Contributions to 

Economic Geology 

1956

GEOLOGICAL SURVEY BULLETIN 1042

This volume was printed as 

separate chapters A-S

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director
CONTENTS

[The letters In parentheses preceding the titles designate separately published chapters]

Page

(A) Geology of the Johnson Creek quadrangle, Caribou County, Idaho, by 

R. A. Gulbrandsen, K. P. McLaughlin, F. S. Honkala, and S. E. 

Clabaugh 1

(B) Airborne and ground reconnaissance of part of the syenite complex

near Wausau, Wis., by R. C. Vickers_______________ 25

(C) Geology of the Virginia City quadrangle, Nevada, By George A.

Thompson. _ _____ . _______ _ 45

(D) Quicksilver deposits near Weiser, Washington County, Idaho, by

Clyde P. Ross ________________ _____ 79

(E) Physical stratigraphy of the Phosphoria formation in northwestern

Wyoming, by Richard P. Sheldon. _ _ _ 105 

(F) Zoning of the Bitter Creek vanadium-uranium deposit near Uravan,

Colo., by Alien V. Heyl_______________________-____________. 187

(G) Gem stones of the United States, by Dorothy M. Schlegel__ ____ 203 

(H) Preliminary report on oil-shale resources of Piceance Creek basin,

northwestern Colorado, by John R. Donnell_____ ____ 255 

(I) A reconnaissance study of the Beach sands of Puerto Rico, by Robert

B. Guillou and JeweU J. Glass_____________________ 273 

(J) Coal resources of Oklahoma, by James V. A. Trumbull___ ___ 307 

(K) Dismal Swamp placer deposit, Elmore County, Idaho, by Frank C.

Armstrong 383 

(L) Monazite in part of the Southern Atlantic Coastal Plain, by Lincoln

Dryden__________________________________ 393 

(M) Optical calcite deposits in Park and Sweet Grass Counties, Mont., by

W. C. Stoll and Frank C. Armstrong_________________ 431 

(N) Geology of part of the Townsend Valley, Broadwater and Jefferson

Counties, Mont., by V. L. Freeman, E. T. Ruppel, and M. R.

Klepper_____________________________ __ 481

(0) Geology and coal resources of the Walsenburg area, Huerfano County,

Colo., by Ross B. Johnson.._______________ _____ 557 

(P) Geology and coal resources of the Tiptop quadrangle, Kentucky, by

Stewart W. Welch..__________________________ 585 

(Q) Pegmatites of the Middletown area, Connecticut, by Frederick

Stugard, Jr___._____________________________ 613 

(R) Geology of the Ord mine, Mazatzal Mountains quicksilver district,

Arizona, by John N. Faick________________________ 685 

(S) Geology and fluorspar deposits, Big Four fault system, Crittenden

County, Ky., by George C. Hardin, Jr., and Robert D. Trace.___ 699

in
Geology of the 

Johnson Creek 

Quadrangle, Caribou 

County, Idaho

GEOLOGICAL SURVEY BULLETIN 1042-A

This report concerns work done partly 

on behalf of the U. S. Atomic Energy 

Commission and is published with the 

permission of the Commission

CONTRIBUTIONS TO ECONOMIC GEOLOGY

GEOLOGY OF THE JOHNSON CREEK QUADRANGLE, 

CARIBOU COUNTY, IDAHO

By R. A. GULBKANDSEN, K. P. MCL.AUGHLIN, F. S. HONKALA, and

S. E. CLABAUGH

ABSTRACT

The Johnson Creek 7^-minute quadrangle in southeastern Idaho has been 

mapped at a scale of 1:24,000. The quadrangle is in the southeastern Idaho 

region in which the Phosphoria formation contains some of the richest and thickest 

phosphate deposits of the western field. Principal efforts have been devoted to a 

detailed definition of structural features.

Most of the area of the quadrangle is occupied by the northwestward-trending 

Aspen Range that is bounded on the west by Bear River valley and on the east by 

Slug Creek valley. The Aspen Range forms a part of the divide between the 

Columbia River drainage basin to the north and Great Basin drainage area to the 

southwest.

The quadrangle contains only sedimentary rocks and these range in age from 

Mississippian to Triassic and from Tertiary to Recent. Formations present are 

the Brazer limestone of Mississippian age, the Wells formation of Pennsylvanian 

and Permian (?) age, the Phosphoria formation of Permian age, and the Dinwoody 

and Thaynes formations of Triassic age. Rocks of Tertiary and Quarternary age 

are present also but have not been designated by formation names.

The Johnson Creek syncline and the Aspen Range anticline are the principal 

structural features of the quadrangle. They trend west of north and are modified 

and partly obscured in places by many minor folds and by faults that have 

broken the area into large and small blocks. Most of the faults strike parallel to 

the trend of the folds, though a few are normal to it. The western front of the 

Aspen Range is the most intensely folded and faulted part, as shown by the 

magnitude of overturned strata and the large apparent displacement of the faults.

Phosphate rock is the only important mineral resource at this time. It occurs 

as bedded rock at different levels in the Phosphoria formation. There are two 

principal zones of economic importance: one, about 20 feet thick, is near the base 

of the formation, the other, about 5 feet thick, is 100 to 150 feet above the lower 

zone. Though the phosphate zones appear to be continuous over the region as a 

whole, their grade and thickness differ from place to place. Phosphate rock was 

being mined from the area in 1955.

INTRODUCTION AND ACKNOWLEDGMENTS

The Johnson Creek 7X-minute quadrangle (fig. 1) was mapped 

as part of an investigation of the phosphate deposits in the Phosphoria 

formation of Permian age. The quadrangle lies in the Peale Mountains of southeastern Idaho where some of the largest and richest

1
CONTRIBUTIONS TO ECONOMIC GEOLOGY

111*45' 111*30' 111'15' lll'OO1

42*45'

42*30'

42*15"

42*00-

JOHNSON DRY

CREEK VALLEY

WRANGLE QUADRANGLE

AREA OF INDEX MAP

Pocotello

i_________

42*43'

42*30-

42*15'

42*005

111*45' 111-30' 111*15'

FIGURE 1. Location of Johnson Creek quadrangle, Caribou County, Idaho.

phosphate deposits Of the western field occur (Swanson, McKelvey,

and Skeldon, 1052). TKe Joknson Creek quadrangle, as the northwest quarter of the Slug Creek 15-minute quadrangle, -was mapped

previously by Mansfield and others (Mansfield, 1927) at a Scale of 

1:62,500 and has been remapped at a scale of 1:24,000 in order to 

obtain detailed geologic data that will aid in the appraisal of the 

phosphate deposits there (pi. 1). The Dry Valley quadrangle, 

recently mapped by Cressman and Gulbrandsen (1955), adjoins the 

eastern border of the Johnson Creek quadrangle.
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 3

Preliminary work in the Johnson Creek quadrangle began in 1948 

when F. C. Armstrong, N. K. Flint, S. Tuttle, and R. Harris examined 

and mapped outcrops of the Phosphoria formation and adjacent strata 

in parts of the area. Mapping on a topographic base was done in 

1949 and 1950 by R. A. Gulbrandsen, K. P. McLaughlin, F. S. 

Honkala, S. E. Clabaugh, K. B. Krauskopf, E. R. Cressman, and 

J. W. Hill under the general supervision of V. E. McKelvey and R. W. 

Swanson. Field verifications were made in 1951 and 1952. Gulbrandsen is chiefly responsible for the text and map compilation.

Besides the comprehensive description of the geology of the Slug 

Creek quadrangle and of the regional geology of southeastern Idaho 

compiled by Mansfield (1927), earlier reports of studies concerning 

this area were made by Gale and Richards (1910), Richards and 

Bridges (1911), and Richards and Mansfield (1911 and 1912).

