ANTARCTIC ADVENTURE AND RESEARCH 



nected with the great tectonic movements of middle and 

 late Tertiary times in this portion of the globe, but no 

 fossils have been discovered of Tertiary age in the 

 Ross Sea area which might furnish an answer to this 

 question. (See Figure ii.) 



Detailed Geology in West Antarctica. — We owe to 

 Sir Edgeworth David a comprehensive discussion of 

 the geological data from this sector of Antarctica, and 

 the writer has made much use of it in the following 

 brief account. There is clear evidence of a close con- 

 nection between the rocks of Graham Land and those 

 of South America. The basement rocks contain in- 

 trusive gabbros and granodiorites which exhibit the 

 most characteristic Andean affinities. Hence they be- 

 long to the Pacific types of eruptive rock. In South 

 Georgia, which appears to arise from the submarine 

 ridge already described, the rocks are formed chiefly 

 of old schists in which no determinable fossils have 

 been found. In the South Orkneys on the same ridge, 

 Dr. Bruce's expedition discovered Ordovician grapto- 

 lites and phyllocarids. Just to the southeast of these 

 islands a specimen of Cambrian limestone containing 

 Archeo-cyathinae has been dredged, which shows that 

 Cambrian rocks must occur in the vicinity (see Figure 



7). 



Overlying these old rocks in Graham Land are strata 



of Mesozoic age which are folded mostly from west 

 to east. At Hope Bay (6^° 15' S.) beds containing a 

 rich Jurassic flora rest on coarse conglomerates which 

 in turn repose on current-bedded sandstone w^ith ob- 

 scure plant remains. Among the plants are Clado- 



104 



