ANTARCTIC GEOLOGY 323 



ments recalling the Beacon sandstone formation. In 76° 27' S. and 

 38° 43' W. a red grit boulder of over 70 pounds was recovered as well 

 as fossiliferous limestone, but unfortunately these specimens were 

 lost with the Endurance later in the expedition. Other rocks collected 

 were dolerite, hornblende granite, shale, and metamorphic rocks, 

 including garnetiferous gneiss and mica schist. Owing to the clock- 

 wise motion of the Weddell Sea ice, there is good reason to believe 

 that the transported material had its source to the east. An important 

 find was the recovery of a fragment of Archaeocyathus limestone 

 by the Scotia expedition in 62° 10' S. and 41° 20' W., at a depth of 

 1775 fathoms. 



The Graham Land sector of the American Quadrant is better 

 known. Morphologically Graham Land stands as a mirror image of 

 Patagonia across the deep water of Drake Strait. The festoon of 

 islands of western Patagonia is reflected in the island archipelago of 

 its western border. This symmetry is furthermore revealed in geolog- 

 ical architecture, for the geological structure of Patagonia is repeated 

 in the Graham Land peninsula. The region forms an ice-covered high- 

 land with eminences rising to a height of 6000-8000 feet. Of this 

 highland the western zone consists for the most part of great plutonic 

 intrusions, the outer rim partly submerged in an archipelago with 

 recent volcanic outpourings, while the eastern tract is capped by 

 horizontal Cretaceous and Tertiary strata covered by basic volcanic 

 rocks. On the northwest coast the highest latitude reached by 

 Charcot was 70° 30' S., and the land (Charcot Land) was seen to 

 continue to the southwest of Alexander I Land. The western zone of 

 Graham Land and its outlying archipelago is believed to consist 

 largely of a calc-alkaline series of granodiorites, adamellites, diorites, 

 gabbros, and serpentine. A folded series of mudstones, slates, andes- 

 ites, and porphyry breccias, tentatively referred to the Mesozoic 

 (? Jurassic), is intruded by quartz diorites and gabbro. Probably 

 an older basement series is seen in a group of metamorphosed sedi- 

 ments and gneisses not yet clearly differentiated. According to 

 Nordenskjold, the plutonic series forming the dominant rocks of the 

 region shows marked chemical and petrographical similarity to the 

 plutonic massifs of the South American Cordillera. 



At Hope Bay at the extreme northeastern end of Graham Land 

 Jurassic graywackes and plant-bearing shales with a rich flora, in- 

 cluding Otozamites, Thinnfeldia, Sphenopteris , etc., and covered by 

 porphyry and porphyry tufifs, are folded and metamorphosed. They 

 occur in close proximity to the plutonic rocks, but the conglomerates 

 of the Jurassic series are free from pebbles of these intrusions. It is 

 probable, though not actually proved, that, like the Patagonian 

 plutonic series, the granite-gabbro series is of post-Jurassic age. 

 The Tertiary lavas on either side of the Graham Land ridge at James 



