Trenching the Rose Canyon Fault Zone San Diego, California

Home , Rose Canyon Fault, San Jacinto Fault Zone

TRENCHING THE ROSE CANYON FAULT ZONE SAN DIEGO, CALIFORNIA

E. R. Artim and D. Streiff

Woodward-Clyde Consultants 3467 Kurtz Street San Diego, California 92110

USGS CONTRACT NO. 14-08-0001-19118 Supported by the EARTHQUAKE HAZARDS REDUCTION PROGRAM

OPEN-FILE NO. 81-878

U.S. Geological Survey OPEN FILE REPORT

This report was prepared under contract to the U.S. Geological Survey and has not been reviewed for conformity with USGS editorial standards and stratigraphic nomenclature. Opinions and conclusions expressed herein do not necessarily represent those of the USGS. Any use of trade names is for descriptive purposes only and does not imply endorsement by the USGS. CONTENTS

Page ABSTRACT 1

INTRODUCTION 3

SCOPE OF STUDY 3 Field Investigation 3

BACKGROUND 7 Regional Tectonic Setting 10 Local Tectonic Setting 12

GEOLOGICAL CONDITIONS IN THE SAN DIEGO TRENCH 18 Faulting 18 Stratigraphy 20

GEOLOGICAL CONDITIONS IN THE CORONADO TRENCH 28 Faulting 28 Stratigraphy 29

DISCUSSION AND CONCLUSIONS 31 San Diego Trench 31 Coronado Trench 34

ACKNOWLEDGMENTS 35 CONTENTS (Cont'd)

APPENDIX A - KEY TO LOGS AND LOGS OF TRENCH A-l IN SAN DIEGO, CALIFORNIA

APPENDIX B - KEY TO LOGS AND LOGS OF TRENCH B-l IN CORONADO, CALIFORNIA

APPENDIX C - FAUNAL ANALYSIS C-l

APPENDIX D - REPORTS ON AMINO ACID AGE D-l ESTIMATES OF QUATERNARY MOLLUSKS

APPENDIX E - BIBLIOGRAPHY E-l LIST OF ILLUSTRATIONS

Page FIGURE 1 - LOCAL FAULT MAP 4

FIGURE 2 - TRENCH LOCATION DOWNTOWN SAN DIEGO 5

FIGURE 3 - TRENCH LOCATION CITY OF CORONADO 9

FIGURE 4 - GENERALIZED REGIONAL FAULT MAP 11

FIGURE 5 - COMPARISON OF RATES 33 ABSTRACT Two trenches were excavated, logged, and interpreted across mapped projections or locations of the Rose Canyon fault zone in the Cities of San Diego and Coronado, Califor nia. The trench in the City of San Diego extended for approx imately 1,645 m across mapped projections of the Coronado fault, Old Town fault, and Rose Canyon fault. The inspection and analysis of the trench exposures indicated one area of normal faulting in the vicinity of Broadway between Front Street and First Avenue in the downtown area of San Diego. The fault strikes generally north-south and has apparent vertical stratigraphic separations of 3 to 4 m in sediments dated by amino acid racemization rates as approximately 360,000 to 560,000, ±75,000 years old. A paleosol estimated to be at least 75,000 to 128,000 years old is displaced 60 cm; a younger paleosol, estimated to be at least 20,000 years old, did not show evidence of displacement. It is concluded that this fault is an antithetic or sub- siduary feature consistent with an extensional stress environ ment in the San Diego area. No other evidence of faulting was found in the trench exposures, thus leading us to conclude that major north-south faulting does not extend through Middle to Late Pleistocene deposits exposed along the trench in the downtown San Diego area. The trench in the City of Coronado was extended across a break in slope previously identified as the fault scarp of the Coronado fault branch of the Rose Canyon fault zone. Detailed logging and analysis of the trench exposures indicated the feature to be an erosional bluff. INTRODUCTION This Final Technical Report for U.S. Geological Survey Contract No. 14-08-0001-19118 documents and describes the results of logging two trenches in areas suspected of being part of the Rose Canyon fault zone. The trenches were located in Coronado and San Diego, California (Fig. 1). The purpose of this study was to obtain geological data to aid in evaluating the location and degree of fault activity of the Rose Canyon fault zone. The study involved logging and evaluating the exposures excavated in Pleistocene deposits across mapped traces of the Rose Canyon fault zone.

SCOPE OF STUDY The scope of the investigation for this study included: (1) Inspection, interpretation, and logging of the expo sures in two test trenches excavated across projec tions of previously mapped faults. (2) Dating soil samples by radiocarbon and racemization techniques as well as relative age estimates by physical properties, degree of soil formation, and faunal assemblages. (3) Evaluation of the data in the context of other information regarding faulting in San Diego.

Field Investigation Trench in San Diego A 1,645-m (5,400-foot) long, 1.9- to 6.7-m (6- to 22-foot) deep trench was excavated through downtown San Diego (Fig. 2). 117-23 I IT-13

32-53'

Mission Florida Canyon dTo-« Fault

Modified after Kennedy and Leqg (1980)

FIGURE 1. LOCAL FAULT MAP Index map showing mapped fault locations in the general area of study, and general locations of trench investigation. OLD TOWN FAULT Bulletin 200 (Kennedy, 1975) BALBOA /It PARK / A.. /

'ROSE CANYON FAULTJ Bulletin 200

(KennedyMH * 1975)

Approximate Trench i

STREET GRAPHIC SCALE FEET

200 400 FIGURE 2 TRENCH LOCATION 1600, . CORONADO FAULTX V Kennedy 1977) DOWNTOWN SAN DIEGO The excavation was generally perpendicular to previous mapped fault locations. Geologic conditions in the trench were logged and evaluated, and geological samples were collected for dating. Various absolute dating techniques were used, including radiocarbon, amino acid racemization, and uranium/ thorium. Relative ages of units were estimated by regional correlation based on physical properties, faunal assemblages, and criteria developed by Quaternary soils specialists. This investigation was made with the cooperation of the City of San Diego and a private contractor. The private con tractor excavated the trench for installation of a new sewer line, and took field measurements (in feet) for the trenching operation. Our logs and station locations (Appendix A) are based on those field measurements. The logging of the trench began 15 m (50 feet) east of the middle of the intersection of Kettner Boulevard and "E" Street. Sections of trench about 15-m (50-foot) long were open for variable time spans. Some sections remained open for several days, but other sections were open for only a couple of hours before backfilling opera tions began. Although the trench was started on February 12, 1980, rainstorms delayed operations until about March 14, 1980. A union strike halted all trenching operations from June 25 to July 28, 1980. Construction delays, such as cave-ins and broken water mains, caused many other short time delays. The final field work was completed October 10, 1980. Trench in Coronado The geological conditions of a 3-m (10-foot) deep, 61-m (200-foot) long test excavation across a scarp in the City of Coronado (Fig. 3) were logged and evaluated. The logs of the trench are presented as Appendix B. The scarp has been iden tified as the Coronado fault branch of the Rose Canyon fault zone (Kennedy and Welday, 1977; Kennedy and Welday, 1980). The excavation was made between November 17 and December 12, 1980, generally perpendicular to and across the mapped fault location. Geological samples were collected for dating by amino acid racemization. Relative ages of units were esti mated by regional correlations based on physical properties, faunal assemblages, and criteria developed by Quaternary soils specialists. This investigation was made with the cooperation of the City of Coronado. The study was done to coincide with and slightly precede a street repair contract issued to a private contractor by the City of Coronado.

BACKGROUND The Rose Canyon fault zone has been shown to extend for approximately 15 km south on land from the La Jolla Cove Shores area (Kern, 1973a; Ziony, 1973; Kennedy, 1975) (Fig. 1). Fault branches have been shown on maps to extend into and across downtown San Diego and the City of Coronado (Wiegand, 1970; Kennedy, 1975; Leighton and Associates, 1978). In the San Diego area, investigators have suggested evi dence of tectonic displacement of the Rose Canyon fault zone in Late Pleistocene and younger sediments (Kennedy, 1975; Moore and Kennedy, 1975; Kennedy and others, 1975; Kennedy and Welday, 1977; Kennedy and others, 1978). The evidence in cludes scattered micro-earthquake activity in the general San Diego area, and suggested displacement of apparent Holocene age sediments on the sea floor (Moore, 1972; Moore and Kennedy, 1975; Kennedy and Welday, 1977; Kennedy and others, 1978). Kennedy (1975) states, "The possibility of Holocene fault activity in the area is not ruled out, though no direct field evidence supports this fact." Kennedy and Peterson (1975) conclude, "Holocene seismic activity along several faults that lie within 10 km of the area is supported by the historic seismicity believed to be associated with the Rose Canyon fault zone in the San Diego Bay area. . ." No direct evidence has been reported for tectonic dis placement of material younger than Pleistocene on the Rose Canyon fault. The youngest displacements of the Rose Canyon fault and onshore fault branches crossing Coronado have not been dated. ^

GRAPHIC METERS c /^. ^v ^ 0 50 ^' V / ^^^^ /^ "--> 7*v^^ .~v.' ^ "^ ~ v---: /x. - i i' ' A'-T-H --.: ^ ^x£ -<^>^ / 1 //-- - ^ION ^C^^: / 200 o^y 106 ^ , / /"~ r' .. ,-f ,-. ixcinicuy <^iid VVelday ^^^r-^ , ' ' ^ " m ' ~'" ^/.f^- . ~

"' y-j?- '.' /^ ~-...r^j; >^ -- - ^ :/ "i'X/:; "' .^1' A ~X^' ~

- ** - O. TRENCH LO< r i,/T,7 C' Station ~-^»-'-

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_.' 1 ,» <~. \ FIGURE 3 TRENCH LOCATION ^ /;? CITY OF CORONADO - ^

> 9 Regional Tectonic Setting San Diego lies within a region traversed by many faults (Fig. 4). Regional fault patterns and plate tectonic theory indicate that the faults are related to the boundary and margin of two crustal plates: the North American Plate and the Pacific Plate. The present boundary of these two plates closest to San Diego is a system of faults in the Imperial Valley commonly referred to as the San Andreas fault system. Faults related to the system include the Elsinore fault, the San Jacinto fault, the Imperial fault, and the San Andreas fault. The northwest-striking, right-lateral regional fault system in southern California and northern Baja California includes the San Clemente fault zone, the San Diego Trough fault zone, and the Coronado Banks fault zone to the west offshore; and the Agua Blanca fault, the San Miguel fault zone, the Vallecitos fault, and the Calabasas fault to the south in Baja California. Historic earthquake records show that the portion of this region presently exhibiting the greatest earthquake activity in Southern California is along the Imperial and San Jacinto faults (Fig. 4). In comparison, the San Diego area, approximately 100 km west of the San Jacinto fault, has a relatively minor historic record of earthquake activity.

10 FIGURE 4. GENERALIZED REGIONAL FAULT MAP

Fault map of the Southern California area showing epicenters of earthquakes of mag nitude 6 and greater. Solid circle show epicenters with year of earthquake, along with magnitude maximum intersity. Open circles with question marks indicate poorly known epicenters. Epicenters are compiled from Hileman and others (1973), and Thatcher and others (1975); faults are compiled from Gastil and others (1975), Jennings (1977), and Legg and Kennedy (1979).

11 Local Tectonic Setting The San Diego area is within the coastal subprovince of the Peninsular Range Province, The area is characterized primarily by Cretaceous, Tertiary and early Quaternary sedi mentary formations, capped by late Quaternary marine and nonmarine deposits. Generally, the Tertiary and Quaternary sedi mentary formations are nearly flat-lying, except for locally deformed areas such as Mount Soledad. A relatively recent erosion surface has been incised onto the Tertiary and Quaternary sedimentary formations. The topo graphic features and geologic setting have also been partially modified by Quaternary faulting. The geologic structure of the San Diego area includes en echelon, north-northwest-striking faults that characteristi cally dip steeply and have apparent normal displacement. These faults lie subparallel to the regional tectonic grain and are believed to result from an extensional tectonic envir onment. The component of extensional stress in southwestern San Diego County is aligned generally east-west; the resulting strain is expressed by normal faults that strike generally north-south. The roughly defined San Diego Bay graben, a structurally depressed block, is bounded on the east by the La Nacion fault zone, on the west by the San Diego Bay faults and offshore faults, and on the north by the Rose Canyon fault (Fig. 1). These faults are discussed in more detail in the following sections. 12 La Nacion Fault Zone The La Nacion fault zone extends north from near the U.S.-Mexico border to at least the south side of Mission Valley (Artim and Pinckney, 1973a, 1973b). This fault zone is composed of a number of closely to widely spaced, parallel to subparallel faults (including the Sweetwater fault and the Chula Vista fault) that displace Tertiary and Quaternary depo sits. The main branch of the fault system displaces the Early Pleistocene Lindavista Formation with stratigraphic separation as much as 70 m. Several traces (as long as 1.2 km), exposed between San Diego Bay and the main branch of the fault system, displace Pleistocene deposits with stratigraphic separation of as much as 30 m. Ziony (1973) reported: The youngest stratigraphic unit definitely displaced by the fault is the Lindavista Formation, which is offset vertically as much as 200 feet at several places. Off sets of basal Holocene deposits along the fault are cited (Artim and Pinckney, 1973) but have not been confirmed by field investigations. As observed at the surface, allu vium of stream valleys extends unbroken across the fault trace. More importantly, topographic features commonly associated with Holocene faulting elsewhere in coastal California, such as sag depressions or well-defined scarps, have not been observed along the La Nacion fault. The existence and recency of movement of other faults are inferred from topographic lineaments or subdued scarps of probable Late Pleistocene age, which appear to disrupt the terrace underlain by the Lindavista Formation.

Kennedy and others (1975) report that the faults of the La Nacion fault system cut the lower Pleistocene Lindavista Formation and are overlain by apparently unfaulted Holocene soil. Kennedy and others (1975) also modified their estimate of

13 the age of faulting by stating, "The maximum age for this dis placement is Early Pleistocene, although terrace deposits that may be younger than the Lindavista Formation are faulted." The exact ages of the Late Pleistocene sediments that are apparently offset were not established. In his explanations of trench interpretations, Kennedy and others (1975) list differences of topsoil-bedrock contacts and topsoil thicknesses over faults at several locations. The remainder of Kennedy's 1975 report indicates that anomalous topsoil-bedrock contacts are common along the La Nacion fault, and that such irregular contacts are numerous and exhibit a relatively consistent pattern of apparent displacement.

Rose Canyon Fault Zone The Rose Canyon fault zone comprises a number of closely spaced, subparallel faults that displace Cretaceous and Ter tiary strata near Mount Soledad. The fault zone, as mapped, continues offshore to the north, and it has been suggested that the fault continues to the south under San Diego Bay and offshore of Coronado. South of Mission Bay, the limits of the Rose Canyon fault zone are diffuse and unclear. Studies of the Rose Canyon fault zone (Kennedy, 1975) have included the Morena fault and the Old Town fault, which are the most east erly faults associated with the zone. More recently, the major zone of faulting has been projected across Coronado to connect with offshore fault features (Kennedy and Welday, 1980).

14 The main fault and some fault branches displace the Early Pleistocene Lindavista Formation. Approximately 140 m of vertical separation of the base of the Lindavista Formation has been recognized near Mount Soledad. The Late Pleistocene Bay Point Formation lies across some fault branches, and may be faulted. Kennedy (1975) shows two concealed faults, one extending to within about 0.5 km northwest of downtown San Diego, and one to within about 0.8 km. More recently, Kennedy (1979, oral communication) projected the Rose Canyon fault 1.2 to 1.8 km west of downtown San Diego to connect with offshore faults identified near Coronado Island. The Old Town fault is now not considered by Kennedy (1979, personal communication) to be a part of the Rose Canyon fault zone.

