680 DR J. H. HARVEY PIRIE ON DEEP-SEA DEPOSITS 



Ice Age as a glacial deposit in shallow water. In its physical characteristics and also 

 in the proportion of mineral particles contained, and microscopic character of the "fine 

 washings" (largely composed of rock flour), it proved to be practically indistinguish- 

 able from a typical Weddell Sea glacial clay. I have intentionally laid some stress 

 upon the clayiness of most of these deposits, because it appears to me from my readino- 

 of the Gauss reports to be more pronounced in this part of the Antarctic than in the 

 regions lying to the south of the Indian Ocean. The width of the marine glacial 

 deposit belt is certainly much wider to the south of the Atlantic than to the south of 

 the Indian Ocean. The greater concentration of the coarser mineral particles within 

 a narrower zone in the latter region would account for their being of a more muddy 

 or sandy character ; but in that region also, as one goes further from the inland ice, 

 the deposits become of a more oozy or clayey nature. 



CaCO^. — Of twenty-eight of these glacial marine deposits, sixteen contained no 

 lime, five merely a trace, and seven amounts varying from 1 to 5 per cent. This 

 paucity or absence of lime is one of the features distinguishing these glacial deposits 

 from the ordinary Blue muds of terrigenous origin in which it is usually abundant. 

 Foraminifera are tolerably abundant in the surface waters, and the trawl showed the 

 presence of numerous living benthoic organ ism.s (fish, brittle-stars, niollusca, etc.) 

 containing lime in the glacial deposit area, so that its absence must be attributed to 

 a strong solvent action of the bottom cold layers of water. The samples which 

 contained small amounts of lime are irregularly distributed, and bear no obvious 

 relationship to the depth, position, etc. This patchy distribution of lime was also 

 noted by the Gauss, and a somewhat similar condition by the Valdivia. On the 

 latter expedition an area of peculiar Globigerina ooze was found between lime-free 

 Diatom ooze and Grlacial mud. 



The principal calcareous foraminifera in these deposits is Globigerina dutertrei ; 

 others occurring are G. duhin, G. hidloides, G. p achy derma, Truncatidina wuellerstorji, 

 T. pygmcea, T. tenuimargo, T. tenera, Cassidulina suhglobosa, Pullenia spharroides, 

 Miliolina hucculenta, Clavulina communis, and Cristellaria convergens. Ostracod 

 valves were noted a few times. 



Siliceous Organisms. — Of twenty-seven samples four contain no siliceous organisms, 

 seventeen a mere trace — and that more often sponge spicules and large radiolaria than 

 diatoms — five from 1 to 2 per cent., and one (No. 26a, bordering on Diatom ooze) 10 per 

 cent. The absence of diatoms is another of the remarkable features of these glacial 

 deposits, and one which has been already commented upon in speaking of the Diatom 

 oozes. The surface waters over these deposits simply teem with diatoms, but apparently 

 they are all carried ofli" northwards by an under-current set up by the melting ice, and 

 only sink to the bottom far beyond their region of maximum occurrence in life. Their 

 absence is as striking in the more northerly part of the glacial clay, where the 

 accumulation is presumably slower, as in the deposits from nearer the Antarctic 

 continent, where it is more rapid, so that mere hiding of the diatoms through rapidity 



1 



