1917] Nomland: The Etchegoin Pliocene of Middle California 209 



A few miles east of the bed last described, or about five miles south- 

 east of Coalinga, another band outcrops on the west side of the higher 

 hills. This bed resembles very closely in texture and petrographie 

 characters the tuffaceous material on Jacalitos Creek. These charac- 

 teristics, together with faunas of middle Etchegoin age collected above 

 and below each of the two bands, indicate that they probably belong 

 to the same horizon. 



Closing the period of deposition of the marine Etchegoin, or im- 

 mediately before the transition of these beds into the prevailingly 

 terrestrial deposits of the Tulare, volcanoes were again active in this 

 region. This is shown by the large proportion of tuffaceous material 

 mixed with the clays of the Mya japonica zone of the north Coalinga 

 region. The tuffaceous material is of very fine texture and of rhyolitic 

 composition. At one locality about one hundred feet stratigraphically 

 below this horizon another bed of tuff has been found. This material 

 is rather coarse-grained, as if deposited and later broken into frag- 

 ments and redeposited. The tuff in this band is interstratified with 

 a large proportion of quartz sand. 



The tuffaceous beds of the upper and lower Etchegoin, being 

 usually very persistent, should prove of value for correlation purposes 

 if found in other parts of the field. The striking characteristics of 

 the beds make them readily distinguishable even at a considerable 

 distance. It appears rather remarkable that they have not been found 

 in the Kettleman Hills and in the Kreyenhagen Hills, a few miles to 

 the south. 



GYPSUM 



At several horizons of the Pliocene in this district large quantities 

 of gypsum have been found. In no instance, however, except near 

 the base of the Tulare formation, are these beds known to be inter- 

 stratified with the clastic series. At that horizon on the eastern flank 

 of the Kettleman Hills thick gypsiferous beds occur with extremely 

 fossiliferous fresh- water deposits. At several horizons in the Etche- 

 goin large quantities of gypsum are found. Since these deposits of 

 gypsum usually are in a very fragmentary condition, they cannot be 

 assigned definitely to an origin contemporaneous with that of the beds. 

 It seems improbable that large quantities of gypsum occurring exten- 

 sively only at definite horizons could have filtered from other sources 

 into fissures and cavities subsequent to the deposition of the Etchegoin. 



Gypsiferous beds are probably not deposited under normal marine 



