﻿COMPOSTELA-DANAO COAL FIELD. 393 



in, and from there on up to the base of the limestone all outcrops 

 (which are very few indeed) show sandstone. This sandstone in its 

 composition very clearly demonstrates that it was largely derived from 

 the igneous material near at hand and we may infer that the only 

 high land at the time of its formation consisted of the diorite and 

 greenstone hills which stood above and immediately to the westward of 

 the tidal swamps in which the coal was forming. We can estimate the 

 thickness of the sandstone only approximately, but considering the 

 outcrops on the slopes of Mount Licos, I believe it to be not over 150 

 meters (500 feet). It is very improbable that there is an unconformity 

 between the shales and the sandstone. Numerous observations of the 

 strike and dip of these formations show the strike in general to vary 

 from N. 27° E. to N. 55° E. and the dip anywhere from 20° to 90° SE. 

 In the region to the west of the Mount Licos workings and in the arroyos 

 which head in or near the igneous formation, I found some westward dips 

 at rather high angles, showing complete overturn, but this is to be ex- 

 pected as the igneous rock is approached. 



There is every reason to believe that the limestone rests unconformably 

 above the sandstone. This formation has two well-marked phases; the 

 lower characterized by being softer, more of a yellowish color and so far 

 appearing to be unfossiliferous, it also is more stratified than the upper 

 part ; the upper portion is a very white, hard, sometimes crystalline lime- 

 stone, revealing little regularity of structure. 



Before describing it in detail I should discuss two other formations 

 which occur in the stratigraphic column between the sandstone and the 

 limestone. 



Both of these are terrestrial deposits — the first or lower is a conglom- 

 erate made up of igneous sandstone, shale and slaty pebbles. The very 

 reddish-brown color of both the pebbles and the matrix, the evidence of 

 oxidation and the general heterogeneous character of the pebbles show 

 pretty clearly that this formation is in the nature of a flood-plain deposit, 

 or as Professor Barrell would call it, piedmont deposit. On the map 

 this is denoted by the brown color, and the formation is to be found exten- 

 sively developed on the east side of Mount Licos. In places it is at least 

 90 meters (300 feet) thick, and it may be more. A remnant of it is found 

 in the hogback in the bottom of the Cajumavjumayan Valley and in 

 several other isolated patches above the coal. The pebbles in this forma- 

 tion are usually small ; I saw none exceeding 2 inches in diameter. 



The second terrestrial deposit of consequence in this field is the andesite 

 just south of the Cot-Cot, the extension of which I have already alluded 

 to. I have mapped a series with this formation, which is rather dif- 

 ficult to demarcate and separate from the andesite because when the two 

 are weathered they strongly resemble one another. This series Abella 

 alluded In as tobas, which moans a elastic rock derived from the wear 



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