340 



The Philippine Journal of Science 



1913 



to only 45°, while 2 kilometers from the axis the dip — west- 

 southwest — is as low as from 15° to 20°. Still farther west the 

 beds lie horizontal in the syncline between the Central anticline 

 and the Ayoni anticline. In the opposite or eastern limb a dip of 

 from 55° to 65° to the east-northeast persists for a distance 

 of 1 kilometer to the eastward from the axis. Farther east, 

 the relations are uncertain and are discussed in connection with 

 the Malipa anticline (page 342) . 



To the south the western limb can be identified in the beds 

 exposed along the eastern slope of Cudiapi Range. The upper 

 part of the Vigo shale, which outcrops along Cambagnaon and 

 Cuyocuyo Creeks, dips from 25° to 30° to the west-southwest; 

 but the beds lower in the formation and nearer the axis of the 

 anticline are steeper, dipping from 60° to 70°. The Canguinsa 

 sandstone which has been removed by erosion farther north re- 

 appears in Cudiapi Range, overlying the Vigo shale and dipping 



Fig. 1. Diagrammatic section across axis of central anticline in the 

 upper valley of Malipa Creek, (a) Canguinsa sandstone; (6) 

 Vigo shale; (c) concealed. 



at low angles to the west-southwest. In the eastern limb of 

 the fold in this vicinity the Canguinsa sandstone is encountered 

 very close to the axis dipping gently to the eastward. The 

 nearest exposures of the underlying Vigo shale are vertical, or 

 dip at high angles to the east in the axial portion of the fold. 

 There appears to be insufficient room between the axis and the 

 Canguinsa sandstone in the eastern limb for a thickness of Vigo 

 shale equivalent to that exposed in the western limb. The rela- 

 tions are shown in text fig. 1. 



Possibly faulting has occurred in the plane of the axis as a 

 result of sharp folding, and the western limb has been thrust 

 upward along the fault. Such a condition would explain the po- 

 sition of the lower part of the Vigo shale in the western limb 

 so nearly in contact with Canguinsa sandstone in the eastern 

 limb. 



In the headwaters of Canguinsa River an exposure of Vigo 



