258 2^^^ Philippine Journal of Science lais 



brought about by the same solution. The question of the origin 

 of the breccias will require further study. Several mineral 

 springs occur in northwestern Leyte, and analyses by the Bureau 

 of Science of the waters from one of them, situated at Villa- 

 hermosa, north of San Isidro, show an extremely high car- 

 bonic acid content with fair quantities of calcium, sodium, and 

 magnesium. 



The analysis of the clay-tuff at first sight does not bear 

 out the conclusion that tuff is an important part of the rock. 

 The silica-alumina ratio, however, is approximately the same 

 as that of tuff in Cebu, which can be correlated stratigraphically 

 with the Leyte clay-tuff, and the calcium, magnesium, and iron 

 salts can be accounted for as additions from the sea water into 

 which the tuff fell. 



The total quantity of bitumen in sight at D is insignificant, 

 but exploration might reveal a greater quantity and at the same 

 time yield valuable information as to the origin of the bitumen 

 deposits. 



Outcrop D is in the general vicinity of the Mount Tabeyta 

 intrusion, although at some distance (3 kilometers) from the 

 peak itself. A clay-shale-breccia cemented by calcite and quartz, 

 as has already been noted, was found on the summit of Mount 

 Tabeyta. The suggestion may be put forward that the breccias 

 and concretions at outcrop D are related to buried intrusions 

 in their origin. The solutions which have impregnated the 

 breccias and concretions might conceivably have been given off 

 by an intrusion, but the manner in which the brecciation was 

 accomplished without disturbing the surrounding clay-tuff beds 

 is not clear. Although the Canguinsa clay-tuff is slightly petro- 

 liferous, there is certainly not enough bitumen in it to account 

 for the concentration represented by the bitumen-cement in the 

 breccias. Bitumen must, therefore, have been introduced into 

 these broken rocks and solution channels, and the most reason- 

 able assumption is that it ascended from a source in the under- 

 lying rocks — that is, from the Vigo shale. 



Outcrops E, F, and G are pockets and irregular deposits of 

 a solid, brownish black bitumen in Canguinsa clay-tuff. There 

 are several other unmarked outcrops in the same region. The 

 pockets follow bedding planes in the clay-tuff in a rough way, 

 but also cross the beds irregularly and fill vertical openings 

 in the formation. Several outcrops have been explored by short 

 tunnels and by shafts, and a total quantity of perhaps 100 

 tons of bitumen has been recovered. The thickness of the 

 deposits is rarely more than 1 meter, and some of them have 



