Marine Terrace Report
Palos Verdes Peninsula, California to Punta Banda, Baja California
September 2013
Prepared for
Southern California Edison
San Onofre Nuclear Generating Station
Seismic Research Project
TABLE OF CONTENTS
Acknowledge ments .................................................................................................................... vii
1.0
Introduction ........................................................................................................................1
2.0
Available Data ....................................................................................................................4
3.0
4.0
2.1
Initial Investigations for Plant Licensing .................................................................4
2.2
Currently Available Data .........................................................................................4
New Terrace Mapping .....................................................................................................16
3.1
Introduction ...........................................................................................................16
3.2
Field Mapping Methodology, Uncertainties and Reference Frames ....................17
3.3
Mapping on Camp Pendleton ................................................................................21
3.4
Data Collection North of Camp Pendleton ...........................................................24
3.5
Field Mapping of Marine Terraces North of SONGS in the Spring of 2013 ........25
3.6
Summary of New Results .....................................................................................36
Summary of New Data Collection ..................................................................................39
4.1
Summary of Terrace Observations .......................................................................41
5.0
Plausible Interpretation of Terrace Data Based on Published and New Data ...........44
6.0
References .........................................................................................................................54
List of Tables
1
GPS parameter settings used for this study
2
Dates of potential map editions used in this and previous studies
3
Average elevations of terraces mapped on Camp Pendleton
List of Figures
1
Illustration of location and geometry of estimated locked (earthquake generating) portion
of the OBT relative to SONGS.
2
Aerial extent of first emergent marine terrace with associated shoreline angle elevations:
Dana Point to Las Pulgas Canyon, modified from Shlemon (1979).
3
Diagram of modern and paleo marine terraces and associated features.
4
Aerial extent of reference and data collection effort, Palos Verdes Peninsula to Punta
Banda.
5
Locations where shoreline angles have been noted in the literature.
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6
Shoreline angle data compiled from all known measurements of uplifted marine terraces
along the coastline from Punta Banda Mexico to the Palos Verdes Peninsula in
California.
7
Plot of many of the most relevant marine terrace fossil localities in Los Angeles, Orange,
and San Diego counties for which there are locality and faunal data.
8
Plot of localities where the presence of coral has been listed.
9
Example of a shaded relief map (hillshade image created from a digital elevation model
[DEM]) of the San Joaquin Hills area derived from archival topographic maps made
before extensive urbanization modified the ground surface with marine terrace extents
overlain.
10
Oblique aerial photograph (by John Shelton, published in Ross and Dowlen, 1975),
showing the pristine coast between SONGS and Oceanside.
11
Exposed contact between the eroded marine abrasion platform and overlying marine
gravels.
12
Control Point 3159 on Camp Pendleton.
13
Modern shoreline angle (SLA) exposed about 1 km southeast of SONGS on San Onofre
State Beach.
14
Modern gravelly beach berm on Camp Pendleton north of Horno Canyon near Warrior
Cove.
15
Oblique aerial photograph (cropped from Figure 10) showing the three sets of terraces we
mapped in this study.
16
Alluvial fan deposits burying the lower terrace set.
17
Example of paleo-shoreline where the actual shoreline angle is buried and we estimate its
elevation.
18
Exposures of oblate spheroid pebbles and cobbles, interpreted as of marine origin.
19
Boreholes in rocks and abrasion platforms interpreted to have been made by rock-boring
clams in the family Pholadidae.
20
The 285 m shoreline exposed in the road cut along San Onofre Peak Road.
21
Shoreline deposits of the first emergent terrace in San Clemente 0.5 km south of the San
Clemente Pier at 8.7 m elevation
22
Paleo-beach exposure of the first emergent terrace, Avenida Calafia, San Clemente State
Beach, at 12.1 m elevation
23
Shoreline angle exposure of the 2nd emergent terrace at the Marblehead development.
24
Paleo-shoreline for the 3rd emergent marine platform exposed along Cristianitos Road in
southernmost San Clemente.
25
Exposure of fossiliferous marine sand and gravel associated with the 4th emergent terrace
at the Marblehead development.
26
Exposure of the terrace fore-edge at 31.2 m at Dana Point.
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27
Exposure of the first emergent terrace at Dana Point
28
Exposure of the fore-edge of a marine terrace at 38.5 m elevation on the north side of
The Street of the Copper Lantern in Dana Point.
29
Inferred location of the shoreline angle for the marine terrace exposed in Figure 28.
30
The ~34 m terrace is the first emergent marine terrace in the Dana Point area, but lower
terraces are preserved both to the north and south of Dana Point.
31
Shoreline angle of the first emergent terrace at the Montage Resort, as exposed adjacent
to a wheel chair ramp, surveyed at 8.5 m elevation.
32
Second emergent terrace in the Laguna Beach area, as viewed from Aliso Beach parking
lot.
33
Fore-edge of the ~21 m terrace exposed in a nature trail on the east side of Pacific Coast
Highway across from Aliso Beach.
34
Fore-edge of a marine abrasion platform exposed along Brooks Street
35
Exposure at Crystal Cove State Park, with well sorted fine sand interpreted to be of
littoral origin interfingering with bedded, clast-supported angular gravel of fluvial origin.
36
Shoreline gravels and paleo-sea cliff of the first emergent terrace at Newport Beach.
37
Estuarine terrace inset into the 3rd terrace on the north side of Upper Newport Bay below
Galaxy View Park.
38
Map with platform elevations derived from geotechnical borehole data.
39
Examples of spotty preservation of low terraces in La Jolla.
40
Surveyed shoreline angle elevations with uncertainties, as measured along the coast
southeast from SONGS.
41
Surveyed shoreline elevations for the lowest four emergent terraces north of SONGS to
Newport Beach.
42
Predicted elevation of terraces based on repeated rupture of the OBT.
43
Cross-sections (locations on Figure 38) showing the platform elevations determined from
geotechnical boring data.
44
Cross-section across Upper Newport Bay.
List of Appendices
I
Bibliography on Pleistocene Paleontology, Marine Terraces and Quaternary Dating
Methodologies, Palos Verdes Peninsula to Punta Banda, Baja California.
II
Guidebooks and edited volumes with numerous contributions by other authors.
III
Bibliography, Geologic Maps of the Coastal Zone, Palos Verdes to Punta Banda.
IV
References identifying scanned and uploaded to database, those used in the fossil locality
and/or shoreline angle compilation, type, and annotations.
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V
Locality datasheets from the Natural History Museum of Los Angeles County for the
Palos Verdes Sand.
VI
Locality datasheets from the Natural History Museum of Los Angeles County for the
Palos Verdes Hills Area.
VII
Locality datasheets from the Natural History Museum of Los Angeles County for the
Orange County area.
VIII
Locality datasheets from the Natural History Museum of Los Angeles County for the San
Diego County area.
IX
Locality datasheets from the Natural History Museum of Los Angeles County for the
northern Baja California area.
X
Summary of SDSC/SDSU Pleistocene fossil localities.
XI
Locality datasheets and maps for USGS localities and collections, now housed at the
University of California Museum of Paleontology (UCMP, Berkeley).
XIIa
Fossil Locality Data
XIIb
Dated Locality Data
XIIc
Shoreline Angle Data
XIIIa Raw GPS Data
XIIIb Field season notes, July – November, 2012 and December 2012 – May 2013
XIIIc Map of Marine Corps Base Camp Joseph H. Pendleton, San Diego County, California
showing location of training areas cited in field notes [Appendix XIIIb]
XIIId Profiles of transects and location map
XIV
Paleontology of Pleistocene Marine Fossil Localities between San Onofre State Beach
and Horno Canyon, Marine Corps Base Camp Joseph H. Pendleton, San Diego County,
California
XV
Paleontology of Pleistocene Marine Fossil Localities between, San Clemente State Beach
and Newport Beach, Orange County, California
XVI
J. P. Kern’s Unpublished Marine Terrace Maps
XVII Geotechnical Boring Logs and Reports Obtained from Local Agencies and Consultants
XVIII Cosmogenic Isotopes and Uranium- Thorium Laboratory Data
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Glossary of Te rms and Acronyms
fault-bend folding: bending of fault blocks as they ride over non-planar fault surfaces; a
mechanism associated with steps in decollement in fold-and-thrust belts, reverse-drag or
rollovers in normal faults that flatten with depth, and flower structures in bends in strikeslip faults (Suppe, 1983).
first eme rgent platform: first bench or geomorphic surface above present-day sea level, not
necessarily identical in age to the first bench observed elsewhere along the same coast
(Shlemon, 1978 a); syn. first marine terrace (Bradley and Addicott, 1968).
marine abrasion platform: an extensive, gently sloping intertidal surface produced by marine
erosion or denudation at or near wave base (Johnson, 1916); syn. a wave-cut platform
(Neuendorf et al., 2005).
shoreline angle (SLA): the intersection between the marine abrasion platform and the paleo-sea
cliff, also termed the terrace back edge. The shoreline angle is essentially a horizontal
datum that can be used to measure vertical and horizontal movements due to folding or
faulting.
wre nch-fault: rupture in the earth’s crust in which the dominant relative motion of one block to
the other is horizontal and the fault plane is essentially vertical; syn. lateral fault, strikeslip fault (Moody and Hill, 1956).
ACRONYMS:
AAR:
BFSA:
CD:
CFM3:
CI:
CIT:
cm:
CRN:
DEM:
DLG:
DMA:
ECI:
GIS:
GP:
GPS:
ka:
km:
LACMNH:
LNG:
m:
M:
Ma:
Amino acid racemization
Brian F. Smith and Associates, Inc., Poway
Compact disk
Community Fault Model, Version 3
Contour interval
California Institute of Technology (Cal Tech), Pasadena
centimeter(s)
Cosmogenic radio nuclides
Digital elevation model
Digital line graph
Defense Mapping Agency-Global Reference Model
Earth Consultants International, Inc., Santa Ana
Global Information System
General point (see data in Appendix XIIIa)
Global Positioning System
kilo anno, 1,000 years
kilometer(s)
Natural History Museum of Los Angeles County, Los Angeles
Liquefied natural gas
meter(s)
Earthquake magnitude
Million years
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MIS:
MLLW:
MSL:
NAD 27:
NAD 83:
NAVD 88:
NGVD 29:
NOAA:
NGS:
NI/RC:
NOS:
OBT:
OSU:
PDF:
PI:
PR:
PSHA:
SCE:
SDG&E:
SDNHM:
SDSC:
SDSU:
SIO:
SLA:
SONGS:
SSHAC:
SSC:
UCERF2:
UCI:
UCLA:
UCMP:
UCSD:
UO:
USDA:
USGS:
UTM:
WGS 84:
Marine (oxygen) Isotope Stage
Mean lower low water
Mean sea level
North American Datum of 1927
North American Datum of 1983
North American Vertical Datum of 1988
National Geodetic Vertical Datum of 1929
National Oceanographic and Atmospheric Administration
National Geodetic Survey
Newport-Inglewood/Rose Canyon fault system
National Ocean Service
Oceanside blind thrust fault
Oregon State University, Corvallis
Portable Document Format
Photoinspected (quadrangle maps)
Photorevised (quadrangle maps)
Probabilistic Seismic Hazard Assessment
Southern California Edison Company
San Diego Gas & Electric Company
San Diego Natural History Museum
San Diego State College
San Diego State University
Scripps Institution of Oceanography, La Jolla
Shoreline angle
San Onofre Nuclear Generating Station
Seismic Source Hazard Assessment Committee
Seismic Source Characterization
Uniform California Earthquake Rupture Forecast 2
University of California, Irvine
University of California, Los Angeles
University of California Museum of Paleontology, Berkeley
University of California, San Diego
University of Oregon, Eugene
U. S. Department of Agriculture
U. S. Geological Survey
Universal Transverse Mercator grid system
World Geodetic System of 1984
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ACKNOWLEDGEMENTS
The planning, field and office work completed to prepare this research document was done by a
team of geologists, geomorphologists, paleoseismologists, paleontologists, and pedologists who
have focused their careers on the fault and seismic hazards in southern California, particularly
along the coast. The team was led by Dr. Thomas K. Rockwell from San Diego State University
and Dr. George L. Kennedy from Brian F. Smith and Associates, Inc. The team included Dr. Lisa
Grant Ludwig from the University of California at Irvine, and Dr. Karl J. Mueller from the
University of Colorado. This team’s technical support was provided by Mr. Justin A. Zumbro
from GeoPentech, Inc., and Ms. Danielle Verdugo, Ms. Tania Gonzalez and Mr. Erik C. Haaker
from Earth Consultants International, Inc. Mr. Craig G. Wolfgram, Range and Training Area
Management Division at the United States Marine Corps Base Camp Joseph H. Pendleton in
northern San Diego County (hereafter, Camp Pendleton), was particularly helpful in facilitating
field work on the Base during the 2012 and 2013 field seasons.
The team was assembled and coordinated by Mr. S. Thomas Freeman and Mr. Justin A. Zumbro
of GeoPentech, Inc., who also served as the report’s editors.
Initial planning reviews were provided by Ms. Kathryn L. Hanson from AMEC Geomatrix, Dr.
James F. Dolan from the University of Southern California, and Dr. Daniel J. Ponti from the U.S.
Geological Survey. Dr. Roy J. Shlemon of Roy J. Shlemon & Associates, Inc. provided both
planning and field reviews.
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Marine Terrace Data Report,
Palos Verdes Peninsula, California to Punta Banda, Baja California
1.0
INTRODUCTION
Marine terraces provide information on the relative and absolute uplift rates of coastlines, and
can be a source of critical data in the assessment of tectonic models and models of fault activity
where these geologic structures cross the coastal zone of the Southern California Continental
Borderland. The San Onofre Nuclear Generating Station (SONGS) lies on the lowest local
emergent marine terrace along the coast in northernmost San Diego County, California. Thus,
quantification of marine terrace ages and elevations near SONGS will provide direct control on
the viability of alternative models of tectonic structures near SONGS and their rates of
emergence and/or deformation.
The offshore segment of the sub- vertically dipping, strike-slip Newport-Inglewood/Rose Canyon
(NI/RC) fault zone was shown to be the closest primary active fault to the plant during the
geological investigations completed for the design and initial licensing of Units 2 and 3 in the
1970s and early 1980s (Southern California Edison, 1990). Recent interpretations (Rivero et al.,
2000; Rivero, 2004; Shaw and Plesch, 2010; Rivero and Shaw, 2011) of historical proprietary
petroleum industry offshore marine geophysical surveys have suggested that shallowly dipping
blind thrust faults may be actively accommodating crustal shortening in southern California’s
Continental Borderland and coastal zone. Furthermore, one of these thrust faults, the Oceanside
Blind Thrust fault (OBT), has been proposed to underlie the southern California coast from the
Mexican border northward to at least Dana Point in Orange County, which includes the vicinity
of the power plant itself. The OBT fault model places an easterly dipping thrust fault directly
under the plant, potentially making the OBT the closest primary active fault, rather than the
NI/RC. Figure 1 shows the simplified geometry of the OBT model implemented in GeoPentech’s
(2010) PSHA. An additional fault named the San Joaquin Hills blind thrust has been proposed to
exist from Dana Point northward to Seal Beach (Grant et al., 1999). Although submerged marine
terraces exist offshore from SONGS, the terrace deposits on them lack any age control and were
not studied further.
The pattern of coastal uplift or subsidence rates, as expressed by the ages and elevations of the
marine terraces along the southern California coast can be used as indicators as to whether or not
the coastal uplift and subsidence over the last 120,000 years is due to either seismic or aseismic
processes. These include deformation caused by one or more of the following:
1. Localized subsidence or uplift due to thrust faults that formed during the initiation of
steeply dipping strike-slip faults such as the Newport-Inglewood fault zone;
2. Coastal uplift associated with long term permanent deformation or short term
interseismic strain accumulation due to blind thrust faults, such as the proposed
Oceanside and San Joaquin Hills blind thrust faults;
3. Regional-scale uplift related to rift- flank uplift of the Peninsular Ranges;
4. Localized subsidence due to sediment compaction or groundwater extraction.
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Figure 1. Illustration of location and geometry of estimated locked (earthquake-generating) portion (in
yellow) of the OBT relative to SONGS.
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Figure 1 shows the approximate aerial and subsurface extent of the estimated locked
(earthquake-generating) portion of the proposed OBT fault. In this model, the western yellow
line on the plan view map (Figure 1) represents a fault depth of 0 km (fault plane projection to
the ocean floor), and the eastern yellow line represents a fault depth of 17 km. The inferred fault
plane lies approximately 7 km below SONGS. The 17 km depth, as evaluated by Rivero et al.
