100 GUIDEBOOK OF THE WESTERN UNITED STATES. 



To a geologist one of tlie most impressive sights of the whole trip 

 from Los Angeles to San Francisco is the great escarpment of thick- 

 bedded Eocene sandstones which blocks the west 

 Chatsworth. end of the San Fernando Valley. From the east the 



Kiovation 952 feet. bcds ETC Seen to He onc on top of another to a height 



S^Smiie., «f ^^^^^y 1>200 feet above the valley. The continua- 

 tion of tlicse beds, whose edges are thus visible, lies 

 under the San Fernando Valley, and the escarpment indicates a 

 great break in the earth's crust along which the rocks on the north- 

 west side have been heaved up or those on the southeast side have 

 sunk. In other words, the steep slope that closes the west end of 

 the valley is a fault scarp. The faulting took place many hundreds 

 of years ago and the cliff has, of course, since been modified by the 

 action of water and air. This great fault extends from the south- 

 west corner of the valley in a north-northeasterly direction into the 

 Santa Susana Mountains. Tlie Eocene sandstones are eroded into 

 grotesque shapes, some of them susrsrestive of battlement 

 steeply above the raih'oad. 



Sandstone from the Topatopa formation (Eocene) quarried 2 miles 

 northwest of Chatsworth is utilized for the San Pedro Breakwater 

 and also as a building stone. 



After passing through two tunnels which penetrate minor ridges the 

 railroad goes through a tunnel, 7,369 feet long, about 500 feet below 

 the Santa Susana Pass. The line between Los Angeles and Ventura 

 counties is crossed midway of this tumiel. The Eocene beds (Topa- 

 topa) dip west at a rather low angle, so that the tunnel, from east to 

 west, cuts successively younger or higher beds in the formation. 

 Soon after leaving the tunnel, the train goes through some cuts of 

 coarse Eocene conglomerate which overlies the beds just described. 

 These rocks form the east end of Simi (see'me) Valley, which comes 

 into view as the tram proceeds westward beyond the tunnel. 



Although the Eocene series here is more than 3,000 feet thick, the 

 dip of the beds to the west soon carries them out of sight under the 



younger formations. The rocks immediately over- 

 Santa Susana. Ijmg the coarse Eocene sandstone and conglomerate 



STnS'm^^^ ^""^ ^""^^ rusty-bro^ra sandstones of OUgocene age- 



the Sespe formation. On the north (right) sido of 

 the valley, opposite milepost 436, oil derricks of the Newhall field 

 are seen m the distance near the base of some low hills lying in front of 

 the main Santa Susana Range. These derricks mark the position 

 of .wells that penetrate the uppermost beds of the Eocene (Topatopa 

 formation), on the flanks of a well-developed arch or anticline in 

 these bods. The anticline extends eastward along the base of the hills. 

 The wells range in depth from 300 to 1,800 feet and yield from 5 to 

 200 barrels each daOy of 37° Baume o± the be^t oil in the State. 



