490 L. Dudley Stamp— 



Pondaung Sandstone. — A very interesting series of deposits. The 

 lower part comprises beds of greenish sandstone (weathering yellow), 

 with bands of conglomerate and greenish shale and passes down 

 quite gradually into the Tabyin Clays below (1 in. map, sheet 

 84 K./5). Fossils here (latitude 21° 50' to 22° 4-5') are scarce, but 

 include Area, Cardita, and other marine forms. Going upwards in 

 the series the Pondaung Sandstones exhibit a gradual change from 

 marine to brackish and finally to freshwater and land conditions. 

 Plant remains (wood) occur throughoiit ; in the lower part the wood 

 is carbonized, higher up partly carbonized and partly silicified, whilst 

 in the highest part it is always silicified. It should be mentioned 

 that silicified wood is highly characteristic of continental deposits 

 in Burma. As one passes northwards (as from latitude 21° 45' to 

 23° 30') the upper continental beds thicken at the expense of the 

 lower marine. The most striking members of the continental facies 

 are beds of clay — purplish, pale greenish, or mottled — with abundant 

 vertebrate remains indicating their formation in freshwater lagoons.^ 

 The remains include mammals {Anthraeotherium, Anthracohyus, 

 Metamynodon ? etc.), crocodiles (Crocodilus), and huge turtles. From 

 about latitude 22° 0' to 22° 30' the highest bed is a " Red Bed " or 

 layer of laterite denoting terrestial conditions. To the south the 

 whole of the Pondaung Sandstones become more marine, the mottled 

 or purplish clays are not found much to the south of latitude 20° 30', 

 and oysters ^ {Alectryonia noetlingi) are here abundant. Large 

 nummulites are common from 20° 5' southwards. The group is as 

 thick as 6,500 feet in latitude 22° 5'. 



Yaw Stage. — A series of shaley clays with an interesting fauna 

 which has been described in part.^ The series is essentially a marine 

 one, and fossils include Nummidites yawensis Cotter,* V elates 

 orientalis Vred. (near F. schnideliana Chemn.) — the latter especially 

 in the upper part^ — large Ampullince {A. cf. grossa Desh.), etc. The 

 stage is typically developed about latitude 21° 30' longitude 94° 

 20' E. ; northwards marine fossils gradually become scarcer and 

 stunted, and the deposits wedge out, being absent in latitude 22° 45'. 

 Owing probably to the proximity of the western shore-line, the 

 deposits are very sandy about latitude 21° 5', but again become 

 of deeper-water type in the Ngape-Yenanma area (latitude 

 19° 50' to 20° 5'). Eastwards in the Myaing district (latitude 

 21° 37', longitude 94° 52') the series is again of shallow- water type, 

 possibly due to the nearness of the ridge of ancient rocks of 

 Shinmadaung mentioned above. In the north the base of the Yaw 



^ For details on all these points see Stamp, " Geology of Part of the Pondaung 

 Range." 



2 Pilgrim and Cotter, Rec. G.S.I., vol. xlvii, pt. i, pp. 42-77, pis. 1-6. 



^ Cotter, " The Lamellibranchiata of the Eocene of Burma " : Palceontologia 

 Indica, 1922 (in the press). 



* Cotter, " On the Value of Nummulites as Zone -fossils, with a Description 

 of some Burmese Species " : Rec. G.S.I., vol. xliv, pt. i, 1914. 



