TRANSACTIONS OF SECTION C. 757 



principally within the Tertiary era, and mainly within the latter half of it. In 

 lact, none of the mountains which hound the Indian Empire appear to have existed 

 in anything like their present form or size at the commencement of the Tertiary 

 era. 



The Indo-Gangetic alluvium occupies a zone of depression formed entirely 

 within the Tertiary era concomitantly with the elevation of the extra- Peninsular 

 ranges. The surface deposits are all Recent or Pleistocene in age, but the occur- 

 rence of extinct mammals in the alluvium of the Jumna, some of which are 

 identical with those of the uppermost Siwalik heds, points to an Upper Tertiary 

 age of the deeper seated deposits of the Gangetic alluvium, whose thickness has 

 been proved to reach 1,300 feet under Lucknow. 



The Peninsular area differs from the extra-Peninsular in having been dry land 

 since the close of the Paleozoic era, and in the very small amount of disturbance 

 the rocks have undergone during this period. Two of its main geographical 

 features appear to be of very ancient date. On the north-west the Aravalli range 

 of the present day is the mere wreck of a mountain range whose elevation was 

 completed in the Vindhyan period ; the exact age of this system cannot be deter- 

 mined, as no fossils have been found in it, but it is certainly pre-Carboniferous, 

 though probably not much older than Devonian. On the east the present coast- 

 line appears to have been approximately determined about the same period, and 

 the manner in which the small patches of marine deposits found on the east coast 

 thin out against the older rocks shows that throughout the Secondary era the sea 

 could never have extended much west of the present coast, though dry land may 

 at times have extended further to the east. 



The west coast appears to be of much more recent origin. Throughout the 

 Secondary era there seems to have been a more or less continuous land connection 

 between Southern India and South Africa ; at the close of the Secondary era, 

 however, this was broken up, the present west coast defined, and the range of the 

 Western Ghats elevated. The palreontological evidence of the former connection 

 between India and Africa is very complete, and, besides this, there is a very re- 

 markable analogy between the geology of the two regions. The Karoo series of 

 the interior of South Africa and the Uitenhage series of the coast are represented 

 in India physically, stratigraphically, and palreontologically by the Gondwanas of 

 the interior of the Peninsula and the Upper Gondwana outliers of the east coast. 



So far reference has only been made to the most important features of what is 

 known, and it will be well now to point out briefly what has still to be done. 

 Within the thoroughly settled districts of the Peninsula large areas have been left 

 uncoloured because absolutely nothing is known of them, and even in the area 

 which has been coloured much remains to be done. The vast area coloured with 

 one uniform tint of pink contains many v^arieties of rock, and at least two — probably 

 many more — successive systems of deposits, besides intrusive and eruptive rocks of 

 the most diverse kinds. The succession and correlation of the various rock systems 

 which are classed as Transition, Ouddapah, and Vindhyan have yet to be esta- 

 blished ; while the relation between the Upper and Lower Gondwana beds and the 

 proper classification of this great series of river deposits, ranging in age from Car- 

 boniferous to Cretaceous, have still to be worked out. 



In the extra- Peninsular area the Himalayas have much information to yield, 

 especially as regards the zonal distribution of the Siwalik fauna, and the sequence 

 and correlation of the great series of as yet unfossiliferous slates and limestones of 

 the North-west Himalayas. On the east our newly-acquired province of Burma, 

 besides almost the whole of Assam, has to be surveyed, and the very fine series 

 of Tertiary rocks and the economically important mineral deposits have to be 

 examined in detail. 



If fact, the most pressing need of the immediate future is not so much the 

 exploration and imperfect examination of new regions as the completion and 

 filling up of gaps in our knowledge of the geology of the land which lies within 

 ouv frontier. 



