STRUCTURE AND CONDITIONS AFFECTING PRESENCE OF OIL. 75 
the rose-colored or slaglike rock observed at many places in this and 
other oil-bearing regions within the Monterey formation. It is fully 
discussed on pages 48-52. It is the result of tire burning of the hydro¬ 
carbons that have impregnated the shale, and its presence therefore 
indicates where seepages have existed. 
GENERAL STRUCTURAL CONSIDERATIONS. 
The area comprised within the limits of the Lompoc and Guadalupe 
quadrangles has been subjected to two systems of forces acting 
obliquely to each other, the one producing structural features which 
trend northwest and southeast, the other those which trend east and 
west. (See PI. VII.) The system causing the northeast-southwest 
structure was probably the older and dominating one, as it brought 
forth the highest ranges and most extreme folding and conformed 
with the great system which has determined not only the Coast 
Ranges of California but the western border of the North American 
continent. The forces producing the east-west features, although 
exceedingly effective from the west end of the Santa Ynez Range east¬ 
ward to the region south of the end of the San Joaquin Valley, were 
not so far-reaching as those of the other system and probably began 
to exert themselves at a later date. 
That portion of the area under discussion which lies to the north¬ 
east of the Santa Maria Valley is dominated almost completely by 
structural lines trending northwest and southeast; in the extreme 
southern portion lines trending east and west prevail. The region 
between these two areas is occupied by folds and faults, some of whose 
component parts exhibit allegiance to one system and some to the 
other, but whose resultant trend is intermediate between the two. 
In a general way the lines of disturbance as well as the topographic 
relief within this central province radiate fanlike from the point of 
divergence of the Santa Ynez and San Rafael ranges east of the town 
of Santa Ynez. 
The forces acting throughout the region have more often found 
equilibrium in the production of folds than in adjustment by faulting. 
Several important faults are recognizable, however, and doubtless 
others will be revealed by detailed work, especially in the San Rafael 
Range. There is evidence to show that forces have acted intermit¬ 
tently along the same general lines throughout a long period of time. 
DETAILED DISCUSSION OF STRUCTURE. 
In the field study of the structures of the formations and in the 
present discussion special attention has been paid to the structure of 
the Monterey shales, because that formation has apparently given 
origin to the petroleum and in it the bulk of the oil is stored. 
