and
uplifts,
faults,basement-cored
wrench
Laramide
NewMexico
in southern
basins
complimentary
NM88003
LasCruces,
Department,
NewMexico
StateUniversity,
byWilliam
R. Seager,
EarthScience
Abstract
The chief mode of Laramide deformation of
the foreland area of south-central and adjacent
parts of southwest New Mexico was uplift of
relatively simple basement blocks similar in
stvle, but smaller in size, to some of those of
the central Rocky Mountains. Uplifts trend
generally west-northwest, and are asymmetric
with steep, southwest-dipping, reverse-faulted
northeast margins. Broad, less-deformed
southwest flanks plunge into deep Wind Rivertype basins filled with lower Tertiary clastic
rocks 1-2 km (3,000-7,000ft) thick. The general
style of deformation seems to extend into the
northern margin of southwest New Mexico terrane previously regarded as part of the Cordilleran "overthrust" belt. In this latter region,
right slip as well as vertical uplift and associ
ated transpressionalthrusting distinguishesat
leastsome marginal upthfusts; basinsmay be
a mixture of both Wind River and Echo Park
types. This interpretation of Laramide tectonic
styles in southern New Mexico has important
implications for the searchfor petroleum in the
Pedregosaand various late Tertiary basinsof
southern New Mexico.
of the ideas
ACKNowLEDGTuENTs-Many
expressedin this paper matured through discussionswith Glen Brown, C. E. Chapin, R.
E. Clemons,G. Mack, and S. Thompson III.
I thank Exxon for permission to use drill hole
data from their No. L Prisor well, and C. E.
Chapin, S. Cather,G. Mack, and F. E. Kottlowski for their reviews of the manuscript. I
especiallv want to thank the New Mexico
Bureauof Mines and Mineral Resourcesand
F. E. Kottlowski, Director, for their continuing support of my geologic research in
southern New Mexico.
1978;Thompson, 1982).These furassic carbonatesprobably thicken southward into the
Chihuahua trough where |urassic evaporites
are diapiric and may be responsible for Laramide decollement and "thin-skinned" folding in the Chihuahua tectonic belt, including
the Sierraluarez (Haengii and Gries, 1970).
In Cretaceoustime the Burro uplift-Deming axis (Elston, 1958;Turner, 1.952)extended
northwestward from the West Potrillo
Mountains through the Florida Mountains
into Arizona, separating4.5-km (15,000-f0thick Lower Cretaceousmarine and nonmarine rocks to the south from thin or missing sections on the foreland region to the
north (Zeller, 1965, 7970;Hayes, 1970).Upper Cretaceousand lower Tertiary rocks,
mostlysynorogenicclasticand volcanicrocks,
are nearly 4 km (13,500ft) thick south of the
Burro uplift (Zeller, 1965,1970; Hay es, 7970).
North and northeast of the Burro uplift, marine and nonmarine Upper Cretaceousrocks
are as much as 1.9 km (5,500f0 thick where
they havebeenpreservedin Laramidebasins
(Kelley and Silver, 1952).Syn- to post-orogenic uppermost Cretaceousand lower Tertiary fanglomerates,red beds, and sandstones
are of comparablethicknessin the samebasins (Doyle, 1951;Bushnell, 1953;Kelley and
Silver, 1952;Seager,1981).
Paleotectonicsetting and stratigraphy
Precambrian granitic and metamorphic
rocks form the basementof all of south-central and southwestNew Mexicoand adiacent
parts of Arizona. During the Paleozoicthe
region was buried by a south- and southwestward-thickening wedge of marine
rocks-mostly carbonates. More than 4 km
(13,500ft) thick in the southwest corner of
New Mexicoand about 2.5km (8,200ft) thick
near El Paso, the Paleozoic section thins
Introduction
northward to less than L km along a line
Corbitt and Woodward (1973), Drewes between Silver City and Truth or Conse(1978, 1982), and Woodward and DuChene
quences(Kottlowski, 1963;Greenwood and
(1981) have emphasized the importance of others, L977;Thompson, 1982).Epeirogenic
large-scaleregional overthrust faulting in ex- uplift in Middle Ordovician, Early Silurian,
treme southwest New Mexico and southeast and Late Silurian-Middle Devonian is repAge of Laramide deformation
Arizona during the Laramide (Cordilleran)
resentedby unconformitiesin the sedimenClast composition of thick fanglomerate
orogeny (Drewes, L978), some of which is tary record; these unconformities are partly
controversial (Davis, 1979). Less well known
responsiblefor the overall northward thin- units within the Hell-to-Finish and naoiit
is the array of west-northwest to northwestning. Thickness variations also reflect late
trending basement-cored block uplifts and Paleozoicsubsidenceof the PedregosaBasin
complimentary basins that have been rec- in the southwestcorner of New Mexico and
Alsoin thisissue
ognized in the foreland area to the north and adjacentparts of Arizona, as well as subsinortheast of the overthrust belt (Fig. 1.;Seager, denceof the Orogrande Basin in the southglyptosaurine
BacaFormation
1975, l98l; Brown, 1982; Brown and Cle- centralpart of New Mexico (Greenwoodand
lizard
P.77
mons, 1983). The purpose of this paper is to others, 1,977;Kottlowski, 1955). Approxiaptychilrom Los
Cephalopod
review the structural characteristics of these mately3 km (10,000ft) of Pennsylvanianand
MoyosLimestone
P.78
uplifts and basins and to show that some of Permian marine strata accumulated in the
ClaytonLakeStatePark
P. 81
the high-angle faults in the overthrust belt,
PedregosaBasinand half that amount in the
Service/News
P. 83
previously considered to be examples of re- Orogrande Basin. Between the two basins,
index
Five-year
cumulative
P.87
gional sled-runner type overthrusts, might
Pennsylvanianand Permian rocks thin across
also be interpreted as boundary faults of a positive area near the Florida Mountains
soon
Goming
basement-block uplifts. Furthermore, some (Kottlowski, 1958,1960).
