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Dehradun: ONGC (C) Modified from Curray and Moore (1971).) Geology and hydrocarbon prospects of Andaman-Nicobar Basin. (C) Profile of the Middle Andaman and a laterally spreading Andaman Sea and the arc of seamounts and dormant and active volcanoes. (B) The cartoon shows the Andaman Island Arc subduction complex in the west adjoining the oceanic trench, the arc of seamounts in the east, the dormant and active volcanoes, and the laterally spreading Andaman Sea further east. (A) The sketch map shows ENE–WSW- to NE–SE- and ESE–WNW-oriented wrench faults splitting the island chain. Southeastwards, this volcanic arc joins up with the belt of Sumatran volcanoes.įig. This arc of volcanoes extends north onto the continent through the long and wide sedimentary Irrawaddy Basin of central Myanmar, where it is represented by Miocene-to-Quaternary volcanoes ( Fig. The graben extends southeastwards onto the Semenko rift valley in Sumatra. Close to the above-mentioned fault occurs a festoon of seamounts (Alcock and Sewell), a dormant volcano (Narcodam), and an active volcano (Barren). This fault has downthrown the eastern block (footwall) to a depth of 3000 m below the mean sea level. The eastern margin of the Andaman ridge is characterized by a 60 km × 20 km shallow platform known as the Invisible Bank that is demarcated by a steep deep normal fault along its eastern end. The East Andaman Fault is longer in extent. 16.2C), which divides the sea into two basins: the forearc Bay of Bengal and the back-arc Andaman Sea. The most prominent and extensive fault is the West Andaman Fault defining the underwater Java Trench ( Fig. The eastern margin of the Andaman Ridge is characterized by a 60 km × 20 km shallow platform known as the Invisible Bank. Along these faults occur at various structural levels the dismembered bodies of ophiolites, which are the basic and ultrabasic plutonic rocks sliced off from the ocean floor.
#Obduction number system series#
They form a series of narrow folds split longitudinally by multitudes of roughly N–S trending faults that dip eastwards like listric faults giving rise to a schuppen zone ( Roy, 1983).
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The arcuate chains of islands are made up of largely Upper Cretaceous to Early Tertiary flysch sedimentary rocks. These sediments were and are being delivered to the sea predominantly by the Ganga and Brahmaputra rivers. Largely filled up with oceanic sediments, it represents the forearc basin. The Island arc is a tectonically resurgent mobile belt adjoining an extremely active obduction zone called the Java Trench ( Fig. Valdiya, Jaishri Sanwal, in Developments in Earth Surface Processes, 2017 Lithotectonic Architecture