Siliciclastic control on carbonate platform evolution

Late Jurassic (Kimmeridgian) to Early Cretaceous (Valanginian) carbonate platforms in the western Atlantic exhibit both progradational and aggradational growth modes. Their development is reflected in seismic shelf edge and depositional facies geometries. These geometric relationships, together with paleotologic and diagenetic data, permit interpretation of the primary controlling factors on platform evolution. Atlantic platform growth and development during the Late Jurassic relative to rise in sea level vary directly with the siliciclastics. Carbonate platforms receiving siliciclastics prograde; those which do not, aggrade. This variation in platform evolution is found in equivalent-age platforms from other western Atlantic basins and as successive platform growth stages within the Baltimore Canyon basin. The switch from progradation to aggradation follows the termination of siliciclastics influx during flooding of an exposed platform. Platform height is maintained or decreases in the prograded stage but increases in the aggraded stage of platform growth associated with rising sea level. Aggraded platform growth demands progressively larger volumes of carbonate sediment as platform height increases. Progradation is thus limited by an increase in carbonates required for vertical platform growth. Siliciclastic filling of basins adjoining carbonate platforms has several important implications. First, siliciclastics may bypass active carbonate margins. Second, their volumetric contribution tomore » basin fill can be sufficiently large to allow progradation of platforms that are otherwise limited to aggradational growth by their sedimentary carbonate budget.« less