SunsetRidgefluoritedeposit
of these steep faults display evidence for sigTriassicand |urassic rocks generally are abhistoryof
nomenclature
Stratigraphic
nificant right-lateral strike-slip motion and sent over most of southern New Meico, alCretaceousrocks in
Upper
marine
a s s o c i a t e d t r a n s p r e s s i o n a l ( c o n v e r g e n t though marine Jurassicrocks are known from
SocorroCounty
wrenching) and transtensional (divergent
a deep oil test southwest of Las Cruces
wrenching) structures (Reading, 1980).
(Thompson and Bieberman, 1975; Uphoff,
Formations of southwest New Mexico record
Early Cretaceousuplift and erosionof Paleozoic and Precambrian rocks from the Burro
uplift and/or deformationsouthwestor west
of New Mexico (ZelIer, L970;Drewes, 1978;
G. Mack, personal communication, 1983).
Laramide deformation commencedin latest
Cretaceoustime with movement phasesrecorded by angular unconformitiei between
the Mojado (Lower Cretaceous) and Ringbone formation (Upper Cretaceous-lower
Tertiary), between the Ringbone and the Hidalgo volcanics, and between the Hidalgo
volcanicsand relatively undeformed middle
Tertiary volcanic rocks (Zeller, 1965, 7970),
Loring and Loring (1980)have dated thrusts
cutting the Hidalgo volcanicsas Paleocene
in age, about 50 m.y. old.
Rejuvenationof at leastthe southeastpart
of the Burro uplift during the Laramide is
suggestedby lower Tertiary fanglomerate
(Love Ranch equivalent) outcrops in the
Fluorite Ridge-southern Cooke's Range area
near Deming (Fig. 1). The fanglomerate,a
very coarsegrained, proximal-fan facies,was
derived largely from Precambrianrockswhich
must have been exposed south of Fluorite
Ridge, as Paleozoic and Mesozoic rocks are
still present to the north. Presumably this
uplifted terrane also exposed the Precambrian rocks of the Florida Mountains which
in many placesare nonconformably overlain
by Iower Tertiary fan debris (Brown and Clemons, 1983;G. Mack, personal communication, 1983) and are cut by high-angle
Laramidefaults discussedlater in this paper.
Farther east and northeast in south-central
New Mexico, precise dating of Laramide
movementphaseshas so far not proved possible, although availableevidencealso indicatesa culminationof Laramidedeformation
in latestCretaceous-early
Tertiarytime (e.g.,
Kelley and McCleery, 1960;Seager,1981).
The orogenicdeposit associatedwith Laramide deformation in the San Andres-Caballo-Las Cruces areas is the Love Ranch
Formation (Kottlowski and others, L956)
consisting mostly of fanglomerate and, in
Laramide basins, finer grained red beds,
brown sandstones,and coal (Fig. 2). Upper
parts of the Love Ranch are relatively undeformed, overlap the margins of deeply
eroded uplifts, and interfinger with upper
Eocene volcanic rocks; they are therefore
largelypost-orogenicand of late Eoceneage.
Lower parts of the formation are strongly
deformed adjacent to Laramide faults and
interfinger with strata of McRae lithology, a
unit whose lowest beds are Late Cretaceous
in age (Bushnell,1953).Consequently,lower
parts of the Love Ranch are synorogenic and
may be as old as latest Cretaceous.Near basin centers(South Jornadaand Potrillo Basins), complete sections of Love Ranch
Formation are I-2 km thick and probably
range in age from Late Cretaceous to late
Eocene, although the bulk of the formation
probably is Tertiary. These relationships
support a latest Cretaceousto early Tertiary
age for T,dramidedeformation in south-central New Mefco, deformation that was com-
November 1983 New Mexico Geology
Exposuresin the San Andres and Caballo
plete by late Eocene(40-43 m.y. B.P.)time.
So far, dating of individual movement phases Mountains reveal the general nature of Laror recognition of the two-fold evolution of amide uplift margins but offer little insight
Laramide deformation describedby Chapin into the overall geometry of the uplifts and
and Cather (1981)has not proved possible. basins.In this regard structuresand unconformities in the San Diego Mountain-RobStructural style, south-centralNew Mexico ledo Mountains area,togetherwith deep drillIn south-centralNew Mexico the chief mode hole information in southern Dofla Ana
of Laramide deformation was uplift and tilt- County, enhance our interpretation. These
ing of large basement fault blocks accom- havepermitted reconstructionof a maior westpanied by subsidenceof complimentary northwest-trending Laramide uplift, facing
(Green River-Wind River type) basins. The east-northeast,whose southern flank dips
structural style is similar to that of the Lar- southward a few degreesinto a complimenamide Rocky Mountains of Wyoming and the tary (Wind River-type)basin (Potrillo Basin)
ColoradoPlateau(e.9., Kelley,1955;Stearns, filled with lower Tertiarv sedimentarv rocks
1978),although southernNew Mexico struc- more than 2 km (6,500ft; tnict (Fig. a).
