Geologic Setting of the Maldives
Published:January 01, 2004
2004. "Geologic Setting of the Maldives", Seismic Expressions and Interpretation of Carbonate Sequences: The Maldives Platform, Equatorial Indian Ocean, Andrei V. Belopolsky, André W. Droxler
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The atolls of the Maldive archipelago form the central and largest part of the Chagos-Laccadive atoll chain in the equatorial Indian Ocean (Figure 1). The north-south-trending Chagos-Laccadive chain extends from the southwest coast of India to south of the equator and is composed of low-lying coral atolls. The Maldive archipelago consists of 22 large atolls whose sizes range from a few km to tens of km in diameter (Figure 1). The atolls are arranged in clusters separated by deep channels. The shapes of the atolls vary from circular to elongate in map view. Numerous smaller atolls called "faros" are commonly present within the lagoons of the large atolls and, in places, form the rims of the large atolls. The depth of the lagoons ranges from 31 m to 82 m (Purdy and Bertram, 1993) and tends to increase from north to south. Although the archipelago extends for 867 km from north to south, the island area is only 298 km2. Approximately 1200 individual islands exist, but only 200 of them are populated.
In the central part of the archipelago, the large atolls are arranged in two parallel north-south-trending chains separated by the Inner Sea (Figure 3). Several large drowned flat-topped banks — such as Fuad Bank between Horseburgh and Ari atolls, with its top submerged in 250 m of water — complete the "broken" segments of the double chain of atolls (Figure 3). The water depth of the Inner Sea ranges from 200 m to 500 m. The combined width of the platform (atolls and the Inner Sea) locally adds up to 130 km.
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Seismic Expressions and Interpretation of Carbonate Sequences: The Maldives Platform, Equatorial Indian Ocean
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.