PALEONTOLOGICAL RESOURCE ASSESSMENT 6231 EAST WIMBLEDON COURT CITY OF ORANGE ORANGE COUNTY, CALIFORNIA

Prepared for:

LAGUNA MOUNTAIN ENVIRONMENTAL 7969 ENGINEER ROAD, SUITE 208 SAN DIEGO, CA 92111

Prepared by:

DEPARTMENT OF PALEOSERVICES SAN DIEGO NATURAL HISTORY MUSEUM P.O. Box 121390 SAN DIEGO, CA 92112

Shelly L. Donohue, Paleontological Report Writer Thomas A. Deméré, Ph.D., Director

11 January 2016

1.0 INTRODUCTION

1.1 PROJECT DESCRIPTION AND SCOPE OF WORK This technical report provides an assessment of paleontological resources at the 6231 East Wimbledon Court project site in the City of Orange, Orange County, CA. The project site is located in the southeastern portion of the City, about 0.25 miles east of the intersection of Chapman Avenue and Canyon View Avenue (Figure 1). The site is bordered to the north by a steeply dipping, undeveloped slope, to the south by existing residential family homes, to the east by existing single family residential properties and the eastern terminus of Pheasant Lane, and to the west by vacant lots previously graded for single family homes. The proposed project involves construction of a new 8-lot subdivision of single family residential homes and a clubhouse, as well as associated infrastructure (e.g., utilities, streets, driveways, sidewalks, landscaping). The single family homes are proposed to be 2-story wood frame structures with partially subterranean lower levels supported by shallow foundations. As indicated in the geotechnical report (Geomat Testing Laboratories, Inc., 2015), previous development at the project site has created several terrace structures through emplacement of artificial fill, but this fill is unsuitable to support the proposed buildings. Thus, earthwork at the proposed project will involve removal of existing fill and placement of additional, compacted fill at each of the proposed lots. Because earthwork at the project site has the potential to impact native sedimentary rocks, it was determined that a paleontological resource assessment should be conducted, in order to determine whether the proposed project has potential to negatively impact paleontological resources. This assessment report is intended to summarize existing paleontological resource data in the project area, discuss the significance of these resources, examine project related impacts to paleontological resources, and suggest mitigation measures to reduce impacts to paleontological resources to less than significant levels. The assessment includes the results of an institutional records search of the paleontological collections at the San Diego Natural History Museum (SDNHM). This report was written by Shelly L. Donohue and Thomas A. Deméré of the Department of PaleoServices, SDNHM. 1.2 DEFINITION OF PALEONTOLOGICAL RESOURCES 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 geological 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 the age of 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 of the 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 structure of ancient ecosystems, and the pattern and process of organic evolution and extinction. In addition, fossils are considered

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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.

2.0 METHODS

2.1 PALEONTOLOGICAL RECORDS SEARCH AND LITERATURE SEARCH A paleontological record search was conducted at SDNHM in order to determine if any documented fossil collection localities occur within the project site or immediately surrounding area. The record search involved examination of the SDNHM paleontological database for any records of known fossil collection localities within a 1-mile radius of the proposed project site. Informal record searches of the online collections databases at the Natural History Museum of Los Angeles County (LACM) and University of California Museum of Paleontology (UCMP) were also conducted. Additionally, a review was conducted of relevant published geologic maps and reports, published paleontological reports, and other relevant literature (e.g., field trip guidebooks, theses and dissertations, unpublished paleontological mitigation reports). This approach was followed in recognition of the direct relationship between paleontological resources and the geologic formations within which they are entombed. Knowing the geologic history of a particular area and the fossil productivity of geologic formations that occur in that area, it is possible to predict where fossils will, or will not, be encountered.

