Geology and Hydrogeology of the Southern Taos Valley, Taos County, New Mexico By Paul W. Bauer, Peggy S. Johnson and Keith I. Kelson New Mexico Bureau of Mines and Mineral Resources, New Mexico Tech Socorro, New Mexico 87801 Open­file Report 501 January, 1999
GEOLOGY AND HYDROGEOLOGY OF THE SOUTHERN TAOS VALLEY,
TAOS COUNTY, NEW MEXICO
FINAL TECHNICAL REPORT
Paul W. Bauer and Peggy S. Johnson
New Mexico Bureau of Mines and Mineral Resources
New Mexico Tech, Socorro, NM 87801
(505) 835-5106 Fax (505) 835-6333 Email: bauer@nmt.edu, peggy@gis.nmt.edu
Keith I. Kelson
William Lettis & Associates, Inc.
1777 Botelho Drive, Suite 262
Walnut Creek, CA 94596
(510) 256-6070 Fax (510) 256-6076 Email: kelson@lettis.com
January 1999
This project was supported by the New Mexico Office of the State Engineer/Interstate Stream Commission under
Contract No. 97-550-45 (97-214-000764), entered into on May 9, 1997. The views and conclusions contained in this
document are those of the authors, and should not be interpreted as necessarily representing the official policies, either
expressed or implied, of the State of New Mexico.
C ONTENTS
I. INTRODUCTION
A. Significance ...........................................................................................................................4
B. Scope and Objectives ...............................................................................................................4
C. Participants ...........................................................................................................................4
D. Previous Work .......................................................................................................................5
1) Geology ...........................................................................................................................5
2) Hydrology ......................................................................................................................5
3) Concurrent Studies ...........................................................................................................6
II. METHODS
A. Geologic Mapping and Air Photo Analysis ..............................................................................7
B. 1:24,000 Compilation of Existing Geologic, Geophysical, Subsurface & Hydrogeologic Data ......8
C. Collection and Compilation of Domestic Well Data ................................................................8
III. GEOLOGY
A. Structural and Physiographic Elements ..................................................................................9
1. Geologic Setting and History ............................................................................................9
2. Picuris-Pecos Fault System ...............................................................................................9
3. Embudo Fault Zone .........................................................................................................13
4. Cañon Section of the Sangre de Cristo Fault Zone .............................................................14
5. Taos Plateau of the Southern San Luis Basin ...................................................................14
6. Los Cordovas Faults .......................................................................................................15
B. Stratigraphy .......................................................................................................................15
1. Proterozoic .....................................................................................................................15
2. Paleozoic .......................................................................................................................16
3. Tertiary .........................................................................................................................17
4. Quaternary ....................................................................................................................23
IV. HYDROGEOLOGY
A. Mountain Bedrock Aquifers ...................................................................................................24
B. Basin Alluvial Aquifer .........................................................................................................25
C. Water Quality Along the Basin Margin .................................................................................26
D. Geologic Controls on Ground-Water Flow ...............................................................................26
E. Conceptual Model of Mountain Front Recharge .......................................................................27
V. PRELIMINARY BASIN-SCALE GEOLOGIC MODEL
A. Taos Graben .........................................................................................................................29
B. Embudo and Sangre de Cristo Fault Zones ..............................................................................31
C. Servilleta Basalts ................................................................................................................31
D. Picuris-Pecos Fault System ...................................................................................................32
E. Unconfirmed East-Striking Fault System ...............................................................................32
VI. RECOMMENDATIONS AND DATA NEEDS
A. Specific Date Needs in Our Study Area .................................................................................34
B. General Data Needs for the Taos Valley Area .......................................................................35
VII. ACKNOWLEDGMENTS .................................................................................................................37
VIII. REFERENCES C ITED ...................................................................................................................38
IX. APPENDIX 1 -- OTHER S ELECTED R EFERENCES FOR THE T AOS A REA ..................................................42
X. APPENDIX 2 -- TAOS W ATER W ELL I NVENTORY ...............................................................................52
2
List of Tables
Table 1. New 40Ar/39Ar Geochronology from the Taos area ...............................................................19
List of Figures
Figure 1. Generalized tectonic map of northern Rio Grande rift ...........................................................10
Figure 2. Generalized tectonic map of the Taos area ...........................................................................11
Figure 3. Stratigraphic chart of Taos study area ................................................................................19
List of Plates (attachments)
1. Geologic map, cross sections A-A’, B-B’ and E-E’ and potentiometric surface map of the southern Taos
Valley, scale 1:12,000
2. Geologic map and cross sections C-C’ and D-D’ of the Talpa area, scale 1:6,000
3. Tectonic map of the southern Taos Valley, scale 1:24,000
4. Speculative geologic block diagram of the southern Taos Valley.
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I. INTRODUCTION
A. Significance
There have been a variety of published and unpublished interpretations of the hydrogeology in the
Taos area, yet the regional hydrogeologic framework is poorly understood. There are few or no
compilations of basic subsurface data at an area-wide scale, and thus no adequate base of information
for evaluating the hydrogeologic framework of the Taos embayment. Barring the installation of
numerous deep exploration test holes around the Taos Valley and valley margins to provide spatially
distributed subsurface geologic and ground-water data (a necessary, but extraordinarily costly
endeavor), the only alternative approach to development of a sound hydrogeologic understanding of
the basin is through collection and synthesis of various types of surface geologic, geophysical, and
hydrologic data. This study synthesizes new and existing geologic data with all existing and publicly
available geophysical and hydrologic data, and provides a preliminary conceptual hydrogeologic
model for use in making decisions about the exploration and development of ground-water resources in
the Taos area. The model and interpretations presented here are intended to provide direction for the
future collection of new subsurface hydrogeologic data, as well as a geologic framework within which
to interpret future data.
B. Scope and Objectives
The study was designed to collect new surface geologic data in the southern Taos valley, and to
synthesize surface and subsurface geologic and hydrogeologic data into geologic and hydrogeologic
conceptual models. The study area is restricted to the Taos embayment, and specifically includes nonpueblo land in the northwest corner of the Ranchos de Taos quad and the southwest corner of the Taos
quad. We have added small areas of the Taos SW and Los Cordovas quads in order to include relevant
geologic features. Mapping was concentrated on the high piedmont terrain within the embayment.
The primary objectives of the study are:
(1) To develop a geometric model of the surface and subsurface geology of the Taos embayment.
This model will assist in locating areas for drilling exploratory water wells, and in locating critical
areas for hydrologic monitoring.
(2) To better understand the detailed basin-margin hydrogeology in the rapidly developing high
piedmont area between Cañon and Talpa. This understanding will assist planners and developers in
making decisions concerning water supply and water quality, and support geologists and drillers in
developing domestic water supplies.
(3) To investigate the influence of stratigraphy and structure on mountain-front recharge, and
determine what recharge mechanisms are active at various locations.
(4) To evaluate existing data resources and recommend directions of future data collection. Such an
evaluation will assist agencies in making decisions about future water studies in the Taos area.
The following deliverables are included in this report: geologic maps at scales of 1:12,000 and
1:6000, six geologic cross sections and block diagrams, a tectonic/geologic/geophysical map (1:24,000
scale) and preliminary model, a potentiometric surface map (1:12,000 scale) of the basin margin along
the southern Taos embayment, and evaluation of mountain-front recharge mechanisms and routes of
recharge. These data and interpretations are synthesized into a conceptual geologic and hydrogeologic
models. In addition, we provide a discussion of areas for future ground water development and
monitoring.
C. Participants
Principal Investigators:
Dr. Paul W. Bauer, New Mexico Bureau of Mines and Mineral Resources
Senior Geologist, Assistant Director, Manager of Geologic Mapping Program
Project tasks: Geologic mapping, structural geology, geologic model, cross sections, report
4
Peggy S. Johnson, New Mexico Bureau of Mines and Mineral Resources
Hydrogeologist
Project tasks: Hydrologic analysis, hydrogeologic model, report
Principal Contractor:
Keith I. Kelson, William Lettis & Associates, Inc., Walnut Creek, CA
Senior Geologist, expertise in Quaternary geology, neotectonics, seismic hazards
Project tasks: Geologic mapping, air photo interpretations, geologic model, report
Research Assistant:
Annie Kearns, New Mexico Institute of Mining and Technology
Hydrologist
Project tasks: Domestic well database, field checking well locations
Other Contractor:
Paul Drakos and Jay Lazarus, Glorieta Geoscience, Inc., Santa Fe
Consulting geologists with expertise in water supply of Taos area
Project tasks: Provide Taos area subsurface data and hydrogeologic input
Technical assistance:
Mic Heynekamp, New Mexico Bureau of Mines and Mineral Resources
Geologic lab associate
Project tasks: Computer drafting, scanning, report production
D. Previous Work
1. Geology
Dozens of geologic studies have been conducted within the Taos area. Rather than list them here,
we present a comprehensive reference list at the end of this report. Prior to our mapping, no quad-scale,
detailed geologic maps existed for the study area. Instead, there existed regional maps (Miller and
others, 1963; Lipman and Mehnert, 1975; Machette and Personius, 1984; Garrabrant, 1993) and thesis
maps of generally small areas or specialized subjects (Chapin, 1981; Peterson, 1981; Leininger, 1982;
Rehder, 1986; Kelson, 1986; Bauer, 1988). Kelson and others (1997) recently completed a USGS-funded
study of the earthquake potential of the Embudo fault zone. The study included detailed geomorphic
mapping and kinematic analysis of faults on the Picuris piedmont from Pilar to Talpa. Of particular
relevance to the current study, the work by Kelson and others (1997) and Bauer and Kelson (1998)
provides a detailed database on the location and complexity of the Embudo fault zone, which appears
to strongly influence subsurface stratigraphy and hydrogeologic relations along the southern margin of
the Taos embayment. Where appropriate, we incorporated previous map data into our 1:24,000 scale
tectonic map (e.g., locations of Los Cordovas faults from Machette and Personius (1984) and Kelson
(1986)).
2. Hydrology
Several general and reconnaissance level hydrogeologic studies have been conducted in the Taos
Valley over the past 40 years, beginning with work by Winograd (1959) in the Sunshine Valley.
Though located north of our area of interest, Winograd’s descriptions of the various rock formations in
the Sunshine Valley and their water-bearing characteristics are still pertinent today, and provide a
sound conceptual model that is applicable in general terms to the region’s aquifer systems.
Reconnaissance studies were undertaken cooperatively by the U.S. Geological Survey, the New Mexico
State Engineer’s Office, and the U.S. Bureau of Reclamation beginning in the late 1960’s as part of San
Juan-Chama Project studies in the Taos Unit, and are summarized in memoranda and letter reports
(Spiegel and Couse, 1969; Cooper, 1972; Hearne, 1975). These studies produced the first test wells in the
5
area, the first contour map of water levels, and the first aquifer tests evaluating stream-aquifer
interactions. Subsequent studies conducted as part of regional water planning for Taos County and the
City of Taos have focused on regional water quality and availability (Wilson and others, 1978, 1980;
Garrabrant, 1993), and exploratory drilling (Turney, Sayre and Turney; 1982; and Drakos and Lazarus,
1998). Other regional hydrogeologic studies of interest include Hearne and Dewey (1988) and Coons and
Kelly (1984). A water budget developed by Hearne and Dewey quantifies water yield from the Sangre
de Cristo Mountains to the Costilla Plains, and the contribution of mountain front recharge to the basin
aquifer system. A conceptual model of the regional flow system presented by Coons and Kelly infers a
two-layer aquifer system that consists of a deep zone of transient storage extending from the basement
to the bed of the Rio Grande, and a shallow, dynamic zone of saturation influenced by meteoric
processes, stream infiltration, pumping, and discharge to streams. It is important to note that no
persistent and identifiable confining layer between these upper and lower zones has yet been
recognized. Collection of original hydrogeologic data has only occurred during the early San JuanChama studies and recent ground-water exploration projects. NMOSE well records provide the only
other source of subsurface geologic data, water level data, and well productivity data; these are the
data on which this study relies.
3. Concurrent Studies
Several concurrent geology/hydrogeology investigations in the Taos area are pertinent to our
study. The New Mexico Bureau of Mines and Mineral Resources is producing 7.5-minute geologic
quadrangle maps as part of the STATEMAP program (contact Paul Bauer for information). The Taos SW
and Carson quads have been released as Open-File Digital Geologic Maps, and the Ranchos de Taos
quad is being mapped at present. These quads are mapped at a scale of 1:12,000, will be released at
scales of 1:12,000 and 1:24,000, and eventually will be available as digital geologic maps.
The U.S. Bureau of Indian Affairs, in cooperation with the Pueblo of Taos, is involved in a water
supply investigation of Tribal lands on the Taos plateau. This program has included the drilling of
exploration wells and interpretation of the subsurface geology and hydrology. Contact Chris Banet or
Bill White for information.
Glorieta Geoscience, Inc. of Santa Fe continues to work for the Town of Taos as consultant for town
water supply studies. The town has drilled wells and conducted hydrologic investigations of water
quality and availability. Contact Jay Lazarus or Paul Drakos for information.
A doctoral student from the University of Texas at Dallas, David McDonald, is currently finishing
a dissertation on the geometry and kinematics of the northern Picuris-Pecos fault and La Serna fault in
Taos County. He has found complex fault histories, similar to our own findings in the Talpa area.
6
II. METHODS
Our approach for investigating the geology and hydrogeology of the study area consisted of three
general phases:
A. Geologic Mapping and Air Photo Analysis.
Geologic mapping was done by P. Bauer and K. Kelson during a number of field trips in 1997. Bauer
concentrated on mapping basement (Proterozoic, Paleozoic, and Tertiary) rocks and structures, and fault
scarps in Quaternary deposits. Kelson concentrated on air photo interpretation, geologic and
geomorphic mapping of surficial deposits and Tertiary rocks in the Talpa area, and fault scarps in
Quaternary deposits. We completed geologic mapping of bedrock units along the mountainfront/piedmont interface at a scale of 1:12,000. Due to complexities encountered in the Talpa area, we
also produced a 1:6,000 map of that area. Mapping involved a determination of lithology and analysis
of structures such as faults, fracture zones, and folds.
The 1:12,000 scale geologic map includes parts of four 7.5-minute quadrangles: Taos SW, Ranchos de
Taos, Taos, and Los Cordovas (Plate 1). The map represents new field mapping of the mountain front
and piedmont, new air photo interpretation of the lower part of the basin, compilation of some
preexisting mapping by Rehder (1986) in the Pennsylvanian bedrock, and compilation of the locations
of Los Cordovas faults from Kelson (1986) and the 1:250,000 map of Machette and Personius (1984).
A primary goal of this project is to provide a conceptual model of the large-scale geologic structure
of the basin beneath the southern Taos valley. Our approach first is to understand the surficial
structural geology around the edge of the basin by careful mapping, and then to infer the subsurface
basin structure using that knowledge and all other available data sets (e.g., boreholes, geophysics,
surface structure, geomorphology, hydrology). In an area such as Taos, which has experienced at least
four major orogenic episodes, the key to understanding the structure of the basin is based on insights into
the geometry and kinematic history of each of the superimposed tectonic events (Proterozoic, Ancestral
Rocky Mountain, Laramide, and Rio Grande rift).
As part of delineating bedrock units, faults, and basin-fill sediments, we analyzed multiple sets of
photographic imagery. These included color infrared images at a scale of 1:58,000 taken for the USGS
National High-Altitude Program (NHAP) in 1981, black-and-white photography as a scale of
1:45,000 taken for the USGS in 1961, color photography at a scale of 1:24,000 taken for the USDA in
1981, color photography at a scale of 1:15,840 taken for the USFS from 1973-1975, and color
photography at a scale of 1:6000 taken for the Town of Taos in 1995. Our air-photo analysis utilized
primarily the 1:15,840 USFS images because of good coverage and high quality, although each of the
photo sets have a high degree of clarity and provide good information on surficial deposits and faultrelated features. Following our analysis of aerial photography, we conducted detailed mapping of
geologic units and geomorphic features at scales of 1:12,000 and 1:6000. Our mapping included
delineation of Quaternary deposits and surfaces, and of Quaternary faults, fault scarps, and lineaments.
Analysis of faults in all units (Proterozoic to Quaternary) included evaluations of fault geometries and
kinematic data. On bedrock faults, fault striations (slickenlines) were combined with kinematic
indicators such as offset piercing lines or planes, and calcite steps to infer slip directions. In Quaternary
deposits, the limited number of fault exposures precluded collection of many kinematic data. We infer
slip directions based on fault scarp geometry, map pattern of fault strands, and deflected drainages,
following the earlier work by Kelson and others (1997).
Final mylar maps were scanned, drafted onscreen using Freehand on a Macintosh, merged with
base data from ARCINFO in our GIS lab, and plotted as color maps. Individual data sets (e.g., faults,
strikes and dips, breccia zones, etc.) were digitized as separate layers so that maps can then contain any
combination of data sets.
7
B. Compilation of Existing Geologic, Geophysical, Subsurface, and Hydrologic Data.
This approach allowed us to infer subsurface stratigraphy and structure over the region, and then
project important features (such as buried faults and basalt flows) into our study area. Other geologic
maps, geophysical surveys, satellite photos, and deep well locations were scanned and plotted at a
scale of 1:24,000. Essential data were transferred to a master map, which was scanned, drafted on a
Macintosh, and plotted on an HP 3500 color plotter.
C. Collection and Compilation of Domestic Well Data.
Because Quaternary deposits cover bedrock over much of the study area, we evaluated well data
along the bedrock/piedmont interface in order to better understand the shallow basin bedrock
architecture in the area of the Embudo and Sangre de Cristo fault systems, and its control of groundwater flow into the basin. Approximately 250 NMOSE well records from the study area were copied
and reviewed, focusing on those wells located along the mountain front-piedmont margin. Records of
wells that penetrated bedrock, and those that were relatively deep were prioritized for evaluation.
We also used information from six experienced local well drillers in locating wells of particular
interest. Several drillers are very knowledgeable about the various aquifer rock types in the Taos
valley. Well locations were checked in the field by verifying locations with well owners, and recording
UTM coordinates from a Garmin™ GPS II Plus location device. In a few instances when satellite
coverage was inadequate for GPS location, UTM coordinates were obtained from the USGS 7.5-minute
quadrangle maps. Well owners also often provided additional relevant information regarding well
construction, water level, water temperature and water quality. From the field, each well was also
plotted on Town of Taos aerial survey photographs (1:6000 color photographs, flown June 1996) and on
the quadrangle maps. Surface elevations for each well were interpolated from 7.5-minute maps.
Elevations of water levels in wells were determined by subtracting the “depth to water” as reported on
NMOSE well records or by the well owner, from the interpolated land surface elevation. These
potentiometric surface points were then contoured on an overlay to a 1:12,000 scale geologic map (Plate
2). No direct water level measurements were taken due to lack of well access. Well data are
summarized in Appendix 2.
8
III. GEOLOGY
A. Structural and Physiographic Elements
1. Geologic setting and history
The southern Rocky Mountains of northern New Mexico record a complex geologic history, from
Early Proterozoic crustal genesis, to the Paleozoic Ancestral Rocky Mountain orogeny, to the
Cretaceous/Tertiary Laramide orogeny, to Neogene rifting and contemporary extension and
sedimentation. The rocks of the Sangre de Cristo Mountains contain evidence of each of these orogenic
events. For the purposes of this report, we will emphasize the Cenozoic history, although it is likely
that earlier geologic events produced faults and large-scale crustal relations that helped focus
Laramide and rift deformation, and therefore influence the present-day geologic structure of the Taos
area.
The following summary of Cenozoic paleogeography for north-central New Mexico (Ingersoll and
others, 1990) provides a regional framework for our synthesis of the geology of the southern Taos
embayment.
•
•
•
•
•
•
Eocene (58-37 Ma) – A single, large, amagmatic sedimentary basin (El Rito-Galisteo basin) was
bounded by the Laramide Brazos-Sangre de Cristo uplift on the east, and the Nacimiento-GallinaArchuleta uplift on the west.
Early to late Oligocene (37-28 Ma) – Intermediate magmatism with volcaniclastic aprons derived
from the San Juan volcanic field and relict Laramide highs. Picuris Formation accumulates.
Late Oligocene to early Miocene (28-21 Ma) – Bimodal volcanism and associated sedimentation
from Latir volcanic field and Questa caldera. Picuris Formation continues to accumulate.
Early to middle Miocene (21-15 Ma) – Continued erosion of silicic volcanic centers coeval with
initial block faulting of rift. Taos Range begins to form, and Phanerozoic and Proterozoic rocks are
eroded. Tesuque Formation begins to accumulate in incipient San Luis rift basin.
Middle to late Miocene (15-8 Ma) – Rift basins continue to evolve into deep half-grabens with
extensive unroofing of Proterozoic-cored ranges. Complex depositional centers form in basins,
including Chama-El Rito Member, Ojo Caliente Member and Dixon Member of Tesuque Formation in
Taos area. Bimodal volcanism continues. Picuris and Tusas Mountains begin to form.
Late Miocene to present (8-0 Ma) – Concentration of extension in San Luis and Española basins
linked by the Embudo accommodation zone. Major basaltic volcanism in Taos plateau (Servilleta
basalt), with regional uplift, and integration of the Rio Grande drainage. Picuris Mountains
unroofing, with deposition of Chamita Formation along north and west flanks of range.
The Taos area straddles the boundary between Proterozoic and Paleozoic basement rocks of the
Sangre de Cristo and Picuris Mountains and Cenozoic sedimentary and igneous rocks of the southern San
Luis basin (Fig. 1). Three major fault systems intersect within the study area: 1) the Picuris-Pecos fault
system; 2) the Embudo fault zone; and 3) the Sangre de Cristo fault zone (Fig. 2).
2. Picuris-Pecos fault system
The Picuris Range is a Proterozoic-cored, wedge-shaped uplift that projects westward from the
southern Sangre de Cristo Mountains, southwest of Taos. The Picuris-Pecos fault zone and parallel fault
zones to the east (La Serna, Miranda, McGaffey, and Rio Grande del Rancho fault zones [see Plate 1])
are high-angle, north-striking systems that separate the Picuris Mountains block from the main block
of the Sangre de Cristo Mountains. In this report, these fault zones will be collectively referred to as
the Picuris-Pecos fault system. Montgomery (1953) recognized the Picuris-Pecos fault (originally named
the Alamo Canyon tear fault) in the Picuris Mountains. He later mapped its southward continuation in
the southernmost Sangre de Cristo Mountains (Miller et al., 1963). The fault is a north-striking,
vertical to near-vertical structure that appears to consist of a single large-displacement fault over
much of its length. Subsidiary, map-scale, sub-parallel faults exist locally, and in the study area we
have mapped several parallel, large-displacement faults with similar geometries.
9
Figure 1. Generalized tectonic map of the northern Rio Grande rift. From Kelson and others (1997).
10
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68
Picuris-Pecos fault system
11
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Figure 2. Generalized tectonic map of the Taos area.
The Picuris-Pecos fault zone has been traced for more than 60 km, from the northern Picuris
Mountains south of Taos, to I-25 near the village of Cañoncito, east of Santa Fe. From Cañoncito, it can
be traced southward into the Estancia Basin for an additional 24 km, yielding a documented trace of 84
km. The fault probably extends considerably farther southward and northward, yielding a total length
of 160+ km.
