348 THE DEEP SEA 



equal to the whole ocean floor. A large but indeterminate part of 

 this accumulates in hemipelagic deposits and locally, as in coral 

 atolls, but most of it must go into the pelagic calcareous ooze. 

 The noncalcareous "red" clay, where solution results in no carbo- 

 nate accumulation, covers about one-third of the total area, and 

 thus w^ould not radically change the above estimate on rate for the 

 areas of calcium carbonate accumulation. This rate based on influx 

 from rivers corresponds approximately with the 1 cm per thousand 

 years for Globigerina ooze accumulation, indicated by Kuenen 

 (1950, p. 383). 



The great excess of calcium carbonate deposits in the rocks of 

 the continents, over the percentage to be expected from the 

 original igneous rock sources, cannot represent a segregation there, 

 through dominance of shallow water deposition of the calcium 

 carbonate, if the present great percentage of calcareous deposition 

 in the deep-sea persisted through much of the earth's history 

 known in the sedimentary rocks. 



This enigma is evident in all the attempts at a geochemical 

 balance of the elements eroded from igneous rocks and accumu- 

 lated in all sediments and ocean water. The various estimates and 

 results cannot be summarized here. Results from various ap- 

 proaches and assumptions led Kuenen (1950, p. 389) to conclude 

 that the present large segregation of calcium carbonate in pelagic 

 sediments may have begun in Cretaceous time, with the advent of 

 the planktonic Foraminifera. The coccoliths and other very small 

 calcareous remains of planktonic algae appear to have been a 

 more important carbonate component than the Foraminifera until 

 late in the time since the Cretaceous. Present evidence, however, 

 does not preclude the possibility that all such calcareous plankton 

 were unimportant before the Cretaceous. This interpretation is 

 inviting as it could account for a great dominance of shallow water 

 deposition of the calcium carbonate, by the benthonic organisms, 

 and perhaps inorganically, in pre-Cretaceous time. 



An attempt at a geochemical balance by Goldberg and Arrhenius 

 (1958, p. 207) resulted in a much smaller total volume of the 

 noncalcareous pelagic clays than that of Kuenen's computations, 

 but the same problem of a long-term lack of balance for calcium 

 carbonate deposition is again evident in their results. 