Helpful cooperation was extended to the field parties by the Anaconda Copper Mining Co., and residents of the area allowed free 

access to their properties. Also, thanks are due R. W. Swanson, 

V. E. McKelvey, and E. R. Cressman for suggestions and advice 

given during the preparation of this report. The cost of the work 

was partly borne by the Division of Raw Materials of the United 

States Atomic Energy Commission.

GEOGRAPHY

The principal physiographic feature of the quadrangle is the northwestward-trending Aspen Range, one of the ranges composing the 

Peale Mountains (Mansfield, 1927, p. 24). The Aspen Range is 

bounded on the east by Slug Creek valley, part of which lies within 

the quadrangle, and on the west by Bear River valley which lies 

entirely outside the quadrangle. Valleys within the range trend 

northwestward and northeastward. Some that lie parallel to the 

range are broad, but nearly all those perpendicular to it are narrow.

The Aspen Range forms a part of the divide between the Columbia 

River drainage basin on the north and the Great Basin drainage 

area on the southwest. Slug Creek, Trail Creek, and Johnson Creek 

are the largest perennial streams in the quadrangle. Other perennial 

streams are in South Sulphur Canyon, Wood Canyon, and in the canyon west of the Jougelard Ranch. The highest point in the quadrangle is Sulphur Peak, 8,302 feet. The maximum relief is 2,600 

feet, but local relief between ridge and valley is generally about 1,000 

feet.

No towns are present in the Johnson Creek quadrangle, but Soda 

Springs, the Caribou County seat, Monsanto, and Conda are situated 

a few miles west of the quadrangle. Soda Springs is served by the 

Union Pacific Railroad and U. S. 30 N. Dirt roads enter the
4 CONTRIBUTIONS TO ECONOMIC GEOLOGY

quadrangle from the west through Trail, Wood, and Sulphur Canyons 

and make all parts except the southern part of the southeast quarter 

reasonably accessible.

STRATIGRAPHY

The Johnson Creek quadrangle contains only sedimentary rocks. 

They total from 7,000 to 9,000 feet in thickness and range hi age from 

Mississippian to Triassic and from Tertiary to Recent. Formations 

present are the Brazer limestone of Mississippian age, the Wells 

formation of Pennsylvanian andPermian(?) age, the Phosphoria formation of Permian age, and the Dinwoody and Thaynes formations of 

Triassic age. Formational names have not been given to the rocks of 

Tertiary and Quaternary age hi this quadrangle, though Mansfield 

(1927) designated the rocks he considered of Tertiary age as the Salt 

Lake formation. Limestone, quartz sandstone, and quartz siltstone 

are the most abundant rock types. Phosphate rock is the only rock 

of economic importance at this tune, though chert of the Rex chert 

member of the Phosphoria formation is used locally as road metal on 

secondary roads.

MISSISSIPPIAN ROCKS 

BRAZER LIMESTONE

The name Brazer was applied by Richardson (1913) to a sequence 

of rock of late Mississippian age, 800 to 1,400 feet thick, in Brazer 

Canyon in the Crawford Mountains of northern Utah. There the 

formation consists of thick-bedded limestone in the upper part and 

thin-bedded limestone and shale in the lower. Locally the formation 

contains beds of calcareous sandstone and nodules and thin beds of 

chert.

The Brazer limestone is incompletely exposed in the Johnson Creek 

quadrangle but hi areas nearby it is thicker and somewhat different 

in composition from its type locality. In Wells Canyon (see section,

p. 5) about 15 miles southeastward from Middle Sulphur Canyon, the

Brazer is more than 1,900 feet thick and consists mostly of thickbedded limestone in the upper part and interbedded limestone and

sandstone hi the lower part. At Little Flat Canyon (see section, pp. 6-7)

about 18 miles northwestward from Middle Sulphur Canyon, the Brazer is about 1,800 feet thick and consists of about 1,000 feet of thickbedded limestone in the upper part and about 800 feet of calcareous

sandstone and some limestone hi the lower part. Locally, a thin black 

shale unit occurs at the top or bottom of the Brazer hi areas outside

tli© Jotnson Oreek quadrangle, Black sLalo occurs at tLe top of tKo

Brazer in Fossil Canyon a few miles south of this quadrangle. Shale

at the top of the Brazer at Little Flat Canyon is varicolored (brown,
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 5

red, and gray) rather than black, presumably the result of weathering. 

Black shale at the base of the Brazer near Laketown, northern Utah,, 

contains some phosphate rock.

Section of the Brazer limestone, north side of Wells Canyon, SW]4SWj4 sec. 11,. 

SE>4 sec. 10, T. 10 S., R. 45 E., Caribou County, Idaho; generalized from.

section measured by T. M. Cheney.

CumuThick- lative

Limestone, gray, fine-grained, thick-bedded; contains chert nodules

and lenses, brachiopods, and pelecypods; sandy and some cross- (feet) (feet) 

bedding at base___._____.______-_-_-_-___________ 9 1966.

Limestone, gray, fine- to coarse-grained, thick-bedded; contains

horn corals, brachiopods, and many fossil fragments.__________ 169 1957

Dolomite and limestone, light-brown to pink, fine-grained, thin- to

thick-bedded._____________________________________________ 6

Limestone, gray, fine- to medium-grained, thick-bedded._________ 40

Covered.___-__-_________-___._____--__-__-__--____-_---_--_ 48

Limestone, light-brown to gray, fine- to coarse-grained; mostly 

thick-bedded; contains horn corals and other fossil fragments; 

sandy in middle part---_-___--__-_--__-____-------------___ 41 1694

Covered.--________-__---_________-_---__---_-___--_-.-____- 19 165&

Limestone, gray, fine-grained, thick-bedded, contains ferruginous

splotches; thin purple to light-red sandstone in middle part_____ 188 1634-

Limestone and sandstone, interbedded gray fine- to coarse-grained 

thick-bedded limestone; and light-brown thick-bedded sandstone; 

some siltstone at top of unit; and oolites in limestone at top of 

unit . ___-_____---_--_________---__-_____-_______-__.___ 326 144&

Sandstone and limestone, interbedded light-brown to red thickbedded sandstone; and gray fine- to coarse-grained thick-bedded 

limestone; oolites in limestone at top of unit; horn corals and other 

fossils and fossil fragments in limestone_____________________ 140 1120

Limestone, gray and brown, fine- to coarse-grained, mostly thickbedded; contains many chert nodules and lenses in middle part, 

and contains horn corals, brachiopods, and fossil fragments _____ 236 980

Covered, limestone and chert float-____________________________ 23 744

Limestone, brown, fine- to medium-grained, thick-bedded; contains

chert nodules and lenses in middle part-__---_---_____________ 56 721

Limestone and sandstone, interbedded gray fine- to mediumgrained thick-bedded limestone; and light-brown thick-bedded 

sandstone; oolites and some chert nodules and lenses in limestone. 203 665

Limestone, gray, fine- to coarse-grained, mostly thick-bedded; 

sandy in part; oolites at top of unit; contains chert nodules and 

horn corals and fossil fragments.____________________________ 264 462

Limestone and sandstone, interbedded gray fine-grained thickbedded limestone; and light-brown thick-bedded sandstone; some 

siltstone in middle part of unit; fossil fragments in limestone in 

middle part of unit___._.__._______________________ 170 198

Covered, limestone float______________________________________ 12 28

Limestone, gray, fine-grained, thick-bedded; contains lenses of

oolitic limestone._______________________._________^________ 16 16

Base of formation not exposed.

370720-56 2
6 CONTRIBUTIONS TO ECONOMIC GEOLOGY

Section of the Brazer limestone measured on the south side of Little Flat Canyon, 

in the S# sec. 17, N}_ sec. 20, T. 7 S., R. 40 E., Bannock County, Idaho, measured by R. A. Gulbrandsen, L. Carswell, and R. Smart.

