Abstract The Moattama Region as defined by the Myanmar government and Myanma Oil and Gas Enterprise (MOGE) comprises a number of different geological elements, but is dominated by the Martaban Basin which lies between the Yadana and M8 highs in the west and the Tanintharyi Shelf in the east (Fig. 7.1). The westernmost margin of the defined region includes the MD-1, MD-2 and MD-3 blocks (Fig. 7.2) which occupy the southwards continuation of the Rakhine Basin (discussed in Chapter 9) and includes the plate boundary between the Indian Plate and the Burma Microplate. The dominantly Late Oligocene–Early Miocene carbonate platform of the Yadana and M8 highs overlies a volcanic basement, and in turn is overlain by a relatively thin succession of Upper Miocene–Recent clastic sediments deposited from the ancestral Ayeyarwady River. Seismic sections over these structural highs show them to have had a complex history of alternating deposition and uplift and, in the case of the narrow M5 basin which separates these highs, there was clearly a phase of structural inversion between the Middle and Late Miocene. Further east in the central part of the Martaban Basin area, a thick clastic succession of ?Early–Late Miocene age is present. This is thought partly to have been deposited from the ancestral Ayeyarwady River and partly from the other major river entering the basin, the Thanlwin River. Sediment from those two sources cannot be distinguished on seismic sections, and in this account we refer to the combined package as the Thanlwin/Ayeyarwady delta system. This Martaban Basin sedimentary sequence then thins eastwards onto the Tanintharyi Shelf (Fig. 7.1).