﻿Vol. 64.] GEOLOGY OF BUEMA. 617 



bamboos on the former. From the boundary of the Chindwin divi- 

 sion northwards as far as Kabaing (long. 94^ 43' E., lat. 22° 13' N.) 

 Pliocene continues ; no dips were observed, except a possible 5° 

 westwards half a mile south-west of Kabaing ; but, since in a range 

 of hills running northwards from near Nyaungbinle (94° 42' E., 

 22° 20' jST.) Miocene rocks crop out with anticlinal structure, the 

 fold probably extends southwards in a less marked degree in the 

 overlying Pliocene. From Nyaungbinle, the Mahu Daung, as this 

 range is called, extends towards Mingin on the Chindwin Kiver, and 

 shows a series of blue shales and grey conglomeratic sandstones 

 under the Pliocene—bent into an unsymmetrical arch, the eastern 

 flank of which dips at about 70° to 90° and the western at 15° to 

 50°. The pebbles in the sandstones are fairly large and irregularly 

 distributed in the grey sandstone-matrix, this character persisting 

 up to the lower limit of the Pliocene. Some thin beds of purple 

 marls occur in the Miocene of this district near the top. 



III. General and Stratigeaphical. 



In the foregoing pages a series of observations have been 

 recorded relating to the Tertiary of Burma, of which those 

 regarding the Eocene rocks are confined to one district, whereas 

 the Miocene has been studied at several points in the Irawadi 

 Valley. 



In the hitherto unstudied Bassein Stage, several fossiliferous 

 horizons have been noted, and it seems possible to correlate the 

 various sections and to determine certain palaeontological zones 

 in a tentative way. The lowest horizons are those yielding 

 Turritella sp. 3 near the anticlinal crest south-west of Thabyem- 

 young, and various fossils (including Operculina canalifera) with a 

 cast of Turritella, possibly the same species, on the crest in the Man 

 choung near Subagyidan. From general considerations, these two 

 may be assumed to be the same and termed ' the 'Turritella-Zone.' 

 We have also another fossil occurring in considerable quantity, in a 

 bed found at two points about 10 miles distant along the strike, 

 namely AmpuUina grossa, var. ohlonga, and in both cases about 

 6000 feet above the assumed Turritella-Zone. This, therefore, 

 appears to be a sufficiently well-defined horizon to be termed ' the 

 Zone of AmpuUina grossa.' In addition to these, what are perhaps 

 better-marked zones exist, but they are at present observed only 

 ^t one locality in each case : namely, the nummulitic limestone at 

 the top of the Bassein Group, with Nummulites Beaumonti (?) in 

 large numbers, and the thin band of white limestone largely made 

 up of small globular hydrozoa, probably not less than 100 feet below 

 the former. 



At an horizon approximately corresponding to the last, and 

 probably below rather than above it, in blue clays, Corhula harpa 

 occurs in considerable numbers, so that this may be termed the 

 zone of that fossil. Hence, we have the following general section 



