66 DISCOVERY REPORTS 



Another noteworthy addition to our knowledge made by recent Discovery II expeditions is the 

 existence of several basaltic volcanoes on the north-western side of the South Shetland Islands. 

 Desolation Island, off the northern coast of Livingston Island, consists of columnar basalts of Recent 

 aspect. On M^Farlane Strait, not very far to the east, is the beautiful columnar basalt plug surmounted 

 by agglomerate of Edinburgh Hill, discovered and figured by Ferguson {op. cit. pi. i, fig. i). Then 

 again at Fort William, Coppermine Cove, on Roberts Island, the islands at the northern end of 

 Fildes Strait, and on the mainland of King George Island along Fildes Strait, fresh columnar olivine- 

 basalts were collected which probably mark the sites of Quaternary or even Recent volcanoes. All 

 these volcanic centres on the north-western side of the South Shetlands have obviously suffered 

 considerable denudation, and are therefore somewhat older than those on the Bransfield Strait side. 

 There can be no doubt but that these occurrences will be augmented in number when the geological 

 survey of the South Shetland Islands is carried out in detail. 



Finally, it is possible that the South Shetlands rest on a basement of crystalline schists and gneisses, 

 with sedimentary rocks in various stages of cataclastic metamorphism. Boulders and pebbles of these 

 rocks are numerous in shore and glacial accumulations, and among the dredged material from Bransfield 

 Strait (p. 57). Quite possibly some of this material has been derived from exposures on the South 

 Shetland Islands, although it is more probable that the bulk of it has come either from the Graham 

 Land peninsula to the south-east or from the Palmer Archipelago to the south. 



PART II. PETROGRAPHY OF ROCKS FROM THE GRAHAM LAND 

 PENINSULA AND ADELAIDE ISLAND, WEST ANTARCTICA 



INTRODUCTION 



Among the material sent me for description by the Discovery Committee during recent years I found 

 small collections of rocks from Cape Roquemaurel, Wiencke Island, and the Marin Darbel Islands, 

 as well as a large collection of stones dredged a few miles off the west coast of Adelaide Island. 

 Dr N. A. Mackintosh kindly provided me with a copy of the short geological notes he had made on 

 Cape Roquemaurel and Port Lockroy in Wiencke Island. These notes have been incorporated with 

 suitable acknowledgement in the following descriptions. The collections, especially that from Adelaide 

 Island, have proved valuable in extending our knowledge of the geology of West Antarctica, and in 

 providing confirmatory evidence in favour of previously expressed views on the relationships of 

 West Antarctic rocks with those of the southern Andes in Patagonia and Tierra del Fuego. 



PETROGRAPHY 



STATION 1490 (20 JANUARY 1935), CAPE ROQUEMAUREL, TRINITY PENINSULA, 



GRAHAM LAND 



Cape Roquemaurel is situated on the northern coast of the Trinity Peninsula, the eastern termination 

 of Graham Land, in long. 58° 30' W., lat. 63° 30' S. In his notes on this locality Dr Mackintosh 

 states that: 'The headland consists of several high rocks projecting from the ice-sheet of Trinity 

 Peninsula. On the south-west side of the outermost rock is a good boat harbour with a very small 

 beach. The rocks of the headland are said to be about 600 ft. high, and consist of a pale granite-like 

 rock traversed by conspicuous dikes of fine-grained blackish rock. On the south-west side of the head- 

 land beneath the granite (?) a yellowish brown rock could be seen for several hundred yards just 

 showing itself above the water line. This seemed to be a different kind of rock, though its structure 