CumuThick- lative

Shale, varicolored (brown, red, and gray); appears highly weathered; n"^ {^s' 

contains some black sandstone; exposed by excavation on north (feet) (feet) 

side of canyon__________________________.__________________ 10 1830

Covered__________________________________________________ 10 1820

Carbonate rock, medium- and dark-gray on fresh fracture, lightand medium-gray on weathered surface, coarse- and fine-grained, 

thick-bedded, fossiliferous; contains horn corals, brachiopods, 

and gastropods (?) mostly silicifiecL _________________________ 55 1810

Mostly covered, some dark-gray and medium-gray carbonate rock 

with black chert lenses._____________________.______________ 20 1755

Carbonate rock, medium- and dark-gray, fine- and coarse-grained, 

thick-bedded, f ossiliferous; contains horn corals and brachiopods 

mostly silicified; contains sandy carbonate lenses that weather 

brown__ ________________________________________________ 20 1735

Carbonate rock, medium-gray, mostly coarse-grained, thick-bedded, 

f ossiliferous; contains mostly fragments of brachiopods and 

crinoid stem plates, some silicified; contains black chert lenses 

some f ossiliferous. _________________________________________ 85 1715

Carbonate rock, medium-gray and light brownish-gray, finegrained, thick-bedded; fossiliferous in places; contains black and 

light-olive chert nodules and lenses __________________________ 110 1630

Carbonate rock, light brownish-gray, fine-grained, thick-bedded; 

fossiliferous in places; contains some reddish and brownish beds 

colored by iron oxide, and some chert lenses__________________ 65 1520

Covered___-______---_________._____________________________ 135 1455

Carbonate rock; dark-gray and light brownish-gray, fine-grained,

thick-bedded; contains silicified corals____-__-_-_----_-_______ 30 1320

Carbonate rock, dark-gray, coarse-grained, thick-bedded, fossiliferous; contains silicified horn corals and crinoid stem plates_______ 55 1290'

Carbonate rock, dark- and medium-gray, coarse- and fine-grained, 

thick-bedded, fossiliferous; contains silicified horn corals and

colonial pipestem corals individuals of the latter measure as

much as Y?. inch in diameter and 1 foot in length____ ___________ 115 1235

Carbonate rock, dark- and medium-gray, coarse- and fine-grained,

thick-bedded, oolitic.......--__-. _..-. . - 350 1120

Carbonate rock, light yellowish-brown on fresh surface, pale-brown

on weathered surface, fine-grained, thin-bedded, sandy very fine

grained quartz_ ________ . __________________________________ 2 770

Carbonate rock, fine-grained; contains many lenses of black chert-_ 5 768

Carbonate rock, pale-brown and light yellowish-brown and mediumgray, fine-grained, thin- and thick-bedded; contains interbeds of

sandy carbonate rock, some chert lenses in upper part, and a thin

zone of horn corals____________-.____________--__-_-_-------- 113 763

Sandstone, light yellowish-brown arid light olive-brown, fine-grained

thin-bedded, carbonatic; contains bed of very coarse grained carbonate rock and a bed of fine-grained deep-red carbonatic sandstone______ 30 050
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 7

CumuThick- lative 

ness of thickunit ness 

(feet) (feet)

Sandstone, light-gray, medium-grained, thin- and thick-bedded_ _ 90 620' 

Carbonate rock, light-gray, mostly coarse-grained, thin- and thickbedded; contains some interbeds of pale brown fine-grained carbonatic sandstone.____-___-___----__-________-____________ 130 530'

Mostly covered, contains float and some outcrops of brown and 

gray fine-grained thin-bedded carbonatic sandstone..__-_-_____ 400 400'

In the Johnson Creek quadrangle the composition of the upper half 

of the Brazer, the only part represented, compares well with the composition of the Brazer in the southeastern Idaho region. In theMiddle Sulphur Canyon area, where the principal exposures occur,, 

about 1,000 feet of Brazer consists largely of thick-bedded limestone 

but contains a small amount of sandstone in the lowest exposures. 

Here the characteristically thick-bedded limestone is medium to dark, 

gray on fresh surfaces and weathers to lighter shades of gray. Grain 

size ranges from very fine to coarse; the coarse grains are of sand size 

and are composed mostly of crinoid stem plates, oolites, and shell 

fragments. Chert occurs in small amounts as nodules, lenses, and 

thin beds in the limestone. Some of the limestone presents a mottled, 

appearance because of irregularly shaped segregations of finely disseminated iron oxides which are the specks of "siderite" referred to by 

Mansfield (1927, p. 63). In the lowermost exposures the fresh calcareous sandstone is brownish gray and grayish brown, but on. 

weathered surfaces it is dark brown and reddish brown.

Fossils are abundant in the limestone of the formation. Large 

silicified horn corals occur in great number at several horizons, and 

many beds are composed largely of crinoid stem plates and brachiopods..

The top of the Brazer in this quadrangle is taken at the top of the 

uppermost cliff-forming thick-bedded limestone. The break between 

the Brazer and the overlying Wells formation is not distinct, however, 

because the thin black shale unit referred to previously is not present.

PENNSYLVANIAN AND PERMIAN(P) ROCKS 

WELLS FORMATION

The Wells formation was named by Richards and Mansfield (1912, 

p. 689) for its occurrence in Wells Canyon, Idaho, about 10 miles 

southeast of this quadrangle. At Wells Canyon the formation includes 

2,400 feet of thick-bedded sandstone and limestone lying between the 

Brazer limestone of Mississippian age and the Phosphoria formation 

of Permian age. Richards and Mansfield (1912) and Mansfield (1927) 

considered the formation to be largely of Pennsylvanian age. Work 

by other members of the group investigating the western phosphate 

deposits and Baker, Huddle, and Kinney (1949), however, suggest 

that a significant part of the upper half of the Wells may be of Permian
8 CONTRIBUTIONS TO ECONOMIC GEOLOGY

age and correctable with the lower member of the Park City formation 

in Utah. J. S. Williams (1955, oral communication) states that the 

upper member of the Wells contains fusilinids of probable Permian 

age. Considerably more work is necessary, though, before a definite 

Permian age can be assigned to some of the Wells formation.

In this quadrangle the formation is lithologically similar to the type 

section in Wells Canyon and to the section which follows, measured by 

A. F. Holzle in Deer Creek Canyon, about 2 miles northwest of Wells 

Canyon. The three principal lithologic divisions described by Mansfield (1927, p. 72) are recognizable in this quadrangle as well as in the 

general area of the Peale Mountains. They are "a lower sandy and 

cherty limestone facies, a middle sandy facies, and an upper siliceous 

limestone." The thicknesses of Mansfield's units are, respectively, 

750, 1,600, and 50 feet. Though the formation is compositionally 

uniform over a large area, its differences in thickness are noteworthy. 

The Wells Canyon section is 2,400 feet thick, the Deer Creek Canyon 

section is about 1,700 feet thick, and an average thickness in the 

Johnson Creek quadrangle is about 2,000 feet.

Section of the Wells formation, north side of Deer Creek Canyon, in the S}_ sec. 

33, T. 9 S., R. 45 E., Caribou County, Idaho; generalized from section meassured by A. F. Holzle.

