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HomeMy WebLinkAboutCDP 13-30; De Anda Residence; Coastal Development Permit (CDP) (4)TECHNICAL REPORT PALEONTOLOGICAL RESOURCE ASSESSMENT DE ANDA RESIDENCE SAN DIEGO COUNTY, CALIFORNIA Prepared for: ASM AFFILIATES 2034 Corte Del Nogal Carlsbad, Califomia 92011 Prepared by: DEPARTMENT OF PALEOSERVICES SAN DIEGO NATURAL HISTORY MUSEUM P.O. Box 121390 San Diego, CA 92112 Thomas A. Demere, Ph.D., Director 16 July 2013 TECHNICAL REPORT PALEONTOLOGICAL RESOURCE ASSESSMENT DE ANDA RESIDENCE CITY OF CARLSBAD SAN DIEGO COUNTY, CALIFORNIA INTRODUCTION This technical report provides an assessment of issues related to paleontological resources at the De Anda Residence project site, located in the 2400 block of Jefferson Street (APN 155-140-41), City of Carlsbad, San Diego County, Califomia. The purpose of this report is to assist the project owner in planning and design efforts for the purposed project as related to paleontological resource issues. Specifically, this report is intended to summarize existing paleontological resource data in the project area and vicinity; assess potential impacts to paleontological resources from construction of the project; and identify mitigation measures to avoid or reduce project-related impacts wherever feasible. Additional discussion of report methodology is provided below. This report was prepared by Thomas A. Demere, Ph.D. of the Department of PaleoServices at the San Diego Natural History Museum (SDNHM), San Diego, Califomia. As defined here, paleontological resources (i.e., fossils) are the buried remains and/or traces of prehistoric organisms (i.e., animals, plants, and microbes). Body fossils such as bones, teeth, shells, leaves, and wood, as well as trace fossils such as tracks, trails, burrows, and footprints, are found in the geologic deposits (formations) within which they were originally buried. The primary factor determining whether an object is a fossil or not, isn't how the organic remain or trace is preserved (e.g., "petrified"), but rather how old is the organic remain or trace. Although typically it is assumed that fossils must be older than -10,000 years (i.e., the generally accepted end of the last glacial period of the Pleistocene Epoch), organic remains of early Holocene age can also be considered to represent fossils because they are part ofthe record of past life. Fossils are considered important scientific and educational resources because they serve as direct and indirect evidence of prehistoric life and are used to understand the history of life on Earth, the nature of past environments and climates, the membership and stmcture of ancient ecosystems, and the pattem and process of organic evolution and extinction. In addition, fossils are considered to be non-renewable resources because typically the organisms they represent no longer exist. Thus, once destroyed, a particular fossil can never be replaced. And finally, for the purposes of this report, paleontological resources can be thought of as including not only the actual fossil remains and traces, but also the fossil collecting localities and the geological formations containing those localities. METHODOLOGY A review was conducted of relevant published and unpublished geologic reports (Morton et al., 2004; Kennedy and Tan, 2005; GeoSoils, Inc., 2008), unpublished paleontological reports (Demere and Walsh, 1993), and museum paleontological locality data (SDNHM, Department of Paleontology). This approach was followed in recognition of the direct relationship between paleontological resources and the geologic formations within which they are entombed. Knowing the geology of a particular area and the fossil productivity of formations that occur in that area, it is possible to predict where fossils will, or will not, be encountered. 