﻿620 3IE. L. V. DALTOX ON THE [NoY. I908, 



questions of the subdivision and the thickness of the Pegu Grroup, 

 which have by no means been thoroughly threshed out. The 

 subdivision proposed by Dr. !N"oetling, into TenaugyouDgian and 

 Promeian, was based upon the appearance of certain beds in a deep 

 ravine in the centre of the Tenangyoung dome, and upon the 

 assumption, from inadequate study of the lower beds of the group 

 in Lower Burma, that they were unfossiliferous. As to the first of 

 these, a purely lithological distinction, it is observed : (1) that the 

 beds near the crest of the anticline at Yenangyoung, and in 

 particular the clays, are noticeably blue in deep ravines at any 

 point in this inlier ; (2) that where continuous sections are exposed, 

 as in the Yaw-Yalley region, in jungle-country (as distinguished 

 from the dry zone, with its facilities for weathering and oxidation), 

 the whole series is equally blue in colour, and the olive tints 

 described as characterising the Yenaugyoungian are absent. More- 

 over, when Dr. Noetling saw such a section of the Miocene in the 

 Chindwin district, where the country is covered by forest, he 

 noticed the absence of the olive tints, and attributed it to the 

 absence of the Yenaugyoungian : whereas, after passing from the 

 known Yenaugyoungian localities in the south of the Pakokku 

 district, in the dry zone, to those of the Chindwin, through inter- 

 mediate country less thickly covered with jungle, one is conscious 

 only of a gradual change from olive in the more exposed regions 

 to blue in the forest-covered districts on the north in corresponding 

 beds ; while the Upper Miocene of the Thayetmyo region shows the 

 blue colour also, though to a less extent, as much in the topmost 

 beds of the Miocene as in those immediately above the Eocene 

 boundary. As to the second, fossiliferous horizons, as we have seen, 

 do occur in Theobald's ' Sitsyahn Shales,' where these are exposed 

 in the Thayetmyo district, and while no fossils have been found in 

 wells drilled by the Burmah Oil Company in this series in the north, 

 it needs but a very little knowledge of the system of drilling adopted 

 in these oil-fields to enable us to realize how fortuitous it is that 

 fossils, except perhaps from beds full of them, will be brought to 

 the surface in anything like recognizable condition. 



We see, therefore, that, in the first place, the olive tints of the 

 Upper Miocene Beds in the exposed regions of the ' dry zone ' 

 appear to be due to weathering, as they are absent in the least 

 exposed portions of these beds there, and absent also in the forest- 

 clad regions elsewhere ; in the second place, the lower parts of the 

 Miocene in Lower Burma have been shown to contain fossils, and 

 there is no legitimate ground for the assumption that the unexposed 

 parts in Upper Burma are completely unfossiliferous. This throws 

 us back, therefore, on the Pegu Stage as the only valid division : 

 and from our present knowledge of the series there seems to be no 

 ground for any further subdivision, since the character of the rocks 

 is the same throughout. Some subdivision is perhaps desirable and 

 possible ; but it seems to be better to have none, rather than that 

 based on an erroneous interpretation of the evidence. The series 

 requires much fuller and more detailed study than has yet been 

 given to it, before any sounder basis can be suggested. 



