DECIPHERING BIOTIC RESPONSES TO RAPID CLIMATE CHANGE AT THE PLIO-PLEISTOCENE BOUNDARY

Research from the western Atlantic region indicates that the Pliocene-Pleistocene is a dynamic period for taxonomic loss and origination resulting from the closing of the Panama Isthmus. Evidence from the Atlantic and the Pacific suggests that this tectonic change altered ocean circulation patterns and redistributed sea surface temperature (SST) and nutrients, which affected marine communities. This study examines the pattern of extinction and origination within the eastern Pacific marine communities during the Plio-Pleistocene transition. It also constrains the location of the Pliocene-Pleistocene boundary in the San Diego Formation via foraminifera biostratigraphy. Eight fossil beds were sampled for a macro-faunal analysis. Macrofossils were sieved and identified in order to calculate diversity and abundance rates throughout the section. Samples were collected for the foraminifera biostratigraphy at 1.5 meter intervals along an approximately 30 meter section of the San Diego Formation, San Diego County, CA. Foraminifera were picked directly from the sand samples. All of the macro-fossils identified were epifaunal suspension feeders. Pectin bivalves are found throughout the section, along with intermittent high-spired gastropods. The abundance and diversity of the taxa varied throughout the section. It is our goal to combine faunal data with results from Stable Isotope Analysis, tracking SST and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), tracking nutrient variation through time. Multivariate statistics will determine casual links between the data. Understanding biotic responses to climate change during recent geological time, affords key insight for modeling and planning for future anthropogenic climate change. The Plio-Pleistocene boundary provides a unique laboratory to examine how environmental change affects life on Earth and can provide direct insights into our present-day biodiversity crisis for two reasons: 1) many Plio-Pleistocene taxa are extant thus providing a direct prediction of how modern taxa might respond to rapid climate change; and 2) the proposed environmental analyses provides a more rigorous and detailed analysis than previous studies, thus providing a more direct comparison with modern climate patterns.