[artin.] PETROLEUM FIELDS. 129 
exposed in the region to the northeast of Katalla along the banks of 
he Katalla River and in the range of hills to the east of it. From this 
>oint they extend eastward, occupying the whole of the peninsula 
>etween Bering Lake and Controller Bay and outcropping in all the 
alls south and east of Bering River except (probably) the Okalee 
fountains. Good exposures were seen on the west shore of Bering 
^ake, and it is possible that some of the shales and sandstones of 
Cayak and Wingham islands represent the same formation. No 
stimate could be made of the thickness of the formation because of 
he complicated structure in all the districts where it is exposed. A 
ew fossils which have been obtained indicate that the formation is of 
Cocene age. 
The eastern shore of Bering River and Controller Bay, from a 
>oint slightly below the mouth of Stillwater Creek to the ocean, is a 
at plain of sand and mud, constantly growing by the addition of 
ediment which the streams from the southeastern margin of the 
Jering Glacier carry and deposit along their courses and at their 
louths. Mount Nitchawak, Mount Campbell, Mount Gandil, and 
ther peaks rise like islands from out this plain of sand and mud. 
t seems certain that a very short time ago they were islands in an 
lder extension of Controller Bay which has been filled by the sedi- 
lent of these glacial streams. These deposits are known to have a 
biickness of over 580 feet at one point on the Bering River. This 
laterial floors the valley of Katalla River and of the stream which 
eads near it and flows into Bering Lake to a depth exceeding 240 
set, and it also fills the lower courses of most of the other streams 
r hich enter Controller Bay. 
Another series of deposits contemporaneous with the last, yet dif- 
srent in origin, is made up of the beaches, islands, and bars which 
le waves of the ocean are building along these shores. 
Several igneous masses were seen on the west shore of Bering 
liver, near its mouth. These include several dikes of a light- 
^lored, fine-grained rock (tentatively determined under the micro- 
jope to be a microgranite) and a fine-grained, dark-green igneous 
ock which, upon examination, proves to be a chloritized tuff or 
olcanic ash. 
STRUCTURE. 
The structure of this region appears at first sight to be extremely 
omplex, the strikes and dips being of almost indescribable irregu- 
irity. Careful study has, however, shown that part of the irregular 
utcrops consist of large blocks that have been displaced on the steep 
illside by gravity, while some of the irregularities may be due to a 
linor crumpling in the softer beds. Others may be due to faulting, 
ut the amount of influence of this factor is not known. 
Bull. 259—05 9 
