GEOMETRY, PALEOENVIRONMENTS AND RELATIVE SEA-LEVEL (ACCOMMODATION SPACE) CHANGES IN THE MESSINIAN MURDJADJO CARBONATE PLATFORM (ORAN, WESTERN ALGERIA) - CONSEQUENCES

The Messinian carbonate platform of the Djebel Murdjadjo (western Algeria) is composed of six sedimentary units arranged in generally aggradational-progradational sequences commencing at the major Tortono-Messinian transgression and terminating at the onset of the ''Salinity Crisis''. Palinspastic reconstruction, combined with microfacies analysis, has allowed recognition of inner platform to outer platform environments and provides a new interpretation for platform building with respect to relative sea-level (accommodation space) changes. Following the deposition of the bioclastic limestones of the first transgressive unit, the upper red-algae limestones, a reef-complex and a part of the ''Terminal Complex'' were successively deposited during stillstands. These three episodes were each separated by decametre-amplitude rises in relative sea-level (accommodation space). No major sea-level drop appears to have been associated with the deposition of Messinian evaporites.