(2000) and Rivero and Shaw (2011), corresponds with the assumed base of regional seismicity in
southern California’s Inner Continental Borderlands. Our understanding is that the hypothesized
fault projects to greater depths (20 to 25 km); however, the magnitude and frequency of
earthquakes below 17 km is low. In UCERF2, [2007 Working Group on California Earthquake
Probabilities (WGCEP), 2008, Appendix A, table 2, titled “Faults being considered for
development"], the geometry of the OBT is modeled a little differently, with the locked portion
of the OBT estimated to lie between about 1 and 8 km beneath the surface. Alternative models of
OBT geometry to greater depths have not been espoused, so in terms of model comparisons with
coastal uplift rates, it is probably best to extrapolate the OBT model below 17 km at a constant
dip.
The OBT fault model has been divided by Rivero et al. (2000), and Rivero and Shaw (2011) into
a northern and a southern segment. Based on the data set from the Community Fault Model
constructed by Plesch et al. (2007), the northern segment of the OBT fault plane has an average
dip of approximately 22 degrees, with dips ranging from 20 to 26 degrees. The southern fault
segment has an average dip of approximately 24 degrees, with dips ranging from 20 to 30
degrees. The latest slip rate estimates for the OBT utilized in the GeoPentech (2010) PSHA
ranged between 0.70 mm/yr. and 1.94 mm/yr. Based on the inferred geometry, this converts to a
vertical slip rate component of 0.26 mm/yr on the northern segment and 0.48 mm/yr. on the
southern segment.
If the OBT fault were to exist under the coastline with the segmentation, different dip angles, and
slip rates as presented by Rivero et al. (2000), Rivero (2004), Plesch et al. (2007) and Rivero and
Shaw (2011), one would expect extensive deformation of the coastal terrain and marine terraces
above the fault plane, especially considering the millions of years that the OBT is estimated by
Rivero et al. (2000), and Rivero and Shaw (2011) to have been active. This scenario would have
left an extensive record of deformation of the uplifted marine terraces found along the coast.
Thus, understanding the pattern and rate of coastal uplift and deformation, as expressed by the
topography/elevations, and ages of the elevated marine terraces along the Orange and San Diego
County coasts, will provide critical data with which to assess this potential seismic hazard to
SONGS. The results of these coastal studies are also important in updating and refining slip rate
and rupture patterns tied to the strike-slip NI/RC primary fault model.
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2.0
AVAILABLE DATA
2.1
Initial Investigations for Plant Licensing
Early work conducted by SCE several decades ago on the ages, elevations, and deformation of
marine terraces along the coast in the vicinity of SONGS (Figure 2) demonstrated that the
Cristianitos fault did not cut the gravels deposited on top of the wave-cut platform of the
emergent marine terrace on which the plant is situated (Shlemon, 1978a). However, these data
are not well constrained by today’s standards in terms of either the ages or the precise elevations
of the variously preserved terraces and shoreline angles (SLA; the intersection between the
marine abrasion platform and the paleo-sea cliff, also termed the terrace back edge). The
shoreline angle is essentially a horizontal datum that can be used to measure vertical movements
(Figure 3). This is particularly important when using the terrace data as a means to assess the
Quaternary deformation characteristics of more regionally extensive Continental Borderland
faults in southern California, such as the proposed OBT. Hence there is a strong need to update
and refine our knowledge of marine terraces in the vicinity of SONGS. Doing so first required a
thorough assessment of the currently available marine terrace data that have been collected by
others since SCE’s initial efforts in the 1970s (see appendices).
2.2
Curre ntly Available Data
The following data compilation (herein and attached, see Appendices I–XVII) provides a basis
by which to assess the current state of knowledge on marine terrace ages and elevations from the
Palos Verdes Peninsula in the Los Angeles Basin southward to Punta Banda in northern Baja
California (Figure 4), and to identify relevant data gaps that needed to be filled in order to better
assess the various alternative tectonic models that may control the seismic hazards at SONGS.
The scope and aerial extent of the compilation of terrace and elevation data were based on the
need to provide a sufficiently broad background against which to test various tectonic models of
coastal deformation. Possible models for coastal deformation and uplift include: 1) regional farfield rift flank uplift; 2) uplift associated with local wrench- fault thrust mechanisms within an
active primary strike-slip fault system; 3) uplift associated with fault propagation or fault-bend
folding accompanying an active primary blind thrust system, or 4) a mix of these processes. The
purpose of this compilation was to provide as complete a data resource as possible to help guide
studies on the style and rate of uplift of the coastal terrain and marine terraces in the vicinity of
the San Onofre Nuclear Generating Station.
Characterizing late Quaternary strain caused by active faulting along the coastal plain between
San Diego and Los Angeles is challenging for several reasons. First, the uplift signal from
gently dipping faults such as the OBT is small (on the order of tens of meters over a period of a
hundred thousand years). This subtle deformation must be distinguished from uplift caused by
regional rift flank uplift, as described by Mueller et al. (2009) for the Baja California and
southern California areas. Rift flank uplift models, such as those described by Kier and Mueller
(1999) and Mueller et al. (2009), have been discussed in SONGS pre-Seismic Source Hazard
Assessment Committee (SSHAC) and SSHAC meetings. The SONGS Seismic Source Topical
Meeting in August 2011, although focused on data, included some discussions by T. K.
Rockwell and K. J. Mueller on rift flank uplift models. More recently, the SONGS Seismic
Source Characterization (SSC) SSHAC Workshop #1 in January 2013, which was also focused
on data, included a brief mention of the model in Rockwell’s presentation; however, since that
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workshop was focused exclusively on data rather than models, more detailed discussions were
not facilitated.
Discussion of uplift as reflected in the coastal marine terraces and possible implications toward
the mechanism of tectonic deformation were discussed during the 2013 SONGS SSC SSHAC
Workshop #2. In addition, data from key areas where recent deformation might have occurred,
but which have been obscured or destroyed by urbanization and development, such as at Dana
Point, where the San Joaquin Hills Blind Thrust is likely to terminate, and in San Clemente
closer to SONGS, where rift flank uplift may decrease relative to its consistent magnitude farther
south, were presented.
Before the 2012 and 2013 field seasons it was difficult to gain access to terraces on portions of
Camp Pendleton. Access issues were partially circumvented using remote data, including
historical aerial photographs and topographic maps. However, due to the value of the resulting
data to the United States Marine Corps., Staff on the base made commendable efforts to facilitate
access for the terrace mapping team.
Additionally, geotechnical reports and boring log data were collected from local city agencies
and geotechnical consultants to further aid in analysis of areas that are now developed or
inaccessible, in order to better define the paleo-shorelines inland of the current coastline.
Finally, uranium-series and cosmogenic nuclide dating programs were implemented on selected
samples by the University of Minnesota and Purdue University, respectively.
2.2.1
General Bibliography
The current research effort involved the collection of every reference we could find about the
locations and ages of Pleistocene marine terraces, the extent and elevations of exposed marine
abrasion platforms, marine terrace and correlative estuarine fossil localities, other Pleistocene
marine terrace dating methods, and other relevant data that may bear on uplift rates or tectonic
deformation rates that could potentially be applied to terrace deposits between the Palos Verdes
Peninsula and Punta Banda. We built upon the original compilation of approximately 50 relevant
published references in SCE’s original database by incorporating extensive additional published
material, as well as data from unpublished sources or gray literature, including but not limited to,
consulting reports, abstracts, field trip guidebooks, unpublished maps, and fossil locality data
sheets (Appendices I, II, and III).
Collection of these references required visits to the libraries at the University of California at Los
Angeles (UCLA), the University of California at San Diego (UCSD), Scripps Institution of
Oceanography (SIO), San Diego State University (SDSU), Oregon State University (OSU), the
San Diego Natural History Museum (SDNHM), and the Natural History Museum of Los Angeles
County (LACMNH), as well as meetings with individuals with extensive private libraries or
collections.
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Figure 2. Approximate aerial extent of the “first emergent marine terrace” with associated shoreline angle elevations: Dana Point
to Las Pulgas Canyon, as interpreted by Shlemon (1979). New marine terrace mapping in 2012 and 2013 has extended this both to
the south, through Camp Pendleton to Oceanside, as well as to the northwest, to Newport Beach.
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Figure 3. Diagram of modern and paleo marine terraces and associated features.
Figure 4. Aerial extent of reference and data collection effort, Palos Verdes Peninsula to Punta
Banda.
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In total, there are 616 literature citations listed in Appendix I. Many of these citations were
derived from citations contained in guidebooks and edited volumes; these sources are listed
separately in Appendix II. Appendix III is a bibliography of published geologic maps of the
coastal zone from the Palos Verdes Peninsula, to Punta Banda in northern Baja California. Some
references in Appendix III are also listed in the main bibliography of Appendix I.
Given the amount of information found, and because of time and budget constraints, we needed
to prioritize our scanning and database updating efforts to those sources deemed most relevant to
the objectives of the study at this time. Appendix IV is a spreadsheet that includes all 616
citations listed in Appendix I, and indicates that 69 of these new citations have already been
acquired, scanned into PDF format, and added to SCE’s SONGS digital database. Appendix IV
also indicates whether the citation was used in the terrace data compilation of Appendices XIIa,
XIIb, and XIIc. Information from 27 of the citations contained in Appendix I were used to
compile the terrace data presented in Appendices XIIa, b, and c, but they have not yet been
acquired, scanned and added to SCE’s SONGS digital database.
2.2.2
Fossil Locality and Faunal Data
Critical to any marine terrace study is the ability to accurately date marine terraces. Critical to
the task of dating the terrace ages is the presence of Pleistocene marine invertebrate faunas that
can be collected and directly associated with a specific geologic age, marine abrasion platform or
correlative estuarine deposit. Important sources of marine faunal data include the extensive
paleontological collection records at the LACMNH and the SDNHM, both of which maintain
locality data files for fossils that have been collected over the past century. Faunal lists may
report the presence of species that can provide important information on the zoogeographic
signature (i.e., temperature aspect) of the fauna, which has been successfully used to assign ages
to terraces formed during previous interglacial periods (e.g., Kennedy et al., 1982; Kennedy,
2000), and other aspects that relate to terrace age. Faunal lists are available for most SDNHM
Pleistocene localities, and can be compiled from locality collections at LACMNH (including
those previously at UCLA and California Institute of Technology (Caltech, CIT), SDSU (now at
SDNHM), University of California Museum of Paleontology (UCMP), and the United States
Geological Survey in Menlo Park (USGS, now at UCMP).
2.2.3
Terrace Elevation Data
We reviewed references that contained information on shoreline angle locations and elevations.
A shoreline angle is the intersection between the abrasion platform and the sea cliff. Modern
shoreline angles are typically cut during a combination of high tide and storm surge, so they are
typically at 1 to 3 m above mean sea level (MSL) (Rockwell et al., 1989). Lower shoreline
angles may form in areas of resistant rock, where headlands project out into the water. In these
cases, only the cuspate bays exhibit shoreline angle elevations that are above MSL. Because of
the general horizontality of the position of the shoreline angle along a straight coastline, it
provides an elevation baseline with which to measure uplift over time, and as an indicator of
local (non-regional) terrace deformation.
Paleo-shoreline angles are those associated with uplifted beaches, most of which are of
Pleistocene age. The elevation of these paleo-shorelines is a function of uplift and the position
of paleo-sea level at their times of formation.
September 2013, Rev. 0
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Figure 5 presents an aerial view of all of the localities for which we have shoreline angle
elevation data derived from references in the bibliography. Figure 6 plots the same shoreline
angle elevation data set (from Punta Banda in Baja California to the Palos Verdes Peninsula,
California), with the shoreline angle elevations grouped into various marine isotope stages.
Figure 6 shows that the early SONGS area terrace data (Shlemon, 1978a, 1978b, and 1979)
(green dots on Figure 6) were not well- constrained in terms of marine isotope stages and were
not correlated with terrace data to the north or south of SONGS. Many of the shoreline a ngle
data for SONGS were estimated and/or projected shoreline angles dating from work done in the
late 1970’s that now need clarification in terms of precisely locating shoreline angle locations
and elevations, and identifying the resulting marine isotope stage identification and uplift rates.
In addition, the marine isotope stages denoted on Figure 6 for the areas south of SONGS may not
be entirely accurate and need to be verified. For instance, some of the first emergent terrace data
points may represent either substage 5a or substage 5e terraces, and the substage 5e terrace data
may contain some terraces that may represent Stage 7 or Stage 9; hence the need for the
additional study of the marine terraces.
Figure 5. Locations where shoreline angles have been noted in the literature. The data
from northern Baja California, San Diego County up to Oceanside, and in the San Joaquin
Hills in Orange County all have fairly well resolved elevations, and many are surveyed –
these are shown as yellow pins. The shoreline angle elevations near SONGS are all based
on projections of up to 800 feet, and assume that a mapped shoreline corresponds to the
fore edge of the terrace exposed in the sea cliff (Shlemon, 1978a, b) – these are shown as
dark pink octagons.
The vast majority of the information comes from a few seminal data sets, some of which are
published and others that are not. Unpublished data sources include mapping efforts by Dr. J. P.
Kern (formerly at SDSU) and Dr. L. B. Grant (UCI). Few published studies refer to shoreline
angle elevations, indicating the need for further mapping efforts in order to refine the extent and
timing of local or regional uplift rates based on uplifted marine terrace data.
Marine terrace data, including: 1) geographic information, 2) elevations, 3) inferred ages or
associated U-series, and cosmogenic nuclide dates, and 4) other relevant data from geotechnical
reports and boring log data obtained from local cities and consultants were collected and
digitized and are included in electronic versions in a number of formats in the accompanying
data files. Generally, previously mapped shoreline platforms were considered too imprecise for
incorporation as point data into this compilation. For example, the marine terrace map of
Woodring et al. (1946) for the Palos Verdes Hills provides reasonably good detail as to the
locations of the paleo-shorelines, but contains no surveyed or directly measured elevation data,
and therefore is of limited use without additional work. Therefore, for this project, shoreline
angle data were only incorporated if a specific locality and measured elevation were both
September 2013, Rev. 0
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provided. Furthermore, projected shoreline angle data were generally not incorporated into this
database, as they are too imprecise to test tectonic models. We did include Shlemon’s (1978a, b)
projected elevation estimates, as they focused on terraces around the SONGS facility. At first
glance, the spatial coverage appears excellent, although nearly all of the observations near
SONGS are poorly constrained in terms of the current levels of accuracy in terraces ages,
shoreline angle locations, and elevations. We address this directly in the next section where we
present new, highly constrained (GPS) survey data on terrace elevations.
The data obtained from our literature review are compiled into three groupings: b) localities with
Pleistocene fossils (Appendix XIIa), b) localities that have been dated by U-series methods
(Appendix XIIb), and c) localities with shoreline angle elevations (Appendix XIIc). The
shoreline angle data set lists each locality, its geographic coordinates and its elevation, the data
source, the local terrace name with which the shoreline is associated; the marine oxygen isotope
( 18O) stage number (MIS) to which the authors attributed to each locality, and whether the
elevation is based on a direct survey, an estimate from a topographic base map, or a projection
over some distance from a platform exposure. The fossil locality data set provides the locality
name and description, its geographic coordinates (longitude and latitude), the terrace number that
the locality is inferred to be from, any additional fossil locality designations, whether there are
corals present, the bibliographic reference, and any additional locality description or information.
For the U-series dated fossil localities, and cosmogenic nuclides dated samples, if the data were
available, we also summarized the age determinations and uncertainties, the species of coral or
hydrocoral used (U-series dating) or sediment or rock type (cosmogenic dating) that was
analyzed, and the associated shoreline angle elevation, when known.
As shown on Figures 5 through 8, the San Joaquin Hills contain the densest coverage of fossil
localities, U-series dates, and shoreline elevations in the SONGS region. However, newly
obtained data from marine terraces on Camp Pendleton (Subsection 3.3) provide important
information on shoreline elevations in the vicinity of SONGS (Appendix XIc). The published
uplift rate of the San Joaquin Hills (Grant et al., 1999) was derived from data in the northern San
Joaquin Hills, between Laguna Canyon and Newport Bay. In the southern San Joaquin Hills,
between Laguna Canyon and Dana Point, unpublished mapping a nd preliminary correlation of
terraces/shorelines suggests that the uplift rate or style of deformation differs from the northern
San Joaquin Hills because the sequence of terraces differs. This inferred change in marine terrace
sequence coincides with a change in drainage orientation that might be tectonically controlled.
