1916] Nomland: Invertebrate Zones of Jacalitos and Etchegoin 79 



of the Etchegoin. In this paper Arnold and Anderson stated that 

 for the Etchegoin, "The upper limit is not defined for the hills north 

 of Coalinga owing to the indefiniteness of the line between the Etche- 

 goin and Tulare there." As will be shown in this paper, the Mya 

 zone, which corresponds to the uppermost Etchegoin in other parts 

 of this district, and also other corresponding zones have been dis- 

 covered north of Coalinga in the typical section of that formation. 



Jacalitos and Etchegoin Northeast op Coalinga 



The base of the Jacalitos as defined here is the first gravel above the 

 fossiliferous Santa Margarita formation. This is taken from the 

 detailed mapping of J. H. Ruekman, according to whom some of the 

 thick beds of gravel seen near the anticline become thinner and also 

 more sandy and finally shaly on being traced northward. Ruekman 

 also shows that the basal gravels unconformable above the Santa Mar- 

 garita consists of a member somewhat lower than the one mapped as 

 such by Arnold and Anderson. In these basal gravel beds we find a 

 large amount of silicified wood and gypsum. Immediately above this 

 occurs a member of brown, red, gray, and otherwise highly colored 

 clays. Leaf impressions are abundant. These conditions seem to 

 indicate that these beds are terrestrial deposits. 



About two hundred feet above the base we have other gravel beds 

 which seem to have been mapped as the basal Jacalitos by Arnold and 

 Anderson. Possibly these beds may be unconformable with the under- 

 lying clays. It was in this zone that Arnold and Anderson reported 

 finding a tooth of PlioJiippus. From these gravels upward to the top, 

 the Jacalitos consists largely of soft yellowish clays with interbedded 

 vivianitic sandstone and conglomerate. 



The exact relations of the Jacalitos and Etchegoin as mapped by 

 Arnold and Anderson in the field north of Coalinga are a matter of 

 doubt, since we have in the northern field two series of beds appar- 

 ently conformable, in the lower of which no invertebrate fauna has 

 been found. The two series of beds in the southern part of the district 

 with which the Jacalitos and Etchegoin here described have been 

 correlated are, however, said to be unconformable and to have faunas 

 which are somewhat different. 



In the basal Etchegoin the low, dark bluish-colored hills show 

 exposures of a coarse-grained, slightly consolidated, vivianitic sand- 



Publication in press. 