San Diego Bay Faults and Offshore Faults A set of inferred faults, including the Coronado Fault and the Spanish Bight fault, may displace Quaternary sediments in San Diego Bay and just offshore of San Diego (Kennedy and Welday, 1977; Kennedy and Welday, 1980). These faults have recently been described as the southern extension of the Rose Canyon fault zone (Kennedy and Welday, 1980). The faulting is largely based on interpretations of subbottom acoustical pro filing investigations (Moore and Kennedy, 1975; Kennedy and Welday, 1977; Kennedy and Welday, 1980). The trends of these

15 faults vary from slightly northwest to slightly northeast. Kennedy and Welday (1980) suggest that the faults displace an estimated 7 m of near-surface sediments, and that the most recent slip was in the Late Pleistocene or early Holocene. Their work suggests a set of short north-striking normal faults with the west side faulted relatively upward.

Other Local Faults As more geologic studies are completed in the San Diego area, many relatively small faults are being identified. Two of these features include the north-striking Texas Street fault and Florida Canyon fault (Fig. 1). These normal faults displace Early Pleistocene deposits and conform to the extensional stress environment characteristic of the San Diego area.

Ages of Local Faults Geologically young materials in San Diego have been dis placed by faults. Faulted sediments in the southeast Mission Bay area, approximately 11 to 13 km northwest of the trench sites, have been radiocarbon dated at 28,000 ±1,500 years old (Liem, 1977). Unpublished information from Mr. William Elliott* (1980, personal communication) indicates that a fault

Consulting geologist, San Diego, California

16 in Chula Vista has displaced sediments radiocarbon dated as approximately 25,000 years old. Sediments in the downtown San Diego area, dated by amino acid methods as approximately 200,000 to 300,000 years old, may have up to 3 m of displace ment (unpublished Woodward-Clyde Consultants data). A deposit on Point Loma dated as approximately 120,000 years old has up to about 4.6 m of displacement (Kern, 1973a). Sediments mapped as the Bay Point Formation (approxi mately 100,000 to 130,000 years old) are faulted in La Jolla, Point Loma, Chula Vista, and National City (Peterson, 1970a, 1970b; Kern, 1973a, I973b; Moore and Kennedy, 1975; Kennedy, 1975; Kennedy and Welday, 1977). Most of these fault expo sures may be in Middle Pleistocene deposits. Studies of the offshore areas north of La Jolla, south of Coronado, and in San Diego Bay, have identified faults by subbottom geophysical profiling (Moore and Kennedy, 1975; Kennedy and Welday, 1977; Kennedy and others, 1978). These faults were interpreted as displacing Holocene (up to 11,000 years old) ocean bottom sediments; however, the inferred faulted material has not been dated. Therefore, there is some uncertainty regarding the age of faulting. To date, no direct evidence for Holocene faulting has been established in the San Diego area. Topographic features such as sag ponds, offset stream courses, or sharply defined scarps, commonly associated with Holocene faulting elsewhere in

17 California, are not generally associated with local faulting; this suggests that these faults, if they are active, have a very low rate of activity.

GEOLOGICAL CONDITIONS IN THE SAN DIEGO TRENCH Faulting The stratigraphic sequence in the east-west excavation has been disrupted by faulting at one general location. The faulting strikes generally north-south in the vicinity of Broadway between Front Street and First Avenue (Station 1710 to 1870). The primary shear appears to be located at approx imately Station 1795. The main shears, are approximately 0.6 to 1.3 cm wide; short, discontinuous shears were observed within a few centi meters of the main shears. Several paper-thin, clay-lined fractures are present subparallel to the main shears. Dis placements along these fractures are usually less than a few centimeters. The sheared material is composed primarily of brecciated and discolored sand containing silt and clay binder. Some weathered zones extend down into the shears. In some areas, the sheared materials have been altered to clay. A vertical fracture, backfilled with red oxidized sand, grades upward into an overlying paleosol. Neither clay gouge nor slicken- sided surfaces were observed along any of the shears.

18 The uppermost formational sand beds exposed in the trench have apparent vertical displacements of 2 to 3 m. Based on test boring correlations by Woodward-Clyde Consultants in the nearby area, a stratigraphic separation of 3 to 4 m is likely in a series of clay beds at depths between 16 and 20 m. The results of eight amino acid age dates indicate the sands represent a continuous depositional environment and are approximately 360,000 to 560,000 years old. A paleosol esti mated to be at least 75,000 to 128,000 years old is displaced 60 cm. No shears or fractures extend up into a younger overlying paleosol (estimated to be at least 20,000 years old), and no irregularities that were construed to be fault displacements were noted at the base of a recent topsoil contact or this paleosol. The fault appears to be normal, with the east side down. No evidence in the exposures indicates significant strike-slip (horizontal) separation. The fault appears to be the result of an extensional stress environment present in western San Diego. The fault area does not correspond to gravity survey anomalies (interpreted to be faults) in downtown San Diego (Harrington, 1980). No other faults were found in the trench.

19 Stratigraphy Eleven significant stratigraphic units were exposed in the trench. These units are described below in order of increasing age. Each unit name is followed by a symbol or symbols used to identify that unit on the trench logs. Where possible, absolute ages of the materials are given. Absolute dating of geologic materials can be difficult because of a lack of datable geologic materials or because the age of the available materials is not within the age range of dating techniques. Where materials for dating techniques were lack ing, other methods, such as degree of weathering, soil forma tion, and paleontologic or stratigraphic correlations, were used to estimate the ages of materials.

Holocene Aeolian and Alluvial Deposits (a) These deposits consist primarily of brown to grayish- brown, clayey, silty fine- to medium-grained sand. A discon tinuous, poorly formed stone line exists at places along the base of the unit. The deposits range in thickness from less than 20 cm to approximately 1 m. The deposits are friable, massive to poorly bedded, porous, and contain numerous worm and small animal burrows as well as decayed roots. A thin (0.1 to 0.5 cm thick) organic mat (entisol) is preserved in some areas. In most places, the upper surface shows dis turbance by grading, and in some areas these deposits have been

20 removed. A poorly developed soil profile grades from a thin "A" horizon to a "C" horizon with no development of a clay "B" horizon layer. The aeolian and alluvial deposits post-date paleosols and formational units upon which they have been deposited. Avail able results of radiocarbon dating performed on similar allu vial soils from the San Diego area indicate approximate ages of 2,000 to 3,000 years (Charles J. Pinckney,* 1980, personal communication). Based on the lack of a well-defined soil profile on these deposits, we estimate the deposits to be less than 5,000 years old; however, some areas may be only as old as a few hundred years. Geologic evidence in the trench exposures indicates no fault displacements in this unit.

Holocene Embayment Deposits (Q, ) This unit was exposed in the western end of the trench below Elevation 8 feet [Mean Sea Level Datum]. The unit con sists of grayish-brown to dark gray, silty clay. The deposits have a decaying organic odor and contain local lenses of silty sand. The deposits are covered by approximately 2 m of fill.

Senior Consulting Geologist, Woodward-Clyde Consultants, San Diego, California

21 Buried Paleosol (S-.) This unit consists primarily of dark brown to dark yellowish-brown, sandy clay. The soils are firm to hard, and contain numerous small roots and some animal burrows. The soils have a poorly to moderately well-developed, medium angular to blocky structure, and thin to moderately thick clay skins. Manganese oxide staining is common and often concen trated in the lower part of the unit. This unit has developed on formational materials and older paleosols, and was exposed along most of the length of the trench. The unit is roughly parallel to what can be interpreted as the original topographic surface prior to development of the downtown area. Based on a comparison of the degree of soil profile development in other areas of San Diego, we estimated this paleosol to be at least 10,000 years old; however, some parts of the paleosol may be much older, perhaps as old as oxygen isotope Stage 5* (Shackleton and Opdyke, 1973).

Pleistocene Channel Fill and Estuary Deposits ( Q3a, 23b, 23c, Q3d) This sand and gravel unit includes nonmarine, brown to dark brown, gravelly fine- to coarse-grained sand, and dark

Oxygen isotope Stage 5 lasted from approximately 75,000 to 128,000 years ago.

22 brown to grayish-brown, sandy to silty clay. The sand and gravel sequences may be alluvial deposits, whereas the clay deposits appear to be estuarine deposits locally containing up to 15 percent organic matter. The sand beds are typically lightly oxidized with local weak cementation. The unit has numerous channel fills, and cross bedding is common in the sands. The base of the deposit is marked by two distinct gravel sequences. A radiocarbon date performed on a bulk sample at Station 975 gave an age of 19,300 ±2,100 years.

Buried Alluvial Deposits (Sla;n , These deposits consist of dark brown to dark yellowish- brown, clayey, silty fine- to medium-grained sand. The depos its are firm, porous, and massive to poorly bedded; they have numerous animal burrows in-filled with material from the over lying horizons. Concentrations of hematite and poorly formed manganese nodules are common and result in reddish-brown staining. These deposits pre-date the paleosol (S.,) that has, in part, formed on them.

Older Buried Paleosol (S9 ) This paleosol consists of hard, dark brown to dark grayish-brown, sandy clay. The paleosol has a well-developed,

23 coarse, blocky to prismatic structure, and moderately thick to thick clay skins. The lower part of this paleosol grades into hard, brown, sandy clay having a moderately well-developed, angular to blocky structure, and thick clay skins. The minimum time required to form a paleosol with the above characteristics is at least oxygen isotope Stage 5 (post-Sangamon interglacial), (Bert Swan,* 1980, personal communication). Based on the degree of soil profile develop ment compared to soil profile development in other areas of California, this paleosol is estimated to be at least 100,000 years old, (Kathryn Hanson,* 1980, personal communication). The paleosol is conceiveably much older than oxygen isotope Stage 5; it may be a few hundred thousand years old.

Pleistocene Alluvial Deposits (Q2 ) This unit consists of nonmarine, light reddish-brown to reddish-brown, gravelly, clayey fine- to coarse-grained sand. The deposits are typically lightly oxidized with weak cemen tation. The clasts are pebble size and bedding is essentially horizontal. This unit pre-dates the paleosol (S2 ) developed on the deposits, and post-dates the marine deposits (Qt) upon which it has been unconformably deposited.

Quaternary Soils Specialists, Woodward-Clyde Consultants, San Francisco, California.

24 Buried Paleosol (S~) The upper 30 to 45 cm of this paleosol consists of grayish-brown to dark grayish-brown, hard sandy clay having well-developed, coarse, blocky to prismatic structure, and thick, continuous clay skins. The paleosol grades down into hard, dark brown, sandy clay having moderately well-developed, medium angular to blocky structure, and numerous manganese oxide stains and nodules. This unit is faulted at Station 1795 and has a minimum of 60 cm of stratigraphic separation. The minimum time required to form this paleosol is at least post-oxygen isotope Stage 5 (post-Sangamon interglacial), (Bert Swan, 1980, personal communication). This pal eosol is probably much older than oxygen isotope Stage 5; it may be a few hundred thousand years old.

Middle to Late Pleistocene Marine Deposits (Qt ,Qt, Qt,) This formation consists of fine to moderately bedded, light gray to light reddish-brown, silty fine- to coarse grained sands containing thin, scattered pebble layers. The beds are friable and tend to be lenticular. Bedding thickness varies from a few millimeters to several centimeters. Some small shell fragments and local fossil lenses and layers are present. Faunal analyses of the fossils are included as Appendix C.

25 This formation underlies most of the downtown San Diego area along the trench alignment. The uppermost sand beds exposed in the trench, have been faulted with stratigraphic separation of 2 to 3 m at Station 1795. This unit has been mapped as the Bay Point Formation. The Bay Point Formation (Sangamon) in San Diego is dated at approximately 120,000 ±10,000 years old (Kern, 1973). K.R. Lajoie (1980, oral communication) of the U.S. Geological Survey is of the opinion that many of the deposits in the downtown San Diego area, mapped as Bay Point Formation, may be significantly older than oxygen isotope Stage 5, and that they could be a couple to several hundred thousand years old. The results of several amino acid age dates performed on shells from this unit give ages ranging from approximately 200,000 to 560,000, ±75,000 years old. A summary report of the amino acid dating is included in this report as Appendix D.

Pleistocene Terrace Deposits (Qtt) These deposits range from light to dark reddish-brown, sandy to clayey cobble conglomerate; to clean, pebbly medium- to coarse-grained sand. The beds are iron-stained and are cemented locally by iron oxide. Some of the sand beds are mottled light red in a generally reddish-brown sequence. The conglomerate beds are typically 0.3 to 1 m thick. Clasts are

26 generally well-rounded and range from about 1 cm to cobbles more than 15 cm in diameter. The base of this unit is an irregular, scoured contact into beds of the San Diego Forma tion. These deposits typically are present above an approximate elevation of 65 feet, and are, in part, gradational with the Middle to Late Pleistocene marine deposits.

Pliocene San Diego Formation (Tsd) This unit consists of finely to massively bedded, light gray to light brown, silty fine- to coarse-grained sand. These sands contain thin layers and lenses of pebbles and at least two thin layers (less than 6 cm thick) of light gray, sandy clay. Most of the light gray sand beds are friable and subject to caving in vertical excavations. Bedding thickness varies from a few millimeters to a few meters. The stratigraphic section exposed in the trench is litho- logically similar to the type section of San Diego Formation. This section is known to contain rare but locally abundant fossils. The section is micaceous with biotite that weathers to reddish-yellow to yellowish-red halos. The San Diego Formation generally has been considered Pliocene, but its exact position in the Pliocene has been variously placed by different authors. Hertlein and Grant (1944) assigned the San Diego Formation to the Middle Pliocene. Woodring and Bramlett (1950), by way of chart correlations, suggested a range from late Early Pliocene to Late Pliocene. 27 Hertlein and Grant (1954) suggested an age of Middle Pliocene to early Late Pliocene. Milow and Ennis (1961) considered the San Diego Formation upper Pliocene. Allison (1964) suggested an age of Early Pleistocene based on the presence of a fossil horse tooth. Ingle (1967) concluded that the formation was deposited no earlier than Early Pliocene and no later than Late Pliocene. Mandel (1974) suggested an age of very late Pliocene to earliest Pleistocene. Recently, several fossil horse teeth collected from the lower San Diego Formation were identified by Dr. Savage (1979, personal communication) of the University of California, Berkeley, as Equus and younger than 3.5 million years old. Based on the available published and unpublished data and definitions, the San Diego Formation appears to be a Middle to Late Pliocene unit that extends into the Early Pleistocene, with an approximate age range of 1.5 to 4 million years old.

GEOLOGICAL CONDITIONS IN THE CORONADO TRENCH Faulting No faults or fractures were observed in this trench. The pivot point at the base of a fault scarp remains at relatively the same position (Philip Birkhan,* 1981, personal communica tion). A fault, if present, should have been encountered at approximately Stations 110 to 120.

* Geologist, Woodward-Clyde Consultants, Orange, California

28 Stratigraphy Four significant stratigraphic units are exposed in the trench. These units are described below in order of increas ing age. The unit name is followed by a symbol used to iden tify that unit on the trench logs. Where materials for abso lute dating were lacking, other methods, such as degree of weathering (soil formation), and stratigraphic or paleontologic correlations, were used to estimate the ages of materials.

Holocene Aeolian Deposits (a., ) This unit consists of very porous, friable, pale brown, silty, very fine-grained sand, deposited unconformably on an erosional scarp. The deposit appears to overlie and to be younger than an alluvial deposit (a2 ). The age of the aeolian unit may vary from a few hundred to a few thousand years old.

Holocene Alluvial Deposits (a? ) This unit consists of fine sand that is porous, friable, light reddish-brown and silty. A poorly formed soil profile has begun to develop in the upper 5 cm and consists of gray ish-brown, slightly clayey, silty sand exhibiting local manga nese oxide staining. The profile grades from an "A" horizon to a "C" horizon with no distinct "B" horizon present.

29 Based on the degree of weathering and soil profile devel opment, this unit is estimated to be less than 5,000 to 10,000 years old.

Paleosol (S) This paleosol consists of dark reddish-brown, clayey sand. The soil is hard, and has a poorly to moderately well- developed, medium angular to crumbly structure, and thin clay skins. Manganese oxide staining is concentrated along the base of this paleosol. Based on the degree of weathering, this paleosol is esti mated to be at least 10,000 years old.

