B13D-0559: Landscape patterns from plant biomarkers across early human habitats (ca. 1.845 Ma)

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Authors: Clayton R Magill1, Gail M Ashley2, Katherine H Freeman1

Author Institutions: 1. Geosciences, The Pennsylvania State University, University Park, PA, USA; 2. Earth and Planetary Sciences, Rutgers University, Piscataway, NJ, USA

Fine-scale spatial resolution reconstructions of early human (hominin) landscapes are key to understanding environmental and evolutionary processes that have shaped the genus Homo. Spatial distributions of artifacts and fossils are often interpreted in relation to specific landscape features (e.g., woody cover), but archaeological and faunal assemblages are indirect paleoecological indicators and lack stringent spatial constraints. Here, we present carbon-isotopic data for organic matter and plant biomarkers preserved in paleosols from the FLK Zinjanthropus archaeological level 22 (FLK Zinj) at Olduvai Gorge and 15 surrounding sites of stratigraphic equivalency. Plant biomarkers (leaf waxes and lignin oxidation products) reveal distinct differences in plant community composition, which were juxtaposed within just 100s of meters of each other. Central sites (including FLK Zinj) cover about 250 m2 and contain leaf waxes with low _13C values, which we interpret as evidence for woodland habitat. About 200 m to the north, aquatic leaf waxes and sedge lipids (5-n-alkylresorcinols) occur in conjunction with mound-like tufa deposits, suggesting freshwater wetland habitat. At southern sites, strongly 13C-enriched leaf waxes and lignin components diagnostic for non-woody plant tissues suggest open grassland habitat. Taken together, these data delimit the heterogeneous landscape at FLK Zinj, which has been hinted at by its archaeological assemblage, and reinforce that the site was a ‘central place’ for hominin activities because it afforded arboreal refuge and freshwater in an otherwise open and arid landscape. Taken together, this study highlights that fine-scale spatial habitat heterogeneities can be preserved by biomarkers in paleosols over geologic timescales.

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