BrGDGT temperature reconstruction from interior Alaska: Assessing 14,000 years of deglacial to Holocene temperature variability and potential effects on early human settlement

Abstract

Aeolian deposits in the middle Tanana Valley of central Alaska offer a well-preserved record of paleoenvironmental change since the deglacial period (c. 16,000–11,000 cal yr BP). These deposits also contain some of North America's oldest archaeological occupations (c. 14,000–13,000 cal yr BP), making this region critically important for understanding human migration into the high latitudes and the Americas. Major research questions involve assessing the magnitude of deglacial climatic change and the influence of climate on early human groups. This study uses branched glycerol dialkyl glycerol tetraethers (brGDGTs) from six loess-paleosol sequences to develop a quantitative paleotemperature record within terrestrial locations in the Tanana basin that are close to archaeological sites. BrGDGT-derived temperatures demonstrate a lack of cooler temperatures associated with deglacial conditions, making this region relatively “warm” compared to other parts of the globe. Additionally, our brGDGT record shows little coherent temperature change associated with deglacial climate variability (e.g., Bølling-Allerød, Younger Dryas), and Holocene temperatures are relatively stable as well, indicating that temperature fluctuation was not the main driver of environmental or archaeological change over time. We recommend averaging data across multiple terrestrial exposures to produce regional temperature reconstrutions.