62 Prof. J. W. Gregory — Geological Relations of S. Georgia. 



iN'ordenskjold kindly tells me that this fossil has been identified as 

 a Posido7iomya and as probably Mesozoic. This conclusion recalls 

 Darwin's view of the Cretaceous age of the similar clay-slates of 

 Tierra del Fuego. 



The Posidonomya was found in phyllitic rocks in Cumberland Bay, 

 and further to the west, on the same part of the northern coast, 

 Dr. Konig, of the German Antarctic Expedition under Lieutenant 

 Filchner, foiand a fossil which Dr. Fritz Heim, the geologist of the 

 expedition, identified as part of an Ammonite. The fossil is badly 

 preserved ; it has been submitted by Professor Salomon to Professor 

 Pompeckj, who says that it maij he an Acanthoceras and may be 

 ' Kreide '. Professor Salomon has kindly given us the opportunities 

 to see this specimen in Glasgow, and its matrix agrees closely with 

 the rocks collected from tlie same locality by Mr. Ferguson ; they 

 come from the middle part of the Cumberland Bay Series and are 

 largely composed of volcanic debris. 



The preliminary paper in which Dr. Heim ' has announced the 

 discovery of this fossil shows that South Georgia contains a varied 

 series of rocks ; for in addition to the slates > and tuffs described by 

 Thiirach, Dr. Heim records, from widely separated localities, boulders 

 of granitic and dioritic rocks and aplite ; and he discovered at the 

 south-eastern end of the island a centre of ' alt-vulkanischer ' basic 

 eruptives, including diabase and melaphyre-like rocks. On the 

 general conclusions as to the relations of South Georgia, Dr. Heim 

 remarks that the rocks are not sufficient to prove that the island 

 belongs to the folded mountain system of the Andes and Antarctic 

 Andes. Nevertheless, he adds, the appearance of the folded Mesozoic 

 beds, the presence of the tuffs and basic eruptives, and the characters 

 of the associated plutonic rocks in South Georgia and Grahamland 

 form a striking geological reflection of the Patagonian Cordillera. 



Since the visit of the German Antarctic Expedition South Georgia 

 has been further examined owing to the public- spirited generosity of 

 Th. Salvesen, Esq., of Leith, by Mr. D. Ferguson, whose work throws 

 much fresh light on the geology of the island and some doubt on 

 the generally accepted view as to its relations. He found in the 

 slates and limestones of Stromness Bay a number of fossils, whicli 

 have, however, been so crushed that their identification is a matter 

 of extreme difficulty. The fossils include some dichotomous stems 

 which may be dismissed as fucoids. The most definite specimens 

 are some vertical sections through what appear to be massive 

 cylindrical tabulate corals. The best specimen is 45 mm. wide and 

 70 mm. long ; it has thick walls, no septa, and is crossed by thirty 

 tabulae in a length of 60 mm. The certain generic determination 

 of the fossil is impossible. Its shape was obviously cylindrical; it 

 is above the average size of simple corals ; its walls are thick ; it 

 has no septa extending far into the interior, but there are traces 

 of septal structure in the wall; and it has no internal vesicular 

 tissue, but many strong tabulae. This combination of characters is 

 also met with in the coral Omphijma. If the fossil be a coral, it 



^ F. Heim, " Geologiscbe Beobachtungen iiber Siid-Georgien " : Zeit. Ges. 

 Erdk. Berlin, 1912, No. 6, pp. 451-6. 



