3 o8 DISCOVERY REPORTS 



twenty-one samples are described, of which fifteen are diatomaceous muds, four are 

 terrigenous muds, and two are classed as sands. One of the latter (St. 195) is from a 

 depth of 391 m. in Admiralty Bay, King George Island, and the other (St. WS 481) is 

 from a depth of 453 m. on the Graham Land shelf, east of Astrolabe Island. The samples 

 of terrigenous mud are from Sts. 196, WS 312, WS 476 and WS 477, south of Martin's 

 Head, King George Island, at depths which vary from 425 to 1892 m. Most of the 

 samples of diatomaceous mud are from the centre of the depression, where the depth 

 varies between 446 m. towards the south of the traverse and 2085 m. south of King 

 George Island. While the distribution of terrigenous and diatomaceous muds appears to 

 accord generally with depth, there are records which invite further discussion. South 

 of King George Island terrigenous mud occurs at unusual depths for this deposit, but 

 the location is at no great distance from the land surface, which slopes down under the 

 sea with a steep gradient. On the southern side of the Strait the sea-floor falls away 

 quite gently from the land, so that the depth contour of 250 m. lies some 25 miles from 

 the coast of Trinity Peninsula. Thus the occurrence of diatomaceous mud at the slight 

 depth of 345 m. in this part of the strait is explained. But the presence of a similar 

 deposit at a depth of 152 m. close to the northern coast of Trinity Peninsula (St. 

 WS 482) seems to demand conditions, perhaps peculiar to the locality, which are not 

 apparent from the records. 



A further series of twenty-one samples is available from the western part of Bransfield 

 Strait. Here the depression is more shallow and the deposits contain a larger proportion 

 of detrital material. Fourteen samples of diatomaceous mud are from the deeper parts 

 of the sea-floor (800-1000 m.), but towards the south the gentle slope of the bottom 

 allows accumulation of such material at depths of 200-300 m. Terrigenous deposits, 

 containing numerous fragments of volcanic glass, are forming at Sts. 172, 209, WS 394 

 and WS 493 near Deception Island at depths of 168-500 m. The abundance of volcanic 

 detritus here is only to be expected from Andersson's description of the active volcano 

 which forms Deception Island, 1 "a large crater island, 15-19 km. in diameter. The 

 crater itself forms a basin, 9-10 km. in width and connected with the ocean by a very 

 narrow entrance, only about 200 m. wide". Farther south, at St. 175, a sandy deposit 

 at a depth of 200 m. supports Herdman's 2 suggestion that "there appears to be a ridge 

 between Deception and Tower Islands ". Again, sandy material appears at St. WS 389, 

 west of Astrolabe Island at a depth of 130 m. ; this station is on the coastal shelf of 

 Graham Land. 



(b) The Palmer Archipelago is separated from Graham Land by the narrow Gerlache 

 Strait, with an average depth of 600-700 m., which continues westwards by the shal- 

 lower Bismarck Strait to the Bellingshausen Sea. Five samples of the sea-floor along 

 this line consist of diatomaceous mud, while terrigenous mud occurs at a depth of 

 300 m. in Schollaert Channel between Anvers Island and Brabant Island. North of the 

 last-named island, between it and Low Island, is a wide and shallow depression from 



1 Andersson, J. G., 1906. The Geology of Graham Land. Bull. Geol. Inst. Upsala, vn, p. 49. 



2 Herdman, H. F. P., 1932. Report on Soundings, etc. Discovery Reports, vi, p. 231. 



