Tuesday, October 09, 2007

African mega-drought?   posted by Razib @ 10/09/2007 02:02:00 PM

Ecological consequences of early Late Pleistocene megadroughts in tropical Africa:
Extremely arid conditions in tropical Africa occurred in several discrete episodes between 135 and 90 ka...Fossil and sedimentological data show that Lake Malawi itself, currently 706 m deep, was reduced to an ~125 m deep saline, alkaline, well mixed lake. This episode of aridity was far more extreme than any experienced in the Afrotropics during the Last Glacial Maximum (~35-15 ka). Aridity diminished after 95 ka, lake levels rose erratically, and salinity/alkalinity declined, reaching near-modern conditions after 60 ka. This record of lake levels and changing limnological conditions provides a framework for interpreting the evolution of the Lake Malawi fish and invertebrate species flocks. Moreover, this record, coupled with other regional records of early Late Pleistocene aridity, places new constraints on models of Afrotropical biogeographic refugia and early modern human population expansion into and out of tropical Africa.