Geology of Burma

Burma begins with the Indo-Burman Ranges E of the lowlands of the Ganges and the Brahmaputra. This S-shaped fold belt extends 2,000 km to the S as far as the Andamans. As a physiographic barrier it has been since time immemorial an ethnographic, cultural and political boundary. Further to the E, in nothernmost Burma, other mountain ranges branch off the S abruptly from the E? W-striking fold bundles of the E Himalayas and run from the headwaters of the Irrawaddy via the Shan Plateau southwards to the T enasserim Ranges: the Sino-Burman Ranges. Between these two major mountain chains, which issue from a common root in the N, lies the Chindwin-Irrawaddy Basin, the Inner-Burman Tertiary Basin, which gradually widens towards the S. This is the fertile heartland of Burma. In terms of regional geology, Burma is in a key position for studying the phenomena of converging plates: W of and parallel to the Indo-Burman-Andaman? Nicobar Fold Belt runs the S Tethys suture, which separates the oceanic crust of the E Indian Ocean from the continental crust of SE Asia. In its off- shore section, the suture is identical with the Indonesian-Andaman Trench, a pronounced foredeep caused by a subduction zone. E of and parallel to the foredeep are (listed from W to E) the ? Outer Arc?, the ? Inter-Arc Through (Interdeep)?, the ? Inner Volcanic Arc? and the ? Back Arc Basin? with its cratonic foundation in the E, the Sino-Burman Ranges. Geological research in Burma commenced in the first of the 19th century and was relatively intensely pursued during the years when Burma formed part of British India (1885 - 1948). Following the estalishment of the independent Union of Burma (1948), geological studies were only hesitantly continued. It was not until about 1965 onwards that they were encouraged to some extent by organizational meas- ures introduced by the Burmese government, as well as by the careful opening up of the areas of economic activity and science. It is thus understandable that despite an astonishingly large number of indivi- dual papers on its geology in the older literature, and despite its considerable potential as regards natural resources, Burma is still in many respects geologically unknown territory. Because of the inaccessibility of the region, large areas of the W and E ranges framing the Inner-Burman Tertiary Basin, and also the entire region N of about latitude 25° N, remain some of the geologically least known areas of SE Asia. Obviously, any synthesis based on such sketchy knowledge is bound to be very unreliable. Nevertheless, it makes sense to sort out the knowledge that has so far been gained and to ar- range it in accordance with modern geological criteria, because it makes it easier for the geologist concerned with special questions to gain some insight into regional geological features, it provides an overview for dealing with regional geological problems, and it defines gaps in the knowledge and thus indicates the points where further geoscientific research should commence. In the years from 1969 to 1982, the authors spent various periods of time working as geoscientists in Burma. They got to know and developed an affection for this beautiful country and its friendly, hospitable and understanding inhabitants. In publishing this contribution on the geology of Burma, the authors wish to thank their Burmese colleagues.