Middle to Late Pleistocene Marine Deposits (Qt) This unit consists of sand that is thin to moderately bedded, light gray to light reddish-brown, silty fine- to coarse-grained and contains thin, scattered pebble layers. The beds are friable and tend to be lenticular. The light reddish-brown color appears to be secondary and restricted to within 3 m of the ground surface. Bedding thickness varies from a few millimeters to several centimeters. Some small shell fragments are present in the trench, and a test boring placed at the west end of the trench recovered fossil shells from Elevation +5 to Elevation -8 feet (Mean Sea Level). A faunal assemblage in similar deposits was recovered from an

30 excavation at 10th Street and "B" Avenue in the City of Coronado. Fossil shells were also recovered from lithologi- cally similar deposits at Ynez Place and Pomona Avenue. A reference location map is included as page D-l in Appendix D. The results of several amino acid age dates performed on shells from this unit give ages of approximately 220,000 ±30,000 years. These results are comparable to unpublished amino acid dates obtained in the general area of the City of Coronado (Wehmiller, 1981, oral communication). A summary report of the amino acid dating is included in this report as Appendix D.

DISCUSSION AND CONCLUSIONS San Diego Trench A faulted area has been identified in the downtown area in the vicinity of Broadway, generally between Front Street and First Avenue. Formational sediments, amino acid age-dated at approxi mately 360,000 to 560,000 years old, have been displaced 3 to 4 m by the fault. The uppermost sand beds have a stratigraphic separation of 2 to 3 m. A paleosol estimated to be at least 75,000 to 128,000 years old is displaced a minimum of 60 cm. A younger paleosol estimated to be at least 20,000 years old did not show evidence of stratigraphic separation. In our opinion, the fault has not been displaced in the last 20,000 years and probably not in the last 75,000 years.

31 A fault that has a displacement of 3 to 4 m in 360,000 to 560,000 years has an average displacement rate of 0.007 to 0.011 mm per year. The average displacement rate calculates to 0.005 to 0.008 mm per year for 60 cm of displacement in the last 75,000 to 128,000 years. As a relative index of fault activity, this rate is compared to estimated rates of other San Diego faults (Fig. 5). Assuming that the average displacement on this fault has been 30 cm per event, an average recurrence interval between events of surface faulting would be approximately 27,000 to 56,000 years over the past 360,000 to 560,000 years. The average recurrence interval between events of surface faulting has been approximately 54,000 to 112,000 years, if an average displacement of 60 cm is assumed. Based on its lack of surface expression, relatively little displacement in geologic time, sense of displacement, and lack of direct tie-in to more pronounced fault features in the San Diego area, we consider this fault to be an antithetic or subsidiary feature. Such features are not unusual in an extensional stress environment as is present in the San Diego area. Similar faults with very short horizontal extent and limited vertical displacement may also be located elsewhere in downtown San Diego. We found no other evidence of faulting in the trench exposures, thus leading us to conclude that major north-south

32 DISPLACEMENT m x I? 2 O ID o m c Q. JiJ 3 2 CD 30 CL rn o s O

5 =ft O g ^ H § 2 < H 3) S 0)i-t- 0) m CD I m

2 \< m

m r~x

iiCD n> faulting does not extend through Middle to Late Pleistocene deposits exposed along the trench in the downtown San Diego area.

Coronado Trench We found no evidence to support suggestions that the scarp through the City of Coronado is a fault, or is a fault- related feature. However, we found evidence to suggest that the scarp is an erosional feature not unlike numerous other bluffs in the San Diego shoreline area.

34 ACKNOWLEDGMENTS This work was supported by the U.S. Geological Survey's National Earthquake Hazards Reduction Program (Contract No. 14-08-0001-19118). Mrs. Dorian Mills and Mr. David Nelson of Woodward-Clyde Consultants, San Diego, assisted with the geological field investigation. Ms. Kathryn L. Hanson and Dr. Frank Swan of Woodward-Clyde Consultants, San Francisco, provided information and interpretations regarding Quaternary soils. Dr. Lloyd Cluff of Woodward-Clyde Consultants, San Fran cisco, provided input into interpretations of fault activity, recurrence intervals, and tectonic setting. We wish to thank Ms. Margaret Kelly, Ms. Cynthia Hayman, and Ms. Jerri Samuels for their patience and assistance in the preparation of this report. We also wish to acknowledge the input and contributions in age dating by Dr. John Wehmiller of the University of Dela ware, working under a separate U.S. Geological Survey grant.

35 APPENDIX A

KEY TO LOGS AND LOGS OF TRENCH IN SAN DIEGO, CALIFORNIA KEY TO LOGS

HOLOCENE AEOLIAN AND ALLUVIAL DEPOSITS

Brown to very dark brown to grayish-brown, clayey silty fine to medium-grained sand. The deposits are friable, massive to poorly bedded, and porous.

HOLOCENE EMBAYMENT DEPOSITS

Grayish-brown to dark gray, fine, sandy silty clay. The deposits have an organic odor and contain local lenses of silty sand.

BURIED PALEOSOL

Dark brown to dark yellowish-brown sandy clay. The soils are firm to hard and have a poorly to moderately well-developed, medium angular to blocky structure and thin to moderately thick clay skins.

PLEISTOCENE CHANNEL FILL AND ESTUARY DEPOSITS

Light brown to light reddish-brown to dark brown, gravelly silty fine to coarse-grained sand and dark brown to grayish-brown sandy to silty clay.

Mainly estuary deposits consisting of dark aray to crrayish-brown silty clay

with interbeds and channel fills con sisting of dark gray to grayish-brown fine to medium-grained sand.

FIGURE NO. A-l KEY TO LOGS (Con't)

Mainly alluvial deposits consisting of light brown to brown, silty to clayey fine to coarse-grained sand containing pebble and gravel layers.

and grayish-brown, silty to clayey fine grained sand and fine-grained sandy silt and clay containing thin interbeds of coarse-grained sand.

and browr, clayey to silty, fine to medium-grained cross-bedded sand.

Dark brown to reddish-brown, locally lightly cemented medium to coarse-qrained sandy gravel containing friable coarse sand beds.

Light brown to brown, sandy pebble gravel containing sand interbeds; pebbles are typically stained with iron oxide or manganese oxide.

BURIED ALLUVIAL DEPOSITS

Dark brown to dark yellowish-brown, clayey silty fine to medium-grained sand. The deposits are firm, porous, massive to poorly bedded, and are stained with manganese

OLDER BURIED PALEOSOL

Dark brown to dark grayish-brown sandy clay The soil is hard and has a well-developed, coarse, blocky to prismatic structure, and moderately thick to thick clay skins.

FIGURE NO. .A-2 KEY TO LOGS (Con't)

PLEISTOCENE ALLUVIAL DEPOSITS

Light reddish-brown to reddish-brown, gravelly clayey fine to coarse-grained sand. The deposits are typically lightly oxidized and moderately to lightly cemented.

FAULTED BURIED PALEOSOL

Grayish-brown to dark grayish-brown, hard sandy clay having well-developed coarse, blocky to prismatic structure and thick continuous clay skins.

MIDDLE TO LATE PLEISTOCENE MARINE DEPOSITS

Light gray to light reddish-brown, silty fine to coarse sands containing thin pebble layers and rare but locally abundant fossil shell beds.

Light grayish-brown to brown, clayey fine to coarse sand containing local thin beds of sandy clay and pebbles. Slightly cemented and stained by iron oxide and manganese.

Light gray to light yellowish-brown silty fine to medium-grained sand containing thin coarse sand and pebble beds and local fossil shell layers. Beds are friable and lenticular.

Brown to gray, sandy, pebble to cobble to boulder, conglomerate bed. Matrix is gray silty clay with white calcium carbonate stain on upper qravels, reddish- brown oxide stain on lower gravels.

FIGURE NO. A-3 KEY TO LOGS (Con't)

PLEISTOCENE TERRACE DEPOSIT

Light reddish-brown to dark reddish-brown sandy to clayey cobble conglomerate; containing clean, pebbly medium to coarse-grained sand. Beds are iron stained and locally cemented by iron oxide.

PLIOCENE SAN DIEGO FORMATION

Light gray to light yellowish-brown to light brown silty fine-grained sand containing thin layers and lenses of pebbles and at least two thin clay layers.

FOSSIL SHELL LOCALITIES

COARSE SAND LENSES AND THIN SAND INTERBEDS

<*.: GRAVEL OR PEBBLE INTERBEDS

THIN CLAY LAYERS

LITHOLOGIC OR GEOLOGIC UNIT CONTACT

FAULT

FIGURE NO. A-4 Stations 10 20 30 40 50 H- »- -H

4" utility 3" Utility Line Line Asphalt

10- 6- ' .: '

Shell Fragments -5-1

GRAPHIC SCALE (Meters)

1 I 0 1 2 3

LOG OF TRENCH (NORTH WALL) STATIONS 0 TO 50

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o a a o 3 en n

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Asphalt Over Concrete

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GRAPHIC SCALE (Meters) 1 I , ,. i i 0 1 2 3

LOG OF TRENCH (NORTH WALL) STATIONS 250 TO 300

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20 Asphalt Over Concrete Asphalt

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LOG OF TRENCH (NORTH WALL) STATIONS 350 TO 400

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LOG OI<' TRENCH (NORTH WALL.) STATIONS 1750 TO 1800

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en o ^> O"3 Mg -3

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00 ro s Elevation (Feet)

NJ U) U) Ul o 01 NJ I-"

NJ M O

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O O ro o o

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ro NJ

o _ oa 1z OB

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-.. .OP*! Elevation (Feet) NJ NJ OJ O I/I O LH I K! ro

O 3B

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MM iI W""\ ' ' I I < , 5 fen'

m §

ii Stat ions 2400 2410 2420 2430 2440 24'

Asphalt Ovor Concrete

40H

Jj Cu

GRAPHIC SCALE (Meters) 20-1

LOG OF TRENCH (NORTH WALL) STATIONS 2400 TO 2450

DRAWNBY: rnrR ^CHECKED BY; gA 1 PROJECT NO: 50135H-GK01 | PATE; 1Q-1Q-8Q | FIOUHE MO; A- 1 Elevation (Feet) Elevation (Feet)

O i o a o | 5 3 ^ 7T

MM*

O X m O X m O

1 a b 2 in O m > 0 O -3 ^ Z 0 H p 2 ?3 '.n ^1 Z 01 to O O LH m M o u> r~^ tn 2 |TJ >-3 O 1 O *J cn -3 M to 3: o Ln M (_n SI 0 > MM f^-t 0 m i 0 i O3 1 00 o

Tl 5 m ! > i ./-. i-'i'i:i:-^-.i\':'!;; sv^.'Jv^3^ ; ' V-^:^^U^ :^S^^3^ ' -. ' ' ' Elevation (Feet) U) o

o 0 1 a

3 n

O z m :;' 0 * m O

9 a sr- yjlo em -3'4 > -t 0 t Z ^3 "J Z M 0 O H Z 73 75 ^ LH 2 C ro O h-1 01 ~ OJ U1 on 0 . z T ^ o 0 ?d ^ KJ o ro ~ i 0> o s: 0 > o > h. m

o 1 T 00 o

n 5 Ca m i > i t-i'-r.'--':^"' fV^TVi:-"fyl-aV- t-i-: vi? Elevation (Feet)

c o

o O i a z OB

3 n 01 n

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Ln O

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0 >

L8 Elevation (Feet)

--J C O

o a iz 0 <

O X m O X m O 00 S mmm i r a o 2in -^ > 3 q _3 z 5 p 3 H 'Si ^ LT! z

LO w^ 0 ~ z 1 H 0 O 5C i M zi i --j LH SI mfmm O > O H m i ' T X KJ 1 --J GC .£» C O

Tl 5 c a in ! "i 2 St.it.ion; 2750 27GO 2770 2780 _ _ j. . 2790

AspliaJ t Over Concrete 50

#v$#^\/^-- ' ^ '/^'' ' ^ ^^] ',.. ' ' . '-'. ''+. v' :-".- ' " \''.''(^;'': '' '' ^:^'.;f'V'; .'f:'- '?$&?$}' &;& ' :^/?.\^$^ 4! ;-' :-; '' ;<;:-. ' ' .- "' .' '°;; ' ' ;> f$$!$$?#^^ ^'P^^S1'''^ ;':*: '!*.' '':''*^t;^',^' ^^!:^^^^-:':^^ QI: '. ^ * '4;***'' *** . **;';v >'..*>'"*. **''' ** ; ;.:*« , ; X' ' f SBiSfe\lS^i|S^:^^^ ' '.'". V:- i -*-?: '"-' ^.'-'.' ' .; ' '> ^-''^ %o .«y «» <3P<> «r> ^ ^'<^,**'. *.-^><^

30 H

25J C'.RAPHir (Metors) J

I,Or; UK TRENCH (NORTH WALL) STATIONS 2750 TO 2800

DRAWN BY: [ CHECKED BY; £fl | PROJECT NO: 50J35H-C;EOi [ DATE; 10-8-80 | FIGURE NO Stations 2800 2810 2820 2830 _u_.. fPJast. ic Manhole Concrete Asphalt Over Electri c (Still in Rox Concrete Conduit 50-i \

45-

35-

30- &- -î^^^^^Mii^^M^s^îî&L Qt

25J GRAPHIC SCALE (Meters) TURN POINT ON INTERSECTION J OF BROADWAY AND FOURTH AVENUE LOG OF TRENCH STATION 2800 TO 2850 NORTH WALL TO STATION 2036 - EAST WALL TO STATION 2850 DRAWN BY: Tn ,) ; | CHECKED BY: gfl | PROJECT NO: 501 35H-G1K) 1 | DATE; 10-8-80 | FIOUBE MO; A-&J Elevation (Feet) Ln o O NJ r 00 Ln

O 1 a a (D iz OB O cn 3 n

MMM NJ X O --J z o ffl o rt- ffl 0) 0 OB

a i i § b q 71 O

o M " 0 1-3 , 00 Ln 2! pd 1-00 O en t/d ; O t > 2: Oj ro o Ln oo a ~ Ln 1 O O Tj H3 > tb > O cn NJ

MMH 0 > 0 M O 1 ( ~ ' H ffl ^ijsiiSjiiiijM I < 0 1 00 1 00 o

MM" n o

ffl i i Elevation (Feet) OJ GO Ln O cn O NJ _J r §vD

NJ vD

o i

o en n > r OT NJ O

.'/I '-f

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NJ UD U> O M n vD x o

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UJ U) £» NJ P - U-

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t-J

b in d -3 > O

CO K z O votxj n:O (_n ^^ y^^v

"3 > O OT o s: o r>1

ro -D O ' Elevation (Feet)

M U) U) Ln Ln O tn O t_n O _i_

o -i o 31 Q Pd Z OB O cn n

PI n x m S o 1) * rt m (D O 09

31 o 2 J\ a m l-j O > o

o nn o -^ R H > O cn o £ tno r>1

10 I 03 I 2 OD o O

o Elevation (Feet)

U) OJ >£> Ul o l_n O _l______I J Ln O

o a

< O 3 en X" O >r « PI O Z m 3: O o X n- m o O M en £ o a r o 2 73 C~i m H > 0 3 t-3 Tl z M p O H LJ z to O U~l en p] O 2 u» O UJ o ^: LH Ul * O ^-x r~}T p] *^1_3 «">!< ' PI O en o i-3 h- ' LJ ^J 0 > "" o r1 O M > m r- ' O 1 X 1 o O3 ^o O o

Tl 5 c m i > * 9*- Elevation (Feet) u> O O

U) .1 > o :^W:

en T! M H -3 O Z G pa G >-3 » 3 nn en T3 n o > O rH z o G z

NJ O

o -* so CO cn H > -5 M cn O t-g n Z H> r1 U) M O i O CD i Z ro cn g I u> i-1 H Z O XI O O 3 pa z >-3 H n 3 O =1 li >s: ^u. r1 LH f o -3 O

