HISTORICAL SUMMARY. 



361 



the whole of the southern slopes of the range until, to the south 

 of Loi-len village, they have attained a width in plan of nearly 

 five niilep (Section I, Plate 24). They form the northern limb of 

 a great overfold, the axis-plane of which hades southwards, while 

 the southern limb has been let down by a fault of great throw, 

 bringing the Plateau Limestone, and indeed patches of the over- 

 lying red Namyau beds against the slaty series. The ribbon of 

 lower Palaeozoic rocks mentioned above can be traced continu- 

 ously along the crest of the range, widening out slightly, but 

 greatly crushed, until at Loi-len the beds are inverted, and dip 

 below the Chaung-Magyis. But further to the east their outcrop 

 increases more rapidly in width, and the single fold opens out and 

 is doubled, the purple beds and Naungkangyis being repeated 

 twice in the cross-section. At the same time the Plateau Lime- 

 stone mounts up the southern side of the range, and bends over 

 the crest, conforming to the undulations of the beds beneath, 

 and coalesces with the band which covers the northern flanks 

 (Section II, Plate 24). 



The structure of the Loi Pan — Loi Twang range seems to be 



that of a huge dome faulted in a direction 

 ran™ Pan— 1 Twan S transverse to the longer axis across the centre, 



so that the southern half of it alone is now 

 visible. The core of Chaung Magyi rocks is very broad at the northern 

 end, but gradually narrows, until to the south of Loi Twang it dies 

 away altogether. The fossiliferous Palaeozoic rocks along the 

 eastern flanks form one limb of an immense anticlinal arch, the 

 western limb of which has been faulted down out of sight. To the 

 north, between Mong La and Pinghsai (H 4), the belt of fossiliferous 

 rocks is very broad, and is partly repeated by a minor fold on the 

 Nam-hen ; but to the south of Pinghsai it becomes! more narrow 

 and compressed, and near Hwe Mawng there are signs of inversion 

 of the strata. The structure along the eastern side of the ranges 

 east of Mong Yai, in the valley of the Nam Pang, is precisely 

 similar. 



(ii) Subsidence Faults. 



To what cause the vertical faults which have done so much to 

 . diversify the scenery of the plateau must be 



attributed is not quite clear. In their mode 

 of occurrence, especially in the manner in which they are repre- 



