94 
SANTA MARIA OIL DISTRICT, CALIFORNIA. 
more or less in thickness, composition, and yield from well to well. 
The most persistent zone in that part of the field which is best 
developed at the present time is the second, or B zone. Above 
this in many of the wells is zone A; in others zone C is penetrated 
below it. The upper zone in the eastern group of Western Union 
wells, although above what is supposed to be the horizon of B, is 
probably considerably above the A zone of the northern part of the 
field, where it appears to have no correlative. 
With the exception of the lowest zone in the wells in the eastern 
part of the field and of a few others mentioned in the detailed dis¬ 
cussion of the local areas, the oil zones appear to represent fractured 
portions of the shales, the interstices in the breccia or possibly joint 
cracks in the beds being the reservoirs for the storage of the oil. 
The exceptions to the brecciated productive zones are apparently 
typical sands and gravels. 
HALL-HOBBS RICE RANCH AREA 
LOCATION AND STRUCTURE. 
The area here discussed comprises the California Coast, Meridian, 
Coblentz, Santa Maria Oil Company (Keyser), Hall & Hall, New 
Pennsylvania, Rice ranch, and Dome properties and the north¬ 
eastern part of the Hobbs lease, and occupies the ridges and canyons 
which extend northward from the east end of the main Graciosa 
Ridge. The wells are located on the northwestern flank of the 
Mount Solomon anticline, at or immediately northwest of the ter¬ 
ritory, in which it swings from a northeastward to a southeastward 
trend. In addition to the main anticline there appear to be one or 
more local flexures involved in the structure of the field, the Hobbs 
anticline and the syncline between it and the Mount Solomon anticline 
being the most prominent. The characteristics and extent of these 
features as they are believed to exist are portrayed on the contour 
map (PI. X). 
GEOLOGY OF THE WELLS. 
• • 
Nearly all the wells in this area, with the exception of the Hall, 
Meridian, and Coblentz start down in the Monterey shale. Those 
farthest away from the top of the ridge, other things being equal, 
have to penetrate farthest through the Fernando clay, sand, and 
conglomerate. Up to the present time the greatest thickness of the 
Fernando penetrated before reaching the shale is 650 feet, and much 
trouble was experienced in going through it in this well, the forma¬ 
tion being mostly sand. From the top of the Monterey shale to the 
bottom of the wells the rocks are largely blue and brown shales, 
with only here and there interbedded hard “shell” layers. In fact, 
