354 LA TOUCHE : GEOLOGY OF NORTHERN SHAN STATES. 



beds and the manner of their deposition show that they were 

 laid down on the very edge of the depression, l and it doe3 not 

 follow that older marine strata may not exist beneath the allu- 

 vium further to the south. 



The third instance of a recent exposure of the old sea-floor is of 

 a somewhat different character, but it lends, 



Asakau loma. T 



i think, some support to my suggestion that 

 the break up of this portion of the Gondwana continent began at 

 about this period., and throw3 some light on the manner in which 

 , , the movements originated. It has long been 



Uriiissic beds 



known that rocks of Triassic age exist among 

 the parallel ranges of hills that constitute the Arakan Yoma in 

 Lower Burma, and that they are associated with upper Cretaceous 

 beds (Maestrichtian), with Cariita Beaumontir The Triassic beds 

 contain the well known Himalayan genus Halobia, and the species 

 found was identified by Stoliczka as H. Lommeli, 3 but is probably 

 distinct. It, is, however, associated with a species of Avicula 

 allied to A. (?) Girthiana Bittner, also a Himalayan type, and thus 

 indicates a somewhat close connection between this area and the 

 southern shore of the ' Tethys ' in Triassic times at least. No rocks 

 older than these have been met with among these hills, but there 

 is no reason why Carboniferous or Permian strata should not exist at 

 , , greater depths below the surface. Here again 



Burmese foredeeps. ° f- . » » 



we have brought to light the floor ot a de- 

 pression that was certainly in existence in Triassic times, but this 

 depression was evidently at right angles to that of the Ganges 

 valley. It is, in fact, the ' foredeep ' corresponding to the Burman 

 arc of elevation, just as that of the Ganges valley corresponds 

 to the Tibetan or Himalayan arc. The subsequent history of the 

 depressions has many points in common : both have been filled up, 

 that of the Ganges entirely, and that of Burma partly, by Tertiary 

 and recent deposits ; but the advance of the respective earth thrusts 

 has resulted, in the former case in the folding of the Siwaliks 



3 H. B. Medlicott, Geological Sketch of the Shillong Plateau ; Memoirs, Geol. Surv. 

 Ind., Vol. VII, Pt. 3, p. 168 : Mr. Medlicott also suggests (Coal in the Garo Hills ; Records, 

 Geol. Surv. Ind., Vol. VII, Pt. 2, p. 62) that the Cretaceous coal measures of the Garo 

 Hills were deposited in pre-existing valleys, in which case this side of the depression 

 must have been above water till the end of the Mesozoic epoch. 



2 W. Theobald, Geology of Pegu ; Memoirs, Geol. Surv. hid., Vol. X. Pt. 2, pp. 127-137: 

 G. H. Tipper, Preliminary Note on the Trias of Lower Burma ; Records, Geol. Surv. Ind., 

 Vol. XXXIV, Pt. 2, p. 134: Further Note on the Trias of Lower Burma; Ibid, Vol, 

 XXXV, Pt. 2, p. 119. 



1 Theobald, Op. cit., p. 135. 



