10(3 



COGGIN BROWH : THE Bl KMA EARTHQUAKES OF MAY L911 



To the south of the crystalline area but still outside the 

 plateau, a broad area of deeply dissected hilly 

 Tawngpeng System. couutry intervenes, its most important member 

 consists of a series of metamorphosed, unfossiliferous, sandy or 

 argillaceous beds, to which the name Chaung Magyi series has 

 been given, owing to their great development in the valley of the 

 river ^of the same name. Here they occupy a narrow zone 

 below the precipitous scraps of limestone along the western edge 

 of the plateau overlooking the lrrawaddy plains. The western 

 boundary of this zone is marked by a fault, which brings them 

 into contact with the gneiss towards the north, and with the 

 PaUeozoic rocks to the south. Throughout this zone the strike 

 of the quartzites and slates is north and south, that is to say 

 parallel to that of the gneisses of the western bank of the lrra- 

 waddy. 



Practically the whole of the area which is termed " plateau ' is 



occupied by one formation, a dolomitie limestone 



Rooke of the Piatowu. ^ p alaeozo i c agCj am i the chief orographical 



features are due to the peculiar weathering and disintegration 

 of this rock. On the north it is bounded by the hilly country 

 described above, but ou the east its limits are not so well defined, 

 for in this direction the limestones are thrown into more or less 

 regular folds, and m succession with the older Paleozoic looks form 

 high hill ranges. To the south the plateau merges into that of the 

 Southern Shan States, the geology of which is practically unknown, 

 with the exception of the small area traversed by Mr. C. S. Middle- 

 miss and described in the paper previously quoted. In association 

 with the Plateau Limestone, and usually outcropping at its junction 

 with the Arclnean or Tawnpeng systems, 01 brought to the surface 

 in other places by faults, are various older PaUeozoic formations 

 belonging to the Ordovician and Silurian systems, while above the 

 limestones, strata of Kinetic and Jurassic age arc sometimes 

 found. 



The valleys of the Shan States are as a rule Idled with fluvia- 



BluviatileandLaouB- &* ««* lacustrine deposits of sands, silts 



triae valley depcrate. am l sand rock of late Tertiary Pkistoieno age. 



A very remarkable and constant feature of tltc Plateau Lmit- 

 stone is the extraordinary manner m which it 

 crushing of th. ; k as | jeeu c , usnoc l. To such an extent have 

 Plateau Limestone. . , , . .. . - f ■ 



difleiential movements taken place tnat it is 



