822 THE GEOLOGICAL RELATIONS AND SOME FOSSILS OF SOUTH GEORGIA. 



Dr Bassler tells me that the opinion of himself and his colleagues is that these 

 Camarocladoid fossils " must be post-Cambrian or pre-Devonian." 



The structure of South Georgia therefore possibly includes two distinct groups 

 of rocks. The foundation may consist of Ordovician or Silurian sediments, resting 

 probably on still older rocks. If all the radiolarian jasperoids belong to the lower 

 Palseozoic, this lower group must extend into Graham Land, and the foundations 

 of South Georgia and Graham Land may be remnants of the Flabellites-Land of 

 Professor Schwarz. 



The second group apparently consists of marine Mesozoic rocks associated with 

 contemporary volcanic tuffs. Both the lower Palaeozoic and Mesozoic divisions may 

 have been disturbed by earth movements connected with the upheaval of the Andean 

 Mountain System. The evidence which connects South Georgia with the Andes has, 

 however, not been strengthened by Mr Ferguson's work, for the igneous rocks which 

 he collected are not Andean in affinity ; as Mr Tyrrell's descriptions show, they are 

 rocks of alkaline types which are prevalent in the Atlantic area. 



Moreover, there is no evidence of any Kainozoic volcanic activity in South 

 Georgia. There is an intrusive sill in the lower division of the Cumberland Bay 

 Series and evidence of volcanic activity during the deposition of the rest of the 

 Cumberland Bay Series. The south-western end of the island may contain igneous 

 rocks with Andean affinities ; but with the evidence now available the relations of 

 South Georgia and South America are problematical. At present there does not 

 seem to be adequate evidence to show whether South Georgia is a fragment of the 

 Andes, or whether the mountain loop that must once have connected Patagonia with 

 Graham Land passed west of South Georgia. 



DESCRIPTION OF PLATES. 

 Plate XCII. 



Figs. 1-8. Fossils from the lower division of the Cumberland Bay Series between Leith Harbour and 

 Nansen Harbour, South Georgia, collected by D. Ferguson, Esq. All the figures are natural size except 

 figs. 7 and 8, which are two-thirds natural size : — 



Fig. 1. Fragment of a tabulate coral allied to Omphyma . 



Fig. 2. Camarocladia, 1 



Fig. 3. Camarocladia, 1 A long-stemmed variety. 



Figs. 4-6. Camarocladia, 1 The fine-stemmed variety. 



Fig. 7. Caespitos fossil, 1 Calcareous sponge. 



Fig. 8. Buthotrephis, 1 succulens, Hall. 



Plate XCIII. 



Outlines of radiolaria from the Middle Cumberland Bay Series, Cape Pariadin, South Georgia. 

 Drawings by Dr G. J. Hinde, F.R.S. 



