HOW GRASSY WERE LATE PLEISTOCENE HABITATS AT RANCHO LA BREA?: FIRST PHYTOLITH RECORDS FROM THE TAR PITS

Past reconstructions of Late Pleistocene habitats, vegetation types and animal diets at Rancho La Brea (RLB) have been based on dental microwear, mesowear, carbon isotopic records from bone collagen and enamel, and analysis of vegetative remains in boluses extracted from herbivore cheek teeth. Together, these records have suggested that habitat and herbivore diets at Rancho La Brea consisted mostly of C₃ vegetation, with woody plants making up a majority of the diet of Bison and Camelops to name a few. Though largely understudied, the macrobotanical record of the RLB deposits has yielded only a handful of grass fossils, further suggesting that grass biomass may have been low at RLB during the Late Pleistocene. We present new records of vegetation from well-preserved, fossil phytoliths extracted from the asphaltic sediments of Rancho La Brea. Although preliminary, our results suggest that C₃ pooid grasses were a dominant component of the herbaceous plant cover at RLB in deposits dating to ~40kya, and C₄ chloridoid and panicoid grasses were extremely rare, but present. Future phytolith work aims to track changes in grass composition throughout the Late Pleistocene and Holocene, and to incorporate modern reference collection material to identify grass species.