1917] Nomland: The Etchegoin Pliocene of Middle California 195 



ern side of the San Joaquin Valley Robert Anderson and R. W. Pack 

 have discussed briefly the Etchegoin and Jacalitos. 



The occurrence of the invertebrate faunas in horizons with the 

 vertebrate faunas in the type Etchegoin section north of Coalinga has 

 been described in a short paper by the writer."' In this publication 

 Arnold and Anderson's formational names Etchegoin and Jacalitos 

 and their faunal zones in the Etchegoin were retained. In a later 

 paper by the writer, 11 embracing a study of the hitherto little known 

 fauna of the Jacalitos formation at the type locality, the fauna of 

 this formation is shown to be very closely related to the overlying 

 Etchegoin. 



THE RELATION OF THE JACALITOS TO THE ETCHEGOIN 



In their report on the geology and oil resources of the Coalinga 

 district Arnold and Anderson 12 state that, "the Jacalitos is likewise 

 conformable to all appearances with the later Miocene (Etchegoin) 

 beds which rest above it and are largely similar in composition, the 

 line between these two formations being drawn somewhat arbitrarily, 

 chiefly on the basis of the fossil contents." It is, however, stated in 

 the same publication 13 that an unconformity between the formations 

 exists, as is shown by the overlap of the Etchegoin on the Cretaceous 

 in the White Creek syncline, though the beds appear conformable in 

 other parts of the district. During the study of the Pliocene of the 

 Coalinga district by the writer the question of the relationship of the 

 Jacalitos to the Etchegoin as defined by Arnold and Anderson has 

 therefore been considered of especial importance. 



The base of the Etchegoin as mapped by Arnold and Anderson 

 north of Coalinga in the type section of the formation was the Gly- 

 cimeris zone. It was found by the writer in attempting to extend the 

 zones of Arnold and Anderson to the north that these tend to dis- 



9 Anderson, Eobert, and Pack, R. W., Geology and oil resources of the west 

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

 Bull. 603, 1915. 



10 Nomland, J. O., The relation of the invertebrate to the vertebrate faunal 

 zones of the Jacalitos and Etchegoin formations of the Coalinga District, Univ. 

 Calif. Publ. Bull. Dept. Geol., vol. 9, no. 6, 1916. 



11 Nomland, J. O., Fauna from the Lower Pliocene at Jacalitos Creek and 

 Waltham Canon, Fresno County, California, Univ. Calif. Publ. Bull. Dept. Geol., 

 vol. 9, no. 14, 1916. 



1 2 Arnold, Ralph, and Anderson, Robert, Preliminary report on the Coalinga 

 Oil District, California, U. S. Geol. Surv. Bull. 357, p. 41, 1908. 



13 Ibid., p. 47. 



