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Home My WebLink AboutCT 98-05; De Jong Property; Tentative Map (CT) (8)I I PALEONTOLOGICAL RESOURCE ASSESSMENT, • MORNING RIDGE PROJECT, DE JONG PROPERTY, CITY OF CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA • (CT 98-05) I For: I I Keystone Communities 1 5333 Mission Center Road, Suite 360 San Diego, California 92108 I I - By: I • Brian F. Smith and Associates Archaeological, Historical, and Paleontological Consulting 14678 Ibex Court, San Diego, California 92129 I I I 8 April 2003 I I I i i I i i i i i i i i i i i i i i i Paleontological Monitoring for the Morning Ridge Project INTRODUCTION The California Environmental Quality Act (CEQA) requires local governmental agencies to consider potential impacts to paleontological resources and mandates that mitigation measures be implemented when these resources are likely to be threatened by construction related activities. In the City of Carlsbad, the Planning Department, pursuant to CEQA regulations for excavation and/or construction activities, requires a mitigation, monitoring, and reporting program be instituted when such an activity occurs in areas that have been judged to be paleontologically sensitive based on the distribution of known fossil localities or of potentially fossil-bearing sedimentary formations (cf. Demere and Walsh, 1993). A paleontological resource assessment of the de Jong property/Morning Ridge project site (see attached vicinity map) was conducted to evaluate the potential for discovery of unrecorded paleontological resources that might require a paleontological mitigation and monitoring program to be implemented. The paleontological assessment involved examination of published geologic maps, evaluation of the local formational units for their paleontological resource potential (cf. Demere and Walsh, 1993), a field survey, and examination and interpretation of locality collection records of the San Diego Natural History Museum for data on nearby fossil localities. ASSESSMENT The de Jong property/Morning Ridge project is an approximately 33.4 acre parcel of land within the central part of Carlsbad east of Black Rail Road and north of the Poinsettia Lane extension (under construction). The project is situated on a remnant of a high marine terrace (Clairemont terrace of Kern and Rockwell, 1992 [=1993]) overlooking a northward draining canyon that is tributary to Canyon de las Encinas (Palomar Airport Road alignment) on the north. The project site is centrally located between Canyon de las Encinas on the north, El Camino Real on the east, Batiquitos Lagoon on the south, and the Interstate 5 freeway on the west. This project site occupies the northwest quarter of the southeast quarter of Section 22 of Township 12 South, Range 4 West, SBBM, as shown on the U. S. Geological Survey 7.5-minute, 1:24000 scale, topographic map of the Encinitas, Calif, quadrangle (1968 edition, photorevised 1975). The project property is overlain by marine terrace sediments (Qt4 on the geologic map of Tan and Kennedy, 1996, pi. 2) that are typically assigned to the Lindavista Formation. The high marine terraces in northern San Diego County have yielded little in the way of fossil materials and the only published fauna from the formation is from the Tierrasanta area of San Diego (Kennedy, 1973) many miles to the south. The collection records of the San Diego Natural History Museum (SDSNH), however, show two localities in the Lindavista Formation in the vicinity, one along the eastern margin of the subject property. Both fossil localities are in the basal sediments of the Lindavista Formation, at an elevation of about 319 feet. Fossils include marine bivalve mollusks I I I I I I I I I I I I I I I I I I I Paleontological Monitoring for the Morning Ridge Project that have bored into the underlying Eocene sediments. The contact between the Lindavista Formation and underlying Eocene sediments is exposed along the mesa edge on the eastern margin of the subject property, and westward along the 320 foot (+/-) contour along the eastern edge of proposed house lots 8 through 28 (see Attachment), which overlook the present canyon. Paleontological monitoring of grading/earthmoving activities in this part of the project will be necessary to recover any fossils that are exposed during this phase of construction. The highest elevations on the subject property are in the southwest corner, but the sediments there are mainly eolian fine-grained sands that are characterized by the presence of small ironstone concretions typical of this part of the Lindavista Formation. The presence of fossils in this upper part is less likely. In the central Carlsbad area, and including the subject project, the marine terrace materials (Qt4, or Lindavista Formation) overlie marine, estuarine, and terrestrial sediments assigned to the middle Eocene (40-44 million year old) Santiago Formation (informal "member B") (Tsa on the geologic map of Tan and Kennedy, 1996, pi. 2). "Member B" of the Santiago Formation locally has yielded very important marine invertebrate and terrestrial vertebrate faunas, as well as paleobotanical specimens (San Diego Natural History Museum collection records), and is assigned a "high paleontological resource sensitivity" by Demere and Walsh (1993, p. 21). The Santiago Formation, if encountered below the Lindavista Formation, would also require paleontological monitoring in order to recover any fossils that might be exposed during grading/earthmoving activities. SUMMARY A paleontological resource assessment of the de Jong property/Morning Ridge project in the central part of Carlsbad, San Diego County, California, supports the necessity of a paleontological monitoring and mitigation program during grading and/or earthmoving activities that may occur in conjunction with developing the property. The subject property is overlain by middle to lower Pleistocene marine terrace sediments (the Lindavista Formation) that have been assigned a "moderate paleontological resource sensitivity" by Demere and Walsh (1993), and underlain by the middle Eocene Santiago Formation, which has been assigned a "high paleontological resource sensitivity." The presence of known fossil localities that have yielded marine invertebrate fossils from the basal Lindavista Formation on the east side of the property, and at another locality close by to the southeast, support the necessity of paleontological monitoring, particularly at or near the contact of the Lindavista Formation and underlying Eocene sediments (approximately equivalent to the 320 foot contour level), which are exposed along the eastern margins of proposed house lots 8 through 28. Paleontological Monitoring for the Morning Ridge Project REFERENCES Demere, T. A., and Walsh, S. L. 1993. Paleontological resources, County of San Diego. Unpublished report prepared for the San Diego County Department of Public Works, San Diego, California. 68 pp., figs. 1-3, 8 map sheets. Kennedy, G. L. 1973. A marine invertebrate faunule from the Lindavista Formation, San Diego, California. Transactions of the San Diego Society of Natural History, 17(10): 119-127, figs. 1-3. Kern, J. P., and Rockwell, T. K. 1992 [1993]. Chronology and deformation of Quaternary marine shorelines, San Diego County, California. In Fletcher, C. H., ffl, and Wehmiller, J. F., eds., Quaternary coasts of the United States: Marine and lacustrine systems. SEPM (Society for Sedimentary Geology), Special Publication, no. 48: 377-382, figs. 1-2, tables 1-4. 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, pis. 1-2 (map sheets, 1:24,000). f,ANOW AZUA HSDIONDA MAP NO. 323 OCEAN BLUFF .03-00 AVIARA RELOCATED 16' S.D.G. <fc £. ACCESS ROAD DEJONG, CARLSBAD / CT 98-05