martin.] COOK INLET REGION. 47 
plane. For about 3 miles north from this fault the strata undulate 
somewhat, but have a general dip to the northwest, which finally 
becomes very pronounced and is constant at an angle of from 15° to 
17° for a distance of over a mile, thus forming the general western 
flank of the greater anticline. 
The syncline which adjoins this anticline on the west is a much nar- 
rower and simpler fold. It is characterized by a steeper dip on the 
western than on the eastern flank. It appears to die out toward the 
northeast and was not recognized on Chinitna Bay. West of this 
syncline is an anticline in which the rocks are badly crumpled and 
faulted. The crystalline rocks are exposed on its western side and 
at places within it. The contact of the westernmost outcrops of the 
shales with the crystalline rocks appears to be along the line of a 
great fault. 
The amount of pitch of the axes of these folds is not known. 
The contact of the Enochkin formation with the underlying crys- 
tallines has been seen only on the east side of Enochkin Bay. The 
locality on the south shore of the northeast fork of the bay would seem 
to show that the formation rests unconformable 7 upon the green 
porphyritic rock, though, on the other hand, the locality across the 
bay, on its northern shore, suggests that the green rock may be 
younger and intruded. Another hypothesis may also be considered, 
namely, that the Enochkin formation is unconformable upon the 
green rock and that the western line of outcrop of the former is along 
a zone of faulting which has thrown a block of the green rock into 
the dike-like position seen on the north shore. The crushed zone 
west of this locality favors this hypothesis, as does also the fact that 
on Chinitna Bay, some distance northeast of this point, the contact 
of the Enochkin formation with the green rock has transgressed east- 
ward across the series of folds in the former, so that there is only 
one anticline instead of two, as on Enochkin Bay. This hypoth- 
esis is favored also by the occurrence of abundant fragments of 
brown, sandy, shale or shaly sandstone along the western border of 
the belt occupied by the Enochkin formation. 
OCCURRENCE OF PETROLEUM. 
Surface indications.— The surface indications of petroleum in 
this region consist of seepages or oil springs and the so-called w " gas 
springs." In the first, the petroleum may be seen oozing from the 
cracks in the rock or coming out of the soil. On the east shore of 
Enochkin Bay a good seepage was seen about 1,000 feet below the 
lower cabin, although the spring is covered at high tide. The flow is 
often so strong that the petroleum collects in Large blotches on the 
pool, or even covers its entire surface. At one point it issues from a 
crevice in the shale of the Enochkin formation. 
