DECCAN TRAP, 173 



of highly weathered earthy trap so commonly met with throughout the 

 Deccan region, for they are the result of excessive weathering, and where 

 the weathering has taken place concentrically, it is easy to find a nucleus 

 of tolerably well-preserved rock in the centre of the spheroids. This 

 variety answers to the nodular trap or wacke of older writers. The 

 basalt occurs either massively amorphous, or rudely tabular, or rudely 

 columnar, one or other of the two latter forms being most commonly 

 met with. 



The lower flows are mostly basaltic in character, the medium flows 

 are alternately basaltic and amygdaloid, and the upper are chiefly basal- 

 tic, with clayey and lateritic beds capping them. 



The lowest flows were poured out over an exceedingly rough surface, 

 Infra-trappean land consisting of gneiss or the younger metamorphic 

 rocks (Kaladgi and Bhima series) and the thin 

 local deposits described in the last chapter, which possibly represent the 

 Lameta formation of Central India. Owing to this great inequality of 

 the pre-trappean surface, it is impossible in many places to form a safe 

 opinion as to the relative position of individual beds, for the basement 

 bed in one place would correspond with a bed several hundred feet 

 above the true base at another place. The upper flows frequently over- 

 lap the lower and rest upon the higher lying parts of the older rocks. 



In the gh^t region the position of the flows is more distinct than 

 Position of the trap- further eastward, and they are seen, when care- 

 °^^" fully studied from some high and commanding 



point, to dip at a very low angle and generally to the north-east.* 

 About twenty-five or thirty miles from the edge of the ghats the dip 

 becomes more easterly in direction, and so gradual as to be hardly re- 

 cognisable by the unaided eye. The flows exposed in the Konkan show 



* The dip is too slight to be measured with a clinometer, but a calculation of the 

 difference in elevation of some of the principal trigonometrical stations which are capped 

 by outliers of one and the same bed shows the north-easterly slope to range from 9 to 23 

 feet per mile, giving a mean of 16 feet per mile. 



( 173 ) 



