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HomeMy WebLinkAboutCT 00-13; Tabata; Tentative Map (CT) (3)M-D6-2002 02:46PM FROM- ^ T-221 P.002/006 F-126 PALEONTOLOGICAL RESOURCE ASSESSMENT TABATA PROPERTY PROJECT SITE CITY OF CARLSBAD for THE BREHM COMPANIES 1935 Camino Vida Roble, Suite 200 Carlsbad, California 92008 by Department of Paieontological Services San Diego Natural History Museum P.O. Box 121390 SanDiego, CA 92112 Thomas A. Demure, Ph.D. Director RECEIVED 19 March 2002 MAR 2 1 2002 THt bhtnivi UOMPANItb 04-06-2002 02:46PM FROM- T-221 P.003/006 F-126 PALEONTOLOGICAL RESOURCE ASSESSMENT TABATA PROPERTY PROJECT SITE CARLSBAD, CALIFORNIA INTRODUCTION This report provides a suminary of findings conceming the paieontological resource potential ofthe Tabata Property project site, Carlsbad, California (Figurc 1), The project site is located in the former agricultural lands south of Poinsettia Lane, east and north of Aviara Parkway and west of Ei Camino Real Black Rail Road forms thc westem border ofthe site, Corte Orchidca thc northem border, and Cabela Place the eastem border. As defined here, paieontological rcsources (i.e., fossils) are the remains and/or traces of prehistoric plant and animal life exclusive of man. Fossil remains such as bones, teeth, shells, and leaves are found in the geologic deposits (rock formations) within which they were originally buried. For the purposes of this report paieontological resources can be thought of as including not only the actual fossil remains, but also thc collecting localities and the geologic formations containing those localities. It is important to point out that many fossil sites presently on record in San Dicgo County have been discovered only during residential development activities, during highway and freeway constmction projects, or during pipeline and other utility constraction projects, This close correlation between fossil sites and constmction is related to the fact that surface weadiering quickly destroys most fossil materials and it is not until fresh unweathered exposures are created by gi-ading that well-preserved fossils can often be recovered. In addition, because of the amount of grading proposed for some sites, the chances are increased that grading will unearth rich fossil horizons. METHODS Because of the direct relationship between fossils and tlie geologic formations within which tliey are entombed, knowing the geology of a particular area and die fossil productivity of particular rock fonnations, one can reasonably predict where fossils will (or will nol) be encountered. Paieontological resource assessment of the project site is based upon a review of existing published geological literature (Eisenberg. 1985), a review of the site-specific geotechnical report by Geocon (2001), a review of museum paieontological records (SDNHM, San Diego Natural History Museum), and a walkover ofthe project site to field check the results ofthe literature and record reviews. RESULTS The project site lies on the crest of an ancient "beach ridge" that forms thc highest ground on the relatively flat coastal mesa surface that characterizes this area ofCarlsbad between Batiquitos Lagoon on tlie south and Canyon de las Encinas on the north. . D4-06-2002 02:46PM FROM-T-221 P.004/006 F-126 'as.. ••• •-j'S.-'^ -G- ' U .A - » r. .1.'. T.:ir-- •" IJ- .-. • • •, »•',. :';:!;; tr.;ir ..j^^j. SITE TNT/MN fl3' 4^ . t^llLE 1000 FEET 500 tn JOOOro Printed ftom TOPO! ©2000 TOdflower Prodoctions (www.topo.com) Figure 1. Index map showing location ofthe Tabata Property project site. Base map USGS 7.5 minute Encinitas, CA. 04-06-2002 02:47PM FROM- T-221 P.005/006 F-126 Elevations range from about 350 feet on the eastem and westem borders ofthe site to 383 feet along the southem border. Existing residential development exists to the north and cast ofthe site. An unlandscaped roadcut along Cabela Place provides an excellent exposure of the subsurface geology of the site. General Geology- As summarized on the Encinitas, CA, 7.5' USGS quadrangle geologic maps of Eisenberg (1985) and Tan and Kennedy (1996) the project site is underiain by early Pleistocene-aged (400,000-700,000 years old) sedimentary rocks of the Lindavista Formation. The site specific geotechnical report of Geocon (2001) records sedimentary rocks ofthe Lindavista Fomiation as occun-ing in the subsiwface, at least to a depth of six feet. A diin veneer of modem alluvium was mapped in the northwestem comer of the site. Lindavista Formatioji Introduction- The Lindavista Formation on tlie project site consists of at least 20 feet of red-brown, fine- to coarse-grained, massive sandstones and pebble conglomerates as exposed in the existing eastem roadcut along Cabala Place. The total thickness ofthis rock unit on the project site is probably close to 60 feet based on SDNHM documents and the published map of Eisenberg (1985) that place the base of tlie Lindavista Formation in this area at approximately elevation 320 feet. The Lindavista Formation was originally named for a sequence of Pleistocene strata exposed in metropolitan San Diego. This rock imit has subsequently been mapped into northem San Diego County where it includes both fine and coarse-grained sedimentary rocks. The Lindavista Fomiation is hypothesized to have formed in nearshore marine, beach, and coastal sand dune depositional enviromnents. Paleontology- Sparse fossil reraains have been recovered from this rock unit in the Carlsbad area. Two collecting sites are documented in the locality records ofthe SDNHM and occur one-half mile northeast of die Tabata Property site. Fossils from these rccorded localities consist of poorly-preserved molds and casts of marine molluscs and echinoderms. Thc fossils were discovered at the extreme base of the Lindavista Formation where it directly overlies Eocene-age sandstones of the Santiago Fomiation. In the metropolitan San Diego area Ihe Lindavista Forraation has produced better preserved fossils of marine molluscs, cmstaceans, and echinodemis, as well as sparse skeletal remains of marine vertebrates (sharks, rays, and cetaceans) (Demere and Walsh, 1993). Distribution- Thc Lindavista Formation imderiies the entire projeci area. Resource Sensitivity- The Lindavista Formation on the project site is assigned a low paieontological sensitivity based upon the diick nature ofthis rock unit on the Tabata Property site and the fact that fossils fi-om this rock unit almost always occur at its very base. » 54-06-2002 02:47PM FROM- T-221 P.006/006 F-126 IMPACT ANALYSIS Direct impacts to paieontological resources occur when earthwork activities, such as mass grading, cut into the geologic deposits (formations) withm which fossils are buried. These direct impacts are in the form of physical destmction of fossil remains. Tentative grading plans for the Tabata Property project site indicaie lhat on site cuts will bc confined to the upper portions ofthe Lindavista Fonnation and will not reach the typically fossiliferous base of the fomiation, which is projected to occur at about elevation 320 feet in this area ofCarlsbad, SIGNIFICANCE OF IMPACTS Fossils are the remains of prehistoric animal and plant life and are considered to be nonrenewable. Direct impacts to high and moderate sensitivity fomiations are significant and, under CEQA guidelines, require mitigation. The impact analysis presented above indicates that grading will not impact thc fossiliferous portions of the Lindavista Formation. MITIGATION MEASURES Because development of die Tabata Progeny project site will not produce any impacts to significant paieontological resources, there is no need for implementation ofa resource mitigation program. Thomas A, Demere, Ph.D, Department of Paieontological Services