238 University of California Publications in Geology [Vol. 7 



tinctly determined by an unconformity, the underlying forma- 

 tions ranging from crystalline terranes (Mesozoic or even Paleo- 

 zoic) up to the Tejon (generally accepted as upper Eocene) and 

 the Sespe (considered Eocene or Oligocene). In some areas, 

 where no angular deformation took place, the separation from 

 the Tejon appears to be difficult if the beds near the border are 

 not fossiliferous. The general relations, however, and the con- 

 tributory palaeontologic evidence indicates that there was a dis- 

 tinct discontinuity of conditions between the Tejon and the 

 Monterey, and that there were orogenic movements and a general 

 recession of the sea between those two periods of deposition. 



The relation of the Monterey to the San Lorenzo (referred 

 by Arnold to the Oligocene) is uncertain. These latter beds 

 have not been definitely recognized outside of the Santa Cruz 

 Mountains, where they are said" to lie "in general conformably 

 below the Vaqueros sandstone" (p. 4, col. 1). And again, "In 

 this body of water limestone of the Eocene age, the Butano sand- 

 stone (supposed Oligocene), the San Lorenzo shale (Oligocene), 

 and the Vaqueros sandstone (lower Miocene) were deposited, all 

 (except possibly the Eocene) in conformable" 1 sequence" (p. 10, 

 col. 3). J. P. Smith has recently suggested 92 that this "lowest 

 horizon of the Miocene," the Turritella hoffmanni (or inezana) 

 zone, "may eventually be found to be the inshore equivalent of 

 the deep-water San Lorenzo Oligocene, with which it has a few 

 species in common." In this case the Butano sandstone would 

 probably be the base of the Monterey series for that region. It 

 will require further investigation in the field to satisfactorily 

 settle the question. 



Palaeontologic Characters 

 Fauna. — The fauna of the Monterey series is, at least for the 

 inshore facies, quite distinctive, and with any reasonable devel- 

 opment of fossils in the coarser terrigenous beds their proper 

 assignment to the Monterey period is assured. Professor J. P. 



so U. S. Geol. Surv. Santa Cruz Folio, California, no. 163 (1909). 



si Notwithstanding these definite statements in the text, in the col- 

 umnar section and in the map legends of the folio cited, an unconformity 

 is indicated between the San Lorenzo and the Vaqueros. 



fsProc. Cal. Acad. Sci., 4th Ser., vol. 3, p. 165 (1912). 



