THE DEVELOPMENT OF TEX86 FOR CONTINENTAL PALEOTEMPERATURE CONSTRUCTION

POWERS, Lindsay A.¹, WERNE, Josef P.², JOHNSON, Thomas C.³, HOPMANS, Ellen C.⁴, SINNINGHE DAMSTÉ, Jaap S.⁵ and SCHOUTEN, Stefan⁵, (1)Large Lakes Observatory, Univ of Minnesota Duluth, 2205 E. 5th St, Duluth, MN 55812, (2)Large Lakes Observatory and Dept. of Chemistry, Univ of Minnesota Duluth, 10 University Dr, Duluth, MN 55812, (3)Large Lakes Observatory and Department of Geological Sciences, Univ of Minnesota Duluth, Duluth, MN 55812, (4)Marine Biogeochemistry & Toxicology, Royal Netherlands Institute for Sea Rsch, PO Box 59, Den Burg, 1790 AB, Netherlands, (5)Marine Biogeochemistry and Toxicology, Netherlands Institute for Sea Rsch, PO BOX 59, Den Burg, Texel, 1790 AB, Netherlands, jwerne@d.umn.edu

We have developed a calibration for the new TEX86 paleotemperature proxy from a climatically diverse suite of globally distributed lacustrine systems. The results of this calibration show a strong linear relationship (r2= 0.96) between TEX86 values and published mean annual lake surface temperatures. The TEX86 index as it currently stands appears to work only in large volume lakes, which are typically the best integrators of regional climate variability. The marine crenarchaeota responsible for producing the tetraether membrane lipids used in the TEX86 index do not appear to be ubiquitous in lakes as previously thought, or are not in great enough abundance to be detected in the sediments of some, especially small, lakes. In contrast to the aquatically derived tetraether lipids, we have found terrestrial tetraether lipids in all lacustrine sediments analyzed thus far. The terrestrial tetraethers are primarily produced by soil bacteria and some methanogenic archaea. In very few cases the presence of terrestrial tetraethers, co-occurring with the aquatic tetraethers, confuse the TEX86 signal and predict a colder than normal temperature. As a demonstration of the potential of this molecular paleotemperature proxy, we present a set of paleotemperature records derived from the application of TEX86 to sediment cores from Lake Malawi, East Africa through the LGM. We find a ~4 ºC overall warming since the LGM, with temperature reversals of more than 2 ºC during the Younger Dryas (12.5 ka BP) and in the early Holocene. The warmest Holocene temperatures in this part of Africa appear to have occurred around 5000 years ago. The onset of warming in the Lake Malawi basin coincides with the BYRD oxygen isotope record of warming in Antarctica. While the range of temperatures observed in this study is not surprising, the timing of post-glacial warming, the thermal response to the YD, and the Holocene history of warming and cooling trends are providing important new insights into tropical climate dynamics on centennial to millennial scales.

Session No. 4

S4. Lakes—Glacial Lakes, Large Lakes, Small Lakes, Groundwater Interaction I

Thursday, 19 May 2005: 8:00 AM-12:00 PM

Geological Society of America Abstracts with Programs. Vol. 37, No. 5, p.8

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North-Central Section - 39th Annual Meeting (May 19–20, 2005)

THE DEVELOPMENT OF TEX86 FOR CONTINENTAL PALEOTEMPERATURE CONSTRUCTION