457000mE. NAD27 Zone lis 468000mE, 455000mE. TNt/MN 1/13' 457000mE 1/2 • NAD27 Zone lis 468000rnE. 1 MILE Figure 1. Index map showing location of the De Anda Residence project site on the south shore of Buena Vista Lagoon in Carlsbad, CA. Base map; San Luis Rey, CA 7.5' USGS topographic quadrangle. EXISTING CONDITIONS PHYSICAL GEOLOGICAL SETTING The project site is underlain by geologic deposits mapped as Pleistocene-age marine terrace deposits (=Bay Point Formation) and Eocene-age strata of the Santiago Formation (Morton et al., 2004; Kennedy and Tan, 2005; GeoSoils, hic, 2008). The depositional contact between the Pleistocene and Eocene age deposits occurs at approximately 16 feet below ground level (-46 feet above sea level). PALEONTOLOGICAL RESOURCE ASSESSMENT The following section provides a general overview of the types of geologic deposits located within or immediately adjacent to the project site. Pleistocene marine terrace deposits Introduction: The upper portion of the project site (above approximately elevation 46 feet) is underlain by red-brown, fine-grained, compact sandstone and silty sandstone with local stringers of well-rounded pebbles. As discussed by Eisenberg (1985) the Pleistocene marine terrace deposits in the Carlsbad and Oceanside area accumulated on a stair step series of elevated marine abrasion platforms (i.e., sea floors) which formed as a result of past periods of sea level fluctuation caused by episodes of global warming and cooling. The terrace deposits at the project site sit on an uplifted marine abrasion platform (i.e., an ancient sea floor), which based on elevation, appears to be correlative with the Nestor Terrace of Kem and Rockwell (1992). Paleontology: Fossils locally occur in the Pleistocene marine terrace deposits exposed in Carlsbad and Oceanside and consist primarily of well-preserved shells and tests of nearshore marine invertebrates (e.g., clams, oysters, scallops, snails, crabs, sea urchins, and sand dollars). Sparse remains of marine vertebrates (e.g., sharks, rays, and bony fish) have also been recovered from these deposits. A series of fossil discoveries were made in 1996 during constmction of the Pacific Coast Plaza shopping center on the north side (Oceanside) of Buena Vista Lagoon. Fossil recovered from these sites include diverse assemblages of Pleistocene marine invertebrates and vertebrates. Also in 1996, constmction improvements to the State Route 76 - Interstate 5 interchange (i.e., the northbound onramp) resulted in discovery of a partial mammoth tusk. Collectively, these fossils are significant and serve to document the location and faunal composition of Pleistocene marine and terrestrial paleoenvironments in northem San Diego County. The geologic age of these fossil-bearing deposits ranges from approximately 120,000 to 300,000 years old. Site Specific Assessment: There are no previous records of fossil localities occurring within the Pleistocene marine terrace deposits on the south side of Buena Vista Lagoon. However, there are recorded paleontological collecting sites in correlative deposits as exposed to the north of the project area. Because of these previous records, and following the paleontological guidelines developed by the County of San Diego, these marine terrace deposits are assigned a high paleontological resource sensitivity rating. Sespe Formation (mapped as Santiago Formation) Introduction: Published geologic reports for the Oceanside-Carlsbad area (Tan and Kennedy, 1996; Kennedy and Tan, 2005) refer all of the pre-Pleistocene and pre-San Onofre Breccia sedimentary rocks west of El Camino Real and to the Santiago Formation. Walsh (1991) and Mihlbachler and Demere (2009) discussed stratigraphic details and associated land mammal fossil assemblages from the Santiago Formation in northem San Diego County and noted that deposits in the eastem portions of Carlsbad and Oceanside range in age from 45 to 40 million years old. Recent fieldwork by SDNHM paleontologists in the westem portions of Carlsbad and Oceanside, however, have discovered fossils of Oligocene-age (-30-28 million years old) in the sedimentary rocks mapped as the Santiago Formation. This paleontological evidence when combined with recent geologic field evidence in this area clearly demonstrates that the published mapping is in error. Instead of being assigned to the Santiago Formation, the pre-Pleistocene and pre-San Onofre Breccia sedimentary rocks in this area more correctly should be assigned to the Sespe Formation as mapped farther north in southem Orange County (Morton et al., 2004; Kennedy and Tan, 2005). Paleontology: The Sespe Formation strata exposed in the westem portions of Carlsbad and Oceanside have produced well-preserved fossils of land mammals including isolated teeth and bones, as well as skulls and partial skeletons of insectivores, rabbits {Archaeolagus sp.) rodents {Heliscomys sp.), camivorans {Cynodictis sp.), oreodonts {Sespia californica), and chevrotains {Hypertragulus sp.). These fossils (especially Sespia californica) are characteristic of the early Arikareean North American Land Mammal Age (later part of the Oligocene Epoch) and suggest a correlation between the Sespe Formation in northwestem San Diego County and the Otay Formation in southwestem San Diego County. Studies by Demere (1988) and Walsh and Demere (1991) of the Otay Formation have noted the importance of these late Oligocene land mammal fossils to an understanding ofthe prehistory of the southem Califomia region. Site Specific Assessment: There are several recorded fossil collecting sites from the Sespe Formation located southwest of the project site in the sea cliffs of north Carlsbad. Another recorded fossil collecting site is known from a residential housing development built along the north side of the San Luis Rey River Valley in Oceanside. Because of these previous records, and following the paleontological guidelines developed by the County of San Diego, the Sespe Formation is assigned a high paleontological resource sensitivity rating. IMPACT ANALYSIS INTRODUCTION Direct impacts to paleontological resources occur when earthwork activities, such as mass grading operations, cut into the geological deposits (formations) within which fossils are buried. These direct impacts are in the form of physical destmction of fossil remains. Since fossils are the remains of prehistoric animal and plant life they are considered to be nonrenewable. Such impacts can be significant and, under CEQA guidelines, require mitigation. Impacts to paleontological resources are typically rated from high to zero depending upon the resource sensitivity of impacted formations. High significance Impacts to high sensitivity formations (Pleistocene marine terrace deposits and Sespe Formation). Moderate significance Impacts to moderate sensitivity formations (none in project area). Low significance Impacts to low sensitivity formations (none in project area). Zero significance Impacts to formations with no fossil potential (none in project area). SITE SPECIFIC IMPACTS Pleistocene marine terrace deposits It is assumed that constmction of the proposed residence will involve some excavation into previously undisturbed sedimentary rocks. This work has the potential to impact potentially fossil-bearing strata of the Pleistocene marine terrace deposits. These potential negative impacts to paleontological resources can be reduced to below the level of significance through implementation ofthe mitigation plan as outlined below. Sespe Formation Although more deeply buried on the project site, previously undistmrbed strata of the Sespe Formation may be impacted by deeper excavations, such as occur during constmction of swimming pools. Such excavations may impact potentially fossil-bearing strata of the Sespe Formation. These potential negative impacts to paleontological resources can be reduced to below the level of significance through implementation of the mitigation plan as outlined below. MITIGATION MEASURES 1. A qualified paleontologist should attend the pre-constmction meeting to consult with the grading and excavation contractors conceming excavation schedules, paleontological field techniques, and safety issues. (A qualified paleontologist is defined as an individual with a MS or Ph.D. in paleontology or geology that is familiar with paleontological procedures and techniques, who is knowledgeable in the geology and paleontology of San Diego County, and who has worked as a paleontological mitigation project supervisor in the county for at least one year.) 2. A paleontological monitor should be on-site on a full-time basis during the original cutting of previously undisturbed deposits of high paleontological resource potential to inspect exposures for contained fossils. Because of the destmctive nature of surface weathering processes, the only the deeper (i.e. > 5 feet deep) excavations into the Pleistocene marine terrace deposits should be monitored full-time. In contrast, any excavations extending below elevation 46 feet and impacting the Sespe Formation should be monitored fiill-time (A paleontological monitor is defined as an individual who has experience in the collection and salvage of fossil materials. The paleontological monitor should work under the direction of a qualified paleontologist.) 