martin.] PETROLEUM OF PACIFIC COAST OF ALASKA. .'V7 
COOK INIjET PETROLEUM FIELDS. 
GEOGRAPHY. 
The region under discussion occupies the western shore of Cook 
Inlet from the foreland on the north side of the entrance of Chinitna 
Bay, south westward for about 40 miles, to the months of Enochkin a 
and Iliamna bays, and extends inland, with a maximum width of 
about 10 miles, to the crystalline rocks at the eastern front of the 
Chigmit Mountains. Its coast includes the deep indentations of 
Chinitna, Enochkin, and Iliamna bays, and the lesser ones of Oil and 
Dry bays (PL IV). 
The region includes a high mountain range, a range of lower 
hills, and an intervening valley region. The rugged Chigmit Moun- 
tains have an average elevation of about 3,500 feet, and are parallel 
to the general shore of the inlet. The Tilted Hills from the mouth 
of Enochkin Bay northeastward to Snug Harbor run parallel to 
the coast at the distance of a mile, and have a general elevation of 
about 2,200 feet (PI. V). An area of depression occupies the posi- 
tion between these two ranges, and consists of many valleys drained 
by streams flowing into the bays named above, and of irregular, low, 
rounded hills. The divides between the drainage systems are low 
and permit easy portages. The streams are all small, for the most 
part unnamed, and entirely unnavigable. 
The lowlands are covered with dense vegetation and consist of 
about half meadow and half forest. The meadows are deeply 
grassed and are dotted with groves of cottonwood and thickets of 
alder and willow. The forests consist of a fair growth of spruce and 
hemlock, and though trees are not large, they are straight and sound. 
A wagon road has been built from the lower landing point of 
Enochkin Bay to the head of Oil Bay, and there are cleared trails 
from the head of Oil Bay to Dry Bay, to the head of the eastern arm 
of Enochkin Bay, and to a point on the shore of Enochkin Bay 2 
miles above the lower landing. There are also two trails from Dry 
Bay to the shores of Chinitna Bay, and a portage trail from the head 
of Enochkin Bay to the head of Chinitna Bay. (See PL IV.) 
GEOLOGY. 
The rocks of this region consist of a zone of massive crystallines, 
exposed in the Chigmit Mountains; a sedimentary formation of 
Jurassic age in a belt east of them, and a series of overlying agglom- 
erates, shales, and bedded volcanic flows, which are exposed in lli<' 
"This has been variously spelled as Inerskin, Innerskin, Inischen, and Innisken, but 
that here given is said to be the correct spelling of the Russian name. 
