Address by Prof. Sir T. H. Holland. 463 



range up to about the end of Permian times ; while the third set alTects the 

 younger and Upper Gondwanas of about Ehsetic or Liassic age. Although 

 the present topography of the country follows closely the outlines of the geo- 

 logical formations, it is clear from the work of the Geological Survey of India 

 that these outlines were determined in Mesozoic times, and that the movements 

 which formed the latest series of faults were but continuations of those which 

 manifested themselves in Paleeozoic times. According to ?\Ir. J. G. Medlicott, 

 the field data showed ' ' that a tendency to yield in general east and west or 

 more clearly north-east and south-west lines existed in this great area from the 

 remote period of the Vindhyan fault ".^ The author of the memoir and map 

 on this area was certainly not suspicious of the ideas of which I am now un- 

 burdening my mind ; on the contrary, he attempted and, with apologies, failed 

 to reconcile his facts to views then being pushed by the weight of ' authority ' 

 in Europe. This was not the last time that facts established in India were 

 found (to use a field geologist's term) unconformably to lie on a basement of 

 geological orthodoxy as determined by authority in Europe. It is important 

 to notice that the series of faults referred to in the central parts of India are 

 not mere local dislocations, but have a general trend for more than 250 miles. 



A fault must be younger, naturally, than the strata which it traverses, but 

 how much younger can seldom be determined. Intrusive rocks of known age are 

 thus often more useful in indicating the age of the fissures through which they 

 have been injected, and consequently the dykes which were formed at the time 

 of the eruption of the great Deccan Trap give another clue to the direction 

 of stresses at this critical time, that is, towards the end of the Cretaceous 

 period, when the northerly creep had reached its maximum, just before Gond- 

 wanaland was broken up. If, now, we turn to the geological maps of the 

 northtrn part of Central India, the Central Provinces, and Bengal, we find that 

 the old Vindhyan rocks of the Narbada Valley were injected with hundreds of 

 trap-dykes which show a general W.S.W.-E.N.E. trend, and thus parallel to 

 the normal tension faults, which we know were formed during the periods pre- 

 ceding the outburst of the Deccan Trap. This general trend of faults and 

 basic dykes is indicated on many of the published geological maps of India 

 covering the northern part of the peninsula, including Ball's maps of the 

 Eamgarh and Bokaro Coal-fields" and of the Hutar Coal-field,^ Hughes' Eewa 

 Gondwana basin,'* .Jones' southern coal-fields of the Satpura basin,* and 

 Oldham's general map of the Son Valley.*" 



We see, then, that the development of fissures with a general east-west 

 trend in the northern part of Gondwanaland culminated at the end of the 

 Cretaceous period, when they extended down, probably, to the basic magma 

 lying below the crust either in a molten state or in a state that would result 

 in fluxion on the relief of pressure. That the molten material came to the 

 surface in a superheated and liquid condition is shown by the way in which 

 it has spread out in horizontal sheets over such enormous areas. Throughout 

 this great expanse of lava there are no certain signs of volcanic centres, no 

 conical slopes around volcanic necks ; and one might travel for more than 

 400 miles from Poena to Nagpur over sheets of lava which are still practically 

 horizontal. There is nothing exactly like this to be seen elsewhere to-day. 

 The nearest approach to it is among the Hawaiian calderas, where the highly 

 mobile basic lavas also show the characters of superfusion, glowing, according 

 to J. D. Dana,^ with a white heat, that is, at a temperature not less than about 

 1,300=^ C. 



Mellard Eeade has pointed out that the Earth's crust is under conditions of 

 stress analogous to those of a bent beam, with, at a certain depth, a " level of 



1 Mem. Geol. Surv. Ind., vol. ii, pt. ii, p. 256, 1860. 



^ Ibid., vol. vi, pt. ii. 



^ Ibid., vol. XV. 



* Ibid., vol. xxi, pt. iii. 



" Ibid., vol. xxiv. 



^ Ibid., vol. xxxi, pt. i. 



"^ Characteristics of Volcanoes, 1891, p. 200. 



