MARINE DEPOSITS OF PATAGONIA 185 



indicate the presence of large boulders or the outcrop of rock through the deposits. 

 St. WS 825 in lat. 50 50' S and long. 57 15' 15" W, with 35 per cent large fragments, 

 lies on the edge of the continental shelf to the north-east of the Falkland Islands. 



(II) VERY COARSE GRAVEL (Plate V) 

 (Material under 15 mm. and over 10 mm. in diameter) 



The distribution of very coarse gravel follows closely that of the large fragments, but 

 is rather more widely spread. The grade does not occur in the Gulf of San Jorge, but to 

 the north a small patch lies close to the coast. The large-fragment ground off Cape 

 Tres Puntas and Point Deseado carries up to 9 per cent of very coarse gravel, and the 

 similar ground between it and the Jason Islands carries up to 13 per cent. Two southerly 

 extensions of the latter occur, one carrying up to 8 per cent of the grade, the other 

 1 per cent. 



The south coasts of the Falkland Islands are bordered by an area carrying a small 

 proportion of very coarse gravel, and an extension of the area into deeper water occurs 

 towards the south-west. On the edge of the continental shelf to the north-east of the 

 islands a patch occurs bearing up to 6 per cent of very coarse gravel : this patch coincides 

 with the area of large fragments in the same place. The Burdwood Bank shows an area 

 of this grade extending into deep water towards the north-west, but the grade is absent 

 from the northern slope. 



Two small patches of very coarse gravel occur between the Falkland Islands and the 

 entrance of the Strait of Magellan, whilst another occurs off the coast of Tierra del 

 Fuego south of the entrance of the Strait. 



Very coarse gravel occurs elsewhere in the region only in isolated patches, par- 

 ticularly towards the edge of the continental shelf north of the Falkland Islands. 



(Ill) COARSE GRAVEL (Plate VI) 

 (Material under 10 mm. and over 5 mm. in diameter) 



This grade occurs over a large part of the region under consideration. A line drawn 

 from Cape San Diego to a point in lat. 50 S long. 6o° W and thence to Cape Tres 

 Puntas approximately encloses to the westward the main area of distribution of coarse 

 gravel. A bay in the northern part of this area is free from the grade, as is also a coastal 

 strip extending from Desvelos Bay to Point Gallegos. This large area of coarse gravel 

 does not extend as far east as the Falkland Islands, but west of the islands it carries a 

 higher proportion, up to 18 per cent of the grade, than over the rest of the area where it 

 does not carry more than 5 per cent. North of the area of coarse gravel just described 

 the grade occurs only as isolated patches, small ones in the middle of the continental 

 shelf and at the extreme north, a larger one at the edge of deeper water, while the largest 

 is a coastal strip north of the Gulf of San Jorge. 



Coarse gravel forms up to 8 per cent of the deposits on the rough patch at the edge 

 of deep water north-east of the Falkland Islands. It also occurs in small quantity on 

 the rough ground, south of the Falkland Islands, which extends in a south-westerly 



