X, A, 3 Smith: Reconnaissance of Mountain Province 187 



question. From the observations of Carpenter on the coast of Florida he 

 holds that the formation of coral reefs is possible even from great depths 

 and explains the different vi^ays of emergence, by the influence of currents 

 and other factors. 



The presence of coral reefs elevated to a considerable height is not 

 peculiar alone to those regions in the Philippines visited by me. Semper 

 also mentions similar occurrences in northern and eastern Luzon and in 

 Mindanao. Junghun also speaks of elevated coral reefs on the southern 

 coast of Java. 



The greater part of the tuffs and tuff -sandstones are unquestionably older 

 than the raised coral reefs. These tuffs, even though we admit excessive 

 faulting and folding, of which I could find no clear evidence, however, are 

 extraordinarily widespread. From Aringay to Benguet, which has an 

 elevation of 4,000 feet above sea level, they occur without interruption and 

 likewise from Nueva Cobeta almost to the western slope of Tovalina Pass 

 (nearly 2,000 feet). The included coral strata point to extended periods 

 of rest in the formation of this complex, whereas the remains of dicotyle- 

 donous plants in the marls indicate the nearness of land. The coal measures 

 of Angaqui and Aringay, which I did not examine personally, may very 

 possibly form part of the same formation. In the basal rocks of northern 

 Luzon, finally, we must include the Agno beds: diabase, gabbro, syenite, 

 diorite, aphanite, and the protogine gneiss, which perhaps is the oldest of 

 all. That the Agno beds have derived their material principally from the 

 underlying greenstone and are, therefore, younger than the greenstone has 

 already been mentioned. 



It is highly interesting that a very similar bedded complex has also 

 been found by Minard on the Island of Mindanao; it appears that in Min- 

 danao these rocks are the source of gold (Sur les gisements d'or des 

 Philippines, Bull, de la Societe geolog. de France, 2, 3d series, 403). The 

 gold is obtained from the gravels which the Rio de Iponan carried 

 down from the interior, as well as from steep alluvial terraces which 

 lie at the bases of the mountains. The most important rocks which 

 are met with in Iponan Valley, according to Minard, are conglomer- 

 ate and various kinds of sandstones with calcareous cement, covered 

 over at many places by coralline limestone. The strata are broken through 

 at numerous places by diorite and serpentine, and their inclination is about 

 12°. The stratigraphic order of these rocks is as follows: Shale (thickness 

 unknown) ; conglomerate derived from various classes of rocks (thickness, 

 100 meters) ; grit derived from various classes of rocks (30 meters) ; 

 argillaceous coralline limestone (30 meters) ; laminated clay (15 meters) ; 

 ancient alluvium not gold-bearing (10-12 meters) ; recent gold-bearing 

 alluvium (6-8 meters). The conglomerates are composed of the following 

 kinds of rocks: 1, Black, coarsely laminated amphibolite; 2, diorite, with 

 large amphibole crystals and triclinic feldspars as essential minerals and 

 pyrite, quartz, and epidote as accessory minerals; 8, some specimens inter- 

 mediate in character between the amphibole-diorite and the amphibolite- 

 diorite of medium-grain size; 4, granitoid diorite with much mica; 5, 

 aphanite; 6, granular marblelike feldspar in which granite and amphibole 

 occur in bands; 7, serpentine diallage (magnetic), variety of ophiolite; 8, 

 precious serpentine with asbestos veins; 9, diorite porphyry; 10, augite 

 porphyry; 11, quartzose epidote; 12, jasper in beautiful modifications. 



