Abstract The geology of the petroleum-bearing parts of Myanmar (essentially the western part of the country) is dominated by the oblique collision between the fixed Sunda Plate in the east (itself a mosaic of Gondwana-derived blocks, and since the Mesozoic a part of the much larger Asian or Eurasian Plate; Fig. 2.1) and the north-moving India Plate (e.g. Curray et al. 1979; Mitchell 1993; Curray 2005; Socquet et al. 2006; Steckler et al. 2008; Hall 2012; Rangin et al. 2013). Before considering the origin of the component parts of Myanmar it is necessary to identify the main structural units that now comprise the western part of the country. Figure 2.1 shows the importance of the Sagaing Fault and its possible offshore continuation in separating the Burma Platelet from the Sunda Plate to its east. Here we follow the terminology of Rangin et al. (2013) in choosing to call this the Burma Platelet, although earlier it was called the Burma Plate by Curray et al. (1979), the Indo-Burma-Andaman Block by Acharyya (1998) and the West Burma Plate by others (e.g. Hall 2012; Metcalfe 2013). The platelet is complex and is discussed further below, but one of its obvious features is the discontinuous belt of dormant volcanoes and granitoid intrusions running down the Central Burma Depression and dividing that major downwarp into forearc and back-arc tectonic domains (Wang et al. 2014). The cones of Mount Popa and Mount Taungthonlon (Fig. 2.1) are among Myanmar’s highest peaks, and the volcanic arc reappears in the Indian sector of the Andaman Sea as the active strato-valcanoes of Narcondam and Barren islands (Bandopadhya et al. 2014) before joining the volcanic arc of Sumatra.

Abstract The Andaman-Nicobar Ridge and the Indo-Burman Range are composed of sediments of the Bengal and Nicobar Fans scraped off the underthrusting Indian plate at the Sunda subduction zone. The Andaman Sea and the eastern part of the central valley of Burma represent a Neogene-Quaternary extensional basin underlain by oceanic crust formed by northwestward rifting of this orogenic ridge away from continental crust of the eastern Burma highlands and the Malay Peninsula. The plate edge is defined by a north-south transform in Burma, by the Sumatran fault system longitudinally bisecting Sumatra, and by a complex system of short spreading rifts and transforms in the central basin of the Andaman Sea. Where sedimentation rates are high over the newly formed oceanic crust, no magnetic anomalies are identifiable; where sedimentation rates are low or negligible, clear magnetic anomalies have permitted dating this phase of opening at approximately 11 m.y. B.P.

Abstract Andaman–Nicobar Ophiolites (ANO) occur as discontinuous bodies along the eastern margin of the Andaman and Nicobar Islands, the exposed parts of the outer-arc ridge of the present Sunda subduction system. The lithospheric architecture starts with mantle rocks overlain by crustal rocks with a thin transition zone in between. The mantle peridotites and the volcanic rocks exhibit great variability all along the ridge and demonstrate influence of subduction-related magmatism in their origin. Like many Tethyan ophiolites, the ophiolitic rocks of Andaman–Nicobar had their origin in a supra-subduction zone that were juxtaposed tectonically with younger sediments, now exposed on the present outer-arc ridge. The final emplacement of this oceanic lithosphere was unlike typical Tethyan-type ophiolites because, before its final emplacement over the Indo-Burma-Andaman (IBA) microcontinent, the subduction margin was charged with huge sediments from the river delta systems to the north that accreted at the leading age of the overriding plate, similar to some extent to cordilleran-type ophiolites. We propose a two-stage subduction model that displays a sequence of events from birth to resurrection that explains the petrological, geochemical and architectural variations of ANO. Supplementary material: The geochemical tables are available at https://doi.org/10.6084/m9.figshare.c.3634331.v1

Abstract The Andaman–Nicobar archipelago that forms the western margin of the Andaman Sea is a sediment-dominated accretionary wedge (outer-arc island) associated with a convergent margin tectonic setting. The Andaman accretionary ridge consists of two stratigraphically and structurally distinct terranes, juxtaposed and telescoped into a north–south-trending high-relief fold-thrust belt formed along the obliquely subducting eastern margin of the Indo-Australian oceanic lithospheric plate. The geology and structure of the ridge reflect the complexity of the evolving tectonics and stratigraphy of an accretionary wedge. Pre-Cretaceous meta-sedimentary rocks, Upper Cretaceous ophiolites and Palaeogene–Neogene sedimentary formations indicate rapid, spatial and temporal changes in lithology, sedimentology, sedimentary and tectonic environments, and palaeogeographic setting. This chapter outlines the current geodynamic setting, evidence for the history of accretion and regional geology and introduces the regional stratigraphic framework.