Sedimentary processes in the inter-cratonic Kalahari Basin

One of the world's largest intracratonic basins (covering altogether >10% of the continental crust) is the > 2.5 million km2 Kalahari Basin situated in the southern part of Africa. It is characterized by uplifted margins, terrestrial sedimentation within semi endorheic sub-basins, subdued morphology and climatic gradients. This intracratonic basin has been subjected to a prolonged period of subsidence affecting its sedimentary fill by plate motions and climatic cycles. Today, the surficial unconsolidated sand deposits of the Kalahari form the largest continuous sand body on earth. In this talk I will demonstrate the use of the Kalahari sedimentary fill to reconstruct tectonic and climatic processes. First, I will focus on three sites forming a north-south transect through the basin, where full sedimentary sequences where recovered. Chemical and isotopic analyses of the sediments were used to reconstruct depositional environments and paleo drainage systems and were linked to regional tectonic and climatic events. The chronostratigraphy of deposition was determined using cosmogenic nuclides dating techniques. These sedimentary successions display significant environmental and depositional variations throughout time and space, revealing dynamic sedimentation. Secondly, I will present a new data-based stochastic approach which integrates luminescence and cosmogenic nuclides data into a model, and reproduces sand-bodies migration and the time of sand introduction to the landscape. Applied in 8 localities across the Kalahari, model results suggest a main phase of sand introduction into the Kalahari, during and Pleistocene.  The obtained ages coincide with previous studies suggesting onset of arid conditions during the same time periods. Overall, results imply an early to mid-Pleistocene environment totally different than the arid one presently existing in the southern Kalahari.

 


תאריך 4/11/2018 10:30 12:00
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