﻿232 EVELAND. 



River show that the formation has existed, at one time, over a greater 

 area from which it has been eroded. It is probable that field work 

 beyond the district will also show this striking rock. 



ORE DEPOSITS. 



Although the present paper was planned as a contribution to economic 

 geology, the study of the area has shown that the present stage of develop- 

 ment of the ore deposits which have so far been found, does not warrant 

 an extended investigation of them at present, nor would it, under such 

 circumstances, be of more than descriptive value. It is therefore un- 

 necessary more than briefly to touch on the occurrence of valuable ores 

 within this district. 



The native (Igorot) has for a long time, in a semi-skilled manner, 

 worked such gold-bearing rock as has come to his attention, and the 

 presence of the old working naturally led to their exploitation by the 

 American miners, most of whom came in the army of occupation within 

 the last decade. The Bagnio district up to the present time has been 

 prospected or developed in three, more or less distinct, districts, the 

 Kias region, the Copper King or Bued River region, and the Antamok 

 region. In all of these districts, deposits occur, associated with the igne- 

 ous basal diorite or the closely connected volcanics. 



SUMMARY OF THE GEOLOGY. 



The geology of this region shows that we have a basal mass of dioritic 

 rocks as the oldest rock which is laid bare, and this may be accepted as 

 the beginning of the geological history of Luzon, until further data are 

 collected from wider areas. During the gradual and prolonged submer- 

 gence of this base, which is probably an eroded stump in the form of an 

 islet, the basal conglomerate of the Bued River was laid down and on 

 it the rest of the series of sandstone and clays, in which so far no fossils 

 have been found. The limestone of the Bued River was built upon 

 these in perfect conformity, and all paleontologic and stratigraphic 

 evidence so far goes to show that this building occurred during the Mio- 

 cene, after uplift and folding, erosion and base leveling commenced. Fol- 

 lowing this, or possibly at the beginning of the Miocene, that neovolcanic 

 period began which also produced the "eruptive conglomerate" and tuffs 

 at a later time. During this period the ore deposits which may have 

 existed in the basal rocks may have been modified, and later deposits 

 formed. 



To judge from the physiographic evidence, there have been minor 

 changes in level, in addition to normal base-leveling, which have produced 

 the topographic features of the district. 



