270 SUPERFICIAL DEPOSITS 



by glacier ice. There can be no doubt that the ice underlying the Cape Barne 



raised beach is a relic of the Great Ice Barrier. 



Fig. 63 below shows the theoretical structure of the Drygalski-Larsen-Reeves 

 Piedmont ice, the section being taken from south-east to north-west, nearly at right 

 angles to the " rib " of the Larsen Glacier. The thrust has come chiefly from the 

 direction of the great Drygalski Glacier " rib," which has transmitted its thrust, 

 not of course through the two "open channels" to its left (these are shear planes), 

 but through areas nearer the shore-line, where the shear plane walls are firmly in 

 contact with one another. 



N.W. 



Part of Reeves I'l Piedmont ice 



Vpthrust marine muds 

 ZOPabmeseacmerefl 

 with large angular 

 blodiS of granite a 

 ^Quartz porphyry 

 \resting on ice 



Larsen Piedmont 

 m/fl neevy moraine 



S.E 



Drygalski Piedmont 



Longitudinal Scale 

 Vertical Scale. 



tsooD (600O Metres 

 400 feet 

 ~" Soo Metres 



Fig. 63. Uptkrust Marine Muds and Raised Beaches 



The following alternative explanation to the upthrust hypothesis may be 

 suggested ; — 



The region near Backstaii's Passage is one where there is a large amount of 

 moraine material either upon the ice or embedded in it. As already explained, 

 absorption of the sun's heat by blocks of rock leads to then- being so warmed up that 

 they rapidly melt their way into the ice beneath and become englacial. Thus the 

 glacier ice in the neighboui-hood of moraines becomes heavily loaded with blocks of 

 rock, and so its mean density may be so much increased that it exceeds that of sea 

 water and becomes what may be termed rock-loaded, or rock-logged. A sub- 

 mergence of the land taking place later sea-level relatively rose, and the glacier 

 ice, weighted down by its rocks, was not able to float up to the sui-face, consequently 

 for a time it formed the actual sea floor. Marine muds with the nimierous organisms 

 described were then deposited, various types like the serpulce and the incrusting 