Bauer and Ralser (1995) summarized the geologic history of the Picuris-Pecos fault zone as follows:
1) Proterozoic(?), post-1.4 Ga displacement on the Picuris-Pecos fault resulted in some unknown
amount of right slip (perhaps 11 km?) and deflection and attenuation of Proterozoic supracrustal rocks
and older ductile structures;
2) As noted by Sutherland (in Miller et al., 1963), a series of Mississippian and Pennsylvanian west
-up movements on the Picuris-Pecos fault resulted in deposition of sediments along the northern part of
the fault. Although no strike-slip component is documented, some amount was likely;
3) During the Laramide orogeny, at least 26(?) km of right-slip occurred on the Picuris-Pecos fault,
with coeval, subsidiary displacement on north-striking, high-angle faults east and west of the main
fault. The overall geometry of the fault system was a positive flower structure, with dip-slip
displacement dominating some subsidiary faults. Strike-slip, oblique-slip, and dip-slip fault striae all
developed contemporaneously on different fault strands. Perhaps the timing of this contractional
duplex corresponds with the Eocene opening of the transtensional Galisteo Basin along the TijerasCañoncito fault;
4) During the Neogene, rift-related faulting was concentrated in the Santa Fe Range, rather than
the Picuris Mountains, perhaps due to greater extension in the southern Española Basin versus the
northern Española Basin (Chapin and Cather, 1994). Normal faulting may have been distributed over
many reactivated(?), high-angle faults in the southernmost Sangre de Cristo Mountains.
Only the northern end of the Picuris-Pecos fault system has been mapped for this study (Plate
1). All five of the fault zones share some common features. They are all near-vertical, they are wide,
complex structures with many splays, they are mostly located in valleys, and they are all cut by the
Embudo fault system. We suspect that each of the fault zones share similar kinematic histories of
multiple reactivation.
Importantly, for the current study, these faults cut rocks as young as the middle Picuris Formation
(ca. 19 Ma). This means that these faults were active during initial rift formation, and perhaps later as
well, as we suspect that some may also cut the Chama-El Rito member of the Tesuque Formation.
Because the N-S faults are cut by the Embudo fault, they pre-date the Embudo system and,
importantly, must exist in the subsurface north of the Embudo fault. Based on the north-south
orientation of the Taos graben, we suspect that these faults have helped control the geometry of the
Taos graben.
The large N-S faults are located in valleys because the pervasive brittle deformational features
(fractures, fault gouge, fault breccia) are relatively easily weathered and eroded. One implication of
this phenomenon is that in the southern part of the valley, runoff is concentrated along the fault zones.
A second is that the fault zones themselves display hydrologic properties that differ from those of the
unfractured areas.
The most complex, exposed deformational zones are mapped in the Talpa area, where exposures of
the Picuris Formation are cut by both the N-S faults and the Embudo fault zone. For this reason, we
have produced a 1:6000 scale geologic map of the Talpa area (Plate 3). Where Tertiary rocks are
exposed, the map shows numerous faults that are either north- or north-east striking. Most of the N-S
faults in the Tertiary appear to be small structures, with map separations measured on the order of tens
of meters. The main strand of the Miranda fault is not exposed, but can be inferred by the juxtaposition
of Picuris Formation against Proterozoic granite across Arroyo Miranda. Several splays of the Miranda
fault are exposed west and east of the arroyo. In the southwest corner of the 1:6000 map, on hill 7365 ft,
a tectonic sliver of Llano Quemado breccia is bounded by two steeply east-dipping, strike-slip(?) faults.
A system of branching faults (herein named the McGaffey fault) on the bedrock ridge of Cuchilla del
Ojo offsets Proterozoic and Paleozoic rocks, and is probably responsible for the location of Ponce de Leon
thermal springs.
Although Proterozoic rocks underlie all of the study area, they are only exposed in the southwest
corner of the map area. The Picuris-Pecos fault appears to represent a major boundary that has
12
experienced enough slip to juxtapose very different rock packages. West of the fault is the layered
supracrustal Hondo Group, a metasedimentary terrain consisting mostly of quartzite and schist.
Exposures in between the Picuris-Pecos and La Serna faults, and in the Ponce de Leon area east of the
Miranda fault, are of similar, medium-grained, orange weathered granite. Several water wells in the
northern Miranda graben are completed in granite at depths of about 400 ft. All three of these
occurrences are probably of a single granitic terrain, sliced up by the Miranda graben. If so, it follows
that the strike-slip components of net slip on the faults of the Miranda graben are modest with respect
to that of the Picuris-Pecos fault. This granitic terrain probably continues eastward beneath the
Paleozoic section, and exists at depth in the basin to the north. Presumably, the Picuris-Pecos fault also
extends northward into the basin, and must represent a profound subsurface boundary in at least the
Proterozoic and Paleozoic sections. Although the Miranda graben must also extend northward into the
basin (because the graben faults are older than the Embudo fault system), it probably does not represent
such a profound structure in the Proterozoic and Paleozoic sections.
3. Embudo fault zone
The southeastern margin of the San Luis basin is a major Neogene-age fault system, called the
Embudo fault zone, that separates the east-tilted San Luis basin from the west-tilted Picuris block
(Baltz, 1978). Along the northwest flank of the Picuris Mountains, the Embudo fault zone is
distinguished topographically by precipitous cliffs that parallel the Rio Grande and NM-68. The 65km-long Embudo fault zone is a segment of a much larger structural/volcanic trend, the Jemez lineament,
that may have been a zone of crustal weakness since late Precambrian time (Muehlberger, 1979).
Muehlberger (1979) estimated that structural relief across the fault is at least 10,000 ft.
A number of different interpretations of this fault zone have been published (Montgomery, 1953;
Kelley, 1978; Manley, 1978, 1979; Muehlberger, 1979; Aldrich, 1986). Recent work documents
Quaternary northwest-down, left-oblique normal slip along multiple, near-vertical strands on the
northeastern part of the fault (Kelson and others, 1996, 1997; Bauer and Kelson, 1997; Kelson and Bauer,
1998). Our mapping shows that the fault zone is several kilometers wide, and extends from basement
rocks in the Picuris Mountains onto the piedmont north of the range. Aldrich (1986) stated that major
transcurrent movement occurred on the Embudo fault zone during the Pliocene, and has subsequently
slowed. Within our study area, Personius and Machette (1984) and Kelson and others (1997) described
fault scarps on the Embudo trend that could be as young as 10,000 years old.
In the map area, the Embudo fault zone is a complex system of left-oblique, north-down, strike-slip
fault strands that is over two kilometers wide. We have defined the terminus of the Embudo fault at
the Rio Grande del Rancho, where the dominantly strike-slip, east-striking Embudo fault system
swings northward and merges with the dominantly dip-slip Cañon section of the Sangre de Cristo fault.
It is noteworthy that the transition zone from the Embudo fault to the Sangre de Cristo fault is
coincident with the Picuris-Pecos fault system and the Miranda graben.
In Proterozoic bedrock units, the major strands of the Embudo fault are well developed, highangle, brittle deformation zones. Some are many tens of meters wide, typically consisting of central
zones of intense strain (breccia, fault gouge, closely spaced fractures) flanked by wide zones of fractured
rock. The fault strands anastomose, locally around pods of relatively undeformed rock. In
Pennsylvanian sandstones and conglomerates, fault striations (slickenlines) are common, and generally
plunge gently to the west. Fractures typically are open, with only minor carbonate cementation.
Commonly, the massive sandstone and conglomerate beds contain thoroughgoing fractures, whereas the
interlayered shales do not contain fractures. Such a mechanical response to strain of rocks with
different ductilities is common.
A different style of deformation is present in the several places where we found good exposures of
Embudo faults in the Tertiary rocks (Picuris Formation and Chama-El Rito member). In these zones, the
bedrock has been reduced to a clay-rich fault gouge that contains a strong tectonic foliation and clasts
rotated into the foliation plane. Away from the fault plane, these gouge zones grade into altered and
fractured bedrock, and then into relatively unstrained bedrock. In places, these fault zones can be traced
along strike into bedrock faults and into Quaternary scarps. A third style of deformation is seen where
the fault zones cut Quaternary deposits. Typically, the alluvium is laced with thin, anastomosing,
calcite-filled fracture veins. Alteration zones are common, and clasts are rotated into the foliation
13
plane. However, the overall fabric of shearing is substantially less in the Quaternary deposits than in
older units.
The variations in the nature of the Embudo faults in units of different ages are probably due to a
combination of factors. First, there are dramatic differences in the mechanical properties between
consolidated granite/sandstone/conglomerate, semiconsolidated Tertiary siltstone, and unconsolidated
alluvium. Each of these units responds to brittle strain differently. Secondly, the history of faulting
along the Embudo system is one of episodic reactivation (Kelson and others, 1997). Therefore, in
general, we believe that the oldest rocks record the greatest slip; that is, a Pennsylvanian sedimentary
rock has experienced more fault displacement than an overlying Pleistocene alluvial fan.
A variety of physical features help to define fault scarps and photolineaments along the Embudo
fault zone. These include springs and deciduous trees such as willows and cottonwoods.
4. Cañon section of the Sangre de Cristo fault zone
The Sangre de Cristo Mountains are composed primarily of Early Proterozoic supracrustal and
plutonic rocks north of the latitude of Taos Pueblo, and Paleozoic sedimentary strata to the south.
North of Taos, the mountains are bordered on the west by the 160-km-long, north-striking, steeply
west-dipping, normal Sangre de Cristo fault zone, the major rift-bounding structure of the San Luis
basin. Prominent fault scarps exist only along most of the fault zone, which consists of a series of
parallel and subparallel faults with individual strain histories. Nonetheless, the zone shows
significant Pleistocene and Pliocene normal offset (Machette and Personius, 1984; Machette and others,
1998).
Following the usage of Machette and others (1998), the southern section of the fault zone, between
Rio Grande del Rancho and Rio Pueblo de Taos, is called the Cañon section of the Southern Sangre de
Cristo fault. The Cañon section therefore includes the Taos Pueblo fault of Machette and Personius
(1984). The Cañon section shows complex surface expressions and is interpreted as having ruptured
during either early(?) Holocene or latest Pleistocene. The Cañon fault represents the transition between
the Embudo strike-slip fault zone and the Sangre de Cristo normal fault zone (Kelson and others, 1997).
The Cañon section is a complex system of branching faults that define the boundary between the
mountains and the basin. In general, the surface expression of the Cañon section is narrower than the
Embudo fault zone. With the exception of the Rio Fernando area, fault scarps in Quaternary deposits
are mostly confined to the mountain front zone where Quaternary is in contact with Pennsylvanian.
Individual fault planes typically dip steeply west to northwest, with slickenlines plunging
moderately to steeply westward. The transition from strike-slip to dip-slip in the Talpa area is
gradational, with a prevalence of oblique-slip (plus some strike-slip) faults in the bedrock just
southeast of Talpa. The physical characteristics of the bedrock and alluvium faults are similar to
those of the Embudo system.
Several small springs exist along fault splays in the Cañon map area (Plates 1 & 2). The springs
are located in arroyos overlying the footwall block, just upstream (east) from the fault plane.
Presumably, movement of ground water through the sedimentary strata and arroyo alluvium is
attenuated by the Sangre de Cristo fault, and at least partially discharging upgradient of the fault.
We also found two inactive travertine deposits, located on major fault strands, that are probably
associated with extinct springs (Qt on Plate 1).
5. Taos Plateau of the southern San Luis basin
The San Luis basin is one of the major structural elements of the Rio Grande rift. It is
approximately 240 km long, and is bordered by the Sangre de Cristo Mountains on the east, and the
Tusas and San Juan Mountains on the west. The southern part of the basin is a physiographically and
geologically unique terrain known as the Taos Plateau. The plateau is composed mostly of Pliocene
basaltic rocks that were erupted locally, and have only been mildly deformed by rift processes. Basalt
flows dip very gently to the east, at about 6 m/km or 0.4° (Lipman and Mehnert, 1979). The plateau
surface shows only minor dissection, although the Rio Grande and its tributaries are confined to deep
canyons cut through the volcanic rocks. The 1000-ft-deep Rio Grande gorge contains the best exposures of
these flat-lying Tertiary volcanic rocks, as well as the interlayered sands and gravels of the Chamita
14
Formation that represent westward-prograding alluvial fans of the Taos Range. The basalt flows pinch
out eastward and southward towards the edge of the basin.
In the Taos area, the rift is a 30-km-wide, asymmetrical, Basin and Range-style basin with the
major flanking fault system along its eastern border (Sangre de Cristo fault system). The total throw on
the Sangre de Cristo fault system might be as much as 7 or 8 km (Lipman and Mehnert, 1979). Gravity
data indicate that at the latitude of Taos, the basin consists of a very deep N-S graben (maybe >5km
deep; herein called the Taos graben) along the eastern edge of the rift (Cordell, 1978). The west edge of
the graben (herein called the Gorge fault zone) is buried approximately under the Rio Grande (Cordell
and Keller, 1984), resulting in a graben that is less than half the width of the topographic valley. The
structural bench west of the Taos graben rises gently towards the Tusas Mountains, and is cut by
numerous small-displacement normal faults. To the north, the bench becomes an intra-rift horst with
Oligocene volcanic rocks exposed in the middle of the rift at the San Luis Hills of southern Colorado
(Lipman and Mehnert, 1979).
6. Los Cordovas faults
Los Cordovas faults were not mapped for this project, but their southern extent, as mapped by
Kelson (1986), is included in the map area (Plates 1 and 4). Previous workers described a 5-8 km wide
zone of north-striking faults in the Taos plateau (Lambert, 1966; Machette and Personius,1984). Where
separation is greatest, the faults juxtapose piedmont- slope alluvium down to the west against older
Servilleta Formation basalt. Machette and Personius (1984) stated that the fault offset is greater than
the 15-30 m high erosional scarps that now define the surface expression, and that faulting may be as
old as early Pleistocene, but could be as young as middle(?) Pleistocene. Profiles of stream terraces along
the Rio Pueblo de Taos suggest that the faults displace the early(?) to middle Pleistocene piedmont
surface, but not the middle Pleistocene Qt2 terrace (Plate 1; Kelson, 1986; Machette and others, 1998).
B. Stratigraphy
Because the accompanying geologic maps contain descriptions of all lithologic units mapped in the
study area, the following discussion of stratigraphy focuses on stratigraphic relationships, field
relationships, paleogeography, and hydrogeologic significance rather than lithology. This section is a
synthesis of previous work and our current study.
1. Proterozoic
A great variety of Early Proterozoic units is exposed in the Taos Range and Picuris Mountains;
these units are also present in the subsurface of the San Luis basin. In general, the Taos Range contains
large areas of plutonic and gneissic complexes (including greenstones), whereas the northern Picuris
Mountains are composed of metasedimentary rocks (quartzite, schist, phyllite) in fault contact with
granitic rocks to the east. The eastern granitic rock, known as the Miranda granite, is exposed in the
ridges between Arroyo Miranda and Rio Grande del Rancho. For more information on the local
Proterozoic, see references cited in Montgomery (1953, 1963), Bauer (1988, 1993), Bauer and Helper
(1994), Lipman and Reed (1989), and Condie (1980).
Proterozoic crystalline rocks have generally limited primary porosity and permeability. They
store and transmit ground water almost entirely through interconnected fractures, including widely
distributed microfractures and joints, as well as more localized and linear fracture systems associated
with faults. Near-surface local flow systems, intermediate, and deep, regional flow systems can all
play roles in the movement of ground water through crystalline rocks, although local flow systems
operating in the upper 150 ft or so are the most quantitatively significant (Trainer, 1988). The
distribution of Proterozoic units, and specifically the locations and geometries of faults in these rock
units, are very important in understanding how, where, and on what time-scale, ground water is
transmitted from the mountain recharge areas to the Taos Valley.
15
2. Paleozoic
Most of the bedrock exposed in the study area consists of Paleozoic sedimentary strata of
Mississippian and Pennsylvanian age. If earlier Paleozoic rocks ever covered this area of New Mexico,
they were probably removed during Silurian and Early Devonian time (Armstrong and Mamet, 1990). In
early Mississippian time, the Taos region was an area of positive relief on the Proterozoic basement. At
the end of Osagean time, northern New Mexico was covered by shallow marine waters that deposited a
basal sand and carbonates of the Espiritu Santo Formation of the Arroyo Penasco Group. At the end of
the Osagean, erosion of these rocks occurred during regional uplift. A thin section of carbonates of the
Tererro Formation of the Arroyo Penasco Group then accumulated unconformably on the Espiritu Santo
rocks. During latest Mississippian to earliest Pennsylvanian time, all of these sediments were subject to
erosion and karsting, before deposition of the thick Pennsylvanian section. For more information on the
Mississippian strata, see Armstrong and Mamet (1979, 1990)
In the Talpa area, near Ponce de Leon spring, a thin section of the Mississippian (Osagean)
Espiritu Santo Formation of the Arroyo Penasco Group rests unconformably on the Miranda granite. The
Espiritu Santo Formation consists of basal Del Padre Sandstone member of thin basal conglomerate,
quartz sandstone, and minor limestone beds at top, grading upward into the overlying Tererro
Formation. The upper, carbonate-rich part of the Espiritu Santo Formation is mostly absent from the
Ponce de Leon springs area.
Major tectonic activity of the Ancestral Rocky Mountains, probably associated with Ouachita
deformation to the southeast, occurred during the Early to Middle Pennsylvanian. The Taos area was
part of a north-trending trough (the Taos trough or Rowe-Mora basin) located between the nearby
Uncompahgre highland to the west, and the Sierra Grande uplift farther to the east. Thick sequences
of marine, deltaic, and continental sediments were deposited in the Taos area until late Desmoinesian
time when the trough was topped off with arkosic clastic sediments of the Sangre de Cristo Formation
during a second orogenic pulse. The trough opened southward across the Pecos carbonate shelf, and so
the clastic-dominated Early to Middle Pennsylvanian rocks of the Taos area grade southward into the
cyclic carbonate strata of the Pecos area.
Pennsylvanian stratigraphic nomenclature is somewhat complicated by the concurrent use of two
sets of names for the same rocks. Read and Wood (1947) named these early to mid-Pennsylvanian,
marine sedimentary rocks the Magdalena Group, with a lower Sandia Formation and an upper Madera
Formation. After a detailed study of these rocks between Taos and Pecos, Sutherland (1963) rejected
these names, and defined three new formations. The Flechado and La Posada Formations represent the
northern (deeper marine) and southern (carbonate shelf) equivalents of the Sandia Formation and the
lower part of the Madera Formation (the so-called gray limestone member). The overlying Alamitos
Formation represents the upper part of the Madera Formation (the so-called arkosic limestone
member), and interfingers with the overlying Sangre de Cristo Formation. Although most workers have
used Sutherland’s names, Soegaard and Caldwell (1990) chose to use the original nomenclature. In this
report, we will use Sutherland’s names.
Within the study area, the Pennsylvanian strata exposed from the top of the Mississippian
section on Cuchilla del Ojo near Ponce de Leon spring eastward into the Sangre de Cristo Mountains is
probably entirely Flechado Formation, although a series of large, north-striking faults have repeated
and/or deleted parts of the section. The exposures consist mostly of olive, brown, and dark gray shales
and siltstones, and low-feldspar sandstones and conglomerates. Limestone is a very minor component of
the section. The shales and siltstones are typically poorly exposed, whereas the sandstones are
moderately to very well exposed, and the conglomerates and limestones are ridge- and cliff-formers.
Casey and Scott (1979) measured sections near Talpa, and concluded that the rocks represent a series of
clastic wedges that record an eastward and southeastward progradation of coarse fan-delta lobes in the
Taos trough. The fan deltas contain complex interrelationships of thin, laterally discontinuous facies
that make traditional mapping of rock-stratigraphic units problematic. The only units that we
mapped in detail in this section were limestone beds and thick, ridge-forming sandstone horizons. Both
rock types were useful for helping to delineate faults with large separations. For more information on
Pennsylvanian sedimentary strata, see Sutherland (1963), Casey and Scott (1979), Casey (1980), Kues
(1984), and Soegaard and Caldwell (1990).
16
Although only a small portion of the study area contains Paleozoic rocks at the surface, it is likely
that much of the area is underlain at depth by these rocks. Thus, many geologic characteristics of these
rocks are important for understanding the subsurface hydrogeology of the area. For example, the
Mississippian section near Ponce de Leon spring contains paleokarst features. Similar Mississippian
rocks presumably exist at depth in the basin, and therefore can be considered a possible zone of
increased, solution-enhanced permeability. In well-indurated units, fractures and faults play a similar
role in transmitting ground water as described above with Proterozoic crystalline rocks. In layered
sedimentary strata, faults can also create barriers to ground-water flow either by impermeable
segments of the fault itself, or by interrupting a flow path with a less permeable unit. This combination
of faulting and layered stratigraphy typically produces compartmentalized aquifer systems with
preferential flow paths through the more permeable stratigraphic units.
In 1996, the Town of Taos drilled an exploration well in the town yard, behind the Wal-Mart on
Paseo del Norte Sur. At 720 ft, Pennsylvanian sedimentary rocks were encountered. Before the well was
abandoned at 1020 ft, 300 ft of limestone, shale, and sandstone had been penetrated. Prior to this well,
no control points existed for the location of the Paleozoic section in the southern Taos valley. The well
is located nearly two miles from the nearest surface exposures of Pennsylvanian, near Cañon. Clearly,
Paleozoic strata exist in the subsurface of the basin, and in places, at shallow depths. The fact that
fossiliferous limestone was a prominent lithology in the well cuttings, suggests that the rocks
encountered at depth might come from higher in the Pennsylvanian section, perhaps in the upper
Flechado Formation or the Alamitos Formation. If so, then Proterozoic basement could lie as much as
several thousand feet deeper, because the Alamitos Formation can be over 4000 ft thick, and the
Alamitos can be 2500 ft thick in the Taos trough.
The thick section of Pennsylvanian strata of the Taos trough thins westward against the former
Uncompahgre uplift, but the rate of thinning, and the location of its termination are unknown (Baltz,
1978). Because of its existence in the Town Yard well, our cross sections (see section A-A') show a
reasonably thick Pennsylvanian section that thins westward in the Taos graben.
3. Tertiary
Ingersoll and others (1990) wrote “Cenozoic stratigraphic nomenclature of the study area is
extraordinarily complex......due to interfingering of distantly and locally derived nonmarine units of
widely differing provenance and lithology. There are many examples of published geologic maps with
different stratigraphic units mapped in the same places by different geologists. This confusion of
nomenclature results from both the complex stratigraphy and poor exposure of some slightly
consolidated lithologies.” We agree. However, we also believe that the Tertiary units of the study
area are consistent with previous stratigraphic frameworks. Within the area, investigations of
Cenozoic geology have been conducted by Manley (1976), Muehlberger (1979), Steinpress (1980),
Leininger (1982), Dungan et al. (1984), Aldrich and Dethier (1990), and Ingersoll and others (1990).
Picuris Formation. The oldest Cenozoic unit in the study area is the Picuris Formation; a local
package of mostly volcaniclastic sedimentary rocks that represents pre-rift and early-rift activity. It
is thought that the early shallow rift basins of northern New Mexico were initially infilled by a
combination of volcanic eruptions and volcaniclastic alluvial fans with sources in the San Juan volcanic
field to the north (Baltz, 1978). The Picuris Formation probably represents such a deposit (Manley,
1984).
The only previous study of the Picuris Formation divided it into three members; the lower member,
the Llano Quemado breccia member, and the upper member (Rehder, 1986). These subdivisions were
made by examining and then correlating 11 scattered exposures. This work was a major contribution to
understanding this important unit, but we are uncertain of the validity of some the interpretations due
mainly to new isotopic ages and the remarkably extensive faulting present in the study area. Although
the Llano Quemado breccia is an excellent marker bed, in the Talpa area it crops out as a scattering of
fault-bounded exposures (Plate 1) that complicate straightforward stratigraphic reconstructions.
