26 GRIESBACH : EAMKOLA AND TATAPANI COAL-FIELDS. 



The dykes south of the Pipra hill continue for some distance into 

 the metamorphic rocks west of the Gondwanas, and two of them are 

 found south of Chiraikund amongst granitic rocks. 



Numbers of parallel dykes are found near the north-western boundary 

 of the Mahadevas in the neighbourhood of Naogai and Assandiah, some 

 of them penetrating into the adjoining metamorphics. In fig. 2. j)l. I, 

 1 have shown one of these long ridge-like dykes of trap south of Assan- 

 diah. They are only covered with very little soil, and the onion-like 

 structure of the trap is visible all over, and thus the presence of the trap 

 can always be detected with the greatest ease. . A long dyke (see fig. 3, 

 pi. VI) of this trap extends along the valley of the Rer, forming a 

 high and precipitous wall of nearly north-west to south-east direction. 

 It is connected in the south with the great intrusive sheets of the 

 Jajawal area shown in fig. 3, pi. V. 



Recent Deposits. 

 Before closing my description of rock-groups, I must briefly allude to 

 the enormous deposits of recent sands and clays covering, more or less, 

 the entire surface of the area examined by me. They present the greatest 

 uniformity throughout the area, and are in no way different from the 

 great alluvial deposits observed in the Palamow districts. It is mostly a 

 fine silty deposit of sands with a few partings of clay, and here and there 

 layers of pebbles from the neighbouring rocks. The greatest deposits 

 were found in the northern half of my area, in the neighbourhood of the 

 Ledho and Iria nullahs, where banks of 80 to 100 feet of them are expos- 

 ed by the rivers. They usually show beautiful examples of false bedding, 

 and here and there alternating layers of sand and pebbles. Wherever 

 exposed, they have weathered into high, almost perpendicular, cliffs, and 

 are washed out into a semblance of organ pipes. Not less common are 

 examples of pillar structure, caused by the denudation of all the sand and 

 clay, except the portion protected by capping pebbles or stones. The recent 

 deposits covering the Talchirs are remarkable in so far that they contain a 

 great deal of kunkur limestone of precisely the same character as that 

 described from Daltonganj. 

 ( 154 ) 



