194 VREDKNBURG: SKETCH OF BALUCHISTAN DESERT, 



Chapter III.— GEOLOGICAL DIVISIONS. 



Section i.— Introduction— .Maps. 



I have already mentioned the principal kinds of rocks met with 

 in this region. The marine strata are sediments extending in age 

 from upper cretaceous to upper eocene and interbedded with a 

 large proportion of volcanic rocks. These together with numerous 

 igneous intrusions contribute to form the greatest portion of the hill 

 masses. Considerable areas are occupied by Siwalik strata, and in 

 many regions the older rocks are entirely concealed by modern 

 alluvium and sand dunes. Lastly, in the western portion of the 

 country examined there are several recent volcanoes, one of which 

 still shows signs of activity. 



The marine sediments, notwithstanding the enormous extent of 

 their outcrop, belong to little more than one geological division. Of 

 the cretaceous, on the one hand, only the uppermost beds are seen, 

 and, on the other hand, the newest beds observed contain fossils of 

 upper eocene age. The general absence of fossils and the discon- 

 nected nature of my observations have not allowed me to draw any 

 divisions through this series. It would have been interesting to make 

 out a succession of horizons and describe them in succession, but 

 there are so many rocks whose exact age cannot be determined that 

 it is impossible to follow such a plan. Petrographical differences do 

 not constitute any guide, for rocks containing fossils that belong to 

 widely different faunas are petrologically very similar. I propose, 

 therefore, to give a few general remarks upon each of the classes of 

 rocks met with, the marine strata, and their accompanying volcanic 

 products, the igneous intrusions, the Siwaliks, and finally the recent 

 deposits. Then I intend to describe the details met with as I pro- 

 ceeded along the line of march. The recent volcanoes forming as 

 they do an adventitious group without any intimate connection 

 with the other rocks will be described separately. 

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