GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 83 



The occ-urrences of limestones and shales seen on an excursion from 

 Bosoboso to the iron deposits near Santa Inez remains to be mentioned. 

 On approaching Bosoboso some indistinct limestone outcrops were found 

 in descending the hill into the town. In the river bed to the east of the 

 abandoned settlement of San Jose and at the hot spring described by 

 Abella as the "Mainit de Bosoboso" outcrops of somewhat metamorphosed 

 argillaceous beds were seen which Abella has described as follows : 

 "The country in these localities consists of an extensive formation of 

 old slate; diabasic conglomerates (at Langay-langayan) and limestones 

 (Lanatin Biver). The strata at the hot spring strike 1ST. 10° W. with 

 dips very pronounced nearly vertical toward the east." He explains that 

 the jointing and the fracturing of the formation is due to the igneous 

 rocks which are found as dikes and volcanic masses. 



There is no true slaty structure in the formation at the hot spring or 

 near by and it is evidently a mistake to class these rocks as slates or 

 older slates, or to include them in the discussion of the. older rocks as 

 did Becker on the strength of Abella's description. Certain hand speci- 

 mens from the exposures at the Montalban Gorge are identical in char- 

 acter with specimens from San Jose. The description by Ickis of the 

 formation on the Alas-asin in his section from Infanta to Tanay shows 

 that similar rocks are encountered there. 



Von Drasche in crossing from Laguimanoc to Atimonan found at first 

 tuff, higher up tuff inter stratified with breccia of coral limestone and 

 finally single isolated coral reefs which are rich in fossils. He says that 

 in part the limestone is completely crystalline. On the area of schist 

 which he found he saw an isolated, small coralline limestone cliff. In 

 as much as Von Drasche has seen the typical Tertiary limestone it would 

 be fair to suppose in view of his description of the section that the coral 

 reefs above-mentioned are not to be confounded with it, -and that the 

 breccia of coralline limestone with interstratified tuff beds is a formation 

 distinct from the typical Tertiary, but after having seen the variable 

 character of the Exposures at the Montalban Gorge and having studied 

 the section from Pagbilao to Atimonan it seems more reasonable to accept 

 the opposite conclusion. 



In this connection should be mentioned the conglomerate containing 

 limestone pebbles described by Jagor and Both which the former found 

 on the road from Mauban to Lucban. The locality which is especially 

 described by Jagor is about 2 kilometers east of Sampaloc. When the 

 writer passed this place a landslide had come down the hill to the river 

 and carried away the road, leaving the formation well exposed. The 

 limestone pebbles which appear to have been derived from the dense 

 Tertiary limestone of the region were seen lying in lenticular masses in 

 a coarse-grained, soft sandstone-like matrix and clipping at steep angles. 

 The matrix has been largely derived from the erosion of igneous rock 



