A wet climatic terrestrial carbonate record in the middle-upper Pleistocene, north Tunisia
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ORIGINAL ARTICLE
A wet climatic terrestrial carbonate record in the middle‑upper Pleistocene, north Tunisia Ildefonso Armenteros1 · Naoufel Ghannem2 Received: 11 April 2020 / Accepted: 21 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The middle-upper Pleistocene Borj Edouane unit records a singular spectrum of terrestrial carbonates in a shallow depression on Cretaceous rocks in north Tunisia. This study aims to decipher the depositional system and reveal the climatic and paleohydrological conditions of the carbonate facies deposition. They are grouped into two facies associations: (1) a calcrete–palustrine and (2) a composite microbialite-travertine, surrounded by a marginal alluvial association along the western and northern borders of the basin. The calcrete–palustrine association extends along the westernmost south–north strip of the basin, reflecting calcrete development on distal alluvial fan deposits and pedogenic modification (palustrine facies) of shallow fresh-water carbonates. The composite microbialite-travertine, extending along north–south strips in the middle and eastern areas of the basin, consists of microbialite, clastic microbialite–travertine, and travertine associations. Microbialites were developed in fluvio-lacustrine environments within the central strip and pass eastward into the travertines through the clastic microbialite–travertine association. The latter was deposited from currents and in shallow ponds along a bench next to the travertine-depositing springs, linked to a fault system in the eastern margin of the basin. The carbonate depositional system shows an asymmetrical distribution of facies that parallels the paleohydrological asymmetry along the basin. Water supply was restricted in the western part of the basin and abundant in its eastern areas linked to spring waters that kept stable lake levels in the basin center, favoring the genesis of microbialites. The presence of lacustrine carbonates in the studied area indicates higher water availability during the Middle-Late Pleistocene and that climate in North Africa was wetter than today. Keywords Calcrete · Palustrine · Laminar crusts · Microbialites · Travertine · Paleoclimate
Introduction Terrestrial carbonates can form in different environmental conditions in continental basins. There is an exhaustive individualized treatment for each environment (Alonso-Zarza and Tanner 2010). Thereby, the calcrete and carbonate palustrine facies are extensively described in the literature for the Paleogene–Neogene time (Freytet and Plaziat 1982; Alonso-Zarza 2003). Fluvio-lacustrine carbonates dominated by microbialite facies show contrasting environmental significances with respect to calcretes and carbonate palustrine and laminar crusts. Their facies are found in fluvial * Ildefonso Armenteros [email protected] 1
Faculty of Sciences, Department of Geology, Salamanca University, 37071 Salamanca, Spain
Faculty of Science of Bizerte, University of Carthage, 7021 Zarzouna, Tunisia
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