CHAPTER XVII 



UPTHRUST MARINE MUDS AND RAISED 



BEACHES 



As pointed out by Mi-. C. Hedley, the expression " raised beach " is somewhat of 

 a misnomer as appUed to the geologically recent uplifted parts of the ocean floor 

 of Antarctica. Mr. James Murray, the biologist of our expedition, has explained 

 that shell beaches, like those developed in temperate and tropical latitudes, cannot 

 form in the Antarctic on account of the grinding action of ice-floes and the grating 

 of small bergs over the bottom of the sea. The deposits about to be described are 

 considered by Messrs. Chapman and Hedley to have been ujDheaved from depths 

 of as much as 100 fathoms. They may be described therefore rather as raised 

 marine muds than as I'aised beaches. 



Raised marine muds were observed at three distinct localities on the western 

 and south-western slopes of Ross Island, also at Dry Valley near New Harbour, just 

 north of the mouth of the Ferrar Glacier, also near the foot of Backstairs Passage 

 near the Drygalski Piedmont, between Mount Crummer and Mount Gerlache. The 

 position of the two chief deposits on the west slopes of Ross Island are shown on 

 the detailed geological map of the Cape Royds area. 



1. Upthrust Marine Mud or Raised Beach near Backstairs Passage, south- 

 east of Mount Larsen. This deposit Is formed of a bluish-grey calcareous clay or 

 ooze, in which large foraminifera and echinoid spines are conspicuous. It also con- 

 tains numerous worm-tubes of serpulid origin, polyzoa represented by Lepralia 

 cheilodon (McGillivray), a well-preserved brachiopod, Liothyrina antarctica (Block- 

 mann), numerous sponge spicules, valves of a chiton, species undetermined, as well 

 as the following, determined by Mr. C. Hedley : Pecten Colhecki (Smith), Thracia 

 'meridio7ialis (Smith), Valvatella crehrilirulata (Smith), Lovenella antarctica 

 (Smith), Lepeta antarctica (Smith). Mr. Chapman, who has described the ostracods 

 and foraminifera, concludes that the deposit may have been formed at a depth 

 certainly of about 100 fathoms, if not greater. He records twenty-four species of 

 foraminifera, twelve of which have already been noted from the sub-antarctic islands 

 of New Zealand. A solitary coral and a large compound siliceous sponge were also 

 obtained from this deposit ; the latter is of special interest in reference to its mode 

 of occurrence. 



As regards the general appearance of this raised deposit, it is of the nature of a 



