PALEOENVIRONMENTS AND EVOLUTION OF THE UPPER MAASTRICHTIAN PLATFORM IN THE BETIC CONTINENTAL-MARGIN, SE SPAIN

In the Betic passive margin (SE Iberia) the latest Cretaceous (Late Ma astrichtian) was a period of great tectonic activity that resulted in the reactivation of major NE-SW trending listric faults. In this unsta ble setting, a narrow (tens of km wide) but long (hundred of kilometre s) mixed carbonate-siliciclastic platform developed over a ''middle'' Maastrichtian tectonically-induced unconformity. The environments deve loped in this platform and the changes they underwent during its evolu tion are interpreted and their facies and biotic associations describe d. These environments include: (1) the coastal lakes, which formed fre shwater to hyposaline, shallow lacustrine systems; (2) the tidal flats , developed in a narrow coastal area under conditions of low turbulenc e and high freshwater influence; (3) the lagoon, characterized by norm al marine salinity and by a variety of subenvironments, including radi olitid patches; (4) the platform edge, the dominant features of which developed under high-energy conditions, varying from mainly siliciclas tic shoals to carbonate reef complexes, depending on the terrigenous i nflux; (5) the mid platform, corresponding to the shallower areas belo w fair-weather wave base, in which the fossil assemblages are still do minated by benthic forms; and (6) the outer platform, characterized by hemipelagic sedimentation. The evolutionary history of the platform c omprises four main successive episodes: (1) Installation of a mixed ca rbonate-siliciclastic ramp, after an initial rapid transgressive event ; (2) Evolution of the mixed ramp into an incipient rimmed carbonate s helf, induced by the accretion of the edge of the platform during an a ggradational-progradational episode; (3) Interruption of the platform' s evolution by a regional tectonic event that caused a minor transgres sive pulse accompanied by a new arrival of abundant terrigenous materi al into the platform; (4) Reconstruction of the carbonate platform dur ing a second progradational-aggradational episode. The end of the plat form was controlled by the latest Maastrichtian regional tectonic even t that caused strong changes in the palaeogeography and in the basinal configuration.