In overall geometry the structure resemtures display more structural relief than those
of the Plateau and less than those of the bles the Wind River range of Wyoming and
Rockies.Small parts of uplifts are exposed adjoiningparts of the Wind River basin.The
in the Caballo, San Andres, Robledo, and northern margin of the uplift, exposedat San
Organ Mountains, and at San Diego Moun- Diego Mountain, is a west-northwest-striktain (Kelley and Silver, 1952; Bachman and ing thrust fault dipping southward 35". PreMyers, 1969;Seager, 1975, 1981;Seagerand cambrian granitic rocks form the hanging wall
others, in preparation). Large parts of the and a small exposureof folded Paleozoicrocks
centraland southernJornadadel Muerto and forms the foofwall. Near this marginal thrust,
MesillaBasinscontainremnantsof Laramide Love Ranch fanglomerate depositionally
basins.
overlies Precambrian rocks indicating uplift
Laramide uplifts trend west-northwest to and erosion of 2-2.4 km (5,500-8,000ft) of
northwest, are bordered by steep-faulted Paleozoicand Mesozoicrocksnear the thrust
margins that face east-northeastto north- in latest Cretaceousor early Tertiary time.
east, and are flanked by broad domains of Farther south, over an area 35 km (22 ml)
gently folded or tilted rocks. (Farthernorth, broad, including the modern RobledoMounin the northern Caballo and Fra Cristobal tains, thin post-orogenic Love Ranch fanranges,Laramidesfuctures swing into a more glomerate overlies successivelyyounger
northerly trend, becoming parallel with the Paleozoicstrata up to Lower Permian Hueco
centraland northern New Mexico Rockies). Limestone. This erosional truncation sugUplift margins are distinguished by narrow gests that the soufhern flank of the uplift
zonesof steepto moderatelydipping reverse
and thrust faults, which dip southwest and
modify monoclinalflexures.Uptft along these
marginsrangesfrom 1 to 5 km (3,500-17,000
ft), and the monoclinal folds seemingly are
drapes across the edges of basement fault
. Scisnce
blocks. The Bear Peak fold and thrust zone
andSsrvice
in the southern San Andres Mountains is a
1983
Volume 5, No. 4, November
good example, and this zone also illustrates
published quarterly by
New Mexico Bureau ofMines and Mineral Resources
some of the subsidiary thrusts that can deadivision ofNew Mexico Institute ofMining& Technology
velop in the compressedbeds on the downthrown side of the fault zone (Fig. 3a).
BOARD OF REGENTS
Ex Officio
An uplift margin exposed in the central
Toney Anaya, Covernor of Ne|| Mexico
and southern Caballoschangesalong strike
Leonard DeLayo, Srperintendenl oJ Public Instruclion
Appointed
from simple, like the BearPeakfold and thrust
Judy Floyd, Pres., 19'7'7-198'7,Las Cruces
zone, to more complex (Fig. 3b,c). In this
William G. Abbott, Secty/Trcas., 196l-1985, Hobbs
Donald W Mods, 1983-1989, Los Alamos
example, the level of erosion of the footwall,
Robert Lee Sanchez, 1983-1989, Albuqwrque
from high in the Paleozoicsection to the PreSteve Tones, 196'7-1985, Socorro
cambrian, revealsthat the uplift-margin fault
New Mexico lnstitute ofMining& Technology
dips more steeply (- 50) where it transLaurence H. Lattman
President .
gressesPrecambrianrocks, flattening to 30New Mexico Bureau of Mines & Mineral Resources
Director .
.. FrankE.Kottlowski
40" at higher levels. The marginal fault also
Deputf Dircctor
George S. Austin
bifurcateslocally into two strands, each asSubscriptions: Issued quarterly, February, May, August,
sociated with a monoclinal flexure or large
November; subscription price $6.00/yr.
Editoriol motter: Contributions
of possible marerial for
overturned fold (Fig. 3c). The hanging wall
consideration in future issues of NMG are welcome.
rocks of this uplift, also exposedin the southArticles submitted for Dublication should be in the edem Caballos,were broadly folded and eroded
itor's hands a minimum of five (5) months before date
of publication (February, May, August, or November).
locally to the Precambrianby late Eocenetime
Address inquiries to Marla D. Adkins-Heljeson, editor of
(involving erosionof 2.5 km [8,200ft] of PaNew Mexico Ceology, New Mexico Bureau of Mines &
Mineral Resources.Socorro. NM 87801
leozoicand Mesozoicrocks),as indicatedboth
Published as public domain, thereJore rcproducible
without
by clastsof Precambrianrock in Love Ranch
pem ision. So urce credit requ ested.
fanglomerate and by local nonconformities
Circulotion: 1,4{n
betweenPrecambriangranite and Love Ranch
Prirter. University of New Mexico Printing Plant
Formation.
New A4exfic@
GEOLOGY
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FIGURE l-Location
tim'itsof Corditteron
overfhrrri-
b e l t o f C O r b i t f o n d W o O d w o r d( 1 9 7 0 )
o n d D r e w e s ( t g 7 o8 -) o - o - o - o
t1:::l_.1.1""-..,i^,?,i,:?^-,
I h r u s l o r r e v e r s e l o u l t s/
-.-.-.-.
