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University of California Publications in Geology [Vol. 9 



in this region. Since this occurence offers a somewhat unusual oppor- 

 tunity for the comparison of the invertebrate and vertebrate time- 

 scales of California in the upper Miocene and lower Pliocene and of 

 the invertebrate faunal zones of the western with those of the eastern 

 part of the continent, a more or less detailed description is here 

 presented. 



The locality at which this relationship of vertebrate and inverte- 

 brate faunal zones has been studied is located about nine miles north- 

 northeast of Coalinga and east and northeast of the small town of 

 Oilfields. Tbe eastern foothills of the Coast Ranges here show 

 exposures of the Jacalitos and Etchegoin formations. The Tulare is 

 exposed only to a very limited extent at Anticline Ridge. The region 

 examined forms a rectangular strip extending in a north and south 

 direction and has an areal extent of somewhat more than a half 

 township. 



Historical 



The first paper dealing definitely with this region was published 

 by F. M. Anderson. 2 This was followed a few years later by another 

 publication on this region by the same author. 3 According to Anderson, 

 the later Neocene may here be divided into the Coalinga beds and 

 the Etchegoin beds. The latter were subdivided into the Etchegoin 

 sands and San Joaquin clays. The type section of his Etchegoin beds 

 is located in the neighborhood of the old John Etchegoin ranch about 

 fifteen miles northeast of Coalinga. A persistent fossil horizon is 

 mentioned as occuring somewhere near the base. This was later named 

 the Glyeymeris zone by Arnold and Anderson and used as the typical 

 basal Etchegoin in their mapping of the Coalinga field. 



In a bulletin published by Ralph Arnold and Robert Anderson 4 

 the Coalinga beds of F. M. Anderson were divided into three forma- 

 tions, the lowest of which was called the Vaqueros, above this the 

 Santa Margarita, and uppermost the Jacalitos. The Jacalitos for- 

 mation was defined as being above the basal gravels and fossil wood 

 zone overlying the fossiliferous Santa Margarita. At the top the 

 Jacalitos was defined as being below the Glyeymeris zone at the base 



- Anderson, F. M., A Stratigraphic Study in the Mount Diablo Range of Cali- 

 fornia, Proc. Calif. Acad. Sci., 3rd ser. vol. 2, no. 1, 1905. 



s Anderson, F. M., A Further Stratigraphic Study in the Mount Diablo Range 

 of California, Proc. Calif. Acad. Sci., 4th ser., vol. 3, 1908. 

 * U. S. Geol. Surv. Bull. 398, 1910. 