13 Elevation (Feet) NO U) Ul o

OJ I

o Is 5 o

S NJ n-ro o

cn ^

3D O

o ^

0 I 0 ro L - 00 *- ,o

CO o Stations 3200 3210 1220 3230 3240 I I _ i

45, Utility Lines Asphalt Over Concrete Utility Line

35-

;; .* __,-... Qt

30-

25J

GRAPHIC SrALFl (Motors)

L .- ..J 1 0 1 2 3

LOG OF TRENCH (NORTH WALL) STATIONS 3200 TO 3250

DRAWN BY: Ch | CHECKED BY: &V | PROJECTNO: 50135H-GE01 | DATE: 10-28-80 | FIGURE NO: A-^> ( ) UJ LO O i-n

_ NJ Ln O

I v^-> r- t"-5 i <^ ! o

0 o a o > 50 5 > z "3 OB < i 1 r^M j,,: jo n*n > ^^^ t3 o X m 2 o O x re m o O i-S OB

^ ^

^ i 9 b a -300 O em ^ 2 3 r-1 0 -3 Z Z 50 p '/2 z:m Ln ^ n O NJ ^ h^ Ln UJ O ^^ Ln -3, Oz: T 0 W o >-3 w t^o ^ 0 OJ H^ o s: 0 > P O ^^ > m

M O 1 M CD 1 CD 0

T» O a m ! > i to UJ Ln Uu > o o

-n 0 a o z CB 2 < i-1 "* Mn

c 73 1 > ^ i o n z NJ m S o o * rr m (0 O t^ CB 01 S u> MM s ^ 73 (D a -3 2 > O m iJ n} O M 0 t-3 Z 50 Z 73 R p Z Ln u> O ^ OJ C^ i . o o^ o _^ Ln , 2: ^ ° T O po ^ -g ?^ OJ i . Ln 5- 0 § 1 (

^ M tr1 0 H m t ' o i NJ M-l Hi;...... 03 ?^i« 1 oc . 'I! I. .1 ll^-TV;^^ o m*m ii J '1 ! 0 1 ' i I .!$ IfcOP'vA^

m ! > i Elevation (Feet) O LH O

~n o a 0 | § 00 = M -* n en -^

o s z tsj _ ^ m s O O ^5 (-! m O O r*{ 00 cn I CO

|PROJE f-H b en Q > O O >-3 TJ -4 i i Z o 3 O C/l M Ln z '00 O uj n o OJ U1 <£) c \ ^.^^ T ^ o r~j o ?o 0 w S t ' c > ^ i o ^

m t 1 o i (0 1 00 o

It o c a 9 i Elevation (feet) UJ (jj

O O

^_-' <_. 0 a en

z 2 OB t t ' o 0 rr 05 n > a O z to - . m 2 o O X rt m 0 O M OB on

u> rt 0) S rT H- o « f 3 O Cfl a O5 O 2 H m > O O H ^ M Z O -3 2 50 p C/5 3 ~n 2L.

O u> O U) ^ ^: O UJ 0 un 0 2 T H3 0 r-j 0 5° d O U) ^ p . un § O ^

^ MM O g

m i o i M ^) 1 00 o

n 5 c a m i > i -j Elevation (Feet) OJ U) j^ ^ 9 ^ Q I01 en O

I -4 0 p

1 t |8 ^ m c 33 4^ O o o

Pi i ' / '-'i ' ' ' r ! i I 1 I I ;!.- «. I I OJ

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2 I r- O Jl O) ~r ^.

2 'j~i

Z 3 -3 O Z 33 .7) K y Z "uJ O 01 3 o o _^

o LH 5? O > tr1

01 x^ o Elevation (Feet) to tn V1

UJ Ul

u; Ul

en-3 bn 3 o o in 73

LJ Z 01 O~ on 00 o

UJ tn U) O r- O O

.i' ''..'II '"'!;' l.,l-lf« 3 ,y, 411 '/i'.' ,ii !'.'; "^ § all 01 n \J o mM || ||i '/, 'L "IK % f j I'', IV1-KP2& m |;!' ;!, O rv, ! * j| : ' I : ,!/; ,2 !llil i '" V

S en 01 O u> O Z O en n Z 01 OJ O CT» OC O Q O ^ 0S 3

O <-"

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IBH^ s O X tsj -I m 3: o O JR rt O m fT> o O ^ 3 OB ~-»cn QJ < 'Jo ;! | UJ H- 3 .'iluli: ili\4T :i«'.i!, rt i^M« a e en Q m > O q M O *-3 o "* cn M un 2 00 O UJ O o Oi "^ u» 01 o _ T o | w ^ 0M -j "

JH o H ffl t O 1 NJ

1 00 o '{,[ ' il-t i \ ' Mi« n 5 i m i

i Elevation (Feet)

-4 O O

f'!!l,i!f !i!,. ' ,

-4 i i O

O i Oa $z OB

I 1 M'^ r

-4 o NJ Xm O O X m O

M^ -, a en Q 2 "3 m > O q "3 ^ t i 0 -3 P en M tn 2 -4 c LO O UJ O O ~ (Ji T s| i ' ° 2 m«i t~* o m i o i NJ 1 00 0

MM) s5 nm i Elevation (Feet) Ul ^ ^ 01 Oi O 01 ? ? «!.?fl MM;! l.

jn^U^U'j;

3.1 !ff|ii>lfe^' GRAPHIC i! ji: :; J;|j||f!{!iv^|fl i L_1 0 en n l|!?îOM:n ;iV > i ÎHB ri m ? 0 J T m 0 0 -5 " '72 ?i,i ,i'.^: '':'3!, ,",'. U) ii!','!'1 f ! T ''MM! j ? \ !!'.': - I - ill M i ! , 03 f en o 'i; :!hs ft q So H"3 *~^ (!lhli:|fj' v"tl! i H (D 01 2 £d 0 en M CO I-1 5 o uo u> n 3 01 -j SG liM.ililMJIi'.l'i O H 01 H< o > (D ;D !|!H:I i^^n ft (D b1 1 3 § u> S !|i;:','.i'i''. '. ^ » §! t'lj (- = nii" r* ; ;ii -Mj ^ f ! ! l LI |I; 0i ro U) -J vD 00 O 0 û^Sfe' i" îi'.'iiiiiMi'/ii'iVi m i'-i,'! 1 f,Vi^ 1 , I* ,'ffl p 2 ' -i' ' i'-i: - ; 'i, v.i ii i'i Elevation (Feet)

o GO O O

o a | OB

o z NJ m O O m O X OB z: M a Cfi Z oo cn w b a CO (T) 01 S 2 m > O 3 M O H Z 53 p C/i Mz O~l ui O 0 oo rn o UJ o Ln -z. H 0 T O 53 K «c^ rn C o Elevation (Feet) t tn s: 0 > (_n . r U1 r L_ _J_ O H Ift ! I 1 t i : !i IP; :n: 1 I-'K.'- .j'-li 1 00 o o £>. ij^ '! liV,1 ' o BMMBJ I ' , I!' 'j rs w jjl! -: Oi 1- y 5 ; Q.I CJ i ,!' 1*1 § i . Elevation (Feet)

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o CT> O

(_» 0 B S Z T) OB T| 0^ 1 _ M " n

C 1 ' 3 S o n -J z ro -^ o m o"2 n rf m 0> O n 5 cn U) 9

v ROJECT S en Q > O -3 Tl Z (_ J O 0 H LTl Z pd C cn PI I z O UJ £>. n 00 LTI o n: o T 0 ^ £ ^ 2 0 °?J ^

MM 0 s: ° M O ^ ffl :

O 1 o & o 1 oc 0

MM n S i i 1 Elevation (Feet)

o o

o 4 ro m O O

cn J n- n-cu p- O 3

cn O > O

M O H z: U> e> n O I-1 3 o o ^ 1 O ra o

tn O

O I M .£> t-1

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pH-r-M'ViiifH( tei 'V-ii-i 1 U- Elevation (Feet)

r tn o

£>

o o a F z 3 < ,_, M

o en :r n > * M o z m ro U 9 O o ^ rt m (D 0 OB cn «< -~^ a u» ~ ____i * a f * 2 O m . -i > 0 3 *~3 *~Q z M p O H ij"i 25 ?d CO M 00 0I-1 25 o »£>. nnO -r O ^-, 1 , 25 Q 3g b H > ,^w «-y^ NJ o 5; mmmm O > t~* ^ Im t ' o i U) £.. o t ' 1 CD O O

_* _ n 5 i

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LH O NJ O o

NJ I ' O

o a

iz OB

O X NJ m NJ O O m 0 OB

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DATE: o i o NJ 1 ** 00 O 0

11 5

§fit i Elevation (Feet) U1 o NJ Ol O

NJ & O

o a

Jz OB

MMB 5=3 O N) X ^J m o O rr m ^> O ^ OB 01

rt- a QJ C^ H- 9 O a -jl b 3 2 m [^ O H 0 Z o p § -d

0 ^ 1 NJ 00 u, Ul o zL 0 ^ T H 2 ? \ o o 0 4^ "3 ^ UJ ^

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0 i LJ NJ 0 vO 1 O 00 o

Tl 5

m S

1 Elevation (Feet) ui ui p o o

o o a

z OD

M o CO z O m O m O OD s rf HH>H O a en d ^ 2 > O o i-H "^ H 0 -3 Z Z xd 0 en rr! on -c^ n UJ (3 UJ ^ o i o ^j o LTl T ^S0 » 2 1-3 c L*J "" o § r1 ^MM r- O ^

m o i UJ O 1 00 o

m^mm

11 O

§m §

i c! x' !i Stations 4150 4.1 GO 4370 4180 4190 -1400 I i

Asphalt Over Concrete Fill

55-1

GRAPHIC SCAF.B (Meters) 1 1 J 1 0 1 2 3

LOG OF TRENCH (NORTH WALL) STATIONS 4350 TO 4400

DRAWN BY: ch | CHECKED BY: QR | PROJECT NO: 501. 1411-GFOl ] DATE: 10-30-80 | FIGURE NO: - Elevation (Feet) tn LTI O Ul

O O

.: *' Vi'-i» ! 1 r S :' i ' '

o OB 1 rr 3

o X 10 h ? ffl 0 0 -D m O cn

U) 1 n-en £j rt H- O 3D 2 cn b > CO H O q M TJ 0 Z «-3 p cn po <_n a u> O >t» z o I 1 £* n u> O 3 ui o ^ T H 2- o 0 ° 0 )PO -1 b

Ul ,- o g ^ H t^ O > % , H m H-1 O 1 U) ii 0 1 CD 0

n Q < i ffl u.,!1 !:- §

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^^ CD O " s 1 o z fsj ^^*" m ^^ O 05 m (D 0 h{ 01 cn

Ui $ mmmm en b .g i-3 O a ^ O 2 i i *r5 m O -r z cn pd w fc. p j^ n C*. (_n Ul Z CO O o O u; -3 S ~(_n 0 0 ?3 1 >c^ 1-3 O Ui 33 fr] O b o s; tr1

0 i u» o

00 o

1MM 5

i Elevation (Feet) tn in O en O O

tn (- O

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n 5 I i

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OB < O O 73

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11 5 m ! > l O ,!, VvS;-{-:^ I.| t^MMiil Elevation (Feet) ui ui

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MM n z -J S O o rr m cD O ^ OB cn cn i rt MMBI

M a cn b 2 i-3 (D m ^ o M T| O |H Ul n CD o *» "Z O CTi O NJ m a: Ul o 1 -3 ^ On 0 0 o 4^> 1-9 ( -j a: o o s; MMM tr1 O t^ 1*1

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O o a i OB 2 M t-» J O cn O rr o ^H w O Z ro , _ -^ NJ III 2 O o O m 0 ro OB cn cn rr U) GJ r* $ H- t-t MBBBI O d cn o a i-3 > O 2 t-3 *^3 i _j O ^ z o cn w 01 £> n o -0 ffi U) I 1 0 O U) o -^ 01 2 fT] H O 1 O » o >~3 M it^ nc o ~o K-1 01 s: O Js*

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o a zJ OB < M O rj cn :r O > f HIM o 03 mX 2 ^v) o Q O x rt m fO 0 n OB cn en rt 4V flj rt MM H- » O a f 3 cn O cn em H O o ^ H O M ^ 0 Z H p** cn S3 <_n M 00 0 ^. z U) oo n o LO o z U] o T 3 2 il^ 0 0 c * 3 I- S K 0 33 MM > 0 f4 > £^ 1*1 (- O u> »- i 00 00 ^ 0 o

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X LTl O Stations 4850 4860 4870 4880 4890 4900 I I___ i I ___I

70^ Asphalt Over Concrete

65-

t! 60. 0) Jjl!^.!^v'.0/:-VU«;i'0 o^iravel^ ? » jr'A^^sf

Ho 4J Qt : _= . ...;. ; --.;. rtJ 0) 55-

50J

GRAPHIC SCALE (Meters) L J

LOG OF TRENCH (NORTH WALL) STATIONS 4850 TO 4900

PR AWN BY: ch | CHECKED BY: 6P | PROJECT NO: 50135H-GE01 | DATE: 10-31-80 | FIOUHE MO A ~ Elevation (Feet) 01 CT* CT* o O Ln C o o

o a

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O X m O X ffl o OB cn rt SJ ao cn o 2 H O m -3 O O -4 o Z 2 >-3 O cn 50 ra cn PV 2 O *x) n h-' o rn UJ o H 2 l 0 0 £1 50 6 {Q JU ( Ul o s: __ f 0 £ H ffl (- !- 1 U) 1 00 o

11 5 im

i Ln CT> O Ln

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i > O > i i i APPENDIX B

KEY TO LOGS AND LOGS OF TRENCH IN CORONADO, CALIFORNIA KEY TO LOGS

HOLOCENE AEOLIAN DEPOSITS

Very porous, friable, pale brown silty very fine-grained sand

HOLOCENE ALLUVIAL DEPOSITS

Porous, friable, light reddish-brown silty fine sand; poorly formed soil profile in upper 5cm (12 inches) consisting of grayish brown, slightly clayey silty sand containing concentrations of manganese staining. Gradational "A" to "C" profile with no distinct "B" horizon.

PALEOSOL

Dark reddish-brown clayey sand. The paleosol is hard, and has a poorly to moderately well- developed, medium angular to crumbly structure and thin clay skins. Manganese oxide staining is concentrated along base of this paleosol.

LATE PLEISTOCENE MARINE DEPOSITS

Thin to moderately bedded, light'gray to light reddish-brown, silty fine to coarse grained sand. The light gray beds are finely laminated friable sand, whereas the light reddish- brown beds are lightly cemented with iron oxide.

LITHOLOGIC OR GEOLOGIC UNIT CONTACT

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FAUNAL ANALYSIS

by Thomas A. Demere and Kenneth M. Winterstein Department of Geology, Natural History Museum San Diego, California FAUNAL ANALYSIS

Downtown San Diego - Pleistocene Faunas

Introduction

Pipeline excavations in the downtown area of the City of San Diego exposed fossiliferous marine sands that are the subject of this report.

Ms. Dorian Elder of Woodward-Clyde Consultants made collections from these deposits during March and June of 1980. A total of four separate collections were examined; three from a series of localities along

E Street between Columbia and State Streets and one from Broadway near its intersection with 2nd Street. These localities are plotted in

Figure 1 and have been assigned the following San Diego Society of

Natural History (SDSNH) locality numbers: 3061 (= WC 570), 3062 (= WC 490),

3063 (= WC 510), and 3064 (= WC 2340). Elevations for these localities as provided by Elder are as follows: 3061 (II 1 above sea level),

3062 (II 1 above sea level), 3063 (4 1 above sea level), and 3064 (31 T above sea level).

Methods

The bulk fossil material with matrix was air dried and screened through a series of sieves producing the following size fractions: ^4 mm,

^2 mm, ^.85 mm, and ^ .85 mm. All size fractions were examined for fossils both megascopically and microscopically. Recovered fossils were identified, counted and curated into the collections of the Natural

History Museum where they are available for further study.