1 9 8 2 ) ..-.-.-.-,
ond
O
nd D
Drewes
f e W e S ((t982)
(o
r r o w ss h o ws t r i k e - s l i pm o l i o n)
O
5Okm
map, southwest New Mexico; note location of Figs. 3, 4, 6,7, and 9 structure sections.
dipped south a few degrees. Thirty km (18
mi) still farther south, in the Grimm and
others American Arctic Limited No. 1 Mobil
32 oil test, Cretaceous and Jurassic rocks
overlie the Hueco, and basinal clastic rocks
Love Ronch Formofion
SW
(sandstone,coal, fine-grained red beds) corLove Ronch Formoiion
relative with the Love Ranch are more than
bosn
r
2 km (6,500ft) thick (Thompson and Bieberb o s i nf o c i e s
focies
man, 1975;Uphoff, 1978;Thompson, 1982).
P o l e o , zo i c
r OCK
S/
Thus the uplift is strikingly asymmetric, with
M e s o zo i c
M e s o z oci
that dips perhaps 10P r e c o m b r i o nr o c k s
P o l e o z o i cr o c k s a broad southern flank
rocks 12' southward into a deep, complimentary
lkm
basin. The slope is interrupted in at least one
placeby a steep, south-dipping reversefault,
kmlO 5
O
with displacement of approximately 300 m
2-Diagrammatic
section
showing
features
of
Laramide
uplifts
and
basins
in
south-central
IIGUS!
(1,000 f0, that is exposed in the northern
New lvlexico; note syn- and post-orogenic relationships in Love Ranch Formation adjacent to uplift
RobledoMountains. Whereasthe north-south
marSrns.
Neu;Mexico Geology November 1983
cross-sectionalgeometry of this uplift is fairly
well constrained,its eastemand westem limits
areunknown becauseof cover of young rocks.
Florida-Big Hatchet-Little Hatchet
Mountains
A major northwest-trending reverse fault
in the southern Florida Mountains, previously interpreted as the front edge of a re-
gional overthrust (Corbitt and Woodward,
1973;Woodward and DuChene, L981), has
recently been reinterpreted as the upthrust
margin of a basement block (Brown, 7982;
Brown and Clemons, 1983). The fault dips
approximately 85osouthwest (after removal
of IateTertiary tilt). Brown (L982),Brown and
Clemons(1983),and Clemonsand Brown (in
press) argued for predominantly vertical
NE
) ouo,n,onn.
o fe x p o s u r e s
I
t
2km
321
.t
I
o
z rm
,
o
p€
km2
I
FIGURE 3-a.) Composite cross section through Bear Peak fold and thrust belt, southern San Andres
Mountains. b,c.) Cross sections through Laramide uplift in southern Caballo Mountains. Effectsof late
Tertiary block faulting have been removed from all three sections.Th-Tertiary Love Ranch Formation,
K-Cretaceousrocks, Pu-upper Paleozoicrocks, Pl-lower Paleozoicrocks, and p€-Precambrian rocks.
movement along the fault. However, compelling evidence for substantial right{ateral
slip also is indicated primarily by large-scale
drag of Paleozoicfootwall rocks in the footwall adjacentto the southeastexposuresof
the upthrust (Fig. 5). Adjacent to the fault,
the southern limb of the drag fold seemingly
has been segmentedinto complex thin slices
bordered by low-angle faults, which are
stackedand shearedout in the footwall along
the length of the fault to the northwest (Fig.
6). Most of the faulting resulted in younger
rocks displaced over older (normal faults),
but some produced typical thrust relationships of older over younger. Both styles
of faulting "root" downward into the major
reversefault and are considered to be a product of transpression in the fault zone.
Numerous high-angle normal faults also indicate local extension in the zone. Another
indication of strike slip along the major reverse fault is the dissimilar Precambrian
rockson either side of the fault (Fig. 5), which
also yield different K-Ar ages (Clemons, in
press).However, a component of northeast
motion is also indicated by thrust-faulted,
northeast-vergent folds, located in footwall
rocks. Collectively, the structures indicate
oblique right slip on the major steep fault,
witha smallcomponentofmovementtoward
the northeast, and strong transpression of
bedded footwall rocks. If the length of the
sheared-outlimb of the drag fold is a reliable
index, the amount of strike slip could be 5-6
km (3-3.5 mi), which is probably at least as
much, if not more, than the vertical component of movement.
The uplifted basement block in the southern Florida Mountains appears to be only
one component of a much broader, faulted
basement uplift, as shown inFig. 7. The basin adjacent to the northem flank of the uplift
is identified by the full section of Paleozoic
and Cretaceousrocks exposedin the Fluorite
Ridge-GoatRidge-Cooke's Rangeareaa few
kilometers north of Deming. Very coarse
grained proximal-fan deposits of early Tertiary age (Starvation Draw member of Rubio
PeakFormation; Clemons, 1982)overlie Cretaceousrocks in this area and were derived
largely from Precambrian and lower Paleozoic rocks. The uplift margin exposing these
Precambrian-Paleozoicrocks presumably was
located not far south of the Fluorite Ridge
areain an area now covered by bolson grav-
+-LoromidePotri|loBosin_<-LoromideRob|edo-SonDiegoup|ift+N
q
l o t e T e r t i o r yM e s i l l oE o s i n
l o t eT e r fi o r y R o b l e d oh o r s t l o t eT e r t i o r yf o u l t b l o c k s
G r i m mo n d o l h e r s n o . l
M o b i l 3 2 , T . 0 . 2 r . 7 5 9f t
Son Diego Mln.
t2
2
iet-'\
KJ
Pu
PI
I
I
\\
| /
.
8km
Ts
-5.OOOft
- s.l.
