Clark: The San Lorenzo Series of Middle California 63 



Devil's Den region and southwest of Wagon Wheel Mountain, a 

 series of sandstone and shale was found below the Vaqueros with a 

 thickness of nearly two thousand feet. The following statement is 

 made concerning the age of these beds: 



With the exception of Pecten peckhami Gabb, which ranges from the Eocene 

 or Oligoeene to the Miocene, the stratigraphic position of none of the fossils men- 

 tioned is known. The stratigraphic affinities of the beds are with the Eocene, 

 and while the palaeontologic are with the lower Miocene, they are possibly to be 

 correlated with the white diatomaceous shale tentatively mapped with the Tejon 

 in the Coalinga district and may possibly be of Oligoeene age. 



In a recent paper by Robert Pack and Robert W. Anderson, 11 a 

 series of shales, the Kreyenhagen shales, found in the region of 

 Coalinga and to the north, are placed questionably in the Oligoeene. 

 These are the shales referred to as the white shale in the extract given 

 in the paragraph above ; they were described by Arnold and Ander- 

 son 32 in their paper entitled, "Geology and oil resources of the 

 Coalinga district, California," and doubtfully referred to the Tejon. 

 The following quotation in reference to these shales is taken from 

 the paper by Anderson and Pack : 



In the report on the Coalinga district this body of shale was included tenta- 

 tively with the Tejon (Upper Eocene) and treated as an upper member of that 

 formation, although the possibility of its being of Oligoeene age was pointed out. 

 Positive evidence as to the exact age of this shale is still lacking but numerous 

 facts lead to the belief that it constitutes a distinct formation more recent in age 

 than the Tejon. This conclusion, combined with the evidence afforded by the 

 fauna, which, though meagre, is distinct, from that of the underlying and over- 

 lying formations and is suggestive of the Oligoeene, warrants the tentative 

 assignment of these beds to the Oligoeene series. 33 



Fossils collected by John Ruckman from the Kreyenhagen shale, 

 which are in the collections of the Department of Palaeontology of 

 the University of California, show conclusively that these beds are of 

 Oligoeene age and belong to the San Lorenzo series, as defined by the 

 writer in this paper. One of the common species found in this col- 

 lection is Fusinus (Exilia) lincolnensis Weaver, the type of which 

 came from the Lincoln beds in southern Washington, which beds are 

 considered by Weaver to be of Lower Oligoeene age ; associated with 

 it are Macrocallista pittsbvrgensis Dall and Lcda lincolnensis Weaver, 



31 Anderson, Eobert, and Pack, Robert W., Geology and oil resources of the 

 west border of the San Joaquin Valley, north of Coalinga, California, U. S. Geol. 

 Surv., Bull. 603, pp. 1-220, pis. 1-14, 1915. 



32 Arnold, Ralph, and Anderson, Robert, TJ. S. Geol. Surv., Bull. 398, pp. 1-354, 

 pis. 1-52, 1910. 



33 Anderson and Pack, op. oit., p. 74. 



