NEW PALEOGEOGRAPHIC AND LAKE-LEVEL RECONSTRUCTIONS OF LAKE TANGANYIKA- IMPLICATIONS FOR TECTONIC, CLIMATIC AND BIOLOGICAL EVOLUTION IN A RIFT LAKE

Palaeogeographic and lake-level reconstructions provide powerful tools for evaluating competing scenarios of biotic, climatic and geological evolution within a lake basin. Here we present new reconstructions fo r the northern Lake Tanganyika subbasins, based on reflection seismic, core and outcrop data. Reflection seismic radiocarbon method (RSRM) a ge estimates provide a chronological model for these reconstructions, against which yet to be obtained age dates based on core samples can b e compared. A complex history of hydrological connections and changes in shoreline configuration in northern Lake Tanganyika has resulted fr om a combination of volcanic doming, border fault evolution and climat ically induced lake-level fluctuations. The stratigraphic expression o f lake-level highstands and lowstands in Lake Tanganyika is predictabl e and cyclic (referred to here as Capart Cycles), but in a pattern tha t differs profoundly from the classic Van Houten cycles of some Newark Supergroup rift basins. This difference results from the extraordinar y topographic relief of the Western Rift lakes, coupled with the rapid ity of large-scale lake-level fluctuations. Major unconformity surface s associated with Lake Tanganyika lowstands may have corresponded with high-latitude glacial maxima throughout much of the mid- to late Plei stocene. Rocky shorelines along the eastern side of the present-day Ub wari Peninsula (Zaire) appear to have had a much more continuous exist ence as littoral rock habitats than similar areas along the north-west ern coastline of the lake (adjacent to the Uvira Border Fault System), which in turn are older than the rocky shorelines of the north-east c oast of Burundi. This model of palaeogeographic history will be of gre at help to biologists trying to clarify the evolution of endemic inver tebrates and fish in the northern basin of Lake Tanganyika.