HR: 1340h
AN: PP13A-1484    [Abstracts]
TI: Tree-Ring Investigation of an in situ Younger Dryas-Age Spruce Forest in the Great Lakes Region of N. America
AU: * Panyushkina, I P
EM: panush@ltrr.arizona.edu
AF: Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721 United States
AU: Leavitt, S W
EM: sleavitt@u.arizona.edu
AF: Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721 United States
AU: Lange, T
PP13A-1484 AF: NSF AMS Facility, Dept. of Physics University of Arizona, Tucson, AZ 85721 United States
AU: Schneider, A F
PP13A-1484 AF: Department of Geology, University of Wisconsin-Parkside, Kenosha, WI 53141-2000 United States
AB: A late Pleistocene-early Holocene geological site known as Liverpool East on the southern end of Lake Michigan (in Indiana) was discovered in the early 1980s. Five previously reported radiocarbon dates on wood and peat from the deposit ranged from 9,080 to 11,290 ¹⁴C yr B.P., but our subsequent radiocarbon dating of wood from in situ spruce stumps at the site has yielded four ages from 10,060 to 10,444 ¹⁴C yr B.P., which correspond to calibrated calendar ages between about 11,550 and 12,500 Cal yr B.P. These dates place this forest squarely into the Younger Dryas event, and offer an unusual opportunity for exploring high-resolution environmental variability during an abrupt climate change event related to ocean thermohaline circulation. In the last 3 years, we have collected more than 130 pieces of wood from the site, about 65 of which are from stumps. Typical separation of trees was about 2-3 m, suggesting more of an open woodland than dense forest. The tilting of many stumps suggests the effect of wind on trees rooted in a soft peat substrate, and their tops broken at uniform height seem consistent with a subsequent rise in lake level, beach sand deposition, and ice floe event(s) that sheared off the upper trunks. Although these trees tend to be fairly young (typically 50-100 years old) and somewhat complacent, we developed a ring-width chronology to examine interannual variability. We are also measuring stable-oxygen and stable-carbon isotope ratios on α-cellulose in sequences of individual rings for several trees as additional environmental indicators of moisture and temperature. This collective set of tree-ring measurements and their statistics provide the basis for inferring the environment of this site, placed more precisely in time by "wiggle-matching" a sequence of 10-year radiocarbon measurements.
UR: http://www.ltrr.arizona.edu/~panush
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4914 Continental climate records
DE: 4920 Dendrochronology
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005