Tectonic and environmental factors controlling on 1 the evolution of Oligo-Miocene shallow marine carbonate factories along a tropical SE Circum-Caribbean

Abstract

The evolution of the Cenozoic Circum-Caribbean shallow marine carbonate factories and ecosystems has been for long attributed to major global climatic and environmental changes. Although temporal variations in the Cenozoic shallow marine carbonate factories in this region seem to follow global trends, the potential effects of regional processes, such tectonic activity and local environmental change, on the evolution of the shallow marine carbonate factories are not well established. Here we present detailed sedimentologic and stratigraphic information from Middle Oligocene - Middle Miocene (Chattian-Burdigalian) shallow marine carbonate successions of the Siamana Formation in the Cocinetas Basin, located in the Guajira Peninsula, northern Colombia. We document the potential effects of regional tectonics and local environmental deterioration on the evolution of the Oligocene-Miocene tropical shallow marine carbonate factories along the SE Circum-Caribbean. Our results show that mixed heterozoan-photozoan biotic associations dominated the shallow marine carbonate factories during the Chattian, while purely photozoan biotic associations constituted the primary carbonate factory during the Aquitanian-Burdigalian transition. The Chattian mixed heterozoan/photozoan biotic association is associated with the development of mixed carbonate/siliciclastic shelves along which detached patchy reef areas occur. The onset of the Aquitanian-Burdigalian purely photozoan biotic associations parallels the increase in coral diversity as well as the occurrence of rimmed/detached carbonate platforms in the northern part of the basin. The development of the rimmed/detached platforms coincides with a time of increased basin subsidence and increased siliciclastic input along the southernmost part of the basin. A significant 127 change in the carbonate factory occurs in the Late Burdigalian, when purely heterozoan (rodalgal) biotic associations constituted the main shallow marine carbonate factory. This shift in the carbonate factory was favored by a major extensional component that resulted in subsidence and relative sea level rise along the Caribbean - South American margin. This extensional component is evidenced by the occurrence of normal faults that controlled the thickness and lateral extension of shallow marine rodalgal biostromes. The onset of the rodalgal biostromes, which elsewhere is associated with excellent carbonate reservoirs, also parallels the initiation of the Urumaco Trough and a further increase in silicilastic input toward the Cocinetas Basin. It also parallels a major tectonic reactivation along the Caribbean - South American plate boundary which resulted from the initial closure of the Panama Seaway