GEOLOGIC RECONNAISSANCE OF SOUTHWESTERN LUZON. 71 



the entrance to Manila Bay. The lower slopes of the mountains descended 

 to the coast gradually and at the shore are cut off abruptly in sea cliffs. 

 In these cliffs the marine conglomerates are well exposed. West of Ter- 

 nate they are in many respects similar to the beds on Corregidor Island. 

 They were also seen in the cliffs of Carabao and other islands near the 

 shore and in the jagged coast line south, to the vicinity of Nasugbu. 

 In this part of the coast, which is exposed toward the China Sea, they 

 have yielded more readily to erosion, and deep inlets and coves have 

 been formed. The conglomerates are found up to an elevation of about 

 200 meters north of Nasugbu. The bowlders in the conglomerate are 

 mostly andesitie. The finer materials are in part derived from erosion 

 of igneous rocks, but to a considerable extent they are tufaceous. Some 

 of the tufaceous material may have come from the denudation of deposits 

 on the mountains of the western cordillera, but it is probable that much 

 of it is the equivalent of the great tuff area found in the southwestern 

 volcanic region. This is suggested by the fact that the Pico de Loro 

 Mountains on their eastern flank are partially overlaid by water-laid 

 tuffs. Near Ternate and ISTaic the conglomerates apparently grade into 

 the deposits of water-laid tuffs which have a great extent in the adjacent 

 plains. 



Tufaceous foraminiferal marls. — A tufaceous foraminiferal marl, 

 which was discovered and described by Von Drasche, occurs on the 

 western base of the sierra along the coast from Palanag to Santa Cruz 

 and perhaps further north. This author reports it as extending up to 

 an elevation of 400 feet. Felix Karrer determined the fossils from this 

 formation and assigned it to the younger Miocene. This formation may 

 correspond to the marine conglomerates which are found on the flanks 

 of the southern portion of the cordillera. 



Geologic history. — The early history of the western cordillera and the 

 succession of the igneous rocks which constitute its principal area is not 

 yet plain. The younger sedimentaries on its flanks, however, give a key 

 to some of the later changes which have taken place. Von Drasche, who 

 crossed the northern part of the range, says : "There may have been a 

 time when the sierra Zambales (western cordillera) stood in the sea in a 

 form similar to. that which Paragua Island (Palawan) now has. On 

 the west of the island the foraminiferal marl was built up from the 

 volcanic detritus under the action of the sea, while on the east it was 

 covered by a heavy mass of tuff mixed with bowlders of volcanic rock. 

 Through continued uplift the great central plain of Luzon finally became 

 dry land and apparently it is even yet rising." 



The relations of the marine conglomerates described in this report 

 furnish additional proofs of the supposition of Von Drasche, which was 

 based upon the evidence of the foraminiferal marls, and indicate an 

 emergence of the cordillera amounting to as much as 200 meters. In 



