X, A. 4 Pratt: Petroleum and Residual Bitumens 253 



of the intrusions, but there are numerous smaller outcrops east 

 and south of Villaba. 



It is believed that the intrusions have been instrumental in 

 driving the petroleum upward through the surrounding rocks. 

 One of the observed petroleum seeps is on the contact of an 

 apparently intrusive holocrystalline rock in the Vigo shale. All 

 the petroleum and solid bitumen occurrences are near intrusions, 

 and viscous or semiliquid bitumen is found in concretions and 

 brecciated concretionlike bodies, the origin of which may reason- 

 ably be attributed to solutions given off by buried intrusions. 



More detailed descriptions of each of the formations repre- 

 sented in Leyte will be found in the report cited on the Tayabas 

 field, and other observations are recorded in the descriptions of 

 the occurrences of the hydrocarbons in the present paper. The 

 age of the various divisions was determined by Smith from his 

 study of the included fossil remains as follows: Alluvium and 

 littoral deposits. Recent ; raised coral reefs. Recent to Pleistocene ; 

 Malumbang series. Pliocene and upper or middle Miocene ; Can- 

 guinsa clay-tuff, middle or lower Miocene; Vigo shale, lower 

 Miocene or Oligocene. The intrusive rocks are younger than the 

 Canguinsa and are evidently younger than the Malumbang series 

 if they are responsible for the dispersion of the bituminous mat- 

 ter which is observed to impregnate part of the Malumbang 

 series south of Villaba. 



STRUCTURE 



The structure of the Leyte petroleum region has been com- 

 plicated by the intrusions which have penetrated the bedded 

 rocks. The predominant strike is west-northwest. The dips are 

 usually not greater than 30°, but locally they exceed this angle, 

 especially in the Vigo shale, which commonly shows a greater 

 inclination than the overlying beds. There are lines of local 

 folding with dips in opposite directions on either side. Most of 

 these folds trend west-northwest in the direction of the general 

 strike, but this is not universally true. Along the coasts there 

 is a tendency at several places for the strata to dip seaward, the 

 strike corresponding to the general direction of the coast line. 



The bitumens and the intrusive rocks alike appear in or near 

 arches or domes in the structure. Nowhere are they found in 

 clearly defined synclines. 



There is an anticline with west-northwest axis near the head 

 of Butason River. Outcrop D lies on the southern limb, and out- 

 crops A and B lie on the northern limb of this fold. At outcrops 

 E, F, and G, however, the dip is uniformly north-northeast, 

 showing that the fold does not persist far eastward. Between 



