Regional context of the geology of the Andaman–Nicobar accretionary ridge
Published:January 01, 2017
Peter D. Clift, 2017. "Regional context of the geology of the Andaman–Nicobar accretionary ridge", The Andaman–Nicobar Accretionary Ridge: Geology, Tectonics and Hazards, P. C. Bandopadhyay, A. Carter
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The Andaman–Nicobar accretionary ridge forms the eastern boundary of the Bay of Bengal and is presently being constructed by accretion and underplating of sediments off-scraped from the obliquely colliding Bengal Fan. Net accretion is relatively low (c. 28%) with the rest subducted mostly into the upper mantle. Although subduction initiated along the margin at c. 95 Ma, large-scale subduction accretion likely accelerated during the Early Miocene by which time wedge top basins had formed. Prior to that time, sediment off-scraped during the Eocene against the ophiolitic backstop was probably derived from the adjacent magmatic arc of Burma. There was also some erosion of continental sources at that time, probably from the Sibumasu Block which forms the western edge of Sundaland. The scale of this accretion was small and potentially interrupted by times of tectonic erosion during the Palaeogene. The influence of continental erosion increased into the Oligocene, potentially accompanied by modest flux from the Indus–Yarlung Suture via the Irrawaddy River. Drainage capture in eastern Tibet in the Early Miocene and opening of the Andaman Sea, probably in the Late Miocene, has removed these source areas to the Andaman Trench.
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The Andaman–Nicobar Accretionary Ridge: Geology, Tectonics and Hazards
Rocks exposed across the hundreds of islands that belong to the 800 km long Andaman–Nicobar archipelago provide a condensed window into the active subduction zone that separates the India–Australia plate from the over-riding Burma–Sunda plate. Despite a strategic and seismically active location the Andaman-Nicobar ridge has seen comparatively little research. This Memoir provides the first detailed and comprehensive account of geological mapping and research across the island chain and adjacent ocean basins. Chapters examine models of Cenozoic rifting of the Andaman Sea and the regional tectonic and seismogenic framework. A detailed critical review of the Andaman–Nicobar stratigraphy, supported by new data, includes arc volcanism and a description of Barren Island, India’s only active volcano. Seismic history and hazards and the impacts of the 2004 earthquake and tsunami are also described. The volume ends with an examination of the region’s natural resources and hydrocarbon prospects.