FIRST AMERICANS ARCHAEOLOGY AND CLIMATE: SOIL CHEMISTRY AND ITS APPLICATIONS FOR GEOARCHAEOLOGY IN CENTRAL ALASKA

Understanding the effects of Quaternary climate events in central Alaska is crucial for addressing some of the most pressing research questions in First Americans archaeology. Differences in lithic technologies throughout the latest Pleistocene and earliest Holocene have been attributed to any one of a number of things, climate change included, but few conclusive, site-specific climate data are currently in use. Much of the work conducted in this area pre-dates modern geochemical techniques and, as a result, climate reconstructions are generally based on sedimentology and regional-or-larger-scale pollen analysis. Recent advances in paleopedology and sedimentary geochemistry now allow for a much more comprehensive and local-scale understanding of climate. This study employs such data at three central Alaskan archaeological sites: Owl Ridge, Dry Creek, and Linda’s Point. Soil micromorphology was employed to identify paleosol horizons within the stratigraphic sequences at each site. Soil magnetic susceptibility, d¹³C of soil organic matter (SOM) and whole soil chemistry were then used to assess changes in paleoprecipitation, paleotemperature and vegetation at each site in an attempt to correlate technology changes at these sites with major climatic shifts. This study serves a twofold purpose: to gather climate data relevant to the archaeology of the peopling of the Americas and to test a loess-calibrated variant of the CALMAG paleoprecipitation proxy newly developed using the Baylor University Paleosol Informatics Cloud (BU-PIC) database. The CALMAG proxy estimates paleoprecipitation (MAP) by using ( Al₂O₃)/ (Al₂O₃+CaO+MgO) in a paleosol. ICP-MS and ICP-AES elemental weight percentages were calculated for buried B horizons at each site. Data suggest that paleoprecipitation ranged from 570-730 mm/yr at Owl Ridge and 822-1193 mm/yr at Dry Creek. On average, these values are higher than modern precipitation at these sites (~400 mm/yr) and suggest a wetter climate during the latest Pleistocene and early Holocene than exists today. d¹³C values of SOM at Owl Ridge indicate dominance of C3 vegetation in the late Holocene but with possible inputs of C4 plants during drier periods in the mid- to early Holocene and latest Pleistocene.