﻿COMPOSTELA-DANAO COAL FIELD. 387 



former material. This limestone does not conform to the beds below, 

 but lies as a mantle upon the folded and truncated coal measure beds, and 

 in some cases upon igneous formations. However, there is a decidedly 

 warped appearance to this formation which is in part due to the configura- 

 tion of the older topography upon which the limestone was laid down, 

 and also to some minor folding subsequent to its deposition. 



A somewhat noteworthy feature of the drainage is the orientation 

 of the Cot-Cot and its tributaries, the Jimarco, the Parel and the Muao; 

 and the peculiar course of the Danao. 



The Cot-Cot and its three tributaries are seen to conform with 

 reasonable closeness to two lines which make an angle of 92° with one 

 another. The Jimarco and the Cot-Cot fall on a line the course of 

 which is jST. 37° W., while the Muao and the Parel come into the main 

 stream approximately at right angles or along a line N. 55° E. I am 

 strongly of the opinion that the N. 37° W. line is a fault line, although I 

 have no other cause to think so than its great persistence. 



Side branches under normal conditions do not join the trunk stream 

 at right angles, but alwa} r s in such a manner as to make an acute angle 

 upstream with it. The reason for this departure in this region lies in 

 the structure of the underlying formations. In a traverse of the Muao, 

 in more than one place, I foimd that the strike of the beds conformed to 

 the direction of the stream and there should be little doubt but that 

 this factor has controlled its course, as it would be much easier for the 

 stream to cut along this line than across the formations. As the dip 

 is generally to the southeast throughout the greater part of this region, 

 it would be expected that the stream would shift laterally and in the 

 direction of the dip. 



I am not so certain that this holds true in the case of the Taganejan, 

 as exposures of the sedimentaries are not so plentiful. If we now examine 

 the course of the Danao, the headwater tributaries of which are known 

 as the Cajumayjumayan and the Donga we see that it starts on the north- 

 east slope of Mount Lantauan and flows southwest in the Cajumayjumayan 

 basin until it strikes the Cordillera, it then swings to the south at the 

 base of this ridge and turns rather sharply to the southeast, worming its 

 way in great curves through a canon-like cut in the basal igneous forma- 

 tion, and still farther down it takes a due easterly course to the 

 sea. 



As the Cajumayjumayan Valley is a S3 r ncline, the river in this part 

 of the course is a consequent stream. In time the courses of Donga and 

 Cajumayjumayan Creeks will coincide, as both shift laterally along the dip. 

 That part of the stream which lies between Sibacan and Ustaganon 

 Creeks is antecedent. Its present incised meanders in that portion are 

 evidently inherited from an earlier and higher stage of the stream, and 

 may point to a post-Miocene peneplain. 



