222 The Philippine Journal of Science ms 



Cordillera the dip of the beds is as high as 70", but gradually 

 this inclination decreases till the beds assume an almost hori- 

 zontal position. The inclination of the beds is much greater 

 on the Antique (west) side of the cordillera. In the foothills 

 local undulations with reverse dips attended by some faulting 

 are to be noted (fig. 3) . 



As pointed out in the di.scussion of the control of topography, 

 these strata assume the attitude of tilted bl(x;ks with the abrupt 

 slope up- and the gentler slope downstream, this slope in mo.st 

 cases corresponding exactly to the bedding planes. Abella's 

 profiles are very good representations of the general conditions. 

 A somewhat modified section, using Abella as a basis, is shown 

 in fig. 3. The survey of Tigum River has revealed the existence 

 of a small anticline just east of Maasin, and perhaps many others 

 exist Avhich would be revealed by a detailed survey of the 

 region. These anticlines are all important in the matter of the 

 accumulation of oil. Complete folds in the strata are, however, 

 the exception, and the dominating structure is monoclinal. Of 

 course, where there are anticlines the reverse type of fold, the 

 syncline, must exist. There is one of these shown in fig. 3 

 just west of the Maasin anticline. As anticlines usually afford 

 the most favorable places for the accumulation of oil, artesian 

 waters are most favorably tapped in the synclines. The reason 

 for this marked difference between two mobile substances is due 

 to their difference in specific gravity. For further discussion 

 of the petroleum possibilities in this region see page 225. 



PRE-TERTIARY FORMATIONS 



At an elevation of about 400 meters near the headwaters of 

 Ulion River there is an excellent exposure of indurated sedi- 

 ments closely resembling slate. Intercalated with these are sills 

 of diorite from 3 to 5 meters thick. The sills follow the bedding 

 planes. The strike of these slaty sediments is northwest, and 

 the dip is 30° to the northeast. No marked difference was 

 noted between that part of the sedimentary beds nearest the sills 

 and the interior ; so it is improbable that the hard slaty character 

 of these beds can be due entirely to the heat or pressure result- 

 ing from the intrusion of the sills. 



Specimen 2322. — The rock is blue-black, very dense, exceed- 

 ingly fine-grained, and has a hackly to conchoidal fracture. It 

 shows on certain surfaces a very fine banding which is distinctly 

 that of sedimentation. The cleavage in these beds is not typical 

 of slates, and hence they might more properly be termed pseudo- 

 slates. 