C-l County Ce (13 (13 C 'IEGO fl> 3

O o

Figure 1. Location map of Pleistocene fossil localities (SDSNH) in the downtown area. Map is taken from the USGS 7.5' Point Loma and National City Quadrangles (scale 1:24000). Faunal Analysis - Downtown San Diego Page 3

In counting specimens two pelecypod valves were counted as one individual. In the case of fragments only hinges were counted for pelecypods and apertures for gastropods.

The faunas were compared with previously known fossil assemblages from the San Diego area.

Results

A total of fifty-one (51) species of marine mollusks (24 gastropods and 27 pelecypods) were identified from the four localities. These are listed in Table I along with counts and relative frequency data. All fossil specimens retain their original shell material.

Localities 3061, 3062 and 3063 contain faunas so similar both in terms of species present and relative frequencies that they can be considered members of a single faunal unit. This lumping is also supported by the similar lithology at each locality, i.e., greyish-brown, well-sorted, subangular, medium grained, unconsolidated fossiliferous sand.

The characteristic species in the E Street faunal unit include:

Acteocina culcitella, Caecum californicum, Crucibulum spine-sum, Nassarius tegula, Turbonilla tenuicula, Psammotreta viridotincta, Tagelus californianus

Tellina meropsis, Chione californiensis and Felaniella sericata. Of these taxa, only the last two were also encountered in the collection from 3064.

This fauna, from Broadway, contains the following characteristic species:

Turritella gonostoma, Argopecten cf. A. aequisulcatus , Diplodonta subquadrata,

Lucinisca nuttalli, Pecten vogdesi and Chione californiensis. The lithology at 3064 consists of a reddish-brown, poorly sorted, subangular, coarse to

C-3 TABLE I. Page 4 FAUNAL LIST OF FOSSILS DOWNTOWN AREA SAN DIEGO CITY

N = number of specimens counted per species; % = relative frequency of species within individual localities. Counts are based on two hinges per individual pelecypod specimen and one aperture per individual gastropod specimen.

LOCALITIES we 570 WC 490 WC 510 WC 2340 SDSNH 3061 SDSNH 3062 SDSNH 3063 SDSNH 3064 N (%) N (%) N (%) N (%) Gastropoda Acteocina culcitella (Gould) 12 (1.9) 8 (1.3) 26 (3.4) Acteocina cf. A. harpa (Dall) 2 (.3) Acteocina sp. indet. 12 (1.9) Alabina tenuisculpta Carpenter 1 (.2) Alabina tenuisculpta phalacra Bartsch 4 (.5) Barleeia cf. B. calif ornica Bartsch 1 (.2) Caecum calif ornicum Dall 15 (2.4) 14 (2.2) 12 (1.6) 2 (.9) Cerithidea californica (Haldeman) 9 (1.4) 5 (.8) 8 (1.0) 2 (.9) ICerithidea cf. C. californica (Haldeman) 1 (.5) Cerithiopsis carpenteri Bartsch 1 (.2) 2 (.3) Crucibulum spinosum (Sowerby) 10 (1.6) 5 (.8) 4 (.5) Cylichna cf. C. veleronis Strong & Hertlein 1 (.2) lEupleura muriciformis (Broderip) 1 (.2) Gastropoda; fam. , gen. et sp. indet. 2 (.9) Melampus olivaceus Carpenter 1 (.1) Nassarius tegula (Reeve) 15 (2.4) 22 (3.5) 26 (3.4) Odostomia (Menestho} sp. indet. 1 (.2) Odostomia cf . O. laxa Dall & Bartsch 1 (.2) Odostomia (Salasiella) sp. indet. 1 (.2) Odostomia sp. indet. 2 (.3) Olivella sp. indet. 1 (.2) Polinices reclusianus (Deshayes) 1 (.9) Teinostoma sp. indet. 1 (.2) Turbonilla tenuicula Gould 18 (2.9) 12 (1.9) 6 (.8) Turritella gonostoma Valenciennes 92 (43.4) C-4 Table I (cont.) LOCALITIES Page 5 WC 570 WC 490 WC 510 WC 2340 SDSNH 3061 SDSNH 3062 SDSNH 3063 SDSNH 3064 N (%) N (%) N (%) N (%)

Pelecypoda Aligena cerritensis Arnold 2 (.3) 3 (.5) 1 (.1) Anomia peruviana Orbigny 1 (.2) 1 (.5) Argopecten cf. A. aeguisulcatus (Carpenter) 21 (9.9) Cardiidae; gen. et sp. indet. 1 (.2) Chione callforniensis (Broderip) 57 (9.1) 7 (1.1) 87 (11.3) 63 (29.7) Chione fluctifraga (Sowerby) 1 (.2) Chione cf. C. gnidia (Broderip & Sowerby) 1 (.1) Corbula luteola Carpenter 2 (.3) 2 (.3) Crassinella branneri Arnold 2 (.3) 2 (.9) Cryptomya californica (Conrad) 1 (.2) 1 (.1) Diplodonta subguadrata Carpenter 4 (1.9) Donax californicus (Conrad) 1 (.2) 1 (.2) 3 (.4) Felaniella sericata (Reeve) 417 (66.6) 487 (77.8) 535 (69.8) 3 (1.4) Laevicardium cf. L. substriatum (Conrad) 1 (.2) Lucinisca nuttalli (Conrad) 8 (3.8) Mactra californica Conrad 2 (.3) Megapitaria squalida (Sowerby) 1 (.1) Nucula exigua Sowerby 1 (.2) 1 (.2) 1 (.1) 1 (.5) Ostrea lurida. Carpenter 1 (.2) 3 (.5) 1 (.5) Pecten vogdesi Arnold 7 (3.3) Pi tar newcombianus (Gabb) 1 (.5) Protothaca staminea (Conrad) var. 1 (.1) Psammotreta viridotincta (Carpenter) 10 (1.6) 8 (1.3) 5 (.7) Saxidomus nuttalli Conrad 1 (.2) Tagelus californianus (Conrad) 9 (1.4) 13 (2.1) 9 (1.2) Tellina meropsis Dall 21 (3.4) 26 (4.2) 26 (3.4) Trachycardium cf . T. panamense (Sowerby) 1 (.2)

Dther Bryozoa 3 (.5) Decapoda; crab claw 1 (.2) Echinodermata; sea urchin spine 1 (.1)

Totals = 626 626 767 212

Total number of specimens = 2231 C-5 Faunal Analysis - Downtown San Diego Page 6

fine grained, poorly indurated, argillaceous, fossiliferous sand. In places this locality contains calcareously cemented sand pockets that display external molds of mollusks. The fine grain fraction at this locality serves to separate it from the localities along E Street.

Age and Correlation

The modern aspect of the faunas (i.e., all species are extant) together with the lack of characteristic Pliocene species suggests a

Pleistocene age for these four localities. In addition, Chione californiensis, a common taxon at each locality, appears to be stratigraphically restricted to the Pleistocene Epoch.

As concerns the E Street faunas, amino-acid analysis of Chione shells from 3061 and 3063 have yielded absolute ages of 300,000 years B.P. and between 200 and 300,000 years B.P. respectively for these two fossil assemblages (Bada, letter to Elder, 16 May 1980). This slight temporal distinction is not supported by faunal and lithological evidence which together suggest contemporaneity. Kern (1977, and personal communication) recognizes at least three distinct temporal intervals in the San Diego

Pleistocene including his Bird Rock Terrace at 80,000 years B.P., the

Nestor Terrace at 120,000 years B.P. and as yet, an undescribed faunal unit at 200-250,000 years B.P. It is to this oldest unit that the E Street faunas are correlated. Additional faunas in and around the downtown area that fall into this temporal framework include a small fauna from G and 1st

Street (SDSNH 3019) which has been dated at 200 to 300,000 years B.P. and a series of faunas from deposits along Harbor Drive near Indian Point

C-6 Faunal Analysis - Downtown San Diego Page 7

(SDSNH 0054, 3065 and 3074). One of these (0054) has been dated at

210,000 years B.P. (Masters, letter to Demere, 28 August 1980). All of these localities contain a distinctive warm water faunal element characterized by the following taxa: Eupleura muriciformis, Dosinia ponderosa,

Felaniella sericata, Psammotreta viridotincta and Tellina meropsis. It is this warm water element that most closely ties these various faunas together. It should be mentioned that all of these assemblages reflect a protected marine facies.

The Broadway fauna is distinct from those discussed above and appears to correlate with an older and very poorly studied group of Pleistocene deposits which are recognized from only a few isolated outcrops in the

San Diego area. Three species serve to separate this fauna from those at

E Street; Turritella gonostoma, Argopecten cf. A. aequisulcatus and

Pecten vogdesi. In addition, the condition of the shells, many heavily bored by sponges, appears to be an important characteristic of this fauna.

Interestingly a small assemblage of fossils from Broadway and 3rd Street

(SDSNH 2991) collected in 1918 is identical to the above described fauna.

Kern (1977) reported on a molluscan fauna (SDSU 2530) from Loma Portal at the north end of Point Loma and although at the time of publication he considered this fauna to be a Nestor correlative he has since received amino-acid data placing it at older than 500,000 years B.P. (Kern, personal communication). Stephens (1929) also reported on a fauna from Loma Portal

(SDSNH 0070) and both he and Kern noted the occurrence of Turritella gonostoma in these deposits. This taxon is a locally extinct southern extralimital species that today lives throughout the Gulf of California south to

C-7 Faunal Analysis - Downtown San Diego Page 8

approximately the latitude of Peru. It is suggested here that this taxon may, with further collecting and study, prove to be an index species for these older terrace deposits.

Another characteristic species in the Broadway fauna, Pecten vogdesi, may also prove to be somewhat of a faunal indice for these deposits.

Hertlein and Grant (1972) in their discussion of this taxon report it from a deposit at 32nd Street near Logan Avenue in East San Diego.

They considered this deposit to be Pliocene in age based on rather nebulous data but added that, "Except for its occurrence in the San Diego Formation

Pecten vogdesi has been reported from southern California only in beds of

Pleistocene age" (p. 182).

A collection of fossils from 32nd Street (SDSNH 3020) housed at the

Natural History Museum contain common Chione californiensis and Lucinisca nuttalli. The Chione shells display severe boring by sponges as at the

Broadway locality. Kern (personal communication) received an amino-acid date for this locality in excess of 600,000 years B.P. and has concluded that it represents an older Pleistocene terrace deposit.

Amino acid analysis of Chione shells from SDSNH 3064 have produced allo/iso ratios in excess of the limits of this dating technique (i.e., greater than 300,000 years B.P.) (Masters, personal communication). Although this date is not an absolute figure, it does serve as a relative measure of age. It is suggested here that the Broadway fauna and those at Loma Portal and 32nd Street are correlative and representative of an older Pleistocene interval previously unrecognized in the San Diego area. Interestingly, these three localities occur at roughly the same elevation; approximately

30' above sea level.

C-! Faunal Analysis - Downtown San Diego Page 9

Paleoenvironment

The following discussions on the paleoenvironmental aspects of the

downtown faunas are based on ecological data for living molluscan species.

Exposure.- Faunal elements in the E Street assemblages as well as those

from Broadway suggest protected marine conditions. There are no strictly

exposed coast species in either faunal group. The species Cerithidea californica, Nassarius tegula and Tagelus californianus from the E Street

faunas are today restricted to the quiet waters of bays or estuaries.

In the Broadway fauna the species Cerithidea californica and Argopecten

cf. A. aeguisulcatus suggest similar restrictions.

A simplistic but useful model for generating these protected marine

conditions is given in Figure 2. In this model coastal San Diego is

flooded by interglacially high sea levels creating an enlarged Pleistocene

San Diego Embayment and isolating Point Loma as an island. Those areas in

the lee of this Loma Island, including the present downtown area, would thus have been protected from direct wave attack.

Substrate.- The dominant infaunal pelecypod species in the E Street

assemblages suggest a sandy bottom habitat. The most abundant species,

Felaniella sericata, lives today only in sand. This is consistent with

the nature of the sediment in which these faunas are preserved. A few rare

species requiring a firmer substrate together with others requiring a muddier substrate suggests some mixing of taxa from these habitats.

In the Broadway fauna the dominance of the gastropod species,

Turritella gonostoma, points to a finer-grained substrate for this deposit.

This species today is commonly found on mud or sandy mud bottoms. Other species

C-9 Faunal Analysis - Downtown San Diego Page 10

PRINCIPAL FOSSIL LOCALITIES 1. Pacific Beach Soledad 2. Bay Point Headland 3. N.W. Mission Bay 4. Tecolote Creek 5. Loma Strait 6. Ostrea bank, E. Loma Is. 7. Exposed coast of Loma Is 8. Spanish Bight Mission 9. San Diego City Embayment 10. Glorietta Bay 11. Indian Point 12. Border locality

SAN DIEGO +8,....,.. --...

''v-Embayment

Figure 2. Map of southwestern San Diego County showing upper Pleistocene fossil localities and the approximate configuration of the corresponding shoreline (after Valentine, 1961, p. 353).

C-10 Faunal Analysis - Downtown San Diego Page 11

in the Broadway fauna, however, require sandy substrates and it appears

that these two substrate types contributed molluscan species into a common post-mortem accumulation site. The greater fine grain fraction at 3064 and the poor sorting may also reflect this mixing of habitats.

Water Depth.- The majority of the molluscan species recovered from the

E Street localities suggest a littoral to inner sublittoral environment.

Several taxa, including Nassarius tegula, Chione californiensis and

Tagelus californianus are characteristic of the littoral zone in present day bays and estuaries. The two gastropods Cerithidea californica and

Melampus olivaceous have very restricted depth ranges, being confined to the upper portion of the littoral zone. Their occurrence with species more commonly considered sublittoral imples that post-mortem transportation carried these shells into the sublittoral.

The Broadway fauna suggests water depths somewhat greater than those at E Street. The species of pectens (Argopecten and Pecten) commonly occur in the sublittoral regions of bays or on protected bottoms offshore. The several littoral species in this fauna suggest that post-mortem shell transportation was at work here as well.

Salinity.- The majority of the species recovered from the E Street and

Broadway localities reflect normal marine salinities. Only Cerithidea californica and Melampus olivaceous are indicators of brackish water conditions. As discussed earlier, these species were probably transported after death, in this instance probably from a restricted back-bay habitat out into the more open marine areas of the embayment.

C-ll Faunal Analysis - Downtown San Diego Page 12

Temperature.- A strong warm water element is represented in both the

E Street and Broadway faunas. At E Street this element is characterized by abundant Felaniella sericata, common Tellina meropsis, frequent

Psammotreta viridotincta and rare Eupleura muriciformis and Megapitaria sgualida.

At Broadway, the characteristic warm water species include common

Turritella gonostoma, frequent Pecten vogdesi and rare Diplodonta subguadrata

The remaining species in both faunal groups all include San Diego within their present zoogeographical range.

Summary

The four fossil collections examined can be divided into two distinct faunal groups of Pleistocene age.

Those from E Street are considered contemporaneous and appear to be correlative with other known fossil deposits in and around the downtown area. Chione shells from these deposits have been dated by amino-acid analysis at 200 to 300,000 years B.P. The E Street faunal group lived under protected marine conditions within the Pleistocene San Diego Embayment.

The majority of its member species lived infaunally on sand bottoms within or just below the littoral zone. Post-mortem transportation probably carried their shells into the sublittoral where they accumulated with those species inhabiting this depth range. The presence of several southern extralimital species in this faunal group indicates that water temperatures were somewhat warmer in this embayment than at present.

C-12 Faunal Analysis - Downtown San Diego Page 13

The faunal group from Broadway appears to be older than the E Street group based on amino-acid analysis of Chione shells (i.e., greater than

500,000 years B.P.). This fauna contains several characteristic species not found at E Street (e.g., Turritella gonostoma and Pecten vogdesi} which allow for correlation with deposits at Loma Portal and 32nd Street.

