STUDIES RELATED TO WILDERNESS

STUDY AREAS

Depository

RFCElVf D

EBOT 'SCO

STURGEON RIVER WI 

STUDY AREA, MICHIG

GICAL SURVEY BULLETIN 1465

Mineral Resources of the 

^ Sturgeon River Wilderness Study Area, 

Houghton and Baraga Counties, 

Michigan

By W. F. CANNON and ELIZABETH R. KING, U.S. GEOLOGICAL SURVEY,

* and by JAMES J. HILL and PETER C. MORY, U.S. BUREAU OF MINES

 &

- STUDIES RELATED TO WILDERNESS STUDY AREAS

An evaluation of the mineral 

potential of the area

UNITED STATES GOVERNMENT PRINTING OFFICE. WASHINGTON : 1980
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard Director

Library of Congress catalog-card No. 80-600000

For sale by Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402

Stock Number 024-001-03259-7
STUDIES RELATED TO WILDERNESS 

STUDY AREAS

In accordance with the provisions of the Wilderness Act (P.L. 

88-577, September 3, 1964) and the 

Joint Conference Report on Senate 

Bill 4, 88th Congress, and as specifically designated by P.L. 93-622, 

January 3, 1975, the U.S. Geological 

Survey and U.S. Bureau of Mines have 

been conducting mineral surveys of 

wilderness and primitive areas.

Studies and reports of all primitive 

areas have been completed. Areas 

officially designated as "wilderness," "wild," or "canoe" when the 

act was passed were incorporated into the National Wilderness Preservation System, and some of them are 

presently being studied. The act 

provided that areas under consideration for wilderness designation 

should be studied for suitability 

for incorporation into the Wilderness System. The mineral surveys 

constitute one aspect of the suitability studies. This report discusses the results of a mineral survey of national forest land in the 

Sturgeon River Wilderness study 

area, Michigan, that is being considered for wilderness designation 

(P.L. 93-622, January 3, 1975). The 

area studied is in the Ottawa National Forest in Houghton and Baraga 

Counties in the Upper Peninsula of 

Michigan.

CONTENTS

H -

Page

Summary -------------------- i

Introduction, by W. F. Cannon, James J. Hill,

and Peter C. Mory -------------- 2

Area description- ------------- 2

Present investigation ----------- 5

Geology and geophysical interpretation, by

W. F. Cannon and Elizabeth R. King- ----- 6

Introduction- --------------- 6

Physiography- --------------- 12

Lithology ----------------- 13

Pleistocene glacial deposits- ------ 14

Jacobsville Sandstone ---------- 15

Diabase dikes -------------- 15

Basalt- ----------------- 16

Michigamme Formation- ---------- 18

Stratigraphy and structure- -------- 19

Mineral-resource potential of known deposits,

by James J. Hill and Peter C. Mory- ----- 24

Land status ---------------- 24

Surface ownership ------------ 25

Mineral ownership ------------ 25

Mining activity -------------- 25

Prospecting activity- ----------- 27

Within the area ------------- 27

Silver Mountain ------------- 27

High-silica sand- ------------ 33

Stone ------------------ 37

Sand and gravel ------------- 37

Clay- ------------------ 38

Peat- ------------------ 38

Potential for undiscovered mineral deposits, 

by W. F. Cannon, James J. Hill, and

Peter C. Mory ---------------- 42

Assessment by geologic environment- - - - - 42

Michigamme Formation- - --------- 42

Basalt and diabase dikes- -------- 43

Jacobsville Sandstone ---------- 43

Glacial deposits- ------------ 44
VI CONTENTS

Potential for undiscovered mineral deposits Con. 

Assessment by geochemical survey- ----- 44

Soil samples- -------------- 44

Stream sediments- ------------ 45

Bedrock ----------------- 47

References cited- --------------- 48

ILLUSTRATIONS

Page

FIGURE 1. Index map showing study area - - - - 2 

2, 3. Photographs showing:

2. Waterfalls on Sturgeon River - 3

3. Gorge downstream from falls- - 4

4. Map of study area showing locations

of sample sites- --------- 7

5. Aeromagnetic map of study area - - - 9

6. Regional aeromagnetic map- ----- 10

7. Regional Bouguer anomaly gravity map 11

8. Photograph showing a view of study

area from Silver Mountain- - - - - 13

9. Schematic geologic cross section in

study area ------------ 14

10. Bedrock geologic map of study area - 16

11. Photograph showing Pleistocene

glacial deposits along Sturgeon 

River- -------------- 18

12. A typical aeromagnetic profile - - - 21

13. Density model of study area- - - - - 23 

14-16. Maps showing:

14. Federal surface ownership in

study area- -------- 26

15. Federal mineral ownership in

study area- -------- 28

16. Prospects on Silver Mountain 31

17. Map and section of Silver Mountain

adit --------------- 33

18. Photograph showing Pleistocene 

glacial deposits along 

Sidnaw Creek ----------- 39
CONTENTS VII 

TABLES

TABLE 1. Mineral ownership within and

adjacent to the Sturgeon River 

Wilderness study Area ------- 29

2. Partial chemical analyses of samples 

from the Sturgeon River Wilderness 

Study Area- ------------ 34

3. Evaluation of glacial clay samples- - 40

4. Comparison of analyses of some 

stream sediments and heavy 

mineral pan concentrates- ----- 46
CONVERSION FACTORS

Metric unit Inch-Pound equivalent

Length

millimeter (mm) 

meter (m) 

kilometer (km)

