494 



L. Dudley Stainj>- 



be superimposed systems of different ages, and when it was found 

 that the Pegu beds passed northwards into freshwater deposits, the 

 latter were termed " Freshwater Pegus ". For the present this term 

 may conveniently be retained for those freshwater beds which are 

 shown by their vertebrate remains to be earlier than the well-known 

 Irrawadian of the Oilfield region of Yenangyaung, Minbu, etc. 



1. The Marine Post-Eocene or Pegu System [sensu lato). 

 A number of horizons can now be distinguished on a palaeonto- 

 logical basis (" Standard Faunas "), and at least some of the stages 

 based on a study of these faunas can be traced through the changes 

 of facies from Lower to Upper Burma. The relationship of the 

 lithological divisions to the stages is far more easily expressed in 

 diagrammatic form and a mass of detail has been incorporated in 

 Fig. 3, which is not rejDcated in the text below. 



Lithological Divisions 

 {Lower Burma). 

 Akauktaung Series.^ 

 Pyalo Sandstones. 



Kama Clays. 



Prome Beds (" A "). 



Stages?- 



Akauktaung and Pyalo 

 Stages. 



Kama Stage. 



Singu Stage. 



Lithological Divisions 

 ( Upper Burma). 

 Represented by Fresh- 

 water beds (? base of 

 Irrawadian). 

 Brackish upper part of 



Pegu, 

 r Exposed Pegu Beds of 





Sitsayan shales with 

 Lepidocyclina Lime- 

 stones. 



Kyet-u-bok Bed. 



rSitsayan Stage. 



(Shwezetaw Stage. 

 Kyet-u-bok Horizon. 



the Oil Fields 

 Minbu, etc. 



of 



Shwezetaw Sandstones, 

 etc. 



Velates Bed (Dudaw 

 Taung, etc.). 



The total thickness of the Pegu System in Lower Burma may be 

 taken to be roughly 10,000 feet. 



Basal or Kyet-u-h6k Bed.^ 



This bed, which the writer regards as the base of the Pegu System, 

 is a well-marked calcareous band, conglomeratic in places with 

 small quartz pebbles. It is characterized by four species of 

 foraminifera, always present, but in very variable proportions. 

 They are Nummulites yawensis Cotter (formerly described as N. 

 cf. heaumonti^ SiXid. N. beanmonti),^ Orthophragmina omphalus Fritsch, 

 Operculina cf. canalifera D'Arch., and Gypsina globulus Reuss. 

 The associated moUusca include species common to the underlying 

 Yaw Stage, notably Velates orientalis. Whilst the species of 

 foraminifera mentioned occur in enormous numbers in the bed itself, 



^ Slightly modified from Vredenburg, Sec. G.S.L, vol. liii, pt. iv, 1921-2, 



pi. XXV. 



2 " Marine Irrawadian " of Stuart, 1909-10 ; Mogaung Sands of Theobald, 

 1874. 



3 Named after a now non -existing village from whence it was first noted by 

 Dalton, Q.J.G.S., vol. Ixiv, 1908, p. 612. 



* Dalton, op. jam. cit., p. 612. 



5 Cotter, Eec. G.S.I., vol. xli, pt. iv, 1911-12, p. 226. 



