The Los Angeles Basin 275 



eastern borders of the Los Angeles Basin are commonly sepa- 

 rated from the adjoining upland areas by high-angle faults or 

 fault zones. Such fault zones pass along the southern base of 

 the Santa Monica Mountains, through Hollywood and Los 

 Angeles, and along the southern border of the Puente Hills. 

 The fault which marks the southern boundary of the Puente 

 Hills, it may be remarked in passing, extends southeast forming 

 the east boundary of the Santa Ana Mountains, and is known 

 as the Whittier fault. Oil has been trapped within and just 

 south of these fault zones in Pliocene and Miocene rocks that 

 have been bent into minor folds since they were laid down. 

 Surface seepages of oil along fault zones and along outcrops of 

 sand-rock early attracted the attention of prospectors and 

 resulted in the production of oil as early as 1880 (H. W. 

 Hoots) . 



The Los Angeles oil fields lie in a zone extending in a gen- 

 erally east-west direction immediately north of the business 

 center of the city. The axis of the Los Angeles anticline ex- 

 tends from west of Los Angeles River west of Sunset Boulevard 

 and northwest of the Sisters' Hospital almost in a straight line 

 to a point in Benton street 200 feet south of First. Near this 

 point the axis of the anticline bends and passes to the northwest 

 toward Colegrove. The zone of faulting and fracturing in 

 which the productive oil wells occur lies to the south of the 

 axis of the anticline in a generally east-west direction. The 

 anticlinal axis is an expression of a deep-seated fold in the rocks, 

 which dates back to Miocene time and the disturbances which 

 marked that period in southern California. The fault zone in 

 which the oil fields occur dates from Pleistocene time when the 

 Miocene and Pliocene sandstones and shales were faulted and 

 shattered. 



Oil Fields Determined by Structural 



Features 



The oil fields occur in a zone of faulting which lies a few 



