Seismic Expressions of Prograding Carbonate Bank Margins: Middle Miocene, Maldives, Indian Ocean
Andrei V. Belopolsky, André W. Droxler, 2004. "Seismic Expressions of Prograding Carbonate Bank Margins: Middle Miocene, Maldives, Indian Ocean", Seismic Imaging of Carbonate Reservoirs and Systems, Gregor P. Eberli, Jose Luis Masaferro, J. F. “Rick” Sarg
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Carbonate bank margins in the Maldives, a large isolated carbonate platform in the equatorial Indian Ocean, prograded significantly in the middle Miocene. The interpretation of a dense grid of two-dimensional seismic data located pro-grading margins and imaged the internal architecture of the prograding sequences in detail. Three individual prograding bank margins were positioned tens of kilometers away from each other. The margins prograded from both east and west toward the central seaway. Each prograding complex consists of five depositional sequences bounded by unconformities and correlative conformities. Seismic correlation shows that the deposition of sequences in individual prograding complexes was synchronous and driven by a mechanism of regional scale.
One prograding complex, complex I, is examined in detail in three dimensions on a set of seismic lines. Each prograding sequence is subdivided into two packages: strong-and weak-amplitude reflection packages. Strong-amplitude reflection packages consistently display a basinward shift in onlap and/or downstepping and are interpreted as having formed during falling relative sea level. Weak-amplitude reflection packages are interpreted as having formed during the rise and highstand of relative sea level. Each sequence thus represents a complete sea level cycle. The terminal middle Miocene sequence is characterized by voluminous downslope deposition of sediments interpreted as gravity-flow deposits. This regional event is interpreted as a response to a significant sea level fall at the end of the middle Miocene.