44 PETROLEUM OF PACIFIC OAST OF ALASKA. bo l. 250. 
by the abundance of large cephalopods, especially several species of 
Cadoceras, which, with the Belemnites, predominate over all other 
forms. Dr. Stanton places this fauna near the top of the middle 
Jurassic, it possibly being the equivalent of the Callovian. It is to 
be compared with the Jurassic rocks from Cold Bay described by D . 
W. H. Dall and also in this report, and with those described by Doc 
tor Dall from Tuxedni Harbor (Snug Harbor), Kamishak Bay, and 
other localities on the Alaska Peninsula. 
UPPER JURASSIC ROCKS. 
The Enochkin shales are overlain by a series of volcanic flows of 
andesite and basalt, and by coarse agglomerate, with much inter- 
bedded tuff, arkose, and shale. While the agglomerate seems to be 
confined to the shore of Enochkin Bay, the series as a whole forms the 
high coastal ridge which extends from Enochkin Bay to and beyond 
Chinitna Bay, the total thickness being probably more than 5,000 feet. 
Agglomerate. — The Enochkin shales as exposed in the type section 
are overlain with apparent conformity by a bed of agglomerate hav- 
ing a computed thickness of 200 feet. The pebbles vary in size from 
less than an inch to 6 or 8 inches in diameter, are well rounded, 
and composed principally of granite, though occasional pebbles of 
some other crystalline or of schistose rocks are seen. The cement is 
evidently a volcanic ash of andesitic character. 
The thick beds of coarse agglomerate have been seen by the writer 
only in the section described above, and it is probable that they are 
a local facies of the series of igneous flows which outcrop at the 
mouth of Chinitna Bay and along the shore of Cook Inlet, both north 
and south of that point. If such be the case, then the very fine tuffa- 
ceous agglomerate described in the Oil Bay section (see p. 43) is 
probably the equivalent of the coarser agglomerate exposed a few 
miles southwest ward on Enochkin Bay. 
Naknek formation. — In the section on the east shore of Enochkin 
Bay the bed of agglomerate is overlain by a series of very homoge- 
neous, dark, sandy shales, with a computed thickness of 583 feet. No 
fossils were seen in these shales at their exposure on the shore of 
Enochkin Bay. 
The shales are overlain by an alternating series of andesite flows 
and beds of agglomerate, the thickness exposed on the shore of Enoch- 
kin Bay being computed at 270 feet. Beyond the mouth of Enochkin 
Bay, in the cliffs on the shore of Cook Inlet, higher beds are exposed. 
The entire thickness is not known. 
The Enochkin shale exposed on the shores of Chinitna Bay and in 
the Dry Bay and portions of the Oil Bay regions is overlain con- 
formably by a series of arkose and other sediments interbedded with 
andesitic flows (fig. 3). These with their relation to the underlying 