Shoreline angle elevations in Appendix XIIc also show differences in elevations of northern San
Joaquin Hills strandlines reported by Grant et al. (1999) and projected shoreline elevations in the
southern San Joaquin Hills from Shlemon (1978b). Unpublished mapping and preliminary
correlation of wave-cut notches in paleo-sea cliffs of the San Joaquin Hills also suggest differing
uplift rates, although the evidence is weak due to absence of age control on the notches.
However, there is some evidence that the San Joaquin Hills contain an intermediate shoreline
(substage 5c) in addition to the more widely reported substage 5a and 5e shorelines (Grant et al.,
1999). Finally, new surveyed data collected for this study and presented in Section 3 suggest
that at least the lowest emergent terraces are relatively flat and unfolded from San Clemente
northward to Newport Bay.
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Figure 6. Shoreline angle data and interpretations compiled from references of all previously mapped uplifted marine terraces along
the coastline from Punta Banda, Baja California, Mexico to the Palos Verdes Peninsula in southern California. Note that Grant, et al.
(1999) indicated that the single MIS 5a point in the San Joaquin Hill could alternatively be MIS 5c. This was the starting point for the
new mapping of terraces on Camp Pendleton, and in southern Orange County, as discussed in Section 3.0.
September 2013, Rev. 0
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A complicating feature of the San Joaquin Hills is the presence of relatively steeply dipping
faults that appear to have been active in the Quaternary. These faults locally displace uplifted
marine terraces. For example, the UCI Campus fault in the northern San Joaquin Hills displaces
late Quaternary terraces on the UCI campus. A M3.5 earthquake on September 15, 2011
occurred on the UCI Campus fault, indicating that it is active, and/or intersects the inferred San
Joaquin Hills blind thrust at an approximate depth of 10 to 11 km. The effect of surface faulting
displacement of marine terraces in the northern San Joaquin Hills was not considered by Grant et
al. (1999) in calculating marine terrace uplift rates, and the difference in elevations reported by
them and those collected during this study and presented in Section 3 may be partly explained
by the presence and activity of these faults.
Figure 7. Plot of many of the most relevant marine terrace fossil localities in Los
Angeles, Orange, and San Diego Counties for which there are locality and faunal data.
Note the excellent spatial distribution of fossils along the coastal zone.
The SDNHM has records for over 600 Pleistocene fossil localities, most with appended faunal
data, as well as locality and elevation information. Most of these localities are from coastal San
Diego and Orange Counties, and therefore are directly relevant to SONGS. Their locations have
been incorporated into this project’s digital map database, but the actual locality sheets and
associated faunal lists have not yet been acquired. Appendices V, VI, VII, VIII, and IX are
datasheets for 331 Pleistocene fossil localities from the LACMNH that relate specifically to
SONGS. Appendix V presents data for 85 localities on the 120,000 year-old terrace and
correlative subsurface deposits of the Palos Verdes Sand; Appendix VI lists 31 additional
localities from older terrace localities on the Palos Verdes Hills; Appendix VII lists 89 marine
Pleistocene localities in Orange County; Appendix VIII lists 100 marine Pleistocene localities in
San Diego County; and Appendix IX includes 26 northern Baja California marine Pleistocene
localities. Appendix X includes marine Pleistocene locality data sheets for 134 fossil localities
previously at SDSU and now at the SDNHM. Appendix XI includes locality data sheets for 27
relevant USGS (Menlo Park) marine Pleistocene locality collections now at the UCMP in
Berkeley, along with a locality list for another 543 localities at UCMP, many of which are
relevant for SONGS.
As seen on Figure 7, which shows many of the recorded fossil localities from the LACMNH,
SDNHM and USGS sources, there is generally excellent spatial coverage along the Orange and
San Diego County coasts. Of these, 35 localities (Figure 8) have yielded corals that are suitable
for uranium-series analysis; 12 of the localities have been previously dated and the results
published (see Appendix I and Appendix XIIb); and 30 of the localities have been digitized and
September 2013, Rev. 0
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included in the GIS overlays appended to this report. Three localities in northern San Diego
County that have yielded corals are highly relevant to the SONGS investigation, but had not been
dated during the earlier phases of this project. We were able to acquire corals from five of the
reported localities, including two of the localities in northern San Diego County, and the results
are presented later in this report. Furthermore, the fossil lists for many of the other localities have
not been compiled and analyzed for the presence of corals, so the potential exists that additional
corals may be available to provide additional dates for terraces in the study area.
Figure 8. Plot of localities where the presence of coral has been listed. Dated localities
are shown in red, whereas collected undated coral localities are shown in blue .
2.2.4
Historical Digital Topographic Maps
Georeferenced digital copies of twenty 7.5- minute, USGS topographic quadrangle maps
produced between 1948 and 1953 were obtained and used to create pre-development topographic
maps for the site and surrounding southern California coastline area. These archival maps
provided a way to create digital elevation models (DEMs) by digitizing contour lines and
attributing their elevations. The resulting digital line graphs (DLGs) were then gridded at
various resolutions to produce DEMs. The DEMs were then processed to create shaded relief
maps (e.g., Figure 9) and slope maps that enabled us to identify areas that might be uplifted
above faults along the coast near SONGS. This was a cost-effective approach that was used to
target more detailed analysis of topography using photogrammetry and high resolution GPS
measurements. They also enabled the mapping of beach ridges as continuous coastal features
from San Diego northward to Camp Pendleton, and provided a separate basis with which to
interpret coastal deformation.
2.2.5
Acquisition of J. P. Ke rn’s Unpublished Marine Terrace Maps and
their Place ment into the GIS Frame work
We acquired J. P. Kern’s eleven original unpublished geologic map overlays that were
completed in the 1970’s. The overlays were constructed over vintage (1968) USGS 7.5-minute
quadrangles and consist of individual overlay sheets showing marine terraces with abrasion
platform elevations, shorelines, faults, and beach ridges.
These overlays covered Kern’s mapping from San Diego (Point Lomas quadrangle) northward to
San Clemente (San Clemente quadrangle). The base maps for these overlays are the 1968 series
of USGS topographic quadrangle maps, which used NAVD29 as the vertical reference frame,
and NAD27 for the horizontal reference frame. We downloaded the 1967 and 1968
georeferenced USGS topographic quadrangle maps from the USGS historical topographic map
collection (http://nationalmap.gov/historical/) and placed them in Global Mapper software (Blue
Marble Geographics).
September 2013, Rev. 0
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We scanned the overlays using a large- format scanning platform and saved each scan as a
separate tiff file. We used Adobe Illustrator to auto-trace all lines and data on each overlay to
produce digitized overlays as separate layers. These were then placed in Photoshop to remove
the backgrounds and convert them to .png files. These, in turn, were opened in Global Mapper
and georeferenced onto the topographic base maps. Reference marks located on the four corners
of each overlay corresponded to the four corners of the topographic maps. Nevertheless, two of
the maps (Point Loma and San Onofre Bluff) required additional georeferencing (using other
landmarks common to both maps, such as road intersections and elevation benchmarks) to allow
precise registry of the data. From this data set, GeoTIFFs showing Kern’s geologic maps
overlain on the 1968 topo maps were produced for each quadrangle map, and these are all
included in Appendix XVI. Elevations stated on Kern’s maps were estimated from the 1968
series USGS topographic maps (Phillip Kern, personal communication to Thomas Rockwell), so
they likely have an elevation uncertainty of a few meters.
2.2.6
Historical Geotechnical Reports and Boring Log Data
A large amount of subsurface terrace elevation data have been collected over the years as part of
geotechnical investigations, especially for large developments. We acquired subsurface terrace
data from developments at Marblehead, Wishbone Hill, and the Newport Coast Marriot Hotel.
The Marblehead development, located in central San Clemente, was not completed due to
bankruptcy, and the site remains as it was after grading.
The Wishbone Hill development is located on the slopes above Crystal Cove State Park between
Reef Point and Pelican Point.
The Newport Coast Marriot is located east of Newport Bay in Newport Beach. All three
developments drilled a large number of borings and we were able to acquire 127 of the boring
logs, many with direct information on the presence or absence of marine terrace deposits.
The boring logs typically included information on the surveyed surface elevation at the borehole
site, the depth at which marine terrace sand and gravel was encountered, and the depth to top of
bedrock. The locations of all borings were recovered from the site investigation maps. The
maps were dropped into GIS and georeferenced based on the locations of preexisting streets and
the site boundaries that can be identified in modern imagery. From this georeferenced
framework, the locations of all boreholes were determined and assigned geographic coordinates.
Appendix XVII presents all of the boring data, including surface elevations, marine terrace
platform elevations, and/or top of bedrock elevations. For the Marblehead and Newport Coast
Marriott projects, all of the borehole locations have been identified as point features in GIS and
contain borehole ID numbers with top of bedrock elevations and/or abrasion platform elevations:
these are included in Appendix XVII. The Wishbone Hill data have not yet been converted into
point features, but the data are listed in spreadsheet format in Appendix XVII.
September 2013, Rev. 0
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Figure 9. Example of a shaded relief map (hillshade image created from a digital elevation
model [DEM]) of the San Joaquin Hills area derived from archival topographic maps made
before extensive urbanization modified the ground surface. Mapped extents (Grant et al. (1999)
of uplifted terraces have been overlain on the hillshade.
2.2.7
Historical Aerial Photographs
Historical USDA aerial photographs of the site vicinity (circa 1938 and 1952) have been
obtained and scanned at a high resolution; many have been georeferenced for use in GIS
software. These photos were used to identify subtle changes in topography related to paleoshorelines to map marine terraces, and to confirm Kern’s mapping of terraces and terrace
shorelines. The photos can also be used to generate DEMs using photogrammetric techniques, if
required in future studies, to provide representations of the ground surface at a relatively high
resolution. This may be particularly important for planning hazards assessment of active folds,
where changes in elevation of only a few meters may be spread over zones that are hundreds of
meters to a kilometer in width, and for use as one of the base maps in future field surveys.
September 2013, Rev. 0
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3.0
NEW TERRACE MAPPING
3.1
Introduction
To test the potential of a blind thrust beneath the coast of San Diego County and the vicinity of
SONGS, we initiated new mapping and surveying of the Pleistocene marine terraces on Camp
Pendleton and north of SONGS to Newport Beach to test whether the terraces are uplifted and
folded, as expected if deformed by thrust faulting, or whether they are simply uplifted by farfield dynamics, such as a rift- flank uplift mechanism (Mueller et al., 2009), in which case they
should be essentially horizontal.
The elevation data collected using high resolution GPS during the 2012-2013 field season was
used to create several surficial elevation profiles oriented normal to the beach ridges (Appendix
XIID). These profiles were used to compare the change in elevations of the numerous beach
ridges along the coastline.
Because the early terrace mapping efforts in the vicinity of SONGS (Figure 6) in the late 1970’s
were not well constrained in terms of elevation control, many of the shoreline-angle data for
SONGS were estimated, based on the use of an aneroid barometer, and/or represented projected
shoreline angles over relatively large distances rather than being precisely surveyed. In many
cases, the location of the shoreline angle for the terrace exposed in the sea cliff was unknown,
which imparted additional uncertainty to the validity of the shoreline angle elevations.
Furthermore,
the
interrelationship between
interglacial sea level high
stands, flights of multiple
marine terraces, and
implications
of
the
marine oxygen isotope
record were only then
being understood. Thus
any sense of correlation
of
marine
terrace
sequences to the north or
south of SONGS was not
fully appreciated. The
ability to accurately
determine
elevations
using GPS technology
now allows for a far
greater
accuracy
in
Figure 10. Oblique aerial photograph (by John Shelton, published in determining elevations
Ross and Dowlen, 1975), showing the pristine coast between SONGS
than ever could be
and Oceanside (to the left and right of the image, respectively), with a
imagined in the 1970s.
flight of marine terraces.
In the last few decades,
the coastal areas of
southern Orange County and northern San Diego County have experienced extensive urban
growth and development. However, SONGS may be ideally situated in that it is located near an
September 2013, Rev. 0
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unusually well preserved sequence of marine terraces that have been protected from this
urbanization by the fact that it lies within Camp Pendleton (Figure 10). The opportunity to study
the marine terraces across the coastal zone of Camp Pendleton offered a means to examine the
potential effects of regional versus local uplift, and to evaluate proposed seismic models that
predicted a variety of tectonic deformation effects.
3.2
Field Mapping Methodology, Unce rtainties and Reference Frames
Fieldwork in Camp Pendleton was mainly conducted between July and October of 2012
(Appendix XIIIa-d), with limited fieldwork between San Onofre State Beach and Crystal Cove
State Park being conducted in November 2012 (Appendix XIIIb). Additiona l field work from
southern Camp Pendleton and northward to Newport Beach was conducted primarily in the
Spring of 2013; the data from all of these surveys are compiled and summarized in Appendix
XIIIa. Paleontological investigations conducted in Camp Pendleton and north of SONGS during
2012 and 2013 are compiled and summarized in Appendices XIV and XV.
A fundamental potential problem in comparing elevation data collected in different time periods
is the issue of reference frames. Older topographic maps have used a variety of vertical
reference frames, including older geoid models (NAVD 27) or mean lower low water (MLLW)
instead of mean sea level (MSL), so resolving which reference frame was used is important
although not always achievable. For instance, J. P. Kern’s unpublished mapping from the 1970’s
and early 1980’s used older USGS topographic quadrangle maps for the base, which was based
on NAVD 27. However, within the City of San Diego, Kern used 5-foot contour interval (CI)
maps that were made by the City in order to estimate the elevations of shorelines within the City
limits (J.P. Kern, personal communication to T. K. Rockwell). There are two different vintages
of these 5- foot CI maps, one from the 1950’s and one from the 1960’s and they use different
reference frames (MLLW vs. MSL)
such that there is a 7 to 8 foot
difference in elevation of common
points. Although we assume Kern
used the ones referenced to MSL, we
are not certain of this. For these
reasons, and because topographic
control on Camp Pendleton was
limited to the USGS quadrangle
maps, we used modern GPS surveys
to constrain elevations of all terrace
platform, shoreline, and terrace
surface
elevations.
We
then
compared our new results with the
older data, with the caveats that 1)
the reference frames for the older
Figure 11. GPS elevations were determined from the data are not always known implicitly,
exposed contact between the eroded marine abrasion
and 2) the uncertainties of the older
platform and overlying marine gravels. In a few cases, the
data are usually substantially larger
shoreline angle was exposed and directly surveyed.
than stated.
September 2013, Rev. 0
Page 17 of 57
For our studies, we used a hand-held GPS unit (Trimble model GeoXH 6000 Series) to
determine precise elevations during foot surveys of marine terrace abrasion platforms (Figure 11)
(Table 1), shoreline angle elevations where exposed, or during terrace profiling. In some steep
canyons, however, it was necessary to hand level to a desired reference point from a previous
GPS-determined elevation point (see field notes, Appendix XIIIb) because the GPS signal was
interfered with by the canyon walls, or in some cases, was too weak to allow for precise
resolution of elevation.
A second Trimble GPS unit (model
GeoXT 2005 Series) using the same
parameter settings (Table 1) was used
System: Latitude/Longitude
on 20 November 2012 in San Clemente
Datum: WGS 1984
State Beach and at Crystal Cove State
Altitude Reference: mean sea level
Park (GP data points TAS GP 1210
Altitude Units: meters
through TAS GP 1220, Appendix XV).
Geoid: DMA 10x10 (Global)
GPS data from the Trimble GeoXH
Coordinate Order: North/East
6000 unit were regularly downloaded
Vertical datum: NAVD 88
and processed using Trimble GPS
Pathfinder software (version 5.3). Data
obtained by the Trimble GeoXT 2005 were processed using Trimble TerraSync software
(version 6.21). All elevation data cited in this compendium, unless otherwise noted, represent
post-processed data and not the original fieldrecorded elevations as are present in field
notes (Appendix XIIIb) taken at the time the
data were obtained.
Table 1. GPS parameter settings used for this study.
Machine uncertainties of the Trimble GeoXH
6000 GPS unit are stated to be +/- 10 cm, with
a post processed precision of +/- 10-30 cm,
which was typically accomplished by
accumulating 50 to 200 counts during each
actual field point occupation. To test the
precision of the unit, elevations (GP data,
Appendix XIIIa, and b) were determined at a
number of recorded benchmarks on Camp
Pendleton, and the elevations compared to
those in official records on the base (GPS/GIS
Services Department,
Camp Pendleton,
managed by Technology Associates), and they
consistently agreed within the Trimble’s stated
uncertainty. Additionally, multiple readings
over a several week period were taken at a
single benchmark (Camp Pendleton Control
Point no. 3159, Figure 12) on Stuart Mesa to
check the consistency and accuracy of the
Trimble GeoXH 6000 GPS unit over time; all
September 2013, Rev. 0
Figure 12. Control Point 3159 on Camp
Pendleton on the southern end of Stuart Mesa,
above the Santa Margarita River.