Thick- CumuDolomite, brownish-gray to light-gray, fine-grained, thick-bedded; n^f t^ness

contains distinctive white-weathering chert nodules and lenses, (feet) (feet)

and silicified fossil fragments in upper part._________________ 15 1668

Limestone, light-brown to dark-brown, fine- to coarse-grained,

thin- to thick-bedded; white sandstone at top________________ 42 1653

Covered, white and reddish-brown sandstone float.______________ 130 1611

Sandstone, reddish-brown, white and gray, fine-grained, thickbedded; limestone bed in lower part________________________ 79 1481

Covered.._________________________-____-_____ _ _- 30 1402

Sandstone, yellowish-white, fine-grained, thick-bedded.___________ 27 1372

Covered, yellowish-white sandstone float____-_____---_____-__-- 40 1345

Sandstone and limestone, interbedded buff, fine-grained, thickbedded sandstone; and reddish-gray, fine-grained, limestone.___ 45 1305

Covered, yellowish-brown and light-gray sandstone float. ____ 65 1260'

Sandstone, yellowish-white and yellowish-brown, fine-grained, . 

thick-bedded...___________________________________________ 36 1195

Covered, light-brown-weathering sandstone float________________ 55 1159

Sandstone, yellowish-brown, fine-grained, thick-bedded____...--- 18 1104

Covered, gray and tarowr, sanastono float- ______________________ HO 1086

Sandstone, light-reddish to yellowish-gray, fine-grained, thickbedded... " - 35 976

Covered, sandstone float__-___-_ ___-_ __-_---- ----_- 160 941

Sandstone, reddish-gray, fine-grained, thick-bedded._____________ 15 781

Covered, sandstone float. (Approximately the contact between the upper and lower memoers or tnc formation,) __.. . ss 76&

Limestone, light-brown and brownish-gray, fine-grained,, thickbedded, cherty and sandy in part, fossiliferous in middle part; 

contains chert nodules and interbeds of chert in middle part.___ 121 681
GEOLOGY, JOHNSON CREEK QUADRANGL^, CARIBOU CO., IDAHO 9

TAicfc- Cumuness of lative

unit thickness

(feet) (feet)

Covered, brown sandstone float------------------------------- 12 560

Limestone, gray, fine- to coarse-grained, thick-bedded, sandy; 

contains a few sandstone interbeds, and chert nodules in middle 

part of unit__--_-_-----____---_._------------------------- 91 548

Covered, gray sandstone float._____-__---_-___--_---___-_-____ 30 457

Limestone, light-gray to brownish-gray, fine-grained, thick-bedded,

sandy; contains chert nodules in lower part of unit____-____._ 34 .427

Covered, gray sandy limestone float-____-_-__-_---__-___-----_- 300 393

Limestone, gray and light-brown, fine- to coarse-grained, thickbedded, sandy in upper part; contains few chert nodules in middle 

part of unit_-----------_------------------------------__ 28 93

Covered, approximate contact with Brazer limestone...___--_____ 65 65

.Next lower outcrop is part of Brazer limestone.

The formation has been divided into two members for mapping 

purposes. The contact between them is taken as the zone of 

gradation from interbedded sandstone and limestone below (Mansfield's sandy and cherty limestone facies) to a dominantly sandstone 

sequence above (Mansfield's middle sandy and upper siliceous limestone facies).

The lower member, which is about 800 to 900 feet thick, contains 

gray and brownish-gray interbedded limestone and sandstone that 

occur as thick-bedded units, generally several feet thick. Many of 

the limestone beds contain abundant fossil fragments and oolites. 

The sandstone is commonly fine to medium grained and calcareous.

The upper member, about 1,100 to 1,300 feet thick, consists mostly 

of sandstone, though some limestone is also present. The sandstone 

is gray on fresh surfaces but weathers to shades of brown and reddish 

brown. Some of the sandstone is cemented with silica, some is distinctly crossbedded, and all is typically thick bedded. A thin unit 

of gr&y calcareous porous friable sandstone occurs about 200 or 300 

feet from the top of the member. In outcrop areas this rock contains 

many cavities, both large and small. Another thin unit composed 

of red calcareous sandstone, rarely exposed, overlies the porous sandstone. The porous sandstone and red sandstone are correlative in 

stratigraphic position with "pink" sandstone and anhydrite in the 

upper part of the Wells formation in Bear Lake County, Idaho, 

according to the core log reported by Zeni (1953) from the Sheep 

Creek test well. The contact of the upper member with the overlying Phosphoria formation is sharp and is taken at the top of about 

30 feet of thick-bedded gray dolomite that contains nodules, lenses, 

and thin beds of black and light bluish-gray chert. Some of the dolomite beds contain abundant silicified brachiopods (Squamularia?), 

and .others contain silicified rough-surfaced white rods that are considered to be of organic origin. The lithology and fossils of these
10 CONTRIBUTIONS TO ECONOMIC GEOLOGY

beds make an excellent marker, and they have great value in defining 

the proximity of the Phosphoria formation.

Exposures of the Wells formation make up large parts of the areas 

along the western, southern, and eastern margins of the quadrangle. 

The formation's general outcrop pattern outlines a northwardplunging syncline, though the eastern limb is partly obscured by 

faulting. In the south-central part of the quadrangle at the head of 

Johnson Creek part of the upper member of the formation is exposed 

in a small transverse anticline.

PERMIAN BOCKS 

PHOSPHORIA FORMATION

The Phosphoria formation was named by Richards and Mansfield 

(1912, p. 684) for its occurrence in Phosphoria Gulch in the southeast 

corner of the Slug Creek quadrangle, Idaho. The formation is of 

Permian age, though what part of the Permian is represented has not 

yet been satisfactorily determined. The phosphatic shale member 

Is thought by some paleontologists to be of Guadalupe age, and 

possibly Leonard as well (Miller and Cline, 1934; Newell, 1948; and 

Thompson, Wheeler, and Hazzard, 1948, p. 8). Licharew (in 

Williams, 1938, p. 772) considers the Phosphoria to be probably of 

Artinskian age.

In its type section the formation is about 415 feet thick and is

 divided into two members; a lower member composed dominantly 

of phosphatic shale, and an upper member, named the Rex chert 

member, composed of chert and limestone. The formation in this 

quadrangle as described by McKelvey, Armstrong, Gulbrandsen, and

 Campbell (1953) is similar in character and average thickness to

that of the type section and is likewise divided into two distinct 

members, the phosphatic shale member and the Rex chert member

(pi. 2).

The thickness of the formation in the Johnson Creek quadrangle 

ranges from about 150 or 200 feet to a maximum of around 500 feet. 

In general, the formation is thicker along its outcrop at the western 

part of the quadrangle than in the eastern or southern parts; this is 

especially true for the phosphatic shale member. The thickness of 

the Rex chert member is not well defined because the upper contact

is generally covered.

The phosphatic shale member is generally from 100 to 200 feet 

thick and consists of mudstone, phosphate rock, and carbonate rock. 

Where fresh, the mudstone and phosphate rock are dark shades 

of gray and the carbonate rock is a lighter gray. Weathered rock is 

brownish gray, brown, and gray. The beds are typically tMn 1)6(1(16(1 

and generally less than a foot and frequently less than an inch in
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 11

thickness. The carbonate rocks tend to be thicker bedded than the 

others. The phosphate rock is characteristically pellety or oolitic, 

and the abundance of pellets and oolites provides a good estimate 

of the amount of phosphate in the rock. Most of the phosphate 

rock occurs in two zones, one near the base and one near the top 

of the member. The phosphate content of these zones is shown by 

the analyses on page 19. Parts of the phosphatic shale member are 

rarely exposed in natural outcrop, and the whole member has been 

exposed only in bulldozer trenches.

The Rex chert member consists of chert and limestone, chert making 

up the greater part of the unit. The chert is black, medium gray, 

and pale red, and massive in the lower half and shaly above. The 

shaly impure chert is also called siliceous mudstone. Limestone 

occurs in two zones: in the lower part as dense dark-gray limestone 

that weathers gray, and at the top of the massive chert as a coarse 

gray limestone that contains abundant fossil fragments mostly 

crinoid stem plates. The upper limestone is laterally discontinuous. 

It occurs in this quadrangle only in the Wood Canyon area as a large 

lens several square miles hi area. In regions outside the quadrangle, 

however, there are similar occurrences of the limestone at this horizon. 

