Daly — The C oral-Reef Zone. 155 



Similarly, Abendanon assumes (Oligocene) peneplana- 

 tion of Celebes, as noted by Davis. 20 The wide shelf west 

 of Palawan island means prolonged crustal stability for 

 the eastern part of the China Sea area — a crustal qui- 

 escence which followed a period of crustal unrest both in 

 the Philippines and in Malaysia. The question is as to 

 which period or process most affects the problem of the 

 living coral reefs. If any inference from the lands 

 bordering the China Sea is permissible, it is more rele- 

 vant to assume recent, prolonged stillstand at the Mac- 

 clesfield Bank and the other great banks thereabouts than 

 to assume recent subsidence. The full duration of effec- 

 tive crustal stillstand cannot yet be expressed in terms 

 of geological periods, much less in years, but it need not 

 be any longer than the "long stationary period" or a 

 "long interval of rest" postulated by Darwin to explain 

 the flatness of lagoon floors and other, associated fea- 

 tures. 



6. Assumed Uniformity of Reef Growth. — Objection 

 has been made to the Glacial-control theory on the ground 

 that it demands for existing reefs uniform growth, uni- 

 form breadths, and uniform heights above platforms. 

 The mere statement of the test shows that it is unreason- 

 able. The volumes of the living reefs, measured above 

 the levels of their theoretical platforms, depend on many 

 highly variable factors, which may be listed : a. Date of 

 colonization by reef organisms ; b. Initial depths of the 

 platforms ; c. Depths of water where talus must accumu- 

 late in order to support reefs which have been growing- 

 outwards ; d. Amount of food supply for reef organisms ; 

 e. Density of the plankton and shallow-water, non-coral 

 population furnishing debris to the growing reefs ; /. 

 Distribution of hurricane tracks and other oceanic phe- 

 nomena affecting the welfare of reefs ; g. Recent crustal 

 deformation; h. Character and abundance of each coral 

 and algal species instrumental in the building of reefs. 



Without further expanding the list and without labor- 

 ing the point that all eight factors named are exceedingly, 

 variable throughout the tropical zone, one should have no 

 difficulty of understanding why existing reefs are partly 

 alive, partly drowned and dead ; well developed at or near 

 low-tide level, and in many other cases nowhere built up 

 to that level ; knolly, or continuous ; narrow or relatively 

 broad at any given level. 



20 W. M. Davis, Jour. Geol., vol. 26, p. 394, 1918. 



