518 W. M. DAVIS SUBSIDENCE OP REEF-ENCIRCLED ISLANDS 



exceptionally long one which, when certain islands stood lower, crowned 

 the long ridge of Cebii where, according to Becker, a mantle of coral 

 reaches "to the very crest of the island. . . . 2,362 feet in elevation" 

 and gives it "an even line many miles in length" (1901, 69, 75). 



The occurrence of elevated reefs, probably fringes or barriers, has been 

 recorded on many other islands of the Australasian archipelagoes ; Semper 

 found what he took to be an elevated atoll at an altitude of more than 

 3,000 feet on Luzon, and Drasche found reef limestones on the same 

 island at altitudes of 3,500 and 4,000 feet (1871, 31-, 42-) ; but these 

 and other earlier authors do not state whether the limestones rest con- 

 formably or unconformably on their foundation. This critical matter is 

 later touched on by Becker and Smith, though without full application 

 of its meaning. Becker states that the Philippines suffered deforma- 

 tion and uplift in late Eocene time, that they sank in late Miocene time, 

 and that general upheaval with oscillations has taken place since. "All 

 the evidence thus far adduced, both paleontological and structural, points 

 to a progressive uplift of the archipelago, beginning in the late Miocene 

 and still proceeding. . . . Evidences that the islands are rising at the 

 present time, or have been rising within a few years, abound from one 

 end of the group to the other. It is also clear that the amplitude of the 

 movement has been very great" (1901, 79, 77). 



Furthermore, Becker notes, that Cebii in particular is covered for the 

 most part by a mantle of coral, 100 or more feet in thickness, which 

 reaches from the crest of the island to the sea and forms "a vast num- 

 ber of terraces, all of which are sensibly horizontal" (1901, 19, 79), 

 while in Negros there is "a series of hills flanking the main range with 

 excessively steep slopes and crests only a few feet in width. They were 

 composed of rough coral and seemed to represent barrier reefs" (75). 

 The same observer states explicitly that there is a "great unconformity 

 both in Cebii and in N'egros. It lies between the [Miocene] lignitic 

 series and the coral mantle" (69), but he inclines to believe that the 

 elevated reefs of these islands were formed during the elevation of their 

 foundations and not during the preceding subsidence; and perhaps for 

 this reason he gives some credence to Semper's objections to Darwin's 

 theory. 



W. D. Smith, whose latest paper on the Philippines makes reference 

 to "coral platforms" (fringing reefs) on which the outwash of alluvium 

 is rapidly forming coastal plains, notes that "in a few places the reefs 

 were found to make an unconformable contact with eroded igneous rocks 

 beneath" (1917, 540), but no inference is drawn from this as to rapid 

 subsidence preceding the formation of the present reefs, presumably 

 because the origin of reefs was not the special subject of study of this 