The Rex chert member is generally from 200 to 300 feet thick.

The major outcrop areas of the Phosphoria are in two bands, one 

in the western part of the quadrangle and one in the eastern part. 

The formation is exposed also around part of the southern tip of the 

Trail Creek syncline and in the transverse anticline at the head of 

Johnson Creek. Its other occurrences are hi many small fault 

blocks. Usually the massive chert of the Rex chert member is well 

exposed, in contrast to the less competent shaly chert and the rocks 

of the phosphatic shale member.

TBIASSIC BOCKS 

DINWOODY FORMATION

The Dinwoody formation of Early Triassic age (Newell and Kummel, 1941) has its type locality at Dinwoody Canyon in the Wind 

River Mountains of western Wyoming. The name Dinwoody is 

applied in this quadrangle, following Kummel (1953 and 1954), to 

the rock strata lying above the Phosphoria formation and below the 

Meekoceras-beaxuig limestone at the base of the Thaynes formation, 

the same strata referred to by Mansfield (1927, p. 86) as the Woodside shale. Kummel (1953 and 1954) redefined the Woodside to 

include only the red facies of these Triassic strata. Since red beds 

are not present in this quadrangle, the whole interval is mapped as 

Dinwoody.
12 CONTRIBUTIONS TO ECONOMIC GEOLOGY

Olive-gray and dusky-yellow calcareous siltstone and gray limestone are characteristic of the Dinwoody rock types throughout a 

large area. The rock strata are shaly in the lower half and thick 

bedded (commonly from 1 to 2 feet thick) in the upper half. The 

total thickness of the formation averages about 2,000 feet, but there 

are large local .differences. Generally the formation seems to be 

thicker in the northern half of the mapped area and markedly thinner 

in the southern part by as much as several hundred feet. A complete 

section of the Dinwoody formation was measured by Kummel (1954) 

on Dry Ridge, a few miles east of this quadrangle.

Two members are mapped. The lower member, which is about 

1,000 to 1,400 feet thick, is composed largely of dusky-yellow and 

light olive-gray calcareous shale. Thin ribs of fossiliferous limestone 

that weather to a distinctive brownish gray or dark purple are characteristic of the lower part of the member. In the upper part of the 

member irregularly bedded and thin-bedded calcareous siltstones are 

interbedded with even- and thick-bedded calcareous siltstone. The 

latter siltstone weathers typically to brownish gray or shiny black.

A zone of transition between the shale and siltstone of the lower 

member and siltstone and limestone of the upper member is taken as 

the contact between the two members of the Dinwoody. This zone 

is characterized by what is interpreted to be slump structures 

bedded rock fragments whose bedding is bent and twisted and is 

discordant to the bedding of the containing rock mass. Also, on the 

rock of this zone, differential weathering has produced marked surface 

irregularities that reflect a small-scale alternation of siltstone and 

limestone layers. The contact between the Phosphoria and this 

lower member is rarely exposed. However, the topographic expression that is the result of a change from the resistant Unit that represents the upper part of the Rex chert member to the weak Unit that 

represents the lower part Of the Dinwoody, along with marked soil 

and float changes, serves to locate it approximately.

The upper member, 800 to 1,200 feet thick, is characterized by

thick-bedded limestone that Weathers light gray, and by interbeds of

calcareous siltstone and calcareous skaie. Many of the limestone 

beds contain an abundance of poorly preserved shells of pelecypods 

and brachiopods. The contact with the Ttaynes formation is taken 

at the base of the Meekocems-l>z&i\\\g limestone. 

Outcrops of the Dinwoody occur mo^i? in tiio central and northern

parts of tte mapped area where its distribution is controlled by the 

attitude of the Trail Creek syndine. Other exposures occur in the 

crest of a small anticline between Trail and Wood Canyons, in fault 

blocks in the-south west corner of the mapped area, and in the northeast part of the quadrangle.
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 13 

THAYNES FORMATION

The Thaynes formation of Early Triassic age has been redefined 

recently by Kummel (1954, p. 173). In the region of the Peale Mountains, Kummel divides the formation into seven members that are, 

from bottom to top: lower limestone, lower black limestone, tan 

silty limestone, upper black limestone, sandstone and limestone, 

Portneuf limestone, and Timothy limestone. Formerly Mansfield 

(1916 and 1927) had included three formations Koss Fork limestone, 

Fort Hall formation, and Portneuf limestone in a Thaynes group. 

Kummel (1954), on the basis of his regional study, reduces the Thaynes 

group to formational rank and retains Mansfield's Portneuf limestone 

only as a member of the formation. In addition, Kummel includes 

the Timothy sandstone as a member of the Thaynes, whereas the 

Timothy had formerly been a formation.

KummeFs (1954) Sheep Creek section of the Thaynes, which is 

about 8 miles northeast of the Johnson Creek quadrangle, is about 

3,550 feet thick. In the Johnson Creek quadrangle only about the 

lower two-thirds of the formation is present. The topmost beds are 

probably equivalent to the lower part of Kummel's Portneuf member, 

but few and poor exposures make the correlation uncertain. Four 

units of the Thaynes are mapped in this quadrangle (pi. 1). They 

were chosen as the units most suitable for mapping in the quadrangle 

and correspond only in part with Kuinmel's members.

The lowest member is composed of calcareous shale and limestone, 

estimated to be 500 to 800 feet thick. The base is marked by the 

distinctive Mee/coceras-bearing gray limestone containing interbeds 

of calcareous siltstone. The abundance of fossils in a few feet of 

strata serves as an excellent marker throughout the whole of southeastern Idaho. Overlying beds are composed of fissile and thin-bedded 

medium-gray calcareous shales that weather gray and brown. Some 

black brittle thin-bedded limestone that weathers to a characteristic 

medium bluish gray is present in the central part of the member.

The second member is composed dominantly of thin-bedded olivegray calcareous siltstone that weathers characteristically into large 

smooth thin dusky-yellow plates. The plates are thick and rough 

surfaced in the upper part of the sequence. Dark-gray fissile shale 

occurs at the top. The overall thickness is estimated to be 600 to 800 

feet.

The third member, which is about 500 to 900 feet thick, is typically 

thin bedded and irregularly bedded. It is composed largely of calcareous siltstone or very fine grained sandstone that contains nodules 

and thin beds of gray limestone. The limestone nodules give a 

large-scale mottled appearance to the rock.

The fourth member is very poorly exposed. It contains distinctive
14 CONTRIBUTIONS TO ECONOMIC GEOLOGY

thick-bedded gray limestone that is fossiliferous in part, and finegrained sandstone that weathers brown. Along the axis of the Trail 

Creek syncline the unit has a maximum thickness of about 500 feet. 

The Thaynes formation is confined to the central and north-central 

part of the mapped area. It occurs in the trough of the Trail Creek 

syncline and represents the youngest of all the beds making up the

syncline.

TERTIARY AND QUATERNARY ROCKS

Tertiary and Quaternary rocks are not differentiated, except 

Quaternary alluvium, though rocks of both ages are believed to occur 

in the quadrangle. It was found that their limited distribution, 

poorness of exposure, and lack of fossils made attempts at differentiation too tenuous to be useful. However, Mansfield (1927) did map 

rocks in this quadrangle that he considered to be of Tertiary age as 

the Salt Lake formation.

The unit mapped as Tertiary and Quaternary is composed of gravel, 

conglomerate, and travertine, but gravel is most abundant at least as 

observed at the surface. The gravel included here is of local derivation, 

but it occurs in physiographic positions in which it could not have been 

deposited by processes prevailing in Recent time. Travertine occurs 

along fault zones and is the cementing material for some of the 

conglomerate.

