24 GEIESBACH : RA.MKOLA AND TATAPANI COAL-FIELDS. 



But tbe main mass of the trap rocks in my survey is situated within 



Dykes and intrusive ^^^ boundaries o£ the coal-fieldj where it occurs in 



sheets of basaltic trap. ^^^ j^^,^ ^^ ^^^^^ ^^^^ intrusive sheets. Having 



reached the western extension of the basin before I finished the centre, 

 I came on large sheets of trap in Barakars, and there took it at first 

 for contemporaneous trap, owing* to the regularity of the apparently 

 interbedded sheets between strata ; but I soon found out my mistake 

 when I saw the continuation of the same traps traverse the Gondwanas 

 as enormous dykes and without any regard to the stratification or age 

 of the beds, cutting through all rocks from metamorphics to Mahadevas. 



The principal spreads of intrusive sheets are noticeable between the 

 villages of Majurdaki and Gorgi, where they have pushed between beds 

 probably of Barakar age and the overlying Mahadevas; subsequent 

 denudation has then exposed great sheets of this trap, the latter showing 

 nearly throughout a spheroidal structure. 



A similar but even larger sheet is found in the valley of denudation 

 of the Morne and tributaries, extending across the whole width of the 

 valley, covering the Barakars and loosing itself below the Mahadevas. 

 Here and there the former are exposed in patches where the trap was 

 removed by denudation, and good examples of the contact effects are 

 then shown. Towards the north this intrusive sheet is connected with 

 a dyke little less than half a mile in width, which extends in a north- 

 westerly direction beyond the Morne river and cuts through the Maha- 

 deva sandstone. 



The narrow strip of trap north of Namadhaka (5 miles north-west 

 of Maiapur), at the foot of the Kalhota hil], is probably part of the 

 intrusive sheet which is hidden by the Mahadeva sandstone of the 

 Churipat hills. 



The northern half of the basin examined is traversed by numerous 



trap dykes, most of them being situated along 

 Dykes along faults. 



faults. Some of the traps in the Nowadih sections 



(north of Damni) and of the Bhalui nullah section might be explained 



as being intrusive and repeated by faulting ; but there is clear evidence 



( 152 ) 