2.2 RESOURCE ASSESSMENT CRITERIA: PALEONTOLOGICAL POTENTIAL For the present report, the following levels of paleontological resource potential are used to rate individual geologic rock units/formations, following the guidelines of the Society of Vertebrate Paleontology (SVP, 2010). 2.2.1 HIGH PALEONTOLOGICAL POTENTIAL High potential is assigned to geologic formations known to contain paleontological localities with rare, well-preserved, critical fossil materials for stratigraphic or paleoenvironmental interpretation, and fossils providing important information about the paleobiology and evolutionary history (phylogeny) of animal and plant groups. Generally speaking, highly sensitive formations produce vertebrate fossil remains or are considered to have the potential to produce such remains. 2.2.2 UNDETERMINED PALEONTOLOGICAL POTENTIAL Undetermined potential is assigned to geologic formations that have little to no information available concerning their geologic context (e.g., depositional environment, age) and/or contained paleontological resources. 2.2.3 LOW PALEONTOLOGICAL POTENTIAL Low potential is assigned to geologic formations that, based on their relative youthful age and/or high-energy depositional history, are judged unlikely to produce important fossil remains.

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Formations that produce invertebrate fossil remains in low abundance are also assigned a low paleontological potential. 2.2.4 NO PALEONTOLOGICAL POTENTIAL Zero potential is assigned to geologic formations that are entirely igneous in origin and therefore have no potential for producing fossil remains, or to artificial fill materials which lose the stratigraphic/geologic context of any contained organic remains (e.g., fossils). 2.3 PALEONTOLOGICAL IMPACT ANALYSIS Direct impacts to paleontological resources occur when earthwork activities (e.g., mass grading, trenching), cut into the geological rock units within which fossils are buried, and physically destroy the fossil remains. As such, only earthwork activities that will disturb potentially fossil-bearing sedimentary rocks (i.e., those rated with a high or moderate paleontological sensitivity) have the potential to significantly impact paleontological resources. The purpose of the impact analysis is to determine which (if any) of the proposed project-related earthwork activities may disturb potentially fossil-bearing sedimentary rocks, and where and at what depths this earthwork will occur. The paleontological resource impact analysis involved analysis of all available project documents (e.g., grading plans, geotechnical report), and comparison with geological and paleontological data gathered during the record search and literature search.

3.0 EXISTING CONDITIONS

3.1 GEOLOGIC SETTING The proposed project site lies within the northern portion of the Peninsular Ranges Geomorphic Province of California, and more specifically within the Santa Ana Valley – Capistrano Valley Province of Orange County. The valley occurs adjacent to the western foothills of the Santa Ana Mountains. Here, Mesozoic basement rocks of the Jurassic-Cretaceous Santiago Peak Volcanics and the Cretaceous Peninsular Ranges Batholith are nonconformably overlain by sedimentary rocks of late Cretaceous through Pleistocene age that are locally interbedded with volcanic rocks (e.g., Yerkes, 1957; Shoellhamer et al., 1954; 1981). Published geologic mapping (e.g., Morton and Miller, 2006; Figure 1) indicates that the project site is entirely underlain by deposits of the El Modeno Volcanics, a middle Miocene volcanic rock unit that is interbedded with marine sedimentary rocks of the Topanga Formation. In the vicinity of the proposed project site, El Modeno Volcanics are locally overlain by compact to unconsolidated Quaternary terrace deposits, colluvium, and/or artificial fill materials (GeoMat Testing Laboratories, Inc., 2015). 3.1.1 EL MODENO VOLCANICS The El Modeno Volcanics have been subdivided into three members: a lower basalt flow member, a middle tuff and tuff breccia member, and an upper andesite flow and flow breccia member (Yerkes, 1957). The volcanic rocks underlying the proposed project site are predominantly composed of the tuff and tuff breccia member, with the lower basalt flow member cropping out in the southeast corner (Figure 1). The basalt flow member typically consists of a massive, vesicular,

