62 NOETLING: PETROLEUM IN BURMA. 



The sandstone is very fine grained and usually very soft, but 

 sometimes it contains more silicious cement, and in that case either 

 thin continuous layers of a very hard, silicious grey sandstone are 

 formed within the softer beds, or the silicious matter concentrates 

 in the shape of globular concretions, both of which constitute great 

 obstacles to the limited resources of the native well digger. When 

 the sandstone is fairly soaked with oil it exhibits, when fresh, a fine 

 grass green colour, which, however, very soon changes to a dirty 

 brown. After being exposed for some time to the heat of the sun, 

 the oil evaporates, and then it is seen that the sandstone is of the 

 usual pepper and salt colour. The argillaceous beds generally consist 

 of a very tenaceous, bluish clay, forming either continuous beds 

 of considerable thickness, or thin layers alternating with equally 

 thin beds of sandstone ; the latter facies is known by the drillers 

 as " shale." 



Within the area of the Yenangyoung oil field only an insignificant 

 part of the Prome stage comes to the surface, chiefly in the form 

 of thin alternating beds of argillaceous and arenaceous character. 

 The lithological characters can generally only be ascertained by the 

 debris heaped round the mouths of the native wells. 



b, Paldeontological characters.-— Fossils are apparently very rare, 

 and I only once succeeded in finding a few in a conglomeratic bed 

 made up of rolled lumps of clay, carbonized wood and numerous 

 fragments of bones, about 156 feet from the surface. This bed was 

 not more than about 4 inches in thickness and was intercalated in 

 sand slightly charged with petroleum, and must have been of purely 

 local character, as it does not seem to occur anywhere else. The 

 fossils were not particularly well preserved, excepting some osseous 

 fragments and teeth; the calcareous substance of the other fossils 

 had been entirely destroyed by the action of the sulphuric acid, the 

 presence of which is explained by the frequent occurrence of iron 



pyrites in this bed. 1 



1 See my paper on the Development and Subdivision of the Tertiary system in 

 Burma ; Records, XVIII, p. 59* 



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