SEA-FLOOR DEPOSITS. PART I 313 



Station G. 19. ii. 26. Lat. 52 54' S. Long. 34° 05' W. 3469 m. (Plate XVII.) 



Diatom ooze. A whitish, coherent, powdery sediment, made up entirely of diatom frustules, 

 among which large centric forms such as Coscinodiscus and Thalassiosira are most conspicuous; 

 other forms include navicular and elongate genera, e.g. Fragilaria, Achnanthes, Thalassiothrix and 

 Rhizosolenia. 



Station H. 2. iii. 26. East Cumberland Bay, South Georgia. Lat. 54 15' 15" S. Long. 36 32' W. 

 229-256 m. (Plate XIX, inset.) 



Diatomaceous mud. A grey fine-grained mud, mainly composed of angular to subangular mineral 

 grains of extremely small size. Some fragments of quartz, however, are more than 01 mm. across. 

 Some centric diatoms {Coscinodiscus) are present; they are usually rather small but some reach 

 o-i mm. in diameter. 



Station I. April 1926. Off Cumberland Bay, South Georgia. 183 m. 



Diatomaceous mud. The deposit contains abundant mineral fragments (quartz and green horn- 

 blende) ; a few reach 0-2 mm. in diameter but the majority are smaller. Fine-grained flocculent material 

 contains centric diatoms (chiefly Coscinodiscus), many of which retain their greenish protoplasmic 

 contents; finer particles may be comminuted diatom tests. The greenish colour of the deposit is 

 apparently due to chlorophyll, for the preservative liquid is coloured green. 



Station J. 21. v. 26. Lat. 49 32' 30" S. Long. 55 28' 30" W. 892 m. (Plate XVII.) 

 Terrigenous mud. This rather sandy grey mud consists mainly of mineral grains among which 

 some reach a diameter of 0-2 mm., but most are below diameter of 0-05 mm. Grains of quartz and 

 green hornblende are abundant. There is some admixture of diatoms and sponge spicules. 

 Station K. 25. ix. 26. Lat. 33 05' S. Long. 1 6° 18' E. 3260 m. (Plate XVII, inset.) 

 Globigerina ooze of same type as foregoing samples. The finer material consists largely of com- 

 minuted foraminiferal shells, coccoliths and rhabdoliths. 



Station L. 28. ix. 26. Lat. 33 19' S. Long. 17 40' E. 235 m. (Plate XVII, inset.) 

 Glauconitic mud. This is a detrital sediment consisting mainly of clean quartz grains, apparently 

 evenly graded at a diameter of about 0-05 mm. Some glauconite is present as dark green grains while 

 dark opaque grains, slightly larger, occur in some abundance. Flocculent matter also occurs. 

 Station M. 29. ix. 26. Lat. 33 21' S. Long. 16 47' E. 2020 m. (Plate XVII, inset.) 

 Globigerina ooze. Mainly broken tests of Globigerina. Little detrital matter if any. Shields of 

 calcareous flagellates (especially coccoliths) are plentiful among the finer particles. 

 Station N. 26. ii. 27. Lat. 62 57' S. Long. 6o° 21' 30" W. 967 m. (Plate XX.) 

 Diatomaceous mud. The sample consists mainly of greenish flocculent material which is ap- 

 parently diatomaceous in origin. Besides frustules of Rhizosolenia, Fragilaria and Coscinodiscus it 

 contains small sand grains with a diameter of usually less than 0-05 mm., among which quartz and 

 volcanic glass are noted. 



Station O. 19. iii. 27. Lat. 64 56' S. Long. 64 43' W. 435 m. (Plate XX.) 



Diatomaceous mud. A light grey mud with abundant grains of quartz and green hornblende ; 

 some of the grains are 0-5 mm. across, but the majority are less than 0-05 mm. in diameter. Organic 

 remains form a subordinate proportion of the sample ; they are mainly broken diatom tests (but some 

 whole frustules of Coscinodiscus) and sponge spicules. 



Station P. 21. xii. 26. Drygalski Fjord, South Georgia; about i-ii miles from glacier at end of 

 fjord. 178-3 m. (Plate XIX.) 



Diatomaceous mud. A greyish mud, containing roughly equal proportions of small sand grains 

 and flocculent material. The sand grains, generally less than 0-05 mm. in diameter, are mainly 

 fragments of quartz, but green hornblende is also plentiful. The flocculent matter is largely diatom- 

 aceous ; there are some unbroken centric frustules. 



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