ORDOVICIAN SYSTEM : UPPER NAUNGKANGYI STAGE. 93 



detected anywhere to the westward of the G-okteik gorge, where 



it is found at the eastern end of some of the zig-zags on the cart 



road, and at the bridge in the bed of the gorge, but to the eastward, 



as far as the rocks have been traced up the Nam-Tu valley, it 



is very persistent, though not more than a few feet thick. 



Among the ranges east of the plateau the lower Naungkangyi 



beds are followed immediately by a great 

 Litholoeical characters. • , r , 1 ', ,■ 



thickness 01 purple rocks resembling very 



closely this narrow band at the top of the upper series. The 

 variegated shales of the western area are absent here, but since the 

 purple beds contain similar fossils, especially Pliomera ingsangensis, 

 which seems to be pretty freely distributed throughout, and is 

 especially common near the base of the formation, I think there 

 is little doubt that these eastern beds are the equivalents, in point 

 of time, of the whole series in the west, including the variegated 

 shales and the purple zone, and that the difference in colour is due 

 to accidental causes. These rocks are seldom calcareous, but possess 

 a peculiar texture, resembling that of the mudstones of the Lud- 

 low formation in England, with, as commonly happens in the latter 

 rocks, a tendency to become aggregated into nodular concretions. 

 They often exhibit no well defined bedding planes, and break with 

 a somewhat conchoidal fracture ; perhaps the term 'claystone ' is 

 the one that best expresses their peculiar character. 



The purple beds are found all along the crest of the Loi-len 



range east of Lashio, conforming everywhere 

 Distribution. Loi-len tQ the distribution of the lower Naungkangyi 

 range. 0 ° J 



band beneath them, but they are not developed 



to the same extent as they are further south, nor were they found to 

 contain any fossils worth collecting, probably because of the intense 

 crushing they have sustained. In some places, as on the pass near 

 Loilen village (Loc. 109, I 1), the pressure has been so great that 

 the beds resemble a schist rather than a shale, and were it not for 

 their position, and the traces of organisms which they still contain, 

 they might be taken for much older rocks. 



To the east of the broad plateau stretching eastwards from the 

 ! base of Loi Ling, in which the Tertiary coal- 



field of MYin-se-le, described by Mr. R. R. 

 Simpson, 1 is situated, rises an elongated dome-shaped mass of 



1 The Namma, Man-sang and Man-se-le Coal-fields, Northern Shan Stilus, Burma ; 

 Records, Geol. Surv. Ind., Vol. XXXI II, Pt. 2, p. 152. 



