418 The Philippine Journal of Science 1923 



visions of the past through the well-trained eyes of the expert 

 scientist. 



The next worker in this field was A. J. Eveland, who con- 

 tributed an excellent article upon the geology and mineral 

 prospects in the Baguio region. Eveland published with this 

 report a good reconnaissance map of the Benguet mineral 

 regions, upon which are outlined the various geologic forma- 

 tions. Eveland recognized the peneplain character of* Baguio 

 Plateau and gives an excellent description of it. He says in 

 part :* 



The Baguio Plateau is the most striking of the four physiographic 

 types of the region. It is a peneplain of limited extent, with an 

 average elevation of about 5,000 feet and with a drainage and topography 

 so characteristic of a lowland region, that, viewed from a central point 

 where the valleys of the Bued and Agno River drainage are not visible, 

 it is hard to realize the situation of the area. 



Eveland also recognized that Mount Santo Tomas was a 

 block mountain upthrust above the plateau by movements along 

 a fault bounding this mass on the northeast. In the same 

 publication Smith discusses the petrography of the rocks of 

 this region. 5 



Four years later Smith and Eddingfield 6 presented a revised 

 map of the Baguio region, revised the geologic scale, and gave 

 additional notes upon the economic geology of the region. 



GEOLOGY 



GENERAL STATEMENT 



The oldest rocks exposed in the vicinity of Baguio occur in 

 Antamok Valley (Plate 2) . These rocks represent a portion of 

 the basement complex of schists, diorites, slates, and cherts 

 which form the backbone of most of the larger islands of the 

 Philippine Archipelago. In Antamok Valley the basement com- 

 plex is represented by a characteristic plutonic rock, a diorite. 

 This diorite is technically described by Smith. 7 It seems 

 possible that this diorite is intrusive in the slates and cherts 

 of probable Jurassic age. 



The next oldest rocks are the conglomerates, sandstones, and 

 carbonaceous shales of Miocene age, and they are best seen in 



4 Philip. Joum. Sci. § A 2 (1907) 219. 



'.Smith, W. D., Petrography of some rocks from Benguet Province, 

 Luzon, P. I., Philip. Journ. Sci. § A 2 (1907) 235. 



8 Smith, W. D., and Eddingfield, F. T., Additional notes on the economic 

 geology of the Baguio mineral district, Philip. Journ. Sci. § A 6 (1911) 429. 



7 Philip. Journ. Sci. § A 2 (1907) 235. 



