426 The Philippine Journal of Science 1923 



trail begins to zigzag, and another abrupt change occurs. No 

 evidence of faulting was found except this sudden topographic 

 change, but taken with the faults previously observed the writer 

 regards the point of change as marking a fault. In this final 

 steep climb to the top of Mount Santo Tomas andesitic agglom- 

 erate, andesite, and andesitic conglomerate were successively 

 noted. The last-named member has a steep westerly dip of 78°. 

 The andesite and andesitic conglomerate may be pre-Malum- 

 bang in age, and associated with the Vigo in part as intrusives. 

 Practically the same types of andesite, andesitic agglomerates, 

 and andesitic conglomerates are found on the east side of Bued 

 River Canon at the Copper King mine, now known as the 

 Demonstration mine, where this material is probably in fault 

 contact with a coarse sandstone of possible Vigo age, since 

 pebbles of diorite, apparently derived from the basement com- 

 plex of diorites and schists, were embedded in it. 



At the foot of the Zigzag on the Baguio Road in Bued Canon 

 a dark gray to black limestone occurs (Plates 1, 2, and 7) . This 

 limestone yielded the following fauna: 



Stylopkora cf. mordax Dana. Tellina sp. a. 



Avicula sp. Tellina sp. b. 



dementia papyracea Gray. Venus purpera Linnaeus. 

 Mactra (?) sp. 



This fauna is referred to the Malumbang, and the dark color 

 of the limestone is probably due to infiltering waters. 



BAGUIO FORMATION 



Andesitic tuffs and breccias of late Pliocene or early Pleis- 

 tocene age which rest unconformably upon marl of the Malum- 

 bang formation are assigned to the Baguio formation of Smith. 

 The writer does not limit this formation to that portion con- 

 taining silicious-spring deposits, but regards the silicious-spring 

 material as a later and adventitious deposit of no great impor- 

 tance from the point of view of the student of historical geology. 

 This use of the term "Baguio formation" is much broader than 

 that of Smith, who first used the name; but, since the city of 

 Baguio is built upon these andesitic tuffs, agglomerates, and 

 breccias, and these rocks are finely exposed here, the writer 

 thinks best to extend the name. Eveland's reconnaissance map 

 of the Baguio region shows the areal extent of this formation. 

 The materials in this formation were practically all derived 

 from a neighboring volcano or volcanoes, and apparently all 

 were deposited upon land or in shallow lakes. Certain outcrops 