Nonetheless, we have retained Rehder’s stratigraphy, with the addition of several modifications
proposed by Ingersoll and others (1990). These latter workers included the Llano Quemado breccia
within the lower member of the formation, renamed Rehder’s “upper Picuris Formation” as the “middle
Picuris Formation”, and included the “upper Picuris Formation” with the lower part of the Chama-El
17
Rito Member of the Tesuque Formation. We will therefore use Ingersoll and others (1990) nomenclature
(Fig. 3) with our new chronostratigraphy.
Within our study area, the lower member of the Picuris Formation appears to consist of a basal
boulder and cobble conglomerate and conglomeratic sandstone interbedded with thinly bedded
sandstones. The boulder unit is distinctive, composed of well rounded, poorly sorted, mostly clast
supported, Proterozoic quartzite clasts, with minor altered clasts of intermediate Tertiary volcanic
rocks and Paleozoic sedimentary rocks. The boulder unit grades (fines) upward to less indurated pebble
conglomerate and conglomeratic sandstone, and variegated green, red, and white siltstone and mudrock.
Local layers of primary(?) white to gray to yellow to brown air-fall ash are well sorted and contain
sanidine and biotite crystals. This member was interpreted as a sequence of debris flow and alluvial fan
deposits derived from the Sangre de Cristo Mountains and Latir volcanic field to the north and
northeast (Rehder, 1986). However, as noted below, the deposit (34-27 Ma) cannot be older than the
source (26 Ma), and therefore, the volcanic component of the unit was probably derived from the older
San Juan volcanic field to the north and northwest. Alternatively, the source could be a buried or
eroded, unrecognized, older volcanic unit from the Latir field.
Llano Quemado breccia (perhaps part of lower member) is a light gray to red, monolithologic
volcanic breccia of distinctive extremely angular, poorly sorted, light-gray, recrystallized rhyolite
clasts in a generally reddish matrix. Rhyolite clasts contain phenocrysts of biotite, sanidine, and
quartz. The rock is highly indurated and crops out as a ridge-former. The breccia was interpreted as a
series of flows from a now buried, nearby rhyolite vent (Rehder, 1986). However, excellent exposures in
Arroyo Miranda display layering and sedimentary structures such as cross bedding that indicate that
at least parts of the unit are reworked volcaniclastic sediments.
The middle member of the Picuris Formation (Rehder’s upper member) is a gray to pinkish gray,
immature, pumice-rich, ashy, polylithologic, conglomeratic sandstone. It consists mainly of sandstones
with gravel-sized clasts of pumice and silicic volcanic rocks (mostly 25.7 Ma Amalia Tuff), and minor
Precambrian quartzite and intermediate composition volcanic rocks (including the 26.0 Ma Latir Peak
quartz latite). Most of gravel-sized fraction is pumice, with some clasts up to 25cm in diameter. Most
clasts are rounded to well rounded. Some cobble-rich conglomerates are interlayered with easily
eroded, weakly cemented pebble conglomerates. Paleoflow measurements indicate a source to the north,
and Rehder (1986) interpreted the unit as an alluvial fan deposit derived from the Latir volcanic field
at around 26 Ma (Rehder, 1986). We agree, and would add that a new basalt clast date of 18.59+/-0.70
Ma from the middle member (see below) indicates that at least part of the section accumulated much
later. Based on our mapping along the northern Picuris Mountains piedmont, where the tilted,
pedimented Tertiary rocks are locally exposed beneath Quaternary fans, we prefer to interpret a
continuous section of Picuris Formation to Tesuque Formation, perhaps punctuated locally by
unconformities.
The NMBMMR Geochronology Lab recently provided us with several new 40Ar/39Ar isotopic ages
for the Picuris Formation (Table 1), which further refine the stratigraphy (Table 1). For the current
study, the important geochronological findings are summarized below:
• A white ash that crops out near Talpa, and is interbedded with clastic sediments of the lower
Picuris Formation, yielded an age of 34.64±0.16 Ma. This date pushes back the age of the Picuris
Formation to early Oligocene, and, if our stratigraphy is correct, it means that the oldest exposed
part of the Picuris Formation (Tplc, the basal quartzite boulder conglomerate near Talpa) is older
still.
• A rhyolite clast from the Llano Quemado breccia yielded a plateau age of 28.35±0.11 Ma. This
probably represents the eruptive age of a rhyolite dome that was later eroded or buried. The
breccia is therefore older than any rock known from the Latir volcanic field, the oldest of which is
a 26.0 Ma quartz latite that was interpreted as a pre-caldera feeder (Czamanski and others, 1990).
Because we believe that the breccia is actually a sedimentary rock, the clast age is therefore a
maximum age for the unit.
• A poorly indurated, white ash from south of hill 7365ft was dated at 27.93±0.08 Ma, confirming that
parts of the lower Picuris Formation are approximately time equivalent to the Llano Quemado
breccia.
18
• Figure 3. Composite stratigraphic chart for the Taos area.
19
• Additional new control on the age of the Picuris Formation comes from a vesicular basalt clast from
the upper Picuris Formation on the west side of Arroyo Miranda, collected by D. McDonald of the
University of Texas at Dallas. The date of 18.59±0.70 Ma is a minimum age due to some argon loss,
but nonetheless indicates that Picuris Formation deposition continued into the Miocene, and
possibly overlaps in time with the Chama-El Rito Member (18-14 Ma in the Dixon area, according
to Steinpress, 1981).
Table 1.
Sample # A r / A r
age
RdT-8
Car-7
RdT-4
RdT-5
PB-3
New 40Ar/39Ar Geochronology from the Taos Area
Unit
Name
34.64 Picuris Fm
+/- 0.16
lower
34.5
+/- 1.2
Picuris
Fm?
28.35 Picuris Fm,
+/- 0.11
Llano
Quemado
breccia
27.93 Picuris Fm,
+/- 0.08 upper?
27.5
+/- 2.0
Rock
Type
ash
A n a l y z e d Lab #
15
sanidine
crystals
ASH23
Quad
UTM N
Ranchos
de Taos
4020550
ash
17 sanidine
crystals
Carson
4013600
rhyolite
clast
15 sanidine
crystals
Ranchos
de Taos
4019200
ash
15 sanidine
crystals
Ranchos
de Taos
4019200
UTM E D e s c r i p t i o n
446350 10-cm white ash
between lower red and
greenish-gray
claystones, W of Pete
Tafoya's house. Good
eruptive age. Coarsegrained, so near source.
431070 white ash near Pilar.
Sanidines altered. Finegrained. Confidence
uncertain
444900 white rhyolite clast in
red groundmass. Good
eruptive age.
444900 white ash, poorly
indurated, just below
RdT-4. Good eruptive
age.
Tv cobble in float in
Tesuque(?) Fm.
Tesuque
Fm?
volcanic single flake biotite Taos SW
cobble
PB-5
27.29
Tesuque
+/- 0.15
Fm?
volcanic single flake biotite Taos SW
cobble
Tv cobble in float in
Tesuque(?) Fm.
PB-2
25.16
Tesuque
+/- 0.10
Fm?
volcanic
cobble
15 sanidine
crystals
Taos SW
Tv cobble in float in
Tesuque(?) Fm.
RdT-13
18.59 Picuris Fm,
+/- 0.70
upper
basalt
clast
ground- mass
Taos SW
4016380
ground- mass
Tres Ritos
4004600
Taos SW
4021630
TresRitos- 5.44 +/1c
0.20
basalt
basalt
TaosSW-1 1.27 +/0.02
Qf2
ash
15
sanidine
crystals
ASH14
20
443800 David McDonald
vesicular basalt sample
from upper Picuris Fm
layered white tuff.
Disturbed spectrum, so
minimum date.
444300 mildly vesicular basalt
outcrop from S or US
Hill. Some alteration?
438400 white ash, cross
bedded, coarse & fine
layers, reworked Plinian.
Roadcut on NM-64, .65
mi W of Steakout Rd.
Surface exposures of the Picuris Formation exist only west of the Rio Grande del Rancho (Plates 1
& 3). It is not known for sure whether the Picuris Formation exists in the subsurface of the basin east of
the Rio Grande del Rancho, but the numerous well records reviewed in this study do not support its
presence there. The presence or absence of the Picuris Formation is important to the hydrogeologic work,
as the Picuris Formation and the Santa Fe Group have dissimilar hydraulic properties. Whereas the
basal conglomeratic and volcanic breccia units have the potential to store and transmit ample amounts
of ground water, the overlying siltstone, mudstone, and middle, immature, ashy sandstone are expected
to exhibit low to very low hydraulic conductivities.
In summary, in the map area, the stratigraphy generally agrees with that of Rehder (1986). The
base of the Picuris Formation is exposed just west of the mouth of the Rio Grande del Rancho, where a
quartz-cobble conglomerate rests unconformably on Pennsylvanian strata. The conglomerate fines
upward to a sequence of quartz-pebble conglomerates, sandstones, and siltstones. This part of the section
is extensively faulted, by north- and northeast-striking faults. Well data indicate that the basal
boulder conglomerate has west-down vertical separation across a series of faults within the Embudo
fault zone. The middle volcaniclastic member of the Picuris Formation crops out in the western map
area, generally west of Arroyo Miranda. It is extensively faulted in both the Miranda and La Serna
fault zones.
Santa Fe Group. Although the Santa Fe Group is not exposed in the study area, it certainly exists
in the subsurface of the northern part of the map area. The exact nature of the Santa Fe Group is
unknown, although borehole data indicate that relatively thin Quaternary deposits are underlain by
thick Tertiary sand and gravel in the basin. Geologists who have examined cuttings from deep
exploration boreholes in the Taos area have picked out the Chamita-Ojo Caliente contact, and the Ojo
Caliente-Chama-El Rito contact locally in the subsurface. At present, due to the heterogeneity of the
Santa Fe Group, and the paucity of petrographic analysis of the cuttings, we believe that within the
map area the data are insufficient for constructing isopach or structure contour maps on any of the Santa
Fe Group sedimentary subdivisions described below.
Servilleta Formation basalts exist in the subsurface in the northern part of the map area. We have
used available well data to constrain the extent of Servilleta basalt in the subsurface, and are also
attempting to fingerprint basalt flows encountered in deep boreholes using geochemistry and
geochronology.
As rift extension progressed, and normal faulting along the Sangre de Cristo fault offset the Taos
Range from the San Luis basin, the volcaniclastic and Precambrian-clast dominated Santa Fe Group
began to accumulate in the broad rift basin. The Tesuque Formation (Miocene to Pliocene) of the Santa
Fe Group, was originally defined near Santa Fe by Baldwin (1956). In the Picuris Range area, Miller et
al. (1963) described this sequence as buff-colored, poorly sorted, weakly consolidated, sand, silt, gravel,
volcanic ash, clay, and breccia that ranges in thickness from 500 to 3500(?) ft (150 to 1065(?) m). Much of
this unit was derived locally from Paleozoic and Precambrian rocks, and along the flanks of the Picuris
Mountains sits unconformably on Precambrian basement. Rock types typically vary considerably along
strike.
In the Taos/Pilar area, the oldest Tesuque Formation unit is the Chama-El Rito Member, composed
predominantly of volcanic-rich, non-fossiliferous sandstone and conglomerate, with minor mudrock
interbeds. Conglomerates are generally purplish to gray due to the abundance of pebble-size,
intermediate composition, Tertiary volcanic clasts. Sandstones are pinkish-gray to buff, poorly to
moderately sorted, with highly variable grain size. Sandstones are transitional between arkoses and
volcanic arenites. White beds of calcareous, pyroclastic volcanic ash, less than 2 m thick, are found
locally. Fluvial and alluvial sedimentary structures are common. The Chama-El Rito Member, thought
to be 18-14 Ma, represents braided stream deposits on a distal alluvial fan derived from a volcanic
terrain to the northeast (Steinpress, 1980). The Chama-El Rito Member is locally exposed along the
Picuris Mountains piedmont, and we have inferred it in the subsurface in the study area. Thickness in
the Dixon area was estimated to be 480 m (1570 ft) (Steinpress, 1980).
The Chama-El Rito Member is conformably below, and interfingers with, the Ojo Caliente
Sandstone Member of the Tesuque Formation west of the study area, along Rito Cieneguilla, near Pilar
(Leininger, 1982; Kelson and Bauer, 1998). The Ojo Caliente is a buff to white, well-sorted eolian
21
sandstone, consisting mostly of fine sand. Tabular crossbeds are common, with some sets over 4 m in
height. Transport was from southwest to northeast, approximately 13-12 Ma (Steinpress, 1980). The Ojo
Caliente is not exposed in the study area, but probably exists in the subsurface. If so, its lateral extent
and thickness are generally unknown, but estimated to range from 30 to 250 m (100 to 820 ft). Based on
lithologic interpretations from well cuttings and downhole geophysics, the Town of Taos exploration
well along the Rio Pueblo in the northwestern corner of the study area (Well RP-2000, TW-112)
penetrated what appears to be a 650-ft interval of primarily Ojo Caliente sands (Drakos and Lazarus,
1998).
During rifting in late Miocene time, high-angle faulting produced deep, narrow, fault-bounded
basins that filled with great thicknesses of clastic sediments and volcanic rocks. In the Taos/Pilar
area, the clastic sediments are named the Chamita Formation of the Tesuque Formation (the name
Cieneguilla member has been abandoned), and the volcanic unit is named the Servilleta Formation. To
the north of Taos, some workers have used an informal name, the Lama Formation, to describe the
Tertiary clastic sediments that lie above the upper Servilleta basalt. In light of the fact that alluvial
sedimentation was continuous before, during, and after basalt eruptions, and that the eruptions were
essentially instantaneous compared to the time involved in sedimentation, we will use the Chamita
Formation designation for all of these Pliocene sediments.
The Chamita Formation (Miocene and Pliocene) is well exposed in the Pilar area, where it ranges
from a lower section of buff-colored, moderate to poorly sorted sands with clasts of intermediate
volcanic rock, quartzite, and other metamorphic rocks, to a middle section with fewer volcanic clasts
and more metamorphic clasts, to an upper section that is devoid of volcanic clasts. Overall, the unit
coarsens upwards. On Pilar Mesa, dips decrease from 30°NW at the base to horizontal at the top, with
an internal angular unconformity of about 15° near the top of the exposure. Its contact with the Ojo
Caliente Sandstone is interfingering. The upper part of the unit represents an axial drainage off the
uplifted Picuris Mountains block at about 8-5 Ma (Ingersoll and others, 1990). Thickness of the Chamita
Formation is highly variable and difficult to estimate at any given location. It is also extremely
difficult to distinguish the Chamita Formation from overlying Quaternary alluvial deposits, a fact
which poses a problem when interpreting lithologies and formational contacts based solely on well
cuttings. Thickness has been estimated to range from 100 to 230 m (330 to 750 ft) in the Pilar area
(Steinpress, 1980). However, in the Town of Taos exploration well along the Rio Pueblo (Well RP-2000,
TW-112), thickness of the Chamita Formation below the lower Servilleta basalt was estimated to be
930 ft (Drakos and Lazarus, 1998).
Nearly flat-lying basalts of the Pliocene Servilleta Formation cap the Taos plateau over much of
the southern San Luis basin. The basalt is a dark-gray, diktytaxitic olivine tholeiite that erupted as
thin, fluid, widespread, pahoehoe basalt flows. Individual flows, which are up to 12 m thick, are
grouped into packages of from one to ten flows, and separated by 0.3- to 4.5-m-thick sedimentary
intervals (Leininger, 1982). Dungan and others (1984) identified three basalt groups at the Gorge
Bridge, a classification that has been adopted by most workers. A lower basalt package consists of two
sets of flows totaling 51 m, that locally are separated by up to 4 m of Chamita Formation sediments. A
middle basalt of 36 m is separated by a relatively thick, 30-m sedimentary interval from an upper
basalt sequence of 30 m. However, the relative thicknesses of the various basalt packages, individual
flows, and intervening sediments are quite variable. Limited exposure of the basal basalt in the gorge
suggests that flows erupted onto a nearly flat erosional surface of the Chamita Formation. Five central
vents to the north are the sources of the flows (Lipman and Mehnert, 1979), which dip gently, thin, and
pinch out to the east and southeast. A recent study of isotopic ages of the volcanic rocks of the Taos
plateau has shown a range in ages of the Servilleta Formation basalts from 4.81±0.04 to 3.12±0.13 Ma at
the Gorge Bridge, and from 4.33±0.02 to 2.93±0.14 Ma at the Dunn Bridge (Appelt, 1998).
The Servilleta basalts have been encountered in many test and exploration wells near Taos, and
the eastward lateral extent of at least the uppermost basalt flows can be approximated in map view
(Plate 1). The ability of the basalt to transmit water depends upon the extent of fracturing and/or the
presence of cooling joints, characteristics that vary amongst individual flows as well as spatially
within a single flow. Where the lavas are not fractured or jointed, they are relatively impermeable.
The limited data currently available indicate that generally the basalts do transmit water, sometimes
in large quantities, although individual flows behave locally as confining units (Winograd, 1959).
22
The intervening Chamita Formation sediments also vary significantly in their lithologic and
hydrologic characteristics. A thick sequence of sandy, gravel fluvial sediments separating the upper
and middle basalts, termed the Agua Azul aquifer (Drakos and Lazarus, 1998), is reported to have a
transmissivity ranging from 280 to 700 ft2/day (hydraulic conductivity of 8 to 26 ft/d) at the RP-2000
well (TW-112). In the Karavas 2 exploration well, the intervening fluvial sediments are dominantly
sand, with an expected conductivity in the range 0.1 to 1 ft/d. In general, lithologic characteristics of
interbedded Chamita Formation sediments range from lacustrine clays to axial fluvial sands and
gravels. These sediments would be expected to exhibit hydraulic conductivities ranging from 100 to 10-4
ft/d. Owing to the spatially variable hydrogeologic characteristics of the basalts and intervening
sediments, it is extremely difficult to characterize their different water-bearing capacities on a basinwide or even regional scale.
4. Quaternary
Quaternary deposits in the Taos area generally are unconsolidated, make up the shallow aquifers,
and provide areas for ground water recharge. The study area contains a variety of coalescent alluvialfans, stream channel, and terrace deposits that range in age from early(?) Pleistocene to Holocene. In
the western part of the study area, surficial deposits (high alluvial fans?) derived from the Picuris
Mountains interfinger with alluvial terrace deposits along Rio Grande del Rancho near Talpa. The
alluvial fans grade to the highest Servilleta Formation basalt along the southern rim of the Rio Pueblo
de Taos gorge (Kelson, 1986). In the central and northern parts of the study area, near-surface
Quaternary units consist of coarse-grained fluvial sediments deposited by major streams, and coarse- to
fine-grained alluvial-fan sediments derived from smaller, mountain-front drainages. The sandy area
contains fluvial and alluvial-fan deposits that range in age from early Pleistocene (1.6 to 0.7 Ma) to
recent.
Fluvial sediments are present primarily along the Rio Grande del Rancho, Rio Chiquito, Rio
Pueblo de Taos, and Rio Fernando valleys. These poorly sorted sands and gravels contain subrounded
clasts of quartzite, slate, sandstone, schist, and granite, and are laterally continuous in a down-valley
direction (Kelson, 1986). Soils developed on these deposits associated with older, higher stream
terraces (i.e., the terrace beneath the village of Llano Quemado) contain well-developed (stage III to
IV) calcic horizons that may impede near-surface infiltration of meteoric water. Younger terraces are
associated with lesser amounts of soil development (stage I to II calcic horizons; Kelson, 1986). Because
these deposits lack substantial soil development and are located near active watercourses, they allow
substantial amounts of surface water to infiltrate into the ground water system. Continuous zones of
saturation 15 to 40 ft thick have been identified along the major water courses in the valley (Spiegel
and Couse, 1969), and have been shown to be in direct hydraulic communication with the underlying
Quaternary alluvial deposits or Santa Fe Group sediments.
Alluvial-fan deposits in the central and northern parts of the study area are derived mostly from
smaller mountain-front drainages developed in Pennsylvanian sandstone and shale. In general, these
deposits are coarse-grained sands and gravels near the mountain front, and are finer-grained with
distance to the north or west. The alluvial-fan deposits likely are laterally discontinuous and
moderately heterogeneous. Older fan deposits are associated with well-developed soils (stage III to IV
calcic soils), whereas younger deposits contain moderately developed soils (stage I to II calcic horizons)
or lesser-developed soils. The younger fans in many places bury older fan deposits, such that subsurface
conditions may vary considerably across the mountain-front piedmont. Because of this variability,
ground-water flow paths may be complex along the Sangre de Cristo mountain front.
North of Rio Pueblo de Taos, in the northwestern corner of the study area, the Servilleta basalt is
overlain unconformably by fine-grained deposits that likely are: 1) the distal parts of older alluvial
fans shed from the Sangre de Cristo Mountains; and/or 2) derived from the ancestral Rio Grande
(Kelson, 1986). These deposits are poorly exposed, but based on stratigraphic position, are probably
middle Pleistocene in age and may have well-developed soils beneath stable ground surfaces.
23
IV. HYDROGEOLOGY
Given the spatially complex distribution of coalescing Quaternary and Tertiary alluvial and
volcanic units along and adjacent to the basin margin, and the combined influence of complex faulting,
ground-water flow paths along the southern edge of the Taos Valley are also expected to be quite
complex. Evaluating ground-water flow at the basin margin is an important step in determining what
recharge mechanisms are active along the margin and at what geographic locations. These data and
interpretations are important factors in supporting more quantitative efforts to model ground-water
flow in the basin. Piezometric surface maps, when interpreted in a geologic framework, are important
hydrogeologic tools, and help identify and evaluate: (1) ground-water flow paths; (2) geologic controls
on ground-water flow (structural, stratigraphic, or depositional); and (3) areas receiving or lacking
active recharge. A piezometric surface map was developed for the margin of the southern Taos Valley
extending from Talpa northeast to Cañon, based on the domestic well inventory presented in Appendix
2. Wells used in creating the map are completed in Pennsylvanian bedrock, Tertiary Picuris Formation,
and Tertiary/Quaternary basin fill alluvium. The piezometric contours, developed separately for
mountain bedrock and alluvial basin aquifers, are shown on a 1:12,000 geologic base map on Plate 2. A
discussion of the piezometric map and basic interpretations are presented below.
A. Mountain Bedrock Aquifers
The piezometric surface map for the mountain bedrock aquifer(s), shown in red contours on Plate 2,
is based on 39 wells completed in Pennsylvanian shale, sandstone, and limestone, as well as Tertiary
Picuris Formation. The wells range from 118 to 500 ft in depth, and are found from the foothills south of
the Embudo fault zone northward to the farthest basinward expression of the fault zone.
Approximately half of these wells exhibit artesian or semi-artesian conditions.
Hydraulic gradient in the bedrock aquifers generally follows topography, sloping downward from
the mountains toward the basin. Ground-water flow direction is NW at a moderate to high gradient of
about 0.1 to 0.7. The hydraulic gradient along the mountain front between the Rio Chiquito and the Rio
Fernando is relatively uniform, of moderate grade (0.25 to 0.50), and does not appear to vary
significantly with well depth. The most dramatic gradient anomaly occurs along the Rio Grande del
Rancho, between Arroyo Miranda and Rio Chiquito where the hydraulic gradient flattens to
approximately 0.1. This lower gradient indicates a zone of relatively high hydraulic conductivity and
increased ground-water flow in the region bounded by the Miranda and Rio Grande del Rancho faults.
This increase in ground-water flow is an expected response to pervasive fault-related fracturing in the
well-indurated Pennsylvanian sandstones and limestones and crystalline Proterozoic granite. Geologic
mapping noted that fractures near these faults were ubiquitous and open, with only minor carbonate
cement present in fractures. Hydrostatic head conditions also seem to prevail in this region, based on
apparently uniform hydraulic heads over the upper 360 ft of aquifer in wells TW-1, TW-93, and TW110.
