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beneath which the sediments seem to dip. At the north and south ends
of the area the sediments also seem to plunge beneath the volcanic rocks,
though in the north they may be in part cut off by intrusive rocks which
are rather plentiful in this locality. As already stated, the sediments in
the northern part of Bear River district appear to plunge northward under
the volcanic rocks. The sediments in upper American Creek valley seem
to occupy the same stratigraphical position and, therefore, the sediments
of the two areas are correlated on structural grounds. Apparently the
deep valley of American creek has been cut through the volcanics to the
lower sediments.

In Salmon River district sediments occur in two northerly striking
bands. The eastern band extends from Slate mountain northward to mount
Mitre. The rocks are mainly argillite with minor beds of greywacke and
conglomerate. The sediments of this area form a syncline. The beds dip
inward at moderate to gentle angles in its southern part and at steep angles
in its northern part. In the southern and southwestern part and locally
along the eastern side the sediments are separated from the underlying vol-
canic rocks by a bed of fine pebble conglomerate. Locally this conglomerate
appears to grade from the underlying volcanic rocks to the overlying
argillite. In these places the lower beds of the conglomerate contain pebbles
of volcanic rock and its upper part consists of coarse sediments such as grits.
This conglomerate may indicate that a short period of erosion intervened
between the formation of the adjacent volcanic rocks and the deposition
of the sediments. Wherever dips are seen in the adjacent volcanic rocks,
they are, however, conformable to those of the overlying sediments and,
therefore, the erosion interval was probably very brief. As the sediments
overlie the adjacent volcanics they are correlated on structural grounds with
those east of the head of Bear river and east of American creek, which over-
lie the same body of voleanic rocks. Fossils have been found in the lower
part of this sedimentary body and these show that the age is Jurassic.

The westerly band of sediments begins on the east side of Salmon River
glacier near its lower end and extends north and northwest in a broadening
band continuing west and southwest into Alaska and northwest over a large
area west of Summit lake. The sediments are mainly black argillite. The
relationship of this band to the adjacent volcanics in the south is obscure
as the igneous rocks in contact with it are in the main of intrusive type.
Because stratified volcanic rocks to the east at the Big Missouri mine dip
west toward the sediments it appears as if the sediments occupy an over-
lying position. It is probable that the sediments are younger than the
bedded volcanics to the east and have been cut by minor intrusions associ-
ated with these volcanics. West of Salmon glacier the sediments of the
southern part of the body have a uniform, gentle, westerly dip. Farther
north, from mount White-Fraser north for 8 miles, the dip is northwest at
gentle to moderate angles. The thickness of the sediments on mount
White-Fraser exceeds 3,000 feet. Where the sediments are in contact with
crystalline rocks of the volcanic series on the east near Summit lake the
contact is vertical and the sediments there have a vertical dip. No evidence
of the age of these sediments is available from the adjacent part of Alaska
as there the sediments are enclosed in Coast Range intrusives. The pre-
valent westerly dip over most of this sedimentary area suggests strongly