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



exposed on the seaward face of the Coastal Bulge. They show 

 surprisingly Blight alteration, merely a little marginal bleaching 

 and silicification. 



The granite shows few indications of having been subjected 

 to severe earth stresses, such as would be 

 apparent if it had participated, as a solid 

 rock, in the great compressive movements which uplifted the Indo- 

 Malayan mountain chains. It may therefore either have been 

 intruded towards the end of the period of folding, or if intruded 

 earlier, must have remained in a plastic condition throughout the 

 period of maximum activity ; in any case it would appear that 

 the granite accompanied the upheaval and was not an older intru- 

 sion fortuitously involved as part of a pre-existing rock associa- 

 tion. But speculation regarding its exact age is better postponed 

 until the geological survey of Tenasserim has proceeded further 

 than it has at present, and especially until the relationships of the 

 granite and the great Permo-Carboniferons limestone series have 

 been studied in Amherst and Mergui districts. 



Tertiary Rocks. 



Tertiary deposits are found along two belts, the one corre- 

 sponding with the present-day valleys of the 

 y " "Ran and the Kamaungthwe, and the other 



to a less extent with that of the Great Tenasserim. They have 

 been areas of depression along parallel axes, separated by a more 

 elevated barrier about 20 miles wide, through which the Tenas- 

 serim has cut its way. The Tenasserim area is as yet very imper- 

 fectly explored ami the following short account refers mainly to 

 the Ban-Kamaungthwe basin. 



On the map the Tertiaries appear as a number of disconnected 

 patches. It is not known whether these were 

 separate basins in which deposition took place 

 independently, or whether they all formed part of a continuous 

 sheet of sediments which has been broken up by slight post-Tertiary 

 earth-movements and the removal, by the present streams, of 

 material from the upraised portions. 



It is perhaps more likely that the latter is the case — that the 

 Tertiaries were accumulated in a, broad river-valloy or possibly 

 a lake, and are the remains of a more widespreading expanse than 

 their present limits would indicate. 



