ORDOVICIAN SYSTEM : LOWER NAUNGKANGYI STAGE. 



so greatly crushed and distorted as to be in some cases unrecognis- 

 able. Beyond Panghti this simple fold appears to be replaced by 

 two or more minor folds, due to a twist in the direction of the 

 main anticlinal, but the ground along the crest of the range is so 

 entirely covered with dense grass jungle that the structure could 

 not be made out exactly. The Plateau Limestone here comes 

 up from the south almost to the crest and arches over the lower 

 Palaeozoic rocks, which disappear entirely beneath it a few miles 

 further on, near the village of Tenghkio (J 1). 



The lower Naungkangyi beds do not appear on the southern side 

 , , _ . _ . of the Nam-Pawns; valley, or on the northern 



South of Loi-Ling. i <• t • t • ±\ 



and eastern slopes of Loi-Ling, where they 



are overlapped by higher strata. They are next found along the 



south-western base of Loi-Ling and are exposed at the point where 



the cart road from Mong-Yai to Tang-yan enters the hills, about 



a mile east of the village of Nam-un (I 2). Here also they are 



vertical, greatly crushed, and the fossils are almost unrecognisable. 



A few miles further to the north-west they disappear beneath the 



Tertiary silts of the Nam-Sang coal-field, but to the south-east 



they can be traced for a long distance, forming a narrow fringe 



along the edge of the Chaung-Magyi rocks which form the core of 



the range between Mong-Yai and the valley of the Nam-Ha. 



A great fault runs along the valley of this river, bringing down 



the Plateau Limestone and the rocks beneath 



Valley of the Nam-Hd j t aga i ns t the Chaune-Maffyi series, forming 



(Section HI, Plate 24). & , & . bJ ' 6 



a great mass of interlacing ridges and valleys 

 to the east, and on the west side of this fault there are at least 

 two minor faults which, combined with the folding that has affected 

 all the rocks, have rendered the structure exceedingly complex. 

 The band of lower Naungkangyis can be traced, however, wherever 

 the Chaung-Magyi rocks come to the surface, and can be easily 

 recognised by the fossils, usually by the presence of Rafinesquina 

 imbrex, Orthis subcrateroides, and Diplotrypa sp., which are the most 

 common forms. In one or two localities a hard siliceous rock occurs 

 crowded with casts of a species of Ctenodonta or Nucula, in which 

 the teeth are well preserved. One of these localities is on the 

 spur running west from the village of Mong-Ha to the peak marked 

 6,055 feet, about three-quarters of a mile below the crest of the 

 ridge (Loc. 110, I 3). Another is near the southern extremity 

 of the hills, at the head of a deep lavine cut through Chaung- 



Q 



