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Home My WebLink AboutCT 00-13; TABATA; PALEONTOLOGICAL RESOURCE ASSESSMENT; 2002-03-12· 04-06-2002 02:46PU FROU-T-221 P.002/006 F-126 PALEONTOLOGICAL RESOURCE ASSESSMENT TABATA PROPERTY PROJECT SITE CITY OF CARLSBAD for THE BREHM. COMPANIES I 935 Camino Vida Roble, Suite 200 Carlsbad, California 92008 by Department of Paleontological Services San Diego Natural History Museum P .o. Box 121390 San Diego, CA 92112 Thomas A. Demere, Ph.D. Director 19 March 2002 RECEIVED MAR 21 2002 THt: l:St1tMM L:OMt'ANlf:~ ·-04-06-2002 02 :46PU FROM- C T-221 P.003/006 F-126 PALEONTOLOGICAL RESOURCE ASSESSMENT TABATA PROPERTY PROJECT SITE CARLSBAD, CALIFORNIA INTRODUCTION This report provides a summary of findings concerning the paleontological resource potential of the Tabata Property project site, Carlsbad, California (Figure l ). The project site is located in the fonner agricultural lands south of Poinsettia Lane, east and north of A viara Parkway and west of El Camino Real. Black Rail Road forms the western border of the site, Corte Orchidea the northern border, and Cabe la Place the eastern border. As defined here, pa)eontological resources (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 paleontological resources can be thought of as including not only the actual fossil remains, but also the collecting localities and the geologic formations containing those localities. It is important to point out that many fossil sites presently on record in San Diogo County have been discovered only during residential development activities, during highway and freeway construction projects, or during pipeline and other utility construction projects. This close correlation between fossil sites and construction is related to the fact that surface weathering quickly destroys most fossil materials and it is not until fresh unweathered exposures are created by grading 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 the geologic formations within which they are entombed, knowing the geology of a particular area and the fossil productivity of particular rock fonnations, one can reasonably predict where fossils will (or will not) be encountered. Paleontological resource asscssntent of the project site is based upon a. review of existing published geological literature (Eisenberg, l 985), a review of the site-specific geotechnical report by Geocon (2001), a review of museum paleontological records (SDNHM, San Diego Natural History Museum), and a walkover of the project site to field check the results of the literature and record reviews. RESULTS The project site lies on the crest of an ancient "beach ridge" that forms the highest ground on the relatively flat coastal mesa surface that characterizes this area of Carlsbad between Batiquitos Lagoon on the south and Canyon de las Encinas on the north. • D4-06-2002 0Z:46PM FROM-T-221 P.004/006 F-126 ... -- .', ., ~ _;:.; .. -,.t,· .' ., .. ,. 0 I. 0 I ,, •' f.--' .. -... --· -' .-·G .U .A • ... • ... l •, ... -.. ',, / H /E D .. i CZ:·· ::i ,.. . ,;(2 i . ·I f MILE 1000 FEET O 500m 1000ffl j •• ] I ... , I· ,,_ I j • : I ' -I : j :::J P:rh\tQd UOlrl TOPO! @2000 Wildflower Productio:ns (www.topo.com) Fieure 1. Index map showing location of the Tabata Property project site. Base map USGS 7.5 minute Encinitas, CA. .. -.: ·.•'\. ·" . __ -;.~ ... ;.,;'':. ... , 04-06-2002 02 :47PU FROU-T-221 P.005/006 F-126 Elevations range from about 350 feet on the eastern and western borders of the site to 383 feet along the southern border. Existing residential development exists to the north and east of the site. An unlandscaped roadcut along Cahela 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 underlain by early Pleistocene-aged ( 400,000~ 700,000 years old) sedimentary roel<:s of the Lindavista Formation. The site specific geotechnical report of Geocon (2001) records sedimentary rocks of the Lindavista Fonnation as occurring in the subs1.trface, at least to a depth of six feet. A thin veneer of modem alluvium was mapped in the northwe$tem comer of the site. Lindavista Formatio,n Introduction-The Lindavista Formation on the 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 eastern roadcut along Cabala Place. The total thickness of this 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 the Lindavista Fonnation 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 unit has subsequently been mapped into northern San Diego Cotinty where it includes both fine and coarse-grained sedimentary rocks. The Lindavista Fom1ation is hypothesized to have fanned in nearshore marine, beach, and coastal sand dune depositional environments. Paleontology~ Sparse fossil remains have been recovered from this rock unit in the Carlsbad area. Two collecting sites are documented in the locality records of the SDNHM and occur one-half mile nonheast of the Tabata Property site. Fossils from these recorded localities consist of poorly~preserved molds and casts of marine molluscs and echinoderms. The fossils were discovered at the extreme base of the Lindavista Formation where it directly overlies Eocene-age sandstones of the Santiago Fom1ation. In the metropolitan San Diego area the Lindavista Fonnation has produced better preserved fossils of marine molluscs, crustaceans, and echinodem1s, as well as sparse skeletal remains of marine vertebrates (sharks, rays, and cetaceans) (Demere and Walsh, I 993). Distribution• The Lindavista Formation underlies the entire project area. Resource Sensitivity-The Lindavista Formation on the project site is assigned a low paleontological sensitivity based upon the thick nature of this rock unit on the Tabata Property site and the fact that fossils from this rock unit almost always occur at its very base. , ~4-06-2002 02:47PU FROM-· T-221 P.006/006 F-126 IMP ACT ANALYSIS Direct impacts to paleontological resources occur when earthwork activities, such as mass grading , cut into the geologic deposits (fonnations) within which fossils are buried. These direct impacts are in the form of physical destruction of fossil remains. Tentative grading plans for the Tabata Property project site indicate that on site cuts will be confined to the upper portions of the Lindavista Formation and will not reach the typically fossiliferous base of the fom1ation, which is projected to occur at about elevation 320 feet in this area of Carlsbad. 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 fom1ations are significant and, under CEQA guidelines, require mitigation. The impact analysis presented above indicates that grading will not impact the fossiliferous portions of the Lindavista Formation. MITIGATION MEASURES Because development of the Tabata Protperty project site will not produce any impacts to significant paleontological resources, there is no need for implementation of a resource mitigation program. Thomas A. Demere, Ph.D. Department of Paleontological Services