Paleolimnology of Lake Tanganyika, East Africa, over the past 100 kyr

Authors: Scholz C.A.¹; King J.W.²; Ellis G.S.³; Swart P.K.³; Stager J.C.⁴; Colman S.M.⁵

Source: Journal of Paleolimnology, Volume 30, Number 2, August 2003 , pp. 139-150(12)

Publisher: Springer

Abstract:

New sediment core data from a unique slow-sedimentation rate site in Lake Tanganyika contain a much longer and continuous record of limnological response to climate change than have been previously observed in equatorial regions of central Africa. The new core site was first located through an extensive seismic reflection survey over the Kavala Island Ridge (KIR), a sedimented basement high that separates the Kigoma and Kalemie Basins in Lake Tanganyika.

Proxy analyses of paleoclimate response carried out on core T97-52V include paleomagnetic and index properties, TOC and isotopic analyses of organic carbon, and diatom and biogenic silica analyses. A robust age model based on 11 radiocarbon (AMS) dates indicates a linear, continuous sedimentation rate nearly an order of magnitude slower here compared to other core sites around the lake. This age model indicates continuous sedimentation over the past 79 k yr, and a basal age in excess of 100 k yr.

The results of the proxy analyses for the past 20 k yr are comparable to previous studies focused on that interval in Lake Tanganyika, and show that the lake was about 350 m lower than present at the Last Glacial Maximum (LGM). Repetitive peaks in TOC and corresponding drops in ¹³C over the past 79 k yr indicate periods of high productivity and mixing above the T97-52V core site, probably due to cooler and perhaps windier conditions. From 80 through 58 k yr the ¹³C values are relatively negative (-26 to -28 l) suggesting predominance of algal contributions to bottom sediments at this site during this time. Following this interval there is a shift to higher values of ¹³C, indicating a possible shift to C-4 pathway-dominated grassland-type vegetation in the catchment, and indicating cooler, dryer conditions from 55 k yr through the LGM. Two seismic sequence boundaries are observed at shallow stratigraphic levels in the seismic reflection data, and the upper boundary correlates to a major discontinuity near the base of T97-52V. We interpret these discontinuities to reflect major, prolonged drops in lake level below the core site (393 m), with the lower boundary correlating to marine oxygen isotope Stage 6. This suggests that the previous glacial period was considerably cooler and more arid in the equatorial tropics than was the last glacial period.

Keywords: Lake Tanganyika; East Africa; Paleolimnology; Paleoclimatology

Language: English

Document Type: Research article

Affiliations: 1: Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA E-mail: cascholz@syr.edu 2: Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA 3: Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida 33149, USA 4: Paul Smiths College, Paul Smiths, New York 12970, USA 5: U.S. Geological Survey, Woods Hole, MA 02543, USA

Publication date: 2003-08-01

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• In this Subject: Geology
• By this author: Scholz C.A. ;  King J.W. ;  Ellis G.S. ;  Swart P.K. ;  Stager J.C. ;  Colman S.M.

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