BELOPOLSKY, ANDREI V., and ANDRE W. DROXLER
Rice University, Houston TX

Abstract: Oligocene and Miocene Sea Level Record: New Insights From the Maldives

Royal Dutch/Shell recently released to us a dense grid of seismic data from the Inner Sea of the Maldive Archipelago, central equatorial Indian Ocean. This data set provides a unique opportunity to improve the Oligocene and Miocene sea level record. During this period of time, the Maldives carbonate platform was subjected to minimal tectonic activity because of its location on the rigid part of the Indian plate away from the diffuse plate boundaries. The Maldive carbonate system consisted of two Oligocene/Miocene platforms separated by the Inner Sea basin. Because of this physiography, unusual for an intraoceanic carbonate system, platform to basin stratal geometries encapsulate past sea level fluctuations.

Our study focuses on the timing and amplitude of Oligocene sea level fluctuation, with a particular emphasis on testing the major "28.5 Ma" sea level fall of the Haq et. al. (1987) sea level chart. This event corresponds with an abrupt shift from middle neritic to coastal basinal sediments recovered from ARI-1 well drilled by Shell. On seismic sections, mid-Oligocene event is expressed by a high amplitude reflector, which can be correlated across the basin, and into the Oligocene carbonate platform.

In addition, we attempt to tie high resolution benthic d¹⁸O record with 4th order Miocene prograding sedimentary sequences with a particular emphasis on the sea level fluctuations during the middle Miocene. This interval is especially important since it is characterized by a systematic growth of the Antarctic ice sheet.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas