CHAPTER II. 



GEOLOGY. 



The predominant rocks of the Tavoy District arc an assemblage 

 of sedimentaries, highly folded and indurated, but little metamor- 

 phosed, to which the term Mergui Scries was given by Dr. T. Oldham. 

 These are so extensively intruded by masses of granite in the form 

 of large and small bosses that the area occupied by granite outcrops 

 is nearly as great as that occupied by the Mergui Series. 



In the interior of the district are two areas of Tertiary rocks 

 deposited in tectonic basins on the surface of the Merguis, one 

 along the course of the Great Tenasserim River, and the other 

 in the broad valley occupied by the Kamaungthwe and the Ban, 

 the two rivers which join at Myitta to form the Great Tenasserim. 



In the lower portions of the valleys and along the coast, recent 

 deposits are at present accumulating, but it is only in the estuarine 

 portion of the Tavoy River and in the Heinze Basin that they 

 attain any considerable thickness or that alluvial plains of silt are 

 found. In the larger valleys patches of boulder beds and clays 

 are occasionally seen, which are newer than the Tertiaries and 

 older than the alluvials of the present day ; these may be late 

 Tertiary or sub-recent, probably the latter, and are so referred 

 to below. The Moulmein limestone, so conspicuously developed in 

 the districts to the north, has not been recognised with certainty 

 in Tavoy. 



The Mergui Series. 



The Mergui Series is essentially a formation of hardened and 



crushed shales and agglomerates, with greatly 



Lithology. subordinate quartzites, limestones and conglo. 



merates, and is characterised by monotonous uniformity of type 



over great areas and over immense thicknesses of strata measured 



across the strike. 



It is largely owing to this uniformity that it has been impossible 

 to decipher%he nature of the folding to which the Merguis have 

 been subjected, but even if distinctive horizons had been present 

 they could have been traced over very limited tracts, so difficult 



