814 INDEX TO THE STRATIGEAPHY OF NORTH AMERICA. 



The pebbles are of all sizes, from coarse sand to stones several inches in diameter. Quartz 

 is the principal mineral, granite, feldspar, and other minerals also being present. * * * 



It is probable that the Tertiary deposits at one time covered the entire western part of 

 Oldahoma. The valleys of the prestot streams have been carved in these deposits, and in 

 many parts of the Territory aU traces of the Tertiary are gone, except scattered quartz pebbles. 



The thickness of the formation varies with the locality, being greatest on the high divides. 

 Throughout a large part of western Oklahoma its thickness averages 100 feet or more, while in 

 a few localities distant from the streams it may reach as much as 300 feet. On the other hand, 

 in a great many places there is but a thin blanket of the deposit over the red beds. 



I 10-11. SANTA BARBARA COUNTY AND SOUTHERN CALIFORNIA, 



Arnold and Anderson ^^ thus describe the Monterey shale (Miocene) in the Santa 

 Maria oil district, California: 



A great series of fine shales, largely of organic origin, overhes conformably the coarse and 

 fine sedimentary deposits of the Vaqueros. These shales make up the Monterey formation and 

 are representative of the whole of middle Miocene time. The formation is of great thick- 

 ness and is doubly important as the probable source and the present reservoir of the oil. The 

 areal extent of the Monterey is not adequately represented on the map. It doubtless covers 

 as one continuous sheet the whole basin between the Santa Ynez and San Rafael mountains, 

 as well as a large part of these ranges, but it is covered over considerable areas by later deposits, 

 which are in many places very thin. The character, structure, and relations of the Monterey 

 have been the chief subject of the present study. 



The name "Monterey" was given by Wilham P. Blake" in the early fifties to an organic 

 shale formation typically developed in the vicinity of Monterey, in Central California. It is 

 very extensive in the Cahfornia Coast Ranges, being the "bituminous shale" series described by 

 Whitney in the reports of the Geological Survey of California as occurring at widely separated 

 points north and south of the Golden Gate. Its age is generally considered to be middle Mio- 

 cene. It is the source of much of the petroleum found in Cahfornia. The shale that charac- 

 terizes this unique formation is not similar to ordinary clay shale but is composed largely of 

 the remains of minute marine organisms. In its unmetamorphosed condition it resembles 

 chalk but is of sihceous instead of calcareous composition. 



The Monterey in the part of Cahfornia treated here may be divided on hthologic grounds 

 into two parts, although there seems to be perfect conformity throughout the formation. There 

 is no definite dividing line to be drawn, but taken as a whole the lower half, composed chiefly 

 of hard, metamorphosed, in places flinty shales, is distinct from the upper half, in wMch soft 

 shale, giving evidence to the naked eye of its organic origin, is predominant. 



The following summary description of the stratigraphy of the Summerland 

 district, Santa Barbara County, is quoted from Arnold : ^° 



The formations involved in the geology of the Summerland district are 9,000 ± feet of con- 

 glomerate, sandstone, and shale of the Topatopa (Eocene) ; 4,300 ± feet of conglomerate, sand- 

 stone, and shale of the Sespe (Eocene or Oligocene) ; 2,400 ± feet of sandstone and shale of the 

 Vaqueros (lower Miocene); 1,900+ feet of shale and volcanic ash of the Monterey (middle 

 Miocene); 1,000+ feet of conglomerate, sandstone, and clay shale of the Fernando (upper Mio- 

 cene-Pliocene); and 50+ feet of gravel, sand, and clay of the Pleistocene — in all, 18,650+ feet 

 of sediments, practically all of Tertiary age. Unconformities occur between the Monterey and 

 Fernando formations and between the latter and the Pleistocene. 



= Proc. Acad. Nat. Sci. Philadelphia, vol. 7, 1855, pp. 328-331. 