The Miranda fault exerts significant control on ground-water flow at the mouth of Miranda
Canyon, probably due both to (fault related) increased hydraulic conductivity in the Proterozoic
granite, and to relatively low conductivity in the abutting portion of the Tertiary Picuris Formation.
Piezometric contours are deflected parallel to the fault and indicate that ground-water flows WNW
through the Tertiary Picuris Formation at a relatively steep gradient of 0.7. Evidence also exists for a
vertical component of flow near the fault, based on a vertically upward gradient of approximately 0.15
between wells TW-26 and TW-73. Further, the discharge of thermal water at Ponce de Leon springs is
indicative of both very deep, regional circulation of ground water as well as a vertically upward
gradient near Miranda and Cuchilla de Ojo faults. The Picuris Formation exerts significant control on
ground-water flow in the Talpa area. Variegated siltstones and claystones present in the lower Picuris
typically form a relatively impermeable, confining layer over the basal quartz conglomerate, which
can produce significant quantities of water (e.g. well TW-67). In parts of the Rio Grande del Rancho
floodplain, some wells go down over 400 ft to get good production from the basal Picuris Formation.
24
B. Basin Alluvial Aquifer
The piezometric surface map for the basin alluvial aquifer, shown in blue contours on Plate 2, is
constructed from data in 38 wells completed in Quaternary and Tertiary alluvial material. With very
few exceptions, no distinction is made regarding formation or unit of completion. The wells on which
piezometric contours are based range from 82 to 1020 ft in depth, but most are less than 440 ft. The wells
are primarily located along the basin margin in the Talpa, Weimer Road, and Cañon areas, with a few
wells located outboard from the margin toward the so-called basalt line. Slightly less than half of
these wells exhibit artesian or semi-artesian conditions.
The first notable feature of basin-margin water levels is that hydraulic head appears to vary
significantly with depth. Based on these limited data, it can generally be noted that wells with midscreen elevations less than 6,800 ft (wells TW-6, TW-71, TW-83, TW-100, TW-104, and TW-105) exhibit
lower hydraulic heads than nearby wells completed over 6,800 ft, indicating a vertically downward
gradient in the shallow margin aquifer. This head drop has no readily identifiable lithologic or
geologic control, but is observed along the margin between Talpa and Weimer Road, and in the basin
east of Ranchos de Taos. There are insufficient data to evaluate the vertical gradient near Cañon. The
downward flow component is, however, consistent with a regional pattern of active ground-water
recharge beginning at the basin margin and extending basinward for an undefined distance. Only those
wells with mid-screen elevations greater than 6800 ft were utilized in constructing the piezometric
contours for the alluvial aquifer depicted on Plate 2.
The second notable feature reflected by the piezometric map is the existence of a slightly reversed
gradient at the basin margin, that is necessarily accompanied by a piezometric high midway between
the Embudo fault zone and the basalt line. The piezometric high, or water table mound, is defined by
water levels in wells TW-94, TW-5, and TW-114. The reverse gradient indicates that, at shallow
depths along the basin margin, ground water flows south and southeast, back toward the mountains and
in a direction opposing the topographic gradient. This reversed gradient does not appear to be just a
local phenomenon, rather it is defined by water levels in three, widely distributed wells groups: (1)
wells TW-88, TW-87, and TW-84 in the Weimer Road area; (2) wells TW-94, TW-5, TW-14 and TW-72
near Talpa; and (3) wells TW-57, TW-11 and TW-13 north of Weimer Road. This reversed gradient is
also suggested by water levels in the extreme western portion of the study area (wells TW-111, TW-109,
TW-7, and TW-63 and cross-section B-B’); however, varying depths of completion for these wells
preclude a definitive gradient interpretation in this area. The gradient reversal is not observed in
deeper alluvial wells (those completed at elevations less than 6800 ft). Anomalously high water
levels exist in alluvial wells within the Embudo fault zone (wells TW-4, TW-70, and TW-74), and
could reflect local perched conditions within thin Quaternary fan deposits.
Previous work by Spiegel and Couse (1969) produced a piezometric map from data collected in 1957
and 1964-1968, from basin wells in this area, that defined a uniform, NW-trending hydraulic gradient
extending from the mountain front into the basin. However, this map contained no data along the basin
margin, and made no consideration of depth of completion of the wells, rather contoured water levels
from both shallow and deep alluvial wells. This previous map did reflect elevated water levels at
locations coincident with the water table mound illustrated on Plate 2. The piezometric high defined in
this study is based on fairly limited data, and thus it is uncertain as to whether the water table mound
actually extends continuously along the basin margin, or whether it is a localized feature associated
with mountain front drainages and the infiltration of stream-derived recharge. It could be that the
actual piezometric surface reflects features of both Plate 2 and the map of Spiegel and Couse (1969),
wherein the regional basin margin gradient is a NW-trending, mountain-front-to-basin, gradient,
punctuated by local water table mounds created by infiltration of stream-derived recharge. A higher
resolution water table map extending from the basin margin to the basalt line would be required in order
to resolve the question.
25
C. Water Quality Along the Basin Margin
Although an in-depth evaluation of water quality characteristics of the aquifers was not within
the scope of this study, general observations of water quality were made based on information received
from well drillers and owners. These observations are of general interest, and provide added support for
some of the conceptual hydrogeologic interpretations discussed below. These general observations are as
follows:
•
•
•
Elevated iron (Fe) concentrations are prevalent in deep alluvial wells along the margin (e.g. TW83).
Elevated sulfur (S) concentrations and overall poor water quality are common in wells completed in
Pennsylvanian shales (e.g., TW-85 and TW-41).
A trend of warm water wells exists in the Weimer Road area defined by TW-13 (74oF), TW-88
(62oF), and TW-102 (52oF), as well as intervening wells, and appears to be coincident with a major
fault strand of the Embudo fault zone.
D. Geologic Controls on Ground-Water Flow
By developing and interpreting a water level or piezometric map within a geologic framework,
geologic controls on ground-water flow can be identified. The ground-water study by Spiegel and Couse
(1969) interpreted previous water level data to infer the existence of five areas of high transmissivity
within the Santa Fe Group sediments, four of which occur in or adjacent to our study area (see Plate 2).
Two high transmissivity zones are located in the basin generally along the Rio Grande del Rancho
(zones A and B of Spiegel and Couse, 1969), one of which (zone A) is coincident with the water table
mound depicted on Plate 2. Two additional high transmissivity zones (zones C and D) are located
generally along, but slightly north of the current trend of the Rio Fernando. Spiegel and Couse (1969)
suggested these areas were due to the local occurrence of coarser or better-sorted sediments in certain
layers of the upper alluvial facies of the Santa Fe Group. We agree, but additionally propose that
zones A and B represent a Quaternary/Tertiary axial stream facies, probably present throughout the
entire Santa Fe Group, that was deposited by an ancestral drainage associated with the Miranda
graben. The Miranda graben, a Laramide structure within the Picuris-Pecos fault system, was certainly
an active feature during and since the Tertiary and throughout the tectonic development of the Taos
graben. This ancestral drainage has likely provided a significant source of axial stream sediments to
the basin since Tertiary time. Whether a similar history is presumable for the Rio Fernando drainage
is not as certain. Significant east-west trending faults have been mapped in Pennsylvanian sediments in
the Rio Fernando canyon, but there are insufficient data on which to infer a history of movement on the
faults. The mere existence of high transmissivity zones C and D coincident with the drainage is itself
suggestive that axial stream deposits derived from an ancestral Rio Fernando exist within the Santa Fe
Group sediments.
In addition to influencing facies distribution in the developing Taos graben, the basin-margin
faults also control current ground-water movement along and across the basin margin. The Embudo fault
zone, a complex margin fault consisting of a series of fault strands that step out into the basin, cuts
Proterozoic through Quaternary units (see cross-section B-B’) across a zone 2 km wide. The major fault
strands have been noted to include broad, clay-rich, gouge zones, particularly in Tertiary rocks, and to
anastomose locally around pods of undeformed rock, both features that are likely to reduce
permeability perpendicular to the fault. In general, water level data along the basin margin (Plate 2)
suggests that the Embudo fault zone impedes but does not prevent the flow of ground water across the
fault and into the basin. This is supported by the existence of small springs at several locations
immediately upgradient of major strands of the Embudo, as well as the occurrence of significant waterlevel declines across major fault strands and dry holes at anomalous depths down-gradient of major
fault strands (e.g., TW-106 and TW-107). One well, TW-85, observed to be completed at considerable
depth (650 ft) within a major strand of the Embudo fault zone, is reported to be an extremely poor
producing well. Relatively restricted ground-water flow across the Embudo fault zone is consistent with
26
the existence of a reversed hydraulic gradient at the basin margin; conversely, elevated iron
concentrations and poor water quality in alluvial wells at the basin margin is also indicative that a
subsurface pathway does exist to move poor quality ground water from the Pennsylvanian sediments,
across the fault, and into the basin. Hence, it seems the process is one controlled by relative rates of
recharge via different mechanisms.
The large north-south Laramide faults associated with the Picuris-Pecos fault system and the
Miranda graben also influence the movement of ground water across the basin margin. In particular, the
Miranda fault, the Cuchilla del Ojo fault, and the Rio Grande del Rancho fault, together form an
extensive, pervasive fault-related fracture network that increases bedrock permeability and aquifer
transmissivity. Water level data (Plate 2) indicate the presence of a zone of anomalously low
hydraulic gradient and increased transmissivity encompassing the area between the Miranda fault and
the Rio Grande del Rancho fault, and extending across the Embudo fault zone. Because water level data
west of the Miranda fault are limited, no inference can be made regarding a continuation of this high
transmissivity zone to the west and toward the Picuris-Pecos fault. Based on available data, the area
immediately east of the Miranda fault is the only basin-margin location within the study area where
there appears to be a significant component of ground-water flow across the Embudo fault zone.
Although data within the basin are insufficient to precisely define how and where these large
north-south faults cross the basin, their presence in the basement of the Taos graben can not be
questioned. The influence these faults have on basin structure and the geometry of the alluvial aquifers
in the Taos Valley is discussed in the context of a basin-scale geologic model presented below in section
V.
E. Conceptual Model of Mountain Front Recharge
In the previous sections concerning the regions aquifers, we have presented much discussion on the
subject of recharge. However, because the topic is critical to current and future efforts to quantify
ground-water flow, availability and impacts of development, a brief summary of the findings of this
study regarding recharge to the alluvial basin aquifer is also presented here. The recharge processes
evaluated in this study have focused on mountain front processes that may be active along the basin
margin, specifically subsurface inflow of ground water from the mountains, mountain-stream-channel
recharge, and arroyo-channel recharge. The method used to evaluate which recharge mechanisms may
be active in specific geographic areas integrates geologic data, hydrologic data, and to a limited
extent, qualitative hydrogeochemical data.
The importance of mountain-stream-channel recharge as a significant recharge component to the
alluvial aquifer in the Taos Valley has been recognized since the earliest ground-water studies of the
area (Bliss, 1928; Winograd, 1959; Spiegel, 1962; Spiegel and Couse, 1969). It is clear that the major
perennial streams in the study area, Arroyo Miranda, the Rio Grande del Rancho, the Rio Chiquito,
and the Rio Fernando, all contribute a significant volume of recharge to the shallow alluvial aquifer
after they cross the basin margin fault system(s) (Embudo fault zone or Sangre de Cristo fault) and flow
across the coarse, proximal, alluvial fan deposits. Hydraulic connection and interaction between the
stream-course aquifers and the underlying/adjacent Santa Fe Group aquifer has also been shown in
previous studies (e.g., Spiegel and Couse, 1969; Cooper, 1972; Drakos and Lazarus, 1998). An additional
finding of this study is the significant potential for the major fault-controlled stream systems such as
the Rio Grande del Rancho to affect the distribution of highly permeable axial stream deposits
throughout the entire Santa Fe Group formation, and thus provide a mechanism and window for
mountain-stream-channel recharge to contribute not only to the shallow alluvial aquifer, but also to
the deep underlying system. Arroyo-channel recharge is also an active recharge mechanism to the
shallow aquifer along the basin margin, but on a significantly smaller volumetric scale than mountainstream-channel recharge.
The importance of subsurface inflow as a significant recharge mechanism in the Taos Valley has
not been addressed in any previous work. Indeed, most hydrogeologists have probably assumed that
subsurface inflow across the margin faults is negligible, and for most of the basin margin this
assumption is likely a reasonable one. However, considerable geologic and limited hydrologic data
indicate that subsurface inflow may be a very significant component of recharge at certain geographic
27
locations. In this study area, the region between the Miranda fault and the Rio Grande del Rancho
fault is shown to be such an area.
In summary, we present a simple conceptual model of mountain front recharge along the basin
margin between Talpa and Cañon. The area between the Miranda fault and the Rio Grande del Rancho
fault is the most significant recharge window along the portion of the basin margin evaluated in this
study. Both mountain-stream-channel recharge and subsurface inflow are highly active mechanisms in
this area, and together must contribute volumetrically significant amounts of ground-water recharge to
the shallow alluvial aquifer and potentially to the deeper alluvial system in the Taos Valley. The
contribution this recharge provides to the Taos Valley aquifers is potentially augmented by the
presence of highly transmissive axial stream deposits at depth throughout the Santa Fe Group
sediments at this location. Data are insufficient to evaluate recharge along the margin west of the
Miranda fault; however, the presence of thick sequences of lower Picuris formation throughout Arroyo
Miranda may certainly limit subsurface inflow in that area, and mountain-stream-channel recharge is
an active mechanism only along Alamo Arroyo. The basin margin between the Rio Grande del Rancho
and the Rio Fernando lacks an active recharge mechanism that can provide significant volumes of
ground water to the basin, as both mountain-stream-channel recharge and subsurface inflow are
negligible in this area. Arroyo-channel recharge, the only active mechanism here, generally
contributes relatively small volumes of recharge. The Rio Fernando, like the Rio Grande del Rancho, is
also a significant source of mountain-stream-channel recharge, and may potentially contribute some
subsurface flow. Additional geologic and/or geophysical data are required to more fully evaluate the
east-west faults in the Rio Fernando canyon and assess their potential for providing a significant
pathway for subsurface flow across the margin.
28
V. PRELIMINARY BASIN-SCALE GEOLOGIC MODEL
Our basin-scale geologic model is based on a 1:24,000 tectonic map that we compiled from the
following data sources:
1) Our new 1:12,000 geologic maps and cross sections.
2) The Taos SW 7.5-min quadrangle geologic map of Bauer and Kelson (1997).
3) Selected fault data from Machette and Personius (1982) 1:250,000 map, Kelson (1986), and
Kelson and others (1997).
4) Residual gravity data of Cordell and Keller (1984).
5) Residual total-magnetic intensity map of Cordell and Keller (1984).
6) Geomorphologic data from Dungan and others (1984).
7) Public domain well records from the NMOSE files.
8) Select Town of Taos exploration well records.
9) Select Pueblo of Taos/BIA well records.
10) Shallow seismic reflection surveys by C. Reynolds for BIA, dated 5/27/86 and 5/18/92.
11) Locations of springs from USGS topographic maps, Garrabrant (1993), Johnson (1998), and our
analysis of aerial photography.
12) Geologic cross sections from Glorieta Geoscience and John Sorrell (formerly of the BIA).
13) A variety of published papers and M.S. theses.
The tectonic map represents a first attempt at integrating all of the geologic, geophysical, and
subsurface data that are available (Plate 4). A comprehensive evaluation of these data sources and the
details of the tectonic model are beyond the scope of this report.
The model is limited by some data sources. The major limitation is that no detailed geologic maps
exist adjacent to our field area. In addition, parts of the gravity data of Cordell and Keller (1984) may
be insufficient to resolve moderately sized rift structures in the Taos area. For example, the Town Yard
well suggests the presence of the buried Town Yard bench, which is not expressed in the regional
gravity data. In addition, if extensive Paleozoic and early Tertiary rocks exist in the subsurface
beneath the Taos valley, gravity models probably need to be recalibrated because published depth-tobasement estimates could be incorrect. Nevertheless, Plates 4 & 5 show the most up-to-date tectonic
model using all the available data.
A. Taos Graben
The Taos graben, which was first recognized by Cordell (1978) from gravity data, is the major
structural feature in the Taos area, and probably is the key to deciphering the great variety of surficial
geologic and physiographic features in the region. At the latitude of Taos, the north-south graben is
approximately 13 km (8 mi) wide, making the main rift graben considerably narrower than the
topographic valley (about 32 km, 20 mi wide). The deepest part of the graben is just west of Taos Pueblo,
where the depth to Precambrian basement rocks is estimated at over 5000 m (16,400 ft) from gravity
data (Keller and others, 1984).
The western edge of the graben is a buried fault zone (herein named the Gorge fault zone) that
appears to underlie the Rio Grande gorge. Tectonic surface expression of the Gorge fault zone in the area
is scarce. The Dunn Bridge fault, which is exposed in the gorge near the Dunn Bridge, a normal, eastdown, north-striking, 35 m scarp that has formed in the last 3.5 Ma (Dungan and others, 1984). Recent
mapping in the Carson quadrangle by Kelson and Bauer (1998) identified an east-facing fault scarp that
branches from the Embudo fault near Pilar, and extends northward towards the Dunn Bridge fault. A
large number of springs, including Manby hot springs, exist along the Rio Grande between Taos Junction
bridge and near the Red River. It is likely that at least the hot springs owe their existence to the
buried Gorge fault zone.
The position of the Rio Grande and its gorge probably is related to the existence of the Gorge fault
zone and the western edge of the Taos graben. Dungan and others (1984) concluded that the position of
29
the river is “controlled by a combination of overall east-tilting of the plateau, westward prograding
alluvial fans, and the local control exerted by the faults, which in turn are surface manifestations of
the deep Taos graben”. The gentle east tilt of the plateau likely forced the ancestral Rio Grande
eastward, while the prograding fans probably constrained the amount of eastward migration. Possibly,
the Rio Grande incised above the Gorge fault due to the existence of a now-eroded, north-trending
fracture zone in the basalts above the fault zone.
The Taos graben was mostly formed by the time the lower Servilleta basalt erupted about 4.5 Ma.
On the Taos Plateau, the Rio Grande was superposed on the plateau after eruption of the youngest
Servilleta basalts (ca. 3 Ma), and began to rapidly entrench upon integration of the river system at
approximately 0.5 Ma (Wells and others, 1987). Although most of the high-angle faults on the plateau
did not cause thickening or thinning of volcanic flows across the faults, evidence exists for active rift
faulting during the time that the Servilleta basalts were erupted and the interlayered Chamita
sediments were accumulating (Peterson, 1981; Dungan and others, 1984). A notable example is found at
the Dunn Bridge fault where the sedimentary interval between the middle and upper basalts increases
17 m (56 ft) across the fault.
The eastern edge of the Taos graben correlates with mapped and inferred structures of the Sangre
de Cristo fault zone. Gravity data as interpreted by Reynolds (1992), showed a complex eastern fault
zone that generally steps down into the graben. Reynolds (1986, 1992) also performed shallow seismic
reflection surveys over parts of Taos Pueblo, interpreting a complex system of buried faults along the
Cañon section of the fault zone, including some small-scale horst and graben geometries. We have not
mapped in any of the areas covered by the Reynolds surveys, but we believe that evidence exists for a
southward extension of such structures into our map area. In 1996, the Town of Taos drilled an
exploration water well at the Town Yard, southwest of Taos (Plate 1). At about 600 ft, a 70-ft-thick
basalt was encountered, and at 720 ft Pennsylvanian sedimentary strata were encountered. Drilling
ceased after penetrating 300 ft of the Pennsylvanian section. Just to the northeast of the Town Yard well
is a spring that is shown on the USGS Taos quadrangle. The existence of shallow bedrock and the spring
is consistent with a large, NNE-trending structural bedrock high (herein called the Town Yard bench)
present in the subsurface. The bench corresponds with a strong gravity gradient, and projects northward
along the western edge of Buffalo Pasture wetland area of Taos Pueblo. The western boundary fault of
the bench also projects southward into the Picuris-Pecos fault system mapped south of the Embudo fault
zone. We have not found any surface expression of the western boundary fault (herein named the Town
Yard fault) of the Town Yard bench within our map area. We suspect that this buried structure has an
impact on ground water flow in the Taos area, and may represent a reactivated part of the Miranda
fault zone to the south. We do not know the exact configuration of the structural bench, and have shown
a speculative location on the maps (Plate 4).
The Taos graben appears to be shallower and narrower north of Arroyo Hondo. These complexities
might be related to the western part of the Questa caldera, which now is buried within the rift in the
Questa area. To the south, the Taos graben terminates against the Embudo fault zone in some unknown
manner. The gravity map shows that the gravity gradient along the southern extension of the Gorge
fault zone shallows such that there is no clear intersection of the graben and the Embudo fault zone.
Bauer and Kelson (1997) and Kelson and Bauer (1998) showed an unnamed east-down fault that may
represent the southernmost extension of the Gorge fault. This fault intersects the Embudo fault on Pilar
mesa, coincident with a change in strike of the Embudo fault from E-W to NE-SW (see Kelson and
others, 1997). Part of the eastern intersection is exposed where we have mapped the Cañon section
joining the Embudo fault near Talpa. However, the gravity data indicate that the master riftboundary faults probably are buried beneath Taos, and we have no field control on their southern
terminations. Reynolds (1992) depicted the borders of the Taos graben as deflected westward into the
Embudo fault zone. However, gravity data tend to smooth angular features. Based on surface exposures
near Talpa, we suspect that the buried bedrock (Tertiary and older) north of Talpa is broken into a
checkerboard pattern of fault blocks due to the superposition of north- and east-striking fault systems.
Such a pattern may have profound implications for ground water flow.
A variety of other surficial geologic and geomorphic features appear to be associated with the
Taos graben. These include Los Cordovas faults, the Gorge arch and associated flexures, stream
asymmetries, and certain linear drainages.
30
Los Cordovas faults are located above the deepest part of the Taos graben. The faults are rather
uniformly spaced, barely diverge from a north-south trend, are nearly all west-down, and appear to
terminate to the north and south. Lambert (1966) noted that they are directly on trend with both the
Picuris-Pecos fault to the south, and the Sangre de Cristo fault to the north, but failed to speculate on a
possible connection. As stated earlier, we believe that the Picuris-Pecos fault system exists in the
subsurface of the Taos graben. We do not know their locations, but we agree with Lambert that Los
Cordovas faults could be related to them. The fact that the Los Cordovas faults are short, west-down,
and are located over the deepest part of the suggests that they could be antithetic, west-dipping faults
that intersect the Taos graben at depth. On the cross sections, we have chosen to speculatively show
the major strands of the Picuris-Pecos fault system as major, Laramide, rift-reactivated structures that
shallow into the Pleistocene Los Cordovas faults.
A number of very gentle, broad flexures (Gorge arch and other folds on Plate 4) have been
identified in the Taos area (Muehlberger, 1979; Peterson, 1981; Dungan and others, 1984; Personius and
Machette, 1984). These interpretations were based on drainage patterns and stream asymmetries on the
Taos plateau. Dip changes in the basalt horizons are imperceptible in the field. In the eastern Taos
Plateau, Peterson (1981) identified seven domains of similarly oriented asymmetrical valleys, and
suggested that the warping occurred after emplacement of the Servilleta basalts. Interestingly, the two
primary flexures, the Gorge arch and the syncline along the Rio Pueblo de Taos, are parallel to the
Embudo fault zone, and bracket the deepest part of the Taos graben and Los Cordovas fault. We suspect
that the flexures are a surface manifestation of the complex subsurface fault geometry, but because our
subsurface and kinematic data are inadequate, any coherent conceptual model is poorly constrained.
