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

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Author
Mulliken, Katherine M.
Chair
Reuther, Joshua D.
Potter, Ben A.
Committee
Clark, Jamie L.
Wallace, Kristi L.
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URI
http://hdl.handle.net/11122/6632
Abstract
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 valley, Alaska, and provided a more complete context for interpretation of the archaeological record.
Description
Thesis (M.A.) University of Alaska Fairbanks, 2016
Table of Contents
Chapter 1: Introduction -- 1.1 Tephra and tephra analysis -- 1.2 Anthropological studies in volcanically active regions -- 1.3 Research objective and specific research questions -- 1.4 Thesis organization -- Chapter 2: Background -- 2.1 Study area -- 2.1.1 Physiography -- 2.1.2 Paleoenvironment -- 2.1.3 Modern climate and ecology -- 2.2 Middle Susitna River Valley stratigraphy -- 2.2.1 General stratigraphy -- 2.2.2 Tephra correlations -- 2.2.3 Hayes Volcano and plinian eruptions -- 2.3 Archaeological investigations in the mSRV -- 2.3.1 Archaeology of the mSRV and the region -- 2.4 Problems and potential solutions -- 2.5 Summary -- Chapter 3: Materials and Methods -- 3.1 Tephra analysis -- 3.1.1 Tephra sample selection -- 3.1.1.1 Proximal Hayes Volcano reference tephra -- 3.1.2 Tephra sample processing and preparation -- 3.1.3 Tephra geochemistry -- 3.1.4 Data correction and filtering -- 3.1.5 Statistical analysis of tephra geochemical data: SIMAN similarity coefficient for correlation -- 3.2 Chronometric evaluation -- 3.2.1 Radiocarbon sample selection -- 3.2.2 Radiocarbon analyses -- 3.2.3 Methods of radiocarbon database construction -- 3.2.4 Radiocarbon database -- 3.2.5 Radiocarbon data calibration -- 3.2.5.1 Bayesian age models -- 3.3 Analysis of archaeological materials -- 3.3.1 Creating the mSRV site database -- 3.3.2 Variables considered -- 3.3.3 Analyses of archaeological sites in the mSRV -- 3.4 Qualitative model building for understanding effects of tephra deposition -- 3.5 Theoretical approach: Human behavioral ecology -- 3.5.1 Optimal foraging theory and patch choice models -- 3.5.2 Constraints: resources, mobility, and risk -- 3.6 Summary -- Chapter 4: Results -- 4.1 Tephra analyses -- 4.1.1 Results of EPMA of tephra -- 4.1.1.1 Middle Susitna River Valley reference archaeological tephra -- 4.1.1.2 Other mSRV archaeological tephra from informal tephra units -- 4.1.1.3 All other archaeological unknown tephra samples -- 4.1.1.4 Hayes Volcano reference tephra -- 4.1.2 Similarity coefficient -- 4.1.2.1 Correlating mSRV reference tephra with proximal Hayes Volcano reference tephra -- 4.1.2.2 Similarity coefficient between archaeological tephra samples for geochemical groups -- 4.1.1.3 All other archaeological unknown tephra samples -- 4.1.1.4 Hayes Volcano reference tephra -- 4.1.2 Similarity coefficient -- 4.1.2.3 Similarity coefficient calculations between mSRV tephra unit geochemical groups and Hayes Volcano reference tephra -- 4.1.3 Summary of tephra geochemical analyses and correlations -- 4.2 Results of chronometric evaluation -- 4.2.1 New mSRV dates -- 4.2.2 Revised mSRV chronology -- 4.2.2 Bayesian age model results -- 4.2.2.1 Bayesian calibration of dates from site TLM-216 -- 4.2.2.2 Bayesian calibration for tephra deposition -- 4.3 Archaeological analyses -- 4.4 Summary -- Chapter 5: Volcanic events and their effects: qualitatively modelling the effects of tephra deposition in the mSRV -- 5.1 Eruption dynamics, deposits, and consequences -- 5.1.1 Using volcanic events as analogs: potential disconnects -- 5.1.2 Consequences of tephra deposition -- 5.2 Understanding the effects of tephra deposition in the mSRV -- 5.2.1 Tephra preservation in the mSRV -- 5.2.2 Vegetation succession in Alaska -- 5.2.3 Seasonal considerations of tephra deposition in the mSRV -- 5.2.4 Immediate effects of ash deposition on humans -- 5.2.5 Tephra deposit thicknesses in the mSRV -- 5.3 Summary -- Chapter 6: Discussion -- 6.1 Clarifying the stratigraphic contexts of the mSRV -- 6.1.1 Geochemical characterization and correlation of mSRV tephra -- 6.1.2 Revised dating of mSRV tephra -- 6.2 Archaeological contexts of tephra depositions in the mSRV and their effects -- 6.2.1 Oshetna tephra: Context, deposition and effects -- 6.2.2 Watana tephra: Context, depositions, and effects -- 6.2.3 Devil tephra: Context, deposition, and effect -- 6.2 Evaluating responses to ashfalls in the mSRV -- 6.3 Summary -- Chapter 7: Conclusion -- 7.1 Future Directions of Research -- 7.2 Conclusion -- References cited -- Appendices.
Date
2016-05
Type
Thesis
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