Isolated carbonate platforms are abundant and widespread in Cenozoic strata and in the present-day oceans of Southeast Asia. The purposes of this article are (1) to describe the basic oceanographic setting of present-day Southeast Asia oceans; (2) to synthesize, compare, and contrast observations of the character of extant platforms in the context of fundamental oceanographic controls; and (3) to leverage these insights to develop a more complete understanding of older isolated platforms, especially the Miocene systems of Central Luconia. The data, presented to mimic an offshore-to-nearshore transect, illustrate Holocene platforms with a spectrum of sizes, depositional relief, facies abundances, and water depths. Although the first-order patterns of relief, size, and orientation are controlled by the geologic setting and Pleistocene history, the results demonstrate the influences of physical processes (waves, tides, currents), siliciclastic sediment, and chemical oceanography (nutrients, salinity, temperature) on the sedimentologic and geomorphic character of these platforms. Careful and critical application of these concepts to Central Luconia reservoirs in isolated carbonate platforms provides actualistic examples and process-response analogs. Although these perspectives offer understanding into controls on horizontal and vertical reservoir heterogeneities, they also emphasize that any one modern system can only be a partial analog for an ancient reservoir in an isolated carbonate platform.

Abstract Shallow-water carbonate sediments deposited in tropical and subtropical settings form thick and spatially extensive accumulations referred to as “carbonate platforms.” Carbonate platforms typically have life spans of millions of tens of milliions of years, and their birth, growth, and demise are governed by a combination of factors such as tectonics, eustasy, environmental conditions, and climate. Carbonate platforms contain an archive of variations of these factors through time in its sedimentary record. These changes can then be extracted from this record, providing insight into our understanding of sedimentary processes and enhancing our knowledge of earth’s history. This study examines the stratigraphy and evolution of the Maldives isolated carbonate platform, in the equatorial Indian Ocean. The Maldives platform is unique because of its enormous size (800 x 130 km). It is the second-largest modern isolated carbonate platform (after the Bahamas). Established in the early Eocene and now more than 3 km thick, the platform contains a sedimentary record which spans more than 50 million years. This study is based on interpretation of the regional 2-D seismic data set and data from one deep exploration well that resulted from Royal Dutch/Shell during its exploration campaign in 1989-1991. The excellent quality and the vast volume (6000km of seismic data) allowed the authors to conduct a detailed study of the Maldives platform.

Abstract A combination of ground truth, provided by a single exploration well, and geometries apparent on seismic lines, provides new insight on the geologic development of the Maldives. The single exploration well documents the occurrence of more than 2000 m of Tertiary carbonate rock overlying volcanic basement. Seismic lines demonstrate that the shallow water Paleogene part of the drilled section is generally horizontally bedded, whereas the overlying upper Oligocene-Miocene carbonates have a distinctly prograding pattern. Significantly, the prograding pattern is directed inward from the edges of the present platform rather than outward into the thousands of meters of Indian Ocean water depths. The punctuated lateral expansion of the carbonate platforms is therefore bilaterally opposing, i.e., away from either of the Indian Ocean edges of the platform and toward each other. The same opposing directions of expansion are apparent in Saya de Malha bank, where, unlike the Maldives, coalescence has been completed in the form of a large carbonate bank. In both cases, the opposing directions of progradation appear to be the result of a structural change in depositional architecture of the kind usually associated with the thermal contraction development of sag basins. Within this overall structural and stratigraphic framework, there is evidence that seismic stratigraphic relationships can vary considerably from atoll to atoll, indicating important local variations of the regional stratigraphy. A second significant depositional change resulted from the onset of Pliocene-Pleistocene glacial fluctuations in sea level.