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Geologic Map of the Oceanside 30' X 60' Quadrangle, California

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Geologic Map of the Oceanside 30' X 60' Quadrangle, California Geologic Map of the Oceanside 30’ x 60’ Quadrangle, California Compiled by Michael P. Kennedy1 and Siang S. Tan1 Digital Preparation by Kelly R. Bovard2, Rachel M. Alvarez2, Michael J. Watson2, and Carlos I. Gutierrez1 2007 Prepared in cooperation with: Copyright © 2007 by the California Department of Conservation California Geological Survey. All rights reserved. No part of this publication may be reproduced without written consent of the California Geological Survey. The Department of Conservation makes no warranties as to the suitability of this product for any given purpose. ARNOLD SCHWARZENEGGER, Governor MIKE CHRISMAN, Secretary BRIDGETT LUTHER, Director JOHN G. PARRISH, Ph.D., State Geologist STATE OF CALIFORNIA THE RESOURCES AGENCY DEPARTMENT OF CONSERVATION CALIFORNIA GEOLOGICAL SURVEY __________________________________ 1Department of Conservation, California Geological Survey 2U.S. Geological Survey, Department of Earth Sciences, University of California, Riverside CALIFORNIA GEOLOGICAL SURVEY JOHN G. PARRISH, Ph.D. STATE GEOLOGIST Copyright © 2007 by the California Department of Conservation. All rights reserved. No part of this publication may be reproduced without written consent of the California Geological Survey. The Department of Conservation makes no warranties as to the suitability of this product for any particular purpose. Introduction southwestern corner of the quadrangle In 1990 the U.S. Geological Survey, (source of the 1986, ML=5.3, Oceanside as part of the National Geologic Mapping earthquake) (Fig. 1). Seismic hazards are Program, initiated the Southern California numerous throughout the area. In addition, Areal Mapping Project (SCAMP) (http:// rapid uplift of relatively weak sedimentary scamp.wr.usgs.gov) in cooperation with the rocks has lead to an abundance of California Geological Survey (then Division landslides in the western and offshore parts of Mines and Geology) Regional Geologic of the quadrangle. A tsunami hazard zone Mapping Project (http://www.conservation. also exists along the coastal margin. ca.gov/cgs/rghm/rgm/index.htm). SCAMP’s The Peninsular Ranges of southern objectives were two-fold: to provide a basic California form a northwest-trending understanding of the geologic framework geomorphic province that occupies the and geologic history of southern California; southwestern corner of California and and to develop a uniform digital geologic extends southeastward to form the Baja map database that could be used in a California peninsula. Its physiography is Geographic Information System (GIS) and characterized principally by steep mountain be the foundation for geologic hazard highlands with elevations exceeding 3,500 investigations, natural resource evaluations, meters and dramatic intermontane basins, and other related earth science studies. valleys, and rivers. The highlands are These types of digital data can provide an flanked on the west by a relatively narrow, important component for performing GIS westward sloping coastal margin that analyses throughout southern California. includes the San Diego embayment. On This map was prepared by the the east the highlands are bounded from Department of Conservation, California the adjoining Colorado Desert and the Gulf Geological Survey and is a product of of California by precipitous fault scarps, SCAMP. This project was supported in part 2,000 to more than 3,000 meters high. by the U.S. Geological Survey STATEMAP The Peninsular Ranges province is award no. 01HQAG0092. comprised of rocks that range in age from Quaternary to Paleozoic. Most of the rocks Geologic Summary are Jurassic and Cretaceous igneous rocks The Oceanside 1:100,000-scale of the Peninsular Ranges batholith and the quadrangle lies within the Peninsular Triassic and Jurassic metasedimentary Ranges Geomorphic Province of southern sequence they intrude. Along the western California, between 33° and 33°30' N. margin of the province are large undivided latitude and 117° and 118° W. longitude, in bodies of Jurassic and Cretaceous pre- a rapidly urbanizing part of southern batholithic and synbatholithic volcanic, California (Fig. 1). The area is tectonically metavolcanic, and metasedimentary rocks. and seismically active and includes parts of In addition, thick sequences of Upper four major, northwest-striking, right-lateral, Cretaceous and Tertiary units composed of strike-slip, Pacific/North American Plate post-batholithic sedimentary and volcanic boundary fault zones. They include the rocks flank the older rocks on the west. Elsinore Fault Zone in the northeastern The youngest deposits are Quaternary corner of the quadrangle, the Newport- marine, lagoonal, and fluviatile