Patches of Tertiary and Quaternary sediments are found mostly 

along the higher margins of Johnson Creek valley and the valley just 

east of Trail Creek. Other small patches occur in the northwest 

corner of the quadrangle near the Jougelard Ranch, in the extreme 

southwest corner, in the east-central margin area, and along the west 

side of Dry Fork Canyon in the southeast part of the quadrangle.

QUATERNARY ROCKS

Quaternary alluvium makes up the valley floors. Generally it is 

composed of fine-grained sediments, but along the edges of the valleys 

and in their narrower parts the sediments are coarser, in places gravel.

STRUCTURAL

The Structure Of the quadrangle is complex. It consists of two

major north-nortliwestward-trending folds that include many minor

folds. The folds, in addition, are modified and obscured by faults 

which have broken the area into large and small blocks. Most of the 

faults strike parallel to the trend of the folds, though a few are transverse to them.

The Trail Creek syncline and the Aspen Range anticline (Mansfield, 1927) are the largest folds in the quadrangle and are the basic 

structural elements of the area. The Trail Creek syncline is the
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 15

better denned of the two, though it is partly obscured by faulting 

and much minor folding. The Aspen Range anticline is complexly 

faulted; minor folding is present but is less common than in the 

Trail Creek syncline.

The Trail Creek syncline makes up the central part of the quadrangle, extends the full length of the area, and plunges gently to the 

north. The west limb is generally better defined and dips more 

steeply than the east limb, particularly in the southern half of the 

quadrangle. The southern end of the syncline is not well defined 

because of the occurrence of many faults and the small transverse 

anticline at the head of Johnson Creek. The rocks in the Trail Creek 

syncline have been crumpled on a small scale throughout a large 

area. Most of this folding is of too small a scale to be indicated on 

the map but is reflected there by some of the seemingly eiratic dips 

and strikes.

The Aspen Range anticline adjoins the Trail Creek syncline on the 

east. Its anticlinal form is not clearly defined, for it is bounded on 

the west by a large normal fault and is sliced up by other transverse 

and longitudinal faults; parts of the area that are not disturbed by 

faults, however, show the crest of the anticline and its gently dipping 

limbs. The large ridge between Trail and Slug Creeks is thought to 

be the northern continuation of the anticline, though that continuity 

is not clearly shown because of the great amount of faulting.

Folds of lesser magnitude than those just described are common 

and are similar in character. Nearly all trend north-northwestward, 

parallel to the larger folds, though at the head of Johnson Creek two 

small transverse anticlines plunge northeastward. Overturned folds 

are not common, and those that have been found are mostly near the 

western front of the Aspen Range Avhere much large-scale faulting 

has occurred.

 The coincidence of the range front and the position of overturned 

strata and complex faults is striking. This relation is well illustrated 

by the overturned moderately dipping Phosphoria formation and 

adjacent strata on the south side of South Sulphur' Canyon. Other 

occurrences of this coincidence are northward from there. Overturned strata along the front of the Aspen Range are not restricted to 

this quadrangle; the feature is found also on the north side of Swan 

Lake Gulch about 2 miles south of this quadrangle. The same 

phenomenon has been noted by Williams (1948) along the western 

front of the Bear River Range near Logan, Utah. Williams attributes 

the overturning there to drag from a large thrust fault that cut the 

rock strata at an angle greater than the slope-angle'of tkfi-range front. 

In this quadrangle the complex faulting associated with the over-
16 CONTRIBUTIONS TO ECONOMIC GEOLOGY

turning makes an explanation more difficult, and as yet the mechanism 

and sequence of events that are involved are not known.

Normal faults are the largest and most abundant of the many 

faults in the quadrangle. Though two large tear faults probably 

associated with the normal faults occur in the northern half of the 

quadrangle, transverse and reverse or thrust faults are of minor 

importance. The faults are not well defined in many places because 

of poor exposures, but generally they dip westward at medium to 

high angles. Most of the normal faults that dip eastward are on the 

east limb of the Trail Creek syncline.

Faults along .the western border of the quadrangle are especially 

complex. A large normal fault can be traced southward from Shield 

Canyon to the area between North and South Sulphur Canyons where 

its identity is lost in a complex of faults. This fault was mapped by 

Mansfield (1927) as two faults, both as branches of the Bannock 

overthrust, but his interpretation is not supported here. The position 

and attitude of the Phosphoria and Wells formations on the west side 

of the fault are more simply explained as thrown down rather than 

thrust up. In the normal fault interpretation the rock mass on the 

west side of the fault was derived from the west limb of the Trail 

Creek syncline; in Mansfield's interpretation the thrust block came 

out of Bear River valley. At both ends of the fault, as traced in this 

quadrangle, are large outcrops of the Brazer limestone that are nearly 

bounded by faults, the largest of which represents a minimum stratigraphic displacement of more than 3,000 feet. The masses of Brazer 

appear to have been points of resistance that deflected the faulting 

to all sides.

Two other complexly faulted areas occur in the eastern half of the

quadrangle, the area of Burchertt Canyon and the area just north 

of the junction of the Mill Fork and Wood Canyon roads. These 

areas show an intricate pattern of faults, mostly of small displacement

and length, such as might result from a general but rather small-scale 

shattering of the strata.

Two major tear faults are present in the northern half of the mapped 

area. They strike nearly eastward and are the only large faults

that cut across and displace the northward-trending folds. The

block on the north side of each fault shows an apparent westward

horizontal displacement of 1,000 to 2,000 feet from the block on the

south side. Mansfield (1927) states that the Bannock overthnist;

underlies the whole of the Johnson Creek quadrangle, and therefore

no direct observations relating to the question of the existence of 

the Bannock could have been or can be made here. Mansfield did 

map some thrusts along the western margin of this quadrangle that he 

considered to be branches of the Bannock overthrust, but it was
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 17

found in the course of this mapping that the thrusts do not exist or 

are better interpreted as normal faults. Another instance of this 

relates to the thrust shown by Mansfield as extending southward 

from the northwest corner of the quadrangle to the area between 

Trail and Wood Canyons. There the existence of the thrust was 

based on the supposed absence of the Meekoceras zone at the base 

of the Thaynes formation; during the course of the present mapping, 

however, the Meekoceras zone was found along the entire line of 

outcrop.

The relation of faulting to folding in the quadrangle is complex; 

yet in general the major faulting and folding appear to have occurred 

in different periods. The major folds, the Trail Creek syncline and 

Aspen Range anticline, were formed first. Minor faulting was 

associated with the folding, such as the breaking and thinning of 

strata at the southern tip of the Trail Creek syncline. The major 

faulting occurred after the folding, as indicated by displaced and 

broken folds. During this period the large normal faults were formed. 

They generally trend parallel to the folds, and most commonly1 

the blocks on the west side of the faults were dropped.

MINERAL, DEPOSITS

The phosphate deposits of this quadrangle are among the thickest 

and richest of the entire western phosphate field (Swanson, McKelvey, 

and Sheldon, 1953), but the largest part of the deposits is deeply 

buried. The phosphate rock occurs as beds at different horizons 

in the Phosphoria formation and is composed of carbonate-fliiorapatite 

and varying proportions of quartz, dolomite, calcite, and carbonaceous material. The carbonate-fluorapatite occurs most commonly 

as pellets or oolites of fine to coarse sand size. The phosphate and 

associated rocks of the phosphatic shale member contain important 

concentrations of many minor elements; but, except for vanadium, 

the economic utilization of the minor elements awaits the development 

of efficient processes of concentration and extraction.

As part of a regional program, the U. S. Geological Survey trenched 

and sampled the phosphatic shale member of the Phosphoria formation in Trail Canyon, trench 1206, in the NWX sec. 30, T. 8 S., R. 43 

E., and on the outcrop just north of the point where Johnson Creek 

enters Slug Creek valley, trench 1209, in the SE% sec. 23, T. 8 S., 

R. 43 E. Brief rock descriptions and chemical analyses for PgOs and 

the acid insoluble of all samples; A1203, FejjOa, F, and loss on ignition 

for some samples; and semiquantitative spectrographic analyses for 

a large number of elements for some samples have already been published (McKelvey, Armstrong, Gulbrandsen, and Campbell, 1953).

