Paleooceanography of the Mesogean sea based on ostracods of the northern Tunisian continental shelf between the late Cretaceous and early paleogene

Abstract

A new method analysis used in the study of the El Kef Section (north-western Tunisia) led to the paleooceanographic reconstruction of the Mesogean between-late Cretaceous and early Paleogene. Several changes observed are, in fact, worthy of particular mention: paleobathymetrically the area changed from an upper bathyal environment of about 400 m deep to an outer shelf domain of 100-50 m. Furthermore, the Oxygen Minimum Zone (O.M.Z.) became highly intense at (a) the Cretaceous-Tertiary transition (catastrophic event); (b) the P1-P2 boundary (intense thermic stratification); and (c) between P4 and P6 (very active paleoproductivity). In this last episode the continental shelf environment was subjected to intense upwelling responsible for the formation of a »prephosphatic« environment at water/sediment interface. The paleooceanographic history of phosphates in the Gafsa-Metlaoui basin is, in fact, in perfect stratigraphic and paleoenvironmental agreement with the paleobathymetric evolution of the Kef region. Finally, paleooceanographic communication between the Mesogean and the North Atlantic was, at this period, highly free because of lack of hydrologic relations between the North Atlantic and the Norwegian Sea.