214 The Philippine Journal of Science 1914 



posed exposures of the granite. The varying thickness of the 

 column of sedimentary rocks, as exposed by erosion at different 

 places, is due apparently to the increasingly greater overlap of 

 the successive beds upon the older basement. 



Very close to the base of the series, which from the presence 

 of the Binangonan limestone in its upper portion has been 

 designated as Miocene, is a subordinate thickness of white crys- 

 talline limestone or marble. This limestone was not identified 

 in all parts of the area, and is not differentiated on the geologic 

 map from the shale-tuff-sandstone member in the base of which 

 it occurs. Its stratigraphic relations are most clearly developed 

 near Camaching, where it is thoroughly metamorphosed and is 

 interbedded with tuffs and clastic rocks near the base of the 

 series. 



The Binangonan limestone, with the underlying shales, tuffs, 

 sandstones, and clastic rocks and the lower limestone, can be 

 correlated stratigraphically with the coal-bearing Miocene in 

 other parts of the Philippines, notably in Cebu. In the Cebu 

 sedimentary column the lower limestone, which is immediately 

 above the basal conglomerate, is rich in fossils, and in a sample 

 collected by one of us, Smith has identified tentatively Heteros- 

 tegina margaritata Schlumberger, which according to L. Schlum- 

 berger " was found by Martin in the Oligocene near Dax 

 (France ?). It is probable, therefore, that the limestone at 

 Camaching is Oligocene in age, although at this place it either 

 is not fossiliferous or the fossil outlines have been lost in the 

 crystallinity resultant upon metamorphism. 



To the east of the iron-ore deposits and outside the region 

 shown upon the geologic map are a number of small detached 

 areas of sedimentaries, in some of which reddish slates were 

 found apparently underlying the rocks just described. From 

 the presence of annular tests suggestive of radiolaria in samples 

 of these slates. Smith is inclined to correlate them with the 

 Baruyen chert of Ilocos Norte and the Ulion slates of Panay 

 which he considers to be probably Jurassic. 



The sedimentary rocks are related to the iron ores through 

 the occurrence of the latter, together with intrusive dikes, at the 

 base of the Miocene series and the association of the Cama- 

 ching ores with the lower limestone. 



' Note sur un Lepidocyclina nouveau de Borneo in Samm. d. geol. Reichs- 

 mus., Leiden (1902), 1, 6. 



