viii. a, 5 Pratt and Smith: Petroleum Resources 339 



the Vigo shale, and this is of practical importance in that the 

 overlap may conceal petroliferous members of the Vigo shale 

 above the Bacau stage. The conclusions in this report regarding 

 the general lines of structure — the position of the main anticlines 

 etc. — are to a degree independent of the unconformity, since 

 the larger folds are approximately coincident above and below 

 the discordance. 



Central anticline. — The principal structural feature of Bondoc 

 Peninsula is the series of folds whose trend conforms roughly to 

 that of the peninsula. These folds are made up of broad shallow 

 synclines and narrow acute anticlines. Subordinate anticlines 

 occur near both lateral coasts, and a larger anticline designated 

 as the Central anticline marks the axis of the peninsula. 



The Central anticline is asymmetric in that the eastern limb 

 is more highly inclined than the western. The fold is sharp, 

 especially in the lower strata which are vertical along the axis, 

 and about 25 kilometers in length. The general strike of the 

 axis — north 30° west — is not maintained with absolute uniform- 

 ity, but becomes almost north and south toward the southern 

 end of the peninsula. A general southerly plunge of the anti- 

 clinal axis is indicated by the fact that, from north to south 

 along the axis, beds successively higher in the stratigraphic 

 column are encountered at the same elevation. 



In the northern part of the field the axis coincides with the 

 summit of the low divide between Sibuyanin and Vigo Rivers. 

 From this point it follows more or less closely a straight line 

 south-southeast as far as Cuyocuyo Creek. Farther south the 

 crest of the fold appears to coincide with the upper part of 

 Canguinsa River, so that south of Cuyocuyo Creek the axis 

 must trend about north and south. Beyond Bacau, the sharp 

 fold dies out, and was not certainly identified farther south; 

 although the gentle overturn of the strata, indicated in the 

 western part of Amoguis Valley, probably marks its con- 

 tinuation. North from the divide between Matataha and Si- 

 buyanin Rivers the Central anticline can be traced as far as 

 the eastern slope of Mount Maclayao. In Mount Maclayao, Vigo 

 shale is encountered, striking east-northeast and dipping steeply 

 to the south, and at the intersection of this line of strike with 

 the Central anticline the identity of the latter is lost in a con- 

 fusion of varying strikes and dips. 



In the axial portion of the fold at the head of Sibuyanin 

 River, vertically dipping beds of Vigo shale are exposed. In 

 the western limb the dip decreases rapidly, and within a few 

 hundred meters to the west-southwest of the axis it amounts 



