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חברי כבוד של החברה הגיאולוגית
חברי כבוד של החברה הגיאולוגית
חברי כבוד של החברה הגיאולוגית
Geochemical recycling of Kalahari duricrusts with implications for the cratonic long-term resilience
Shlomy Vainer1,2, Ari Matmon3, Alan Hidy4, Mike de Wit5, Valérie Chavagnac6, ASTER Team7, Claudia Baumgartner8, Torsten W. Vennemann1, Eric P. Verrecchia1,9
(1) Department of Earth and Environmental Sciences, Ben Gurion University of the Negev, Beer Sheva 84105
(2) Other Institute (insert manually)
(3) The Fredy and Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Israel
(4) Other Institute (insert manually)
(5) Other Institute (insert manually)
Other Institute (insert manually)
Other Institute (insert manually)
Other Institute (insert manually)
Other Institute (insert manually)
Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland; Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA; Department of Earth Sciences, University of Stellenbosch, Stellenbosch, South Africa; Géosciences Environnement Toulouse, CNRS UMR 5563 (CNRS/UPS/IRD/CNES), Université de Toulouse, Toulouse, France; Aix Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France; Institute of Earth Sciences, University of Lausanne, Lausanne, Switzerland; Botswana International University of Science and Technology, Department of Mining & Geological Engineering, Palapye, Botswana
Continental duricrusts are a defining component of cratonic landscapes, yet their modes of formation and long-term evolution remain debated. This study examines duricrust development in the Kalahari Basin (southern Africa), using high-resolution petrographic, geochemical, and geochronological analyses to test competing formation models and to constrain the evolution of the African erosional surface in the Kalahari.
Duricrusts from contrasting structural settings across the Okavango Rift Zone record diagenetic spectrum from open meteoric precipitation to strongly evaporitic conditions. In the elevated northern block, carbonate duricrusts formed under open hydrological conditions, reflecting meteoric inputs and active fluid exchange. In contrast, duricrusts from the uplifted southern block preserve signatures of closed-basin, hypersaline environments, followed by rapid mineral replacement during more humid phases. These transitions record repeated dissolution, reprecipitation, and mineral transformation rather than single-stage formation.
Cosmogenic nuclide ages indicate episodic duricrust development separated by major unconformities that coincide with regional tectonic reorganization, demonstrating strong diachroneity of surface evolution within the basin. Together, the data show that neither in-situ laterization nor purely transported-solute models adequately explain intracratonic duricrust formation.
Instead, the Kalahari illustrates a dynamic system in which weathering on structural highs supplies solutes that precipitate in adjacent basins, above and underground. These are repeatedly reworked during climatic shifts and progressively harden into erosion-resistant caps. This ongoing diagenetic recycling maintains chemical reactivity within landscapes that appear geomorphically stable, highlighting cratonic resilience through duricrust armoring as an active process.