196 BROWN & HERON: GEOLOGY AND ORE DEPOSITS OF TAVOY. 



Towards the margins of the basins synclinal dips of 20° — 40° 

 predominate, with an exceptional case as high 

 as 75°, but they flatten out" to low angles or 

 to near horizontally towards the centre, though oven in flatly 

 lying beds minor corrugations are frequent and everywhere the 

 Tertiaries show irregular disturbance. Minor faults are also often 

 seen. 



Recent and sub-recent Formations. 



These deposits are of two ages, and where both are seen in one 

 section they are separated by a slight uncon- 

 formity. The period of the older division is 

 uncertain, for they may be uppermost Tertiary, but in the Great 

 Tenasserim valley in Mergni similar bed'? lie unconformable on the 

 Tertiary conglomerates above the horizon of the Theindaw-Kaw- 

 mapyin coal. The newer beds are identical with, and stratigraphi- 

 cally continuous with, the materials now being laid down by the 

 streams of the present day. 



In the open upper valley of the Tavoy River, above Kaleinaung, 



the river is now cutting down through slightly 

 Oldor alluvium. .. , . _ , , . , -, 



consolidated horizontal sands and coarse 



conglomerates, forming cliffs about 20 feet in height, conglomerates 

 at the base and sands above. At the head of the lower portion 

 of the valley, near Doodaung (Kadutaung), similar conglomerates 

 outcrop as bars across the stream, and elsewhere are probably 

 widely spread but concealed by later accumulations. It is possible 

 that the coarse boulder conglomerates upon which Tavoy civil 

 station is built are of the same period, though they may equally 

 well be of earlier (Tertiary) age ; they carry both cassiterite and 

 gold and present several difficult problems, such as the transport 

 of such large fragments to the centre of a flat and open valley so 

 far from hills and swift-flowing streams. The cassiterite and topaz 

 bearing gravels, with a white clay matrix, which are profitably 

 dredged for tin on the Hindu chaung, a tributary of the Tenas- 

 serim, are in all probability of the same age, whatever that age 

 may be. An elephant tooth dredged from the tin-bearing gravels 

 is closely allied to those of the modern Siamese elephant. 



Exposed on the banks of the Tavoy River between tide limits 



near Tavoy town, are gently inclined clays overlaid by recent 



alluvium now in progress of deposition. Certain fossil crabs 



reserved as curiosities in local " pongyichaungs ' (monasteries) 



