276 Adventures in Scenery 



miles north of Los Angeles. What is called the eastern field 

 extends from the vicinity of the Catholic Cemetery at Buena 

 Vista and Sutherland streets westward to the Sisters' Hospital. 

 Lying west of the Sisters' Hospital and extending westward to 

 a line running north through West Lake is the central field. 

 Extending north and west from the region about the Baptist 

 College to the south of Colegrove is the western field. To the 

 southwest is the Salt Lake field, in which the tar pits of Rancho 

 La Brea are located. 



The structural features of the region about Los Angeles, 

 which determine the location of the oil fields, represent two 

 systems of disturbances. The older, of Miocene age, consists 

 primarily of folds, with many minor faults. The younger, in 

 which faults predominate, is of Pleistocene age. The structure 

 of the Los Angeles Basin as it pertains to petroleum is related 

 to the later system of fractures. These trend diagonally north- 

 west and southeast across the basin. The larger oil pools are 

 associated with anticlinal structures along fractures or fault 

 lines. The oil pools occur upon short anticlinal folds which 

 join the main fold or fault at angles in stair-like fashion (what 

 geologists call en echelon) . The anticlinal structures along 

 these fractures (both the main faults or folds and the shorter 

 branches) are apparently a result of predominantly horizontal 

 movements in the rocks which probably occurred at the same 

 time with the general mountain-building disturbances which 

 occurred in southern California in late Pliocene and Pleistocene 

 time. According to Eaton"" the predominantly horizontal 

 folds and faults in the deep-lying rocks are probably the result 

 of crustal movements deep in the earth which have resulted in 

 a relative movement or shifting of the rocks of the basin from 

 southeast to northwest along the coast and from northwest to 

 southeast upon the landward side; in other words, deep-seated 

 forces in the earth have caused a twisting or whirling or rotat- 

 ing of the rocks of the basin, as though the rocks of the basin 



* J. E. Eaton, "Geology of the Los Angeles Basin," A.A.P.G. Bull. 10. 