--5.OOO
--ro.ooo
--r5,ooo
20.ooo
u
and
FIGURE 4-Cross section through Laramide Potrillo Basin and Robledo-San Diego uplift. Note overlap and thinning of Tl unit onto uplift
truncation of Pu and PI units beneath the Tl unconformity. Ts-Santa Fe Group (Tertiary), Tv-middle Tertiary volcanic rocks, Tl-lower Tertiary
fanglomerate,sandstone, and coal (Love Ranch and correlative units), Kf-Cretaceous-furassic rocks, Pu-upper Paleozoicrocks, Pl-lower Paleozoic
rocks, p€-Precambrian rocks, and Ti-Tertiary intrusive rocks.
November 1983 New Mexico Geology
els. Farther south, near Deming, the Seville
Trident No. 1 McSherry well penetratedPrecambrianrocks at II,590 ft beneathQuaternary-Tertiary basin fill and Tertiary volcanic
rocks (S. Thompson III, written communication, 1983).Significantly,no lower Tertiary
fan deposits (Starvation Draw Member and
Lobo Formationof Lemley, 1982)were found
above the Precambrian.Still farther south,
outcropsin the Florida Mountains reveal thin
Lobo fan deposits nonconformably above
Precambrianor lower Paleozoicrocks, and
fwo steep faults, both downthrown to the
north, have been mapped. One of thesefaults
was describedin the previous paragraph.The
nearly full section of Paleozoicrocks exposed
in the TresHermanasMountains, southwest
of the Florida Mountains, seemingly represents the southern flank of the broad uplift.
Thus, the broad uplift spans the region from
just south of Fluorite Ridge to the southern
Florida Mountains, an area where Precambrian and lower Paleozoicrocks were deeply
erodedand widely exposedin early Tertiary
time. Individual fault blocks stairstepdown
to the north or northeastas a result oi movement on steep faults with major strike-slip
components of motion. The uplift is presumed to have had the same northwesterly
trend as the faults. Its location along strike
with the earlier Mesozoic Burro uplift suggeststhat the Laramide block uplift may have
been reactivated along Burro uplift strucfures.
Somewhat similar structural relationships
exist at Granite Pass and Hatchet Gap between the Big Hatchet and Little Hatchet
Mountains (Fig. 1). Zeller (1970,1975)mapped
drag and second-orderfolds south of Hatchet
Gap which suggestan important right-lateral
component of movement on a major westnorthwest-trendingsteep fault (Fig. 8). This
fault, and the southwest-dippingreversefault
which juxtaposes Precambrian granite and
Lower Cretaceous sedimentary rocks at
GranitePass(just north of HatchetGap), may
be interpretedas oblique-slipupthrusts maiginal to an uplifted basement block. (A Laramide age for these faults is interpreted
becauseof their reverse-faultgeometry, their
northwest trend which is truncated by late
Tertiary, north-trending, range-boundary
faults, and the intrusion of the Granite Pass
fault by a stock of mid-Tertiary granite.)The
uplifted block includes all of the modern Big
Hatchet Mountains (Fig. 9). Generally, Paleozoic strata in the Big Hatchet range dip
southwestward, although broad folds are
present. Fold axes and northeastward-dipping thrusts indicate tectonic transport toward the southwest over large parts of the
range, a relationship that seems more consistentwith horstlike block uplift of the range
and/or transpression of hanging wall rocks
(Fig.9), rather than regionalnortheastoverthrusting (S. Thompson, III, written communication, 1983).North of Granite Pass,
thick Cretaceous and Tertiarv sedimentarv
rocks and Hidalgo volcanic roiks of the Littl-e
Hatchet Mountains were preserved in the
basin footwall of the faults of Granite Pass
1 o 7 " 3 7 ' 3 0 "W
+1 +J
+J ++
+ ++ f
++
T
++ +
-t + +
I
+
+ + ++ +
+ + +t
+f
\
l-
+
++ +
+ I t++
++
+ t
F
t +++ +
+ ++ t
+ ++ +
+ ++
s f r i k el i n e s
++ i f + +
++ r+ ].+
f + ++++ +
+ | ++ l-+
+ +++ t+
+ + + + + +++
++++++++
+ + t r e s+ + + +
++t++f++
+ f ++++++
+++f++++
++ + + + ++ + + + + t f +
+++++++++++
++ + ++i +f +++r;
+ + + + ++
*#fiil
I
32.O5-N
strike
lines
?pt
p€q
\
/
\'
/
-
tt
.
N,\)--'r'-)-.,'r\$-'
?
t_ t
\'r
/
\
'
-
l/
t-
.l
,0"),).
t-/t
I/
,
rikelines
s h o w i n gd i p
direction
q!'rrr
\/
--r-.''-it-
4-'[-l
-
r
/
t
\
,t.-
/\
/
\
/l
a
l-
l-1\
\-/)rn^
",/-L.l
l\
\
,/ \ |
1
\t
I
'I
./1.
