Vol. VII] GESTER— GEOLOGY McKITTRICK DISTRICT 221 



The Etchegoin age of these sands in the various fields is 

 now determinable with considerable certainty. In the first 

 part of the paper a typical example of the stratigraphic rela- 

 tionships as determined by surface outcrops was given. The 

 data obtainable from well records and surface exposures of 

 the West Side fields show these conditions to be similar over 

 a wide area. The only exception lies in the fact that there 

 are apparent gradations between fresh water and marine 

 forms in one or two localities, principally in the Kettleman 

 hills. Mr. Cunningham"' states, however, that in general even 

 here there are evidences of a break between the marine and 

 the fresh water formations. A few specimens of Cryptomya 

 calif ornica, which may be a brackish water type, were also 

 obtained from a well in the Midway field just above the pro- 

 ductive oil sands. The balance of evidence, however, is in- 

 dicative of an unconformity at the base of the Tulare, particu- 

 larly from the Lost Hills southward. 



Lost Hills 



The Lost Hills are a group of low hills, midway between 

 Coalinga and Sunset, which rise but slightly above the valley 

 floor. They are the results of a low anticlinal folding, a fold- 

 ing which plunges and flattens to the southeastward. All sur- 

 face indications in the Lost Hills pointed to their being a 

 broad, flat fold. However, as drilling progressed, the pro- 

 ductive sands were found to dip off at angles greater than the 

 surface exposures seemed to indicate. 



Fossils from near the surface showed the upper strata to be 

 of fresh water origin and of Tulare age. Fossils bailed from 

 the Prestage well, Sec. 32, T. 26-21, at a depth of 380' were 

 determined as follows : 



Amnicola tiirbiniformis (Arnold). 

 Carinifcx marshalli (Arnold). 

 Flumincola, species. 

 Splnerium cooperi (Arnold). 

 Viviparus, species. 



Also from a well in Sec. 18, T. 26-21 at a depth of 600' 



were found 



Amnicola turbiniformis (Arnold). 

 Sphserium cooperi (Arnold). 



• B. L. Cunningham, Southern Pacific Co. private report*. 



