13 



One of the greatest needs today in the stud:" of sedimentation 

 is the collection of r.ore cores v/ith the rudi-aentary instrur:ents so 

 far devised, still nore the development of apparatus to obtain 

 longer cores. Only in this way can we learn anything about thp 

 thickness of the nodern sediments, and about their variations in 

 composition with distance belo"? the surface of the nud. 



The problems for nhich cores of the bottom are needed rr.av be 

 classed as (l) rate of deposition under given circumstances; \^2j 

 constancy or the reverse in the typQ of sediment laid down over long 

 periods; (3) the cheuical alterations that take place in the deeper 

 layers of sediment that are protected from the water by the overly- 

 ing ooze; (4) uplifts or subsidences of the sea floor revealed oy 

 the presence of" one type of sediment upon another; (5) problems of 

 glacial geology. 



Some interesting beginnings have already been made in these 

 fields. Although no cores more than about 80 cms. long have yet 

 been obtained from deep water, those that have been taken in the 

 north and south Atlantic basins, with their poleward extensions, 

 show that it is the rule for even this thin s^aperficial stratum to 

 show a rather noticeable stratification. In this connection, we 

 think especially of the soundings taken by the Ilordske Nordhaus, 

 German South Polar, "llichael Sars, " and "Ileteor" expeditions, as 

 well as by the recent "Atlantis" cruise sent out by the I.!ruseum of 

 Comparative Zoology. With the stratification usually taking the 

 form of a difference in the amount of lime contained in the mud or 

 ooze at different depths downward from its upper surface, its bear- 

 ing on the formation of sedimentary limestones is obvious, llori^lly, 

 there seems to be less and less lime the deeper one penetrates into 

 the mud. How far does this decrease reflect the solvent action of 

 the entrapped water, i.e., the age of the sediment? Does the decay 

 of organic matter in the mud give this water such a load of CO3 that 

 its solvent power is much greater than that of sea water generally? 

 Can it be that solution of this sort actually limits the thickness 

 to which lime deposits can accumulate on the ocean floors of today, 

 by dissolving calcium carbonate from the deeper layers as fast as it 

 accumulates on top? How does all this bear on the depth of water in 

 '.vhich the limestone rocks were originally laid dovra? 



We know nothing definite about the rate at which the limy oozes 

 are actually building up in thickness on the ocean beds, or even 

 whether they are so building up at all. Our only direct evidence as 

 to the rate of their deposition is the rapidity with which 

 Globigerina ooze buries and so protects submarine telegrs.ph cables. 

 But it is certain that the sea floor generally, over all the vast 

 area occupied by the Globigerina oozes, is not rising at as rapid a 

 rate (an inch in ten years, or a fathom in every 720 years) as 

 experience v/ith cables would suggest if D.ccepted at face value. How 

 do the processes of solidification, of solution within the sedia.ents, 

 and of the sinkings of the earth's crust as weight increases (co:::- 

 pensated by uplifts elsewhere) balance the tendency toward ac3U„;ula- 

 tion? 



Does the failure of geologists to find any existing limestones 

 to which abyssal origin can safely be credited mean that the 



