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HomeMy WebLinkAboutGPA 05-06; AURA CIRCLE; PHASE 1 PALEONTOLOGICAL REPORT; 2005-05-12r SAN DIEGO NATURAL HISTORY MUSEUM BALBOA PARK-SAN DIEGO SOCIETY OF NATURAL HISTORY -ESTABLISHED 1874 ~ May 12, 2005 Mr. Jim Kamphuis, Project Manager MSK Development Group P.O. Box 819 Carlsbad, CA 92018 c, ,.,. RE: Phase 1 Paleontological Report for Aura Circle Property, City of Carlsbad, California Dear Mr. Kamphuis: This letter presents the results of a museum record search and site reconnaissance which was conducted for the Aura Circle Property in the City of Carlsbad, California. This property is located between Kelly Drive to the east, Avila Road to the west, Hillside Drive and Aura Circle to the south, and Lot 11 open space to the north, and is situated within the Laguna Riviera subdivision. The footprint of the proposed residential development is approximately 680 feet north to south, and 400 feet west to east. METHODS On Thursday, May 12, 2005, I conducted a field survey of the Aura Circle Property as required by the City of Carlsbad. This survey consisted of a pedestrian inspection of the study area for 1) surface fossils; 2) exposures of potentially fossiliferous rock; and 3) areas in which fossiliferous rocks or younger potentially fossiliferous surficial deposits could be exposed or otherwise impacted during construction. Prior to the field survey, literature and museum record searches were conducted in order to assess the paleontological sensitivity of the Aura Circle Property and the geologic units present within it. The purpose of the paleontological records review and site reconnaissance was to confirm that monitoring of construction excavations would be necessary. RESULTS According to published geologic mapping (Tan and Kennedy, 1996) and the results of the field survey, the Aura Circle Property is underlain by bedrock deposits of member "C" of the Santiago Formation (Wilson, 1972), which is late middle Eocene in age. According to the records of the San Diego Natural History Museum, the Natural History Museum of Los Angeles County, the University of California Riverside, and the University of California Museum of Paleontology in Berkeley, there are at least 20 previously recorded fossil localities in the Santiago Formation within a one mile radius of the Aura Circle Property in Carlsbad (Golz, 1976; Golz and Lillegraven, 1977; unpublished SDNHM, LACM, UCR, and UCMP paleontological data). Numerous other Santiago Formation localities are known from elsewhere in northern San Diego County. These localities have produced locally abundant, well preserved and scientifically significant fossil vertebrates and invertebrates representing a diversity oftaxa, including several holotypes (a holotype is a single specimen which is designated as the name-bearing type of a species or subspecies when it is first established). Post Office Bo:< 121390 * San Diego, California 92112-1390 * Telephone 619-232-3821 *FAX 6\9-232-0248 • www.sdnhm.org Within the Aura Circle property, rocks of the Santiago Formation are covered with a thin veneer of soil and weathered bedrock (approximately 1-2 feet thick). Most of the property is vegetated with coastal sage scrub, but three localized exposures of bedrock are present. One small exposure occurs near the entrance to the property off of Aura Circle; a second occurs on the steep slope along its western boundary. The largest exposure occurs on a steep embankment near the southern boundary of the property. Observed lithologies include weathered light grayish-white and tan resistant fine-to medium-grained arkosic sandstone, and less indurated white to light gray muddy sandstone and sandy mudstone. No surface fossils were observed in this approximately 10 feet high exposure, or elsewhere within the property. This is in part the result of the limited areal extent of outcrops and the severely weathered state of the exposed rock. DISCUSSION Within San Diego County, member "C" of the Santiago Formation is considered to have a high paleontological resource sensitivity based on the presence of locally diverse and well-preserved fossil assemblages of terrestrial vertebrates (Demere and Walsh, 1993). Member "C" has produced abundant vertebrate fossils from several districts including Carlsbad, Oceanside, and Camp Pendleton Marine Corps Base (Golz 1976; Golz and Lillegraven 1977; Walsh 1991). Fossils collected from this upper unit include well-preserved remains of turtles, snakes, lizards, crocodiles, birds, and mammals (e.g., opossums, insectivores, primates, rodents, brontotheres, tapirs, protoreodonts, and other early artiodactyls). Based on the project design plans, a significant amount of Santiago Formation rock will need to be removed in order to prepare the Aura Circle Property for construction of the 10 residences which are proposed. The hill which occupies the center of the property will need to be lowered approximately 60 feet. This removal of Santiago Formation bedrock has the potential to adversely impact scientifically significant paleontological resources, but also provides an opportunity to examine a relatively thick potentially fossiliferous section of Santiago Formation. The Department of PaleoServices at the San Diego Natural History is currently preparing a monitoring and mitigation plan in order to reduce potential impacts to below the level of significance. The preservation of these fossils and their storage in perpetuity at the San Diego Natural History Museum will ensure their availability to future generations of citizens, students, and professional scientists. Please do not hesitate to contact Tom Demere (619.255.0232, tdemere@sdnhm.org) or myself (619.255.0187.pmurphey@sdnhm.org) if you have any questions. Sincerely, Paul C. Murphey, Ph.D. Associate Director, Department of Paleo Services San Diego Natural History Museum REFERENCES Demere, T. A., and S. L. Walsh. 1993, Paleontological Resources, County of San Diego: Prepared for the Department of Public Works, County of San Diego, p. 1"-68. Golz, D.J., 1976, Eocene Artiodactyla of southern California: Natural History Museum of Los Angeles County, Science Bulletin 26:1-85. Golz, D.J., and J.A. Lillegraven, 1977, Summary of known occurrences of terrestrial vertebrates from Eocene strata of southern California: University of Wyoming, Contributions to Geology 15:43-65. Tan, S.S., and Kennedy, M.P ., 1996, Geologic maps of the northwestern part of San Diego County, California: California Division of Mines and Geology Open-File Report 96-02, 2 plates, scale 1 :24,000. Walsh, S.L., 1991, Eocene mammal faunas of San Diego County: In, P.L. Abbott and J.A. May (eds.), Eocene Geologic History San Diego Region. Society of Economic Mineralogists and Paleontologists, Pacific Section 68: 161-178.