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Climatic and hydrological instability in semi-arid equatorial East Africa during the late Glacial to Holocene transition:: A multi-proxy reconstruction of aquatic ecosystem response in northern Tanzania
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2007 (Swedish)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN ISSN: 0031-0182, Vol. 248, 440–458- p.Article in journal (Refereed) Published
Abstract [sv]

This paper reports new multi-proxy palaeoenvironmental data on the late Glacial-Holocene transition (c. 14.8–9.3 ka) in equatorial

East Africa, in the form of microfossil assemblages (chironomids, diatoms and ostracods) recovered from the sediment record of Lake

Emakat, Empakaai Crater, northern Tanzania. In the context of available palaeoclimatic and palaeoecological information from the

region and previously published fossil pollen and carbon and nitrogen isotopic data for the same sediment sequence, we here

reconstruct local lake-system response to regional climatic and hydrological instability during the period of post-glacial warming. The

aquatic biological proxy indicators suggest that the water level and chemistry of Lake Emakat evolved, first from a shallow freshwater

body at 14.8 ka to a deeper freshwater phase between c.14.4 and 10.3 ka and then to a markedly shallower, alkaline-saline environment

after c.10.3 ka. The lake appears to have been deepest between 13.2 and 12.0 ka, at a time of climatic drying when moist montane

forest vegetation within the lake's crater catchment was being replaced by open wood-and scrubland. Some palaeohydrological

changes reconstructed for Lake Emakat are in phase with lake evolution elsewhere in the region and thus apparently track broad-scale

climate changes, but some are not. Collectively these multi-proxy paleolimnological data indicate a complex adjustment of the local

aquatic ecosystem to temporal variations both in total annual effective precipitation and its seasonal distribution. The lake's

hydrological response was further conditioned by local factors, notably its geological and topographic setting.

Place, publisher, year, edition, pages
2007. Vol. 248, 440–458- p.
Keyword [en]
Climate change; Crater lake; Chironomids; Diatoms; East Africa; Empakaai; Multi-proxy reconstruction; Ostracods
National Category
Physical Geography
URN: urn:nbn:se:su:diva-21134OAI: diva2:187660
Available from: 2008-01-14 Created: 2008-01-14 Last updated: 2011-01-11Bibliographically approved

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Ryner, Maria
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