B. Embudo and Sangre de Cristo Fault Zones
Previous workers have suggested that the Embudo fault zone is a relatively young rift feature that
corresponds with the initial uplift of the Picuris Mountains in the late Miocene (Manley, 1978; Ingersoll
and others, 1990). Our mapping shows that there is no distinct boundary between the Embudo fault zone
and the Cañon section of the Sangre de Cristo fault zone. The Embudo zone swings smoothly northward
in the Talpa area to merge with the Cañon section. The most reasonable explanation is that the Embudo
and the Cañon section of the Sangre de Cristo faults are the same age. Kelson and others (1997)
suggested that the Embudo and Sangre de Cristo faults both exhibit evidence of Holocene activity.
Thus, there are three ways to view the kinematic history: 1) the Embudo fault (and therefore the
uplift of the Picuris Mountains) is older than late Miocene; 2) at least parts of the Sangre de Cristo
fault zone are also young; or 3) some combination of numbers 1 and 2. Our current working hypothesis is
that the crescent-shaped Taos valley embayment, defined by the Cañon section on the east and the east
edge of the Taos graben on the west, formed in partnership with the Embudo transfer zone, in early
Miocene time. If so, the pre-early Miocene eastern edge of the rift was defined, from north to south, by
the Sangre de Cristo fault zone north of the Rio Hondo, the buried eastern edge of the Taos graben (i.e.,
Town Yard fault), and the Picuris-Pecos fault system of the Miranda graben.
C. Servilleta Basalts
The Servilleta basalt strata have a profound effect on ground water flow (Winograd, 1959; Drakos
and Lazarus, 1998). Using existing borehole data, we have attempted to define the outline of basalt
flows in the subsurface (Plates 1 and 4). In the map area, boreholes provide enough information to
constrain at least the youngest basalt unit. Not surprisingly, the basalt line closely parallels the edge
of the basin and the fault zones. Surprisingly, at least the youngest basalts exist in the subsurface as far
east as the center of Taos. Not enough deep boreholes exist to evaluate the extent of any older flows in
the map area.
We have chosen not to interpolate basalt flow geometry between boreholes on all of the cross
sections. The thicknesses of basalt intervals and locations of sedimentary interbeds are highly variable
over the Servilleta volcanic field. This is best illustrated by the basalt stratigraphy in the Rio Grande
31
gorge and comparative measured sections in the gorge and tributary canyons (figures 5 and 7 in Dungan
and others, 1984). The main Servilleta stratigraphy of lower, middle, and upper basalt members
appears to hold up over much of the Taos Plateau, and we are performing geochemical analyses of
borehole cuttings in order to evaluate basalt stratigraphy in the Taos Valley.
In his 1989 Taos Pueblo geological/geophysical review, C. Reynolds stated that the thickest
basalts were located on the horst/bench to the west of the Taos graben. We are not sure how he
determined thicknesses. Intuitively, we would expect that lavas travelling southeastward from their
eruptive vents would tend to pool in the low areas, such as over the Taos graben. The fact that some of
the basalts flowed as far as Taos means that they must have pooled in the valley in order to flow
“uphill” to onlap the eastern alluvial fans.
D. Picuris-Pecos Fault System
The five N-S fault zones of the Picuris-Pecos fault system in the southern map area form a 5-milewide zone of high strain in rocks that range in age from Early Proterozoic to less than about 18 Ma.
Based on our preliminary mapping, there is no evidence for similar fault zones to the immediate east
and west. This concentrated zone of high-angle faulting has probably had a long history of
reactivation as both strike-slip and dip-slip systems. We postulate that the faults that juxtapose
young rocks (e.g., Picuris Formation) might look like the Picuris-Pecos fault (which juxtaposes
Proterozoic rocks) at deeper structural levels. Because the older members of the Picuris Formation are
restricted to the fault zone, we suggest that the fault zone defined an Eocene(?) to early Miocene graben
(Miranda graben) that served as a locus of deposition for volcaniclastic sediments shed from the north.
At least parts of the graben have remained low during the Neogene, preserving these unusual rocks. One
consequence of this theory is that at least parts of the Picuris Formation are restricted to the graben and
its buried expression under the Taos valley.
It is likely that the Rio Grande rift used this crustal flaw during early rifting. The faults that cut
the youngest rocks (ca. 18 Ma Picuris Formation) are strike-slip, and may represent pre-Embudo transfer
zone rift kinematics. At that time, the eastern edge of the San Luis basin continued north along the
Sangre de Cristo Mountain front. At some later time (mid-Miocene?), the Embudo fault zone and the
Cañon section formed, and this section of the Picuris-Pecos fault system has been inactive ever since.
The cross sections (Plates 1 &3) show these older N-S faults as deep pre-cursors to the major Los
Cordovas fault strands. Such a correlation is speculative, but reasonable, as the N-S faults project
northwards into the similarly spaced and oriented southernmost Los Cordovas faults that are exposed
along the Rio Pueblo de Taos.
Only a few hot springs exist in the Taos area. Ponce de Leon springs are located at the intersection
of the Miranda and McGaffey faults, in Proterozoic granite and pegmatite. The water is approximately
91°F, and flows at about 300 gpm, and probably represents a deep convective system. If so, the Miranda
fault is a deep-seated structure, and perhaps represents the fossilized southern extension of the Town
Yard fault.
E. Unconfirmed East-Striking Fault System
There is some suggestion of a significant east-west fault system in the Taos area. The linearity of
the Rio Fernando, Rio Pueblo, and upper Rio Lucero may be due to east-striking faults. Although we
have not mapped the bedrock north of the southern Taos Pueblo boundary, our reconnaissance work in
Pennsylvanian rocks along the Rio Fernando found near-vertical, east-striking, strike-slip faults (see
Plate 1). Other workers have found high-angle, east-striking faults in the Sangre de Cristo Mountains
east of the pueblo. The north boundary of the Taos Pueblo buffalo fields is an east-trending vegetative
lineament that contains many small springs and seeps (Plate 4), and may represent a shallowly buried
fault. In addition, based on shallow seismic reflection surveys, Reynolds (1989, 1992) postulated buried
east-striking faults in the Taos Pueblo that appeared to be crosscut by north-striking rift-style faults. If
32
such a set of east-striking faults exists, they probably influence recharge in the mountain/piedmont
zones of the Taos Range, and affect ground water flow in the Taos valley.
33
VI. RECOMMENDATIONS AND DATA NEEDS
We view this investigation as an initial step in deciphering the geology and hydrogeology of the
Taos area. We believe that any investigation of ground water resources should be solidly based in the
best, most detailed, geologic maps available. In an area as structurally and stratigraphically complex
as Taos, where basinal structures and bedrock are covered, the chronology of deposition and
deformation must be understood. Our approach has been to produce detailed geologic maps, and then
incorporate all other data sources into a geologic model that allows one to predict the subsurface
environment, and therefore better assess the behavior of ground water. However, we have been limited
by a variety of inadequate data sources, mostly related to subsurface geology and hydrogeology.
This section presents a list of recommendations for additional data collection for both our study
area and for the Taos valley in general. Ultimately, such studies will permit a better evaluation and
quantification of ground water availability in the Taos valley.
A. Specific Data Needs In Our Study Area
1. Town Yard structural bench. We have tentatively identified a large north-trending structural
bench (the Town Yard bench) that probably extends from the Ranchos de Taos area northward to the
Buffalo Pasture area of Taos Pueblo. The bench is a major basement high that affects ground water
availability. To date, the only direct evidence of its existence is through a Town of Taos water well
that encountered bedrock at a shallow depth. We do not know whether the bench steps up to the
mountains, or whether it represents a horst with a deep sub-basin between it and the mountains. We
believe that much could be learned about this structure through a simple, quick, inexpensive gravity
survey. Such a survey would involve approximately two months of data collection and a month of
follow-up computer processing and modeling. If properly done, such a survey would provide excellent
controls on subsurface faulting and thickness of basin fill. If the bench can be successfully mapped by
geophysics, exploration boreholes and water supply wells could then be optimally located.
2. Water well inventory. We have found that trying to incorporate borehole data into our study is
a frustrating and hugely time-consuming task, oftentimes with dubious results. When well records can
actually be located, they are commonly inadequate. Although the Taos area is the focus of a lengthy
and expensive adjudication process, there apparently exists no database of boreholes. Well records for
the deep exploration wells and municipal wells can not be easily found, in spite of the fact that they
provide the best information available for solving hydrogeologic problems. Similarly, many shallow
domestic wells are not on file at the Office of the State Engineer, and most of the available logs are
improperly located and logged by the driller. Clearly, a digital database of all available data is a
necessity. Such a database should contain the essential data, such as well number, location (including
UTM coordinates), driller, date of completion, depth of completion, water level, etc. Ideally, the
database would eventually be tied into topographic maps through a GIS system. Such a system could
easily be expanded in the future to include other parameters, such as water chemistry, water quality,
etc.
3. Geologic mapping. Our field mapping was limited to the upper piedmont slope, along the
basin/mountain interface. Within our study area, detailed mapping should be done in the basin and
along the mountain front. Such mapping will provide valuable information concerning the nature of Los
Cordovas faults, the Servilleta basalts, the tectonic geomorphology of the valley, basement fault
geometries, and Pennsylvanian stratigraphy. All of which would help to better constrain the geologic
and hydrogeologic models.
34
B. General Data Needs For The Taos Valley Area
1. General geologic needs
Geologic mapping of the rest of the Taos valley. Ultimately, the remainder of the Taos area,
including the Arroyo Seco and Arroyo Hondo areas, should be mapped in detail. Until such mapping is
completed, attempts to model the geometry and hydrogeology of the basin will be limited by
incomplete data.
Fault analysis. We did not attempt a kinematic analysis of the various generations of faults in
bedrock units. Such work would help to determine when and how faulting occurred. This in turn, would
help us to better evaluate the geologic history and to better visualize the 3-D architecture of the basin.
2. Geophysical
Geophysical surveys. In our map area, and over most of the Taos valley, the only geophysical data
available are regional gravity and magnetic surveys. More focused studies using gravity, highresolution aeromagnetics, seismics, and other techniques could help resolve subsurface structure and
stratigraphy. In addition, the type of deep geothermal well logging that Dr. Marshall Reiter
(NMBMMR) is currently doing in the Albuquerque basin would add useful insights into the
communication and interaction between the shallow and deep aquifer systems.
3. Hydrologic
Ground water chemistry and age determination. Very little geochemical data exist for the Taosarea aquifers. Existing data are totally insufficient to support a thorough evaluation of water quality
or ground-water residence times in the shallow or deep alluvial aquifers. The limited geochemical
data that do exist indicate that water quality diminishes with depth and that the deep and shallow
aquifer systems have unique geochemical signatures (Drakos and Lazarus, 1998). Thus, geochemical
data will provide important insight for characterizing the ground-water flow system. Water quality
and geochemical data should be gathered in a widely spaced network of existing shallow and deep
alluvial wells completed throughout the Santa Fe Group and stream-course aquifers. Analyses should
include general chemistry, trace element chemistry, stable isotope chemistry (2H/1H and 18O/16O), and
age determination sampling that should include at a minimum 3H and 14C, and if possible, CFCs.
Evaluation of stream losses and gains. Several ground-water studies have shown that the
perennial streams in the Taos Valley are hydraulically connected to shallow stream-course and Santa
Fe Group aquifers, and mountain-stream-channel and arroyo-channel recharge are known to be
important mechanisms of mountain-front recharge to the ground-water systems. On the other hand,
surface water data indicate that certain reaches of the Rio Pueblo de Taos as well as other major
perennial streams (Red River, Rio Hondo, Rio Grande) gain flow due to ground-water accretion. An
evaluation of stream/aquifer interaction is necessary to understand both the ground-water and surfacewater systems, and to quantify ground-water and surface-water availability. Identification of critical
stream reaches that are subject to infiltration or accretion will improve water balance estimates and
help validate ground-water model results. This evaluation should include the following elements:
(a) First, estimate stream gains and losses between intervening gage stations by analyzing existing
daily discharge data. Estimates derived from daily discharge data will be more accurate and
informative than previous estimates derived from annual discharge data, and will help guide
identification of critical stream reaches requiring additional study.
(b) Second, conduct seepage runs at various low to intermediate discharges along critical reaches of
the Rio Pueblo and its tributaries. Seepage runs, which consist of measuring discharge at intervals
along a channel reach during a period of low or base flow, will identify if and where significant
channel losses or gains occur, and will quantify surface-water/ground-water exchanges. Discharge
measurements should be accompanied by measurements of specific conductance and temperature to
35
extend usefulness of the data and confidence in interpretations. Because seepage runs can give different
results at different times, seasonal or even monthly measurements should be taken over the course of a
year.
Exploration wells. The future installation of deep exploration wells should: first, be directed by
geologic criteria derived from previous geologic studies; and second, be accompanied by detailed
geologic and geophysical logging, and petrographic analysis of samples by geologists familiar with
the stratigraphy and rock formations of the area. In addition, core samples should be collected for
laboratory analysis of additional hydraulic parameters to include porosity, grain size analysis, and
saturated hydraulic conductivity.
Borehole measurements for vertically-distributed hydraulic conductivity. The most important
hydraulic parameter required to support three-dimensional (or quasi three-dimensional) ground-water
flow models is the hydraulic conductivity distribution. Traditional pumping tests provide estimates of
vertically-averaged hydraulic conductivity. However, the three-dimensional or quasi threedimensional models that are required for basin-scale ground-water flow modeling require verticallydistributed hydraulic conductivity, or in other words, the horizontal hydraulic conductivity as a
function of vertical position. This is particularly important for simulating ground-water flow in
layered sedimentary aquifers such as the shallow alluvial aquifer in the Taos area. The ability of a
ground-water model to confidently predict impacts to the Rio Grande from pumping shallow or
intermediate-depth wells on the piedmont would be greatly improved with good verticallydistributed conductivity data. Future aquifer characterization efforts in the Taos area should include
applying one of the simple, inexpensive, borehole methods for making vertically-distributed
measurements of hydraulic conductivity in new and existing wells. The most practical methodologies
(Molz and others, 1990) are flowmeter tests (Hess, 1986; Morin and others, 1988; Molz and others, 1989)
and multi-level slug tests (Zlotnik and McGuire, 1998). New technologies are emerging all the time in
response to the need for this type of data.
36
VII. ACKNOWLEDGMENTS
We thank Andy Core of the NM Office of the State Engineer for helping to arrange the funding
and define the scope of this project. Jay Lazarus and Paul Drakos of Glorieta Geosciences, Inc. provided
hydrogeologic insights and spacious accommodations in Taos. John Sorrell and Bill White of the Bureau
of Indian Affairs were helpful with regional hydrogeologic information. A number of individuals
graciously provided us with access and advice and information during the field mapping and domestic
well inventory; Benny Mondragon and Pablito Trujillo (La Serna Land Grant Association), Dave
DiCicco (Taos County), Ricardo Gonzales (Talpa/Rio Chiquito Community Association), Pete Tafoya
(Talpa), Glenda Gloss, David Delling (Abydos), Iris Foster (Arroyo del Alamo), Tom and Marjorie
Schubring, Dirk and Noel Schuurman, Charles Hyde, and Gayle Viola. We are grateful to Heather
Head and Roxanne de Graaf (Town of Taos) for access to aerial photos. Jeff Unruh (William Lettis &
Assoc.) helped with geologic mapping in the Talpa area. Lisa Peters of the NMBMMR Geochronology
Laboratory provided isotopic ages. Several of the drillers in the Taos area generously provided a
wealth of information on well locations and ground water conditions; (Jim Fennell, Jim McCann, Rodney
Stevens, Robert Cook, Joe Thomas?) Shari Kelley provided a useful review of the report. Mic
Heynekamp (NMBMMR) cheerfully and artfully drafted our digital geologic maps and cross sections.
Finally, we acknowledge the staff of Fred’s Place for providing us with delectable offerings for the
palate and the spirit, after long days in the field.
37
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Aoki, K., 1967, Petrography and petrochemistry of latest Pliocene olivine-tholeiites of the Taos area,
northern New Mexico, U.S.A.: Contributions to Mineralogy and Petrology, v. 14, p. 191-203.
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system, Sangre de Cristo Mountains, New Mexico and Colorado and adjacent areas: New Mexico
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Baldwin, B., 1956, The Santa Fe group of north-central New Mexico: New Mexico Geological Society
Guidebook 7, p. 115-121.
Baltz, E.H., 1978, Resume of Rio Grande depression in north-central New Mexico; in J.W. Hawley, ed.,
Guidebook to Rio Grande rift in New Mexico and Colorado: New Mexico Bureau of Mines and
Mineral Resources Circular 163, p. 210-228.
Bauer, P.W., 1988, Precambrian geology of the Picuris Range, north-central New Mexico [Ph.D.
Dissertation]: New Mexico Bureau of Mines and Mineral Resources, Open-File Report OF-325, 260
p.
Bauer, P.W., 1993, Proterozoic tectonic evolution of the Picuris Mountains, northern New Mexico: Journal
of Geology
Bauer, P.W. and Helper, M., 1994, Geology of the Carson 7.5-minute quadrangle, Taos County, New
Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map GM-71, scale 1:24,000.
Bauer, P.W. and Kelson, K., 1997, Geology of the Taos SW 7.5-minute quadrangle, Taos County, New
Mexico: New Mexico Bureau of Mines and Mineral Resources, Open-File Digital Geologic Map OFDM 12, scale 1:12,000.
Bauer, P.W. and Kelson, K., in prep., Geology of the Ranchos de Taos 7.5-minute quadrangle, Taos
County, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Open-File Digital
Geologic Map OF-DM 33, scale 1:12,000.
Bauer, P.W. and Ralser, s., 1995, The Picuris-Pecos fault – Repeatedly reactivated, from Proterozoic(?)
to Neogene; New Mexico Geological Society Guidebook 46, p.
Bliss, J.H., 1928, Seepage study on Rio Grande between State line bridge, Colorado, and Embudo, New
Mexico, and between Alamosa, Colorado, and Embudo, New Mexico: New Mexico State Engineer,
Ninth Bienn. Report, 1928-1930, July 1928, p. 27-40.
Casey, J.M., 1980, Depositional systems and basin evolution of the Late Paleozoic Taos trough, northern
New Mexico [Ph.D. dissertation]: Austin, University of Texas, 236 p.
Casey J.M. and Scott, A.J., 1979, Pennsylvanian coarse-grained fan deltas associated with the
Uncompahgre uplift, Talpa, New Mexico: New Mexico Geological Society Guidebook 30, p. 211217.
Cather, S.M., 1992, Suggested revisions to the Tertiary tectonic history of north-central New Mexico;
New Mexico Geological Society, Guidebook 43, p. 109-122.
Chapin, C.E., 1979, Evolution of the Rio Grande rift-a summary: in Riecker, R.W., ed., Rio Grande rifttectonics and magmatism: American Geophysical Union, Washington, D.C., p. 1-5.
Chapin, C.E. and Cather, S.M., 1994, Tectonic setting of the axial basins of the northern and central Rio
Grande rift, in Keller, G.R. and Cather, S.M. (eds.), Basins of the Rio Grande Rift: Structure,
Stratigraphy, and Tectonic Setting, Geological Society of America Special Paper 291, p. 5-25.
Chapin, R.S, 1981, Geology of the Fort Burgwin Ridge, Taos County, New Mexico: M.S. thesis,
University of Texas at Austin, 151 p.
Condie, K. C. (1980). Precambrian rocks of Red River–Wheeler Peak area, New Mexico. New Mexico
Bureau of Mines and Mineral Resources Geologic Map 50, scale 1:48,000.
38
Coons, L. M., and Kelly, T. E., 1984, Regional hydrogeology and the effect of structural control on the
flow of groundwater in the Rio Grande Trough, northern New Mexico. New Mexico Geological
Society, 35th Field Conference, New Mexico Bureau of Mines and Mineral Resources, p. 241–244.
Cooper, J.B., 1972, Letter Memorandum from James B. Cooper, U. S. Geological Survey, to R. W. Fife, U.
S. Bureau of Reclamation, re well data and production characteristics of San Juan-Chama
exploration wells, May 22, 1972, 8 pp.
Cordell, L., 1978, Regional geophysical setting of the Rio Grande rift: Geological Society of America
Bulletin 89, p. 1073-1090.
Cordell, L. and Keller, G.R., 1984, Regional structural trends inferred from gravity and aeromagnetic
data in the New Mexico-Colorado border region: New Mexico Geological Society Guidebook 35, p.
21-23.
Czamanski, G.K., Foland, K.A., Kubacher, F.A. and Allen, J.C., 1990, The 40Ar/39Ar chronology of
caldera formation, intrusive activity and Mo-ore deposition near Questa, New Mexico: New
Mexico Geological Society Guidebook 41, p. 355-358.
Drakos, P. and Lazarus, J., 1998, Hydrogeologic characterization, surface water-ground water
interaction, and water quality in the southern San Luis basin in the vicinity of Taos, New Mexico,
Dungan, M.A., Muehlberger, W.R., Leininger, L., Peterson, C., McMillan, N.J., Gunn, G., Lindstrom, M.,
and Haskin, L., 1984, Volcanic and sedimentary stratigraphy of the Rio Grande Gorge and the
Late Cenozoic geologic evolution of the southern San Luis Valley: New Mexico Geological Society
Guidebook 35, p. 157-170.
Garrabrant, L.A., 1993, Water resources of Taos County, New Mexico: U.S. Geological Survey WaterResources Investigations Report 93-4107, 86 p.
Hearne, G. A. (1975). Letter evaluating the impact of ground water withdrawals on the water levels
and the flow in the streams. Letter from Hearne of the USGS to Warren Weber of the USBR,
3/4/75.
Hearne, G. A., and Dewey, J. D. (1988). Hydrologic analysis of the Rio Grande basin north of Embudo,
New Mexico, Colorado and New Mexico. U.S. Geological Survey Water-Resources Investigations
Report 86–4113, 244 p.
Hess, A.E., 1986, Identifying hydraulically conductive fractures with a slow-velocity borehole
flowmeter: Canadian Geotechnical Journal 23, p. 69-78.
Ingersoll, R.V., Cavazza, W., Baldridge, W.S., and Shafiqullah, M., 1990, Cenozoic sedimentation and
paleotectonics of north-central New Mexico: Implications for initiation and evolution of the Rio
Grande rift: Geological Society of America Bulletin v. 102, p. 1280-1296.
Keller, G.R., Cordell, L., Davis, G.S. and others, 1984, A geophysical study of the San Luis Basin: New
Mexico Geological Society Guidebook 35, p. 51-58.
Kelley, V.C., 1978, Geology of the Española Basin, New Mexico: New Mexico Bureau of Mines and
Mineral Resources, Geologic Map 48, scale 1:125,000.
Kelson, K.I., 1986, Long-term tributary adjustments to base-level lowering in northern Rio Grande rift,
New Mexico: M.S. thesis, University of New Mexico, 210 p.
Kelson, K.I. and Wells, S.G., 1987, Present-day fluvial hydrology and long-term tributary adjustments,
northern New Mexico: In Quaternary tectonics, landform evolution, soil chronologies and glacial
deposits—Northern Rio Grande rift of New Mexico, Friends of the Pleistocene-Rocky Mountain
Cell Guidebook, p. 95-109.
Kelson, K.I., Unruh, J.R. and Bott, J.D.J., 1996, Evidence for active rift extension along the Embudo fault,
Rio Grande Rift, northern New Mexico [abs.]: Geological Society of America Abstracts with
Program, v. 28, no. 7, p. A377.
