HR: 11:05h
AN: PP52B-04    [Abstracts]
TI: A 60,000-yr organic geochemical record of precipitation, temperature, and vegetation change in Southeast Tropical Africa
AU: * Tierney, J
EM: Jessica_Tierney@brown.edu
AF: Brown University Department of Geological Sciences, 324 Brook St. Box 1846, Providence, RI 02912, United States
AU: Russell, J
EM: James_Russell@brown.edu
AF: Brown University Department of Geological Sciences, 324 Brook St. Box 1846, Providence, RI 02912, United States
AU: Huang, Y
EM: Yongsong_Huang@brown.edu
AF: Brown University Department of Geological Sciences, 324 Brook St. Box 1846, Providence, RI 02912, United States
AU: Sinninghe Damste, J S
EM: damste@nioz.nl
AF: Royal Netherlands Institute for Sea Research, Department of Marine Biogeochemistry and Toxicology, P.O. Box 59 NL-1790 AB Den Burg, Den Burg, Texel, Netherlands
AU: Schouten, S
EM: schouten@nioz.nl
AF: Royal Netherlands Institute for Sea Research, Department of Marine Biogeochemistry and Toxicology, P.O. Box 59 NL-1790 AB Den Burg, Den Burg, Texel, Netherlands
AU: Hopmans, E C
EM: hopmans@nioz.nl
AF: Royal Netherlands Institute for Sea Research, Department of Marine Biogeochemistry and Toxicology, P.O. Box 59 NL-1790 AB Den Burg, Den Burg, Texel, Netherlands
AU: Cohen, A S
EM: acohen@geo.arizona.edu
AF: University of Arizona Department of Geosciences, 1040 E. 4th St., Tucson, AZ 85721, United States
AB: Tropical Africa - influenced by two major monsoon systems and a site of deep atmospheric convection - is a climatically important place. While a number of paleoclimate records illuminate the broad evolution of tropical African climate across the Holocene, very little is known about the nature of African climate during the last glacial period. Furthermore, most paleoclimate records from this region lack the resolution to discern millennial and centennial-scale climatic events. To improve our knowledge of Late Quaternary climate change in the Southeast African tropics, we present a high- resolution, 60,000-year organic geochemical record of climate history from the sediments of Lake Tanganyika. Eight meters of sediment were analyzed at 200-500 year resolution for compound-specific carbon and hydrogen isotopes of plant leaf waxes as well as TEX86 paleotemperature. In addition, we analyzed bulk organic carbon and nitrogen isotopes and opal concentrations at 50-100 year resolution to reconstruct lake productivity. Together, these proxies yield a wealth of information concerning tropical African climate. The organic geochemical proxies allow the reconstruction of tangible climatic variables: rain and heat. Since the isotopic composition of rainfall in East Africa is primarily controlled by the amount effect, the hydrogen isotopic composition of long-chain leaf waxes provides a powerful proxy for rainfall amount. In addition, the novel TEX86 paleotemperature proxy, which records the thermal history of the surface waters of Lake Tanganyika, is influenced primarily by variations in air temperature. All proxies indicate large and abrupt changes throughout the past 60,000 years, suggesting that East African climate is highly sensitive to global climatic change. More specifically, the hydrogen isotopes show large changes in precipitation concurrent with Northern high-latitude millennial scale climate changes such as the Younger Dryas and Heinrich Event 1, potentially highlighting the role that the Indian and African monsoon systems play in synchronizing high and low latitude climates. The TEX86 record shows large, rapid, 2-3˚C shifts in lake surface temperature during Marine Isotope Stages 1 and 3, and the carbon isotopic composition of leaf waxes suggests that East African vegetation also responds to climatic variability. The relationship between lake surface temperature and lake productivity (as indicated by organic carbon and opal concentrations) is not straightforward, suggesting that thermally-induced stratification is not the sole important factor controlling production in Lake Tanganyika. This novel record is a prime example of the invaluable paleoclimatic information that can be gathered utilizing organic geochemical methods, and highlights the interplay between high and low-latitude climate systems with respect to millennial-scale climate change.
DE: 1055 Organic and biogenic geochemistry
DE: 4870 Stable isotopes (0454, 1041)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4914 Continental climate records
DE: 4942 Limnology (0458, 1845, 4239)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting