Abstract 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.

The Andaman Islands are part of the Andaman-Nicobar Ridge, an accretionary complex that forms part of the outer-arc ridge of the Sunda subduction zone. The Tertiary rocks exposed on the Andaman Islands preserve a record of the tectonic evolution of the surrounding region, including the evolution and closure of the Tethys Ocean. Some of the Paleogene sediments on Andaman may represent an offscraped part of the early Bengal Fan. Through field and petrographic observations, and use of a number of isotopic tracers, new age and provenance constraints are placed on the key Paleogene formations exposed on South Andaman. A paucity of biostratigraphic data poorly define sediment depositional ages. Constraints on timing of deposition obtained by dating detrital minerals for the Mithakhari Group indicate sedimentation after 60 Ma, possibly younger than 40 Ma. A better constraint is obtained for the Andaman Flysch Formation, which was deposited between 30 and 20 Ma, based on Ar-Ar ages of the youngest detrital muscovites at ca. 30 Ma and thermal history modeling of apatite fission-track and U-Th/He data. The latter record sediment burial and inversion (uplift) at ca. 20 Ma. In terms of sediment sources the Mithakhari Group shows a predominantly arc-derived composition, with a very subordinate contribution from the continental margin to the east of the arc. The Oligocene Andaman Flysch at Corbyn's Cove is dominated by recycled orogenic sources, but it also contains a subordinate arc-derived contribution. It is likely that the sources of the Andaman Flysch included rocks from Myanmar affected by India-Asia collision. Any contribution of material from the nascent Himalayas must have been minor. Nd isotope data discount any major input from cratonic Greater India sources.