246 The Philippine Journal of Science 1915 



of sharp reentrants, including San Isidro Bay, Arevalo Bay, and 

 Campocpoc Bay. Evidently these conspicuous indentations have 

 resulted from local folding. 



GENERAL GEOLOGY 



The geologic formation in northwestern Leyte is predominantly 

 sedimentary and belongs to the late Tertiary and Post-Tertiary 

 series of rocks. The several divisions can be correlated directly 

 with the stratigraphic column as worked out by Pratt and Smith'' 

 in the Bondoc Peninsula petroleum region in Tayabas Province. 



Thin-bedded shales and subordinate thin beds of sandstone of 

 lower Miocene or Oligocene age make up the base of the series. 

 These beds appear to have been laid down unconformably over a 

 complex of igneous and metamorphic rocks of undetermined age. 

 The name Vigo shale was applied to the thin-bedded shale and 

 sandstone series because of typical occurrences along Vigo River 

 in Tayabas. Petroleum is found in the Vigo both in Tayabas 

 and Leyte. 



Overlying the Vigo with some degree of unconformity is a 

 massive or imperfectly bedded formation of clay-tuff and tuff- 

 sandstone, which was designated as the Canguinsa sandstone in 

 Tayabas. This formation yields petroleum and derived bitumens 

 in Leyte, although it is barren or only faintly petroliferous in 

 Tayabas. 



Limestone and calcareous sandstone are encountered with 

 apparent conformity, above the Canguinsa, in both Leyte and 

 Tayabas. These rocks are known as the Malumbang series, and 

 they mark the top of the stratigraphic column except for recently 

 elevated coral reefs, littoral deposits, and modern alluvium. The 

 Malumbang series contains no petroleum in Tayabas, but in Leyte 

 it has been impregnated with petroleum in at least one place 

 with the formation of bituminous limestone and bituminous 

 sandstone as a result. 



The total thickness of the sedimentary formations in Tayabas 

 was estimated at from 1,700 to 1,800 meters, and the sections 

 which can be measured in Leyte show corresponding thicknesses. 



The presence of several small intrusions of andesite and ande- 

 site-agglomerate was recorded in the report on the Tayabas 

 region. In the Leyte field intrusions of this class are much more 

 prominent and numerous. One of the most conspicuous hills in 

 the vicinity of Villaba, namely. Mount Tabeyta, consists of ande- 

 site and nndesite-agglomerate, and a half-dozen smaller intru- 



'■ This Journal, Sec. A (1913), 8, 301 et seq. 



