HR: 1340h
AN: PP43B-1279    [Abstracts]
TI: A Quantitative, High-resolution Hydrologic and Temperature Record From the Northern Great Plains, USA
AU: * Toney, J L
EM: jaime_toney@brown.edu
AF: Brown University, Geological Sciences 324 Brook St - Box 1846, Providence, RI 02912, United States
AU: Fritz, S C
EM: sfritz2@unl.edu
AF: University of Nebraska, 1100 N 17th St, Lincoln, NE 68588, United States
AU: Baker, P A
EM: pbaker@duke.edu
AF: Duke University, 301 Old Chemistry Box 90227, Durham, NC 27708, United States
AU: Grimm, E
EM: grimm@museum.state.il.us
AF: Illinois State Museum, ISM Research & Collections Center 1011 East Ash Street, Springfield, IL 62703, United States
AU: Huang, Y
EM: yongsong_huang@brown.edu
AF: Brown University, Geological Sciences 324 Brook St - Box 1846, Providence, RI 02912, United States
AB: The use of alkenone unsaturation ratios to reconstruct quantitative temperature records from marine sediments is well-established, while the application of this geochemical indicator is relatively new for lakes in continental settings. Here we present the first continuous, high-resolution, Holocene-length alkenone record from the North American interior, Brush Lake, MT, to quantitatively assess temperature changes from the late glacial through the Holocene (with particular emphasis on mid-Holocene maximum aridity period). We couple the alkenone analyses with measurements of the isotopic composition of short and long-chain fatty acids and other bulk geochemical measurements to reconstruct patterns of regional drought. Alkenone concentrations are generally low, but measurable, and we have generated a preliminary temperature reconstruction using a published alkenone calibration from German lakes (Zink et al. 2001). Associated with alkenone-inferred changes in temperature are shifts in the isotopic composition of leaf waxes, as well as changes in the ratio of short to long- chain acids suggestive of variability in aquatic versus terrestrial input of organic matter to the lake environment. This paleoclimate record is part of a multiproxy project to improve our understanding of the long-terms patterns of drought in central North America and the mechanism that causes drought in the Northern Great Plains. The analysis of alkenone unsaturation ratios coupled with isotope data derived from terrestrial leaf waxes has the potential to yield quantitative and independent analysis of the temperature and hydrologic drivers of drought. This study may also provide insight into the cyclic nature of drought in the Northern Great Plains and the relationship to N Atlantic and tropical Pacific SST changes, which are known to force drought in the instrumental period.
DE: 1055 Organic and biogenic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting