Published:January 01, 1993
Figures & Tables
Carbonate Concepts from the Maldives, Indian Ocean
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.