The Late Ordovician glacio-eustatic record from a high-latitude storm-dominated shelf succession: The Bou Ingarf section (Anti-Atlas, Southern Morocco)

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: Loi, Alfredo, Ghienne, J.-F., Dabard, Marie-Pierre, Paris, Florentin, Botquelen, Arnaud, Christ, N., Elaouad-Debbaj, Z., Gorini, A., Vidal, Muriel, Videt, B., Destombes, J.
• Other Authors: Dipartimento di Scienze della Terra Cagliari, Università degli Studi di Cagliari = University of Cagliari (UniCa), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes (GR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre Armoricain de Recherches en Environnement-Centre National de la Recherche Scientifique (CNRS), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Ecole Nationale de l'Industrie Minérale (ENIM), Ecole Nationale de l'Industrie Minérale
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: Katian; Hirnantian; Sea-level; Forced regression; Ice sheet; Sequence stratigraphy; [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology; Ice Sheet
• Online Access: https://insu.hal.science/insu-00563940; https://doi.org/10.1016/j.palaeo.2010.01.018

International audience Evidences of glaciation at the end of the Ordovician are widespread in western Gondwana. Some authors consider the glaciation was restricted to the Hirnantian time, but occurrences of glacial deposits in the Lower Silurian strata of South America indicate that the Gondwana glaciers did not completely disappear after the Hirnantian glaciation. In addition, numerous studies based on palaeoecology, sedimentology, sequence stratigraphy and stable isotopes have suggested that ice sheets formed as soon as the Early/Middle Katian. The objective of this work is to investigate the high-frequency eustatic signals in a stratigraphic succession corresponding to the Katian and the Hirnantian (not, vert, similar 10 My comprising the uppermost part of the Ordovician). The studied section (Bou Ingarf section > 600 m) is located in the Central Anti-Atlas, southern Morocco. It shows an almost continuous succession of siliciclastic platform deposits. The lower package, Katian to early Hirnantian in age, corresponds to a shelf succession, within which storm dynamics prevailed. The upper package, middle to upper Hirnantian in age, comprises a glaciation-related succession made up of a suite of coastal to flood-dominated fluvio-glacial deposits. The latter have essentially filled in large palaeochannels interpreted as subglacial tunnel valleys. From high-resolution facies and sequential analysis, a curve of variation of depositional environments was established at very high, high and low frequencies. Time calibration was performed based on a high-quality biostratigraphic control mainly derived from chitinozoan biozones through the whole succession. Assuming a constant tectonic subsidence and a bathymetric model (shoreface/upper offshore boundary: 30 m; upper offshore/lower offshore boundary: 120 m), changes in facies-based water depths are converted into an eustatic sea-level curve using a one-dimensional backstripping procedure. The eustatic sea-level curve shows that the stratigraphic succession is ...