POST-PLIOCENE BEDS. 65 



side of the broad valley of this stream I have not detected 

 any more on the Yenangyaung hills. In the southern blocks 

 there is no trace of this gravel, but west of them on the tops 

 of the hills at Nyaunghla close to the Irrawaddi it is found, 

 but is at a different level from that of the gravel near Yen- 

 angyaung and farther north. Plateau gravel is also found on 

 the top of the Tangyi hills and in the country round Pagan also at 

 the different levels. Besides being found on the hills similar gravel 

 is also found in the neighbourhood of the Yenangyaung oil-field, 

 amongst recent deposits in the valleys and near the Irrawaddi 



Nature of the compo- river - These beds of plateau gravel consist 

 nents of plateau gravel. of large we ll.r unded pebbles of quartz and 



fossil wood, which are mostly bound together by a red ferruginous 



matrix of clay, sand and smaller pebbles ; the lower beds of the gravel, 



however, have not so much cementing material as those on the tops 



- . . , . ,. of the plateau. The fossil wood and the maior- 



Ongin of the pebbles. r 



ity of the smaller pebbles were evidently 

 derived from the Irrawaddi beds, but I do not think it is possible that 

 the larger pebbles could have been derived from these beds, for 

 although in a few places I have seen pebbles as large as the average 

 big pebbles of the plateau gravel, these were comparatively scarce 

 and there were none so large as the largest of the pebbles in the 

 gravel. The fossil wood in the gravels is mostly highly silicified 

 like that scattered through the conglomerates of the uppermost of 

 the zones in which I have divided the Irrawaddi beds. 



The recent deposits at a lower level, called by Dr. Noetling 1 the 



lower silt, I shall not describe here as they 



Noetitng? Wer S1 ° r * ma y better be considered when I come to deal 



with the extensive deposits of a similar nature, 



which cover the country between the ranges of hills, and of which 



these are merely parts. 



Besides this lower silt, but very difficult to distinguish from it, 

 there are deposits of stream sands from the present streams and rain- 



Memoirs, G. S l„ Vol. XXVII, Pt. 2, 



( 65 ) 



