GEOLOGICAL SURVEY BULLETIN 1027 PLATE 46

Approximate
thickness
(feet)
w
z 110 Sandstone, brown and white, friable; forms massive cliff;
© commonly supports growth of conifers
&
3
a/| 2 22 Shale, gray; interbedded with sandstone
3/6 14 Shale, gray; interbedded with thin beds of lignite
ela 30 Covered; forms slope
3
ele Sandstone, brown and white, friable, fine- to medium-
a\ 4 grained; contains large brown sandstone coneretions as
Ss much as 5 feet in diameter; forms prominent cliff
< Shale, dark-brown, silty; contains thin bed of aragonite;
Plrz cone-in-cone structure at base
S lex 33 Shale, gray to grayish-brown, soft; interbedded with several
S si thin beds of siltstone
ez 31 DSiltstone, brown, hard
eos Shale, dark-gray to black
re 41 Sandstone, soft; interbedded with brown shale. Transi-
tional contact
s 5
2 w
B 3
Oo ES 410 Shale, dark-gray, fissile; contains thin bentonite beds and
3 gray limestone concretions; fossil remains include Bacu-
xt ws, lites and fragments of a large Inoceramus, commonly
ba a with small oysters attached
=
oe Fd
5
o 5
x z
Ww
a
a
5
.
a 153 Shale, dark-gray to black; contains gray limestone conere-
tions
=
5
3
&.
ws
2 Shale, dark-gray to black; contains yellowish limestone
30
z concretions
s Shale, dark-gray; contains reddish-brown ironstone conere-
167 — tions
ee 51 Shale, dark-gray to pea
Limestone, gray, shaly, interbedded with gray shale; forms
Zz 25” prominent orange brown cliff
Be ‘ial dark-gray, caleareous
Esa 27 Shale, dark-gray, calcareous; contains limestone concretions
4 a 187 and bentonite bed
ep) Zz | we 30—Shale, dark bluish-gray; interbedded with thin lenses of
= [wae fine-grained sandstone
2) ges 26 Shale, dark-gray, sandy; cut by mudstone dikes
oO 8< ass 44 Shale, dark bluish-gray; interbedded with thin beds of
2) &g sandstone and bentonite
ld 5 27 Shale and sandstone, dark-gray; weathers light gray; con-
g tS 18. _ tains fish scales
1S) 8 | >z =, Sandstone, gray, fine-grained, soft, thin-bedded
at g2 50 Shale, dark-gray: weathers light gray. interbedded with
as gray to brownish sandstone; contains fish scales
b SS 40 Bentonite and tuff, creamy-gray, massive; forms prominent
uJ 3 ‘white outcrop
wc So Shale, dark-gray, sandy
Covered
() Shale, dark-gray; partly covered; includes 2-foot bed of
NS sandstone at top
jentonite, gray, massive
Covered
80 Shale, dark-gray; mostly covered
16 Sandstone, brown, medium-grained; dark-gray, sandy
shale
7
z
&
s
$
5 205 Covered; talus debris from the overlying sandstone
a
2
o 3
3 2
3° 2 59. Shale, black, fissile
Ww fej
o =
Ee
a 4 237. Shale, black; interbedded with thin beds of gray and brown
oO sandstone; partly coveret
a
Ww
= Sandstone, brown, thin-bedded; has yellow and brown bed-
‘a 17 “ding laminae and fucoidal markings; interbedded with
4d dark-gray fissile shale
Shale, red; mostly covered; weathers to dark-red sandy
185.“ soil
Shale, brown, calcareous; gray, argillaceous limestone
‘Shale, red, mostly covered, weathers to dark-red sandy
soil
é 10/ Sandstone, light-brown: speckled with limonite
= 54 /Shale, red; mostly covered: weathers to dark-red soil
= Sandstone, brown, fine- to medium-grained, contains peb-
= 9 bles of siltstone and limestone
2< Shale, red; mostly covered: weathers to dark-red soil; in-
* cludes a 6-inch bed of brown sandstone
z 0 Sandstone, brown, medium- to coarse-grained; contains
z y pebbles of siltstone and limestone
Ee / Covered
8 350 '27- Sandstone, brown, thin-bedded, fine-grained
