UNCONFORMABLE FRINGING REEFS 



513 



reefs, whether they front the open ocean, as will be shown to be usually 

 the case in the Philippine Islands, or lie along the shore of a lagoon 

 inclosed by a barrier reef, as commonly happens in the Fiji and Society 

 Islands. For the maturely carved spur ends of the embayed shorelines 

 aronnd which fringing reefs, whether standing alone or inside of barrier 

 reefs, are ordinarily formed, as shown in figure 8, have manifestly been 

 much modified by subaerial erosion from the initial slopes of a young 

 volcanic cone : truly not so much modified in quantity as the inter-spur 

 valleys, but as plainly modified in quality. Eeef contacts around such 

 spur ends are evidently unconformable and therefore testify to submer- 

 gence. 



Figure 



-UnconformaMe Contact of a sealevel fringing Beef on the Spurs of 

 dissected volcanic Island 



It is not simply that fringing reefs testify unqualifiedly in favor of 

 unconformable contacts, and therefore in favor of submergence, in prac- 

 tically every case where the inquiry thus suggested has been made; they 

 also testify in many cases to a pre-submergence erosion of so great an 

 amount and therefore of so long a duration, and also to a submergence 

 of so great a measure, that the submergence can be fully explained only 

 by the aid of subsidence and not alone by the rise of ocean level at the 

 end of the Glacial period. Unconformable contacts involving moderate 

 measures of erosion and of submergence might be developed on still- 

 standing islands as a result of the moderate lowering of the ocean during 

 the several moderate time intervals of the Glacial epochs; but the great 



