HR: 1340h
AN: U13B-1160    [Abstracts]
TI: A 75,000-year TEX86-based Temperature Record from Lake Malawi, East Africa
AU: * Woltering, M L
EM: wolte082@umn.edu
AF: Large Lakes Observatory and Department of Chemistry & Biochemistry, University of Minnesota Duluth, 10 University Dr, Duluth, mn 55812, United States
AU: Werne, J P
EM: jwerne@umn.edu
AF: Large Lakes Observatory and Department of Chemistry & Biochemistry, University of Minnesota Duluth, 10 University Dr, Duluth, mn 55812, United States
AU: Johnson, T C
EM: tcj@d.umn.edu
AF: Large Lakes Observatory and Department of Geological Sciences, University of Minnesota Duluth, 10 University Dr, Duluth, Mn 55812, United States
AU: Schouten, S
EM: schouten@nioz.nl
AF: Royal Netherlands Institute for Sea Research (NIOZ), Department of Marine Biogeochemistry and Toxicology, PO Box 59, Den Burg, Texel, 1790 AB, Netherlands
AU: Sinninghe Damste, J S
EM: damste@nioz.nl
AF: Royal Netherlands Institute for Sea Research (NIOZ), Department of Marine Biogeochemistry and Toxicology, PO Box 59, Den Burg, Texel, 1790 AB, Netherlands
AU: Sinninghe Damste, J S
EM: damste@nioz.nl
AF: .Department of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD, Netherlands
AB: We present a record of tropical paleotemperature from one of the few continental sites available to date, Lake Malawi. Using the TEX86 molecular paleotemperature proxy, we have extended the previous Lake Malawi temperature record from 23,000 to 75,000 years. The record, taken from hole 2a Site MAL05-2A drilled during the Lake Malawi Drilling Project in 2005, ends at around 75 ky bp at a near shore sand unconformity. TEX86 temperatures were generally stable between 26 and 27°C from 73 to 70 ky bp. This is followed by ~10 kyr of continuous cooling, during which temperatures dropped 5 - 6°C. This cold period reached its maximum at 60 ky bp, with temperatures as low as 20°C, 1-1.5°C colder than the LGM. Crenarchaeotal lipid abundance during this cold period is five times higher than anywhere else in record, but TOC and Si/Ti ratios do not suggest this to be a time of upwelling. The cooling observed correlates well with a decrease in December and January insolation over Lake Malawi. Following this cold period, we observe a short period of sudden warming with temperatures increasing by 3-4°C in only 300 years. After this, temperature variability in Lake Malawi does not seem to be driven by changes in insolation. Between 58 and 48 ky bp temperatures varied between 23.5 and 25°C. Stable temperatures, varying between 23 and 24°C, are observed from 48 to 21 ky bp. Sediment cores from the Indian Ocean show a similar temperature stability for this time period while temperature records from Antarctica and the equatorial Atlantic reveal a gradual decrease in temperature during this time. No temperature variations correlating with DO events were evident from our record.
DE: 1105 Quaternary geochronology
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1637 Regional climate change
DE: 1641 Sea level change (1222, 1225, 4556)
SC: Union [U]
MN: 2007 Fall Meeting