abstracts: geology 441 



ments. Scales of fishes from the Chico, cut oflf from the inland sea by 

 the western uplands, are all different from those in Rocky Mountain 

 deposits. The Chico has a veritable clupeid, but so far no genuine 

 clupeids have been found in the Benton, Niobrara, Pierre, or Fox 

 Hills. The inland waters seem to have lacked berycoids, which are so 

 characteristic of the European strata. R. W. Stone. 



GEOLOGY. — Structure and oil resources of the Simi Valley, Southern 

 California. W. S. W. Kew. U. S. Geol. Survey Bull. 691-M. Pp. 



323-347. pl- 4. fig- I- 1919- 



This report describes a small oil field about 32 miles northwest of 

 Los Angeles, in the Simi Valley, Ventura County. All the rocks within 

 the Simi Valley district are of sedimentary origin with the exception 

 of a few small areas of basic igneous rocks of Miocene age. The greater 

 part of the Simi Hills is composed of rocks of Chico (Upper Cretaceous) 

 age. In the Simi Valley district, as in other localities in California, 

 the Eocene comprises both the Martinez (lower Eocene) and the Tejon 

 (upper Eocene) formations. Although these divisions are elsewhere 

 separated by an unconformity, the series, consisting of 3,500 to 6,500 

 feet of conglomerates, sandstones, and shales of various types, here 

 appears to be homogeneous. 



The Monterey group (Miocene), which in the Simi Valley district is 

 divided into the Vaqueros sandstone and Modelo formation, is one of 

 the most widespread series of rocks in California. The Fernando 

 formation is exposed in a series of irregular areas along a synclinal 

 region between the Santa Susana Mountains and the Simi and San 

 Fernando valleys. It lies with a marked unconformity on all the older 

 formations. 



The structure, or attitude of the different strata in the Santa Susana 

 Mountains and Simi Valley js closely related to that of the California 

 Coast Range, which is characterized by a number of northwestward- 

 trending folds, broken by faulting. The Simi Valley oil district lies 

 in the midst of the westward-trending ridges of the Coast Ranges and 

 embraces a part of two large structural features, the Santa Susana 

 Mountains and the Simi Hills. In this region the dominant structure 

 is a result of compressive forces which acted from north to south at 

 the end of the Pliocene epoch. The principal structural feature in 

 the Simi district is the Santa Susana fault which follows closely the 

 foot of the steep southern front of the Santa Susana Mountains. The 

 Simi anticline is economically the most important structural feature 



