Geological Society of America

T281 Quantifying Geomorphic Processes and Rates of Landscape Evolution I

Wednesday, 28 September 2016
8:00 AM - 12:00 PM
Room 405

NEW CHRONOLOGY FOR THE SOUTHERN KALAHARI GROUP SEDIMENTS WITH IMPLICATIONS FOR SEDIMENT-CYCLE DYNAMICS

Paper number: T281-6
Program: Technical Sessions
Time: 9:15 AM – 9:30 AM

Authors

Ari Matmon Presenting Author
The Hebrew University of Jerusalem, Jerusalem
Alan J. Hidy
Lawrence Livermore National Laboratory, Livermore, CA
Shlomy Vainer
Hebrew University, Jerusalem, N/A
Onn Crouvi
Jerusalem
David Fink
AMS-ANTARESANSTO, Sydney, NSW
Yigal Erel
Hebrew University, Jerusalem
Team ASTER
CNRS-Aix-Marseille University, Aix en Provence
Liora K. Horwitz
Hebrew University, Jerusalem, N/A
Michael Chazan
University of Toronto, Toronto, ON

Abstract

Kalahari Group sediments accumulated in the Kalahari basin, which started forming during the breakup of Gondwana in the early Cretaceous. These sediments cover an extensive part of southern Africa and form a low-relief landscape. Current models assume that the Kalahari Group accumulated throughout the entire Cenozoic. However, chronology has been restricted to early-middle Cenozoic biostratigraphic correlations and to OSL dating of only the past ~300 ka. We present a new chronological framework that reveals a dynamic nature of sedimentation in the southern Kalahari. Cosmogenic burial ages obtained from a 55 m section of Kalahari Group sediments from the Mamatwan Mine, southern Kalahari, indicate that the majority of deposition at this location occurred rapidly at 1–1.2 Ma. This Pleistocene sequence overlies the Archaean basement, forming a significant hiatus that permits the possibility of many Phanerozoic cycles of deposition and erosion no longer preserved in the sedimentary record. Calcretes that cement conglomerates and sands throughout the sequence are dated with U-series to range between 300-500 ka, much younger than previously assumed. Our data also establish

the existence of a shallow water body that persisted for >450 ka prior to this rapid period of deposition and is associated with early-middle Pleistocene high-density hominin occupation.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-279026

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