Pelagic carbonate platforms in the geologic record: their classification and sedimentary and paleotectonic evolution

Abstract

Drastic differences in thickness and abrupt lateral facies changes in synrift and postrift pelagic sequences usually indicate structural control over deposition. Outcrops in the Umbria-Marche Apennines provide new constraints for Jurassic paleogeographic reconstructions, allowing for the development of models for these depositional systems. The extensional regime and drowning history exert a major control over the PCP type and over the composition of sediment which fills inter-PCP basins. Given the very low rates of pelagic sedimentation the effects of faulting on submarine topography are drastic. Block tilting is of great importance, creating pelagic carbonate ramps that are the source area of most of the gravity flow deposits in half grabens. In horst-and-graben settings, on the other hand basins are sediment starved, and there are comparatively only minor gravity flows; mass transport there is mostly in the form of collapse of platform margins. -from Author