The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1919-12-25

YIN paii tHey UP 10 lle east VI
northeast; and flat beds lie between.
The maximum thickness OF Prichard
rocks exposed In the Pine creek basin
is in the area east of Pine creek be-
tween the Placer creek and Osburn
faults. The beds in this area probably
range in stratigraphic position from a
horizon a few hundred feet below the
middle member Of the Prichard to a
horizon near the top Of the formation.
They dip at variable though In most
places steep angles to the east. Esti-
mates we're made along several ira
verses and it Is believed that not less
than 5000 feet of beds are exposed,
but faults that have no surface ex-
preston may modify these estimates.
The Burke and Revett rocks OF the
Ravalli group flank the Prichard for
nation on the east and south and In
part on the west. To the east, be-
tween the Osbum and Placer creek
faults, the line of separation between
the Prichard and Ravalli rocks Is
probably another fault. for although
there Is no pronounced topographic
expression of fault, the states are
abruptly succeeded by quartzte beds
of discordant dip. Between the Plac-
er creek and Pine creek faults the
states are overlain conformably by the
younger quartZites. Here the beds
strike in general north and dip to the
east.
TO the south the Burke and Revett
rocks overlie the Prichard formation
normally west of a point near the
forks OF Trapper creek. but east of
Trapper creek these formations are
brought into contact by the Pine creek
fault. On the west fork Of Pine creek
excellently exposed states and overly
Ing quantities. dip at moderate angles,
generally to the east or southeast,
though In places the beds are flat.
West of the Sherman prospect, on the
west fork of Pine creek the states are
extend to the summit of Wieserman
peak Purple and green shales and
quartzite of the St Regis formation
conformably overlie the Revett and
quartzite in the southwestern part of
the area in the vicinity of Twin
Crags. The iNewland formation Is
mapped over a small area between
branches of the east fork of Pine creek
and 1t probably occupies a large area
on the divide between the Coeul
d'Alene and st. Joe rivers.
Faults,
Extensive faulting has occurred in
the Pine creek district. particularly in
the area of Prichard rocks and on its
borders The Osburn, Placer creek
and Pine creek faults. Of large dis
placement and pronounced topograph-
ic expression, shown on the geologic
map accompanying professional paper
81, have been traced into the Pine
creek basin All these faults are of
the normal tye, with the downthrow
on the south or southwest.
Osburn Fault.
The Osburn fault, which strikes a
little north of west, traverses the low
lying country in the northern part of
the area. 1t cuts off the belt of Burke
and Revett rocks which lies north of
he Placer creek fault, but for the
most part it traverses the Priohard
The Importance of the Os-
,urn fault has recently been empha-
sized by O. H. Hershey, who has as
,embled evidence indicating that
here was maximum horizontal dis
placement to the west on the south
side of the fault of IL to Is miles in
he Occur d'Alene district probably
,fter the formation of the ore depos-
is.
If this supposition of postmineral
displacement of several
he Wardner and Pine creek districts
occupied positions adjacent |
o the deposits of the Nine Mile and |
canyon creek basins. Studies in the
lllt GREEN give SlloiiS sup
,orting evidence of great horizontal
on the Osburn fault. |
This evidence will not be treated in
etail in this paper, but it may be |
aid briefly that the dome structure
# the Prichard in the Pine creek dis
riot with the structure in the same /
ocks Thanking Ii on the east, is simil-
r to the structure in the same form
tons on the north side of the Osburn |
ault between Osburn and Nine Mile
reek
The ore deposits also in the Prich-
I'd formation in each of these areas |,
ave many features in common.
Placer Creek Fault.
The Placer creek fault is another
,ult of great persistence, which has
cen traced eastward for 35 miles
trough the Occur d'Alene district to
he summit of the Bitter Root noun
lins on the Idaho Montana line. 1t ,
Stends across T. As N, r. 2 E., from
lie south side of Stewart creek in |
action % to Ross fork in section 80 {
nd probably continues westward
ong this stream for some distance.
he displacement along the Placer
Il to, IL - t,,l