WELL-RESOLVED FLORAL RECORD FROM RANCHO LA BREA REVEALS LOCAL-SCALE DEVIATIONS FROM REGIONAL CLIMATE AND VEGETATION DYNAMICS

Prolonged glacial and interglacial stages, more abrupt stadial and interstadial shifts, fluctuating atmospheric carbon concentrations, and large-magnitude faunal extinctions in the late Pleistocene had well-studied impacts on vegetation. But these studies have generally been conducted on relatively coarse spatial and taxonomic scales, and may not reflect finer-scale climate-vegetation dynamics. The Rancho La Brea locality in California, USA, is one of the most important Quaternary paleontological assemblages in the world, but interpretation of the climate-vegetation-fauna dynamics of the site can only be fully understood through such finer-scale resolution. In this study we assessed vegetation and climate dynamics on a local scale with a unique high-taxonomic-resolution reconstruction of plant community change across the Late Pleistocene and Holocene through accelerator mass spectrometry (AMS) dating of 146 asphaltic plant macrofossils excavated from the La Brea Tar Pits alongside flora-climate coexistence analysis. Preliminary findings indicate local climate and plant communities deviated from more regional patterns of increased Pinus presence and moisture at the last glacial maximum. Conversely, La Brea reveals an opposite pattern of conifer extirpation and potentially increasing aridity into the last glacial maximum. The local flora during the glacial maximum is represented by Juniperus species. The large mammal fauna preserved from this time at La Brea must be considered in this context.