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Analysis of Carbonate Isolated Platform, Geometries and Facies Distribution of Pleistocene Carbonates in Bonaire, Southern Caribbean

Abstract

Bonaire is an isolated carbonate platform in the southern Caribbean, part of the Netherland Antilles. Its development is related to subduction of the Caribbean plate creating volcanism that occurred during the Late Cretaceous. The Cretaceous volcanic rocks form the basement of the carbonate island, is comprised of basalts, dacite, and andesite. Carbonate production began in the Miocene, and continues to this day. Through the Plio-Pleistocene, Bonaire has been influenced by uplift and sea level fluctuation, so terrace morphology is recognized in the islands of Aruba, Curacao and Bonaire. Platform geology starts with Eocene clastics, Miocene carbonates and Pleistocence carbonates. The Miocene carbonates can be found on the north side of the island contacting the volcanics. Pleistocene carbonates lie above Miocene and other volcanics, and compose the majority of the island when looking at it from map view. The objective of this study was to create a facies distribution model of the Pleistocene carbonates on Bonaire, and use it as a modern analogue to the petroleum reservoirs in Southeast Asia. To create this model, many different data types were used, including cores/hand samples for descriptions, as well as Digital Elevation Models, ground-based LiDAR, and shallow-seismic. The terraces of Bonaire are formed of boundstones (from the corals Diploria sp. and Acropora sp.) and bioclastic grainstone. There is a higher concentration of boundstone on the windward (east) side of the island, and more grainstone on the leeward (west) side of the island. The eolianites that make up Seru Largu also show high-angle cross-bedding to west. This gives evidence that the wind currents today are similar to what they were during the deposition of Bonaire's Pleistocene carbonates. The two outcrops focused in this study include Seru Grandi and Seru Largu. Seru Grandi is located on the northern coast of Bonaire. It is approximately 0.17 sq. km, 8 meters thick, and contains a bed of dolomite overlain by a boundstone-grainstone bed. The boundstone-grainstone bed thins as it moves landward, pinching out over the dolomite. Seru Largu, located in the center of Bonaire, is a mound of fine-grained, well-sorted eolianites elongated in the E-W direction. These deposits are extended of about 0.26 sq. km, with an average thickness of 17.5 m.