316 



The Philippine Journal of Science 



1913 



As a preface to the discussion of the separate formations, 

 general geologic sections obtained in different parts of the region 

 will be recorded. It should be remembered that the thicknesses 

 assigned to the various formations are estimates only, and are 

 not based upon accurate data. 



In the latitude of Matataha and Vigo Rivers a thickness of 

 the Vigo shale greater than is exposed elsewhere is encountered 

 in the limbs of the Central anticline near the middle of the 

 peninsula. Toward the coasts on either side the upper forma- 

 tions appear overlying the Vigo shale. The section through the 

 rocks east of the anticlinal axis is shown in Table IV. 



Table IV. — Geologic section from the seacoast westward through Cam- 

 bagaco Ridge and Vigo Valley to the axis of the Central anticline. 



Formation. 



Description. 



Approxi- 

 mate thick- 

 ness. 



Recent 



Unconformity'. 



Malumbang series . 



Canguinsa sandstone . 



Unconformity. 



Vigo shale . 



Raised coral reefs and alluvium. Coastal plain. 



Upper limestone. Coralline; eastern slope of Cam- 

 bagaco Ridge; thick bedded to massive; dip 30° 

 northeast. 



Cudiapi sandstone. Bedded, yellow to brown sand- 

 stone; calcareous and of medium-grain size; local 

 crossbedding; summit of Mount Cambagaco. 



Lower limestone; gray to white; thick bedded or 

 massive; locally concretionary; dip 45° northeast. 



/Gray clayey sandstone, usually bedded; west slope 

 of Cambagaco Ridge. 



Sandy massive clay; blue to gray in color: close 

 jointed in some exposures; dip 30° to 40° (north of 

 Vigo River to northeast, south of Vigo River to 

 southeast); abundant fossils in parts of base; 

 a single outcrop of volcanic agglomerate inter- 

 bedded (?) in base on Vigo River at the mouth of 

 Bagacay Creek. 



Abrupt increase in the angle of dip; western base 



of Cambagaco Ridge. 

 /Baeau stage. Grayish blue to black shale: fine 

 grained and bedded; dip 60° to 80° east-north- 

 east; traces of oil and inflammable gas. Volcan- 

 ic agglomerate and massive andesite (flow?) , a 

 single outcrop on Tangob Creek; included in shale. 



Shale interbedded with sandy shale and occasional 

 layers of sandstone, all thin bedded; strikeB in 

 various directions, dips usually steep; nearer axis 

 of anticline, dips become uniform 55° to 65° east- 

 northeast. Vertical in axis; base not exposed. 

 Regular strata east of the anticlinal axis prob- 



\ ably at least 800 meters thick. 



Meters. 

 10 



30 



40 



20 

 70 



100 