\
tl
FIGURE S-Geologic map of southern part of Florida Mountui.,r; g"olotgyafter Brown l'rt#r), at"-o.r,
and Brown (in press), and Clemons (in press). Lines with tick marks are strike lines showing dip
direction. Note large drag in Paleozoicstrata at southeastend of range and different Precambrianrocks
on either side of Florida Mountains "upthrust," both of which are taken as evidence of significant right
slip on "upthrust." The blue-shadedareais complexly broken by closely spacednormal and thrust faults;
it is bounded by low-angle faults which steepen downward to merge with Florida Mountains upthrust.Tv-middle Tertiary volcanic rocks, Tlr-Love Ranch fanglomerate, Pz-Paleozoic sedimentary
rocks, p€s-Precambrian syenite, and p€g-Precambrian granite
F l o r i d oM t s . u P t h r u s l
p€s
no verlicol €roggerolion
NW
/Florido Mts
uPihrusl
Tpoott
qooo
5,ooo
4poo
FIGURE 6-Cross sections acrossFlorida Mountains "upthrust" (oblique-slip reverse fault) taken from
Brown (1982)and Brown and Clemons (in press). Thrusting in footwall rocks seems to be rdsult of
transpression. See Fig. 1 for location. Tlr-Love Ranch fanglomerate, Pu-upper Paleozoic rocks, Pllower Paleozoicrocks, p€s-Precambrian syenite, p€g-Precambrian granite, A-strike-slip movement
away from viewer, and T-strike-slip movement toward viewer.
F
Neu Mexico Geology November 1983
-Reiuven
oled
s
R i n g b o nBeo s i n> < L o r o m i d eF l o r i d ou p l i ft +
(northflonk)
Burro
uPlift
(Loromide)+
N
S o u t hF l o r i d oM t s .
iiiii:ii;''t:-:;';
,:.;;'4!",.
'i'Poleozoic
t
t
rocrc
t
Pr€combrion
rocks(stlnite)
og
lows T6rliory fon deposils- /
(Lobo Fm.-storvolion O.qw) /
Precombrion rocks
(gronite)
2km
opprorimole3cole
l6 km
FIGURE 7-Dagrammatic section from Fluorite Ridge southward through Florida Mountains to Tres
Hermanas Mountains; effectsof late Tertiary faulting and middle Tertiary intrusives have been omitted
in order to emphasize interpreted Laramide structure. Major feature is broad, block-faulted Laramide
uplift, stepped down by steep faults toward north, and exposing in early Tertiary time a broad area
of Precambrian and lower Paleozoicrocks. The Laramide Florida uplift is southernmost block of the
broad uplift, and the broad uplift itself appears to be a Laramide rejuvenation of the earlier Mesozoic
Burro uplift. Evidencefor strike slip along boundary faults is discussedin text. A-strike-slip movement
away from viewer, T-strike-slip movement toward viewer. SeeFig. 10for interpreted arealdistribution of
uplifts and basins and see Fig. 1 for location of cross section.
and Hatchet Gap. The Upper Cretaceour
lower Tertiary Ringbone formation of the Little Hatchet Mountains may be interpreted as
a molasse deposit (- 2 km [7,000 ft] thick)
derived from the Big Hatchet block (G.
Mack, personal communication, 1983).
Thrust faults in the Little Hatchet Mountains
support previous interpretations of overthrusting (Corbitt and Woodward, 1973),but
may also be interpreted as products of local
compressionor transpressionadjacent to the
major oblique-slip reverse faults at Granite
Pass and Hatchet Gap. The situation here
may be analogous to the low-angle faults
adjacent to the Florida Mountains obliqueslip upthrust, with the exception that the
Florida Mountains faults have undergone a
deeperlevel of erosion and indicate transtension aswell astranspressioncausedbv strikeslip motion on the nearby upthrust.
secondaryeffect adjacent to the major steep
faults (Thompson, 1982). Drewes (1.978,
1982b)and Drewes and Thorman (1980a,b)
also have inferred strike slip on northwesttrending faults in southwest New Meico
and southeast Arizona, but they proposed
left-lateral rather than right-lateral movement.
The predominantly vertical or oblique-slip
wrench movement of basement blocks described in this article are viewed as a consequenceof regional compression.Chapin
and Cather (1981)review evidence for eastnortheastcompressionin early Laramide time
(Late CretaceouFlate Paleocene)and northeast compression in late Laramide time (latest Paleocene-middleEocene)in New Mefco.
The predominantly west-northwest trend of
major uplift margins near Las Cruces suggeststhato I (greatestprinciplestress)was oriented more nearly north-northeast in that
Discussion and summary
area, a direction closer to the late Laramide
In summary, the chief mode of Laramide than to the early Laramide directions of
deformation of the foreland area of south- Chapin and Cather (1981).In fact, little evicentral New Mexico was uplift of relativelv dence can be found to define the early Larsimple northwest to west-northwest-trend- amide direction of compression in southingbasementblockssimilar in stylebut smaller centralNew Mexico.
in scale than some of those of the central
Similarlv. little evidence exists from the
Rocky Mountains. Most uplifts are asym- central Cibalo Mountains southward for a
metric, with steep, reverse-faultednortheast zone of rightJateral shearing, following the
margins, and broad, less-deformedsouthern Rio Grande, which Chapin and Cather (1981)
flanks, which plunge into complimentary suggestmay haveaccommodatednorthward
basins filled with lower Tertiary clastic rocks crowding of the Colorado Plateau relative to
1-3 km (3,000-10,000
ft) thick (rig. rO;. rne the Great Plains. Farther north in New Mexgeneral style of deformation appears to ex- ico, Chapin and Cather (1981)make a contend into the northern margin of terrane pre- vincing casefor its etstence. Laramidebasins
viously regarded as part of the Cordilleran south of the Caballos are viewed as Wind
"overthrust" belt. In this latter region sig- River fypes, resulting from compression,not
nificantright-lateral strike slip, aswell as ma- EchoPark types resulting from a north-south
jor vertical uplift, appears to distinguish couple as suggested by Chapin and Cather
marginal upthrusts. Thus, the uplifts in this (1981)for the Cutter Basin(our southernJorarea may be partly the result of convergent nada Basin of Fig. 10).