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porphyritic olivine basalt that appears to represent a single, extensive flow. Capping the basalt in some places is a thin (~4 foot thick) siltstone or claystone deposit. The overlying tuff and tuff breccia member generally consists of alternating horizons of light gray to tan alternating tuff breccia and well-sorted and bedded tuffs. The tuff breccia is less common within the member, but where present consists of angular blocks or lapilli of andesite in a tuffaceous matrix. The extensive tuffs are typically thinly bedded (average of 0.5 inches thick) and well-sorted (Yerkes, 1957). 3.1.2 QUATERNARY SEDIMENTARY DEPOSITS As noted in the geotechnical report (GeoMat Testing Laboratories, Inc., 2015), although not previously mapped at the project site, Quaternary colluvial deposits and underlying Quaternary terrace deposits occur as thin veneers overlying the volcanic bedrock. These Quaternary deposits are thickest in the southern portions of the project site and thin and eventually pinch out to the north, in areas of higher elevation. The colluvial deposits are up to 4 feet thick, and are likely Holocene in age (less than about 11,000 years old). The underlying terrace deposits are up to 12.5 feet thick, and based on the geologic mapping of Yerkes (1957) and Morton and Miller (2006) are likely correlated with the alluvial deposits cropping out about 750 feet to the west of the project site. Morton and Miller (2006) consider these deposits to be middle to late Pleistocene in age. Both the colluvial deposits and terrace deposits are described as consisting of silty sands, sandy silts, and sandy clays with occasional gravels (GeoMat Testing Laboratories, Inc., 2015).

4.0 RESULTS

4.1 RESULTS OF THE PALEONTOLOGICAL RECORD SEARCH AND LITERATURE SEARCH There are no SDNHM fossil collection localities located within a 1-mile radius of the proposed project. Results of informal searches of the LACM and UCMP online paleontological collections databases as well as a literature search are summarized below. 4.1.1 EL MODENO VOLCANICS The UCMP and LACM collections databases contain no records of fossils collected from any outcrops of the El Modena Volcanics. This is not surprising, since fossils are generally not preserved in basalt flow deposits because of the destructive, high temperature conditions present during formation. However, Yerkes (1957) reports silicified fossil remains of bony fish and foraminifera from a thin siltstone or claystone unit that in some places locally caps the basalt flow member. Presumably, these fossils represent marine mass die-offs that occurred during volcanic eruptions (Cooper, 2003). There are also reports of marine invertebrate fossils from tuff beds of the El Modeno Volcanics where it interfingers with the marine Topanga Formation (M.A. Roeder, pers. comm.). These reported fossil occurrences, however, do not occur in the project area. 4.1.2 QUATERNARY SEDIMENTARY ROCKS Colluvial deposits are generally not known to contain significant fossilized remains, due to their relatively young, Holocene age, and fossil remains within colluvium from Orange County were not identified within the LACM or UCMP online collections. Fossils are known to occur within Pleistocene-age alluvial sediments in Orange County and nearby western Riverside County, and include well-preserved remains of large bodied mammals, including ground sloths, mammoths, mastodons, camels, bison, dire wolves, sabertoothed cats,

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American lions, and giant short-faced bears (e.g., Jefferson, 1991; Anderson et al., 2004; Springer et al., 2009; 2010). However, no reports of Pleistocene land mammals are known in the immediate vicinity of the project area. 4.2 RESULTS OF PALEONTOLOGICAL POTENTIAL ANALYSIS 4.2.1 EL MODENO VOLCANICS Both the tuff and tuff breccia member and basalt member of the El Modeno Volcanics are assigned a low paleontological resource potential. The tuff and tuff breccia member only produces fossils where it interfingers with the Topanga Formation; a condition which does not occur at the proposed project site. Although fossils are known from the siltstone and claystone horizon that locally caps the basalt member of the El Modeno Volcanics, such a horizon was not reported by geotechnical workers who surveyed the project site (GeoMat Testing Laboratories, Inc., 2015). 4.2.2 QUATERNARY SEDIMENTARY ROCKS The colluvial deposits at the project site are assigned a low paleontological potential based on their relatively young, Holocene age. The terrace deposits at the project site are assigned an undetermined potential, based on their possible (but uncertain) late to middle Pleistocene age, and the reported occurrence of fossils in terrace deposits exposed elsewhere in Orange County and western Riverside County. 4.3 RESULTS OF PALEONTOLOGICAL IMPACT ANALYSIS For the proposed project, the majority of earthwork will not impact deposits of the El Modeno Volcanics (low paleontological resource potential) or Quaternary sedimentary rocks (low to undetermined paleontological resource potential). Instead, the proposed excavations primarily will involve removal and recompaction of existing artificial fill materials. Once the removal excavations reach the previously undisturbed native rocks the excavations will cease, and new fill structures will be constructed. Thus, only very small veneers of the El Modeno Volcanics in the northern areas of the project (where Quaternary sedimentary rocks are absent) and colluvium in the southern portions of the project are anticipated to be impacted by construction. Notably, because the Quaternary terrace deposits are overlain by colluvium, they are not anticipated to be reached and impacted by construction-related excavations.

