Southeastern Section - 68th Annual Meeting - 2019

Paper No. 20-1
Presentation Time: 1:00 PM-5:00 PM


ALARCÓN TINAJERO, Edgar, Department of Anthropology, University of Georgia, 355 South Jackson Street, Baldwin Hall, Rm 250, Athens, GA 30602 and LEIGH, David S., Department of Geography, The University of Georgia, Geog.-Geol. Building, 210 Field St., Room 204, Athens, GA 30602

We report preliminary analyses of phytolith samples extracted from a Holocene stratigraphic section at the “Cliff Site” in a tributary arroyo to the Río Culebra in the semi-arid highlands of the Mixteca Alta in northern Oaxaca, Mexico. Radiocarbon dating on bulk sediment samples and charcoal from the stratigraphic section indicate deposition of sediment between 14,000 cal. yrs BP to the 16th century CE. The small tributary to the Cliff Site drains a watershed of approximately 8 km2, which includes a large archaeological site (Inguiteria) that was surrounded by cultivated terraced fields during the late Holocene. As such, agricultural modification to the landscape and presence of cultivars are expected to influence the phytolith composition of the latest Holocene portion of the stratigraphic sequence. Phytolith records are valuable corroborates for other paleoenvironmental proxies that elicit data on past vegetation cover. Biases of differential preservation and production by plant taxa are considered both in the sampling methods and data analysis. We highlight two general trends in the data: 1) a greater proportion of woody species phytoliths over grass phytoliths (C3 and C4 species) across strata and 2) higher C4 species over C3 species proportions except where grass phytoliths dominate. Calculated aridity indices and proportions of phytoliths indicate regular oscillation in the proportions of warmer-adapted and cooler-adapted plant communities with a preponderance of semi-arid adapted species over much of the Holocene. This phytolith record is a paleoenvironmental proxy augmenting similar records from sediment in more diverse geomorphological settings. As a paleoenvironmental proxy it also contributes to current understanding of human land-use histories in a dynamic environmental setting spanning the Holocene epoch.