w r e n c h i n g ( t r a n s p r e s s i o n ;W i l c o x a n d
Nevertheless, significant right-slip on
others, 1973;Reading, 1980),and the widely northwest-trending upthrusts does seem to
described complex thrust faulting may be a be an important component of the tectonic
November 1983 New Mexim Geology
picfure in southwest New Mexico, and basins exhibiting features of both Echo Park
and Wind River types may be expected. Although it is beyond the scope of this paper
to evaluate the origin of strike-slip in depth,
three possible causesmight be considered:
1) If late Laramide o, in southem New
Mexico was oriented north-northeast, any northwest-trending steep
fault, suchas the south Florida Mountains fault, should exhibit a component of right-slip movement;
2) Perhaps, south of the Caballo range,
Chapin and Cather's (1981) northtrending right-lateral couple was dishibuted as right-oblique slip on some
of the northwest-trending upthrusts
of the region, such as the south Florida and Hatchet Gap faults;
3) Oblique convergence of the Farallon
and North American plates in late
Laramide time may have caused
strike slip on faults in the foreland
area of southern New Mexico. In
general, however, the northwesttrending uplifts of south-central and
southwest New Mexico are nearly
orthogonal to the Farallon-North
American Laramide plate convergence (Coney, 1976, 1978;Dickinson
and Snyder, 1978), which suggests
wrenching on northwest-trending
faults should be subordinate to vertical component of slip.
RightJateral motion of small displacement
also is indicated by the series of "buckles"
on the Pecos Slope (Kelley, 1971).They are
orthogonal to the trend of basement uplifts
of south-central New Mexico (Fig. 10) and
may be interpreted as tears separating domainsof north-northeastcompression,basement uplifts, and crustal short-eningin southcentral New Mexico from unshortened crust
in southeastNew Mexico (C. E. Chapin, personalcommunication,1983).Similartearsmav
extend as far west as the TularosaBasin, a!
little evidence for major Laramide compression has been reported from the Sacramento-Hueco Mountain-Otero Mesa area (C.
E. Chapin, personalcommunication, 1983).
Besides describing the style of Laramide
structures in south-central New Mexico, the
main purpose of this paper is to point out
that some structures in southwest New Mexico, previously regarded as examples of regional overthrusts, also may be interpreted
as products of block uplift on steep to moderately dipping reversefaults, some of which
display evidence for important strike-slip
movement coupled with vertical movement.
Somesmaller scalefolds, thrusts, and normal
faults in the footwall of the major uplifts may
be the product of compression,transtension,
or transpressioncaused by northeastward
crowding of the uplifts combined with important right{ateral slip. These new interpretations have an obvious importance for
the searchfor petroleum in southwest New
Mexicobasins.
Litl\e
|r'*K
/.1
Loromidez
:
H o ' ic h e i
Mls'
w r e n c h f o u l l z o n e o f C h o p i no n d C o l h e r ( 1 9 8 1 )
Colorodo
Ploleou
-u'suu
ll
'/ll/ z/
'i,
.'*..,r
--r.aa$,
,,:",:^fl*$iY u".*'f
-
,
uglifi boun&ry
foull 2one
O
lni
O
l.Glm
ll
"''"-,1,2"*l..-X";,1
s ';e uDt.
ri9hl -lot€rol
6trik. -
Seville Tridenl
o Los Cruces
vts
-0,+ | j'oon
G r i m m; n d o t h e r N
s o ,M
l o b i3l 2
Fronklin i\4ts,
Mis
b
Hotche\
o
Mexico
Ri cd
FIGURE 8-Geologic map of Granite PasFHatchet
Gap area between Little and Big Hatchet Mountains (after Zeller, 1970,1975).Tg-Tertiary granite,
K{retaceous rocks, Pu-upper Paleozoicrocks, Pllower Paleozoicrock, and pCg-Precambrian granite.
D/irt
uiuir
o
5O km
l'>l{.Erosionio Precombrion in
'-''Lordmide
lime
:::,:Loromide bosins
FIGURE 10-Interpretive paleotectonic map of southwest New Mexico in Laramide time showing
inferred pattern of west-northwest-trending Wind River, as well as mixed Wind River-Echo Park(?)type basins, and southwest-dipping, northeast-facing,basement-coredblock uplifts (uplifts locally have
southwest-facingthrust margins, as in the Big Hatchet Mountains). Uplifts in southwest New Mexico
exhibit important oblique right slip and associatedtranspressionalstructures on boundary faults. Control for uplifts and basins is from cross sections and wells indicated on map, as well as from nature of
outcropping pre-rniddle Tertiary rocks in mountain ranges beyond these sections (Fig. 1). Laramide
uplifts were inferred in modern mountain rangeswhere pre-late Eoceneerosion cut deeplyinto Paleozoic
rocks, or locally into the Precambrian rocks; Laramide basins were inferred where nearly complete
sectionsol Paleozoicand Mesozoic rocks are still present today, andlor where thick Upper Cretaceouslower Tertiary basin-filling rocks are known. Nevertheless, diagram is highly speculative in that data
points are few and widely separated (see Fig. 1). General northwest trend of structures is based on
trend of exposeduplift boundary faults. Inset in upper left suggestsPecos"buckles" are tears separating
compressedand shortened crust of southwest New Mexico from uncompressedand unshortened crust
of southeastNew Mexico.
BiS Hotchet Mts.
Bor ridge
Little Hotchet Mts.
Gronite
of fset
section Hotc het Po9s/ offset..
