GEOLOGICAL FORMATIONS. 37 



is so frequently the case in the Deccan traps. Another characteristic 

 accessory mineral, common also in the traps of 

 the Deccan and Malwa, is quartz with trihedral 

 terminations. The basaltic trap of the Laki hills is apparently of 

 subaerial origin, although it rests conformably on the marine (or 

 estuarine?) Cardita beaumonti beds; at least there is nothing in the 

 igneous bed to indicate its having consolidated otherwise than in 

 the air. 



The evidence that this band of basaltic rock is interstratified and 

 Evidence of interstra- not intrusive, is ample; throughout the whole dis- 

 location, tance the trap is found in precisely the same 

 position between the lowest beds of the Ranikot group and the highest 

 cretaceous strata, and apparently perfectly conformable to both. The 

 close resemblance in mineral character and the similarity of geological 

 position at the base of the tertiary beds show that this band must be, in 

 all probability, a thin representative of the great Deccan and Malwa 

 trap formation, and the occurrence of a second bed at a lower horizon, 

 interstratified with rocks of cretaceous age, tends strongly to confirm 

 the inference drawn from the relations of the traps to cretaceous and 

 tertiary rocks in the Narbada valley, that the great volcanic formation 

 of Western India must be classed, in part at all events, as upper 

 cretaceous. 



The Deccan and Malwa traps had already been traced as far as the 

 western portion of Cutch before their occurrence in Sind was discovered. 

 Their existence west of the Indus extends the area in which they are 

 known to occur by about 150 miles, the distance between Lakhpat, in 

 Cutch, and Ranikot, in Sind. 



3. Ranikot group. — The name of the lowest tertiary sub-division is 



derived from a hill fortress of the Sind Amirs, 

 Derivation of name. ,'-,•,■, T i * s- t -n j i 



situated in the Laki range ot hills, and known as 



Rani-jo-kot, or Ranikot, and also as Mohan-kot, from the Mohan stream, 



which traverses the fortification. The Ranikot group is much more 



extensively developed in Sind than the underlying cretaceous beds, for 



( 37 ) 



