Sedimentology and stratigraphy of the Miocene to Pliocene Mona Reef Complex and its relation with relative sea-level fluctuations

Abstract

The Miocene to Pliocene Mona Reef complex was investigated to define facies distribution, identify corals, describe strata geometries, and provide insights on porosity distribution. Two units were identified on the platform separated by a Late Miocene to Early Pliocene erosional unconformity: Unit I encompasses a Miocene coral reef framework and Unit II a Pliocene coral reef framework. The Miocene framework is characterized by platform facies that seems to be preferentially dolomitized and reef core facies that appear to be limestone. The Pliocene framework is characterized by reef core facies with less diagenetic alterations. The evolution of the Isla de Mona complex is subdivided in six stages characterized by episodes of deposition, subaerial exposure and uplift. Data from the visual porosity survey revealed porosity ranging between 2% and 35% in limestone and 7% and 25% in dolomites. The porosity in the platform commonly occurs as moldic, interparticle and intercrystalline porosity. Depositional textures and diagenetic overprinting control porosity heterogeneity. The Miocene to Pliocene Mona Reef complex exposed on Isla de Mona, Puerto Rico provides excellent outcrops for the study of facies distribution and porosity evolution in carbonate platforms. Heterogeneity of Neogene carbonate reservoirs is an important challenge for hydrocarbon exploration and production that requires an improvement of our understanding on the sedimentologic and diagenetic evolution of carbonate platforms.