-jejrgl
of f s e i
s e c li o n
Gop
\Pu
\--
/\
N
elev.(ft)
| ry/
5poo
K
Pu
n\Jmerous intrutiult
:59OO
-lopoo
l-
r
Jp€
r5.ooo
JIGURE 9-Diagrammatic section through the Little Hatchet-Big Hatchet Mountains (seeFig. L for location and note offsets of section). Big Hatchet
Mountains,are interpreted as basement-coredblock uplift, the Little Hatchets as compressedblock (transpression?)in front of marginal oblique-slip
reversefaults. Tg-Tertiary granite, K-Cretaceous rocks, Pu-upper Paleozoicrocks, Pl-lower Paleozoicrocks, and p€-Precambrian rolts, A-strike-slip
movement away from viewer, T-strike-slip movement toward viewer
I:>
New Mexico Geolo3y November 1983
of Economic Paleontologists and Mineralogists, Perrnian Basin Section, PublicationT0-12, pp. 55-69.
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Suwey, ProfessionalPaper 658-8, 42pp.
Brown, C. 4.,1982, Geology of the Mahoney mine-Gym
Kelley, V C., 1955,Monoclines of the Colorado Plateau:
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804.
-,
Brown, G. A., and Clemons, R. E., 1983,Florida Moun7971,Geology of the Pecoscountry, southeastern
tairo section of southwest New Mexico overthrust beltNew Mexico: New Mexico Bureau of Mines and Mineral
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Kelley,V. C., and McCleary, J. T., 1960,Laramide orogeny
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Sierra County, New Mexico: M.S. thesis, University of
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Kelley, V. C., and Silver, C., 1952,Geology of the Caballo
Chapin, C. E., and Cather, S. M., 1981,Eocenetectonics
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(eds.), Relations of tectonics to ore deposits in the
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-,
v. 74, pp. 773-798.
1960, Summary of Pennsylvanian sections in
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66,787pp.
-,7963,
l:24,000.
Paleozoicand Mesozoic strata of southwest
-,
Geology of the South Peak quadrangle, Luna
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Mines and Mineral Resources,Bulletin 79,l0O pp.
and Mineral Resources,GeologicMap 59, scale1:24,0N, -,
1965, Sedimentary basins of south-central and
ln Dress.
southwestem New Mexico: American Association of
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Petroleum Geologists, Bulletin, v. 49, pp.2,1202,1,39.
quadrangle, Luna County, New Mexico: New Mexico Kottlowski, F. E., Flower, R. H., Thompson, M. L., and
Bureau of Mines and Mineral Resources,Geologic Map
Foster,R. W.,
Foster,
W., 1956,
1956,Stratigraphic
studies of the San
Stratigraphicstudies
58, scale 1,:24,000,
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Coney, P J.,1975, Plate tectonics and the Laramide oroof Mines and Mineral Resources,Memoir 1, 132 pp.
geny; in Woodward, L. A. and Northrop, S. A. (eds.), Lemley, I. S., 1982,The Lobo Formation and lithologically
Tectonicsand mineral resourcesof southwestern North
similar units in Luna and southwestern Dofia Ana
America: New Mexico GeologicalSociety,SpecialPubCounties, New Mexico: M.S. thesis, New Medco State
lication 6, pp. 5-10.
University, 95 pp.
-,
7978,The plate tectonic setting of southeastern Loring, A. K., and Loring, R. 8., 1980, Age of thrust
Arizona: New Mexico Geological Society, Guidebook
faulting, Little Hatchet Mountains, southwestern New
to 29th field conference, pp.285290.
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Corbitt, L. L., andWoodward, L. A., 1973,Tectonicframe- Reading, H. G., 1980,Characteristicsand recognition of
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Publication 4, pp. 7-26.
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Seager,W. R., 7975, Cenozoic tectonic evolution of the
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-/
Laramidefolding associatedwith basementblock fault1981/Geologyof the Organ Mountains and southing in the western United States:GeologicalSociety of
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-,
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Mines and Mineral Resources,Memoir 16, 128 pp.
-,
1970,Geology of the Little Hatchet Mountains,
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-,
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n
pp
L46,23
in
Shortcourse
water-well
design
"Optirnizing the yields of water wells," an intensive two-dav short course, will be offered bv the
Continuing bducation Department of New M'exico
Institute of Mining and Technology in Socorro,
New Mexico.
The coursewill be held November 10-11, 1983,
at Macey ConferenceCenter on the New Mexico
Techcampus.This short coursehas been designed
for water-resourcemanagers, architects, engineers, geologists, and land developers. The
courseoffers an opportunity to update and familiarize topJevel management and key personnel
with methods and materials for optimum production from new or existing water wells.
Instructors for the course include W. K. Summers, president and senior geologist, W. K. Summers & Associates,Inc. of Socorro.Mr. Summers'
firm is active in design of wells and ground-water
resource management ProSrams.Michael D.
Campbell,author of "Water Well Technology" and
B. G. Hammock, authority in preparation of plans,
specifications,and contract management/will add
their areas of exDertiseto the course. One continuing education unit is offered for completion of
the course.
Luncheons, a cocktail party, and Southwestern
barbecueare planned in conjunction with the short
course,offering participants a chanceto meet and
mingle with each other. The costs of the social
functions are in addition to the course fee.
The course fee is $175.00for those registering
after October 1. Complete information, including
courseoutline/ may be obtained by contacting the
Continuing Education Department, NMIMT,
Campus Station, Socorro,NM 87801,or by calling
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