ANTARCTIC ADVENTURE AND RESEARCH 



may represent intrusions into the limestone series, and 

 may have given rise to the chondrodites mentioned 

 earHer. 



David and Priestley believe these rocks to be pre- 

 Cambrian in age, since the Cambrian limestone of the 

 Beardmore Glacier with Archeocyathus is quite un- 

 metamorphosed and therefore presumably younger 

 than the crystalline limestones. Further, the granu- 

 lites are like those of Brittany, which are considered 

 to be pre-Cambrian, and are so like the series from 

 South Australia that they may be considered to be of 

 the same pre-Cambrian age. Near Terra Nova Bay 

 (latitude 75° S.) Priestley found rocks of much the 

 same type, mostly in moraines but sometimes in situ. 

 It is clear that the glaciers cut through a basement 

 series of metamorphic rocks, chiefly biotite-gneiss, 

 granulites, or graphitic mica-schists. 



Slate Graywackes. — In the region of Robertson Bay, 

 near Cape Adare, in latitude 69° S. Priestley has de- 

 scribed a series of sediments which differ very con- 

 siderably from those found so far in other parts of 

 the Ross Sea area, or even in Mawson's area to the 

 northwest. The oldest rocks near Cape Adare appear 

 to be a series of sediments ranging from fine-grained 

 slates to a coarse graywacke.^ They are of a greenish- 

 gray color. The main cleavage lines run north and 

 south, and the bedding is indistinct. The series is 

 thrown into anticlines and synclines, the axes of which 

 are approximately meridional, and has been observed 



8 Graywacke is a cemented aggregate of small fragments of 

 quartz, slate, etc. 



94 



