FAUNA OF NAKNEK FORMATION 407 



In Kamishak bay the exposures of the Naknek formation are usually 

 very fossiliferous sandstones, with low dip, and representing only a small 

 part of the whole formation. One such exposure on Rocky bay is shown 

 in plate 69, figure 2. On Douglas river, which empties into Kamishak 

 bay west of Shaw island, there is an interesting local unconformity within 

 the Naknek formation, showing an unevenly eroded surface, which was 

 traced in the cliffs for about a quarter of a mile. The photograph (plate 

 70, figure 1) shows a detail of this exposure. The fact that the same 

 fauna is found both above and below this unconformity is evidence that 

 the erosion interval was geologically brief, and it probably did not affect 

 a wide area. 



The fauna of the Naknek formation is especially characterized by the 

 presence of Aucella belonging to species very closely related if not iden- 

 tical with A. pallasi and A. bronni of the Russian Volga beds. These 

 fossils are at some localities very abundant, completely filling thick 

 beds. At other places they are so rare that they may be easily over- 

 looked, but a careful search will find them in almost every section. As- 

 sociated with the Aucella there are usually two or three species of Belem- 

 nites, frequently a large Lytoceras and a Phylloceras, and occasionally 

 a few gastropods, Trigonia, and other pelecypods. At Oil bay the lower 

 part of the formation yielded two species of Cardioceras related to C. al- 

 iernans and C. cordatus which aid greatly in making more definite corre- 

 lations with both American and European horizons. It is clear that the 

 Naknek formation is of about the same age as the Mariposa beds of Cal- 

 ifornia with Aucella erringtoni and Cardioceras cf. alternans* and it also 

 includes the horizon of the marine Jurassic with Cardioceras cordiforme 

 in the Black hills, where, however, the Aucella element is lacking from 

 the fauna, and probably only the horizon of the basal portion of the 

 Naknek is represented. A similar fauna occurs in Russia in the Volgian 

 beds, and it is widespread in the boreal region, occurring on Spitzbergen, 

 Nova Zembla, and elsewhere. 



In Alaska, Aucella of the same type occur in the Kennicott formation 

 of the Copper River region and at many places on the Alaska peninsula 

 as far west as Herendeen bay. 



LOWER CRETACEOUS 



The presence of the Russian type of Lower Cretaceous on the Alaska 

 peninsula is suggested by the occurrence of Aucella related to A. crassi- 

 collis at port Moller and Herendeen bay, where Jurassic types of Aucella 

 also occur in other beds, but the details of the stratigraphy are unknown. 



*Two names, C. whitneyi Smith and C. dubium Hyatt, have been proposed for probably the same 

 species in this formation. 



LV— Bull. Geol. Soc. Am., Vol. 16, 1904 



