302 JR. D. Oldham — Probable Changes of Latitude. 



cretionary nodules formed in situ, has been declared to be Carboni- 

 ferous aud contemporaneous with the Talchir group of the peninsula. 1 

 This last supposition may or may not be true ; but, as I have already 

 explained, there can be no manner of doubt that the fossils occur in 

 transported pebbles, and are consequently valueless for determining 

 the horuotaxis of this group. 2 



Besides the Olive group, Mr. Wynne has desci'ibed glacial boulder 

 beds in the Speckled and Purple Sandstone groups of the Salt Eange, 3 

 and in the Trans-Indus extension of that range glacial boulder beds 4 

 crop out from below a limestone of Upper Carboniferous age. 



In the peninsula we know of but a single group of glacial beds, 

 but it is not difficult to account for the difference ; for, while the 

 extra-peninsular area has yielded an extensive and fairly complete 

 series of marine sedimentary beds, these are conspicuously absent in 

 the peninsular area. The limestone of the Vindhyan series and the 

 Talchir group of the Gondwanas maybe of marine origin ; but, apart 

 from them, the rocks of the peninsula, where not of volcanic or meta- 

 morphic origin, are almost entirely river deposits ; so that the absence 

 of any trace of more than a single glacial period is more than 

 possibly due to their records having been destroyed. 



These facts are in themselves sufficiently striking and difficult to 

 reconcile with some of the generally accepted hypotheses of geology, 

 but they are emphasized by a detailed examination of two of the 

 instances. To take the Olive group of the Salt Eange, boulders and 

 pebbles showing glacial striae are abundant, and it is by no means 

 unusual to find an irregular-shaped mass of hard crystalline rock 

 with one, and occasionally more than one, of its surfaces ground into 

 a flat facet, smoothed, polished, and striated with nearly parallel 

 striaa. 



In the case of the Talchir boulder bed of the peninsula, it has been 

 usual to ascribe its origin to winter coast ice ; but the flattened 

 boulders of the Olive group indicate a more prolonged wearing, a 

 greater pressure and a greater constancy of direction of motion than 

 can be accounted for on this supposition. We are consequently 

 driven to the hypothesis that they have been ground by a glacier 

 which descended to the sea-level and gave off icebergs there. 



Now the majority of these boulders consists of rocks of recog- 

 nizably peninsular types, not a few are of a very highly siliceous 

 felsite porphyry, which is at present only known in the Eajputana 

 Desert, and not a single fragment has yet been found which can be 

 declared to be derived from a Himalayan source. Besides this, the 

 pebble band from which the Co mJcm"<® referred to above were obtained 

 exhibits certain peculiarities of distribution, which indicate that 

 the source from which the pebbles were derived lay to the south- 

 wards. 5 



1 Records Geological Survey of India, vol. xix. p. 22. 



2 Ibid. p. ] 27, et sequel. 



3 Memoirs Geological Survey of India, vol. xiv. pp. 87, 93, 214, etc. 



4 Ibid. vol. xvii. p. 239. 



5 Records Geological Survey of India, vol. xix. p. 129. 



