194 



The Philippine Journal of Science 



1S15 



Limestone. — Limestone in the high mountain region of Luzon 

 is widespread though not necessarily extensive. It is manifested 

 by remnants here and there, generally on the high mountain tops, 

 and by "float" in the streams. One is led to believe that it for- 

 merly extended over practically the entire country. 



The most extensive development of it is probably at Sagada, 

 where we find it projecting from the soil and talus in great 

 masses as shown in the photograph (Plate IV). The bedding 

 planes, which can be distinctly made out even in the picture, 

 dip about 20° southeast. On the weathered surfaces the stone 



j_^ 



■kl.'-'C" 



.r.f'^ 





rft" 



^ufji'' 



Fig. 3. Sketch of the vicinity of Bontoc. 



is bluish gray, but on fresh fracture it is cream white to reddish. 

 Plate IV, fig. 2, shows the characteristic spirelike forms pro- 

 duced by the dissolving action of the heavy rainfall of this region. 



A thin section of the rock shows innumerable fragments of 

 the well-known Mio-Pliocene marine alga, Lithothamnium ra- 

 mosissimum Reuss. This formation, therefore, is equivalent 

 to the upper limestone in Cebu and many other parts of the 

 Archipelago. 



In this limestone at Sagada are numerous sinks and some caves. 

 In the entrance chambers of the caves the Igorots place their 

 dead. One cave has a chamber as large as the auditorium of a 



