Tropical East African climate change and its relation to global climate: A record from Lake Tanganyika, Tropical East Africa, over the past 90+ kyr

Forcing mechanisms of tropical climate in continental areas remain poorly understood, due in large part to a lack of continuous, long-term, high-fidelity records. Sediment core T97-52V from Lake Tanganyika provides new insight into the timing and mechanisms behind East African climate change over the past 90+ kyr. This record is particularly important, because, other than a recently recovered scientific drill core from Lake Malawi, there are no other continuous, well-dated records from East Africa prior to 60 ka. The high resolution age model presented here provides a large degree of age certainty for the past 45+ kyr, and our suite of proxies allows a thorough examination of Lake Tanganyika's dynamics. From core stratigraphy and chemical analyses, we present evidence of a lake level drop greater than 400 m sometime prior to 90 ka, much greater than that inferred for the LGM, suggesting a period of intense aridity sometime around 100 ka. Additionally, core T97-52 V preserves evidence of worm burrows detected by X-radiographic imagery as indicated by burrow-shaped deposits of iron oxide, indicating a shallow lake at the time of deposition of that material. Intermittently high lake levels between 78 ka and 72 ka developed at the same time as a weakened Asian monsoon and a pluvial phase in Northeast Brazil, suggesting a global reorganization of climate, possibly forced by a reduction in orbital eccentricity. Over the past 60 ka this core preserves the same events recorded in a core collected 100 km away in the southern basin of Lake Tanganyika, including an unexplained increase in biogenic silica at 37 ka, suggesting that this vast lake is responding coherently across both major bathymetric basins to regional and global climate forcing. (C) 2010 Elsevier B.V. All rights reserved.