GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 79 



basaltic pebbles and it is probable that there are numerous dykes of it in 

 the region. 



Tertiary limestones, sandstones, shales, and coal. — The first mention 

 of the occurrence of limestones in the eastern cordillera was by Meyer. 

 • Both cites him as saying that he saw at San Mateo (probably the cave of 

 San Mateo and present site of waterworks dam) and near Balete (Mon- 

 talban) fine-grained hornblendic slates lying on the limestones of San 

 Mateo. Following this is the description by Von Bichthofen. He 

 visited the locality of the San Mateo cave, at which place he saw a 

 limestone mass extending far to the north and inclosed between trachytes. 

 In a direction nearly south from this place he saw an isolated limestone 

 hill surrounded by trachytes, half way on the road from Antipolo to 

 Bosoboso. In extension of this line he found a small limestone mass 

 which he described as rising in an arrow-like form out of trachyte and 

 lying northeast of Binangonan. ' The limestone is stated to be older than 

 the trach) r tes since pieces of it were found in a trachyte breccia. 



Von Bichthofen says concerning the age of the limestone that from 

 outward appearance it would be considered as Jura, but that he was so 

 fortunate as to find Nummulites and therefore referred it to the Eocene. 



Von Drasche found limestones on Foray Creek at which place he saw 

 a compact breccia composed of limestone and diabase-aphanite on both 

 sides of it. He conjectured that this exposure is a continuation of the 

 limestone to the south at the San Mateo cave, which he also examined. 



In the geologic map accompanying this report, the limestones at the 

 localities of Poray Creek, the gorge at the waterworks dam site, the 

 exposure between Antipolo and Bosoboso and the Binangonan locality 

 are included in a single area. 



The next reference to the limestone of this belt is by Smith, who 

 found Orbitoides in some samples collected by Ickis from the Binangonan 

 locality. Smith visited this locality, collected additional specimens and 

 described Orbitoides riclithofeni s. n. He believed this to be -the fossil 

 which Bichthofen called Nummulites. He called attention to the fact 

 'that Becker considered as unsatisfactory the evidence showing the 

 Binangonan limestone to be Eocene as classified by Bichthofen and that 

 there is no reason why it may not be Oligocene or even Miocene. 

 Further supporting himself by the fact that Martin had found Orbitoides 

 in the marls of Cebu Island of the Philippine group, and declared them 

 to be the equivalent of the "Java Gruppe" which is Miocene, Smith 

 referred the limestones of the Binangonan locality to the Miocene. 



The conspicuous outcrops of the limestone are, as has been stated by 

 most writers, ridges or hills of a massive, whitish to yellowish, dense and 

 fine-grained limestone showing evidence of metamorphism and usually 

 breaking with a conchoidal fracture. 



The so-called Binangonan locality which is. about 7.5 kilometers to 