Page 18 of 57
measurements agreed to within 15 cm of each other (1). The original and post-processed data
are presented in Appendix XIIIa.
Another substantial source of uncertainty relates to field exposure s of paleo-shorelines, which
are the critical element of marine terraces as they are nearly horizontal datums at the time that
they are cut. In many cases, we were able to survey platform exposures to within a few meters
(laterally) from the base of an exposed paleo-sea cliff, so the actual shoreline elevation is known
to within a meter. In other cases, several points were taken on exposed platform elements and
the gradient was projected several to ten or more meters to the shoreline. We also surveyed a
point on the emerging paleo-sea cliff, which provided a maximum elevation. In these cases, the
elevation is reported as our best estimate based on the projection of the platform gradient, and
the uncertainty is reported as the
minimum and maximum surveyed
elevations near the shoreline; these
are typically +1 to +3 m in most
cases.
Figure 13. Modern shoreline angle (SLA) exposed about
1 km southeast of SONGS on San Onofre State Beach
(leased land from Camp Pendleton).
Figure 14. Modern gravelly beach berm on Camp
Pendleton north of Horno Canyon near Warrior Cove,
located about 40 m from the modern sea cliff.
September 2013, Rev. 0
A second aspect that relates to
shoreline angle elevations is that
although they are nearly horizontal,
the modern shoreline has been shown
to vary by +1 m and is typically a
couple of meters above mean sea
level using the NAVD88 reference
frame (Rockwell et al., 1989) where
it cuts across easily erodible rock or
at the back of sandy cuspate bays. In
areas of rocky shorelines and
promontories, the modern shoreline
is typically below mean sea level,
and we assume this to be the case
with the Pleistocene ones as well. It
is this potential variability that will
also be considered when we
determine whether a terrace is
folded, or whether the data argue for
flat uplift.
We surveyed the modern shoreline
angle where it was exposed one
kilometer southeast of SONGS
(Figure 13). Here, the shoreline is
cut into Monterey Formation and is
present at an elevation of 0.34 m
above MSL. Although we note that
this area is subjected to landsliding,
the modern shoreline angle is cut
across rock in this area and should be
Page 19 of 57
close to the average along this stretch of coast. We also surveyed the modern shoreline angle at
Salt Creek Beach in Dana Point, where it is cut across the resistant San Onofre Breccia (and in
an area of no slope instability); here, it is at an elevation of minus 2 m. We also surveyed a
gravel beach berm near Warrior Cove on Camp Pendleton (Figure 14), located about 40 m from
the base of the modern sea cliff; here, the top of the berm is at an elevation of 1.3 m above MSL
(GP 743). Assuming a 1 to 2 inner platform slope, as Camp Pendleton terrace gradients that we
measured typically ranged from 1 near major canyon mouths to as much as 5 for some of the
higher platforms where they cut across San Onofre Breccia. Platform gradients are relatively
lower where they cut across softer San Mateo, Capistrano, and Monterey Formation strata than
they are on more resistant or cemented bedrock such as the San Onofre Breccia. As the bedrock
here is Monterey Formation, we use the lower gradient range of 1 to 2. Assuming a sediment
thickness of 2 m, the modern shoreline angle should lie betwee n 0 and 2 m above MSL. From
these observations, we infer the modern shoreline angle to be slightly below mean sea level
where it cuts across resistant strata, such as San Onofre Breccia, and slightly above mean sea
level where it cuts across softer sedimentary rocks (San Mateo, Capistrano, and Monterey
Formations). We therefore assumed that paleo-shorelines were cut at about the sea level
corresponding to their respective high-stands, and that we expect about a 1 to 3 m variation in
paleo-shoreline elevations, depending on the lithology of the substrate.
Standard U. S. Geological Survey (USGS) 7.5- minute topographic quadrangle maps are based on
a polyconic projection and the 1927 North American Datum (NAD 27), which was subsequently
superseded by the North American Datum of 1983 (NAD 83). To convert latitude and longitude,
1000-m Universal Transverse Mercator (UTM), and California Coordinate System grid lines
from NAD 27 to NAD 83 (for this area of southern California) in order to correspond w ith
results of earlier mapping studies (e.g., the unpublished terrace mapping of J. P. Kern on the Las
Pulgas Canyon quadrangle) or of museum-archived fossil locality data, move the coordinate grid
lines 82 m east and 2 m south. For the Las Pulgas Canyon quadrangle, to convert from NAD 83
back to NAD 27, move the appropriate coordinate grid lines 82 m west and 2 m north. Note that
each quadrangle will have its own correction conversions. For purposes of ground surveying of
marine terrace data, especially considering the uncertainty level of determining SLA elevations,
NAD 83 can functionally be considered to be equivalent to WGS 84 (World Geodetic System
1984), currently the reference system being used by the Global Positioning System and therefore
our GPS units as well. For elevations, USGS topographic quadrangle maps published at least as
late as 1999 continued to use the National Geodetic Vertical Datum of 1929 (also known as the
Sea Level Datum of 1929) rather than its replacement, the North American Vertical Datum of
1988 (NAVD 88). The Trimble GPS units used in this investigation use the NAVD 88 Vertical
Datum, which agrees to within a meter to NGVD 29 surface elevations, although NAVD 88
yields elevations that are 60 to 80 cm higher than those derived from NGVD 29; for conversions,
see the NOAA internet web site (www.ngs.noaa.gov/tools/vertcon/vertcon.html). Thus to
compare our elevation data with those of previous studies, a correction factor must be applied.
Current editions of the topographic maps used in this study and in previous studies represent
photorevised (PR) or photoinspected (PI) (1975 or 1981) editions that originally dated to the
1960s (see below). The shorelines shown on these maps “represent the approximate line of mean
high water” and take into consideration a “mean range of tide of approximately 4 feet.” The map
editions available to J. P. Kern in his unpublished marine terrace mapping project would thus all
represent those published in 1965 or 1968 and PR or PI in 1975 or 1981. Editions used by Kern
September 2013, Rev. 0
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are shown in bold print in Table 2. Elevation data derived from the topographic maps are thus
based on the National Geodetic Vertical Datum of 1929.
Newer editions of these quadrangles, for example the 1997 edition of the San Luis Rey
quadrangle, utilize the newer 1983 (NAD 83) geodetic baseline as a frame of reference, but
continue to use the earlier National Geodetic Vertical Datum of 1929 (NGVD 29) rather than the
newer North American Vertical Datum of 1988 (NAVD 88) established in 1991. All GPS
determinations used in this investigation utilize the NAD 83/WGS 84 frame of reference, which
use NAVD 88 as a baseline and thus will not plot correctly on the published topographic maps
(Table 2) without conversion to the earlier NAD 27 baseline and NAVD 29 vertical datum.
Table 2. Dates of potential map editions used in this and previous studies.
Laguna Beach: 1965, 1965 PR 1981
San Juan Capistrano: 1968, 1968 PR 1981
Dana Point: 1968, 1968 PR 1975
San Clemente: 1949, 1968, 1968 PR 1975
San Onofre Bluff: 1949, 1968, 1968 PI 1975
Las Pulgas Canyon: 1949, 1968, 1968 PI 1975
Oceanside: 1949, 1968, 1968 PR 1975
San Luis Rey: 1949, 1968, 1968 PR 1975
3.3
Mapping on Camp Pendleton
The coastal strip of Camp Pendleton is relatively undeveloped and, geomorphically, is dominated
by a sequence of well-defined marine terraces (Figures 10 and 15) that are observable from the
Interstate 5 Freeway (I-5) between the Santa Margarita River in the south and the San Mateo
Creek drainage in the north. Prior to actual on-the-ground fieldwork, aerial photographs of the
entire coastal strip were examined and preliminary mapping was done on greatly enlarged
renditions to obtain a better
understanding of the terrace
relationships as preserved on
the ground. The marine terrace
sequence can be divided into
three sets of terraces, with the
upper set separated by a major
slope, or palisade that is
particularly evident in the
northern
part
of Camp
Pendleton (Figure 15). The
lowest set of terraces is mostly
buried beneath a thick cover of
Figure 15. Oblique aerial photograph (cropped from the same alluvium, except at the coast
photo as in Figure 10) showing the three sets of terraces we where the fore-edge of the first
mapped in this study. The lowest set is mostly buried by alluvial emergent terrace is usually
fan deposits. The upper terraces are covered by a thin veneer of exposed (Figure 16). Towards
littoral sediments, with colluvial cover near the paleo-shorelines.
September 2013, Rev. 0
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the southern part of Camp Pendleton, there are some exposures where the low terraces are not
buried, and here, terraces that have been mapped and inferred to represent MIS 5 through MIS 9
(Kern and Rockwell, 1992), are exposed and were surveyed. Towards the northern part of Camp
Pendleton, these terraces are buried or cut-out west of El Camino Real (Appendix XIIIc), above
which the first observable terrace lies at about 60 m elevation.
Above and east of El Camino Real, the two sets of terraces, when so distinguished, will be
referred to as either the middle or upper terrace group. In the north, the upper terraces reach an
elevation approaching 380 meters, whereas in the south, the highest preserved terraces are much
lower in elevation and correlate
with the middle set of terraces in
the north.
Because the major part of coastal
Camp Pendleton has remained
relatively undeveloped, access
along the coastal bluffs, or inland
from old El Camino Real, is by
foot except along sparse dirt roads.
Field work in the summer field
season of 2012 involved on the
order of 30 terrace traverses and or
transects to establish the slope
profiles and map remnant terrace
deposits. In addition, we mapped
Figure 16. Alluvial fan deposits burying the lower terrace and surveyed numerous local
set. Here, the first emergent terrace is buried by up to 20 m of
terrace exposures over the entire
upper Pleistocene alluvial fan deposits.
length of Camp Pendleton
(Appendix XIIIb, c). In the north,
as well as on the higher terraces in
the south, the abrasion surfaces
were primarily cut into bedrock of
the San Onofre Breccia, whereas in
the coastal and lower southern parts
of Camp Pendleton, the sedimentary
bedrock formations were primarily
the San Mateo, Capistrano, and
Monterey Formations.
The latter
formations were often incorrectly
mapped on the available geologic
maps for the southern part of Camp
Pendleton.
Figure 17. Example of paleo-shoreline where the actual
shoreline angle is buried and we estimate its elevation by The purpose of the foot surveys was
measuring the base of the exposed sea cliff and the highest to obtain accurate GPS elevation data
elevation of the exposed abrasion surface. This provides of the marine terrace platforms and
absolute bounds for the SLA elevation. The best estimate is of terrace shoreline angles, where
exposed, so as to be able to better
made by projection of the inner edge slope of 3-5 o.
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determine uplift rates of the terrace sequence, as well as any differential deformation from north
to south. Because of the locally thick alluvial and colluvial cover over many of the terrace
platforms, particularly evident in the lower terrace sequence along the coastal bluffs and below
the palisade slope, it was commonly necessary to estimate the position and elevation of possible
shoreline angles by projecting from platform and degraded paleo-sea cliff exposures, which
provided minimum and maximum elevations for the paleo-shoreline. In other cases, the abrasion
surfaces are capped by only 1 to 2 m of gravelly marine sediments, making for easier direct
measurement of the shoreline elevations. Reliable elevation data on abrasion platforms were
most often obtainable at the terrace fore-edge, or exposed nose of the terrace remnant, where the
eroded sea cliff of the next lowest terrace was exposed. On the terraces above old El Camino
Real, the abrasion platforms across exposures of the San Onofre Breccia were often very close to
the surface or covered with less than a meter of surficial sediment so that it was often possible to
define a surface gradient on bedrock that, when used with the eroded surface gradient of the sea
cliff above it, could be used to estimate the position and elevation of the shoreline angle for that
terrace remnant (Figure 17).
Other features that could be used as evidence that any bedrock exposure represented the actual
marine abrasion platform was the presence of terrace gravels, typically consisting of gravel fields
made up of smooth flattened pebbles and/or cobbles (Figure 18). Their presence would represent
the maximum elevation of the abrasion platform at that point, or if adjacent to or very close to
Figure 18. Exposures of oblate spheroid pebbles and cobbles, interpreted as of marine origin. Note
the well sorted fine-grained sand in the left photograph, which is also interpreted as of marine origin.
Figure 19. Boreholes in rocks and abrasion platforms interpreted to have been made by rock-boring
clams in the family Pholadidae.
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the original sea cliff, the maximum elevation of the shoreline angle of that terrace. Gravel fields
on some of the broad high terraces were often extensive and were associated with very little
terrace cover above bedrock of San Onofre Breccia, except at the very back edge where the
cover would be thicker below the terrace sea cliff and above the shoreline angle. The presence
of rock-boring clam holes in bedrock (Figure 19) was also evidence that the exposed surface
represented the marine abrasion platform rather than an otherwise eroded surface.
In most areas, the position and elevation of the shoreline angles were covered by some alluvial
and colluvial cover, although
we could commonly get to
within a couple meters above
or
below
the
actual
paleoshoreline. The exceptions
were several road cuts,
particularly along San Onofre
Peak Road, in the north, and
along Macs Road in the south
(Appendix
XIIIc),
where
shorelines were either exposed
or buried by very little
sediment.
On San Onofre
Peak Road, shoreline angles
were determined at elevations
of 97.5 m, 123 m, 130 m and
139 m in the middle set of
terraces
below the main
Figure 20. The 285 m shoreline exposed in the road cut along San
palisade slope, and at 248 m
Onofre Peak Road.
and 285 m in the upper set of
terraces (Figure 20) farther up the terrace sequence above the palisade slope. Surface cover of
the lower terraces north of Las Pulgas Canyon consisted of up to 20 to 30 m of alluvium and
colluvium. In contrast, the mid and upper level terrace sequences had considerably less to very
little alluvial cover, suggesting that most or all of the small drainages and canyons were incised
sometime after the abandonment of the 60 m terrace. This was fortuitous, as the abrasion
platforms are capped by only a thin veneer of marine deposits in most places, except at the paleoshorelines where there was also some additional colluvium.
Nevertheless, the topographic surface expressions of the several mid- level terraces were often
subtle because the riser between terraces was typically only a few meters in height, so that
surface profiling commonly only shows slight inflection of the surface sediments at the paleoshorelines.
3.4
Data Collection North of Camp Pendleton
Although the location of SONGS adjacent to the well preserved flight of marine terraces within
Camp Pendleton allowed for extensive data gathering related to regional uplift of the area, all of
these terrace data have been derived from areas to the south o f the Plant. The primary mapping
effort during the summer field season of 2012 was concentrated almost entirely within the limits
of Camp Pendleton. However, well preserved marine terraces have been documented and
September 2013, Rev. 0
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mapped along the coast north of SONGS, although little attention has been paid to obtaining
accurate elevation data of the terrace platforms, locating the back edges (i.e., shoreline angles) of
these terrace remnants, or determining the elevations of these shoreline angles. Because accurate
terrace elevations are a requisite for determining local or regional uplift rates and folding, careful
mapping of the marine terraces to the north of SONGS, to relate the terrace data there with those
obtained to the south of the Plant in Camp Pendleton, were completed in late 2012 and Spring of
2013.
Because of the rapid growth and urban development of the narrow coastal strip of southern
Orange County, large areas have been so extensively modified by this development that it is no
longer possible to obtain the level of marine terrace data that was once possible before this
growth (for example, terrace mapping of Vedder et al., 1957, 1975). However, several areas of
the southern Orange County coast are still relatively pristine, or at least still remain as open
space, these being in Crystal Cove State Park, on the Dana Point headlands, and in San Clemente
State Beach, all in Orange County, and in San Onofre State Beach adjacent to SONGS in San
Diego County. Furthermore, a number of existing roadcut exposures, and exposures along foottrails are open to access for surveying.
Preliminary investigations and data gathering (Appendices I through XIIc) prior to any of the
current field activity documented the presence of several Pleistocene fossil localities on marine
terraces along this part of the coast. Preliminary fieldwork for this study resulted in obtaining
marine terrace elevation data from exposed terrace platforms along the sea cliffs between Crystal
Cove State Park and San Clemente State Beach (Appendix XIIIa), and the collection of new
fossil localities and the recollection of other localities in these two park areas. The half dozen
new fossil collections have been processed and the faunas identified (Appendix XV). Additional
fossil materials archived at LACMNH and SDNHM from several other localities were also
examined and analyzed in the light of the new collections. Corals obtained from these
institutional collections have been analyzed by U-series methods to determine their ages.
