THE METAMORPHIC ROCKS OF ADELIE LAND. 



SECTION I. 



By F. L. STILLWELL, D.Sc. (Geologist to the Australasian Antarctic Expedition), 



UmvusaiTY OF MELBOURNE. 



INTRODUCTION. 



Adelie Land is a portion of the Antarctic Continent which lies in the region 

 surrounding Long. 143 and Lat. 67. It consists for the most part of a huge ice-covered 

 plateau which rises rather steeply from the coast and reaches a height of over 6,000ft. 

 at 300 miles inland. It appears, at first sight from the ship, as the side of a vast dome- 

 shaped shield of ice, which descends to the ice cliffs or ice barrier on the seaward aide 

 and rises to about 1,500ft. on the southern horizon. 



The ice cliffs present a vertical face varying between 80ft. and 120ft. in height, 

 and delimits the boundary of the land ice sheet. In many cases the cliffs form the edge 

 of floating glacier tongues or marginal shelf ice, but as the Aurora traced the coast line 

 from Cape de la Motte to Commonwealth Bay, rock could be frequently seen at the 

 base of the cliffs. Yet these exposures remained quite inaccessible to us, and only 

 those outcrops which rise 100ft. or more above sea level and which break the monotonous 

 line of ice cliffs could be reached by sea or land. These latter outcrops are rare, and 

 while they can be readily seen from the ship they are only found and approached with 

 difficulty from the landward side. Rarer still are the nunataks, or islands of rock in 

 the snow fields, and our knowledge of the rocks of the hinterland remains very largely 

 dependent on the study of the glacial debris on the moraines. 



Three small rocky promontories exist along the 60-mile stretch of coast line of 

 Commonwealth Bay a broad open bay about 40 miles across the headlands. Of 

 these the middle one is Cape Denison, on which the Main Base of the Australasian 

 Antarctic Expedition was situated. The western rocks, always visible from Cape 

 Denison, form Cape Hunter. The bay is studded in the centre by the Mackellar Islands, 

 a group of low-lying islands due north of Cape Denison. East of the bay is the Cape 

 Gray Promontory, thickly fringed with the numerous small rocky islets which 

 constitute the Way Archipelago. These islets mostly lie in a 2-mile zone around the 

 edge of the ice cap, and one of the largest is Stillwell Island, on which a landing was 

 made. On the eastern side of the Cape Gray Promontory, facing Watt Bay, are the 

 rock outcrops which have been called Garnet Point and Cape Pigeon Rocks. 



Madigan Nunatak and Aurora Peak, the two remaining rock exposures dealt with 

 in this thesis, are widely separated nunataks. Madigan Nunatak is 2,400ft. above sea 

 level and lies on the ridge which gradually slopes down to Cape Gray, 18 J miles to the 