Kelson, K.I., Unruh, J.R., and Bott, J.D.J., 1997, Field Characterization, Kinematic Analysis, and
initial Paleoseismic assessment of the Embudo fault, northern New Mexico: Final Technical Report
to the U.S. Geological Survey from William Lettis and Associates, Inc., 48 p.
Kelson, K.I. and Bauer, P.W., 1998, Geology of the Carson 7.5-minute quadrangle, Taos County, New
Mexico: New Mexico Bureau of Mines and Mineral Resources, Open-File Digital Geologic Map OF
DM-22, scale 1:12,000.
Lambert, P.W., 1966, Notes of the late Cenozoic geology of the Taos-Questa area, New Mexico: New
Mexico Geological Society Guidebook 17, p. 43-50.
39
Leininger, R.L., 1982, Cenozoic evolution of the southernmost Taos plateau, New Mexico: M.S. thesis,
University of Texas at Austin, 110 p.
Lipman, P.W. and Mehnert, H.H., 1979, The Taos Plateau volcanic field, northern Rio Grande rift, New
Mexico: in Riecker, R.C., ed., Rio Grande rift – Tectonics and magmatism: American Geophysical
Union, Washington D.C., p. 289-311.
Lipman, P.W. and Reed, J.C., Jr., 1989, Geologic map of the Latir volcanic field and adjacent areas: U.S.
Geological Survey Miscellaneous Investigations Map I-1907, scale 1:48,000.
Machette, M.N. and Personius, S.F., 1984, Quaternary and Pliocene faults in the eastern part of the
Aztec quadrangle and the western part of the Raton quadrangle, northern New Mexico: U.S.
Geological Survey Map MF-1465-B, scale 1:250,000.
Machette, M.N., Personius, S.F., Kelson, K.I., and Seager, W.R., 1996, New digital map and computer
database of Quaternary faults and folds in New Mexico [abs.]: Geological Society of America
Abstracts with Program, v. 28, no. 7, p. A377.
Machette, M.N., Personius, S.F., Kelson, K.I., Haller, K.M., and Dart, R.L., 1998, Map and data for
Quaternary faults in New Mexico: U.S. Geological Survey Open-File report 98-521, 443 p.
Manley, K., 1976, The late Cenozoic history of the Española Basin, New Mexico [Ph.D. thesis]:
University of Colorado, 171 p.
Manley, K., 1978, Cenozoic geology of the Espanola basin: New Mexico Bureau of Mines and Mineral
Resources, Circular 163, p. 201-210.
Manley, K., 1979, Stratigraphy and structure of the Espanola basin, Rio Grande rift, New Mexico, in
Riecker, R.E., ed., Rio Grande rift: tectonics and magmatism: American Geophysical Union,
Washington, p. 71-86.
Manley, K., 1984, Brief summary of the Tertiary geologic history of the Rio Grande rift in northern
New Mexico: New Mexico Geological Society, Guidebook 35, p. 63-66.
Menges, C.M., 1988, The tectonic geomorphology of mountain front landforms in the northern Rio Grande
rift, New Mexico: Ph.D. dissertation, University of New Mexico, 140 p.
Menges, C.M., 1990, Late Cenozoic rift tectonics and mountain-front landforms of the Sangre de Cristo
Mountains near Taos, northern New Mexico: New Mexico Geological Society Ghidebook 41, p. 113122.
Miller, J.P., Montgomery, A., and Sutherland, P.K., 1963, Geology of part of the Sangre de Cristo
Mountains, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Memoir 11, 106 p.
Molz, F.J., Guven, O., and Melville, J.G., 1990, A new approach and methodologies for characterizing
the hydrogeologic properties of aquifers. EPA Project Summary, EPA/600/S2-90/002. Robert S.
Kerr Environmental Research Laboratory, 7 p.
Molz F.J., Morin, R.H., Hess, A.E., Melville, J.G., and Guven, O., 1989, The impeller meter for measuring
aquifer permeability variations: evaluation and comparison with other tests: Water Resources
Research, 25, p. 1677-1683.
Montgomery, A., 1953, Precambrian geology of the Picuris Range, north-central New Mexico: New
Mexico Bureau of Mines and Mineral Resources Bulletin 30, 89 p.
Montgomery, A., 1963, Precambrian geology, in Miller, J.P., Montgomery, A., and Sutherland, P.K.,
Geology of part of the Sangre de Cristo Mountains, New Mexico: New Mexico Bureau of Mines and
Mineral Resources Memoir 11, p. 7-21.
Morin, R.H., Hess, A.E., and Paillet, F.L., 1988, Determining the distribution of hydraulic conductivity
in a fractured limestone aquifer by simultaneous injection and geophysical logging: Ground Water
26, p. 586-595.
Muehlberger, W.R., 1979, The Embudo fault between Pilar and Arroyo Hondo, New Mexico: an active
intracontinental transform fault: New Mexico Geological Society, Guidebook 30, p. 77-82.
Morgan, P. and Golombek, M., 1984, Factors controlling the phases and styles of extension in the
northern Rio Grande rift: New Mexico Geological Society Guidebook 35, p. 13-20.
Personius, S.F. and Machette, M.N., 1984, Quaternary faulting in the Taos Plateau region, northern
New Mexico: New Mexico Geological Society Guidebook 30, p. 83-90.
Peterson, C.M., 1981, Late Cenozoic stratigraphy and structure of the Taos Plateau, northern New
Mexico: M.S. thesis, University of Texas at Austin, 57 p.
40
Rehder, T.R., 1986, Stratigraphy, sedimentology, and petrography of the Picuris Formation in Ranchos
de Taos and Tres Ritos quadrangles, north-central New Mexico: M.S. thesis, Southern Methodist
University, 110 p.
Read, C.B. and Wood, G.H., Jr., 1947, Distribution and correlation of Pennsylvanian rocks in late
Proterozoic sedimentary basins on northern New Mexico: Journal of Geology, v. 55, p. 220-236.
Reynolds, C.B., 1986, Shallow seismic reflection survey, Taos Pueblo, Taos County, New Mexico:
Charles B. Reynolds and Associates report to the BIA, May 27, 10 p.
Reynolds, C.B., 1989, Geological/geophysical review, Taos Pueblo area, Taos County, New Mexico:
Charles B. Reynolds and Associates report to the BIA, August 10, 8 p.
Reynolds, C.B., 1992, Shallow seismic reflection survey, northern Taos Pueblo area, Taos County, New
Mexico: Charles B. Reynolds and Associates report to the BIA, May 18, 9 p.
Soegaard, K. and Caldwell, K.R., 1990, Depositional history and tectonic significance of alluvial
sedimentation in the Permo-Pennsylvanian Sangre de Cristo Formation, Taos trough, New Mexico:
New Mexico Geological Society Guidebook 41, p. 277-289.
Spiegel, Zane (1962). Hydraulics of certain stream-connected aquifer systems. New Mexico State
Engineer Special Report, 102 p.
Spiegel, Zane, and Couse, I. W. (1969). Availability of ground water for supplemental irrigation and
municipal-industrial uses in the Taos Unit of the U.S. Bureau of Reclamation San Juan–Chama
Project, Taos County, New Mexico. New Mexico State Engineer, Open-File Report, 22p.
Steinpress, M.G., 1980, Neogene stratigraphy and structure of the Dixon area, Espanola basin, northcentral New Mexico [M.S. thesis]: University of New Mexico, Albuquerque, 127 p.
Summers, W.K., 1976, Catalog of thermal waters in New Mexico: New Mexico Bureau of Mines and
Mineral Resources Hydrologic Report 4, 80 p.
Turney, Sayre and Turney (1982). A study on the feasibility of development and construction of a San
Juan-Chama diversion water system for the town of Taos, New Mexico. Turney, Sayre and Turney
Engineers, Santa Fe, New Mexico.
Wells, S.G., Kelson, K.I. and Menges, C.M., 1987, Quaternary evolution of fluvial systems in the
northern Rio Grande rift, New Mexico and Colorado: Implications for entrenchment and
integration of drainage systems: In Quaternary tectonics, landform evolution, soil chronologies and
glacial deposits—Northern Rio Grande rift of New Mexico, Friends of the Pleistocene-Rocky
Mountain Cell Guidebook, p. 95-109.
Wilson, L., Anderson, S. T., Classan, A. et al. (1980). Future water issues, Taos County, New Mexico. Lee
Wilson and Associates, Inc., Consultant report prepared for the Taos County Board of
Commissioners, variously paginated.
Wilson, L., Anderson, S. T., Jenkins, D., and Lovato, P. (1978). Water availability and water quality
Taos County, New Mexico. Lee Wilson and Associates, Inc., Consultant report prepared for the Taos
County Board of Commissioners, variously paginated.
Winograd, I. J. (1959). Ground-water conditions and geology of Sunshine Valley and western Taos
County, New Mexico. New Mexico State Engineer Office, Technical Report 12, 70 p.
Zlotnik, V.A. and McGuire, V.L., 1998, Multilevel slug tests in highly permeable formations: 1:
modification of the Springer-Gelhar (SG) model: Journal of Hydrology 204, p. 271-282.
41
APPENDIX 1 - OTHER SELECTED REFERENCES FOR THE TAOS AREA
Aerial Photographs (1982). National High-Altitude Program 2. National High-Altitude Program 2.
Color Infrared, Roll 335, Frames 119–124. June 4, 1982.
Aerial Photographs (1981). National High-Altitude Program 81. Color Infrared, Roll 365, Frames
16–18. September 29, 1982.
Akin, P. D., and Borton, R. L. (1971). General geology and ground-water conditions in the Tres Piedras
area, Taos and Rio Arriba Counties, New Mexico. New Mexico State Engineer Open-File Report, 7
p.
Anonymous. (1958). Ground-water investigation at Arroyo Seco, Taos County, New Mexico. Consultant
report to W. F. Turney and Associates, 2 p.
Anonymous (1960). Ground-water investigation at Arroyo Seco, Taos County, New Mexico. Consultant
report to W. F. Turney and Associates, 1 p.
Applied Earth Sciences (1989). Taos Exxon station aquifer test data and analysis, 1989. Applied Earth
Sciences, Houston, Texas.
Baldridge, W. S., Dickerson, P. W., Riecker, R. E., and Zidek, J., eds. (1984). Guidebook to Rio Grande
rift, northern New Mexico. New Mexico Geological Society, 35th Field Conference, 380 p.
Baltz, E. H. (1965). Stratigraphy and history of Raton Basin and notes on San Luis Basin,
Colorado–New Mexico. American Association of Petroleum geologists Bulletin, v. 49, p. 2041–2075.
Baltz, E. H. (1978). Resume of Rio Grande depression in north-central New Mexico. In Guidebook to Rio
Grande rift in New Mexico and Colorado. New Mexico Bureau of Mines and Mineral Resources
Circular 163, p. 210–227.
Bauer, P. W., Love, J. C., Schilling, J. H., and Taggart, J. E., Jr. (1991). The enchanted circle-loop drives
from Taos. New Mexico Bureau of Mines and Mineral Resources Trips to the Geologic Past, no. 2, 137
p.
Bauer, P. W., Lucas, S. G., Mawer, C. K., and McIntosh, W. C., eds. (1990). Tectonic development of the
southern Sangre de Cristo Mountains, New Mexico. New Mexico Geological Society, 41st Field
Conference, 450 p.
Boyd, J. S. (1963). Ground-water investigation, Tres Pedras vicinity, Taos and Rio Arriba Counties, New
Mexico. U.S. Forest Service Open-File Report, 4 p.
Brimhall, R. M., and Titus, F. B. (1967). Hydrologic reconnaissance and recommendations for groundwater development on the D. H. Lawrence Ranch, Taos County, New Mexico. New Mexico Institute
of Mining and Technology Open-File Report, 24 p.
Bryan, Kirk (1928). Preliminary report on the geology of the Rio Grande Canyon as affecting the
increase in flow of the Rio Grande south of the New Mexico–Colorado boundary. New Mexico State
Engineer 9th Biennial Report, 1928–1930, p. 107–120.
Bureau of Reclamation (1955). San Juan–Chama Project: Appendix D–Hydrology. Bureau of
Reclamation, Amarillo Regional Office, Texas.
Bureau of Reclamation (1971). Definite plan report, San Juan–Chama Project, Indian Camp
System—Taos Unit, New Mexico. Bureau of Reclamation, Amarillo Regional Office, Texas.
Bureau of Reclamation (1976). New Mexico water resources—Assessment for planning purposes. Bureau
of Reclamation, U.S. Department of Interior, in cooperation with the state of New Mexico.
Chapin, C. E. (1988). Axial basins of the northern and central Rio Grande rift. In Sedimentary
cover—Northern American Craton, Basins of the Rocky Mountain region, U.S.A. Geological
Society of America—Decade of North American Geology, v. D-2, p. 167–170.
Chapin, T. S. (1981). Geology of Fort Burgwin Ridge, Taos County, New Mexico. University of Texas,
Austin, TX. Unpublished M.A. thesis, 151 p.
Chudnoff, M. (1992). Analysis of transfer of ground-water rights from To-O-The-Word Farms to the
vicinity of Taos airport. State Engineer Office Memorandum, 3/18/92.
Clark, K. F. (1968). Structural controls in the Red River district, New Mexico. Economic Geology, v. 63,
p. 553–566.
Clark, K. F., and Read, C. B. (1972). Geology and ore deposits of Eagle Nest area, New Mexico. New
Mexico Bureau of Mines and Mineral Resources Bulletin 94, 162 p.
42
Condie, K. C. (1980). Precambrian rocks of Red River–Wheeler Peak area, New Mexico. New Mexico
Bureau of Mines and Mineral Resources Geologic Map 50, scale 1:48,000.
Coons, L. M., and Kelly, T. E. (1984). Regional hydrogeology and the effect of structural control on the
flow of groundwater in the Rio Grande Trough, northern New Mexico. New Mexico Geological
Society, 35th Field Conference, New Mexico Bureau of Mines and Mineral Resources, p. 241–244.
Corps of Engineers (1975). Report on hydrologic investigations—flood plain information study—Rio
Fernando de Taos, Taos and Taos County, New Mexico. Corps of Engineers, Albuquerque District,
Albuquerque, New Mexico.
Couzens, J. K. (1974a). Historical water supply available to irrigation users diverting from the Rio
Lucero tributary to the Rio Pueblo de Taos. State Engineer Office Memorandum, 4/2/74.
Couzens, J. K. (1974b). Historical water supply available to irrigation users diverting from the Arroyo
Seco of the Rio Pueblo de Taos. State Engineer Office Memorandum, 4/2/74.
Crouch, T. M. (1985). Potentiometric surface, 1980, and water-level changes, 1969–80, in the unconfined
valley-fill aquifers of the San Luis Basin, Colorado and New Mexico. U.S. geological Survey
Hydrologic Investigations Atlas HA-683, 2 sheets, scale 1:250,000.
Crowl, C. D., and Winslow, K. C. (1974). Supplement to hydrological report for the Mission Hills
Subdivision, Taos County, New Mexico. Rio Grande Surveying Service consultant rpt., 10 p.
Dane, C. H., and Bachman, G. O. (1965). Geologic map of New Mexico. U.S. Geological Survey, 2 sheets,
scale 1:500,000.
Darnell, P. S. (1987). Application for Permit to Appropriate the Underground water of the state of New
Mexico. File: RG-40450-S-2, State Engineer Office Memorandum, 11/13/87.
Dinwiddie, G. A. (1964). Municipal water supplies and uses, northeastern New Mexico. New Mexico
State Engineer Technical Report 29B, 64 p.
Dinwiddie, G. A., Mourant, W. A., and Basler, J. A. (1966). Municipal water supplies and uses,
northwestern New Mexico. New Mexico State Engineer Office, Technical Report 29C, 197 p.
Dungan, M. A. et al. (1984). Volcanic and sedimentary stratigraphy of the Rio Grande Gorge and the
late Cenozoic evolution of the southern San Luis Valley. New Mexico Geological Society
Guidebook, 35th Field Conference, p. 157–170.
Dungan, M. A., Thompson, R. A., and Stormer, J. S. (1989). Excursion 18B—Rio Grande rift
volcanism—Northern Jemez zone, New Mexico. In Field excursions to volcanic terrains in the
western United States, Volume I—Southern Rocky Mountain region. New Mexico Bureau of Mines
and Mineral Resources Memoir 46, p. 435–486.
Earth Environmental Consultants, Inc. (1978). Geohydrological conditions in the area of the Quail Run
Subdivision, Addendum #1 and Addendum #2.
Faith, S. E. (1974). An equilibrium distribution of trace elements in a natural stream environment: the
Red River near Questa, New Mexico. New Mexico Bureau of Mines and Mineral Resources OpenFile Report 50, 54 p.
Fenneman, N. M. (1931). Physiography of the western United States. McGraw-Hill, New York, New
York. 534 p.
Gabin, V. L., and Lesperance, L. E. (1977). New Mexico climatological data, precipitation, temperature,
evaporation and wind, monthly and annual means, 1850–1975. W. K. Summers and Associates, 436
p.
Garn, H. S. (1984). Spatial and temporal variations in water quality of the Rio Grande–Red River
Wild and Scenic River, Taos County, New Mexico. In Selected papers on water quality and
pollution in New Mexico. New Mexico Bureau of Mines and Mineral Resources, Hydrologic Report
7, p.49–59.
Garn, H. S. (1985). Point and nonpoint source trace elements in a wild and scenic river of northern New
Mexico. Journal of Soil and Water Conservation, v. 40, no. 5, p. 458–462.
Garn, H. S. (1986). Quantification of instream flow needs of a wild and scenic river for water rights
litigation. American Water Resources Association, Water Resources Bulletin, v. 22, no. 5, p.
745–751.
Garn, H. S., and Thomson, B. N. (1985). Analysis of cyanide data on the Red River, New Mexico. In
Proceedings from Conference on Cyanide and the Environment, Fort Collins, CO, p. 161–174.
43
Geohydrology Associates (December 1983). Ground-water inventory of Indian trust lands, pueblos of
Taos, San Juan and Santa Clara, New Mexico.
Glorieta Geoscience, Inc. (1991). Geohydrology of the Pinones de Taos, Taos County, New Mexico.
Glorieta Geoscience, Inc., Santa Fe, New Mexico.
Gruner, J. W. (1920). Geologic reconnaissance of the southern part of the Taos Range, New Mexico.
Journal of Geology, v. 28, no. 8.
Hacker, L. W., and Carleton, J. O. (1982). Soil survey of Taos County and parts of Rio Arriba and Mora
Counties, New Mexico. Washington, D.C., U.S. Government Printing Office, 220 p.
Hagerman, C. de B. (1960). Ground-water report, Rancho Cerros de Taos (Taos County. Report to Kirby
Cattle Company, 10 p.
Hagerman, C. de B. (1973). Water availability, Top of the World (Taos County). Consultant report to
the Taos County Planning Commission.
Hagerman, C. de B. (1976). General geology and ground water conditions, Carson area, Taos County.
Consultant report, 7 p.
Hawley, J. W., compiler (1978). Guidebook to Rio Grande rift in New Mexico and Colorado. New Mexico
Bureau of Mines and Mineral Resources, Circular 163, 241 p.
Healy, F. G. (1927). Preliminary report of the feasibility of drilling for artesian water in western Taos
and eastern Rio Arriba Counties, New Mexico. In Report on the Taos–Rio Arriba Counties
investigations. New Mexico State Engineer Open-File Report, p. 133–136.
Hearne, G. A. (1975a). Letter evaluating the impact of ground water withdrawals on the water levels
and the flow in the streams. Letter from Hearne of the USGS to Warren Weber of the USBR,
3/4/75.
Hearne, G. A. (1975b). Letter on the effects of pumping ground water along the Arroyo Seco. Letter from
Hearne of the USGS to Warren Weber of the USBR, 4/8/75.
Hearne, G. A., and Dewey, J. D. (1988). Hydrologic analysis of the Rio Grande basin north of Embudo,
New Mexico, Colorado and New Mexico. U.S. Geological Survey Water-Resources Investigations
Report 86–4113, 244 p.
Heffern, E. L. (1990). A geologic overview of the Wild Rivers Recreation Area, New Mexico. In Bauer et
al., eds. Tectonic development of the southern Sangre de Cristo Mountains, New Mexico: New
Mexico Geological Society, 41st Field Conference, p. 229–236.
Hem, J. D. (1985). Study and interpretation of the chemical characteristics of natural water 3rd ed.).
U.S. Geological Survey Water-Supply Paper 2254, 264 p.
Herkenhoff, Gordon & Associates, Inc. (1981). Red River diversion feasibility report. Prepared for
Northeast New Mexico Municipal Authority, funded by Interstate Stream Commission.
Herkenhoff, Gordon & Associates, Inc. (1983). Supplemental Red River diversion feasibility report.
Prepared for Northeast New Mexico Municipal Authority, funded by the Interstate Stream
Commission.
HKM Associates (September 1992). Summary BIA water claims report. Prepared for the Taos Pueblo,
HKM Associates, Billings, Montana.
Hunt, C. B. (1977). Surficial geology of northeast New Mexico. New Mexico Bureau of Mines and
Mineral Resources Geologic Map 40, 2 sheets.
Jacobi, G. Z. (1981). Effects of organic pollution on benthic macroinvertebrates in the Rio Hondo, Taos
County, New Mexico. New Mexico Environmental Improvement Division, Water Pollution Control
Bureau —82/1, 41 p.
Jacobi, G. Z. (1984a). Intensive survey of the Red River in the vicinity of the Red River and Questa
wastewater treatment facilities and the Molycorp complex, Taos County, New Mexico, January
25–27, 1984. New Mexico Environmental Improvement Division, Surface Water Quality
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Volume II, appendices.
Wilson, L. G., DeCook, K. J., and Neuman, S. P. (1980). Final report, regional recharge research for
southwest alluvial basins. Water Resources Research Center, University of Arizona.
Winkler, H. A. (1951). Seismic exploration, Sunshine Valley, New Mexico. New Institute of Mining and
Technology, 5 p.
Winkler, H. A. (1953). A geophysical section of the Sunshine Valley ground-water basin in New
Mexico. New Mexico Institute of Mining and Technology, 12 p.
Winograd, I. J. (1955). Groundwater for stock and domestic purposes in the vicinity of Taos Junction, Tres
Piedras, and No Aqua, Taos and Rio Arriba Counties, New Mexico. U.S. Geological Survey, OpenFile Report, 20 p.
Winograd, I. J. (1959). Ground-water conditions and geology of Sunshine Valley and western
Taos County, New Mexico. New Mexico State Engineer Office, Technical Report 12, 70 p.
51
Town of Taos Well #2
“City Well”
Qfu
Town of Taos #1
“Pump House”
D U
Qal
Qal
Qt4
Qfu
Qfy
Qfy
Qfu
6950
Qfy
Qfy
?
Qfu
6885
6890/6742
scl, congl
Qp1
?
50
U
˛
Qfy/Qty
Qty
68
Qp1
Qp1
Qfu
Qal
TW–59
Town of Taos
Well #4
“Jack Denver”
Qty
Qfu
Qfu
TW–114
Tb
7000
U
BIA-5
D
Qfy
af
6919/
6775
s,g–cl
Qfu
Qfu
TW–60
Town of Taos
Well #5
“Sierra Sports”
00
Arroyo Park
test
D
Qfu
69
Qp1
Range Water
Program
Well #1
Qt 2
Qty
Plate 1. Geologic map and potentiometric surface map of the southern Taos Valley.
