YENANGYOUNG. 59 



thickness, while the two upper ones include the remainder of the 

 Irawadi series. It is quite possible that the latter is capable 

 of a further subdivision, but owing to the inconstancy of the fossi- 

 liferous beds, and the uniform lithological character, I have not been 

 able to distinguish more than two zones. In fact the subdivision 

 of the beds above the zone of Hippotherium antelopinum into two 

 parts is somewhat artificial, as no definite boundary between the two 

 can be given, owing to the sameness of the lithological character of 

 the strata. Negative evidence, the absence or scarcity of fossil 

 remains, is in fact the only distinguishing feature. 



The zone of Mastodon latidens and Hippopotamus irravadicus 

 is formed by soft yellow sand rocks with subordinate conglomerate 

 beds, and is characterized palaeontologically by the two above- 

 named species, which almost certainly do not occur in the lower zone. 



The zone of Hippotherium antelopinum and Acerotherium peri* 

 mense forms a most conspicuous horizon of the upper tertiaries near 

 Yenangyoung. In the form of a dull red band it is visible at long dis- 

 tances, running continuously over hills and ravines, and encircling the 

 Yenangyoung oil field. In fact the presence of this bed has helped in 

 a great measure to interpret the structural relations of the, Yenan- 

 gyoung oil field. Lithologically this horizon is represented by a ferru- 

 ginous conglomerate, which varies somewhat lithologically ; at some 

 places it is a rather incoherent agglomerate of irregularly shaped 

 concretions of a ferruginous clay, at others it contains numerous 

 quartz pebbles cemented by a hard conglomeratic sandstone, at 

 others again it is an earthy iron ore, of a bright red colour. 



In thickness it varies also, being of not more than 10 feet thick- 

 ness at some, while at other places it swells out to about 25 or 30 

 feet. Palaeontologically this bed is characterised by the frequent 

 occurrence of Hippotherium antelopinum and Acerotherium peri- 

 mense, neither of which rise into higher horizons. Besides these 

 Crocodilis sp. Gavialis sp., Trionyx sp. are very common. Locally, 

 particularly east of Minli-ndoung, it contains hundreds of the two 



t 105 ) 