In addition to the surface trenching, three diamond-drill holes
18 CONTRIBUTIONS TO ECONOMIC GEOLOGY

were drilled for the Geological Survey by the U. S. Bureau of Mines. 

They are: diamond-drill hole 1274 on the south slope of Middle 

Sulphur Canyon, sec. 8, T. 9 S., B. 43 E.; diamond-drill hole 1278 

on the north slope of Middle Sulphur Canyon, sec. 8, T. 9 S., K. 43 

E.; and diamond-drill hole 1276 ori the valley bottom of the south 

fork of Johnson Creek, sec. 9, T. 9 S., R. 43 E. The sections obtained 

from this drilling program were incomplete, but descriptions and 

chemical analyses for P205 and the acid insoluble of the core samples 

have been published (McKelvey, Davidson, O'Malley, and Smith, 

1953). The diamond core drilling was part of an experimental program that is described by Long (1949).

Studies of the phosphatic shale member throughout the southeastern Idaho region (Swanson, MeKelvey, and Sheldon, 1953) have 

revealed that the lower and upper phosphate zones are exceptionally 

continuous as a whole; but local differences are marked and are 

critical from the economic point of view, as shown in the table, which 

summarizes the P20S content of the beds exposed in the Trail Canyon 

and the Johnson Creek trenches. The table indicates the problems 

of areal differences in grade of phosphate rock and faulting that must 

be considered in the appraisal of a deposit for development.

At Trail Canyon the lower phosphate zone, near the base of th& 

member, is 6.6 feet thick and averages 32.8 percent P2O5. No such 

zone is found in the Johnson CreeK section. Overlying this rich 

zone at Trail Canyon is the furnace-grade shale zone, 14.8 feet of 

phosphate rock that averages 25.1 percent PaOs; again, no comparable 

zone is found at Johnson Creek. Other parts of the phosphatic shale 

member at the two localities are comparable, and, moreover, the 

lower phosphate zone and the furnace-grade shale zone have been 

identified at other localities to the east. The absence of these zones 

in the Johnson Creek section, therefore, is believed to be due to faults

that occurred at low angles to the bedding planes. Faults of this 

type are difficult to recognize io small exposures and may account 

for other occurrences of the phosphatic shale member that are 

anomalously thin.

At Trail Canyon the upper phosphate zone, which underlies the

top of the phosphatic shale member, is 5,1 feet thick and averages

29.4 percent P2O6. The same zone at Johnson Creek is 5.2 feet thick 

and averages 34.2 percent PgOs. This relatively small difference in 

gTflidC iS Critical b60aUSe the rock is acid grade at Johnson Creek and 

furnace grade at Trail Canyon. Differences in grade of this kind,

but possibly not the magnitude of the above example, are likely to

D6 QUO tO fliffOrOnOCQ IB IT?fr*^OTlng of *^*> rock. Generally the rock

that has undergone the most weathering will contain the most phosphate, because carbonaceous material and carbonate are removed
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 19

Summary of the phosphate content of the phosphatic shale member

Zones

Undifferentiated. . . ......

Undiflerentlated. ____ . __

Trail Canyon section

Pa05 

content 

(percent)

4.3 

29.4

8.3

25.1 

32.8 

10.2

Thickness 

(feet)

13.2 

6.1

165.7

. 14.8 

6.6 

5.6

Cumulative 

thickness ' 

(feet)

13.2 

18.3

184.0

198.8 

205.4 

211.0

Johnson Creek section

Pj05 

content 

(percent)

5.5 

34.2 

10.8 

25.2 

8.9

Thickness 

(feet)

14.2 

6.2 

1.6 

4.3 

119.8

Cumulative 

thickness > 

(feet)

14.2 

19.4 

21.0 

26.3 

145.1

i Cumulative thickness measured from top of phosphatic shale member.

from the rock more rapidly by solution and oxidation than is phosphate. Differences in grade with depth is likewise a function of 

weathering. Generally, but depending on specific conditions, the 

grade of phosphate rock will decrease with depth. The amount of 

decrease probably is small in most cases, but it may be important.

The Anaconda Copper Mining Co. is the only company now 

actively engaged in mining phosphate rock in this quadrangle. 

Most of its work has been done in the development of the Conda mine, 

which is 2 miles west of the quadrangle but whose workings extend 

to the outcrop of the Phosphoria in the northwest corner of the 

quadrangle. A portal is located in the W% sec. 13, T. 8 S., R. 42 E. 

The Conda mine has been in operation since the early 1920's and is 

the only underground phosphate mine in southeastern Idaho which 

has had any sustained period of production. Most of its production 

has been from the lower part of the phosphatic shale member of the 

formation. In 1952 Anaconda began exploratory strip-mining 

operations in the southwestern part of this quadrangle on a high spur, 

in the EX sec. 17, T. 9 S., R. 43 E., that is capped by nearly flat lying 

Phosphoria formation strata.

Though exploration for rich deposits of phosphate in the Phosphoria 

formation has been under way for many years, that activity has 

recently been accelerated by the increasing demand for phosphate 

fertilizer and elemental phosphorus. Particular attention has been 

directed toward areas that possibly could be exploited by strip mining. 

Besides the exploratory strip mining begun by the Anaconda company, several areas, including the upper part of the south fork of 

Johnson Creek, along Burchertt Canyon, and north of the junction of 

Dry Fork and Petterson Canyons, have been extensively explored by 

bulldozer trenching. Though many trenches were dug, they were 

not deep enough for a proper evaluation of the deposits. Thus the 

potential of those areas is still unknown.
20 CONTRIBUTIONS TO ECONOMIC GEOLOGY

The part of the Trail Creek syncline south of the Johnson Creek 

road in which the phosphatic shale member of the Phosphoria formation is covered only by the Rex chert member or the Rex chert and the 

lower part of the Dinwoody formation is possibly of value for shallow 

underground mining. The marked thinning or absence of the phosphatic shale member in that area, however, makes any estimate of its 

potential uncertain.

The long line of outcrop in the northeast quarter of the quadrangle 

has not been prospected, probably because it is notably thinner than 

either the Trail Canyon or Johnson Creek sections; however, it is not 

known whether the phosphate zones of the section are present there. 

The line of outcrop along the west limb of the Trail Creek syncline 

from the summit of Middle Sulphur Canyon to the northwest corner 

of the quadrangle seems to be comparatively free from structural 

complexities for some distance on either side of the Phosphoria. If 

the grade and amount of phosphate found in the Trail Canyon section 

is characteristic of this outcrop, it is of high economic importance. 

A limited amount of strip mining may be possible southward from the 

Middle Sulphur Canyon area along this line of outcrop. Other small 

areas of outcrop are in fault blocks throughout the quadrangle but 

these rocks generally can be rejected from economic considerations 

because of their structural complexity and limited downward extension.

LITERATURE CITED

Baker, A. A., Huddle, J. W., and Kinney, D. M., 1949, Paleozoic geology of the 

north and -west sides of Uinta Basin, Utah: Am. Assoc. Petroleum Geologists 

Bull., v. 33, p. 1161-1197.

Cressman, E. R., and Gulbrandsen, R, A., 1955, Geology of the Dry Valley

quadrangle, Idaho: U. S. Geol. Survey Bull. 1015-1. 

Gale, H. S., and Richards, R. W., 1910, Preliminary report on the phosphate

deposits in southeastern Idaho and adjacent parts of Wyoming and Utah:

U. S. Geol. Survey Bull. 430-H, p. 457-535.

Kummel, Bernard, 1953, Regional relationships of Triassic formations in eastern

Idaho and adjacent areas: Intermountain Assoc. Petroleum Geologists,

Guidebook Fourth Ann. Field Conf., p. 48-53.