Qfu
Qfu
Qfu
6980/6528
20-001
25-330
43-304
15-310
Qp1
Tb
Qfu
TW-89
Qal
6945/6915
Qp1
Qt4
Qty
Qt4
Qt2
TW–113
6621/6618–6528
Qal
Qt2
Tb
Qty
Qt4
685
Tb
Qal
6935/6883
s
Qfy
Qal
Ba
sa
Qfu
TW-25
TW-11
˛
˛ss
Qal
20
TW-54
Qal
20180
Qfu
TW-71
Qfu
6835/6795
E
Qal
TW-55
65-155
6970/6840
TW-83
Qfu
Qt 2
Qal
68-144
6930/6830
s,cl,gr
20-120
Qfu
Qc/Qfy
Qfu
33-290
Qfy
0
69
TW-96
Qfu
6850/6700
0
˛
Qal
Qt4
Qal
Qfu
02/296
Qfy
Qfu
6683/6626
Qt
6825/6805
30-335
Qty
TW–14
16- 08-146
250
˛
Qfu
24-300
Qf2
69
Qal
Qfy
00
Qf2
Qty
Qal
Tp
Tplq
Qty
Qty
Qal
Qal
Qal
Qty
Qal
50
Qf2
Qty
?
t
aul
Qty
Qty
Qfy
Tpu
Qc/Tp
25-310
80-228
Qf3
32-300
Qf2
Tpu
Tpu
Tpu
Qfy
Qtg
Xa
45-190
Qfy
Tplq
27
30
Xm
64-000
Tpu
Qtg
54
28
65
76
59
53
80
54
70
17
38
34
Qfy
20
45
58-233
Qc/T
Qal
Qfy
01250
Tpu
78-032
82-348
88-340
Xho
89-190
Xvg
Tpu
61260
03
55
Xm
Xho
Picuris Mountains
Qal
75
70
Tpu
20
a
S
Md
89
89
˛a
71
50
21
••••
21
30
89
75
72
75
35
65
66
30
53
89
70
89
05
35
80
89
65
80
48
75
59
81
B a s a lt
44
82
Mu
M
Dominant
tectonic foliation or gneissic foliation, if chronology of fabric elements is unknown
85
S1 schistosity—S1 is commonly subparallel to S 0 bedding
Joints
ARROYO
HONDO
Subsurface limit of Servilleta Fm. basalts inferred from boreholes
˛
A
LOS
CORDOVAS
Zone of high transmississivity (from Spiegel and Couse, 1969)
Water table elevation contour for bedrock wells
24
47
64
89
Tpu
66
Mu
75
Xho
75
Mu
89
45
35
Q/Tpu
35
˛a
31
PUEBLO
PEAK
TAOS SW
RANCHOS
DE TAOS
OF-DM–12
OF-DM–33
SHADY
BROOK
Water well
52
50
Springs
Geologic mapping by P. Bauer and K. Kelson, 1996-1998
Hydrogeology by P. Johnson, 1998
Digital cartography by M. Heynekamp and R. Titus, 1998-1999
64
56
89
42
57
32
Mu
80
58
54
50
65
TAOS
Water table elevation contour for shallow (<6800 ft) basin wells
48
89
3
Taos
Sample location (e.g. for radiometric age)
67
Qfy
WHEELER
PEAK
84
45
89
ARROYO
SECO
36°30'
No Basalt
54
61
80
10
30
Direction of landslide movement
Qtu
˛m
56
60
70
Strike and dip of bedding or overturned bedding where stratigraphic tops are known from primary features
80
61
55
62
35
50
40
54
63
63
50
Strike and dip of bedding, vertical bedding
30 30
48
39
Qal
80
Xm
62
z
27
85
59
Trace of axial plane of syncline, with fold plunge, dashed where approximate or inferred, dotted where concealed
••••
19
33
59
Trace of axial plane of anticline, with fold plunge, dashed where approximate or inferred, dotted where concealed
••••
84
80
Mu
53
70
89
24
Md
06
05
89
Xm
40
Mesoscopic
fault showing separation
50
D
50
07
08
42
Breccia or gouge zones
U
47
31
46
Strike-slip fault—Tick shows dip
12
89
˛m
71
Fault inferred from air photography
Slickenlines on fault
30
89
Md
10
34
Fault—Movement unknown; tick shows dip if known
18
59
04
64
32
Fault with topographic expression—Barbs show facing direction of scarp; dashed where approx. located or inferred
89
Normal
or reverse fault—Solid where exposed, dashed where approximately located or inferred, dotted where
concealed; bar and ball on downthrown side; tick shows dip
••••
20
50
10
Qtg
75
50
Mu
82
59
Rdt-13
Basalt Clast
18.6 Ma
Ar/Ar
68
63
32 64
Tp
lt
Xvg
70
zone
Xm
fau
Qc
Tpu
10
08
34
59
29-250
75-218
Q/Tpu
Tpu
49-233
Xho
Asymmetric drainage
36
50
32
51
Qal
74
57
25
B'
15
˛m
64
32
Base from U.S. Geological Survey 7.5-minute quadrangles
Taos SW (1964), Taos (1964), Ranchos de Taos (1964), and
Los Cordovas (1964)
26
68
SCALE 1:12,000
15
65
1
0.5
1000
0
0
1000
2000
3000
1 MILE
4000
5000
6000
7000 FEET
89
74
49
1
57
0.5
0
64
36
79
77
60
45
35
70
36
24
75
˛a
Mu
CONTOUR INTERVAL 40 FEET
NATIONAL GEODETIC VERTICAL DATUM OF 1929
50
10°
28
Xm
1 KILOMETER
O RT H
Tpu
Xa
Qal
˛
48
42
80
89
63
Qfy
Qc
Tpu
QTg?
08-250
10-280
Tpu
89
36
33
65
32
lll
llllllllllll
Buried fault; location inferred from geophysics
07
fault
47-070
Xvg
80-340
La
Tpu
Qf0
65-270
70
••••
14
e
Tpu
53-242
Q/Tpu
72-352
10
67
85
50
on
Tpu
Tpu
Serna
Xho
Xa
Xm
22
67
lll
21
••••
18
t
Tpu
15-338
84064
89
10
Tpu
Xm
28
ul
Qf0
Tpu?
Xm
– Pecos
35-040
65
18
46
24
Qfy
Miranda
Qf1
Qc
Qc/T?
40
Md
65-080
fa
Qf0
46
89
ris
Tpu
Qal
63
85
llllllllllll
24
36
85
Tpu
15
08
Qal
80
Concealed contact
20
o
Qfy
Picu
Tpu?
41
21
35-105
36
64
Qfy
Tpu
63-150
t
Qf0
l
fau
Qfy
Xa
24
Approximate or inferred contact
12-090
25-180
ch
Tce
Xvg
Qf2
77
97
Xa
Exposed contact
47-060
Ran
20-240
Tce
35-112
Explanation of Map Symbols
12-110
35
80
fau lt
Qf0
89-070
50
56
79
61
15-000
54
80
Q/Tpu
76-015
08-013
28
10
32
87
34
68
60075
30
68
75
38-125 09
80
81
35-100
78
59
70
80
24
74
41
04
46
Mu?
70
85- 81
340
35
04
29
86
69
˛a
44
38
76
50-084
48
38
78
Qty
Qfy
Xm
Xm
25
38
38
Xm
89
65
5
48
85
Qfy
70
59
Rdt-4
Rhyolite Clast
28 Ma
Ar/Ar
350
44
15
80
08
28
20
35
56
Tpu
Qtg
12-054
28
ETIC N
Qf3
Warner Well
Qal
Qf2
Qtg
35
88
36
TRUE NORTH
Qfy
TW-108
58
25
Qal
Qc
Qf1
Qc Xa
50
17
22
MAGN
Qf0
16
74
Rdt-5
Ash
28 Ma
Ar/Ar
Qfy
85
82
75
Qfy
24
del
Qf2
76
88-190
105°37'30"
58
60
85
Qc
84
Qfy
42
82
15/270
07
15
41
05
26
de
Tce
70-310
46
an
Qf2
16
˛m
Mu
C'
75
Qc
Qf3
24
52
y
55-030
Tce
Qfy
51
D'
64
64
78
20-340
Qtg
Tpu
˛
18
75
50-206
Qty
Qal
Qf3
˛a
70
ffe
fault
Embudo
Tce
zone
26
85-140
65
Q/Tpu
13-345
Qfy
34
46
70
44
62-260
79
01
09-206
Qfy
Xp
13
29
65
47-060
64
59-220
Gr
Qf2
70310
59-264
45286 Tplc
55-019
70-204
Qc
70-236
65-240
30-070
61
57-080
43-070
70-070
88110
Ql
32-000
84
89-116
Qf2
6165-056 Qc
050
52-334 52-070
64
02/162
Qfy
Tpl
Ga
Qf3
06/260
20/030
Qfy
85-290
56
37-324
38-324
Qal
Qty
Tplq
Qty
30-338
TW-26
7235/
6845
75-040
10/020
20-245
60200
37-320
15-120
87-034
Mc
Qfy
6410/6420
Tpu
17
Qal
26-306
Steakout Well
TW-63
14
Tp
Tpu
Qal
Tpu
15-330
Qfy
02/
171
66
6845/
6765
20 75080
15
7198/7095
TW-66
25270
42345
31/
Tpl
064
30-320
15-065
o
Em
bu
70-150
55
Qf1
82-290
55-260
80
28330
30-300
55-190
Qf3
55
Md
73010
TW-73
Qf3
28-258
Ri
Qf2
do
Qty
Qf0
Tp
Qty
Qty
Xm
7040/
7095/
7065
64-048
67-308
˛ss
?
Qfy
Qf2
Tp
65-280
Qtg
6820/6810
Qf2
Qf3
05/295 70-070
77-025
34-094
15
26-330
Qc
30-270
35-100
?
Qal
67-250
Qc/Tp
TW–65
75104
50-270
TW-93
TW–67 6720
Tp
04/
308
Qal
60310
Qal
Tpl
57-002
60-326
Tplq
75
40-325
6610/6270
Qf0
30-280
55-050
55-000
Qc
45-000
Qf2
02/194
(Tp@60')
Qfy
45/134
80-320
Qty
Qfy
45-005
Mt
7200
Qfy
Qty
Qc
TW-40
84
40/264
7052/6972
75-104
˛ss
75-104
U
D
14-258
7115/7020
TW–110
Qf2
42
50-090
13280
45-284
62-310
10/342
Qf2
Q/Tpu
80-160
Tplq
Qfy
Qfy
Tpl
25-286
85-173
Qc
Qty
TW-77
6970/ 7000/6940
6940
Qf3
7115/ 6865 +
Qf3
Qf1
Tpu
22/180
2
Qal
Qal
e
on
69
700000
Qal
f Qf ?
Qf3
Qf2
TW-7
Abraham
Well
z
Tplq
6810/6793–6610
Qfy
TW–
106
70-092
20/254
55-102
44/270
Tp Qf1
Qfy
Tpu
Tplq
?
Qal
Qf1
Qal
Qty
Qty
Tp
Tpu
Qal
Qf2
Tpu
Tpu
TW-78
˛
Tp
18-310
70-100
25-280
85-095
03/
350
80080
11-240
Qf2
TW–
107
Qf2
TW–1
Tp
7045
dry/6715
7075
Qf3
85349
Qal
Tp
Qf2
Tpu
Tpu
Qf2
Qf2
Qal
Tpu
11-270
25-325
76-104
10-244
TW-101
7078/6900
s,gr–art
Tpu
Tpu
˛ls
75096
18/280 75
84-890
Qal
20-004
re
Qal
Rdt-8
White Ash
34.6 Ma
Ar/Arr
21-260
15-210
Qc
Qal
79-088
Qfy
Qf1
Qf2
˛
7000/6875
Qt 4
Qf2
30-300
Ca
Qfu
TW-41
Qal
30-334
09-276
Qf2
18-300
19-290
Qfy
Qty
Qty
39-290
Qc
6961/6821
s,gr
w/cl, artesian
Qal
75-116
16-000
Qfu
Qf1
50/205
67-095
75-320
20-274
Qfy
Qf2
Qf1
Qfu?
n
de
6845/6765
cl,s
TW-94
Qf2
c
e
s
˛cong.
80
af
6968/
6915
TW–104
04-190
o
ti
n
6915/6885
cl,s,gr
Qf2
Qal
Qfu
TW-28
Qt 2
6680/5898
15-270 75110
55-015
12-022
Qty
Qal
n
40-344
Qfy
TW–72
TW–109
UNM-1 well
88-300
02-030
Qfu
Qal
Qf2
f
20-320
Qfy
6909/6898
tgr
o
˛
17-342
Qc
Qal
Qfy
Qfu
C
Qt 2
Qal
13-076
Qfu
to
?
Spiegel and Couse (1969)
D
ris
Qf2
Qal
35-346
18-358
70-330
C
A
Qty
80/290
70-270
Sa
ng
Qf1
44-340
6890/
6840
Qfy
ño
Qal
08/303
?
Qal
˛
Qfy
Qfu
86-196
g
TW-79
Qal
87-290
10-160
Qt
Qfu
06-232
27-300
˛lst
25-296
80-330
Qal
Qfu
65-025
19-130
12-384
83-320
Qfu
Qf1
˛
73-116
Qfu
TW–75
Qal
Qf2
˛
47-300
re
TW–111
Taos Country
Club well
Qfy
Qal
Qty
20-064
82-082
30-004
Qfu
Qal
87-208
Qfu
6970/6948–6875
TW-102
70-090
TW-4
Qfy
TW–5
Spiegel and Couse
(1969)
62/044
82-180
˛ss
38-210
Qfu
10-036
6875/6830
Qal
B
Qty
?
TW-100
E'
25-225
60180
6985/
6935
85-285
Cr
Qf2
Tb
Qfy
89-304
7060/7010
Qfy
TW-88
6895/6855
sg
82-056
TW-98
TW-70
Qfu
˛ss
to
Qt2
0
78-134
23/324
Qfu?
6860/6800 6855/6751
sgr
sg
Qfu
20-140
10-180
TW-85
TW-74
6880/6808
sg
Qfu?
15-359
6970/6620
g,cl to 320
TW-87
Qfy
08-040
10/047
Qfu
6905/6843
Qal
TW–17
Qfu?
6875/6825
TW-13
6886/6843/6753
gr+s s,cl
0
69
Qal
27-070
27-300
TW-84
Qal
50-306
86-270
Qty
Qf1
26-146
˛
Qfu
6860/6749
sgr
6870/?
Qfy
85-094
7110/6825
6920/6875
gr,cl
TW–115
Qfy
Qfu
Qfu
Qf1
Tb
Qfu
˛
Qtu
85
89-324
Qty
Qal
10-040
Qfu
Qty
20/056
Qtu
17300
TW–105
0
15-040
Qtu
TW-6
lt
85-280
25-080
Qtu
Qal
04-010
60-204
de
Qt2
0
Qfy
Qal
t
al
No
Qt 2
Qt2
17-072
TW-57
?
s
a
B
Qal
Qf0
Qfy
Qfu
?
Qt4
Qal
U
7093/6957
Tb
Qt 3
82-197
D
Qal
Qt3
89-096
Qfu
Qal
Tb
695
7013/6920
?
Qt2
Qfu
Qt2
Qt2
58-070
88230
10-020
70-260
20-105
nt
Qal
Tb
Qfy
7100/7060
sh
U
TW-92
?
Qp1
Qfy
TW-50
45-344
89-270
D
is
Qty
Los
Cordovas Taos
Taos SW Ranchos
de Taos
7035/6995
sh
7050/6925
33-060
Qfu
To
w n
Qt 3
TW-48
49-290
Qal
6509/4785
Qt2
TW-32
D
˛
7070/6970
ss
D U
40/230 55
55/262
Qal
TW–112
TW-37
ai
ns
Qt4
Qt 2
7015/6930
ls
lt
Qal
Tb
Tb
Qfy
U
30050
?
RP 2000
Well
Qt 3
TW-33
6985/
6995/6970
6935
TW-82
ss,sh
6990/6985
TW-52
sh
6987/6817
10-050
ss
35/
255
?
Qp1
TW-43
TW-31
Qfu
Qty
60/240
ou
B
D U
06-175
73-330
Qfy
Qt4
A
Qty
Qal
Qt4
Qal
Qt4
TW–99
Town Yard Well
Ya
r d
L
6805/6868
Qal
7110/7040
ss
?
s
o
7025/6940
sh
Tb
Qp1
09/
190
TW-44
Qal
Qt4
Tb
TW-56
89-270
Qfy
Qfy
7030/6751
sh
6970/6911
?
Co
rd
TW-49
TW-80
Qfy
A'
7020/6945
sh
6970/6910
Qty
Tb
45-210
TW-46
TW-81
Qty
as
ov
Qt4
6955/6773
ss
Qfu
Spiegel and
Couse (1969)
Qal
22-220
TW-47
?
Qp1
F
Qt4
65-210
47-300
6985/6805
ss
Qfy
C
Qfy
85-126
zone
Qp1
u
a
Tb
TW-34
Qfy
fau
D U
s
t
l
f a
u l
t
Tb
7100
64/250
Qfy/Qty
APPROXIMATE MEAN
DECLINATION, 1996
Plates 2 & 4.
D
D´
North
South
Qt4
Qfy
Qal
Qal
7000´
Qfy
?
?
ntact ?
Gradational Co
?
6500´
Tplc
?
6000´
?
˛
?
˛
T A
T A
?
˛
Taos C anyon
Rio Fernando
?
?
Ma
Tpl
fa
eco
rna ris-P
e
u
S
Pic
La
6000´
T A
˛
Xg?
Taos
Pueblo
5500´
acequia
Qfy
TW-106
TW-107
Dry hole
Qf3
Qf
Qf2
˛
Qf2
Tplc
Tpl
T A
Ma
400´ T A
Xg
T A
Sangre
6500´
Tplq
Tpu
de Cr
isto
?
pÇ
Los
Cordo
vas
˛?
T A
Tv
pÇ
Embudo
fault zone
˛?
˛?
en
pÇ
fault z
one
Xg
Tpl
Grab
Tv
fault
Tplq
T A
T
˛
Yard
Tt?
6000´
Ta o s
7000´
T A
Tplc
G
T
Ma
Tpl
Qf3
Tb
T
pÇ
10´/7115´
260´
?
orge
eG
rand
Q
7500´
Tpl
Grad
lts
fau
Tb
Town
Rio Grande
del Rancho
˛
C´
Tpu
6500´
r
Co
Rio
Cuchilla
del Ojo
Arroyo Miranda
tact ?
ational Con
v
do
6000´
Gorge
Fault geometries are generalized on cross sections.
Thin Quaternary deposits are not shown.
7000´
zone
Q
South
Rio Chiquito
Qal
fault
as
s
5500´
North
C
Embudo
Rio Pueblo de Taos
Taos
Lo
Fault plane projected
from the west.
Talpa
section
Cañon
˛?
Picuris Mountains
lt
u
s fa
ult
Rio Pueblo
de Taos
?
?
Arroyo
Miranda
6500´
?
?
Rio Grande
del Rancho
Rio Chiquito
480´
T A
?
˛
T A
420´
Tpl
Tpu
7000´
60´/7040´
235´/6810´
Tplq
?
Tplc
Tpl
Tpu
Tt
acequia
fault
Qfu
TW-1
NM-518
acequia
Rio Grande
del Rancho
Rio
Chiquito
Talpa
TW-93
(Projected
from W.)
Embudo Fault Zone
faults
˛?
5000 feet
Scale
5500´
5500´
Fault projected
from the west
Front ed
ge
Key to wells
5000
TW-99
Taos well reference no.
in Appendix 2
Plate 2. Geologic cross sections through the Talpa area, Taos County, New Mexico
Scale
1:6,000
No vertical exaggeration
500
0
0
120
1000
240
Depth to SWL / Elev. of SWL
847-952´
Screened interval
1020´
1500 feet
Taos
Taos
SW
Ranchos
de Taos
10000 feet
36°15´
View towards 150° azimuth;
10° elevation; 50km away.
115´/ 6805
Plate 4: Southeast view of subsurface structure in the Taos, Los Cordovas,
Ranchos de Taos, and Taos SW quadrangles.
Los
Cordovas
No vertical exaggeration
Potentiometric surface
N
36°30´
105°30´
105°45´
Total depth
480 meters
360
A
West
TW-112,113 Taos/ RP2000 and
San Juan-Chama wells
well
Plate 1. Cross sections to accompany Plate 1 1:12,000 geologic map.
A'
L o s
Rio Grande Gorge
Rio Grande
6000´
USB
MSB
LSB
?
Axis of Rio
Pueblo Syncline
Basalt
Los Cordovas Taos
quad quad
Rio Grande
del Rancho
TW-99 Taos
Town Yard well
ne
zo
29´/ 6621
Screen=17-47, 97-147 180´ 151´/ 6509
Servilleta basalts not shown due to lack of control
?
f a u l t s
Rio Pueblo
de Taos
Los Cordovas
quad
Rio Pueblo
de Taos
Taos SW
quad
C o r d o v a s
˛f
Tt
Tt
Tt
Tt
˛f
pÇ
M?
6000´
ul
t
1020´
fa
ooooooooooooo
Arbitrary late Miocene reference bed
˛a
˛a
˛a
5000´
M?
˛a
Ya
2030´
4000´
pÇ
wn
4000´
To
Tt
3000´
Cañon section of
Sangre de Cristo fault
(mapped)
acequia
NM-68
115´/ 6805
rd
ooooooooooooo
Buried bedrock
faults inferred Rio Fernando
from geophysics
847-952´
Tb
5000´
East
No Basalt
3000´
˛f
˛f
˛f
˛f
2000´
2000´
Tp
Sea level
Toligocene
G r a b e n
Tt
Tt
-1000´
ooooooooooooo
M?
˛f
1000´
M?
M?
Sea level
pÇ
M?
Arbitrary early Miocene reference bed
M?
pÇ
PÇ
˛a
ooooooooooooo
ault
(volcanic and volcaniclastic rocks)
Ta o s
Gorge f
1000´
Tt
Tt
Gradational Contact
-1000´
˛?
˛f
-2000´
-2000´
Gradational Contact
pÇ
Tp
Gradational Contact
˛a
-3000´
pÇ
-3000´
Gradational Contact
Geometry of horst and graben stuctures is speculative.
Depths to ˛ and pÇ bedrock are unconstrained except for Town Yard well.
M?
-4000´
-4000´
Tp
Tp
˛f
Laramide Movement
Projection of Miranda fault
and Rio Grande del Rancho fault
B
North
Picuris
P late au
TW112,113
TaosRP 2000 and
San Juan - Chama wells
Los Cordovas
fault
Rio Pueblo
7000´
Basalt No Basalt
Qty
Qt3
29´/6621´
Qf2
TW-111
Golf Course
(BJV#1) well
Thin Quaternary deposits are not shown.
NM-570
TW-109
UNM #1
well
310´/6680
158´/6683´
180´
NM-68
Tt
9000´
TW-99
Cross Sections through Weimer neighborhood, Ranchos de Taos quad,
Taos County, New Mexico
E
E´
Taos
West
Xhor
Xhow
Xhr3
Xhr6
Xhp
Xhpl
T A
T A
Tp
A
?
3000´
Tt
˛?
Tp
Tt
˛
T
?
Tt
7000’
Projected
from N
A
A
?
A
M
?
?
?
6000’
M
-3000´
Q
˛?
-5000´
Toligocene?
Toligocene?
(volcanic and volcaniclastic rocks)
?
?
Thins onto Uncompaghre uplift to west
?
˛?
T A
T?
pÇ
Scale 1:24,000
No vertical exaggeration
0
2000
4000 feet
Projection of Picuris-Pecos fault
0
500
1000
1500 meters
North - south cross section from the Taos Plateau to the Picuris Mtns., Taos SW, and Los Cordovas quadrangles, Taos County, New Mexico
Potentiometric surface
115´/ 6805
Depth to SWL / Elev. of SWL
847-952´
Screened interval
1020´
Total depth
˛
7000’
300´ / 6970´
6750’
?
