Geological Society of America

T227 North Pacific Environment and Paleoclimate from the Late Pleistocene to Present II

Tuesday, 24 October 2017
1:30 PM - 5:30 PM
Room 609

LATE GLACIAL AND HOLOCENE LANDSCAPE CHANGE IN THE MIDDLE SUSITNA VALLEY, ALASKA

Paper number: T227-10
Program: Technical Sessions
Time: 3:50 PM – 4:05 PM

Authors

Nancy Bigelow Presenting Author
University of Alaska Fairbanks, Fairbanks, AK
Joshua D. Reuther
University of Alaska Museum of the North, Fairbanks, AK
Matthew Wooller
University of Alaska Fairbanks, Fairbanks, AK
Emilie Saulnier-Talbot
University of Alaska Fairbanks, Fairbanks, AK
Katherine Mulliken
Hawaiian Volcano Observatory, Hilo, HI
Kristi L. Wallace
U.S. Geological Survey, Anchorage, AK

Abstract

The ca. 450 km-long Susitna River of central Alaska extends from the Alaska Range massif to tidewater. 100s of archaeological sites, including some of the oldest sites south of the Alaska Range, are a testament to its importance for people for the past 10,000 yrs. We present here multi-proxy analyses (sediment geochemistry, diatoms, and pollen) of four lakes forming a transect from the tundra to the boreal forest and which span between >12 kyr BP and the present (all ages are calibrated). Key results are:

1) Deglaciation at least before 12 kyr BP and probably several millennia earlier (which is earlier than previous research suggested). By ca. 13 kyr BP, lakes were deep and productive, with a birch shrub tundra growing in the region.

2) Possible Younger Dryas climate change (ca. 11-11.8 kyr BP) with diatom-inferred lake level drop, reduced lake productivity, and reduced shrubs.

3) Early to middle Holocene climatic amelioration with tree expansion (cottonwood, followed by spruce) and deep, productive lakes.

4) Middle to late Holocene climatic deterioration with reduced trees (spruce) and shallower, less productive lakes.

5) A number of tephra horizons are present in the lake cores, some of which are newly identified. In addition, all four lakes contain the prominent Watana tephra at ca. 4 kyr BP, which reduced lake productivity and probably affected the vegetation.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-297481

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