PALEONTOLOGY PROJECTS

The Portola Center (Tract 15353) Project involved the removal and redistribution of over 1.8 million cubic yards of earth on a 95-acre site in the foothills of the Santa Ana Mountains for the construction of 331 single-family homes, a 256-unit townhouse complex, streets, parks, and open spaces.  Impacts to potential paleontological resources at the project were addressed in the City of Lake Forest’s Opportunities Study Area Final Program Environmental Impact Report, which based its findings and conclusions regarding paleontological resource mitigation measures upon BFSA’s paleontological assessment report, pursuant to CEQA regulations.  In the assessment, BFSA concluded that the underlying geologic formations were highly sensitive regarding the potential to yield fossils.

After over four years of monitoring at the project, an abundance of deep-water marine invertebrate and vertebrate faunas from the middle to late Miocene Epoch (nine to 14 million years old) were recovered.  Over 320 fossils were obtained from multiple field collections assigned to 76 museum localities.  Notable fossils included a very large, new species of right whale, the skull and upper body bones of a toothed whale preserved inside a boulder, and the rear feet of a walrus.  Over 15 species of fossil fish and sharks were recovered, including bones from the six-foot-long, saber-toothed salmon and teeth from an ancient species of mako shark and the giant Megalodon.  The most common fish was Ganolytes cameo, an extinct species of sardine over a foot long with fingernail-sized scales.  The fossil mollusk collections represent a rarely seen Miocene assemblage of deep-water species.  These specimens are currently under a joint study by United States Geological Survey and BFSA paleontologists.  The results of the study will be published by 2021.

BFSA has extensive experience guiding residential projects to meet rigorous City of San Diego-mandated Mitigation Monitoring and Reporting Program guidelines for paleontological resources. For example, a new bluff-top real estate project involved extensive underground excavation for a subsurface garage and other amenities. The homesite is perched at the edge of a seaside cliff overlooking Tourmaline Surfing Park. The geology is spectacularly expressed on the face of the 70-foot-high cliff, accounting for multiple scientific publications over the past 50 years and visits by thousands of geology students. Most of the bluff is composed of the 47-million-year-old Mount Soledad Formation, but ironically, fossils from this extensive outcrop were unknown. As a result of monitoring during drilling and excavation for the building’s subsurface structures, impressions of a diverse assortment of fossil shells were discovered from this formation for the first time, and, as a result, a scientific article authored by BFSA scientists with assistance from a United States Geological Survey paleontologist is forthcoming to document the significance of the finds.

Downtown San Diego overlies geologic formations rated as having a “High Sensitivity” by the County of San Diego and the City of San Diego for the potential to yield paleontological resources.  These sensitivity ratings are based upon the occurrence and distribution of known fossil localities.  Dr. George Kennedy of BFSA was consulted to advise the panel responsible for drafting the City of San Diego’s final paleontological mitigation, monitoring, and reporting guidelines.  Dr. Kennedy’s field and managerial experience include dozens of downtown projects, the majority of which yielded fossils.

For example, the Allegro Tower, Pinnacle Marina Tower, and Parkloft Apartments projects are a part of downtown San Diego’s vast, ongoing, two-decade-long redevelopment endeavors, and impacts to rich, fossiliferous strata are common.  Typically, large apartment towers require underground parking that goes 50 feet deep or deeper.  As a consequence, layer after layer of sediments, representing multiple transgressions and regressions of the sea that are a result of glacial ice fluctuations, can be viewed.  These layers of sediments frequently contain a wealth of fossil shells.  BFSA scientists were able to distinguish and separate shell faunas at these and other downtown projects; as a result, the chronologic order of middle to late Pleistocene sea level advances and withdrawals can be interpreted with greater ease and precision within the layers of sediments that are encountered.  Headed by Dr. Kennedy of BFSA, the results from these projects were published in a report for the Western Society of Malacologists.  This report continues to influence the BFSA monitoring staff and serves the scientific community of San Diego at large as a valuable, subsurface guide for subsequent downtown projects.

The Riverside County Flood Control and Water Conservation District retained BFSA to fulfill CEQA requirements for the channelization of a natural drainage. Stage 6 involved grading and excavation activities for a three-mile segment of the Salt Creek Channel roughly between Menifee and Diamond Valley Lake. The bones and teeth of large Ice Age mammals were recovered, including those of giant ground sloth, black bear, horse, camel, two species of bison, and numerous unidentifiable bones. Additionally, the milk tooth of a young mastodon was recovered, as well as a partial skeleton of a mammoth that included a 4.5-foot-long tusk. The condition of the bones suggests that animals trampled the mammoth skeleton before its burial. Wet screening techniques yielded a species of freshwater or land snail. These localities are partly correlative with the rich vertebrate faunas of the Domenigoni Valley just to the east, and serve to add additional information to reconstruct the animal populations of southern California during the Pleistocene.