i Pliocene Invertebrates From the Travertine Point Outcrop of the Imperial Formation, Imperial County, California Scientific Investigations Report 2008–5155 U.S. Department of the Interior U.S. Geological Survey This page left intentionally blank. Pliocene Invertebrates From the Travertine Point Outcrop of the Imperial Formation, Imperial County, California By Charles L. Powell II Scientific Investigations Report 2008–5155 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DIRK KEMPTHORNE, Secretary U.S. Geological Survey Mark D. Myers, Director U.S. Geological Survey, Reston, Virginia: 2008 This report and any updates to it are available online at: http://pubs.usgs.gov/sir/2008/5155/ For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod/ Telephone: 1-888-ASK-USGS For more information on the USGS — the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov/ Telephone: 1-888-ASK-USGS Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Powell, C.L., II, 2008, Pliocene Invertebrates from the Travertine Point Outcrop of the Imperial Formation, Imperial County, California: U.S. Geological Survey Scientific Investigations Report 2008-5155, 25 p. Produced in the Western Region, Menlo Park, California Manuscript approved for publication, August 27, 2008 Text edited by James W. Hendley II Layout by David R. Jones FRONT COVER—The Bivalvia Glycymeris (Glycymeris) gigantea (Reeve) from the Travertine Point outcrop of the Imperial Formation. iii Contents Abstract ..........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Geologic Setting .............................................................................................................................................1 Age and Correlation.......................................................................................................................................3 Paleoecology ..................................................................................................................................................3 Systematic Paleontology ..............................................................................................................................6 Acknowledgments .......................................................................................................................................18 References Cited..........................................................................................................................................18 Appendix—Locality Information Museum of Paleontology, University of California, Berkeley collections ..........................................25 U. S. Geological Survey, Menlo Park, California Cenozoic collections ..............................................25 Figures 1. Map of the Travertine Point study area ..................................................................................................2 2. Latitudinal distribution of selected mollusks recovered from the Travertine Point outcrop of the Imperial Formation ..........................................................................................................5 3. Selected fossils from the Travertine Point exposure of the Imperial Formation. ............................7 4. Selected fossils from the Travertine Point exposure of the Imperial Formation ...........................13 5. Selected fossils from the Travertine Point exposure of the Imperial Formation ...........................17 Tables 1. Fossils collections from the Travertine Point outcrop of the Imperial Formation ...........................4 2. Occurrence of specifically identified mollusks from the Travertine Point faunule.........................5 This page left intentionally blank. Pliocene Invertebrates From the Travertine Point Outcrop of the Imperial Formation, Imperial County, California By Charles L. Powell II Abstract at Cabazon (=Lions Canyon area of earlier reports), White- water (=Super Creek area of earlier reports), and Garnet Forty-four invertebrate taxa, including one coral, 40 Hill. Outcrops from the “southern” exposures are generally mollusks (30 bivalves and 10 gastropods), and three echinoids Pliocene (Johnson and others, 1983; Opdyke and others, are recognized from a thin marine interval of the Imperial 1977), but some recent work suggests that the “southern” Formation near Travertine Point, Imperial County, Califor- exposures are, in part, late Miocene (Winker, 1987). The nia. The Travertine Point outcrop lies about midway between “southern” exposures include outcrops at the Ocotillo Wells exposures of the Imperial Formation around Palm Springs, State Vehicle Recreation Area (=San Felipe Hills of earlier Riverside County, and exposures centered at Coyote Moun- reports), Supersitition Mountain, Fish Creek-Vallecitos tain in Imperial and San Diego Counties. Based on faunal Wash area, Coyote Mountain, Yuha Buttes, and northern comparisons, the Travertine Point outcrop corresponds to the Cucupa Mountains, east of Mexicali, Mexico (Ingle, 1974). Imperial and San Diego outcrops. One exception to this north-south division of the Imperial The Travertine Point fauna is inferred to have lived in Formation are exposure at Willis Palms, where the age of subtropical to tropical waters at littoral to inner sublittorial the fauna appears to be Pliocene (Powell, 1986). Outcrops at (<50 m) water depths. Coral and molluscan species from the Travertine Point lie about midway between the "northern" Travertine Point outcrop indicate a Pliocene age. Two extant and "southern" outcrops of the Imperial Formation, but its bivalve mollusks present have not previously been reported fauna correlates with the "southern" outcrops. as fossils Anadara reinharti and forms questionably referred Fossils from the Travertine Point area were first col- to Dosinia semiobliterata. lected in the 1930s by students from the University of Cali- fornia at Berkeley (UCMP localities A1705, A1706, A1707; see appendix for locality information). Two additional collections at or near Travertine Point are known. The first Introduction is a single specimen of the bivalve Pycnodonte? heermanni at the San Diego Museum of Natural History from a ques- The Imperial Formation consists of marine sediments tionable locality vaguely stating as “...area where Riverside/ deposited at the head and western margin of the proto- San Diego/Imperial counties meet” (SDSNH locality 1012), Gulf of California during the late Neogene (late Miocene which is herein assigned generally to the Travertine Point and Pliocene). Molluscan fossils have been reported from area. The second is small collection from “Garnet Wash the Imperial Formation for more than 150 years (Blake, 1.5 mi W of Travertine Point” at the California Academy of 1855) but are still largely unstudied. This paper describes Sciences (CAS locality 2718). This later site does not cor- an invertebrate assemblage composed mostly of mollusks respond to the Travertine Point directly, but to the area west from an Imperial Formation outcrop near Travertine Point, and northwest of Travertine Point in the Santa Rosa Moun- Imperial County, just west of the Salton Sea and very near tains, where fossils from the Imperial Formation have been the boundary between San Diego, Riverside, and Impe- recently rediscovered (King and others, 2002). rial Counties (fig. 1). The only published record of fossils from this area is that of Dibblee (1954) who, as part of his regional study of the Imperial Valley, mentions briefly fos- sils from the Imperial Formation at Travertine Point. Geologic Setting The Imperial Formation has been informally divided into “northern” and “southern” exposures that differ in The Imperial Formation at Travertine Point, referable to provenance of sediments, location in the proto-Gulf of the lower part of the Latrania Sand Member of Hanna (1926) California, age, and macrofauna (Powell, 1986, 1988). Most and Keen and Bentson (1944), consists of about 17 m of tan outcrops from the “northern” exposures are considered to yellow, fossiliferous, medium- to coarse-grained sandstone Miocene in age (Powell, 1986, 1988; McDougall and oth- with abundant calcareous cement. Grains are generally sub- ers, 1994; Rymer and others, 1994) and include outcrops rounded and the outcrop commonly contains well rounded, 2 Pliocene Invertebrates from the Travertine Point Outcrop of the Imperial Formation, Imperial County, California LOS ANGELES SAN BERNARDINO COUNTY 1 2 RIVERSIDE COUNTY RIVERSIDE BANNING 3 4 5 PALM SPRINGS INDIO ORANGE LONG BEACH COUNTY PACIFIC OCEAN SALTON SEA RIVERSIDE COUNTY 6 SAN DIEGO COUNTY ESCONDIDO 7 JULIAN BRAWLEY 9 CALIFORNIA 8 10 COUNTY IMPERIAL Map area N SAN DIEGO 11 12 50 mi MEXICO 100 km 2000 ft -100 500 m X 86 BM 100 SAN DIEGO CO. N Travertine Point Wash X BM 127 100 Wash IMPERIAL CO. IMPERIAL Garner SAN DIEGO CO. sea level 172 200 Palm 367 100 335 Travertine