3. When fossils are discovered, the paleontologist (or paleontological monitor) should recover them. In most cases this fossil salvage can be completed in a short period of time. However, some fossil specimens (such as a complete large mammal skeleton) may require an extended salvage period. In these instances the paleontologist (or paleontological monitor) should be allowed to temporarily direct, divert, or halt grading to allow recovery of fossil remains in a timely manner. Because of the potential for the recovering of small fossil remains, such as isolated mammal teeth, it may be necessary to set up a screen-washing operation on the site. 4. Fossil remains collected during monitoring and salvage should be cleaned, repaired, sorted, and cataloged as part of the mitigation program. 5. Prepared fossils, along with copies of all pertinent field notes, photos, and maps, should be deposited (as a donation) in a scientific institution with permanent paleontological collections such as the San Diego Natural History Museum. Donation of the fossils should be accompanied by financial support for initial specimen storage. 6. A final summary report should be completed that outlines the results of the mitigation program. This report should include discussions of the methods used, stratigraphic section(s) exposed, fossils collected, and significance of recovered fossils. REFERENCES Demere, T.A. 1988. Early Arikareean (late Oligocene) vertebrate fossils and biostratigraphic correlations of the Otay Formation at EastLake, San Diego County, Califomia. In, M.V. Filewicz and R.L. Squires (eds.), Paleogene Stratigraphy, West Coast of North America. Society of Economic Paleontologists and Mineralogists, Pacific Section 58:35-43. 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. 1-60. Eisenberg, L.I. 1985. Pleistocene faults and marine terraces, northem San Diego County. In, P.L. Abbott (ed.). On the Maimer of Deposition of the Eocene Strata in Northem San Diego County. San Diego Association of Geologists, fieldtrip guidebook, pp. 87-91. GeoSoils, Inc. 2008. Updated preliminary geotechnical evaluation, APN 155-140-41, Carlsbad, San Diego County, Califomia. Unpublished report W.O. 5763-A-SC, submitted to Mr. Roberto. Becker, 118 p. Keimedy, M.P. and S.S. Tan. 2005. Geologic map of the Oceanside 30' x 60' quadrangle, Califomia: A digital database: Califomia Geological Survey, Preliminary Geologic Maps, scale 1:100000. Kem, J.P. and T.K. Rockwell. 1992. Chronology and deformation of Quatemary marine shorelines, San Diego County, Califomia: in Quatemary Coasts of the United States: Marine and Lacustrine Systems: Society of Economic Paleotologists and Mineralogists Special Publication No. 48, p. 377-382. Mihlbachler, M.C. and T.A. Demere. 2009. A New Species of Brontotheriidae (Perissodactyla, Mammalia) from the Santiago Formation (Duchesnean, Middle Eocene) of Southem Califomia. Proceedings of the San Diego Society of Natural History 41:1-36. Morton, D.M., Bovard, K.R., and R.M. Alvarez. 2004. Preliminary Digital Geologic Map of the Santa Ana 30' x 60' Quadrangle, Southern California: U.S. Geological Survey Open-File Report 99-172, http://pubs.usgs.gov/of/1999/of99-172/. Tan, S.S., and M.P. Kennedy. 1996. Geologic maps of the northwestem part of San Diego, Califomia: Califomia Division of Mines and Geology Open-File Report 96-02, 2 sheets (scale 1:24,000). Walsh, S.L. 1991. Eocene mammal faunas of San Diego County. La, 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. Walsh, S.L., and T.A. Demere. 1991. Age and stratigraphy of the Sweetwater and Otay formations, San Diego County, Califomia. In P. L. Abbott and J. A. May (eds.), Eocene Geologic History San Diego Region. Pacific Section SEPM Volume 68:131-148. Wilson, K.L. 1972. Eocene and related geology of a portion of the San Luis Rey and Encinitas quadrangles, San Diego County, Califomia. Unpublished M.A. thesis. University of Califomia, Riverside, 135 p.