GEOLOGY. 



Ratamatia. Trap dykes are very common, and occasional 

 hills, e.g. the Kita Buru in the Saitba forest, are composed of 

 serpentine. u This monntain is strongly magnetic and clothed 

 chiefly with grass and Phoenix acaulis 1 (Kita> K.)" 



Manbhum differs in some important respects from Sing- 

 bhnm, chief of which are firstly, the considerable areas of 

 alluvial and sub-aerial deposits, among which the laterite is 

 very conspicuous, and is the first rock met with in travelling 

 westwards from Calcutta ; secondly, the extensive remains of 

 the Gondwana rocks especially in the valleys of the Damuda 

 and Baraka ; thirdly, the relatively poor development of the 

 enb-metamorphics. Metamorphic and sub-metamorphic rocks 

 are well represented, however, chiefly in the southern mountains. 

 Here also, surrounded by the sub-metamorphics, is a large area of 

 intrusive trap forming a long east and west band up to 3 miles 

 in breadth, thinning out east of the Dalma mountain and extend- 

 ing into and across the valley of the Subarnarekha into Tamar 

 (Ranchi district), and curving south to Bichia Buru in 

 Singbhum. Manbhum shows the most perfect examples of 

 the conical hills formed by the porphyritic or dome 

 gnesis. 2 



In Palamau again the metamorphic and sub-metamorphic 

 rocks compose most of the hill ranges, but in the west and 

 south-west, in the neighbourhood of the Kanhar river the 

 flat-topped hills are capped by massive sandstones and late- 

 rite. 3 In the north-western hills Biotite gneiss and a brown- 

 ish amorphous-looking or slatey rock (with a quite black 

 dull fracture, lydianstone ? ) are frequent. 4 In these hills 

 again a crystalline limestone is abundant, e.g., about Bona- 

 hatpur, where it is frequently hollowed out into cave 



1 Singbhum Working Flar, p. 2, and Appendix XIII, where the 

 r ocks in different compartments are enumerated. 



2 There is a good illustration of the Jhalda hill in Vol. XVIII of 

 the Memoirs of the Geological Survey of India. 



3 But see note on p. 10. 



4 The " lydianstone " was found chiefly between Bonahatpur and 

 MiraL 



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