This project supports the dissertation research by Co PI Joshua Reuther. The research supported will complete laboratory analyses on aeolian geologic records of dune formation and deflation in the Tanana river basin in order to reconstruct the terrestrial paleoenvironment during the end of the Pleistocene and early Holocene. This research is particularly important in light of the 11,500 yo child creation found at the renamed Upward Sun River site in the Tanana Valley in 2010. The reconstruction of the paleoenvironment will give the archeologist working in this region a better sense of the social and cultural adaptations that they are uncovering for this time period. In addition, the research is important because it will give a more complete picture of how the environment was changing during this critical period of human migration into North America.

Project Report

This dissertation project, by Co PI Joshua Reuther, focuses on three study areas in the middle Tanana Valley (mTV) to provide records of local terrestrial ecological contexts and environmental changes in lowland settings that date to the Late Glacial and early Holocene (16,000 to 6,000 years ago) in interior Alaska and Eastern Beringia (Alaska and unglaciated portions of the Northwest Territories and Yukon, Canada). The archaeological record of the mTV provides a rich history of hunter-gatherer land use dating over 14,000 years old, and includes several important archaeological sites such as the Upward Sun River Site, and the Broken Mammoth, Mead, Swan Point sites located in the Shaw Creek Flats area (Holmes 2011; Potter 2005; Potter et al. 2011; Yesner 2007). These studies also established that a rich diversity of faunal communities inhabited this region during the Late Glacial and early Holocene periods; some of which are extinct or do not coexist in the region today. It has been suggested that the mTV was an ecological refugium for late Pleistocene megafaunal species, such as mammoth and bison, as their habitats from the prior glacial period began to fragment during climatic amelioration (Guthrie 2006; Yesner 2007). This project is part of two larger projects focused on prehistoric human ecology and foraging behavior in Eastern Beringia: the Quartz Lake-Shaw Creek Flats Multidisciplinary and Upward Sun River Site Projects. The study areas are spread out across a 4,000 km2 area in the mTV and contain the presence of archaeological sites that have records of well-developed stratification of sediments and soils and preserved macrofossils. Two of the study areas are dune fields: the Little Delta Dunes (including the Upward Sun River Site) and Rosa-Keystone Dunes Fields (in the area of the Shaw Creek Flats); the third area is Quartz Lake, one of the largest lakes within the region. As a whole the study areas provide important information to understand the evolution of regional landscapes, paleoecological systems, and paleoenvironmental conditions dating back to 25,000 years ago, over 10,000 years prior to the currently accepted earliest human occupation of the region. Late Glacial and early Holocene landscapes of the mTV were ones of moderate stability and landscape disturbance with high rates of wind-blown (aeolian) sand and silt (loess) deposition, and the presence of early-to-middle successional vegetation communities (herbs and forbs, shrubs, and deciduous trees) that fostered the presence of diverse mammal communities that no longer coexist in the region. Loess deposition and sand dune activity during theses periods were crucial to maintaining early-to-middle successional vegetation communities throughout much of the mTV lowlands. The dynamic cycle of aeolian activity and weak soil development in the Late Glacial and early Holocene fostered positive feedbacks between cyclical disturbances and human and non-human systems (plants and animals). Fires also played a prominent role, at least in the Shaw Creek Flats and Rosa-Creek Dunes Field, in reactivating dunes. A cycle of fires, aeolian sand deposition, vegetative regrowth of shrubs and trees, weak soil development, and, again, fires occurred for over 2,000 years in the Shaw Creek Flats during this period. Mammal and bird communities were more diverse in the mTV lowlands during these cycles of vegetation-fire-aeolian aggradation-fire during the Late Glacial and early Holocene, in contrast to those of the middle Holocene (~6000 years ago). Late Glacial and early Holocene human populations were likely attracted to the mTV region because of the maintenance of higher mammal and bird biodiversity that was fostered by the presence of aeolian activity and natural fires which played a key role in maintaining early-to-middle successional vegetative communities throughout the Late Glacial and early Holocene. As the middle Holocene approached, landscapes became increasingly stable with the expansion of the boreal coniferous forests and aeolian deposition drastically decreased throughout the mTV. The disturbances that fostered the highly productive early-to-middle successional vegetative communities in the Late Glacial and early Holocene became progressively partitioned in the middle Holocene and primarily relegated to active floodplains. The establishment of the coniferous forests and increased paludification in the region during the middle Holocene (Bigelow 1997) segregated habitats of several mammal and bird species that depend on open grasslands and deciduous shrubs and trees (Guthrie 1990). A middle-to-late Holocene coniferous forest dominated landscape across the mTV likely provided less diversity and quantity of resources that hunter-gatherers relied upon in the Late Glacial and Early Holocene (Potter 2008; Yesner 2007).

National Science Foundation (NSF)
Division of Polar Programs (PLR)
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Anna Kerttula de Echave
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University of Arizona
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