5.0 RECOMMENDATIONS

As discussed above in Section 4.3, only thin veneers of the El Modeno Volcanics and Quaternary colluvial deposits (low paleontological potential) are anticipated to be directly impacted by construction, while Quaternary terrace deposits (undetermined paleontological potential) are unlikely to be disturbed at all during construction. Based on these findings, paleontological resource mitigation is not recommended for the 6231 East Wimbledon Court Project.

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6.0 REFERENCES

Anderson, R.S., M.J. Power, S.J. Smith, K.B. Springer, and E. Scott. 2002. Paleoecology of a Middle Wisconsin deposit from southern California. Quaternary Research 58:310-317. Cooper, J.D. 2003. Geology and paleontology of Orange County. Unpublished report downloaded from http://www.jdcoopercenter.org/GEOLOGYandPALEONTOLOGYofORANGECOUNT Y.pdf. Jefferson, G.T., 1991. A Catalogue of Late Quaternary Vertebrates from California: Part Two, Mammals. Natural History Museum of Los Angeles County Technical Reports, No. 7. Morton, D.M. and F.K. Miller. 2006. Geologic map of the San Bernardino and Santa Ana 30' x 60' quadrangles, California: United States Geological Survey, Open-File Report 2006- 1217, scale 1:100,000.

Natural History Museum of Los Angeles County (LACM), unpublished paleontological collections data. Accessed January 2016.

San Diego Natural History Museum (SDNHM), unpublished paleontological collections data. Accessed January 2016.

Schoellhamer, J.E., D.M. Kinney, R.F. Yerkes, and J.G. Vedder. 1954. Geologic map of the northern Santa Ana Mountains, Orange and Riverside counties, California. USGS Oil and Gas Investigation Map OM-154.

Schoellhamer, J.E., J.G. Vedder, R.F Yerkes, and D.M. Kinney. 1981. Geology of the northern Santa Ana Mountains, California. U. S. Geological Survey Professional Paper 420-D:Dl– D9. Society of Vertebrate Paleontology (SVP). 2010. Standard procedures for the assessment and mitigation of adverse impacts to paleontological resources. 11p. https://vertpaleo.org/PDFS/68/68c554bb-86f1-442f-a0dc-25299762d36c.pdf Springer, K., E. Scott, J.C. Sagebiel, and L.K. Murray. 2009. The Diamond Valley Lake local fauna: late Pleistocene vertebrates from inland southern California. In L.B. Albright III (ed.), Papers on Geology, vertebrate paleontology, and biostratigraphy in honor of Michael O. Woodburne. Museum of Northern Arizona Bulletin 65:217-235. Springer, K., E. Scott, J.C. Sagebiel, and L.K. Murray. 2010. Late Pleistocene large mammal faunal dynamics from inland southern California: the Diamond Valley Lake local fauna. In E. Scott and G. McDonald (eds.), Faunal dynamics and extinction in the Quaternary: papers honoring Ernest L. Lundlius, Jr. Quaternary International 217: 256-265.

University of California Museum of Paleontology (UCMP) unpublished paleontological collections data. Accessed January 2016.

Yerkes, R.F. 1957. Volcanic Rocks of the El Modeno Area Orange County California. U.S. Geologic Survey Professional Paper 274-L: 313-335.

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