SUMMARY 317 



Ross Island, Snow Hill Island, Seymour Island, &c. ; but the fact must not be over- 

 looked here that the above-mentioned localities occupy a comparatively small 

 superficial area, and that if the Antarctic Horst is a continuation of the Graham 

 Land Antarctic Andes, and if these Cretaceous rocks are developed on its western 

 side, that is, on the side of the horst nearest to Africa, they would be faulted out of 

 sight, in South Victoria Land, under the thick covering of the inland ice on the 

 west side of the great horst. It Is possible that some outcrop of them might occur 

 along the coast-line recently discovered by Lieutenant Pennell in the Terra Nova 

 of the British Antarctic Expedition of 1910-12.* 



If now we examine the points of resemblance between the horst of South Victoria 

 Land and the Andes of West Antarctica, the following features at once enforce them- 

 selves on our attention : — In the plan of the earth, as a result of the tendency of the 

 earth's crust to contract in two directions, more or less at right angles to one another, 

 the dominant type of fold and fracture is S shaped. An S-shaped fold of this kind 

 on a grand scale is formed by the Carpathians, Alps, Apennines, Tunisian, and Atlas 

 Mountains, with the trend lines which cross the Straits of Gibraltar, and terminate in 

 the Betic Cordillera. Again in the Burmese arcs, in relation to the great folds of 

 the Himalayas, those of the Salt Range, the Suliman Mountains, and the ranges of 

 Beluchistan, Iran, and the Zagros Hills, we have another example of gigantic 

 tectonic features built on an S-shaped plan. 



As pointed out by one of the authors")" in a recent paper, the main trend lines 

 of Australia are distinctly S shaped. The same structure is to be seen in Central 

 America and South America, and from Patagonia and Tierra del Fuego one sees 

 possible evidence of an immense loop swinging far to the east from near Cape Horn 

 towards South Georgia, and perhaps even the Sandwich Group, returning westwards 

 through the South Orkneys to Graham Land.J 



As regards Graham Land, all the great authorities on the structure of that region 

 — tectonic, petrographical, and paloeontological — are agreed that the rocks of that 

 plateau, which constitutes Terre Louis Philippe, Palmer Land, Danco Land, Graham 

 Land, Terre Loubet Bay, Terre Fallieres, and King Oscar II. Land, show that it is 

 undoubtedly part of the same unit as the South American Andes. These Antarctic 

 Andes of West Antarctica show evidence of very heavy downthrow faults towards 

 the north-west, in the direction of Bransfield Strait, Gerlache Channel, and the archi- 

 pelago recently discovered and described by Dr. Charcot's Expedition to the north 

 and south of Bale Marguerite including Terre Charcot. Thei'e can be little doubt 

 that the South Shetlands, the Palmer Archipelago, the Biscoe Islands, together with 



* Mr. C. T. Madigan, of Dr. Mawson's Australasian Antarctic Expedition, has lately discovered 

 sandstones and coaly shales about 250 miles east of Dr. Mawson's headquarters in Ad6lie Land. The.se 

 rocks are probably to be referred to the Beacon Sandstone. 



t Joui-. and Proc. Roy. Soc. N.S.W., vol. slv. pp. 1-60, Pi-esidential Address by T. W. E. David. 



\ Suess cautions us against necessarily considering this to be a continuous loop. 



2 S 



