The Volcanic Basement of the Maldives
2004. "The Volcanic Basement 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 nature and age of the Maldive basement are based on material recovered at ODP Site 715 and the two industry exploration wells, NMA-1 and ARI-1. Site 715, on the eastern oceanward slope of the Maldivian archipelago (Figure 3), recovered 76.6 m of basalt lava flows. Three limestone units with basalt clasts were interbedded with the basalt lava flows in the upper part of the section. The upper parts of the individual basalt flows were weathered and oxidized; these have been interpreted as lava flows erupted under subaerial conditions (Backman et al., 1988). With 40Ar/39Ar dating, these basalts yielded an age of 57.2 ± 1.8 m.y. (Duncan and Hargraves, 1990).
The Elf Aquitaine well NMA-1, drilled in the North Male atoll lagoon, penetrated 115.5 m of basalts below the carbonate section. Alternating hard and soft, weathered 10-m-thick lava beds were composed of black to green aphanitic basalts with olivine. The age of these basalts was determined with the 40Ar/39Ar method to be 55 m.y. (Aubert and Droxler, 1996). This is consistent with the age from the ODP Site 715 and shows that these two dates provide reliable information about the timing of the basalt basement formation.
The Shell ARI-1 well was drilled in the central part of the Inner Sea (Figure 5). In its bottom section, the well encountered 50 m of weathered basalts. The severe degree of basalt alteration prevented reliable dating.
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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.