Paleolimnological records of environmental change preserved in paleo-lake mababe, Northwest Botswana

Abstract

Lacustrine sediments preserve a record of environmental change from climate shifts and landscape evolution. Paleo-lake Mababe in northwest Botswana was investigated to determine how the effects of tectonics along the incipient Okavango Rift, as well as local and regional climatic changes are recorded in lake sediments. This multi-proxy study using grain size distribution, magnetic susceptibility, organic and inorganic carbon content, and metal data revealed a major shift in hydrology and sedimentation. The shift is due to tectonic activity associated with movement along faults that diverted river flow away from the Mababe Depression. Sediments deposited prior to tectonic activity show evidence of local and regional climate. Post-tectonic sedimentation revealed local and regional climatic shifts and the new hydrologic regime established by neotectonics. Major reorganization of regional hydrology resulting from tectonic activity in the Okavango rift zone affected sedimentation in lakes in the middle Kalahari in northwest Botswana.