﻿392 SMITH. 



BASAL CONGLOMERATE. 



The basal conglomerate, in some places at least, overlies the igneous 

 basement ; however, this does not appear anywhere to have the strong 

 development it has in the Benguet region. 



This conglomerate marks an unconformity, probably the greatest break 

 in the stratigraphic column within the limits of the Archipelago, and it 

 differs from the conglomerate in the coal measures by the fact that all the 

 included pebbles are igneous, whereas in the case of the latter they are 

 mixed with sandstone, shale, etc., clearly showing that they were not 

 altogether derived from the basal mass. It would be difficult to determine 

 the age of the basement complex, but it is certainly pre-Miocene. ■ 



In the region of Sili Creek we find a formation which, taken altogether, 

 I call a greenstone. Some phases of this are certainly diorite, others are 

 porphyritic, and near the head of the creek, at 380 meters (1,250 feet), 

 there is a dark phase of rock -which may be a diabase and hence a dike, 

 but the extremely limited exposure of the outcrop prevented my being 

 absolutely certain. A very important question affecting our knowledge 

 of the extent of the coal on the north side of the Danao River, is whether 

 or not this upper portion of the formation in Sili Creek might not be 

 an intrusive or even an extrusive, like the flow south of the Cot-Cot River. 

 We might then, in the event of this proving to be so, expect to find 

 the coal beds below and possibly exposed somewhere in the bed of Sili 

 Creek. Nowhere in this channel was any coal formation encountered, 

 but on the other hand a clean section of several hundred feet of green- 

 stone was observed. 



I found the greenstone in this stream at an elevation of 238 meters 

 (780 feet) with marked jointing, the directions and dips of which are 

 as follows: S. 25° E., dip 60° NE. ; N. 82° W., dip 76° XE. ; S. 40° W., 

 dip 40° SE. 



THE COAL MEASURES. 



I have divided the coal measures into two subdivisions for purposes of 

 convenience in description, although in the field I have found no sharp 

 line between these. The lower part of the measures consists of gray 

 shales, the upper portion of a coarse, gray sandstone. There are five 

 coal seams. I have mapped the slates and sandstone under one color 

 (the blue), because it is practically impossible to separate them in the 

 field. 



The photograph (PI. II) shows the contact of the coal measure shales 

 with the basal conglomerate. It also shows the intense plication in the 

 weaker rocks, where they abut on the resistant igneous base. 



The shales, as this stream (the Suqui) is ascended, become more and 

 more coarse until the coal seams are encountered where a grit appears. 

 There are about GO or 100 centimeters (2 or 3 feet) of clay and shale, 

 just above the "Enriqueta"' vein, then the coarse gray sandstone comes 



