Bl

Chert. Grey, green, and red cherts make up the most characteristic
sedimentary bands, although they comprise only a small part of the
assemblage. They occur in beds ranging from less than 1 inch to about 14
feet thick, and are commonly crumpled or shattered. Many of the beds
have soft, slaty tops, or are separated by thin layers of slaty material
that weathers more rapidly than the chert and gives rise to ribbed outcrops.

Limestone and Dolomite. Massive to bedded, crystalline limestone
occurs as scattered bands, apparently mainly in the upper part of the
exposed section of this group. Some bands are as much as 200 feet thick,
but most of them are relatively thin. In part the rock is light grey, pure
limestone, but much of it contains argillaceous, tuffaceous, or carbonaceous
impurities and is dark grey, green, pink, or black. Bands of finely crystal-
line dark grey dolomite, commonly less than 10 feet thick and weathering
buff to chocolate-brown, were noted 2 miles northwest of the mouth of
Quenada Creek.

Structure

Northwest from Sustut Lake the strata of the Asitka group dip con-
sistently southwest at angles ranging from 30 to 70 degrees and averaging
50 degrees. Southeast from Sustut Lake nearly to the mouth of Carruthers
Creek, both strike and dip vary widely, and drag-folds and abrupt reversals
of dip are common locally. The general trend of the beds is, however,
northwesterly, and east of Mount Carruthers drag-folds and traces of
bedding on cleavage planes suggest that the major folds there plunge
northwesterly at angles of between 15 and 40 degrees. About 24 miles
northwest of the mouth of Quenada Creek these rocks form an anticline
that plunges northwest at about 20 degrees.

The top of the Asitka group is exposed on a spur extending north from
Sustut Peak, but the base was not recognized at any place. The available
data from the Sustut Peak spur do not eliminate the possibility of some
repetition, but, assuming no repetition, about 8,500 feet of mainly volcanic
rocks are exposed there and represent a minimum thickness for the group.

Fossil Collections

Foraminifera and other fossils are numerous, particularly in the cal-
careous strata. The most useful collections are listed below, with ages
assigned to them by the authorities acknowledged.

F11,2 Locality: 1-5 miles northeast of Niven Peak.
Forms identified: Schubertella n.sp. 18
Rugofusulina nsp. 1
Schwagerina nsp. 1
Age: Lower Permian

F2. Locality: 1 mile northeast of Niven Peak.
Lot A¢*
Forms identified: Productus sp. 1
Age: Permian (?)

1 This symbol appears on the accompanying geological map at the locality specified.

? Forms identified and age assigned by C. O. Dunbar, Peabody Museum of Natural History, Yale University,
New Haven, Conn., U.S.A.

’ This number indicates that this new species of Schubertella is the same as that identified in collection F2, Lot B.

‘ Forms identified and age assigned by Alice E. Wilson, Palzeontological Section, Geological Survey of Canada .

15410—2