The oceanic anoxic event 2 at Es Souabaa (Tebessa,NE Algeria): bio-events and stable isotope study |
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Authors: | Sihem Salmi-Laouar Bruno Ferré Khoudair Chaabane Rabah Laouar Adrian J. Boyce Anthony E. Fallick |
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Affiliation: | 1.Département de Géologieoverall scope of tracing the various,Université Badji Mokhtar Annaba, Laboratoire de Recherche en Géologie (LRG),Annaba,Algeria;2.Dame du Lac 213,Sotteville-lès-Rouen,France;3.Département de Géologie,Université de Batna Hadj Lakhder,Batna,Algeria;4.Département de Géologie, Université Badji Mokhtar Annaba, B.P. 12, 23000 Annaba and Laboratoire de Géodynamique, Géologie de l’Ingénieur et Planétologie, USTHB,Algiers,Algeria;5.Isotope Geosciences Unit, S.U.E.R.C,Glasgow,UK |
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Abstract: | At the southern margin of the Tethys, the Es Souabaa area recorded traces of Oceanic Anoxic Event 2 (OAE2) around the Cenomanian-Turonian boundary (C/Tb). The dark, laminated, filament- and pyrite-bearing limestones represent the typical facies of this event. In terms of sedimentary environment, these features reflect a transgressive drowning that had induced hypoxia in these sedimentary environments. Such conditions favored the deposition and preservation of organic matter of marine origin, the distribution of which was controlled by paleogeography and halokinetic tectonics at that period. The OAE2 reached a climax between the last upper Cenomanian occurrence of Rotalipora cushmani and the lower Turonian occurrence of Whiteinella praehelvetica. Positive shift of the δ13C excursion along with relatively high total organic carbon (TOC) contents during OAE2 both indicate palaeo-environmental modifications enhanced by a significant change in primary marine productivity. Meanwhile, negative δ18O peaks in carbonates reflect increasing temperatures. Comparison of the data from this study with those from the neighboring Kalaat Senan section (Tunisia) suggests close similarities of events, although OAE2 is much more enhanced in Algeria. |
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