3.5
Field Mapping of Marine Terraces north of SONGS in the Spring of 2013
Several of the lower marine terrace abrasion platforms and their associated shoreline angles are
well exposed at a number of locations north of SONGS, starting at Cristianitos Road in San
Clemente. For this field mapping north of Cristianitos Road through San Clemente, J. P. Kern’s
unpublished maps provided a useful base upon which to collect new elevation data. As we only
acquired the maps late in 2012 and processed them in early 2013, we did not have use of them
for the preliminary work north of SONGS, nor for the work on Camp Pendleton in 2012. Farther
north of San Clemente, not mapped by Kern, mapping is based on analysis of aerial photography,
field relationships, and GPS measurements.
We attempted to survey all locations where abrasion platforms with terrace deposits were
exposed. These survey data are presented in Appendix XIIIa. In Subsection 3.5, each locality or
area where terrace elevations were acquired is discussed separately in order to explain the
uncertainties in interpreted shoreline angle elevations. Where a specific shoreline angle was not
exposed or accessible in outcrop, but the accompanying abrasion platform was exposed, we
measured the elevation and gradient (slope) of the abrasion platform, and then projected the
abrasion platform surface up-dip from our elevation measuring location to the next major
topographic inflection point or break in slope that represented the paleo-sea cliff to obtain the
approximate shoreline angle elevation. Note that due to differing erosional rates within softer
September 2013, Rev. 0
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bedrock formations, such as the Capistrano and San Mateo Formations (located within and south
of San Clemente), as compared to the relatively harder, more erosionally-resistant bedrock, i.e.,
the San Onofre Breccia north of San Clemente, we used a set of abrasion platform slope-ranges
for each of these two areas. These platform slope ranges will be discussed later in this report.
Marblehead/San Clemente Area – Terrace shoreline angles are exposed at 8.7 to 12.1 m, 26 m,
34.5 to 36.3 m, and 48 to 50 m elevations between San Clemente and the Marblehead
development (located in central San Clemente). The lowest terrace shoreline angle exhibits two
elevations: an 8.7 m elevation about 0.5 km south of San Clemente Pier on a platform exposure
that is located within about 3 m horizontally of the shoreline angle (Figure 21), meaning the
actual shoreline angle elevation is not likely to exceed 9 m. In contrast, a 12.1 m shoreline angle
elevation was measured in San Clemente State Beach at the end of Avenida Calafia at the back
of a parking lot (Figure 22): the paleo-sea cliff is seen rising behind the shoreline angle and
terrace deposits. However, this exposure is immediately adjacent to a canyon mouth and terrace
deposits appear to wrap into a paleo-canyon, indicating that the canyon has been in existence
since at least the time of formation of the first or lowest elevation emergent terrace.
These two abrasion platform elevations are not necessarily in disagreement, as the 8.7 m value is
a minimum (but likely by only a small amount), and the 12.1 m value is a maximum because it
may reflect run- up into the canyon mouth that was present at the time of terrace formation.
Figure 21. Shoreline deposits of the first emergent terrace in San Clemente 0.5 km south of the San
Clemente Pier at 8.7 m elevation.
Consequently, we use the current observed elevation range of 8.7 to 12.1 m for the elevation of
the first (lowest elevation) emergent terrace in the San Clemente area.
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Figure 22. Paleo-beach exposure of the first emergent terrace,
The second (next higher
elevation) emergent terrace
shoreline angle was surveyed
at
the
Marblehead
development site at an
elevation of 26 m, where it
was exposed in an open cut
associated with abandoned
grading operations (Figure
23). This shoreline angle
exposure was also associated
with a major drainage and
may reflect a component of
run- up into the canyon at the
time of shoreline formation.
Along Cristianitos Road, we
surveyed a platform exposure
at 23 m elevation that is
within 40 m of the paleoshoreline angle. At Avenida
Calafia, in San Clemente State
Beach, located approximately
1.5
km
northwest
of
Cristianitos
Road,
the
maximum
platform
elevation
Figure 23. Shoreline angle exposure of the 2 nd emergent terrace at was surveyed at 21.8 m,
the Marblehead development.
which, based on J. P. Kern’s
mapped
shoreline
angle
location, is located about 160
m from the shoreline angle.
We confirmed this location
through analysis of 1952 aerial
photography. The platform
gradient adjacent to Avenida
Calafia was determined by
survey of three platform
exposures along a drainage in
San Clemente State Beach to
Figure 24. Paleo-shoreline for the 3 rd emergent marine platform
be about 1 degree. Assuming a
exposed along Cristianitos Road in southernmost San Clemente.
constant slope to the shoreline
yields a shoreline angle elevation of 25 m. If the gradient increases near the inner edge, the
estimated elevation would be slightly higher. Therefore the elevation of the second emergent
terrace shoreline in the San Clemente area is 23 to 26 m. The marine terrace faunas from the
second terrace at San Clemente State Beach are treated in Appendix XV.
Avenida Calafia, San Clemente State Beach, at 12.1 m elevation.
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Figure 25. Exposure of fossiliferous marine sand and gravel
associated with the 4 th emergent terrace at the Marblehead
development. Marine deposits are at least 2 m thick, and the
abrasion platform is buried below grade. Base of exposure is at
51 m. The southbound I-5 roadcut, located a few meters
immediately to the east (behind) this exposure shows only
Capistrano Formation to the surface, indicating that this deposit
is essentially at the paleo-shoreline.
Higher terrace shoreline angles
are exposed at elevations of 36.3
m and 48 m along Cristianitos
Road, and at 34.5 m and 50 m at
Marblehead (Figures 24, 25).
Assuming these represent the
same two terrace shoreline
angles, which is reasonable
because they are spatially close
(5 km apart), the measured
shoreline angle elevations for
these terraces in the San
Clemente area are taken to range
from 34.5 to 36.3 m and 48 to 50
m. Adding a half meter of
uncertainty to account for
additional lateral variation of the
shoreline angle elevation, we
estimate a range of 34 to 37 m
for the third terrace shoreline
angle elevation, and 47.5 to 50.5
for the 4th terrace shoreline angle
elevation. Based on their similar
elevations of about 50 m, the
fossiliferous exposure shown in
Figure 25 would correlate with
localities along the Interstate 5
right of way just north of the
Marblehead property (SDNHM
collection records), as well as
that along the N 1200 block of
El Camino Real in central San
Clemente.
Dana Point – Two terraces are
preserved
at Dana Point
Headlands,
but only
the
elevation of the first, or lower,
terrace could be constrained. A
Figure 26. Exposure of the terrace fore-edge at 31.2 m at Dana
platform exposure (Figure 26)
Point. Projection of this elevation to the shoreline yields an
yielded an elevation of 31.2 m,
estimate of the shoreline angle at about 32.7-33 m.
located about 35 m from the
shoreline angle, based on
analysis of aerial photography. The bedrock at this locality is San Onofre Breccia, which
typically expresses higher abrasion platform gradients than where abrasion platforms cut across
the softer San Mateo or Capistrano Formations. Using a 2.5 to 3 degree gradient, we estimate
September 2013, Rev. 0
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the shoreline angle elevation to be 32.7 to 33 m, so for the Dana Point Headlands, we report a
best- estimate shoreline angle elevation of 32.9 m with a plausible elevation range of 32 to 34 m.
Within the City of Dana Point,
a lower terrace shoreline angle
is exposed behind the Rib
Joint Restaurant at the
intersection of Pacific Coast
Highway and Del Obispo
Street (Figure 27). The first
emergent terrace shoreline
angle at this location was
directly surveyed at 8.9 m.
One block north of this
exposure, a higher terrace
abrasion platform is exposed at
32.4 m elevation within a
couple meters of its paleoshoreline angle, as interpreted
from an abrupt rise in
Figure 27. Exposure of the first emergent terrace at Dana Point,
topography and because of an
located behind the Rib Joint along Pacific Coast Highway.
even higher abrasion platform
fore-edge that is exposed at 38.5 m
elevation along The Street of the Copper
Lantern one block to the north (Figure 28).
From these relationships, we estimate that
this terrace shoreline angle is about 32.4 to
33 m elevation and is likely to be the same
terrace exposed at a similar elevation in the
Dana Point Headlands at 32 to 34 m
elevation.
The shoreline angle for the highest terrace
exposed on The Street of the Copper
Figure 28. Exposure of the fore-edge of a marine
Lantern was estimated at 48.4 m. This
terrace at 38.5 m elevation on the north side of The
elevation is based on a platform exposure
Street of the Copper Lantern in Dana Point. The
road flattens at the top of the immediate slope, with
located on the west side of the street and
most houses up the street sitting directly on the
which was measured to be at an elevation of
marine terrace surface, as shown in Figure 29.
38.5 m (Figure 28). This exposure is
located about 220 m from its paleoshoreline based on an abrupt rise in surface topography at the inferred location of the buried
shoreline angle. The bedrock in this area is composed of easily erodible silt and sand of the
Capistrano Formation, so terrace gradients are expected to be relatively low (i.e., 1° to 2°).
Assuming a 1 degree platform slope, and assuming a constant gradient to the shoreline angle,
this yields a lower elevation bound of 42.3 m. With a 2 degree slope, which is higher than any
terrace gradients we have surveyed on this formation, we estimate an elevation of 45.7 m. Thus,
September 2013, Rev. 0
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because the projection distance of 220 m is relatively small, the inferred shoreline angle
elevation only varies by about 3 m in spite of doubling the inferred platform gradient.
The road surface at the base of the inferred paleo sea cliff represents a maximum shoreline angle
elevation, as indicated by mapping on aerial photography and by the slope inflection on The
Street of the Copper Lantern (Figure 29). Assuming that the road is draped over the original
landscape, and that a non-significant
amount of material was removed prior
to road construction, the maximum
shoreline angle was surveyed at an
elevation of 45.6 m. From these data,
we estimate the actual shoreline angle
elevation to be at about 43 m with an
uncertainty of about 2 m (assumes at
least a half meter of terrace cover
below the road for the maximum
value, and a terrace gradient of one
degree for the minimum value).
Figure 29. Inferred location of the shoreline angle for
the marine terrace exposed in Figure 28. Note that most
It should be noted that the first
houses are built directly on the terrace surface, which is
preserved emergent terrace at the
flat and well preserved. The shoreline is inferred at the
Dana Point Headlands is the ca. 34 m
sharp break in slope, as indicated by the arrow.
terrace (Figures 26, 30), whereas a
lower terrace is preserved at 8.9 m in
the town of Dana Point itself (Figure 27) and two lower terraces are preserved at elevations of
approximately 9 m and 23 m both to the north and south of Dana Point. Thus, these lower
terraces at the Dana Point Headlands have apparently been affected by several different
Figure 30. The ~34 m terrace is the first emergent marine terrace in the Dana Point area, but lower
terraces are preserved both to the north and south of Dana Point.
alternative processes, such as erosion, differential uplift, or faulting.
Laguna Beach – The first emergent terrace shoreline angle was recognized at three localities in
the City of Laguna Beach. At the Montage Resort, the shoreline angle was directly surveyed at
September 2013, Rev. 0
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an elevation of 8.5 m (Figure 31). Nearby on the resort property, the platform is exposed for tens
of meters up to within a meter of the shoreline angle, with platform elevations ranging from 6 m
to a maximum of 8 m adjacent to the paleo-shoreline. The bedrock at this site is San Onofre
Breccia, and the platform gradient based on these surveyed points is about 2.3 degrees, a bit
lower than some other San Onofre Breccia localities, perhaps due to compositional differences
within the formation itself, but higher than any platform gradients that cut across the San Mateo
or Capistrano Formations that we measured. Considering that this shoreline angle locality was
taken at a bedrock promontory, this probably represents a minimum shoreline angle elevation
value for this section of coastline, as promontories commonly exhibit slightly lower shoreline
angle elevations because they exist due to increased resistance to erosion and require higher
wave energy to be eroded.
Figure 31. Shoreline angle of the first emergent terrace at the
Montage Resort, as exposed adjacent to a wheel chair ramp,
surveyed at 8.5 m elevation.
Figure 32. Second emergent terrace in the Laguna Beach
area, as viewed from Aliso Beach parking lot. See Figure 33 for
a detail of the terrace deposits.
September 2013, Rev. 0
The first emergent terrace
platform was also exposed and
surveyed at an elevation of 8.7 m
at Heisler Park in Laguna Beach
at a site located within a few
meters
laterally
from
the
shoreline angle. The Heisler Park
SLA was constrained by our
mapping on aerial photos and
field observations (the steep rise
in topography and bedrock that
were observed at the back of the
park).
Between Montage and
Main Beach Park, several
abrasion platform exposures were
surveyed, with elevations ranging
from 5.7 to 8 m, all consistent
with a shoreline angle elevation
between about 8 and 9 m.
Consequently, the best estimate
for the shoreline angle elevation
of the first emergent terrace
through Laguna Beach is 8.5+0.5
m, with the uncertainty covering
all of the surveyed platform and
shoreline angle exposures as well
as the +10 cm uncertainty of the
GPS survey data.
The second emergent terrace at
Laguna Beach is exposed in a
trail cut on the east side of Pacific
Coast Highway above Aliso
Beach (Figure 32), with abrasion
platform elevations ranging from
Page 31 of 57
17.1 to 19.3 m (Figure 33). The highest surveyed point was taken within about 10 m of the
paleo-shoreline angle, and a point on the paleo-sea cliff above the shoreline angle cut into the
San Onofre Breccia was surveyed at an elevation of 22.3 m. Thus, the second terrace shoreline
angle elevation must fall between 19.3 and 22.3 m, so we estimate the shoreline elevation at
20.8+1.5 m at Laguna Beach.
The fore-edge of the third emergent platform is exposed on the east side of the Pacific Coast
Highway just north of Upland Road at an elevation of 27.5 m. The shoreline angle for this
terrace platform is estimated to be about 30 m to the east at a sharp inflection obse rved at the
Figure 33. Fore-edge of the ~21 m terrace exposed in a nature trail on the east side of Pacific Coast
Highway across from Aliso Beach. The terrace elevation at this site was surveyed, and varies between
17.1 to 19.3 m elevation, sloping up to the east.
base of Arch Street, where surficial topography rises steeply. The road surface at this inflection
was surveyed at an elevation of 36.6 m, and likely overlies a section of colluvium and terrace
deposits so it is a maximum elevation for the third terrace shoreline. The bedrock here is San
Onofre Breccia, and as the surveyed platform location is about 30 m away from the inferred
shoreline angle, we used an estimated platform gradient of 2 to 3 degrees to yield a best estimate
of about 28.6 to 29 m for the shoreline angle elevation, with a maximum possible elevation range
of 27.5 to 36.6 m. Because there is likely several meters of colluvium and terrace cover at the
base of the high slope (paleo-sea cliff) at Arch Street, the maximum elevation is likely closer to
33 m. Consequently, we use an elevation of 29 +4 /-1.5 m for the best estimated elevation of the
third terrace shoreline angle.
Higher elevation marine platform deposits are exposed in road cuts in Laguna Beach. Figure 34
shows an exposure of the fore-edge of a marine terrace at 48.5 m elevation, as exposed along
Brooks Street. The shoreline angle is inferred to be about 20 m to the northeast based on the
abrupt rise in topography, although residential structures and dense vegetation make this a rough
September 2013, Rev. 0
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estimate. If correct, and assuming a 2 to 3 degree abrasion platform gradient for San Onofre
Breccia, the shoreline angle elevation is calculated to range between approximate elevations of
49.2 m to 49.5 m.
In summary, the first
three emergent terraces
at Laguna Beach have
shoreline
angle
elevations estimated at
8.5+0.5 m, 20.8+1.5 m,
and 29+4 /-1.5 m, with a
fourth terrace shoreline
angle elevation close to
49 m or 50 m.
