14 



accuniulation of thick beds of calcareous sediments has always been 

 confined to shoal waters, or has taken place at great depths only 

 under special circur^stances? 



The few stratifications so far studied have enlarged our views 

 of cliinatio changes in the oceans in the past especially for high 

 latitudes, enough to point the need of more nuiuerous probings of the 

 bottom to greater depths. 



The thermal relationships of the various species of Fora.^inifera, 

 shells of which have been identified at different depths below the 

 uppermost layer of ooze, have proved highly significant as indices 

 to changes in the temperature of the ocean. Similarly, the alternat- 

 ing strata of shell-bearing, and shell-less clays on the bottom of 

 the Korv/egian Seas emphasize the geologic fertility of studies in 

 this field. The urgent need for more detailed information as to the 

 temperature, and other vital optima, of the various pelagic shell 

 builders here unites the biologist with the geologist, 



"^la may also hope to learn much about the changes in level that 

 the sea floor has undergone from the stratification to be seen even 

 in such short cores of the ooze as have yet been taken, for we have 

 an index to the depth of water at which the sediments were laid down 

 in the fact that the limy oozes (as a class) accumulate only in 

 depths less than about 2500 fathoms, (shoa.ler still in the Pacific) 

 while it is only at depths greater than 3000 fathoms that the red 

 clay, or the radiolarian and diatom oozes are practically uncon- 

 taminated by limy shells, except in the pacific, when the typ3 of 

 sedimen is found in comparatively shallow water. Some short cores 

 suggestive in this respect have already been obtained. The pr?.sence 

 of abyssa-l red clay overlying Globergerina ooze has been used as an 

 argument for a very considerable recent sinking of the sea floor in 

 the mid- equatorial Atlantic, Seven such cases have already been 

 recorded and we may expect still others, xvhen detailed accounts of 

 the results of the "Lleteor" Expedition appear. Stratifications of 

 the opposite sort, i.e., with Globigerina ooze or Diatom ooze over- 

 lying blue mud, such as even the short cores taken by the "Heteor" 

 revealed over a considerable area off Tifest Africa, between 13^ N. 

 latitude and the equator, point to the opposite process of subsidence. 

 The layers of volcanic ash found in some of the "Ileteor"' sediments 

 a,lso open interesting problem.s. Sim-ilar cores, and if possible, 

 longer ones, are desiderata for all the deep subm.arine troughs, and 

 especially for those that fringe the continents, as possible clues 

 to the ages of these depressions, relative to the permanence of the 

 oceans as a Y/hole, and to the ages of neighboring mountain chains on 

 land. 



The probability that cores would throw light on the actual rate 

 of deposition in given circumstances, if some time marker could be 

 established to start from, gives special importance to such work off 

 coasts the character of which was determined in the last glacial 

 period. Circumscribed basins, scoured out by the ice sheet, so deep 

 that mud is entrapped within them, are especially attractive subjects 

 for tine-studies of this sort, if compared with the sedir.ents 

 deposited on land since glacial tii:ies, from materials laid dorm by 

 the ice itself. Projects are, in fact, under way for obtaining cores 



