Holocene volcanism and human occupation in the middle Susitna River Valley, Alaska

by Katherine M Mulliken

Institution: University of Alaska – Fairbanks
Year: 2016
Posted: 02/05/2017
Record ID: 2071808
Full text PDF: http://hdl.handle.net/11122/6632


Archaeological and stratigraphic evidence from the middle Susitna River Valley, Alaska, reveals a rich record of human occupation during the Holocene, punctuated by volcanic ash deposits locally referred to as the Devil, Watana, and Oshetna tephras. Deposition of tephra in the middle Susitna River Valley had the potential to affect subsistence resources and lifeways of prehistoric peoples; however, ambiguities remain in dating both tephra deposits and cultural occupations, and in characterization of the tephra deposits. In addition, there has been little formal consideration of how deposition of tephra may have affected prehistoric hunter-gatherers using the middle Susitna River Valley (mSRV) during the Holocene and this research seeks to fill that gap. Electron probe microanalysis is used to geochemically characterize the middle Susitna River Valley tephra, enabling correlation to reference tephra from Hayes Volcano and aiding in determining the number of volcanic events present in the stratigraphic record of the middle Susitna River Valley. Assimilation of existing radiocarbon dates from multiple sources with new AMS radiocarbon dates produced as part of this study allows for estimating the timing of tephra deposition and evaluating the timing of cultural occupation of the area with greater precision. Characteristics of archaeological assemblages bounded by tephra deposits are also evaluated relative to existing frameworks for understanding prehistoric hunter-gatherer behavior in interior Alaska. Interpretation is aided by consideration of other tephra depositional events and their environmental and ecological effects. Results suggest that at least four tephra depositional events took place in the middle Susitna River Valley. The Devil tephra was deposited between 1625-1825 cal yr B.P. (calibrated years before present). The Watana tephras, which correlate to the Hayes Volcano tephra set H, were deposited between 3360-4400 cal yr B.P., with the upper and lower portions of this tephra deposited either in rapid succession or separated in time by only a few hundred years. The Oshetna tephra was deposited between 6570-7970 cal yr B.P. While the Devil, upper and lower Watana tephras represent discrete volcanic events, the Oshetna tephra has multiple glass compositions and therefore it is unclear whether this tephra represents an eruption with a heterogeneous composition or multiple discrete tephrafalls compounded in the mSRV. Potential hiatuses in cultural occupation of the mSRV occur following deposition of these tephras, but characteristics of archaeological assemblages in the mSRV are in accordance with general transitions in central interior Alaskan archaeology. Information from other volcanic events suggests that tephra deposition in the middle Susitna River Valley would have affected resource procurement in the area and therefore likely contributed to cultural hiatuses, especially following deposition of the Watana tephra. This project has clarified the Holocene stratigraphic sequence of the middle Susitna River… Advisors/Committee Members: Clark, Jamie L. (committee).