MARINE DEPOSITS OF PATAGONIA i 79 



deep (section A, Fig. i), while the southern part is mostly 100-200 m. deep (sections B, 

 C, Fig. 1). The 100 m. contour round the Falkland Islands lies close to the coast so 

 that the shores of the islands descend comparatively steeply to the level of the continental 

 shelf, which on the east, south and west coasts of the islands is narrow. 



Outside the limit of the continental shelf at 200 m. the bottom north of lat. 46 20' S 

 runs steeply down to depths of 2000 m. and more (section A, Fig. 1). From lat. 46 20' 

 to 50 S the 200 m. contour lies farther to the west and the seaward slope of the shelf 

 is more gentle to 500 m., below which it dips steeply (sections B, C, Fig. 1). South of 

 lat. 50 S the Falkland Islands lie close to the edge of the continental shelf and the steep 

 slope from 300 m. downwards is near the coast (section D, Fig. 1). 



The gradient of the continental shelf from the coast to the continental slope is very 

 gentle: in lat. 43 S it is only 1 in 2690 for a distance of 160 miles from the coast out to 

 the 100 m. line, and in lat. 50 S it is 1 in 3150 for a distance of 340 miles from the coast 

 out to the 200 m. line. 



DISTRIBUTION OF SAMPLING 



The area of the region from which samples have been examined amounts to about 

 185,000 square miles, excluding the 6500 square miles of the Falkland Islands. The 

 samples number 112 and are fairly evenly distributed, so that each sample represents 

 on the chart about 1650 square miles of the sea-bottom. This distribution of sampling 

 cannot give any detailed picture of the sea-bottom, but as the region is characterized by 

 great uniformity over large areas the outlines of the nature and configuration of the 

 bottom as sketched in this report may be taken as being approximately correct. Plate II 

 shows the positions of all the stations from which bottom samples were received. 



COLLECTION OF SAMPLES 



The samples were collected with the conical dredge, which has a mouth 18 in. in 

 diameter and a canvas bag. The dredge has a heavy metal lip which cuts into the bottom 

 so that a large sample is collected from some 6 in. to 1 ft. below the surface of the 

 ground. The dredge is described in detail by Borley (1923). 



When the dredge is emptied on deck the sample preserved is taken from the middle 

 of the mass of material turned out, so that the portion of the dredging that was upper- 

 most during hauling, and consequently may have had some of the finer deposits washed 

 out, is rejected. The samples were placed in wide-mouthed screw-capped jars and 

 preserved in spirit. 



A haul with the conical dredge was taken as a routine at nearly every station made 

 by the R.R.S. 'William Scoresby' during her survey of the region surrounding the 

 Falkland Islands, and the samples then obtained are the collection forming the subject 

 of this investigation. 