Crystal Cove – Two
terrace
levels
are
Figure 34. Fore-edge of a marine abrasion platform exposed along
preserved in Crystal
Brooks Street, surveyed here at 48.5 m. The shoreline is not exposed but Cove
State
Park,
is inferred to be less than 20 m to the northeast.
although
only
the
approximate elevation of
what appears to be the
first shoreline angle was
able to be measured. If
so, then this location
yielded
surveyed
elevations that ranged
from 7.8 to 8.7 m. At
one location in front of a
small canyon, fluvial
deposits interfinger with
well-sorted sand that are
interpreted to be beach
sands
(Figure
35),
although
an
actual
platform
is
not
preserved. The shoreline
sands were measured at
Figure 35. Exposure at Crystal Cove State Park, with well sorted fine
elevations as high as 8.8
sand interpreted to be of littoral origin interfingering with bedded, clast- m,
with
Monterey
supported angular gravel of fluvial origin. The well sorted sand is
Formation
bedrock
interpreted to represent the level of the beach during the time of
exposed at 9.8 m. The
formation of the first emergent terrace.
fluvial
gravels
are
composed of bedded, angular clasts that exhibit a water-transported origin based on their bedding
and clast-supported nature. In contrast, the well-sorted sand is identical to that found on the
modern beach except that it is highly oxidized. Taken together, these observations indicate that
these deposits accumulated at the mouth of the small canyon that is present today. In its current
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Page 33 of 57
state, the canyon is cut into Monterey Formation bedrock and is truncated by the modern beach,
resulting in a near vertical seacliff that extends 3 to 4 m below the mouth of the canyon to the
modern beach. The thalweg of this canyon exposed in the seacliff is within about 1 m below the
highest exposure of well oxidized beach sand located no more than 12 m to the northwest. The
well sorted sand is interpreted to represent beach deposits washed up into this small canyon.
Consequently, the current elevation of these deposits is close to the elevation of t he paleo-beach
at the time of cutting of the first emergent terrace.
The fore-edge of the second emergent terrace is exposed at an elevation of 12 m. In the same
area 900 m to the east, surveyed elevations of the second emergent terrace platform range in
elevation from 12 m to 23 m, with some of the marine sands containing marine fossils. The 23 m
elevation for the second terrace was as high as the platform with marine deposits that could be
followed in a small drainage. Bedrock without overlying marine deposits was surveyed at 23.5 m
in the same drainage. A distinct abrupt rise in bedrock was not observed, but the canyon was
obscured by vegetation and exposures would need to be dug out to expose the shoreline angle.
Consequently, we estimated the shoreline angle elevation to be between these two surveyed
points, the one with fossiliferous marine deposits and the other without, with a best estimate of
this elevation to be 23.2+0.3 m (including GPS uncertainty). The marine terrace fauna from the
second terrace at Crystal Cove State Park is treated in Appendix XV.
Newport Beach – At least four different marine terraces are preserved near Newport Beach and
Newport Bay up to an elevation of about 50 m, although only the shoreline angle elevation of the
first, or lowest, emergent terrace is directly well constrained by GPS data from this project.
Platform elevations on the first emergent terrace range from 6.9 to 8.5 m, with the highest
elevation only a few meters away from the actual shoreline angle (Figure 36). Therefore, we
take the 8.5 m elevation to represent the shoreline angle elevation of the first emergent terrace at
Newport Beach. The marine terrace fauna from this low platform is treated by Powell (2001)
and exhibits a cool-water aspect.
Figure 36. Shoreline gravels and paleo-sea cliff of the first emergent
terrace at Newport Beach. The abrasion platform elevation is 8.5 m,
located only a few meters laterally from the buried shoreline angle.
Projection of the platform gradient adds less than 10 cm to the
surveyed elevation.
September 2013, Rev. 0
The top of bedrock above
the first terrace shoreline
angle at the fore-edge of
the second terrace was
surveyed at an elevation
of 14.7 m, which is a
gross minimum for the
elevation of the second
emergent terrace shoreline
angle.
However, the
second terrace shoreline
can be estimated from
inset estuarine deposits in
Newport Bay (Figure 37)
and from geotechnical
borehole
data
taken
nearby. Below Galaxy
View Park, on the
northwest side of Upper
Page 34 of 57
Figure 37. Estuarine terrace inset into the third terrace on the north side of Upper Newport Bay
below Galaxy View Park. The abrasion surface reaches as high as 21 m, and the terrace sands to
about 22 m.
Newport Bay, well-sorted fine sand is present on a terrace surface with surveyed elevations up to
about 21 m. The terrace and platform surface has been notched below the fore edge of the third
terrace along the margins of the bay, and is morphologically distinct. Unpublished abrasion
platform elevation data derived from geotechnical borings during development of several
housing projects in the area were used by Grant et al. (1999) to formulate their interpretations.
The platform elevations from around Newport Bay, originally determined in feet and presented
in meters, are presented on Figure 38. The elevations are close estimates because most are
resolved with an accurate pick on the depth to the abrasion platform or top of bedrock in the
boring, but the surface elevations are typically determined from topographic maps.
The platform elevations of the second terrace that are closest to the first emergent shoreline angle
site range from 18 to 21.9 m, and these deposits include LACMIP localities 68-A and 68-B of
Kanakoff and Emerson (1959). Near Galaxy View Park, the platform elevation is at a maximum,
approximately 27 m (Figure 38). The Galaxy View Park terrace inset is present below the 27 m
platform elevations, arguing that these are separate terrace levels. Furthermore, the 21-22 m
estimate for the shoreline of the terrace inset agrees very well with the maximum platform
elevation reported in the geotechnical data, located a couple hundred meters to the west. These
relationships will be discussed in more detail in the interpretation section.
September 2013, Rev. 0
Page 35 of 57
Figure 38. Platform elevation estimates taken from geotechnical boring data from various housing
projects (L. Grant Ludwig – unpublished data, summarized in Grant et al., 1999). Profile lines A-A’,
B-B’, and C-C’ are locations of profiles presented in the interpretation section of this report.
Described fossil localities of Kanakoff and Emerson (1959), Peska (1976), and LACMIP locality 136
[as “166”] are indicated by blue dots.
The third emergent terrace adjacent to Upper Newport Bay supports the surface upon which
September 2013, Rev. 0
Page 36 of 57
Galaxy View Park and extensive housing is developed (Figures 37 and 38). Elevations for this
and higher terraces have not been surveyed for this study, but the abrasion platform at Galaxy
View Park is about 5 to 6 m above the surveyed shoreline for the second terrace level based on
the geotechnical data.
The shoreline angle elevation for the terrace upon which Galaxy View Park is situated is welldefined on the east side of Upper Newport Bay, where the geotechnical data indicate an elevation
of about 30 m. To the southeast, platform elevations are estimated to be as high as 35 m (from
another study), rising to a higher platform with elevations of 47 to 49 m. Interpretations of these
relationships are discussed in the interpretations section of this report (Section 5.0).
In summary, the shoreline angle elevations of the first two emergent terraces in the Newport
Back Bay area are determined to be about 8.5 and 21 to 22 m, with the third? and fourth?
emergent terraces at elevations of about 30 to 35 m and ~50 m, very similar to those surveyed to
the southeast along the coast.
3.6
Summary of New Results
We recognize the preservation of 21 marine terraces along the coastal strip on Camp Pendleton,
with fewer well preserved or recognizable terraces north of SONGS, largely due to coastal
development. However, on Camp Pendleton, the lowest terraces are mainly buried along
extensive portions of the coast northwest of Stuart Mesa to SONGS, whereas the middle and
upper terrace sequences are typically preserved and well exposed inland of the coast (Figure 15).
Localized preservation of marine terraces is common, as any new high stand of the sea can
potentially erode deep into the landscape and remove entire sequences of older terraces. This
phenomenon can be easily observed in the vicinity of UCSD in La Jolla Shores (Figure 39),
where the first emergent terrace, at an elevation of 105 m corresponds to the Tecolote terrace of
Kern and Rockwell (1992), which
is correlated to MIS 21 at about
800 ka in age.
Figure 39. Examples of spotty preservation of low terraces
in La Jolla. Terraces can be completely removed during any
subsequent sea level high-stand, so most terraces are
typically only locally preserved along a coastline. Terraces
cut during a long interglacial high stand that are followed by
shorter and lower high stands (such as MIS 5e followed by 5c
and 5a) typically are better preserved than the shorter-lived
high stand terraces.
Nevertheless, the example here
demonstrates that even terraces that are typically well
represented along the coast, such as MIS 5e, can be locally
removed.
September 2013, Rev. 0
In the vicinity of Stuart Mesa on
Camp Pendleton, well preserved
marine terraces were measured as
part of the recent field work,
including terrace shorelines at
elevations of 10.4 m and 22.7 m,
which
are,
respectively,
at
essentially the same elevations as
the “MIS 5a” “Bird Rock” terrace
and the “MIS 5e” “Nestor” terrace
initially mapped within and south
of Camp Pendleton by Kern and
Rockwell, 1992 (also summarized
herein on Figure 40 and in Table
3). In addition, terrace shorelines
on Camp Pendleton’s Stuart Mesa
were mapped at elevations of 34.6
m and about 45 m during the 2012Page 37 of 57
2013 field work; these are at
nearly the same elevations as
Kern and Rockwell’s (1992)
“MIS 7” “Stuart Mesa” terrace
and their “MIS 9” “Guy
Fleming” terrace.
Farther northwest on Camp
Pendleton, these terraces are
buried by a progressively thicker
section of alluvial fan deposits
such that only the fore-edge of
the lowest platform is exposed
along the coast. However, north
of SONGS, low elevation
terraces are again exposed, with
elevations of the first four
emergent terraces from San
Clemente northwest to Newport
Beach measured at relatively
constant elevations of about 8 to
9 m for the first emergent terrace
(and possibly 2 to 3 m higher in
San Clemente), 22 to 26 m for
the second emergent terrace
(with the high estimate only in
San Clemente), 29 to 36 m and
48 to 50 m for the third and
fourth emergent terraces (Figure
41). It is also possible that the
53+2 Perry Grove terrace on
Camp Pendleton and northern
San Diego County corresponds
to the ~50 m terrace farther
north.
Figure 40. Surveyed shoreline angle elevations with
uncertainties, as measured previous to 2012-2013, along the
coast southeast from SONGS. The average elevations are
shown at the right side of the diagram, along with the
corresponding terrace names and elevations published by Kern
and Rockwell (1992). The uncertainties indicated for the Camp
Pendleton terrace elevations represent only the variation in the
best-estimated elevations. All data are presented in Appendix
XIII.
September 2013, Rev. 0
Page 38 of 57
4.0
SUMMARY OF NEW DATA COLLECTION
As of the time of the 2011 Progress
Report, we had compiled a list of 616
published and unpublished bibliographic
references that relate to the ages,
elevations, and deformation of marine
terraces and of the Pleistocene fossil
record associated with them, for the
Pacific Coast between the Palos Verdes
Peninsula in southern California and
Punta Banda in northern Baja California.
More than 100 of the citations in the
master bibliography in Appendix I,
including published papers, guidebooks,
and maps, are now scanned and uploaded
to the SCE database. We had located
information on more than 1,500
Pleistocene fossil localities in the project
area, based on the LACMNH, SDNHM,
SDSU, UCLA, UCMP and USGS fossil
collections. We acquired the locality
sheets, and some of the fossil lists, for 331
localities from the LACMNH: these
included sites from Baja California to the
Palos Verdes Peninsula.
We also
acquired a list of over 500 fossil localities
that are archived at UCMP, and we are
aware of more than 600 localities and
associated faunal lists on file at the
SDNHM. We had also compiled more
than 130 localities with shoreline angle
data and elevations (prior to the new
Camp Pendleton effort), and completed a
master spreadsheet with all of these data.
Finally, the locality data were placed in
GIS formatted files. All of the above are
attached as Appendices contained on a
CD.
Figure 41. Surveyed shoreline elevations for the
lowest four emergent terraces north of SONGS to
Newport Beach. Tentative correlations shown by
the colored bars
September 2013, Rev. 0
At that time, there remained significant
data gaps in both the compilation of
available data as well as the determination
of high-resolution terrace elevations and
ages for the vicinity of SONGS. Towards
that end, we conducted extensive field
work to map and survey marine terraces
Page 39 of 57
Table 3. Average elevations of terraces mapped on Camp Pendleton, along with the elevations of the terrace
sequence mapped on San Clemente Island (Adler, 2003) and along the San Diego County coast, as presented in
Kern & Rockwell (1992). Note the remarkable similarity in terrace elevations and spacing.
from the south side of Camp Pendleton northwestward to Newport Beach, as presented in this
report. We acquired five additional corals from terrace localities in northern San Diego and
southern Orange Counties, and submitted them for U-series analysis at the University of
Minnesota. We also collected samples for cosmogenic burial ages, and analysis of these samples
is being completed at the PRIME lab (Purdue University) through the Quaternary lab of Lewis
Owen at Cincinnati University; although the aluminum analysis portion of these new age data is
pending. The results of these new dates are presented in Appendix XVIII, and their significance
and age interpretations are discussed in the interpretation section of this report (Section 5.0).
September 2013, Rev. 0
Page 40 of 57
4.1
Summary of Terrace Observations
1) Uplifted emergent marine terraces appear to have been uplifted at a constant rate along
the entire coast from north of Mt. Soledad in San Diego to at least the northern boundary
of Camp Pendleton in the vicinity of SONGS, assuming the terraces are correctly
correlated. The first and second emergent terraces, preserved or exposed only locally
along the northern San Diego County coast (Torrey Pines to Camp Pendleton) and from
La Jolla to Point Loma in the south, have consistent shoreline angle elevations of 9 to 11
m for the Bird Rock Terrace and 22 to 23 m for the Nestor Terrace. U-series dates
obtained from corals collected from these two terraces indicate ages of ~80 and ~120 ka,
respectively (Ku and Kern, 1974; Kern and Rockwell, 1992).
2) Intermediate terraces within and south o f Camp Pendleton are locally preserved at
estimated elevations of 32-34 m, 46-48 m, ~55 m ~60 m, ~68 m and approximately 84 m
(Kern and Rockwell, 1992) and show no significant coast-parallel deviation in elevation.
At Camp Pendleton, terrace shorelines measured as part of this study have elevations of
34.6 m, 45+1 m, 53+2 m, 63+1 m, 73+2.5 m, and 85+2.
3) The long-term constancy in uplift for the entire coastline is demonstrated by the creation
of a new hillshade model (Figure 41) from vintage (1950s year range) topographic maps,
which demonstrates that the ninth through 12th emergent terraces of Kern and Rockwell
(1992) (referred to as the Claremont, Tecolote, Linda Vista, and Tierra Santa terraces)
maintain nearly constant elevations of approximately 93-98 m, 106-108 m, ~114 m, and
122-124 m, respectively. Newly surveyed elevations collected at Camp Pendleton are
consistent with those published by Kern and Rockwell (1992). Higher terraces are also
locally preserved.
4) North of SONGS, a low terrace is only sparingly preserved as either a narrow bench or as
isolated exposures from San Clemente to Newport Beach, and the elevation of the
shoreline angle of this terrace is between 8.5 and 9 m where good exposures are
measurable. A possible exception to this statement is the surveyed shoreline angle at San
Clemente State Beach, where the surveyed elevation is slightly higher, at 12.1 m in a
canyon mouth, possibly due to canyon run-up.
5) A terrace is preserved discontinuously from San Clemente to Newport Beach, with
numerous fore-edge elevations surveyed between about 14 and 20 m. Shoreline
elevations interpreted for this terrace vary between about 21 and 24 m, except for a single
shoreline angle elevation in San Clemente (Marblehead development) measured at 26 m,
as presented earlier in this report. Between Dana Point and Crystal Cove, this terrace is
partially removed by erosion or obscured by urban developments and is well exposed at
Crystal Cove. North of Crystal Cove, elevation of the shoreline angle was measured at 21
m during grading of a residential development.
6) The third and fourth prominent emergent terraces also appear to be well preserved north
of SONGS, although shoreline angle exposures are sparse in this area due to urban
development. Near San Clemente, the shoreline angle of these two terraces are at
approximate elevations of 36 m and 48 to 50 m, which are similar to the shoreline
elevations measured at Newport Beach, where Grant et al. (1999) measured elevations of
September 2013, Rev. 0
Page 41 of 57
32 to 36 m and 49 to 53m which they attributed to the second and third emergent terraces,
respectively.
7) New U-series dates determined for this project all have issues with open systematics.
Five of these dates show elevated initial ratios that range from 1.185 to 1.81, compared to
sea water values of 1.145-1.15, indicating addition of continentally derived 234 U. One
sample (Loc. 241) has an anomalously low initial ratio, suggesting 234 U loss. The 232 Th
content of some specimens is anomalously high, which is also an indication of open
systematics, such as in sample 2966-73270, where the 232 Th value is nearly 1.7 million,
resulting is a very low 230 Th/232 Th ratio. In short, most corals dated as part of this study
can be interpreted as likely MIS stage 5 in age, but are insufficient to unequivocally
assign them to specific substages. One specimen, collected from the north side of
Batiquitos Lagoon yielded a very old 230 Th age (sample 3646-70191), but also exhibited
open systematics, so the precise age of this sample is questionable. Of the U-series ages
published in Grant et al. (1999), most show open system characteristics with high initial
ratios, with the exception of the coral dated from SDSU locality 3812 (sample FP-28),
which exhibited only slightly elevated initial ratios and likely yielded a reasonably good
age estimate for that locality. The age of about 121-124 ka for this sample correlates this
terrace to MIS 5e, consistent with the abundant tropical elements in the fauna recorded
for this (Peska, 1976) and nearby localities (e.g., Bruff, 1946; Kanakoff and Emerson,
1959).