Together these three localities represent an older and previously unrecognized Pleistocene terrace accumulation in the San Diego area.

In terms of environment, the Broadway fauna lived subtidally on sand and mud bottoms. Several strictly littoral species suggest mixing of shells from this depth zone with the more common sublittoral species.

VW AJL

Thomas A. Demere, Assistant Curator Kenneth M. Winterstein Department of Geology Department of Geology Natural History Museum Natural History Museum

C-13 Faunal Analysis - Downtown San Diego Page 14

References

Kern, J. P. 1977. Origin and history of upper Pleistocene marine terraces,

San Diego, California. Geol. Soc. Amer. Bull. 88:1553-1566.

Hertlein, L. G. and U. S. Grant, IV. 1972. The geology and paleontology

of the marine Pliocene of San Diego, California (Paleontology : Pelecypoda)

San Diego Soc. Nat. Hist., Mem. 2(pt. 2B):135-411.

Stephens, F. 1929. Notes on the marine Pleistocene deposits of San Diego

County, California. San Diego Soc. Nat. Hist., Trans. 5(16):245-256.

Valentine, J. W. 1961. Paleoecologic molluscan geography of the

Californian Pleistocene. U. C. Publ. Geol. Sci. 34 (7):309-442.

C-14 APPENDIX D

REPORTS ON AMINO ACID AGE ESTIMATES OF QUATERNARY MOLLUSKS

By John F. Wehmiller Associate Professor Department of Geology University of Delaware Newark, Delaware 19711 And Jeffrey L. Bada Scripps Institution of Oceanography University of California, San Diego La Jolla, California 92093 2340 2370

REFERENCE MAP FOR APPROXIMATE LOCATION OF AMINO ACID AGE DATING

D-l REPORT TO WOODWARD-CLYDE CONSULTANTS 3467 Kurtz Street San Diego, Calif. 92110 Attn: Mr. E. Artim

AMINO ACID AGE ESTIMATION OF QUATERNARY MOLLUSKS FROM A TRENCH IN DOWNTOWN SAN DIEGO

W-C Project No. 412381-OEC2 Cross Ref. No. 50135H-GE01

From:

John F. Wehmiller Assoc. Prof. Dept. of Geology University of Delaware Newark, Del. 19711 302-738-2926

Sept. 22, 1980

D-2 INTRODUCTION: This report presents amino acid enantiomeric (D/L) ratios, and age estimations, for five samples of the mollusk Chione from a Quaternary marine deposit exposed in a trench in downtown San Diego, California. The exact locations of the samples are presented in the Appendix, in which the letter of transmittal of samples from Mr. Ernest Artim, Wood ward-Clyde, to the Principal Investigator is included. The methods of analysis and data interpretation are discussed in four primary references that will be used in discussions to follow: Wehmiller et al, 1977; Lajoie et al, 1980; Wehmiller and Belknap, 1978; Wehmiller and Emerson, 1980. Reprints of the latter two papers are included with this report. Enantiomeric ratio data are reported in Table 1. These ratios have been determined on total hydrolyzates of approx. 1 gm fragments cut from the hinge area of each shell sample. Ratios are those determined from peak height measurements from at least two chromatograms of each sample.

AGE ESTIMATES: Age estimatations are made using a combination of relative and semi-absolute kinetic model interpretative procedures. Previous studies have indicated that Chione racemization kinetics are similar to those for Protothaca (Wehmiller et al, 1977; Lajoie et al, 1980), so it is assumed that the Chione data of Table 1 can be interpreted in terms of Protothaca

D-3 -2-

kinetic curves presented by Lajoie et al (1980: Figs. 2,3,& 9); Wehmiller et al (1977: Fig, 14); Wehmiller and Belknap (1978: Fig. 1); Wehmiller and Emerson (1980: Fig. 3). In Figures 1-3, the data of Table 1 are plotted in the intrageneric relative racemization format of figures 9-11 of Lajoie et al (1980). These plots indicate that two age groups are represented by the results reported herein: localities 490 and 563 fall into the younger age group, while locality 2370 is distinctly more racemized and therefore distinctly older. Simple comparison of these results with those for a local calibration site, the 120,000 year Nestor Terrace on Point Loma, San Diego harbor, indicates that the samples analyzed here are significantly ( 2x or more) older in age than the Nestor Terrace. Figures 1-3 include data for Protothaca from the Nestor Terrace (marked as "N" on the horizontal axis). In Figure 4, the leucine data for the Nestor Terrace (and two other Pacific coast calibration localities) are compared with the results in Table 1 (a full discussion of this figure is found in Wehmiller and Emerson, 1980), Again, the great age (relative to the 120,000 Nestor Terrace) of the analyzed localities is apparent. For absolute age estimates, the kinetic model of Wehmiller et al, 1977 and Wehmiller and Belknap, 1978 is used. The well-dated Nestor Terrace (120,000 + 10,000) serves as a local calibration site for all amino acid dating in the San Diego area, as it can be reasonably assumed that the Effective Quaternary Temperatures for sites in this area

D-4 -3-

have all been quite similar (generally the assumption is made that sites with equivalent present-day temperatures have had Effective Quaternary Temperatures within about 0.5° C. of each other - see Wehmiller et al, 1977 for further discussion). The kinetic model age estimates for the data groups defined from Figures 1-4 are 360,000 + 50,000 years and 560,000 + 75,000 years. These age estimates are derived from the kinetic curve for Protothaca at 13.5° C. (P-13.5 of Wehmiller et al, 1977). The uncertainties estimated for these ages are a results of both the analytical uncertainty at a given locality and an assumed temperature uncertainty (relative to the calibration locality) of + 0.75° C. The leucine model age estimates presented here are also supported by other, more qualitative age estimates derived from glutamic acid and valine data, compared with the kinetic curve of Lajoie et al (1980: Figure 3) for these amino acids,

SUMMARY: Five shell samples have been analyzed for amino acid enantiomeric ratios, and two age groups are apparent in these data. The younger group, with an age estimate of approximately 360,000 + 50,000 years, lies near the western end of the trench from which the samples were collected The older group, with an age estimate of about 560,000 + 75,000 years, lies to the east of the younger samples

D-5 -4-

and stratigraphically lower (E. Artim, personal communication). It is likely that additional analyses, including repeats, will be performed in the next two months in order to improve the precision of the reported data. These results, if obtained, will be communicated to Woodward-Clyde. More importantly, it would be desirable to analyze samples from stratigraphic positions intermediate to, or lower than, the localities reported herein.

D-6 References

Lajoie, K. R., Wehmiller, J. F., and Kennedy, G. L. (1980) Inter- and intrageneric trends in apparent racemization kinetics of amino acids in Quaternary mollusks, in Biogeochemistry of Amino Acids , P. E. Hare et al, eds., John Wiley & Sons, New York, pp. 305-340. Wehmiller, J. F. et al (1977) Correlation and chronology of Pacific coast marine terraces of continental United States by amino acid stereochemistry - technique evaluation, relative ages, kinetic model ages and geologic implicaitons. U. S. Geological Survey Open-File Report 77-680, pp. 1-106, 11 Tables, 18 Figs. Wehmiller, J. F. and D. F. Belknap (1978) Alternative kinetic models for the interpretation of amino acid enantiomeric ratios in Pleistocene mollusks; examples from California, Washington, and Florida, Quaternary Research 9_, 330-348. Wehmiller, J. F. and W. K. Emerson (1980) Calibration of amino acid racemization in late Pleistocene mollusks: results from Magdalena Bay, Baja California Sur, Mexico with dating applications and paleoclimatic implications, Nautilus 94, 31-36.

D-7 Table 1 Enantiomeric Ratio Data in Chione Samples, Woodward-Clyde Trench San Diego, California Locality Amino Acid*: Sample No. Leu Glu Val Ala Pro Phe Asp Allo/iso Method** 490-1 80-82-1 .66 .50 .50 .93 nd .68 .74 nd P

563-1 80-137-1 .72 .52 .47 .80 .77 .74 .73 .73 B 80-137-2 .66 .48 .49 .87 nd .63 .70 nd P 2370 80-138-1 .79 .68 .68 1.02 .86 .75 nd nd B 80-138-2 .84 .73 .67 .98 .86 .86 .83 1.18 B

*Amino acid abbreviations: Leu = Leucine; Glu = Glutamic acid; Val = Valine; Ala = Alanine Pro = Proline; Phe = Phenylalanine; Asp = Aspartic acid; Allo/iso = alloisoleucine/isoleucine **Method - two chromatographic procedures used, one using isopropyl derivatives (P) and one using butyl derivatives (B); see references for discussion. Comparability of results from two methods is quite good, except for the data for phenylalanine. nd = not determined Figure 1: Leucine-glutamic acid trends (from Lajoie et 31,1980) with Table 1 data plotted for comparison. Note two apparent age groups. Nestor Terrace Calibration data indicated.

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D-9 Fiqure 2:- Leucine-valine trends (from Lajoie et al, 1980) with Table 1 data plotted for comparison. Note two apparent age groups (same samples fall into these groups as in the case of leucine-- glutamic acid), Nestor Terrace calibration data indicated.

.8 PROTOTHACA

0 0

D-10 Figure 3: Leucine-proline trends (from Lajoie et al, 1980) with Table 1 data plotted for comparison. Note two apparent age groups (same samples fall into these groups as in the case of leucine-glutamic acid). Nestor Terrace calibration data indicated

.9- PROTOTHACA PRO-LEU

CAYUCOS

M^ .**>

HOLOCENE

0 ,2 .3 .4 .5 .6 .7 .8 .9 D/L LEUCINE

D-ll Figure 4: Figure 3 of Wehmiller and Emerson (1980) i.o- (reprint enclosed - see for full discussion) with leucine data from Table 1 (mean values 200 ka for each apparent group) plotted for .9- comparison. Solid line is isochron for 120,000 year U--series dated localities. I20ka .8' 80 ka .7 .6- UJ .5- .4- Q .3- .2 .1- 0- Loc: C, 35.3C N.32.7' MB, 24.6° I I I ~T \ T ' I ' 1 10 12 14 16 18 22 24 PRESENT MEAN ANN. TEMP, °C UNIVERSITY OF DELAWARE NEWARK. DELAWARE

19711

COLLEGE OF ARTS & SCIENCE DEPARTMENT OF GEOLOGY 101 PENNY HALL December 10, 1980 PHONE: 302-738-2569

Re: Project No. 50135H-GE01 Mr. Ernest Artim Woodward-Clyde Consultants 3467 Kurtz Street San Diego, CA 92110

Dear Mr. Artim:

This letter constitutes a final report of amino acid enantiomeric (D/L) ratio data for five mollusk samples that you sent in late October.

I enclose a copy of your original letter of transmittal of the samples, to serve as locality descriptions for the samples studied. It is understood that additional locality data will be available in the near future. Methods of analysis and data interpretation have been discussed fully in the report that I submitted to you in September 1980, so the interpretation presented here will rely upon the same figures as presented earlier.

Data for the five shells are given in Table 1. One Tivela sample was analyzed in addition to four Chione samples. Previous observations (Wehmiller et al, 1977; Lajoie et al, 1980) indicate that Tivela, Chione, and Protothaca are all kinetically equivalent, within normal analytical uncertainty, so the enantiomeric ratios given in Table 1 can be directly compared without any con versions.

Figures 1, 2, and 3 present the data of Table 1 in relation to the intrageneric relationships (Lajoie et al, 1980) and the Chione data previously re ported. These figures demonstrate the apparent internal consistency of the intrageneric relative racemization kinetics of the data in Table 1, and the figures can also be used to infer relative ages. Locality 102 has yielded enan tiomeric ratios quite similar to those from locality 2370 of the previous report. Localities 101 and 056 have yielded enantiomeric ratios less than those from localities 490 and 563 of the previous report, but greater than the enantiomeric ratios typically observed in the 120,000 year Nestor Terrace samples. Therefore, the results for localities 101 and 056 suggest an age intermediate between 120,000 years (Nestor Terrace) and the 360,000 (+ 50,000) year estimate for localities 490 and 563 as given previously.

Figure 4 (copy of Figure 4 of previous report) shows how the data of Table 1 plot in relation to the leucine kinetic model as presented by Wehmiller and

D-13 Mr. Ernest Artim December 10, 1980 Page 2

Emerson (1980). Kinetic model age estimates, derived from Figure 4 in combination with either Figure 14 of Wehmiller et al (1977) and Figure 1 of Wehmiller and Belknap (1978) (really all are equivalent expressions of the same kinetic model) are as follows:

Locality 102: 560,000 + 75,000 years (same as loc. 2370 of previous report)

Localities 056 and 101: 220,000 + 30,000 years

Uncertainties result from a combination of analytical uncertainty and an assumed uncertainty of + ,75°C. in Effective Quaternary temperature, as dis cussed in the previous report.

I trust that these data will prove of value. Please do not hesitate to contact me if you have further questions. Sincerely,"

John F. Wehmiller Assoc. Prof.

JFW/lb

cc: Thomas White, Contracts and Grants Univ. Delaware Account WCC AA Dating II 4-3-42-2544-01

D-14 vD

CNJ OO O r-

r~- r^.

C"! OC OC

C O O 'O CJ

D-15 Figure 1: Leucine-glutamic acid trends (from Lajoie et al,1980) with Table 1 data plotted for comparison. Note two apparent age groups. Nestor Terrace . Calibration data indicated.

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o aiov

D-16 Figure 2:- Leucine-valine trends (from Lajoie et al, 1980) with Table 1 data plotted for comparison. Note ' two apparent age groups (same samples fall into these groups as in the case of leucine-- glutamic acid). Nestor Terrace calibration data indicated.

.8 PROTOTHACA

.7- VAL-LEU

/flflL

0 0

D-17 Figure 3: Leucine-proline trends (from Lajoie et al, 1980) with Table 1 data plotted for comparison. Note two apparent age groups (same samples fall into these groups as in the case of leucine-glutamic acid). Nestor Terrace calibration data indicated

.9- PROTOTHACA PRO-LEU

.7-

O .6-

CAYUCOS 5- UJ ' o .4 cc Q_ .3- _J Q .2-

HOLOCENE

0 0 .2 .3 .4 .5 .6 .7 .8 .9 D/L LEUCINE

D-18 Figure 4: Figure 3 of Wehmiller and Emerson (1980) i.o- (reprint enclosed - see for full discussion) with leucine data from Table 1 (mean values 200 ka for each apparent group) plotted for .9- comparison. Solid line is isochron ^ for 120,000 year U-series dated localities.,/^ |20ka .8 .7' 80 ka .6- -LU1 .5- .4- Q .3 .2 .1 0- Loc: C.S5.3' N,32.7 MB,24.6 I I I____ 1 1 I j I 10 12 14 16 18 20 22 24 PRESENT MEAN ANN. TEMP.,-°C UNIVERSITY OF DELAWARE

NEWARK, DELAWARE 19711

COLLEGE OF ARTS & SCIENCE DEPARTMENT OF GEOLOGY 101 PENNY HALL PHONE: 302-738-2569

Dec. 31, 1980 Mr. Ernest Artim Woodward-Clyde Consultants 3467 Kurtz Street San Diego, Calif. 92110 Dear Mr. Artim: RE: Project No. 50135H-GEO1 This letter constitutes a final report of amino acid enantiomeric (D/L) ratio data for five mollusk samples, collected from Coronado Island, San Diego, that you sent in early December.