x AZ Shale, red: partly covered: weathers to dark-red soil: and
20
thin bed of conglomerate composed of lmestone frag-
ments
‘Covered
Sandstone, gray, medium- to coarse-grained: locally con-
. 122 ““glomeratie, crossbedded; forms prominent ledge that
iS}
ss Peo weathers to large angular blocks
n bossa 32 Erosional unconformity
2) —— 3 Coal
Ola
le 25 83 Covered
YOiD5 oe
n|> eg : ‘nous: j :
rs Siltstone, brown, ferruginous; interbedded with gray and
ajc) 35 green shale, brown limestone, and sandstone
am Shale, varicolored; partly covered; interbedded with gray
Wl oO
a cle limestone
Diaioe { é 50. Sandstone, brown, fine to medium-grained; speckled with
re imonite
a\P Se 10 Sandstone, gray and brown, coarse-grained, probably con-
va no
C ° ez tains some glauconite
4 “ss ‘Erosional unconformity
Zz m © 135 Limestone, gray, dense; in beds from 65 to 10 feet thick,
qt thin red and gray partings
2
S 61 Shale, red; weathers to red soil, mostly covered
_ 5 Sandstone, white to orange, friable
> 56 Covered
wn z
ro) 64 Sandstone, white, orange, and red, medium-grained, bed-
2 | Ee ded; color variable
Fl z
WwW °
oO | e 102 Covered
| z
8
g 18 Sandstone, gray, friable; forms massive cliff
=
133 Covered
[<== 15 Sandstone, brown, medium- to coarse-grained; weathers
to large, rough-surfaced blocks
82 Covered
7 39 Sandstone, red, coarse-grained, locally conglomeratic,
ere hematitic; breaks into coarse angular fragments on
weathering
76 Covered
(op) 131. Shale, black, fissile; partly covered
uw
=) z
=
fo) cy 10 Limestone, black, dense; forms ledge
x
a =
a
ld =
218 Shale, black; weathers to black soil; contains thin beds of
LL aragonite up to 1 or 2 inches thick, brachiopods and
_ other fossils attached ; mostly covered
2
O Zz .
= a 9 Limestone, gray, dense; gray shale partings
oO! 5 3
a 2 86 Covered
ae a oO
Ijin > 90 Shale, light greenish-gray, interbedded with thin layers of
o| n = gray limestone
— o
216 4 Limestone, gray, dense, forms small ledge
op) &
a wo] 2 47 Shale, light-gray, light greenish-gray, and light purplish
< gray
s o| z 14° Limestone, dark-gray, dense, bedded
S =| 5. 38 Shale, gray, partly covered
‘ o| 2
&
G
rE 120 Covered
cE
5
137 Shale, gray, calcareous; interbedded with yellow argilla-
‘ceous limestone: mostly covered
w 125 Sandstone and siltstone, yellow and yellowish-gray, fine-
>~S grained; partly covered; commonly supports growth of
we conifers
23
x2
a 65. Siltstone, red; in part shaly or sandy; mostly covered
Erosional unconformity
Limestone, gray, granular or dense; forms massive cliffs
w i =a and hogbacks along front of mountains; commonly sup-
Zz = ports dense growth of conifers ; thickness not measured
52 Vertical scale
<
==
5 100° 0 100 200 300 400 Feet

‘The columnar section is based on measurements from the following localities: The Eagle sandstone and Telegraph Greek formation were measured 10
secs. 5 and 6, T 18N., R. 16 E.; the Niobrara and Carlile equivalents are taken from a section measured by W. A. Cobban near Mosby; the Greenhorn,
Belle Fourche, and Mowry equivalents were measured by W. A Cobban about 5 miles northeast of Geyser; the Thermopolis equivalent was measured
about 2 miles northwest of Geyser; the Kootenai, Morrison, and Swift formations, on the east side of Skull Butte dome; and the Amsden formation and
the Big Snowy group, along the hogback on both sides of Willow Creek in Tps. 14 and 15 N., R. 11 E.

GENERALIZED COLUMNAR SECTION OF ROCKS
EXPOSED IN STANFORD-HOBSON AREA,
CENTRAL MONTANA

354332 O - 55 (In pocket)