8) For the open system dates, the first emergent terrace at Solano Beach and Newport Beach
(both at 8.5-10 m elevation) are likely MIS 5a (samples 2966-73270 and IOC-241,
respectively).
9) The first emergent terrace on Camp Pendleton north of Horno Canyon contains a fauna
with several extralimital northern species (Appendix XIV). The back-edge of this terrace
is exposed at Stuart Mesa with a surveyed elevation of 10.4m. The fore-edge of this
terrace is exposed discontinuously northward from Stuart Mesa to the location of the
fossil locality north of Horno Canyon (SDSNH localities 6655 et al.) at elevations of 6-9
m, although the shoreline angle is buried north of Stuart Mesa by a thick sheet of alluvia l
fan deposits. The cool-water fauna at this location correlates this terrace to late stage 5,
and most likely MIS 5a based on its elevation (Appendix XIV).
10) There are abundant platform elevation data that have been either measured by or
recovered from historic geotechnical reports by Lisa Grant Ludwig for the area in and
around Newport Bay. There are also several critical fossil localities that bear on the ages
and elevations of terraces in this area. LACMIP localities 66-2 and 68-A, 68-B
(Kanakoff and Emerson, 1959) have reported platform elevations of 18 to 19.5 m, with as
much as 7 m of marine terrace deposits and another 1-2 m of fluvial (?) and/or alluvial
soil deposits above the marine deposits. SDSU locality 3812 (sample FP-28) was
collected nearby and exhibits similar elevations, although the original collector (Peska,
1976) estimated an elevation (not surveyed) of about 80 feet (24 m) for the main fossil
horizon immediately above the platform.
September 2013, Rev. 0
Page 42 of 57
11) Elevations of the next higher terrace platform on the East Bluff of Upper Newport Bay
rise to about 26-27 m very close to the location of the Peska (1976) and Kanakoff and
Emerson (1959) fossil localities, and then rise to an obvious shoreline and paleo-sea cliff
with surveyed platform elevations that ranged from 29-30 m (recorded in historic
surveyed geotechnical borehole logs). The terrace deposits overlying this platform are
very thin, as little as a meter thick.
12) An inset terrace of likely estuarine- marine origin preserved below Galaxy View Park
yielded a surveyed platform elevation of 19.7 m. The shoreline angle elevation for this
terrace is likely only slightly higher, and is estimated at between 21 and 22 m.
13) Surveyed elevations for the next higher platform at Galaxy View Park range from 25 to
27 m and are clearly on a separate terrace from the lower terrace below Galaxy View
Park (Figure 37, photo). The elevation of this upper platform is fairly regular along the
bluff, which is roughly parallel to the shoreline preserved east of Upper Newport Bay.
14) Immediately southwest of Galaxy Park, the terrace platform elevations recorded in
historic geotechnical reports drop to 18.5 to 21 m (Figure 38). The area with lower
platform elevations contains LACMIP localities 68-A and 68-B of Kanakoff and
Emerson (1959). The exact locations of these collecting spots cannot be determined from
the original publication, although they are reported as being along the bluff where the
18.5 to 21 m elevations have been determined. The fauna from this locality is distinctly
tropical and correlates well with the faunas from LACMIP localities 66-2 and 136 in
terms of water temperature/environment and species composition.
15) The first emergent terrace, described by Powell (2001) as “a previously misunderstood
late Pleistocene, cool water, open coast terrace at Newport Bay”, is exposed adjacent to,
and north of, the mouth of Newport Bay. This “cool water open coast terrace” has an
exposed shoreline angle at an elevation of 8.5 m near the Taco Bell/Pizza Express fast
food restaurant located at north 1400 Pacific Coast Highway in Newport Beach, Figure
36). The terrace is clearly distinct from the 20-22 m terrace that contains the tropical,
warm-water fauna previously recorded from near Galaxy View Park (i.e., LACMIP
localities 68-A and 68-B).
16) Another terrace on the east side of upper Newport Bay reaches an elevation of at least 35
m. A second, lower terrace appears to be preserved adjacent to this terrace, as interpreted
from 1952 and 1953 aerial photographs. Both surfaces are mapped as a single terrace by
Grant et al. (1999), and by Vedder et al. (1957, 1975).
17) A higher, broad terrace with shoreline elevations reported at 49 to 53 m is present above
the lower terraces that have shoreline elevations of 32-36 m and 19-22m (Grant et al.,
1999).
These observations are presented as several interpretations in the next section.
September 2013, Rev. 0
Page 43 of 57
5.0
PLAUSIBLE INTERPRETATION OF TERRACE DATA BASED ON
PUBLISHED AND NEW DATA
Flat uplift of San Diego County - Marine terraces are uplifted but unfolded from at least
Claremont Mesa in San Diego northward to SONGS. The evidence for this interpretation
appears solid, and implies no recognizable folding or deformation has occurred due to movement
on the inferred Oceanside Blind Thrust (OBT). In turn, this implies that the OBT does not
extend beneath the San Diego County coastline. This assertion is based on expected folding over
a blind thrust source, where slip increases from zero near the rupture termination to a maximum
value near the middle of the rupture. In the blind thrust model of Rivero et al. (2000) and Rivero
and Shaw (2011), the OBT is divided into two segments. Independent rupture of these segments
should produce differential uplift of the coast, as shown in Figure 42. Such differential uplift is
not observed (Figure 40). Alternatively, if the entire OBT were to fail repeatedly in large events,
with slip decreasing to zero at the endpoints of the OBT, then uplift should be higher in the
vicinity of Oceanside than to the south in San Diego. Observation are that the terraces are
uplifted only slightly more where the Rose Canyon fault makes a bend through Mt. Soledad, and
they are depressed in the vicinity of San Diego Bay (Kern and Rockwell, 1992). In addition, the
onshore Eocene strata are virtually flat- lying for most of San Diego County northward to the
Oceanside area, indicating that they have not been affected by folding over the last 40 to 50
million years. This observation also calls into question the assertion that a Miocene detachment
fault extends eastward beneath the coastline under coastal San Diego. North of Oceanside,
Tertiary strata are folded, and the Cristianitos fault is recognized as a high angle normal fault that
accommodated extension in the development of the Capistrano embayment. South of Oceanside,
the lack of Tertiary deformation suggests that extension may have been limited to the offshore
area. In summary, the Quaternary pattern of uplift along with the lack of Tertiary or quaternary
folding does not support the OBT model; the essentially flat uplift of San Diego County marine
terraces is consistent with the rift-shoulder uplift model of Mueller et al. (2009).
September 2013, Rev. 0
Page 44 of 57
Figure 42. Predicted elevation of terraces based on repeated rupture of the OBT, based on the
geometry defined by Rivero et al., 2000 and Rivero and Shaw, 2011. The terrace data represent the
starting point of the terrace study, as terrace elevations were determined from previous studies.
Uplift of Terraces North of SONGS - North of SONGS, there are at least three possible
interpretations based on the existing data. These are: (A) The flat-terrace hypothesis, where the
first several emergent terraces are uplifted but are essentially flat from San Diego to Newport
Bay and northward, including around the north end of the San Joaquin Hills (SJH). In this
interpretation, the SJH represent an older structure that is simply being exhumed during regional
coastal uplift. There is a fold that is well expressed structurally and geomorphically in the
northern SJH (Hughes, 1994). The fold accommodates uplift relative to subsidence in the
southern Los Angeles basin. (B) Terraces are folded or faulted along various strands of the
Pelican Hills and/or faults associated with Newport Inglewood fault zone. This interpretation
would combine the 18-25 m MIS 5e terrace (with a tropical fauna) and the associated abrasion
platform with the 26-30 m terrace, both of which were subsequently covered by a thin veneer of
fluvial or marine deposits and development of a soil horizon. The 25-27 m elevations west of
Newport Bay would then be interpreted to step down to the 18-20 m elevation level coincident
with the terrace platform level at LACMIP localities 68-A and 68-B that contains the tropical
fauna. This would imply an active Pelican Hills or related fault structure, and there does appear
to be a step in the topography from analysis of vintage 1952 aerial photography. (C) A third
plausible model is progressive folding of the older, higher marine terraces in the San Joaquin
Hills, with reduction in rate or cessation of recognizable folding sometime in the middle to late
Quaternary, before formation of the first and second emergent terraces that we measured at about
8-9 and 21-23 meters elevation along the coast, respectively. The underlying Tertiary strata are
strongly folded, so continued Quaternary folding is a reasonable hypothesis to test.
Interpretation A – Flat terrace hypothesis – This model was developed because of the apparent
lack of a change in terrace elevations from San Diego County northward to Newport Bay, as
measured at the coast. Additional analysis of platform elevation data near and around Upper
September 2013, Rev. 0
Page 45 of 57
Newport Bay extended this interpretation to include the region from the coast to Upper Newport
Bay, as discussed below. Northeast of Newport Bay, the terraces are apparently folded down to
the north/northeast across an axial surface or fold, and it is this structure that is interpreted to
allow for the differential uplift between the Los Angeles basin and the coast. In this
interpretation, the SJH are an older structure that is simply being exhumed during regional
coastal uplift.
A critical aspect of this and the other interpretations is an understanding of sea level history. It is
generally accepted that sea level was higher during MIS 5e (C happell, 1983; Bloom et al., 1974;
Muhs et al. 1994, and numerous more recent works). Likewise, warmer-water conditions existed
farther north and south, which is reflected in the presence of both southward ranging and
extralimital southern species in substage 5e faunal assemblages along coastal southern Ca lifornia
(Kennedy et al., 1992; Kennedy, 2000). In contrast, southern California MIS 5a and 5c faunas
typically contain cooler-water faunal elements that suggest temperatures currently present today
north of Point Conception in the southern Oregonian faunal province. Furthermore, paleo-sea
level estimates for MIS 5a and 5c vary as a function of what part of the world is considered,
whether the estimates are based on erosional abrasion platforms or constructive tropical reef
crests (Muhs et al., 1992, 1994; Bloom et al., 1974). The method used to estimate relative paleosea level will thus differ, depending on which scenario is being investigated (Bloom and
Yonekura, 1985). For coastal California, Muhs et al. (1994) estimate a paleo-sea level of -1 m
for MIS 5a relative to an elevation of +6 m for MIS 5e. This is based on the observations and
dated terrace pairs at many low uplift rate localities along the Pacific Coast where the terrace
spacing between the MIS 5a and 5e terraces is only 10 to 15 m. Using the Barbados estimate of
+6 m for MIS 5e and -16 m for MIS 5a requires a minimum spacing of 22 m in areas of no uplift.
For uplifted regions, this spread in elevation will be greater. It is clear that relative sea level
estimates based on coral reef tracts do not work for the Pacific Coast, and that local paleo-sea
levels should be used.
MIS 5c is apparently only rarely preserved along much of the southern California and northern
Baja California coast. At Punta Banda, Rockwell et al. (1989) report U-series ages on corals and
hydrocorals for the Lighthouse and Sea Cave terraces at 79-89 ka and 115-160 ka, respectively.
However, many of these dates were conducted on the hydrocoral Stylaster californicus, which
exhibited significant open-systematics, including elevated initial 234 U/238 U ratios. In contrast,
ages determined from the small solitary coral Balanophyllia elegans yielded excellent closedsystem ages of about 78 and 120-124 ka, respectively (also reported in Muhs et al., 1994),
correlating them to MIS 5a and 5e, respectively. Between these two terraces, a narrow terrace is
only locally preserved and was interpreted to represent MIS 5c, although the terrace is not
directly dated at that locality.
In San Diego, the Bird Rock and Nestor terraces, also locally dated to MIS 5a and 5e,
respectively (Muhs et al., 1994), have elevations of 9 to 11m and 22 to 24 m, respectively (Kern
and Rockwell, 1992). The predicted elevation for MIS 5c, using the relative elevation of the
inferred Punta Banda MIS 5c terrace as a guide should be in the range of 14 m. There are no
terraces that have been documented at this elevation in all of San Diego County except where the
MIS 5a terrace ramps up to the Rose Canyon fault in La Jolla Valley on the flank of Mt. Soledad
(and the MIS 5e also rises above its average elevation).
September 2013, Rev. 0
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Between San Diego and Newport Bay, the relative elevations of the MIS 5a and 5e terraces are
consistent, assuming that the first two regional terraces recognized at 8-11 m and 20-24 m
correlate to MIS 5a and 5e, respectively, which is the interpretation for this model. Of note,
there is only the one locality where we have documented a shoreline angle elevation of close to
14 m at 12 m elevation in the San Clemente State Beach.
The MIS 5c terrace is also reported from the Transverse Ranges (Rockwell et al., 1992; Kennedy
et al., 1992) and from farther north in Central California near Santa Cruz (Bradley and Griggs,
1976), but its occurrence appears to be rare compared to the MIS 5a terrace. This may be due to
its subsequent erosion during the MIS 5a highstand, which appears to have been about twice the
duration of MIS 5c, based on the worldwide set of U-series ages. The MIS 5c terrace appears to
be absent in San Diego County, and may be absent or unmappable in coastal Orange County as
well, with San Clemente State Beach being a possible (albeit low elevation) exception. The MIS
5e and 9 terraces, in contrast, are typically (but not always) fairly broad, possibly because these
interglacials were longer than many and sea levels were higher.
The reason for the preceding discussion is terrace spacing. As uplift rates increase, the vertical
separation between terraces is expected to increase. That is, for any given uplift rate, the
predicted elevations of MIS 5 terraces can be estimated, as can older terraces that correlate to
MIS 7 and 9, and so forth. In San Diego, the uplift rate from the elevation of the MIS 5e Nestor
terrace is estimated at about 0.13-0.145 m/ka, based on a 22-24m elevation, a paleo-sea level of
+6 m, and an age of 117-126 ka. The 117 ka is a justifiable younger age limit because many Useries dates from the Pacific Coast yield ages in that range. The older limit is based on well
constrained ages of coral reef crests worldwide. For the purposes of discussion, we use an
average uplift rate for San Diego County of 0.14 m/ka (mm/yr). Using this uplift rate, the
predicted elevation for the MIS 5a terrace shoreline is 10 m, assuming a -1 m paleo-sea level
(Muhs et al., 1994) and an age of 78 ka (younger limit of closed-system U-series ages from the
Pacific Coast; Muhs et al., 1994). Similarly, MIS 5c (~103 ka), if present, should be present at
about 14.5m, and the MIS 7 and 9 terrace shorelines should be present at about 30-33m (assumes
-1 m paleo-sea level (Rockwell et al., 1989) and an age range of 210-230 ka) and 48-50 m
elevation (assumes +4 m paleo-sea level (Rockwell et al., 1989) and an age of 320-330 ka).
Remarkably, these are the elevations of the first four recognized emergent terraces in San Diego
County northward into Orange County, and as far as Newport Beach if correlations are correct.
At an uplift rate of 0.2 m/ka, the MIS 5a, 5e, 7, and 9 terraces yield predicted shoreline
elevations of about 15 m, 30 m, 41 m and 69 m, respectively, and with a higher uplift rate, the
terrace spacing will diverge further. As the surveyed elevations along coastal San Diego and
southern Orange Counties appear to match well with a constant uplift rate of about 0.14 m/ka,
model A assumes that the terraces at a common elevation along the coast are correlative, as there
is only very minor divergence from these average elevations. The small differences can be
explained by either the expected small variations in shoreline angle elevation that can be
observed in the modern coast: a 1-2 m variation in the modern shoreline angle has been noted in
many studies (Rockwell et al., 1989, Muhs et al., 1994) as well as in this study. Alternatively,
there may be minor amounts of local deformation associated with warping or faulting, although
that is not required.
September 2013, Rev. 0
Page 47 of 57
Newport Bay represents a different problem with its own caveats. Unpublished subsurface data
by L. Grant Ludwig, summarized in Grant et al. (1999), provide an excellent set of platform and
shoreline elevation data to explore alternative hypotheses. For hypothesis A (model A), there are
several critical observations that need to be elucidated, especially as the reported elevations
relate to fossil localities and U-series ages.
First, a note on the fossil localities reported by Kanakoff and Emerson (1959) and Peska (1976).
