Browsing by Author "Horwitz, LK"

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    New chronology for the southern Kalahari Group sediments with implications for sediment-cycle dynamics and early hominin occupation
    (Cambridge University Press, 2017-01-20) Matmon, A; Hidy, AJ; Vainer, S; Crouvi, O; Fink, D; Erel, Y; ASTER Team; Arnold, M; Aumaître, G; Bourlès, D; Keddadouche, K; Horwitz, LK; Chazan, M
    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. Our data also establish the existence of a shallow early–middle Pleistocene water body that persisted for > 450 ka prior to this rapid period of deposition. Evidence from neighboring archeological excavations in southern Africa suggests an association of high-density hominin occupation with this water body. © University of Washington
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    New chronology for the southern Kalahari Group sediments: implications for sediment cycle dynamics and early hominin occupation
    (The Geological Society of America, 2014-10-19) Matmon, A; Hiny, AJ; Crouvi, O; Fink, D; Erel, Y; Arnold, M; Aumaître, G; Bourlès, D; Keddadouche, K; Horwitz, LK; Chazan, M
    The Kalahari Group covers an extensive part of the southern African continent and forms a low-relief landscape dominated by extensive unconsolidated sand. Current depositional models assume that the Kalahari Group sediments accumulated gradually throughout the Cenozoic, but an absence of absolute chronology beyond ~60 ka has left this premise untested. Here, we challenge this age model with new cosmogenic burial ages obtained from a 55 m section of Kalahari Group sediments at Mamatwan Mine near the southern edge of the Kalahari basin. Our results indicate that the majority of the existing section was emplaced rapidly at ~1 Ma. At this time the basin filled to its present level and established the Kalahari sand belts, which fostered the modern savannah. Our data suggest a dynamic landscape, with punctuated cycles of erosion and deposition, in contrast to the accepted concept of a stable basin filling slowly throughout the Cenozoic. The sedimentology and cosmogenic nuclide measurements from the lower Mamatwan Mine section reveal the existence of an extensive Early to Middle Pleistocene water body, persisting at least 420 ka prior to the rapid filling event at ~1 Ma. This water body is contemporaneous with a significant hominin occupation as evidenced by neighboring archaeological excavations. We thus provide the first evidence of association of the high-density hominin occupation in southern Africa with an extensive water body. © 2014 The Geological Society of America (GSA)