TAWNG-PENG SYSTEM : CHAUNG-MAGYI SERIES. 



49 



planes of the rock. The high angles of dip usually presented by 

 these older rocks may also be taken as a guide in mapping them, 

 especially in the neighbourhood of the boundary with the Namhsim 

 sandstones, for which they are most likely to be mistaken, for the 

 latter rocks as a rule rest at low angles upon their upturned edges. 



The rocks of the Chaung-Magyi series formed a continuous 

 floor upon which the succeeding fossiliferous 

 boundary"*' 0 "' Western formations were deposited, and wherever the 

 latter have been removed by denudation to a 

 sufficient depth, these older rocks are exposed beneath them. Along 

 the western edge of the plateau they occupy a narrow zone 

 below the precipitous scarps of limestone overlooking the plains 

 of the Irrawaddy, extending due south along the left bank of the 

 Chaung-Magyi or Maddeya river,— from which the name of the 

 series is derived,— to the point where, leaving the hills at Zehaung, 

 it turns west to the Irrawaddy ; and beyond this to within a 

 short distance of the head of the Kyetmaok stream, above tbe 

 village of Taunggaung (B 4). The western boundary of this 

 zone is marked by a fault, bringing the Chaung-Magyi rocks against 

 the Archaean gneiss to the north of Zehaung, and against the 

 Plateau Limestone and underlying Palaeozoic rocks to the south of 

 that place. Throughout this zone the strike of the quartzites 

 and slates is N. — S., parallel to that of the gneisses on the west 

 bank of the Irrawaddy. 



The inner boundary of this zone is more irregular, the actual 

 location of the line of junction depending on 



Southern and Eastern th d ^ ^ t western scarp 0 f t J le 



boundary. r ° r 



plateau has been cut back, and on the relations 

 between the dip of the rocks and the contours of the hill slopes. 

 Towards the north the elevation of the boundary line above the plain 

 gradually increases, until at a point somewhat to the south-east of 

 the sudden bend of the Nam-pai from west to south (at the peak 

 marked Hpataunggyi, 3,664 feet on the map, Fig. 3, p. 62), the overlying 

 rocks disappear, and the boundary sweeps round to the south-east 

 in the direction of the head of the Gokteik gorge. At the same 

 time the strike of the rocks also changes in direction, and becomes 

 N.W. — S.E., or almost at right angles to the prevailing strike of the 

 gneisses. The rocks in this area form a succession of straight 

 ridges, coinciding in direction with that of the strike, and separated 

 by streams flowing either to the north-west, into the Nam-pai, 



