482 L. Dudley Stamp — 



II. Physical Geography of Burma. 



Burma falls very simply into well-marked natural regions, the 

 physiography of Avhich is controlled mainly by the geology, whilst 

 minor subdivisions can be made on a climatological basis. The 

 main divisions are as follows (see Fig. 1) : — 



(1) The Shan Plateau,^ occupying the whole of the east of the 

 country. It is a region of highly folded Pre-Palseozoic, Palaeozoic, 

 and early Mesozoic rocks, the folds running mainly north and south. 

 Bounding this region on the west is a great line of dislocation which 

 has for many hundreds of miles a roughly north and south direction. 

 This may be termed the Shan Boundary Fault, and the change from 

 the central lowlands to the plateau is at once abrupt and sharply 

 defined. Immediately to the east of the fault there is usually a 

 strip of crystalline rocks. The Shan Plateau is on an average 

 between 3,000 and 4,000 feet above sea-level, and is continuous 

 with the plateau of Yun-nan. As a contrast to the fine highland 

 scenery of the Palaeozoic rocks, well known to the frequenters of 

 Burma's favourite hill-stations — Maymyo and Kalaw — there are 

 broad, level tracts marking the sites of lake basins filled with late 

 Tertiary or Pleistocene deposits. These basins are of some 

 importance as yielding brown coal ^ (as in the coalfields of Lashio, 

 Namma, etc.), and in one case oil-shale. Some of the basins are 

 still occupied by lakes (as Lake Inle). It may be noted, en passant^ 

 that the coals of the Shan States belong to two distinct groups ; 

 firstly, the Late Tertiary or Pleistocene ^ lignites occurring as almost 

 horizontal beds in the basins already mentioned ; secondly, the 

 humic coals of early Jurassic age occurring ia strata which have 

 been subjected to the same intense folding as the Palaeozoic sediments. 

 The coals of Kalaw (Loi-an) belong to the latter group.* It is not 

 the purpose of this note to discuss the Shan Plateau or even its 

 Tertiary basins ; the important points to notice are : — 



(a) the main folding is post-early Jurassic and pre-late Tertiary, 

 (6) the absence of early Tertiary deposits which are of such enormous 

 thickness in the central Tertiary region make it almost certain that the 

 main folding and the initiation of the Shan Boundary Fault are pre- 

 Tertiary, 



(c) from the but slightly tilted late Tertiary deposits in the lake basins, 

 the Shan Plateau must have played the part of a " stable block " during 

 the late Pliocene folding of the main Tertiary region of Burma. 



(2) The Central Tertiary Belt, a strip of country 500 or 600 miles 

 from north to south and averaging 130 miles wide, bounded by the 



^ La Touche, " Geology of the Northern Shan States" : Mem. Geol. Surv. 

 India, vol. xxxix, pt. ii, 1913 ; Middlemiss (part of Southern Shan States), 

 Gen. Rep. Geol. Surv. India for 1899-1900. 



^ La Touche and Simpson, Rec. Geol. Surv. India, vol. xxxiii, pt. ii, 1906, 

 pp. 117 et seq. 



3 Annandale, iJec, G.S.I. , vol. 1, pt. iii, 1919, pp. 50-64. 



* Unpublished information. The writer has collected Jurassic plants and 

 the same conclusions as to age have been reached independently by other 

 observers recently. 



