Marine gateways play a critical role in the exchange of water, heat, salt and nutrients between oceans and seas. As a result, changes in gateway geometry can significantly alter both the pattern of global ocean circulation and associated heat transport and climate, as well as having a profound impact on local environmental conditions. Mediterranean-Atlantic marine corridors that pre-date the modern Gibraltar Strait, closed during the Late Miocene and are now exposed on land in northern Morocco and southern Spain. The restriction and closure of these Miocene connections resulted in extreme salinity fluctuations in the Mediterranean, leading to the precipitation of thick evaporites. This event is known as the Messinian Salinity Crisis (MSC). The evolution and closure of the Mediterranean-Atlantic gateways are a critical control on the MSC, but at present the location, geometry and age of these gateways is still highly controversial, as is the impact of changing Mediterranean outflow on Northern Hemisphere circulation. Here, we present a comprehensive overview of the evolution of the Late Miocene gateways and the nature of Mediterranean-Atlantic exchange as deduced from published studies focussed both on the sediments preserved within the fossil corridors and inferences that can be derived from data in the adjacent basins. We also consider the possible impact of evolving exchange on both the Mediterranean and global climate and highlight the main enduring challenges for reconstructing past Mediterranean-Atlantic exchange.
In the Eastern Prebetic Zone of SE Spain, upper Cretaceous to lower Eocene hemipelagic sequences deposited in the ancient southern passive continental margin of Iberia are we11 exposed. The long-term stratigraphy of these sequences is plUlctuated by six regional tectonic events, which induced rapid changes in palaeogeography and regional tectonics. Each event configured a new genetic scenario for sedimentation, which lasted lUltil the next tectonic reorganization and, in turn, contro11ed the deposition of an event bounded stratigraphic unit (EBSU). The ages of these events, determined chronobiostratigraphica11y, are: intra-Coniacian, late Santonian, "mid" Maas trichtian, latest Maastrichtian earliest Danian, late Thanetian and intra-Ypresian. All the events, but the first, are interpreted here as the result of contractional tectonic pulses, related to changes in intraplate stresses during the onset of African European convergence. Through correlations with both adjacent sha110w marine carbonates (prebetic platform) and basin pelagites (Subbetic), along with other basins of Iberia and North Africa, the long-term evolution of the continental margin is integrated within the geodynamic framework of the western Tethys.
This paper presents the first detailed biostratigraphic analysis of the uppermost Santonian through uppermost Maastrichtian hemipelagic carbonate successions of south-east Spain based mainly on the stratigraphic distributions of plank tic foraminifera. For the time interval studied, seven biozones of planktic foraminifera have been recognized. From oldest to youngest these are: the uppermost part of the Dicarinella asymetrica Zone, and the Globotruncanita elevata, Globotruncana ventricosa, Globotruncanita calcarata, Globotruncana falsostuarti, Gansserina gansseri and Abathomphalus mayaroensis zones. The biostratigraphic succession obtained from the sections studied in the Prebetic area is compared with those from sections in Tercis (France) and Kalaat Senan (Tunisia).
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