viii, a, 5 Pratt and Smith: Petroleum Resources 361 



that petroleum is of organic origin. In the other school are those 

 who believe in the inorganic origin of petroleum, some of whom 

 assert that there is a close relation between volcanic activity 

 and the production of the natural hydrocarbons. It is only fair 

 to admit, that the matter is by no means settled and that there 

 is much which seems to support the inorganic theory. 



The conditions of vulcanism under which petroleum is supposed 

 to originate are still obscure, and it is impossible to say what 

 kind of volcanic activity gives rise to petroleum. Coste, 19 the 

 principal adherent of the volcanic theory, believes that the origin 

 of oil is associated with solfataric emanations, If this be so, 

 there are numerous localities in the Philippines where it might 

 be advantageous to prospect. In the Tayabas field, however, 

 where more oil is encountered than anywhere else in the Archi- 

 pelago, the phenomena of vulcanism are least abundant and 

 solfataric activity is unknown. 



The observed facts bearing upon the question of the source of 

 oil in this field are: 



1. The formations are practically all sedimentary. Small 

 isolated patches of volcanic agglomerate occur, but these are 

 confined to the northeastern portion of the field and aside from 

 the presence of this agglomerate there is no evidence of volcanic 

 phenomena. 



2. The known oil seeps are associated with bluish to brownish 

 black shale and subordinate sandstone which occurs in the Bacau 

 stage of the Vigo shale. Where traces of oil are found below 

 the Bacau stage, they are always associated with beds of fine- 

 grained compact shale. Material of this character occurs in 

 other formations above the Vigo shale, but no petroleum has been 

 observed in the upper formations. 



3. In the petroliferous shale are numerous tests of Globigerina 

 (Plate V) and some minute fragments of carbonaceous matter. 



4. Globigerina has not been noted except in the Vigo shale. 

 They were found most abundantly in the Bacau stage, but occur 

 also at lower horizons. 



5. None of the oil seeps in Tayabas appears to give off a large 

 quantity of petroleum. However, all trace of the oil which is 

 seen to be given off disappears in a remarkably short time, due 

 probably to the light nature of the oil. Hence, it is possible 

 that the quantity of oil which escapes from the seeps is larger 

 than it appears to be. 



6. Natural sections afford opportunity for the examination 



19 Trans. Am. Inst. Min. Eng. (1906), 35", 288. 