I enclose a copy of your letter of sample transmittal, to serve as a locality and sample description. As we discussed by phone on Dec. 12, I have analyzed one Tivela from sample bag A-l, two Tivela from sample bag B-l, and one Saxidomus from each of sample bags B-2 and C-l. B-2 was collected at the same locality as B-l. Table 1 presents the results for these sample, as well as those for the Tivela sample (80-144-1) from the previous collection at your locality WCC 056 (data previously reported in letter of Dec. 10, 1980), a locality equivalent to that of sample A-l of the present collection. Methods of analysis, data presentation, and interpretation, have been described in my earlier reports. The first point to note is that thejiew results for Tivela samples 80-166-1, 80-167-1 and 80-167-2 essentially duplicate those for the Tivela sample (80-144-1) from locality 056. Therefore the conclusions of my report of Dec. 10 regarding the age of the Tivela samples from Coronado Island remain unchanged. As before, the graphical presentation of these results is shown in Figures 1-3, which also include all the previous results as well. You will note in these data (as well as some of the previous results) that there is some significant scatter in the results for glutamic acid and phenylalanine. This scatter is largely a consequence of the different derivatization procedures, rather than being a problem of reproducibility of the analytical method. The enantiomeric ratios for these two amino acids, using our current chromatographic conditions, are approximately 10-15% lower when determined by the isopropyl (P) method than when determined by the butanol (B) method. The apparent scatter for these amino acids is much less when results for only one analytical method are compared.

D-20 Dec. 31, 1980 2.

The two Saxidomus samples are much more extensively racemized than t^ie Tivela samples. The Saxidomus D/L values (converted to equivalent Protothaca and/or Tivela by the intergeneric regressions given in Lajoie et al, 1980), plot in the same range as the data for Chione from localities 102 and 2370 of the previous reports. It should be noted that these Saxidomus samples are worn fragments (with modest amounts of internal luster apparent on freshly-cut surfaces), in contrast to the well-preserved, lustrous whole Tivela samples reported here. Therefore, the simplest explanation of the Saxidomus results (at least for samples B-l and B-2) is that the Saxidomus samples have been reworked from a deposit roughly equivalent in age to localities 102 and 2370 (i.e., about 560,000 + 75,000 yrs.) and that the Tivela analyses represent the true age of the deposit at the site. As only one sample has been analyzed from bag C-l (no Tivela are in this sample), it cannot be said whether shells of two ages are actually present at this locality as well. Nevertheless, both the preservation condition and the analytical results for the Saxidomus from both B-2 and C-l are quite similar and a reworking origin for sample 80-169-1 seems quite likely. The available amino acid data do not permit a correlation of strata from B-2 to C-l, but rather suggest that the analyzed Saxidomus samples from these sites have been reworked from a common source. Additional analyses from C-l might solve this problem, but the samples now available appear to be just as worn (reworked?) as the one sample (80-169-1) already analyzed. In summary, shells of two apparent ages have been analyzed from Coronado Island: 4 Tivela (one from previous report) : 220,000 + 30,000 yrs. 2 Saxidomus (reworked?) : 560,000 + 75,000 yrs. Age uncertainties are primarily a consequence of temperature uncertainties, as discussed previously.

I trust that these data will prove of value. Please do not hesitate to contact me if you wish to discuss these results. I would be most interested in seeing a copy of your final grant report to the USGS, so that I might learn more about the use of these data.

Sincerely,

John F. Wehmiller Assoc. Prof. cc: T. White, Contracts and Grants Account WCC AA Dating II, 4-374272544-01

D-21 Table 1: Enantiomeric Ratio data in Tivela and Saxidomus Samples, Coronado Island, San Diego, Calif, (abbreviations as in previous report) Sample Bag Sample No. Genus Amino Acid D/L Value Method Leu Glu Val Ala Pro Phe Asp

A-l 80-166-1 Tiv. .58 .38 .35 .82 nd .52 .60 P (splits(: of same sample A-l 80-166-1 Tiv. .58 .43 .36 .81 .66 .65 .63 B extract)

B-l 80-167-1 Tiv. .56 .38 .35 .81 nd .56 .64 P

B-l 80-167-2 Tiv. .58 .36 .35 .85 nd .55 .59 P

WCC056 80-144-1 Tiv. .56 .45 .34 .78 .66 .69 nd B (from( 12/10/80 report) oi NJ B-2 80-168-1 NJ Sax. .86 .80 .67(7) .95 .87 .95 .90 B C-l 80-169-1 Sax. 88 Figures 1-3: Intrageneric plots, showning leucine, glutamic acid, valine, and proline D/L values in all Woodward-Clyde San Diego area samples analyzed during late 1980. New data from Table 1 indicated, previous data shown only as open areas within which data points would fall. Intrageneric plots are for Protothaca; no conversions of Chione and Tivela results have been made in this or previous reports in plotting results for either of these genera, because available evidence suggests that these three are kinetically equivalent (Lajoie et al, 1980). Saxidomus results plotted here have been converted (by regressions given in Lajoie et al, 1980) to "equivalent Protothaca" enantiomeric ratio values before plotting. These regression conversions are roughly 5% reductions in enantiomeric ratio values PROTOTHACA GLU - LEU

.2 .3 .4 .5 D/L LEUCINE D/L VALINE o " o

o r~\

o m I to c U1 o m

CD -

CO PROTOTHACA PRO-LEU

.4 .5 .9 LEUCINE

D-26 AMINO ACID DATING OF FOSSIL SHELL SAMPLES FROM DOWNTOWN SAN DIEGO

One Chione valve, weighing approximately 15-20 grams, from each sample was processed using the procedures described elsewhere (1,2). The results indicated that all the samples had a normal amino acid distribution pattern and were thus suitable for amino acid dating. Previous work (1,2) on the amino acid dating of marine terrace deposits in San Diego County has shown that the following equation can be used to calculate the ages of Chione shells:

Ln . 0 .033 t(age in years) = 1-0.95 allo/iso______(1.95) (3.0 x 10~ 6 yr"1 ) where allo/iso is the measures alloisoleucine isoleucine ratio in the sample. The only limitation in using this equation is that the allo/iso ratio should be less than 0.6. Thus, in this study, this equation can only be used to date sample #470-1 since the other samples were found to have an allo/iso ratio greater than 0.6. Using the above equation and the measures allo/iso ratio of 0.570, yields an age of 200,000 years. This age suggests that this sample represents the interglacial peiod defined by stage 7 in the oxygen isotopic paleotemperature curve (3). This age also indicates that this sample is a member of a group of deposits found throughout San Diego County which have been dated at ~ 200,000 years old (2) . The absolute ages of samples, #150-1 and #570-5, are more difficult to evaluate since the measured allo/iso ratios of these samples are greater than 0.6 and as mentioned ear lier the above equation is no longer valid. However, it is possible to assign relative ages to these samples. Based on the allo/iso ratios, it can be concluded that the age of #470-1 is less than #510-1, which in turn is less than #570-5.

D-27 The allo/iso ratio of #570-5 is almost identical to that determined for Chione shells found at a locality near Morena Blvd. in northeastern Mission Bay (2). This locality was assigned an age of at least 300,000 years or greater by Harrow and Bada (2). It would thus appear that #570-5 is similar in age to the Morena Blvd. deposit. This is a highly significant result since the Morena Blvd. deposit was previ ously the only known representative of this ~ 300,000 year old deposit in San Diego County. The allo/iso ratio of #510-1 indicates it has age inter mediate between those of #470-1 and #570-5. So far, no other deposits in San Diego County have been found which fall into this age range. The allo/iso ratio for #570-1 suggests that it may represent a deposit formed in the early phases of the interglacial period which has an age of ~ 200,000 years. Alternatively, it may have been formed in some period of high sea level which occurred during the 200,000 year interglacial period and the interglacial period represented by the Morena Blvd. and #570-5 deposits. A comparison of the ages of the Chione shells analyzed in this study with the groupings defined in the extensive study of Karrow and Bada (2), is given on the next page.

The total amino acid analyses for samples 2340-1 and 2340-2 look very good, and it is my opinion that these samples are not contaminated and can thus be at least relatively dated. The allo/ISO ratios determined for the two samples are essentially identical which suggests the measured ratios are reliable. The measured allo/ISO ratio measured for this sample is the highest I've found for Chione shells in the San Diego area. They could very well thus provide some important new information about the geological history of this region. Jeffrey L. Bada

D-28 r

THE CORRELATION OF THE'SAMPLES ANALYSED IN THIS STUDY WITH THE GROUPS DEFINED IN TABLE 3 IN KARROW AND BADA (2)

Sample allo/iso 470-1 0.570 510-1 0.624 570-5 0.680 2340-1 0.962 2340-2 0.922

TABLE 3. GROUPINGS OF TERRACE DEPOSITS BASED ON THE SIMILARITY IN ______ALLEU/ISO RATIOS IN MOLLUSC SHELLS Group Age Site alleu/iso (dialyzed) Chione Tivela Mytilus I 100,000 *14 0.30 II 120,000 Torrey 0.34 0.40(0.12) 0.78(0.20) Pines* Crown 0.43(0.15) Point Scripps 0.64(0.24) SDSU318 0.36 SDSU1854 0.39 SDSU2577 0.36 Wo-i X' Del Mar NE 0.58(0.16) Border Field 0.50 0.48 #510-1 early part of the group III "") Tecolote 0.51 interglacial, or a minor InterglacialV Creek t #1 0.55 between grout>s III and IV?? J #130 0.59 #570-5 £h* TV ino.nnn Mo r en a 0.68(0.18) Blvd. 2340-1 and 2340-2 . v n, ooo, ooo Linda Vista 1.2(0.71)

Age determination from extent of racemization in Chione shells; see Masters and Bada (1977). The Tecolote Creek Protothaca results (alleu/iso = 0.58) also support the placement of this terrace in this group, since the rates of racemization in Chione and Protothaca shells have been shown to be similar (Wehmiller and others, 1977).

D-29 r c

REFERENCES

1. Masters, P. M. and Bada, J. L., Earth Planet. Sol. Letters, 37 173- 183 (1977) 2. Karrow, P. P. and Bada. J. L., Geology, 8 200-20^ (1980). 3. Shackleton, N. J. and Opdykc, N. D., Quaternary Research, 3 39-55 (1973)

D-30 APPENDIX E

BIBLIOGRAPHY Albee, A.L., and Smith, J.L., 1966, Earthquake characteris tics and fault activity in Southern California, in Lung, R., and Proctor, R. (eds.), Engineering geology in southern California: Association of Engineering Geolo gists Special Publication, p. 9-33. Alien, C.R., Amand, P., Richter, C.F., and Nordquist, J.M., 1965, Relationship between seismicity and geologic structure in Southern California: Seismological Society of America Bulletin, v. 55, no. 4, p. 753-797. Alien, C.R., 1975, Geological criteria for evaluating seis micity: Geological Society of America Bulletin, v. 86, p. 1041. Alien, C.R., 1976, Responsibilities in earthquake prediction: Seismological Society of America Bulletin, v. 66, p. 2069. Alien, C.R., Amand, P.S., Richter, C.F., and Nordquist, J.M., 1975, Relationship between seismicity and geologic structure in the Southern California region: Seismolo gical Society of America Bulletin, v. 55, no. 4, p. 753. Allison, E.G., 1964, Geology of areas bordering Gulf of California, in Van Andel, T.H., and Shor, G.G., Jr. (eds.). Marine Geology of the Gulf of California A Symposium: American Association of Petroleum Geologists Memoir 3, p. 3-29. Arnold R., 1906, The Tertiary and Quaternary pectens of California: U.S. Geological Survey Professional Paper, v. 47, 264 p. Artim, E.R., Bemis, C.G., Pinckney, C.J., and Smillie, B.R., 1971, Western San Diego County fault systems (abs.): Geological Society of America Abstracts with Programs, v. 3, no. 2, p. 75. Artim, E.R., and Pinckney, C.J., 1973a, La Nacion Fault system, San Diego, California: Geological Society of America Bulletin, v. 84, p. 1075. Artim, E.R., and Pinckney, C.J., 1973b, La Nacion Fault system, San Diego, California, in Ross, A., and Dowlen, R.J. (eds.), Studies on the Geologic Hazards of the Greater San Diego Area, California: San Diego Associa tion of Geologists Guidebook, p. 77. Artim, E.R., 1978, Anatomy and History of Two test Trenches, La Nacion Fault, San Diego, California; talk presented to San Diego Association of Geologists, March 1978 meeting.

E-l Artim, E.R., and Elder, D.L., 1979, Late Quaternary deforma tion along the La Nacion Fault system, San Diego, Calif ornia (abs.): Geological Society of America Abstracts with Programs, v. 11, no. 7, p. 381. Bandy, O.L., 1967, Foraminiferal definition of the boundaries of the Pleistocene in Southern California, USA, in Sears, M. (ed.), Progress in Oceanography: New York, Pergamon Press, v. 4, p. 27-49. Barnes, L.G., 1973, Pliocene cetaceans of the San Diego Formation, San Diego, California, in Ross, A., and Dowlen, R.J. (eds.), Studies on the Geology and Geologic Hazards of the Greater San Diego Area, California: San Diego Association of Geologists Field Trip Guidebook, p. 37-42. Berggreen, R.G., and Streiff, D., 1979, Recency of faulting on the Mount Soledad branch of the Rose Canyon Fault zone in northwestern metropolitan San Diego, California (abs.): Geological Society of America Abstracts with Programs, v. 11, no. 7, p. 387. Bonilla, M.G., 1970, Surface faulting and related effects, in Wiegel, R.L., (ed.), Earthquake Engineering: Prentice- Hall, Inc., p. 47. Bowersox, J.R., 1974, Nearshore Environments of the Late Pleistocene Nestor Terrace, Point Loma, California: M.S. thesis, San Diego State University, San Diego, California, 69 p. Cluff, L., 1979, Geologic considerations for seismic micro- zonation: Woodward-Clyde Consultants Geotechnical Envi ronmental Bulletin, v. XII, no. 1, p. 4-13. Dorn, p., 1980, Geophysical Investigations in North Park, San Diego, California: Unpublished Senior report, San Diego State University, Department of Geological Sciences, San Diego, California. Dowlen, R., Hart, M., and Elliott, W., 1975, New evidence concerning age of movement of the La Nacion Fault, southwestern San Diego County, California (abs.): 1975, Association of Engineering Geologists, Annual Meeting, p. 20. Downs, T., and White, J.A., 1968, A vertebrate faunal succes sion in superposed sediments from Late Pleistocene to Middle Pleistocene in California: 23rd International Geological Congress Proceedings, Prague, Czechoslovakia, v. 10, p. 41-47.

E-2 Elliott, W.J., 1970, Gravity survey and regional geology of the San Diego embayment, southwest San Diego County, California: American Association of Petroleum Geolo gists Pacific Section Fall Guidebook, p. 10-22. Elliott, W.J., 1974, Seismicity of the San Diego region, in Recent geological and hydrological studies, eastern San Diego County and adjacent areas: San Diego Association of Geologists Field Trip Guidebook, p. 61. Elliott, W.J., and Hart, M.W., 1977, New evidence concerning age of movement of the La Nacion Fault, southwestern San Diego County, California, in Farrand, G.T., (ed.), Geology of southwestern San Diego County, California and northwestern Baja California: San Diego Association of Geologists, p. 53. Emery, K.O., 1954, General geology of the offshore area, southern California: California Division of Mines and Geology Bulletin 170, p. 107-111. Emery, K.O., 1960, The Sea Off Southern California, a Modern Habitat of Petroleum: John Wiley and Sons, New York, 266 p. Foster, J.H., 1973, Faulting near San Ysidro, southern San Diego County, California; in Ross, A., and Dowlen, R.J. (eds.), Studies on the geology and geologic hazards of the greater San Diego area, California: San Diego Association of Geologists Guidebook, p. 83. Gastil, R.G., Phillips, R.P., and Allison, E.G., 1973, Recon naissance geologic map of the state of Baja California, Mexico: Geological Society of America Memoir 140, 3 plates, scale 1:250,000. Gastil, R.G., Phillips, R.P., and Allison, E. C., 1975, Re connaissance geology of the state of Baja California, Mexico: Geological Society of America Memoir 140, 170 p. Gastil, R.G., Kies, R. , and Melius, D.J., 1979, Active and potentially active faults, San Diego County and north- westernmost Baja California: in Abbott, P.L., and Elliott, W.J. (eds.), Earthquakes and other perils: San Diego region, San Diego Association of Geologists, p. 47-60. Gastil, G., and Higley, R., 1979, Guide to San Diego Area Stratigraphy: San Diego State University, Department of Geological Sciences, San Diego, California.

