SEQUENCE STRATIGRAPHY OF MIXED CARBONATE-SILICICLASTIC PLATFORMS DEVELOPED IN A TECTONICALLY ACTIVE SETTING, UPPER CRETACEOUS, BETIC CONTINENTAL-MARGIN (SPAIN)

The Late Cretaceous platforms in the Betic Continental Margin record a prolonged interval (30 m.y.) in which eustasy and tectonics operated simultaneously but with cell-differentiated frequencies, This resulted in development of two types of unconformity-bounded units: sequence s ets, which are tectonically controlled, and depositional sequences, wh ich are the result of variations in relative sea level. Unconformities bounding sequence sets are the result of tectonic episodes that induc ed great changes in basin geometry and basin subsidence, They operated without apparent rhythmicity at intervals ranging from 1 to 12 m.y. R egional tectonics was related to variations in the intraplate stress r egime associated with (1) the mid-Atlantic spreading, (2) the tectonic : regime in the Africa-Iberia boundary, still poorly documented, (3) t he opening of the Bay of Biscay between the Aptian and the early Campa nian, and (4) the oblique convergence between Iberia and Europe in the Pyrenees, which started in the early Campanian. During periods of rel ative tectonic quiescence eustasy and subsidence controlled developmen t of depositional sequences, These resulted from relative sea-level os cillations, most of them interpreted as third-order eustatic cycles, H owever, the correlation between our depositional sequences and the ''g lobal cycles'' of the Exxon chart is not always easy, mainly because s ubsidence can mask or enhance the eustatic signal.