REGIONAL EFFECT ON OLIGOCENE-MIOCENE SHALLOW MARINE CARBONATE ALONG THE SE CIRCUM - CARIBBEAN

Continuous and well-exposed shallow marine carbonate successions from the Siamana Formation, Cocinestas Basin, Alta Guajira, Northern Colombia, provides a unique opportunity to understanding how Cenozoic equatorial carbonate factories respond to global environmental changes, sea level fluctuation and regional tectonics. Here we present results from multiple proxies, i.e. standard petrographic analysis, elemental analysis and stable isotope carbon and oxygen analysis, used to better constrain the paragenetic history of the Siamana Formation carbonate factory. Our results show a change from a Late Oligocene mixed heterozoan-photozoan (benthic forams and corals) carbonate factory in to a photozoan-coral dominated carbonate factory in the Early Miocene. A change from coral to redagal dominated carbonate factory occurs in the late Early Miocene, which lead to the demise of the carbonate factory in the Middle Miocene

The petrographic analyses show that the basin was under the influence of detrital inputs and reveal rapid and significant compaction of the carbonate grains, with little or no paucity of marine cementation and some localized dolomitization. Meanwhile, the δ¹³C values of the carbonates range from (−1.7‰ to −8.27‰) while the δ¹⁸O values range from (-1.9‰ to -6.25‰). Variations in the isotope signatures show no facies dependence. The isotopic values are consistent with progressive burial diagenesis enhanced by basin subsidence. Together, the stratigraphic, petrographic and isotopic analyses suggest the influence of active tectonics on the evolution of the shallow ,marine carbonate factory. Similar responses have been identified in Cenozoic tropical carbonates deposits in SE Asia.