﻿ASBESTOS AND MANGANESE DEPOSITS. 163 



As nearly as I could ascertain, these beds are horizontal. I should 

 say, to judge from the included forms, that the deposit is of shallow 

 water origin, but not very close to the littoral. Despite their low topo- 

 graphic position, I consider these beds stratigraphically to he above both 

 the Pasuquin and the Bangui formations, and from the very recent 

 appearance of all the fossils and their close relationship to forms now 

 living in the Philippine seas with which I have compared most of them, 

 I shall provisionally refer them to the Pleistocene. 



Raised Coral Reefs (Currimao) . — Only bare mention will be made of 

 these, as I could only note them in passing ; suffice it to say that coral 

 reefs elevated to the extent of 10 to 12 feet above high tide exist close 

 to the water's edge, and behind these the topography by its terraced 

 appearance indicates the existence of one or more raised shelves at about 

 100 feet elevation, and possibly a still higher one. 



I have not made a quantitative study of the species in the raised and 

 living reefs, but even a cursory study shows them to be quite similar. 

 Much light is thrown on the formation of our great limestone beds in 

 the Philippines by a close examination of these raised reefs. In the 

 limestone in many cases a great branching coral head may be seen stand- 

 ing upright and in the same position in which it grew, surrounded by 

 a hardened matrix of limestone which consists of hardened coral sand 

 and which contains fragments of corals and shells. Spines of Ecliino- 

 dermata are always plentiful in this matrix. 



These raised reefs have a very even upper surface, due to the manner 

 of growth of corals. Doubtless, they have not been long in their elevated 

 position for it is well known that these reefs rapidly harden and become 

 strong after being exposed to the air. Mr. Becker 14 has already parti- 

 cularly referred to this phenomenon. 



SUMMARY OF THE GENERAL GEOLOGY. 



From the foregoing it is evident that here we have a region of greatly 

 varied geology, probably exhibiting more diverse features than most parts 

 of the Archipelago; it is primarily a district of metamorphism and this 

 metamorphism is regional rather than local. 



Upon a batholith of diorite there were laid down certain sediments 

 which by great dynamic forces have became altered into entirely new rocks 

 in which practically every mineral has been formed anew out of older 

 and entirely different minerals. Granulite dikes have enhance! this 

 general metamorphism. Still later over all these basement rocks and 

 crystalline schists, there have been deposited sediments which, though 

 often found tilted at high angles, show little subsequent change in their 



14 G. F. Becker: Geology of the Philippines, .ilst An, Kept. U. 8. Oeol. Sur. 

 (1902) 561. 



