670 V. R. GARFIAS 
place mainly along bedding planes, and any barrier, such as the 
basalt intrusions, cutting across the planes of migration, will 
effectively intercept the flow. If resultant conditions are favorable, 
the vicinity of the barrier will become an ideal zone of concentra- 
Fic. 2.—Hypothetical section of a basalt intrusion penetrating the Cretaceous- 
Eocene shales to a point below the surface, illustrating how a deep well might encounter 
only “showings” of oil, and two neighboring shallower wells obtain a fair production 
in the shales. 
tion for the flow of all the lateral channels penetrated, and, owing 
to the large drainage area contributing to the accumulation, this 
will be comparatively large, even if the amount of organic matter 
in the shales is small. In other words, the basalts which intrude 
