New palynological and sedimentological data obtained from the basal 3 m of core E96-2P from Lake Edward, Uganda-Congo record conditions wetter than present in the Edward basin from ∼11 000 to 6700 yr BP, in phase with other climate and vegetation records of northern hemispheric East Africa. Dominant pollen taxa include Celtis spp., Alchornea spp., Olea spp., and Moraceae indicating a moist semi-deciduous tropical forest. More xeric indicators such as Amaranthaceae and Asteraceae together with Poaceae comprise less than 5% of the pollen sum throughout this interval as compared with between 44 and 50% during a lake lowstand at ∼2000 cal yr BP and at the core top (near modern). The differences between these two assemblages suggest a ∼25 to 60% increase in annual precipitation during the early- to mid-Holocene as compared to modern (1500-2000 vs. 1200 mm/yr today). Early Holocene sediments in E96-2P are composed of laminated diatom oozes with moderately high total sulfur concentrations (2.8-4.7%) and no authigenic calcite, also indicative of conditions wetter than present. Between ∼9000 and 6700 yr BP, palynological and sedimentary proxies indicate sub-millennial-scale events related to changes in riverine discharge and runoff in the Edward basin. We attribute the variability in runoff, and hence precipitation, to Holocene variability in Indian or Atlantic Ocean SSTs or to shifts in the relative contribution of Indian and Atlantic moisture sources to the western Rift of equatorial Africa.
|Original language||English (US)|
|Number of pages||18|
|Journal||Journal of Paleolimnology|
|State||Published - Jul 2004|
Bibliographical noteFunding Information:
This research was supported by NSF-EAR 9706522 to Kristina Beuning and Kerry Kelts, NSF-ATM # 9805293 to Kerry Kelts and NSF-EAR 9421566 to Tom Johnson. J. Russell acknowledges the NSF Graduate Research Fellowship Program for salary support. We also wish to acknowledge Lauren Jankowic for her assistance in sulfur analysis as a University of Minnesota REU intern, and Yvonne Chan at the Large Lakes Observatory, Duluth, for biogenic silica analysis, and Linda Graham at the University of Wisconsin-Madison for assistance in identification of lacustrine algal remains. We appreciate the able assistance of the captain and crew of the R/V Topi and permission to conduct research on Lake Edward provided by the government of Uganda and Queen Elizabeth National Park. Tom Johnson, Dan Livingstone and one anonymous reviewer provided helpful comments of earlier drafts of this manuscript.
Copyright 2008 Elsevier B.V., All rights reserved.
- East Africa
- Lake Edward
- Old carbon
- Radiocarbon dating
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