6500’
T?
-9000´
7250’
650’
?
Taos well reference no.
in Appendix 2
TW-99
Laramide (and older)
movement
-7000´
Key to wells
˛
pÇ
440’
Deep geothermal
fault?
-7000´
375’
400´/6875´
490’ 490’
pÇ
TW-85
TW-55
TW-70
290´/6985´
360´/6860´ 380´/6855´
Fault geometries are generalized on cross sections.
˛
260’
360’
?
7500’
210´ / 7060´
360´/6860´
?
Q
Fault gouge
Tp
?
On section line
Tp
?
pÇ
?
?
?
On section line
-3000´
(Well intersected fault at ~320’)
pÇ
Tp
400’ N of line
Weimer Rd.
TW-100
pÇ
?
600’ S of line
˛?
300’ S of line
Tp
TW-87
Gradational Contact
TW-83
-1000´
1000’ S of line
-1000´
East
˛
250’ S of line
?
?
Projected from N
TW-84
Sea Level
pÇ
A
pÇ
Approx. warm water trend
West
Sea Level
-9000´
T
1000´
˛?
-5000´
˛
Scale 1: 12,000
No vertical exageration
1000´
?
˛
˛˛
?
T
Tt
˛
T
˛
?
3000´
Qfu
˛
?
6000’
Zone
Tt
Xh1/2
Xv
Tp
Tt?
Tt?
5000´
Xhr4
Q
Q
Q?
Q
Q?
7000’
Fault
East
Weimer Rd.
7000´
T A
T
Xhow
Xhp
Qc
T A
2030´
Xhr5 Xhr3
Xhr6 Xhr4
Xh1/2
~1300´
1200´
Tc?
Toc?
Pleistocene
movement
850´
-10,000´
Picuris
Peak
Tt
972´
Toc? 1200´
5000´
TW-163
Steakout
well
670´
240´
151´/6509´
Arroyo Hondo
Hondo
Syncline
TW-108
Warner
well
-9000´
B´
South
Mountains
Embudo Fault Zone
“Couch” fault
(projected from
the east)
TW-7
Abraham
well
-8000´
Total depth
TW-85
TW-55
Taos
Taos
SW
quad
Screened interval
-7000´
Notes:
Fault geometries are highly generalized in cross section.
Thin Quaternary deposits not shown.
T
A
Geologic cross section through the Taos, Los Cordovas, and Taos SW 7.5´ Quadrangles, Taos County, New Mexico
Los
Cordovas
quad
847-952´
1020´
A T
Laramide Movement
A T
Laramide Movement
Depth to SWL / Elev. of SWL
TW-70
-10,000´
A T
Laramide Movement
115´/ 6805
TW-100
pÇ
1500 meters
1000
pÇ
pÇ
pÇ
A T
Laramide Movement
La Serna fau
M?
500
-6000´
Potentiometric surface
TW-83
M?
pÇ
-9000´
La Serna fau
lt?
ecos fault?
˛?
0
-5000´
Taos well reference no.
in Appendix 2
Scale 1:24,000
No vertical exaggeration
0
2000
4000 feet
TW-84
˛?
˛
(Laramide “Miranda Graben”)
˛
Key to wells
M?
Projection of
(Thins onto Uncompaghre uplift to west)
-8000´
Toligocene
Projection of
Toligocene
Toligocene
Projection of
-7000´
Projection of
Picuris-Peco
s
-6000´
La Picuris P
fault?
Tp
lt?
Tp
-5000´
TW-87
Grad
Deep geothermal
fault?
ntact
ational Co
˛
?
?
6250’
˛
Scale 1: 12,000
4x vertical exageration
= Potentiometric surface
Fault geometries are simplified on cross sections.
Thin Quarternary deposits are not shown.
Plate 3. Tectonic map of the southern Taos Valley.
.
? .?. ? .?. . . . . . . . .
?
?
?
.
?
?
?
.
?
.
?
?
?
?
?. ? . . .
.
?
?
.
?
?
?.
Qal
Qfu
Qtu
X
Qal
X
Qal
Qfu
Qfy
BIA Well #12
Qfy
Qfu
Qfu
Qal
?
˛
South Wells (2)
Qfu
Qfy
e
g
or
G
˛
˛
Qfu
ch
ar
Qfu
˛
Qfy
Qfy
Qm
Qal
Qfy
Gorge Fault
Qfy
Qfu
Qfu
Qty
Qfy
Qfy
Qfy
˛
Qal
Los Cordovas
Fault Zone
Qfy
Qm
Qfy
Qtu
Qfy
Qm
Qal
Qfy
Qtu
Qal
˛
Qtu
Qtu
Qfu
Qfy
˛
Qc/˛
Qc/˛
N
Qm
o
Ba
Qfu
sa
sa
lt
Ba
Qfu
Qfy
lt
Qal
Qfu
Qfy
N
E
Town of Taos Well #6
“Howell”
Town of Taos Well #7
“Mitchell”
Qfu
˛
Qfy
Town of Taos Wells #3 & #8
“Post Office”
D
Qfu
Qp1
Qal
Qfu
N
Qal
a
oB
s
?
20
TW-54
Qfu
6886/6843/6753
gr+s s,cl
TW-71
Qfu
6835/6795
E
6970/6620
g,cl to 320
TW-74
33-290
0
30-004
˛
Qfu
Qal
Qal
Qfy
47-300
Qt4
Qal
Qfu
02/296
Qfy
Qfu
6683/6626
Qt
TW–75
6825/6805
Qal
30-335
Qfy
TW–14
16- 08-146
250
˛
Qfu
Qfu
0
69
Qf2
Qal
0
Qf2
Qty
Qal
Qf2
Qty
Qf2
Qal
Qf3
85349
Qal
50
Qf2
Qty
?
Qf2
Qfy
Qal
Qf3
Qf2
TW-7
Abraham
Well
lt
f aQfu?
6610/6270
Tpu
Qc/Tp
25-310
Qfy
80-228
Qf3
32-300
Qf2
Tpu
Qty
Qfy
Rdt-5
Ash
28 Ma
Ar/Ar
Qfy
Qf3
Warner Well
Tce
Qfy
Qtg
Tpu
Qfy
Qtg
Qf1
Qc Xa
Xa
45-190
Qfy
Tplq
Tpu
Tpu
Qtg
Xm
64-000
54
28
65
76
59
78
70
Qfy
38
34
Qfy
20
Xa
58-233
Tpu
Xvg
88-340
10-280
Xho
89-190
Tpu
Xvg
Tpu
61260
63
03
55
Tpu
Xho
29-250
Xm
fau
Qc
Xm
Xho
Picuris Mountains
Qal
75
70
75
50
Mu
82
89
89
Tpu
g
Md
Qtg
21
••••
21
30
Fault inferred from air photography
72
75
35
65
66
30
53
89
70
89
05
35
53
70
80
65
35
70
30
85
Slickenlines on fault
30
Breccia or gouge zones
54
63
63
61
U
48
55
Qtu
˛m
Mesoscopic fault showing separation
D
54
61
59
80
81
50
56
Strike-slip fault—Tick shows dip
30
Qal
80
Xm
62
48
39
27
80
62
z
33
59
85
89
59
••••
19
84
80
Mu
Md
06
05
89
Xm
40
89
47
07
08
42
50
50
24
Normal or reverse fault—Solid where exposed, dashed where approximately located or inferred, dotted where
concealed; bar and ball on downthrown side; tick shows dip
12
89
31
46
75
Md
˛m
71
Trace of axial plane of anticline, with fold plunge, dashed where approximate or inferred, dotted where concealed
44
82
Mu
10
˛
84
67
••••
Trace of axial plane of syncline, with fold plunge, dashed where approximate or inferred, dotted where concealed
45
89
••••
24
47
48
Qfy
64
89
89
Tpu
66
Mu
75
Mu
89
45
35
Q/Tpu
35
Strike and dip of bedding, vertical bedding
30
˛a
31
52
50
56
50
40
64
89
42
57
32
Mu
80
58
54
50
75
65
Xho
32
60
Dominant tectonic foliation or gneissic foliation, if chronology of fabric elements is unknown
75
S1 schistosity—S1 is commonly subparallel to S 0 bedding
51
Xm
Qal
74
57
25
15
˛m
64
B'
15
32
26
68
80
65
89
74
49
Direction of landslide movement
79
77
50
60
45
35
70
36
24
75
˛a
Mu
Joints
57
64
36
Strike and dip of bedding or overturned bedding where stratigraphic tops are known from primary features
36
50
28
Fault—Movement unknown; tick shows dip if known
89
10
34
89
Fault with topographic expression—Barbs show facing direction of scarp; dashed where approx. located or inferred
Buried fault; location inferred from geophysics
18
59
04
˛a
50
59
Rdt-13
Basalt Clast
18.6 Ma
Ar/Ar
89
20
50
10
64
32
71
Tp
lt
Xvg
20
63
32 64
59
49-233
75-218
Tpu
68
••••
07
zone
Qc
Tpu
Xa
Qal
Qfy
Q/Tpu
32
08
34
89
La
Tpu
82-348
10
48
42
80
70
fault
Qf0
01250
08-250
lt
Qfy
47-070
65-270
78-032
Tpu
QTg?
fau
Qal
80-340
˛
14
65
e
Tpu
53-242
Tpu
Q/Tpu
72-352
36
33
10
lll
50
18
67
on
Tpu
Xa
Xm
67
85
89
••••
21
t
Qc/T
Xm
15-338
28
ul
Xho
10
70
Qfy
Tpu
84064
22
24
llllllllllll
Md
65-080
fa
Tpu
Xm
18
46
89
lll
llllllllllll
o
Tpu?
85
65
89
– Pecos
Qf0
Qc/T?
Tpu
Qal
46
40
21
20
15
24
36
63
85
Miranda
Qf1
35-040
Qc
ris
Qf0
Picu
Tpu?
Qfy
Tpu
Qfy
Tpu
63-150
25-180
08
Qal
80
Concealed contact
12-090
35-105
ch
45
Qf0
Serna
Qf2
Qfy
Approximate or inferred contact
12-110
47-060
Ran
Tce
35-112
36
41
64
fau lt
Qf0
20-240
24
80
Xa
Xvg
89-070
35
97
61
15-000
54
77
79
76-015
Exposed contact
28
10
32
87
34
Q/Tpu
08-013
50
56
68
75
68
60075
78
80
74
41
09
38-125
80
81
35-100
30
59
70
04
24
17
Mu?
Qty
80
46
29
86
69
˛a
44
38
76
54
70
04
38
53
80
85- 81
340
35
38
38
Xm
85
Tce
25
50-084
48
5
48
Explanation of Map Symbols
89
65
15
70
35
80
08
28
350
44
20
59
Rdt-4
Rhyolite Clast
28 Ma
Ar/Ar
Xm
Xm
Qfy
28
27
30
56
Qtg
12-054
35
88
36
25
Qal
Qc
Qal
Qf2
58
del
Qfy
TW-108
50
17
22
de
Qf0
16
74
Qty
Qtg
85
82
78
105°37'30"
58
24
60
76
88-190
85
Qc
84
Qfy
Qf2
42
82
15/270
05
26
07
15
41
an
Qf2
Tce
C'
70-310
46
Qc
Qf3
16
˛m
Mu
Gr
55-030
Tce
Qfy
24
52
75
75
20-340
89-116
Tpu
D'
64
84
Qal
Qf3
˛
51
18
70
y
fault
Embudo
˛a
64
ffe
Qfy
26
85-140
Q/Tpu
Qty
34
70
75
50-206
01
Tplq
13
62-260
65
47-060
64
59-220
46
44
79
02/162
13-345
zone
Xp
85-290
09-206
Qfy
Qfy
59-264
29
65
37-324
Qf2
Qf2
7235/
6845
70310
70-236
65-240
30-070
61
57-080
43-070
70-070
64
20/030
Ga
Qal
Tpu
Tpu
17
Qal
30-338
38-324
Qf3
14
66
TW-26
6845/
6765
06/260
Tpl
Mc
Qfy
6410/6420
02/
171
Tp
26-306
Steakout Well
TW-63
Tpu
TW-66
25270
20 75080
15
15-330
Tpu
Qal
TW-73
7198/7095
75-040
6165-056 Qc
050
52-334 52-070
Ql
32-000
45286 Tplc
55-019
70-204
Qc
87-034
56
88110
?
E
Qfy
u
mb
do
Qty
42345
31/
Tpl
064
30-320
55
04/
308
73010
70-150
55
Qf1
10/020
20-245
60200
37-320
15-120
Qf3
o
Qf2
Qty
Qf3
05/295 70-070
77-025
Md
Qf3
7095/
7065
15-065
80
28330
30-300
55-190
26-330
64-048
Xm
7040/
6720
82-290
55-260
15
TW-93
TW–67
Tp
Qc
˛ss
28-258
Qal
Tpl
Qf2
57-002
60-326
67-308
Qty
Qf0
Tp
45-000
Qf2
34-094
50-270
Ri
Qf2
6820/6810
Tplq
30-280
Tp
65-280
Qtg
Qfy
Qc
TW–65
75104
30-270
35-100
?
Qal
67-250
Qc/Tp
Qf0
75
40-325
10/342
Qf2
Qty
55-050
55-000
45-284
62-310
Qfy
Qty
Tpu
22/180
80-160
Qfy
13280
Qal
60310
(Tp@60')
Qfy
45-005
Mt
Qf1
Q/Tpu
2
Qal
Qal
z
?
Qal
Qf1
Qal
Qty
Qty
Qfy
˛ss
45/134
02/194
80-320
Qty
Qf2
42
50-090
7200
Qf2
Qf3
D
14-258
TW-40
84
40/264
7052/6972
Tpl
7115/ 6865+
Tpu
Tplq
e
on
69
700000
Tb
Tplq
TW–110
Qfy
Qf3
Qty
Qc
85-173
75-104
U
7115/7020
˛
Tp
Tp Qf1
Qfy
Tpu
Qal
6970/ 7000/6940
6940
Qfy
75-104
20/254
55-102
Qc
Qty
TW-77
44/270
TW–
106
Tplq
Qf2
Tpu
Qty
Qal
7075
TW-78
6810/6793–6610
Tp
dry/6715 107
Tp
Qf2
Tp
Tpu
Tpu
Tpu
TW–1
Qf2
TW–
7045
Qty
Qal
Qal
Qal
Tpu
Tp
Tplq
03/
350
80080
11-240
Tpu
Tpu
Qal
7078/6900
s,gr–art
85-095
e
Tb
Qfy
70-092
25-286
76-104
10-244
18/280 75
84-890
Qf1
11-270
25-325
ng
r
Qal
Qal
˛ls
75096
TW-101
Rdt-8
White Ash
34.6 Ma
Ar/Arr
20-004
18-310
70-100
25-280
15-210
Qc
Qal
21-260
de
24-300
Qf1
Qf2
79-088
Qfy
TW-41
Qty
30-334
30-300
˛
7000/6875
Qt 4
Qf2
18-300
19-290
09-276
Qty
Qal
39-290
Qc
6961/6821
s,gr
w/cl, artesian
n
75-116
16-000
Qfy
TW-94
io
67-095
75-320
20-274
Qfu
Qf1
50/205
t
ec
n
6845/6765
cl,s
s
˛cong.
80
Qfu?
Qfy
Qf2
Qf2
TW–104
04-190
af
6968/
6915
Qf2
Qal
Qfu
TW-28
Qt 2
6680/5898
Qal
15-270 75110
55-015
Ca
Tb
n
40-344
12-022
TW–72
6915/6885
cl,s,gr
Qty
TW–109
UNM-1 well
88-300
02-030
Qfu
Qfy
Qal
Qf2
f
20-320
Qfy
6909/6898
tgr
o
˛
17-342
Qc
Qal
Qfy
Qfu
C
Qt 2
13-076
Qfu
to
Qty
Qal
18-358
70-330
D
ris
?
Spiegel and Couse (1969)
80/290
C
A
Qty
Qf2
Qal
ño
Qal
Qf1
35-346
?
Qal
70-270
a
Qfu
08/303
S
Qal
Tb
86-196
˛lst
44-340
6890/
6840
87-290
10-160
Qt
˛
Qfy
06-232
27-300
TW-79
Qfu
65-025
19-130
Sa
Qf2
Qfu
25-296
80-330
Qal
˛
12-384
83-320
Qfu
Qf1
73-116
Qfu
re
Qty
TW–111
Taos Country
Club well
ai
0
69
6850/6700
˛
is
Qfu
Qc/Qfy
6970/6948–6875
Qfu
20-064
to
6930/6830
s,cl,gr
Qfu
TW-96
87-208
20-120
82-082
70-090
TW-4
TW–5
TW-102
62/044
82-180
6875/6830
Qfy
Qfy
Qal
Qfu
38-210
Qfu
10-036
85-285
˛ss
68-144
6985/
6935
TW-100
Qal
Spiegel and Couse
(1969)
Qal
?
E'
25-225
60180
TW-88
6895/6855
sg
Qfu
Qfu
B
Qty
Qf1
89-304
7060/7010
TW-70
Qfu
82-056
Cr
Qf2
Tb
Tb
65-155
6970/6840
Qfy
78-134
23/324
Qfu?
TW-55
6860/6800 6855/6751
sgr
sg
0
20-140
˛ss
10-180
TW-98
TW-83
Qfu?
15-359
TW-85
TW-87
6880/6808
sg
08-040
10/047
Qfu
6905/6843
Qal
TW–17
6870/?
Qfu?
6875/6825
TW-13
Qt 2
Qal
27-070
27-300
20180
TW-84
Qal
50-306
˛
?
?
Qal
6860/6749
sgr
Qal
0
69
Qal
26-146
86-270
Qal
Qfy
Qt2
Tb
˛
˛ss
Qf1
Tb
85-094
7110/6825
Qfu
Qty
Tb
TW-25
TW-11
6920/6875
gr,cl
TW–115
Qfy
Qfy
Qfu
Qfu
TW–105
alt
˛
B a s a lt
ARROYO
HONDO
Subsurface limit of Servilleta Fm. basalts inferred from boreholes
WHEELER
PEAK
36°30'
No B asalt
A
ARROYO
SECO
LOS
CORDOVAS
Zone of high transmississivity (from Spiegel and Couse, 1969)
3
TAOS
PUEBLO
PEAK
Taos
Sample location (e.g. for radiometric age)
Water table elevation contour for bedrock wells
TAOS SW
RANCHOS
DE TAOS
OF-DM–12
OF-DM–33
SHADY
BROOK
Water table elevation contour for shallow (<6800 ft) basin wells
Water well
Springs
Geologic mapping by P. Bauer and K. Kelson, 1996-1998
Hydrogeology by P. Johnson, 1998
Digital cartography by M. Heynekamp and R. Titus, 1998-1999
Asymmetric drainage
Mu
10°
Qt 2
Qf0
Qfu
Qtu
85
89-324
Qty
Qal
10-040
17300
Qty
20/056
Qtu
Qfu
nt
Tb
Qt2
0
Qfy
15-040
Qtu
TW-6
0
685
85-280
25-080
Qal
alt
04-010
60-204
Qtu
Qal
?
s
Ba
Qal
Qal
Qt2
?
?
Qfy
TW-57
6935/6883
s
de
Qt 3
Qfy
7093/6957
Tb
Tb
U
17-072
Qfu
Qal
Qt4
89-096
82-197
D
Qal
Qt3
Tb
D U
40/230 55
55/262
SCALE 1:24,000
1
0.5
1000
Base from U.S. Geological Survey 7.5-minute quadrangles
Taos SW (1964), Taos (1964), Ranchos de Taos (1964), and
Los Cordovas (1964)
0
1
0
1000
2000
0.5
3000
1 MILE
4000
5000
0
CONTOUR INTERVAL 40 FEET
NATIONAL GEODETIC VERTICAL DATUM OF 1929
Mu
R. 13 E.
6000
7000 FEET
1 KILOMETER
O RT H
Qfu
Qt2
Qt2
Qt2
7013/6920
10-020
70-260
20-105
ETIC N
Qt4
7100/7060
sh
U
58-070
88230
ns
Qty
45-344
89-270
D
TW-92
Qfy
TW-50
lt
Tb
7035/6995
sh
7050/6925
33-060
Qfy
˛
7070/6970
ss
TW-48
49-290
TRUE NORTH
Los
Cordovas Taos
Taos SW Ranchos
de Taos
Qal
Qt2
Qal
TW-32
D
U
30050
Qfu
To
w n
Qty
TW-37
Qfu
Qal
TW–112
7015/6930
ls
Qal
6509/4785
Qt 3
Qfy
zone
Qt2
Tb
TW–113
TW-43
?
Qt4
Qt4
Qt 2
60/240
TW-33
6985/
6995/6970
6935
ss,sh TW-82
6990/6985
TW-52
sh
6987/6817
10-050
ss
35/
255
?
Qal
7110/7040
ss
73-330
Ya
r d
Qty
6621/6618–6528
Tb
TW–99
Town Yard Well
Qfy
RP 2000
Well
09/
190
D U
06-175
TW-31
695
?
Qty
7030/6751
sh
TW-56
TW-44
f a
u l
t
Qty
A'
TW-46
89-270
Qfu
Qp1
Qt 3
Qfy
6805/6868
Qal
45-210
TW-49
6970/6911
7025/6940
sh
Qt4
22-220
7020/6945
sh
6970/6910
TW-80
Qfy
Tb
65-210
47-300
TW-47
TW-81
Qty
Qt4
Qt4
15-310
85-126
6985/6805
ss
6955/6773
ss
Qfu
Spiegel and
Couse (1969)
Qal
Qt4
TW-34
Qfy
Qfy
C
Qfy
Qt4
Qal
B
Qfu
TW-89
6945/6915
Qfy
Qal
43-304
7100
Qfy/Qty
Qal
Qal
Qt4
25-330
64/250
Tb
Qt4
Tb
Qfu
6980/6528
Tb
Qp1
Qp1
TW–114
Tb
20-001
M
ou
s
Lo
Tb
Qt2
TW–59
Town of Taos
Well #4
“Jack Denver”
Qty
Qfu
Qal
Qty
Qp1
˛
Qty
7000
ts
ul
Qfy/Qty
Qp1
A
T
A
Qp1
Qfu
Qfu
6890/6742
scl, congl
fau
C
D U
o
Qfu
6885
U
MAGN
d
or
Qp1
Qfy
?
S
O
Tb
s
va
Qfy
?
Tb
6950
Qp1
Fa
Qfy
Qfu
00
Qp1
Qfu
Qfy
69
U
Qfy
af
6919/
6775
s,g–cl
Qty
Qfu
Qfu
TW–60
Town of Taos
Well #5
“Sierra Sports”
50
D
Qfu
Qfu
Qt 2
U
Qal
Arroyo Park
test
D
Qfu
Town of Taos #1
“Pump House”
Qp1
BIA-5
Qfu
Qfy
Town of Taos Well #2
“City Well”
Qt4
D
Qfu
Qal
Qfu
Qal
Range Water
Program
Well #1
Qfy
Qfu
Qfu
B
A
R
G
Qfy
Qfu
Qfu
Qal
68
. . . . . . .
? . ?. ? . ?. ? ? ? ? ? ? ? ? . ? .? . .
?
.
?
.
?
.
?
.
?
.
?
?. .
?
.
?
?. .
.
?
?
? .?.
.
?
.
?
.
?
.
?
?.
.
?
? .
.
?
?. .
?
.
?
?.
.
?
?.
.
?
?.
.
?
?
U
Qfy
APPROXIMATE MEAN
DECLINATION, 1996