A Preliminary Synthesis of the Geological Evolution of Burma with Reference to the tectonic Development of Southeast Asia


Author : M. TheinPublication : Bulletin of the Geological Society of MalaysiaVolume : 6Page : 87 – 116Year : 1973


Description

Bulletin of the Geological Society of Malaysia, Volume 6, Jul, 1973, pp. 87 – 116

 

A Preliminary Synthesis of the Geological Evolution of Burma with Reference to the Tectonic Development of Southeast Asia

MAUNG THEIN

Department of Geology, Arts & Science University, Rangoon

Far better an approximate answer to the right question, which is often vague, than an exact answer to the wrong question which can always be made precise.

John W. Tukey (1962)*

* requoted from "Statistical Models in Geology" by W.C. Krumbein and F.W. Graybill (1964)

 

Abstract: A preliminary synthesis is attempted with a view to trace the geological development of the Burmese region in time and space. It is based partly on regional field experiences and partly on the published and unpublished information that have become available in the last decade. The model approach is found to be quite useful in this synthesis. It is hoped that this paper would stimulate lively discussions, further research and sounder syntheses.

The synthesis is made in term of seven topics: tectonic framework; areas of deposition and non-deposition; regional depositional pattern; tectonic and depositional environments; structural deformation and related metamorphism; igneous activity and associated mineralization; Burmese region in the general framework of continental drift. The tectonic framework is described with the aid of a generalized tectonic map newly compiled by the author; and four geo-tectonic domains are recognized and formally named.

The sequence of major geological events in the Burmese region is encompassed in a summary chart, and fuller and more refined accounts are given in the text by means of time-length diagrams and other kinds of model expressions. Time-stratigraphy of the Precambrian, Paleozoic and Mesozoic rock units is schematically shown by means of a representative time-length cross-section along the Shan-Tenasserim region which has become a stable block since the close of the Mesozoic. The regional depositional pattern of the Tertiary sediments in the Central Cenozoic Belt is shown by means of two time-length cross-sections, one along the general depositional strike and the other across it. The general pattern is interpreted as one of cyclical sedimentation. Contrary to some recent conceptions of the Central Belt as a geosyncline, available evidences seem to support an old idea - that the Central Belt most probably constitutes a graben. 

The geological development of Southeast Asia in general and of the Burmese region in particular in the general framework of continental drift is considered in the last section. On the basis of fitting of the pre-Tertiary outlines, presence of the Ninety East Ridge, and similarity of certain rock series, it is speculated that the Bay of Bengal may actually be a spheno-chasm, thus implying that Southeast Asia and the Indian Peninsula were probably once joined together in the distant geological past.