212 University of California Publications in Geology [Vol. 7 



Summerland District, Arnold, 1907. — In the "Geology and 

 Oil Resources of the Summerland 50 District ' ' which appeared this 

 same year, Arnold describes the "Vaqueros formation" and the 

 "Monterey shale." These designations were used and were easy 

 of application because the territory studied lies within that 

 coastal belt where the Monterey period of deposition opened 

 with a sandy facies with subordinate shales (785 feet thick in 

 the locality described) graded into predominant clay shales with 

 calcareous shales and concretions (1650 feet near Summerland) 

 and finally into dominant diatomaceous shales and siliceous cherts 

 with occasional ash beds. The lower sands and terrigenous shales 

 are said to contain no characteristic fossils, but their "strati- 

 graphic position and lithologic similarity" to the fossiliferous 

 beds already described in the Santa Clara District "leave no 

 doubt in the mind of the writer as to its correct correlation" 

 with the Vaqueros. The dominant diatomaceous shales in the 

 upper part of the series are called "Monterey shale" and contain 

 besides the microscopic organisms a few species of the shale 

 fauna of Merriam. Here we return to the distinction based 

 on lithologic types, but divided as in the Santa Clara District 

 (and not as originally by Fairbanks farther north) for reasons 

 already discussed. 



Santa Maria District, Arnold, and Robert Anderson, 1907. — 

 In their bulletin 57 on the "Geology and Oil Resources of the 

 Santa Maria Oil District. Santa Barbara County," Arnold and 

 Robert Anderson used the same classification that was used in 

 the Summerland district just described. The Vaqueros for- 

 mation was placed in the " Tejon-Sespe-Vaqueros terrane," as 

 they considered that the purpose of the bulletin did not Avarrant 

 the time necessary to trace the lines between the constituent 

 members. A table of "Vaqueros (lower Miocene)" fossils and 

 localities is given (p. 32). The "Monterey shale (middle Mio- 

 cene)" is said to follow the Vaqueros conformably, the division 

 being placed on lithologic ground at the end of the calcareous 

 shales and beginning of the dominantly siliceous shales. The 

 Monterey shale is said to be 5200 feet thick. 



3«U. S. Geol. Surv. Bull. 321 (1907). 



r ' 7 U. S. Geol. Surv. Bull. 322 (1907); also earlier briefer account in 

 Bull. 317 (1907). 