sediments Inglewood Fault Zone in the center of the that discontinuously crop out over the entire quadrangle (source of the 1933, M=6.3, province. A dramatic series of marine, Long Beach earthquake), the Coronado wave-cut terraces and their overlying Bank Fault in the near offshore region and paralic sediments occur along the western the San Diego Trough Fault Zone in the coastal margin of the province. These 1 Figure 1. Index map showing the location of the Oceanside 30’ x 60’ quadrangle, major cities and faults, as well as the geomorphic provinces of southwestern California. Modified from Jennings and Saucedo, 2002. terraces, coupled with available 18O data, and others, 2003). In southern California, provide clear evidence of regional uplift numerous studies (summarized in detail by during the past million years (Plate 2). Morton and Miller, 2006), using geo- The composite Peninsular Ranges chemical and geophysical techniques, have batholith of southern California and Baja been conducted to determine rock ages, California was emplaced across the properties and structural relationships. lithospheric boundary between the North Most workers divide the batholith into two American and Pacific plates during the major longitudinal parts. The older western Jurassic and Cretaceous periods (Todd, part is of Early and mid-Cretaceous age 2 and composed of tonalite, gabbro and succession of marine and nonmarine lagoonal, granodiorite plutons. The younger eastern paralic and terrestrial sedimentary rocks. part is mid- to Late Cretaceous and Quaternary marine and nonmarine beach, bar, composed of less mafic granitic rocks with dune, fluviatile and alluvial fan deposits little or no gabbro. The eastern part also discontinuously cover the older sedimentary contains Jurassic metagranitic plutons that succession along the western margin of the are now considered part of the Peninsular subaerial part of the province. Holocene Ranges batholith (Shaw, and others, 2003). alluvium and colluvium, derived from fractured The Oceanside 1:100,000-scale quadrangle and deeply weathered bedrock associated lies almost entirely within the western part with K/T boundary subaerial extremes, mantle of the batholith. Jurassic metagranitic rocks much of the interior highlands and particularly in the Pala and Valley Center 7.5-minute the steep slopes adjacent to and southwest of quadrangles crop out near the boundary the Elsinore Fault Zone. between the eastern and western parts of the batholith. In the northwest part of the Compilation quadrangle, Jurassic and Triassic meta- The onshore part of the Geologic Map sedimentary rocks occur as northwest- of the Oceanside 30’ x 60’ Quadrangle, trending screens that have been intruded California was digitized at a scale of 1:24,000 and assimilated by Jurassic and while the offshore part has been enlarged from Cretaceous plutons. Most of these pre- the 1:250,000-scale Continental Margin Map batholithic rocks are quartzofeldspathic (Clarke and others, 1987). New geologic schist, pelitic schist, quartzite, injection mapping for the onshore area was completed gneiss and breccia. These rocks have in each of the eighteen 7.5-minute quad- been informally correlated with the Julian rangles. Geologic maps of the Oceanside, Schist (e.g. Irwin and Greene, 1970). San Luis Rey, San Marcos, Encinitas, and The undivided prebatholithic and Rancho Santa Fe quadrangles were published synbatholithic Jurassic and Cretaceous by the California Geological Survey (Division rocks include volcanic and metavolcanic of Mines and Geology) as Open-File Report rocks (Santiago Peak Volcanics) of Larsen 96-02 (Tan and Kennedy, 1996). The (1948), metasedimentary rocks (Bedford remaining thirteen 7.5-minute quadrangles Canyon Formation) of Larsen (1948) and were completed during the period July 1998 to volcanic, metavolcanic, sedimentary and June 2001 under STATEMAP funding awards metasedimentary rocks (Black Mountain no. 98HQAG2049, 99HQAG0134, and Volcanics) of Hanna (1926). Part of what 00HQAG0120. The geologic maps produced earlier workers mapped as Santiago Peak from these awards along with the previously Vocanics (e.g. Larsen, 1948) is a Creta- published maps were digitized with minor ceous subaerial island-arc volcanic modifications to produce this seamless digital sequence consisting of basaltic andesite, map. andesite, dacite, rhyolite, volcaniclastic The original digital work for the breccia, welded tuff and epiclastic rocks individual quadrangles, as well as the merged (Herzig, 1991). They are the extrusive and database file, was completed using ArcInfo® shallow intrusive parts of the batholith 8.3, a commercial GIS software package by (Herzig and Kimbrough, 1991; Anderson, Environmental Systems Research Institute 1991). (ESRI). For publication purposes the merged The Upper Cretaceous and Tertiary coverage was converted
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