E-3 Goldstein, G.F., 1956, Geology of the Sweitzer Formation at San Diego, California: M.A. thesis, University of Cal ifornia, Los Angeles, California, 86 p. Grant, U.S., and Gale, H.R., 1931, Catalogue of the marine Pliocene, and Pleistocene mollusca of California and ad jacent regions: San Diego Society of Natural History Memoir 1, p. 1036 Green, H.G., Bailey, K.A., Clarke, S.H., Ziony, J.I., and Kennedy, M.P., 1979, Implications of fault patterns of the inner California continental borderland between San Pedro and San Diego: in Abbott, P.L., and Elliott, W.J. (eds.), Earthquakes and Other Perils, San Diego Region, San Diego Association of Geologists, p. 21-29. Gunther, F., 1964, Foraminifera of the San Diego Formation, Mount Soledad and Pacific Beach: Unpublished senior report, San Diego State University, Department of Geo logical Sciences, San Diego, California, v. 16, p~ 187-246. Hanna, M.A., 1926, Geology of the La Jolla Quadrangle, Calif ornia: California University Publications in Geological Sciences, v. 16, p. 187-246. Harrington, J.M., 1980, A gravity survey of metropolitan San Diego, California: Unpublished Senior report, San Diego State University, Department of Geological Sciences, San Diego, California, 30 p. Hart, M., 1974, Radiocarbon ages of alluvium overlying La Nacion Fault, San Diego, California: Geological Society of American Bulletin, v. 85, p. 1329-1332. Hertlein, L.G., 1929, A new pecten from the San Diego Plio cene: Proceedings California Academy of Sciences, San Francisco, California, 4th Series, v. 18, p. 215 Hertlein, L.G., and Grant, U.S., 1939, Geology and oil poss ibilities of southwestern San Diego County: California Journal of Mines and Geology, v. 35, p. 57-78. Hertlein, L.G., and Grant, U.S., 1944, The geology and pale ontology of the marine Pliocene of San Diego, California: San Diego Society of Natural History Memoir, Part 1, v. 2, p. 72. Hertlein, L.G., and Grant, U.S., 1954, Geology of the Ocean- side-San Diego coastal area, Southern California: Calif ornia Division of Mines and Geology, Bulletin 170, p. 53-63.

E-4 Hileman, J.A., Seismicity of the San Diego region, in Ab bott, P.L., and Elliott, W.J. (eds.), Earthquakes and Other Perils, San Diego Region: San Diego Association of Geologists, p. 11-21. Hileman, J.A., Alien, C.R., and Nordquist, J.M., 1973, Seis micity of the Southern California region, January 1, 1932 to December 31, 1972, Seismological Laboratory, California Institute of Technology, Pasadena, 486 p. Howell, D.G., Stuart, C.J., Pratt, J.P., and Hill, D.J., 1974, Possible strike-slip faulting in the Southern California borderland: Geology, v. 2, no. 2, p. 93-98. Ingle, J.C., 1967, Foraminiferal biofacies variation and the Miocene-Pliocene boundary in Southern California: Bull etin American Paleontology, v. 52, no. 236, p. 217-394. Jennings, C.W., 1975, Fault map of California with locations of volcanoes, thermal springs, and thermal wells:_ California Division of Mines and Geology Data Map No. 1, scale 1:750,000. Jennings, C.W., 1977, Geologic map of California: California Geologic Data Map Series, California Division of Mines and Geology, scale 1:750,000. Kennedy, G.L., 1973, A marine invertebrate faunal from the Lindavista Formation, San Diego, California: San Diego Society of Natural History Transactions, v. 17, no. 10, p. 119. Kennedy, M.P., and Moore, G.W., 1971, Stratigraphy and struc ture of the area between Oceanside and San Diego, Calif ornia, geologic road log, field trip no. 8: in Field Trip Guidebook for Cordilleran Section, Geological Society of America, p. 149-166. Kennedy, M.P., 1975, Geology of the San Diego Metropolitan Area: California Division of Mines and Geology Bulletin 200, Part A, p. 1-45. Kennedy, M.P., 1975, Geology of the San Diego Metropolitan Area: California Division of Mines and Geology Bulletin 200, Part B, p. 45-56. Kennedy, M.P., Tan, S.S., Chapman, R.H., and Chase, C.W., 1975, Character and recency of faulting, San Diego Metropolitan Area, California: California Division of Mines and Geology Special Report 123, 33 p. Kennedy, M.P. and Tan, S.S., 1977, Geology of the National City, Imperial Beach, and Otay Mesa quadrangle, southern San Diego, metropolitan area, California: California Division of Mines and Geology Map Sheet 29, 1:24,000. E-5 Kennedy, M.P., and Welday, E.E., 1977, Character and recency of faulting offshore from urban San Diego, in Studies on surface faulting and liquefaction as potential earth quake hazards in urban San Diego, California: California Division of Mines and Geology Final Technical Report, p. 1-15. Kennedy, M.P., Bailey, K.A., Greene, H.G., and Clarke, S.H., 1978, Recency and character of faulting offshore from metropolitan San Diego, California: California Division of Mines and Geology Open File Report, no. 80-6, p. 27-28. Kennedy, M.P., and Welday, E.E., 1980, Recency and character of faulting offshore metropolitan San Diego, California: California Division of Mines and Geology Map Sheet 40, 1:50,000. Kern, J.P., 1971, Paleoenvironmental analysis of a Late Pleistocene estuary in Southern California: Journal of Paleontology, v. 45, no. 5, p. 810. Kern, J.P., 1973a, Late Quaternary deformation of the Nestor terrace on the east side of Point Loma, San Diego, Cal ifornia, in Ross, A., and Dowlen, R.J. (eds.), Studies on the geology and geologic hazards of the greater San Diego area, California: San Diego Association of Geo logists and the Association of Engineering Geologists Guidebook, p. 43. Kern, J.P., 1973b, Origin and history of two upper Pleis tocene marine terraces at San Diego, California: Geo logical Society of America Bulletin, v. 88, p. 1553. Kern, J.P., Stump, T.E., and Dowlen, R.J., 1971, An upper Pleistocene marine fauna from Mission Bay, San Diego, California: San Diego Society of Natural History Trans actions, v. 16, no. 15, p. 329. Ku, T., and Kern, J.P., 1974, Uranium-series age of the upper Pleistocene Nestor terrace, San Diego, California: Geo logical Society of America Bulletin, v. 85, p. 1713. Krause, D.C., 1965, Tectonics, bathymetry, and geomagnetism of the southern continental borderland west of Baja California, Mexico: Geological Society of America Bulletin, v. 76, p. 617-650. Legg, M.R., and Kennedy, M.P., 1979, Faulting offshore San Diego and northern Baja California: in Abbott, P.L., and Elliott, W.J. (eds.). Earthquakes and other perils, San Diego region: San Diego Association of Geologists, p. 29-46.

E-6 Leighton and Associates, 1978, Preliminary review of fault locations and activity, proposed marina redevelopment project: Unpublished report submitted to City of San Diego, California, by Leighton and Associates, San Diego, California. Liem, T.J., 1977, Late Pleistocene maximum age of faulting, southeast Mission Bay area, San Diego, California, in Farrand, G.T. (ed.), Geology of southwestern San Diego County, California and northwestern Baja California: San Diego Association of Geologists Guidebook, p. 61. Lough, C., 1973, Faults and epicenters, County of San Diego: San Diego County Planning Department map. Mandel, D.J., Jr., 1973, Latest Pliocene foraminifera in the upper part of the San Diego Formation, California, in Ross, A., and Dowlen, R.J. (eds), Studies on the Geology and geologic hazards of the greater San Diego area, Cal ifornia: San Diego Association of Geologists and the Association of Engineering Geologists Guidebook, p. 33. Mandel, D.J., 1974, Neogene stratigraphy and micropaleontol- ogy of the southern San Diego Area, California: M.S. thesis, San Diego State University, San Diego, Califor nia. Marshall, M., 1979, Geophysical survey of the La Nacion Fault zone, San Diego, California, in Abbott, P.L., and Elli- ott, W.J. (eds.). Earthquakes and other perils, San Diego region: San Diego Association of Geologists, p. 73-83. Marshall, M., 1980, Unpublished geophysical data, Department of Geology, San Diego State University, San Diego, California. Masters, P.M., and Bada, J.L., 1977, Racemization of isoleucine fossil mollusks from Indian middens and interglacial terraces in Southern California: Earth and Planetary Sciences Letters, v. 37. p. 173 McEuen, R.B., and Pinckney, C.J., 1972, Seismic risk in San Diego: San Diego Society of Natural History Transac tions, v. 17, p. 33. Merifield, P.M., and Lamar, D.L., 1975, Faulting in basement terrain, San Diego County, California: in Ross, A., and Dowlen, R.J. (eds.), Studies of the geology of Camp Pendleton and western San Diego County, California: San Diego Association of Geologists, p. 51-56.

E-7 Milow, E.D., and Ennis, D.B., 1961, Guide to geologic field trip of southwestern San Diego County, in Thomas, B.E. (ed.), Guidebook for Field trips: Geological Society of America 57th Annual Meeting, Cordilleran Section, p. 23. Minch, J.A., 1967, Stratigraphy and structure of the Tijuana- Rosarito Beach area, northwestern Baja California, Mexico: Geological Society of America Bulletin, v. 78, p. 1155. Moore, D.G., 1957, Acoustic soundings of Quaternary marine sediments off Point Loma, California: U.S. Navy Elec tronics Laboratory Report 815, San Diego, California, 17 p. Moore, D.G., 1969, Reflection profiling studies of the Calif ornia continental borderland - structure and Quaternary turbidite basins (abs.): Geological Society of America Special Paper 107, p. 142. Moore, E.J., 1968, Fossil mollusks of San Diego County: San Diego Society of Natural History Occasional Paper 15, 76 P- Moore, G.W., 1972, Offshore extension of the Rose Canyon Fault, San Diego, California: U.S. Geological Survey Professional Paper 800-C, p. 113. Moore, G.W., and Kennedy, M.P., 1970, Coastal geology of the California border area, in Pacific slope geology of northern Baja California and adjacent Alta California: American Association of Petroleum Geologists (Pacific Section) Fall Field Trip Guidebook, p. 4. Moore, G.W., and Kennedy, M.P., 1975, Quaternary faults at San Diego Bay, California U.S. Geological Survey Journal Research, v. 3, no. 5, p. 589-595. Orme, A.R., 1973, Major structural lineaments of northernmost Baja California and neighboring parts of San Diego and Imperial Counties, California: Unpublished report submitted to Fugro, Inc., by A.R. Orme, 9 p. Orme, A.R., 1974, Quaternary marine terraces between Ensenada and El Rosario, Baja California, Mexico, in Gastil, G., and Lillegraven, J. (eds.), The geology of peninsular California: (Pacific Sections) AAPG-SEMP-SEG, Field Trip Guidebook, p. 67-79. Ortlieb, L., 1979, Quaternary marine terraces in southwestern Vizcaino Peninsula, Baja California, Mexico, in Abbott, P.L., and Gastil, G., (eds.), Geological Society of American Annual Meeting, San Diego, California, p. 89-93.

E-8 Peterson, G.L., 1970a, Quaternary deformation of the San Diego area, southwestern California, in Pacific slope geology of northern Baja California and adjacent Alta California: American Association of Petroleum Geolo gists (Pacific Section) Fall Field Trip Guidebook, p. 120. Peterson, G.L., 1970b, Pleistocene deformation of the Linda- vista terrace near San Diego, California (abs.): Geolo gical Society of America Abstracts with Programs, v. 2, no. 2, p. 131. Rowland, R.W., 1972, Paleontology and paleoecology of the San Diego Formation in northwestern Baja California: San Diego Society of Natural History Transactions, v. 17, no. 3, p. 25-32. San Filipo, J., 1978, A magnetic survey of the Rose Canyon Fault zone: San Diego State University, Department of Geological Sciences, San Diego, California, 32 p. Schatzinger, E.R., 1972, Paleoecology of the upper portion of the San Diego Formation: Unpublished Senior report, California State State University, San Diego, Califor nia, 85 p. Schmalfuss, B.R., 1979, Late Quaternary slip on the Rose Canyon Fault: Unpublished Senior research paper, San Diego State University, Department of Geological Sci ences, San Diego, California, 19 p. Shackleton, N.J., and Opdyke, N.D., 1973, Oxygen isotope and paleomagnetic stratigraphy of equatorial Pacific Core J-28^238, Oxygen isotope temperature and ice volumes on a 10 year and 10 year scale: Quaternary Research, v. 3, p. 39. Simons, R.S., 1977a, Seismicity of San Diego 1934-1974: Seismological Society of America Bulletin, v. 67, no. 3, p. 809. Simons, R.S., 1977b, Earthquake prediction, prevention, and San Diego, in Abbott, P.L., and Victoria, J.K., (eds.), Geologic hazards in San Diego: San Diego Society of Natural History, p. 13. Simons, R.S., 1979, Instrumental seismicity of the San Diego area, 1934-1974, in Abbott, P.L., and Elliott, W.J., (eds.), Earthquakes and other perils, San Diego region: San Diego Association of Geologists, p. 101. Thatcher, W., Hileman, J.A., and Hanks, T.C., 1975, Seismic slip distribution along the San Jacinto Fault zone, Southern California, and its implications: Geological Society of America Bulletin, v. 86, p. 1140-1146. E-9 Threat, R.L., 1973, Birth and death of a fault in Mission Valley, San Diego, California, in Ross, A., and Dowlen, R.J. (eds.), Studies on the Geology and Geologic Hazards of the Greater San Diego Area, California: San Diego Association of Geologists and the Association of Engineering Geologists Guidebook, p. 105. Threet, R.L., 1977, Texas Street Fault, San Diego, Califor nia, in Farrand, G.T. (ed.), Geology of southwestern San Diego County, California and northwestern Baja Califor nia: San Diego Association of Geologists, p. 43. Threet, R.L. 1979, Rose Canyon Fault: An alternative inter pretation, in Abbott, P.L., and Elliott, W.J., (eds.), Earthquakes and other perils, San Diego Region: San Diego Association of Geologists, p. 61-71. Valentine, J.W., and Rowland, R.W., 1970, Major features of the marine Pliocene and Pleistocene fossil record of northwestern Baja California, Mexico, in Pacific slope geology of northern Baja California and adjacent Alta California: (Pacific Sections) AAPG-SEMP-SEG Field Trip Guidebook, p. 118-119. Vedder, J.G., Beyer, L.A., Junger, A., Moore, G.W., Roberts, A.E., Taylor, J.C., and Wagner, H.C., 1974, Preliminary report on the geology of the continental borderland of Southern California: Report to Accompany U.S. Geological Survey Map MF-624. Wicander, E.R., 1970, Planktonic foraminifera of the San Diego Formation, in Pacific slope geology of northern Baja California and adjacent Alta California: (Pacific Sections) AAPG-SEMP-SEG Field Trip Guidebook, p. 105. Woodring, W., and Bramlet, P., 1950, Geology and paleontology Santa Maria district, California: U.S. Geological Survey Professional Paper 222, p. 104-107. Wiegand, J.W., 1970, Evidence of a San Diego-Tijuana Fault: Association of Engineering Geologists Bulletin, v.7, no. 2, p. 107. Ziony, J.I., 1973, Recency of faulting in the greater San Diego area, California, in Ross, A., and Dowlen, R.J. (eds.), Studies on the geology and geologic hazards of the greater San Diego area, California: San Diego Association of Geologists Guidebook, p. 68. Ziony, J.I., and Buchanan, J.M., 1972, Preliminary report on recency of faulting in the greater San Diego area, California: U.S. Geological Survey, Open File Report, 16 p.

E-10 Ziony, J.I., Wentworth, C.M., Buchanan-Banks, J.M., and Wagner, H.C., 1974, Preliminary map showing recency of faulting in coastal southern California: U.S. Geolog ical Survey Map MF-585, 3 plates, 8 p, 1:25,000.

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