462 Notices of Memoirs — Australia, 1914 — 



mass of the Outer and Central Himalaya of old nnfossiliferous rock, with the 

 snow-covered crystalline peaks flanked on the north by (5) the Tibetan basin of 

 highly fossiliferous rocks formed in the great Eurasian mediterranean ocean 

 that persisted up to nearly the end of Mesozoic times. 



That these leading features in North India can hardly be without genetic 

 relationship one to another is indicated by the geological history of the area. 

 Till nearly the end of the Mesozoic era the line of crystalline, snow-covered 

 peaks now forming the Central Himalaya was not far from the shore-line 

 between Gondwanaland, stretching away to the south, and Tethys, the great 

 Eurasian ocean. Near the end of Mesozoic times there commenced the great 

 outwelling of the Deccan Trap, the remains of which, after geological ages of 

 erosion, still cover an area of 200,000 square miles, with a thickness in places 

 of nearly 5,000 feet. Immediately after the outflow of this body of basic lava, 

 greater in mass than any known eruption of the kind, the ocean flowed into 

 North- West India and projected an arm eastwards to a little beyond the point 

 at which the Ganges now emerges from the hills. Then followed the folding 

 movements that culminated in the present Himalayan Eange, the elevation 

 developing first on the Bengal side, and extending rapidly to the north-west 

 until the folds extended in a great arc for some 1,400 miles from south-east to 

 north-west. 



New streams developed on the southern face of the now rising mass, and 

 although the arm of the sea that existed in early Tertiary times became choked 

 with silt, the process of subsidence continued, and the gradually subsiding 

 depression at the foot of the hills as fast as it developed became filled with 

 silt, sand, gravel, and boulders in increasing quantities as the hills became 

 mountains and the range finally reached its present dimensions, surpassing in 

 size all other features of the kind on the face of the globe. 



Now, it is important to remember that for ages before the great outburst of 

 Deccan Trap occurred there was a continual unloading of Gondwanaland, and 

 a continual consequent overloading of the ocean bed immediately to the north ; 

 that this process went on with a gradual rise on one side and a gradual de- 

 pression on the other ; and that somewhere near and parallel to the boundary 

 line the crust must have been undergoing stresses which resulted in strain, 

 and, as I suggest, the development of those fissures that let loose the floods 

 of Deccan Trap and brought to an end the delicate isostatic balance. 



During the secular subsidence of the northern shore-line of Gondwanaland, 

 accompanied by the slow accumulation of sediment near the shore and the 

 gradual filing away of the land above sea-level, there must have been a gradual 

 creep of the crust in a northerly direction. Near the west end of the Himalayan 

 arc this movement would be towards the north-west for a j)art of the time ; 

 at the east end the creep would be towards the north-north-east and north-east. 

 Thus there would be a tendency from well back in Palteozoic times up to the 

 end of the Cretaceous period for normal faults — faults of tension — to develop 

 on the land, with a trend varying from W.S.W.-E.N.E. to W.N.W.-E.S.E. 

 across the northern part of Gondwanaland. We know nothing of the evidence 

 now pigeon-holed below the great mantle of Gangetic alluvium, while the 

 records of the Himalayan region have been masked or destroyed by later 

 foldings. But in the stratified rocks lying just south of the southern margin of 

 the great alluvial belt we find a common tendency for faults to strike in this way 

 across the present peninsula of India. These faults have, for instance, marked 

 out the great belt of coal-fields stretching for some 200 miles from east to west 

 in the Damuda Valley. On this, the east side of India, the fractures of tension 

 have a general trend of W.N.W.-E.S.E. We know that these faults are later 

 than the Permian period, but some of them certainly were not much later. 



If we now go westwards across the Central Provinces and Central India and 

 into the eastern part of the Bombay Presidency, we find records of this kind 

 still more strikingly preserved ; for where the Gondwana rocks, ranging from 

 Permo-Carboniferous to Liassic in age, rest on the much older Vindhyan Series, 

 we find three main series of these faults. One series was developed before 

 Permo-Carbonilerous times ; another traverses the Lower Gondwanas, which 



