PHYTOLITH, MOLECULAR, AND ISOTOPE ANALYSES FROM CHOLAME CREEK: A MULTI-PROXY MICROANALYTICAL APPROACH TO PALEOENVIRONMENTAL RECONSTRUCTION IN CENTRAL CALIFORNIA

In central California, the record of middle Holocene (ca. 7000 to 4000 cal BP) human occupation remains underrepresented compared to the late Holocene record. Declines in precipitation during the middle Holocene are thought to have significantly impacted prehistoric economies and influenced changes in land use. In this context, the central coast has been alternatively modeled as a refuge for populations fleeing droughts in interior California, or as an area itself impacted by drastic aridification, potentially resulting in wholesale abandonment of arid regions. The extent to which environmental changes actually affected human populations poses a continuing problem for archaeologists. The records that do exist suggest complex local variability in response to climate fluctuations across the Middle Holocene. This problem therefore requires precise reconstructions of paleoenvironmental records from different localities to better understand how changes were experienced differently by different populations.

This paper takes a multi-proxy micro-analytical approach to reconstructing the Early and Middle Holocene paleoenvironmental changes along Cholame Creek, a drainage within the Interior Coast Ranges near San Luis Obispo on the Central California Coast. Two exposed cut banks of Cholame Creek containing multiple buried paleosols dating between 12,000 and 3,000 cal BP offer a unique opportunity to study the detailed history of climate and vegetation change over time in a specific catchment area. The exposed geo-sections in these cut banks were recorded and sampled for molecular, isotope, and phytolith analysis. These analyses remain under-utilized in California archaeology and this study presents the potential of such techniques to better illuminate the paleoenvironmental potential of our approach.

This research was undertaken in coordination with excavations of a nearby multi-component pre-contact and historic site, and previous work in the nearby Cholame Flats has demonstrated extensive use of this area during the pre-contact Middle Holocene. This work contributes to refining local climatic patterns and paleoenvironmental change over time to help clarify human settlement patterns and substance strategies.