MINERAL RESOURCES OF AROROY DISTRICT. 403 



them and joins the Guinobatan about one kilometer from its mouth. 

 The Guinobatan rises near Mount Baha Simbahan and flows in a general 

 northeasterly and northerly direction, partly encircling Mount Vil-lon. 

 Its course between Mounts Kalakbao and Bagadilla is almost westerly; 

 like the Bangon, it cuts obliquely across the vein system. Beyond the 

 gorge the stream turns sharply to the north and for two kilometers 

 flows parallel to the bay and about one kilometer distant from it. 

 Panique Creek drains the greater part of the in-egular area lying between 

 Mount Kalakbao and the Lanang Eange. The peculiarities of the course 

 of the Lanang Biver have been discussed at length in my paper on the 

 physiography of western Masbate.^* It, like the Guinobatan, rises 

 on Mount Baha Simbahan, and where mapped in the Aroroy district 

 presents a very peculiar course which seems to be the result of successive 

 stream captures, for instead of flowing down the broad valley to the north 

 of the Lanang range, which apparently was its earlier course, it twice 

 cuts through the range in deep gorges. The Luya, a tributary of the 

 Lanang, flows from the northern side of Mount Cogran and joins the 

 main stream about two kilometers above the upper gorge. 



The southern shores of Port Barrera are lined with mangrove swamps, 

 which have a very large development at the mouth of Lanang Eiver, and 

 at the head of the bay near the barrio of San Agustin. 



GEOLOGT. 



In the geologic map accompanying this paper, the rocks are divided 

 into six formations as follows : 



1. The Kaal formation, containing the oldest rocks in the district, 

 chiefly slates, outcropping in the valley of Kaal Creek and in isolated 

 patches to the northward. 



2. The Aroroy quartz diorite, occupying the northern portion of the 

 area and intrusive into the Kaal series. With this are mapped scattered 

 outcrops of other deep-seated igneous rocks including diorite, gabbro, 

 and syenite. 



3. The Panique volcanic series which covers the gi'eater part of the 

 area. On the map this series has been subdivided roughly into the 

 dominant andesitie types, the pyroclastic rocks, and local areas of sedi- 

 ments derived from the andesite and the more basic igneous rocks. 



4. The Mountain Maid limestone, the single outcrop in this district 

 of the blue limestone already referred to, is found on the Mountain Maid 

 claim in the Guinobatan Valley. 



5. The Lanang formation of conglomerate and sandstone forming 

 the hills to the south of the Lanang Eiver. 



6. The Port Barrera formation, consisting of Miocene sediments, 

 found only on the opposite side of Port Barrera. 



" Loc. cit. 



