MARINE DEPOSITS OF PATAGONIA 187 



continental shelf westerly of Point Deseado, while another adjoins the area free from 

 the grade off Point Gallegos. 



Fine gravel is nowhere present in greater amount than 12 per cent of the deposits 

 and is both widely and evenly distributed over most of the continental shelf. 



(VI) COARSE SAND (Plate IX) 

 (Particles over 1 mm. and under 1-5 mm. in diameter) 



This grade occurs in small amount over nearly the whole region examined, forming 

 not more than 6 per cent of the deposits practically everywhere. It is absent from the 

 Gulf of San Jorge and the area eastward of it, from the coastal belt stretching from Point 

 Deseado to Point Gallegos, from two areas on the continental slope, one north-east of 

 the Falkland Islands and the other east of Point Deseado, and from two small patches 

 near the outer edge of the continental shelf east of the Gulf of San Jorge. 



Coarse sand occurs in larger amount, up to 12 per cent of the deposits, off the southern 

 entrance of Falkland Sound, off the west of West Falkland Island, and on the coarse 

 patch north-east of the Falkland Islands. It also occurs on the northern slope of the 

 Burdwood Bank, and in two isolated patches, one about 80 miles east of the entrance of 

 the Strait of Magellan and the other about 40 miles east of Point Gallegos. 



(VII) MEDIUM SAND (Plate X) 

 (Particles over 0-5 mm. and under 1 mm. in diameter) 



Medium sand occurs in much larger amount than any of the preceding grades in 

 nearly every part of the region examined. It is absent only from the Gulf of San Jorge 

 and the coastal belt running from Point Deseado to Point Gallegos, and from a patch 

 on the continental slope in lat. 49 42' S, long. 54 14' 30" W. Over most of the re- 

 mainder of the region it occurs in amounts forming up to 10 per cent of the deposits. 

 A large ground extending eastward nearly to long. 64 W from the coast between Point 

 Gallegos and the Strait of Magellan carries a proportion up to 37 per cent towards its 

 eastern end, while a smaller area to the south-east bears up to 15 per cent. A belt round 

 the western shores of West Falkland Island carries amounts up to 36 per cent, while a 

 patch south of East Falkland Island carries 28 per cent of the grade. The rough patch 

 to the north-east of the Falkland Islands on the continental slope carries 22 per cent, 

 while the northern slope of the Burdwood Bank carries 29 per cent of this grade. Five 

 small patches scattered to the north-west of the Falkland Islands, between them and 

 Point Deseado, carry amounts up to 77 per cent, and are the only places in the northern 

 part of the region with more than 10 per cent of medium sand in the deposits. 



(VIII) FINE SAND (Plate XI) 

 (Particles over o-i mm. and under 0-5 mm. in diameter) 



Fine sand is the characteristic component of the bottom deposits of the whole region 

 and occurs everywhere, usually in large amounts, forming 76-90 per cent of the 

 deposits over more than half the region. It forms 76-90 per cent of the deposits of the 

 continental shelf north of lat. 50 S, with the exception of (i) that part west of long. 



