Campanian-Maastrichtian evolution of sedimentary systems during the final stages of an epeiric sea —La Luna Sea— in eastern Colombia: Processes, spatio-temporal variability, and depositional controls

Abstract

Epeiric seas were widespread during the Cretaceous, associated with global sea-level rise. Their stratigraphic record, controlled mainly by eustasy, tectonic and climatic factors, resulted in the accumulation of important hydrocarbon source and reservoir rocks. In the NW of South America-Colombia, an epeiric sea established in the Early Cretaceous—knows as La Luna Sea in the Late Cretaceous—, bounded by a volcanic arc to the western side and by the Amazonian Craton to the east, was progressively filled during the Campanian-Maastrichtian, being these latest Cretaceous deposits important hydrocarbon reservoirs for conventional petroleum systems. In the Campanian-early Maastrichtian period the western side and the central part of the basin had a normal shoreface profile, dominated by pelagic and wave sedimentation processes, while a delta profile dominated by fluvial processes characterized the eastern side. During the late Maastrichtian, directly related to the accretion of western Caribbean terranes, transitional and continental environments dominated by fluvial processes were established on both sides of the basin, suggesting changes in geomorphological-topographic and drainage system characteristics of the emerged areas, leading to the filling of the epeiric basin. The distribution of the deposits was controlled by allogenic processes: tectonism associated with the growth of the proto-Central Cordillera, the global eustatic level, and in minor degree by autogenic processes such as channel avulsion, bottom and longshore currents, and high productivity events. These processes and their variable temporal and spatial influence were responsible for the different types of deposits on either side of the basin, which had a direct impact on the establishment of macrobenthic communities, also providing new exploration ideas related to the reservoirs. Comparisons suggest that the size of the receiving and emerged zones plays an important role in the distribution and arrangement of deposits along and across the basin, related to the nature of the internal processes involved in sediment redistribution.