 1954, Triassic stratigraphy of eastern Idaho and adjacent areas: U. S. 

Geol. Survey Prof. Paper 254HH.

Long, A. E., 1949, Experimental diamond core-drilling in the Phosphoria formation in southeastern Idaho: U. S.. Bureau of Mines Rept. Inv. 4597.

Mansfield, G. R., 1916, Subdivisions of the Thaynes limestone and Nugget sandstone, Mesozoic, in the Fort Hall Indian Reservation, Idaho: Wash. Acad. 

Sci. Jour., v. 6, p. 31-42.

 1927, Geography, geology, and mineral resources of part of southeastern

Idaho: U. S. Geol. Survey Prof. Paper 152.

McKelvey, V. E., Armstrong, F. C., Gulbrandsen, R. A., and Campbell, R. M., 

1953, Stratigraphic sections of the Phosphoria formation in Idaho 1947-48, 

part 2: U. S. Geol. Survey Circ. 301.
GEOLOGY, JOHNSON CREEK QUADRANGLE, CARIBOU CO., IDAHO 21

McKelvey, V. E., Davidson, D. F., O'Malley, F. W., and Smith, L. E., 1953,

Stratigraphic sections of the Phosphoria formation in Idaho 1947-48, part 1:

U. S. Geol. Survey Circ. 208.

Miller, A. K., and Cline, L. M., 1934, The cephalopods of the Phosphoria formation of the northwestern United States: Jour. Paleontology, v. 8, p. 281-283. 

Newell, N. D., 1948, Key Permian section, Confusion Range, western Utah:

Geol. Soc. America Bull., v. 59, p. 1053-1058. 

Newell, N. D., and Kummel, Bernard, 1941, Permo-Triassic boundary in Idaho,

Montana, and Wyoming: Am. Jour. Sci., v. 239, p. 204-208. 

Richards, R. W., and Bridges, J. H., 1911, Sulphur deposits near Soda Springs,

Idaho: U. S. Geol. Survey Bull. 470-J. 

Richards, R. W., and Mansfield, G. R., 1911, Preliminary report on a portion of

the Idaho phosphate reserve: U. S. Geol. Survey Bull. 470-H, 371-439. 

 1912, The Bannock overthrust, a major fault in southeastern Idaho and

northeastern Utah: Jour. Geology, v. 20, p. 681-709. 

Richardson, G. B., 1913, The Paleozoic section in northern Utah: Am. Jour.

Sci., 4th series, v. 36, p. 406-416. 

Swanson, R. W., McKelvey, V. E., and Sheldon, R. P., 1953, Progress report on

investigations of western-phosphate deposits: U. S. Geol. Survey Circ. 297. 

Thompson, M. L., Wheeler, H. E., and Hazzard, J. C., 1946, Permian fusulinids

of California: Geol. Soc. America Mem. 17, p. 8. 

Williams, J. Steele, 1938, Pre-Congress Permian conference in the U. S. S. R.:

Am. Assoc. Petroleum Geologists Bull., v. 22, p. 772. 

Williams, J. Stewart, 1948, Geology of the Paleozoic rocks, Logan quadrangle,

Utah: Geol. Soc. America Bull., v. 59, p. 1121-1164. 

Zeni, M., 1953, Geology of Sheep Creek Anticline, Bear Lake County, Idaho:

Intermountain Assoc. Petroleum Geologists, Guidebook Fourth Ann. Field

Conf., p. 80-82.

INDEX

Page 

Accessibility. ....... - 3-4

Acknowledgments... . 3

Aspen Range anticline, description.. ... 15

faulting-...-...... 15

Bannock overthrust. See Faults.

Brazer limestone, distribution.. 7, pi. 1 

fossils.-...-..- _... 7 

lithologlc character. , 4-7 

measured sections nearby . 5,6-7 

thickness 4,5,6

thickness of individual units... 5-7 

type section. 4

Dinwoody formation, description of lower

member......._ 12

description of upper member 12 

distribution .... 12.pl. 1

thickness.... ...__.__.___-_... 12

thickness of lower member..._ 12 

thickness of upper member 12 

typo locality ... _ 11

Faults, Bannock overthrust . 16,17 

economic Importance.- _ 18,20 

normal faults..___.___._ 16 

relation to folding... 17 

tear faults .. 16 

thrust fault_____._...... 15

Folding, overturned strata...___--..... 15 

relation to faulting.. 17

Introduction.__._ 1-3

Literature cited. ....................... 20-J1

Location..._ 1-2

Meekoceras............................. 11,12,13,17

Mineral deposits ._ _ _...._ 4

See also Phosphate deposits. 

Mississlppian rocks. See Brazer limestone.

Pennsylvanian and Permlan(?) rocks. See 

Wells formation.

Permian rocks. See Phosphorla formation.

Phosphate deposits, composition of phosphate

rock______.___...._ 17

continuity____.__ 18 

current mining operations. ________ 19 

exploratory strip mining _...._ 19

exploratory trenching... .... . 19

furnace-grade shale, grade. ......... 18,19

furnace-grade shale, thickness...____ 18,19 

Importance of faulting__________. 18,20 

location of drill holes. _.___ _ 17-18 

location of trench samples . 17 

lower zone, grade. . 18,19 

lower zone, thickness___________ 18,19 

middle mudstone zone, grade. _ 19 

middle mudstone zone, thickness____ 19 

possible future mining locations. -___. 20 

upper zone, effect of depth and weathering.. .. __..... 18-19

Page

Phosphate deposit Continued

upper zone, grade........___... .. 18,19

thickness __...___.... 18,19

See also Phosphorla formation, phosphatlc

shale member. 

Phosphorla formation, age____._....... 10

distribution. _.............. 11, pi. 1

generalized section________ .... pi. 2

phosphatic shale member, analyses.. .. 19

phosphatlc shale member, grade of rock.. 18,19

lithologic character._.___ .. 10-11

phosphate rock__. _ .. 11

thickness______________. 10

Rex chert member, lithologic character... 11

Rex chert member, thickness______. 11

thickness...________._.._ 10, pi. 2

type section_______________. 10

See also Phosphate deposits.

Physiographic features .._ 3, pi. 1

Previous investigations______.____. 2,3

Quaternary rocks_.___._...._ . 14, pi. 1

Relief.... . 3

Sguamularia..... . 9

Stratigraphy, general . .. 4 

See also particular formations and ages.

Structural features, general........_ 14, pi. 1

sections...__.__ __ _...._. pi. 1

sequence of formation..... 17

See also Aspen Range anticline, Faults, 

Folding, and Trail Creek syncllne.

Tertiary and Quaternary rocks, description_ 14 

distribution..___________.... 14, pi. 1 

mapped together.. .. _ 14

Tertiary rocks. See Tertiary and Quaternary 

rocks.

Thaynes formation, description of four members. . 13-14 

distribution....__....._.__...... 14, pi. 1

division in areas nearby...________ 13 

division in report area_______.___ 13 

thickness of four members________ 13,14

Trail Creek syncllne, description. ______ 14-16 

folding. . _......... 15

Trlasslc rocks. See Dinwoody and Thaynes 

formations.

Wells formation, age correlation.... ..... 7-8

description of lower member ______ 9 

description of upper member______ 9 

distribution...._______._____ 10, pi. 1

lithologic character. ......._......... 8-10

measured section nearby.. . 8-9 

stratlgraphic Importance of upper member .. .. 9-10 

thickness__... ....... ......... 7,8

thickness of lower member...______ 9 

thickness of upper member...__._... 9 

type section 7

23

V. ». GOVERNMENT PRIHTIHS OFFICEi 1958