In all cases, localities are not as well described in terms of their locations as they might be with
modern GPS capabilities. Nevertheless, critical points of discussion are both the reported
platform elevations and their inferred ages, as determined by their faunal content and three Useries ages reported in Grant et al. (1999). The faunas at all three localities contain tropical
(extralimital southern) species that indicate warmer than present water conditions at the time of
terrace formation and deposition. The U-series ages presented in Grant et al. (1999) yield
consistent dates between 120 and 125 ka, consistent with correlatio n to MIS 5e. These two
aspects, the warm-water fauna and the MIS 5e U-series dates, are consistent and argue strongly
that all three localities are associated with the MIS 5e sea- level high-stand.
LACMIP locality 66-2 is northeast of Upper Newport Bay and has a reported surveyed platform
elevation of 60 to 65 feet (18-19.5 m). The location of locality 66-2 is not well described, but
based on photographs presented in Kanakoff and Emerson (1959) and an unpublished plane-table
map generated for the authors (Kanakoff and Emerson), our collective best estimate for the
location is shown on Figure 38. Similarly, Kanakoff and Emerson (1959) report abundant
tropical species from LACMIP localities 68-A and 68-B, which are shown on their map on the
west side of Upper Newport Bay, also with a reported platform elevation of 60-65 feet (18-19.5
m). In this area, Grant Ludwig recovered platform elevations from geotechnical boring data that
agree very well with a platform elevation of 18-21 m. The marine deposits at LACMIP localities
66-2 and 66-10 and vicinity are reported to be as thick as 22 feet (6.7 m) with another several
feet of non- marine cover (possibly fluvial, colluvium and soils); at localities 68-A and 68-B, they
are 12 to 18 feet thick (Kanakoff and Emerson, 1959). Hence, the top of the marine strata that
contain tropical fauna reaches an elevation of as much as 24-25 m at the reported localities, with
a slightly higher surface elevation.
The Peska (1976) localities, FP-28 and FP28a, are not adequately described by modern standards
(Peska, 1976). He reported a tropical fauna collected from “the same strata” as reported in
Kanakoff and Emerson (1959) at an elevation of about 80 feet (24.3 m), although he did not
survey his localities or elevations. Peska’s localities are referenced to a residential area that had
been graded and developed, whereas Kanakoff collected prior to development or grading. Peska
describes a rich stratum loaded with fossils overlying other layers with a different fauna. These
overlaid a “scattered sandstone and cobble layer”, which in turn overlaid a stratum of clay with
boring clams “trapped” in their burrows. Below the clay, which “ranges up to 3 feet or more in
thickness”, he describes a “coarse, gray sand and clay layer below part of the clay stratum”.
From his description, it is not clear if he exposed the abrasion platform but a similar coarse gray
sandstone is visible today in exposures below the East Bluff terrace platform near Peska’s
locality, so it is likely that he collected from just above the terrace platform.
It is from the Peska collection that a coral was recovered and dated by Grant et al. (1999).
Unfortunately, the exact context of the coral is no t known, nor its actual elevation surveyed. It is
September 2013, Rev. 0
Page 48 of 57
not clear from Peska’s (1976) sketch in his paper if he reached the abrasion platform. Peska
described the location to Grant Ludwig in 1997 and sent her a hand drawn map that cannot be
geo-referenced now, due to changes in infrastructure since the 1970s when the fossils were
collected. Peska’s sites were inland, some distance from the bluff. LACMIP locality 136 was
collected from the bluff face directly above Upper Newport Bay. This locality is described as
the “Anomia Bed: stratum from 14 to 22 feet in thickness over 500 feet in length: 15 feet below
adjacent airport runway. The locality is on the east bluff above Upper Newport Bay: city of
Newport Beach; about ¼ mile due west of LACMIP locality 66. =LACM VP locality 4422.” A
surveyed elevation is not given, but if the top of the marine strata is 15 feet below the runway
(elevation at about 100 feet, or 30 m), then the base of the marine strata could be as low as 18-19
m, similar to the reported base of marine strata at LACMIP locality 66-2 of Kanakoff and
Emerson (1959), which they surveyed with a plane table. However, geotechnical boring data
collected by Grant Ludwig shows a platform elevation of 30.2 m at the runway (99- foot platform
next to the 100- foot elevation contour) indicating minimal marine cover not far to the east of the
presumed Peska locality. An
examination of the faunal
assemblage from LACMIP
locality 136 for this study
revealed an abundance of
tropical species of marine
bivalve
and
gastropod
mollusks, consistent with its
correlation with the other
nearby localities that contained
a tropical faunal element.
In summary, tropical marine
invertebrate faunas that date to
MIS 5e are present in the
Upper Newport Bay area and
associated
with
abrasion
platform elevations between 18
and 22 m, and fossil elevations
as high as 24-25 m.
Figure 43. Cross-sections (locations on Figure 38) showing the
platform elevations determined from geotechnical boring data.
September 2013, Rev. 0
Figure 38 shows the abrasion
platform elevations determined
from the geotechnical boring
data. The elevations on the
east side of Upper Newport
Bay appear to rise to at least
26.5 m, and higher eastward to
a shoreline elevation of ~30 m
near the dirt road east of the
landing strip, southeast of
which the topography rises
rapidly. A cross-section across
Page 49 of 57
Upper Newport Bay, section A-A’ (Figure 43), delineates two possible terraces levels – one at
about 18-22 m, and another at 25-30 m, with the elevations of the higher terrace rising eastward
to the 30 m shoreline. Cross-section B-B’ on the west side of Newport Bay shows a nearly flat
terrace platform at 25-26 m, with the trend of the data parallel to the 30 m shoreline located on
the east side of Upper Newport Bay. This terrace elevation extends south to the vicinity of
Galaxy View Park, where there is an inset terrace with an abrasion platform surveyed as high as
20.7 m and an estimated shoreline angle elevation of 21-22 m. Cross-section B-B’ (Figure 43)
shows this relationship, but the lower ~22 m terrace is clearly inset below the upper, 25-26 m
terrace. Cross-section B- B’ also shows that the elevation of the abrasion surface drops rapidly
from 26.7m to about 20-22 m over a distance of about 200 m, and then slopes gently southward
to an elevation of 18-19 m over a distance of nearly a kilometer. Considering that the elevation
of the 21 m inset terrace below Galaxy View Park is nearly identical to the measured platform
elevations only a few hundred meters to the west argues that these are likely on the same terrace
platform. LACMIP localities 68-A and 68-B with tropical faunas (Kanakoff and Emerson, 1959)
are located along the bluff where the abrasion platform elevations are measured at 18 to 20 m,
indicating that this is the elevation level that is best associated with the MIS 5e tropical fauna.
Cross-section C-C’ (Figure 43) along the eastern side of Newport Bay also shows elevations
consistent with two terrace levels around Upper Newport Bay, rising southwest to higher terrace
levels at about 35 m and 48-49 m. Farther southwest at the coast in Newport Beach, a terrace
has a surveyed shoreline at an elevation of 21 m (69 feet), so the higher terraces are
geomorphically distinct from the 21- m terrace level at the coast.
Model A combines all of the terrace elements in Upper and Lower Newport Bay that reach a
maximum elevation of about 21-22 m and represent a single high-stand of the sea. The presence
of tropical faunas associated with this terrace level, along with the U-series ages presented by
Grant et al. (1999) argue that this is the MIS 5e terrace. In this model, the 21-22 m terrace in
Upper Newport Bay is interpreted to be inset into (below) an older (presumably MIS 7) platform
that reaches a maximum elevation of about 30 m southeast of the old landing field shown in
Figures 38 and 44. If correct, then these 21-22 m terrace remnants all correlate to the Nestor
terrace in San Diego, which has an elevation of 22-24 m throughout San Diego County. The
older terrace remnants associated with the MIS 7 highstand are preserved on both sides of Upper
Newport Bay, but may disappear farther northwest over a fairly short distance, as tropical faunas
are reported from a number of locations to the west in the subsurface, all with platform
elevations below 22 m (K.R. LaJoie, unpublished data). The “nose”, or promontory, of the San
Joaquin Hills was therefore located northwest of Newport Bay at MIS 5e time, rather than to the
southeast, as presented in the Grant et al. (1999) model.
Supporting this interpretation is the presence of the 8.5 m shoreline in Newport Beach, which is
clearly distinct from the next higher, 20-22 m terrace, and is consistent with the predicted
elevation (with normal terrace shoreline elevation variability) for the MIS 5a terrace. In apparent
opposition to this interpretation, Powell et al. (2004) reported a tropical fauna at the inland
Fletcher Jones Motorcars site northeast of Upper Newport Bay (OCPC localities 2601-2606).
Reported elevations of these localities ranged between 7 and 11.2 m. Using the 8.5 m elevation
and assuming it to be the MIS 5a terrace shoreline, the MIS 5e shoreline should be at about 2021 m, indistinguishable from the observed shoreline at 21-22m.
September 2013, Rev. 0
Page 50 of 57
Figure 44. Cross-section across Upper Newport Bay, with an inset terrace fore-edge as
low as 18 m and the shoreline at 21-22m, rising to a platform at 26.7-30 m on the east
bluff, and with lower elevations to the west.
If model A is correct, then the MIS 5a and 5e terraces have been uplifted at about the same rate
from the coast inland to at least Upper Newport Bay, maintaining a shoreline elevation of about
21-22m. This implies no differential uplift at the coastline in this area for the past ~120 ka,
although inland from the coast, the terrace surface does appear to fold over to the northeast in the
vicinity of John Wayne Airport.
Hypothesis B (model B) ties the tropical faunas and coral dates from fossil localities in Upper
Newport Bay to the 30 m shoreline rather than the 21-22 m shoreline, as determined from
geotechnical boring log data reported in Grant et al. (1999). In this model, the thick
accumulation of MIS 5e deposits simply filled in a pre-existing paleochannel such that the base
of the deposits may be well below the expected and actual elevation of the abrasion platform,
had it been cut during a sea level transgression. The apparent abrasion platform reported by
Kanakoff and Emerson (1959) is therefore interpreted as an old fluvial erosional feature.
Kanakoff and Emerson (1959, p. 17) described “the irregular surface of the terrace platform” (p.
17) and ascribed it to either surveying errors or “More likely, the platfor m was channeled by
currents or by some other means before or during deposition of the sediments”.
In this model, the step-down in terrace elevation along cross-section B-B’ is interpreted as a tight
fold or fault, rather than a shoreline and paleo-sea cliff (as in model A). Geologic maps (e.g.,
Morton and Miler, 1981) show several dotted (i.e., buried) faults in the area, probably associated
with the Pelican Hills fault system, or abandoned strands of the Newport Inglewood fault system,
so the presence of a fault is plausible. Presumably in this model, the southwestern increase in
terrace elevation from 30 m adjacent to Upper Newport Bay to at least 35 m closer to Newport
Beach along cross-section C-C’ is explained by upwarping of the platform towards the fault.
This apparent upwarping of Quaternary terraces coincides with the Newport anticline described
by Hughes (1994) in pre-Quaternary rocks beneath the terrace platforms. However, the 35 m
elevation coincides with a similar elevation terrace, which recurs repeatedly southeast along the
coast to San Diego, arguing against crossing of a fault.
September 2013, Rev. 0
Page 51 of 57
Evidence supporting this interpretation was observed during our recent examination of 19521953 stereo-photos of the Newport Bay area that showed a tonal lineament (and elevation
change?) on the western side of the Bay, south of Galaxy View Park, that coincides with both the
change in elevation of the platform from 18-19 meters to 25-27 meters that is observed in the
geotechnical boring log data collected by Lisa Grant, a nd the inferred projection of a strand of
the Pelican Hills Fault System as shown on the CGS Geologic map of Orange County (Morton
and Miller, 1981). This could also be interpreted as a paleo-shoreline.
Problems with this model include the lack of an obvio us reported fault that crosses the southwest
side of Newport Bay, the lack of variation in terrace spacing along the coast from Newport Bay
southeast to San Diego, the apparent coincidence in platform elevations in Upper Newport Bay
and Galaxy View Park with the platform elevations at LACMIP localities 68-A and 68-B, as well
as the shoreline elevation of the terrace between Newport Beach and Crystal Cove State Park.
Further, if the lower (20-22) platform elevations in Upper Newport Bay upon which the tropical
faunas are clearly present represent a filled fluvial channel, why are there no remnant fluvial
deposits reported in any of the studies? There are abundant non- marine fossils reported from the
East Bluff terraces, including LACMIP locality 66-2. According to Kanakoff and Emerson
(1959, p. 6) “This site yielded an abundance of vertebrate remains, including fish, bird and
mammal bones, numerous invertebrates, and even plant remains”. However, richly fossiliferous
marine faunal assemblages often contain at least a minor element of vertebrate fossil species (G.
L. Kennedy, personal observations). If the paleo-channel had simply been drowned, it is highly
likely that some fluvial deposits would be preserved, as observed elsewhere in southern and
central California (there are numerous examples of this). Unfortunately, none of the publications
about non- marine fossils contain good descriptions of the geology and the area has been
developed, so we cannot evaluate the paleo-channel hypothesis with existing data. Another issue
is that none of the tropical faunas are described at elevations that are high enough to be clearly
attributed to the 30 m shoreline and associated platform in Upper Newport Bay. The LACMIP
locality 66-2 fauna is described as being in the marine section that is up to 6.7 m (22 feet) thick
above an 18 m (60 foot) platform. That places the top of the marine section as high as 24.7 m.
The gently sloping platform that clearly rises to the 30 m shoreline in Upper Newport Bay has
platform elevations that range from 26.7 to 30 m east of the bay and 24.1 to 25.9 m southwest of
the bay. Set below this level on both sides are platform elevations down to 18 m, with a
shoreline exposed below Galaxy View Park at 21 to 22 m. It is difficult to reconcile why none of
the tropical faunas are reported to have elevations as high as the 26.7-30 m terrace southeast of
Upper Newport Bay, where the terrace deposits are only a thin veneer. Location information for
sample FP-28 (Grant et al., 1999), which yielded an age of 122 ka, is not precise enough to
determine if the sample was collected at a 24 m shoreline, or at 24 m elevation on the platform
below a ~30 m shoreline.
Hypothesis C (model C) - folding of the older, higher marine terraces in the San Joaquin Hills,
with reduction in rate or cessation of recognizable folding sometime in the middle to late
Quaternary, before formation of the first and second emergent terraces that we measured at about
8 to 9 and 21 to 23 meter elevations along the coast, respectively. In this interpretation, the 8-10
m and 21-23 m terraces correlate from San Clemente northwest to Newport Beach and northeast
to Upper Newport Bay at about the same elevation, but the higher terraces show folding
deformation consistent with the model published by Grant et al. (1999).
September 2013, Rev. 0
Page 52 of 57
The best support for this model comes from the well constrained elevation of the 30 m terrace in
Upper Newport Bay and the apparently higher elevation of possibly the same terrace closer to
the coast. In fact, it is difficult to reconcile the observation of a 30 m terrace that is spatially so
close to the 35 m platform elevations, as noted in Figure 43 that is based on the geotechnical
boring data. The 32-35 m elevations are all platform elevations and the shoreline elevation must
be slightly higher, as they are up to a couple hundred meters from the shoreline. If these are not
the same terrace, then there is a problem with both terrace spacing as well as the apparent
presence of an additional terrace level that is not seen elsewhere. Grant et al. (1999) recognized
this problem and proposed that the 5c terrace might be expressed locally, and thereby complicate
correlation and interpretation of the terraces, although based on the terrace spacing, this is not
likely. The next higher terrace platform has elevations at 47-49 m and the shoreline elevation is
probably higher, as these elevations are taken near the fore-edge. Although additional work
needs to be done to determine if other geotechnical data can be brought to bear on the back-edge
elevation for this terrace, at face value, it is likely to be higher than the shoreline elevation (4850 m) recorded for the fourth terrace to the southeast.
These observations, taken at face value, suggest that folding (or significa nt faulting) in the
northwestern San Joaquin Hills was active until at least MIS 7 (210-230 ka), but may have
slowed dramatically or ceased by the time of the MIS 5e highstand (~117-128 ka). This could
also explain why the higher terrace shoreline elevations reported in Grant et al. (1999) do not
match well with the surveyed shoreline elevations determined for this study from higher terraces
on Camp Pendleton, and those reported by Kern and Rockwell (1992) farther south in San Diego
County.
In closing, it is clear that resolution of these various models, or others that may also be supported
by the data, will require additional work. Of the models presented, models A and C have no
obvious contradictions and are tentatively preferred at this time, although model B cannot be
precluded.
September 2013, Rev. 0
Page 53 of 57
6.0
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