= 0.03937 inch (in) 

= 3.28 feet (ft) 

= .62 mile (mi)

Area

square meter (m2 ) 

square kilometer (km2 ) 

hectare (ha)

= 10.76 square feet (ft2 ) 

= .386 square mile (mi2 ) 

= 2.47 acres

Volume

cubic centimeter (cm3 ) 

liter (L) 

cubic meter (m3 ) 

cubic meter 

cubic hectometer (hm3 ) 

liter 

liter 

liter 

cubic meter

cubic meter

= 0.061 cubic inch (in3 ) 

= 61.03 cubic inches 

= 35.31 cubic feet (ft3 ) 

= .00081 acre-foot (acre-ft) 

= 810.7 acre-feet 

= 2.113 pints (pt) 

= 1.06 quarts (qt) 

= .26 gallon (gal) 

= .00026 million gallons (Mgal or 

10« gal) 

= 6.290 barrels (bbl) (1 bbl = 42~gal)

Weight

gram (g) 

gram 

metric tons (t) 

metric tons

= 0.035 ounce, avoirdupois (oz avdp) 

= .0022 pound, avoirdupois (Ib avdp) 

= 1.102 tons, short (2,000 Ib) 

= 0.9842 ton, long (2,240 Ib)

Specific combinations

kilogram per square 

centimeter (kg/cm2 ) 

kilogram per square 

. centimeter 

cubic meter per second 

(mVs)

_ 0.96 atmosphere (atm)

- .98 bar (0.9869 atm) 

= 35.3 cubic feet per second (fts/s)

Metric unit

Speci

liter per second (L/s) 

cubic meter per second 

per square kilometer 

[(m3/s)/km2 ] 

meter per day (m/d)

meter per kilometer 

(m/km) 

kilometer per hour 

(km/h) 

meter per second (m/s

meter squared per day 

(mVd) 

cubic meter per second 

(m?/s) 

cubic meter per minute 

(m3/min) 

liter per second (L/s) 

liter per second per 

meter [(L/s)/m] 

kilometer per hour 

(km/h) 

meter per second (m/s

gram per cubic 

centimeter (g/cm3 ) 

gram per square 

centimeter (g/cm2 ) 

gram per square 

centimeter

degree Celsius (°C) 

degrees Celsius 

(temperature)

V
STUDIES RELATED TO WILDERNESS-STUDY AREAS

MINERAL RESOURCES OF

THE STURGEON RIVER WILDERNESS

STUDY AREA, HOUGHTON AND

BARAGA COUNTIES, MICHIGAN

By W. F. Cannon and Elizabeth R. King,

U.S. Geological Survey

and James J. Hill and Peter C. Mory,

U.S. Bureau of Mines

SUMMARY

The mineral-resource potential of the Sturgeon River 

Wilderness Study Area is low, despite the fact that the area is 

in this prolific mineral-producing Upper Peninsula of Michigan. 

Within 50 km of the area lie major iron and copper districts, 

and uranium exploration is currently underway to the east of the 

area.

This study did not disclose any mineral deposits that could 

be mined economically. Minor resources of stone, sand and 

gravel, clay, and peat exist in the area but warrant little 

attention because they lie far from present markets.

A complete lack of favorable signs of mineralization in the 

study area and immediate surroundings indicates a very low 

potential for the existence of undiscovered mineral deposits. 

The graywacke and slate turbidite sequence of the Michigamme 

Formation, which underlies about two-thirds of the area, does 

not contain any known economically attractive minerals anywhere 

in the Upper Peninsula. Lower Keweenawan basalt and related 

diabase dikes, which are in some respects similar to middle 

Keweenawan native copper-bear ing basalts elsewhere, underlie 

about one-third of the area. They are barren of mineralization 

both within the area and at all other localities where they have 

been studied. The Jacobsville Sandstone, the youngest bedrock 

unit in the area, is similarly barren of significant 

mineralization in all its numerous exposures in the Upper 

Peninsula.

Pleistocene glacial deposits, and the alluvial deposits 

derived from them, contain small quantities of heavy minerals, 

including titanium and zirconium-bearing minerals, but not in 

concentrations approaching economic grade and size.

1
STUDIES RELATED TO WILDERNESS

INTRODUCTION

By W. F. Cannon, James J. Hill, and Peter C. Mory

The mineral-resource potential of the Sturgeon 

River Wilderness Study Area (fig. 1) was studied by 

personnel of the U.S. Geological Survey and U.S. 

Bureau of Mines in 1975. The survey revealed no 

deposits of current economic value and a very low 

possibility that undiscovered deposits of potential 

economic value are in the area.

AREA DESCRIPTION

The Sturgeon River Wilderness Study Area comprises approximately 53 km and lies wholly within

90° 89° 88°

0 25 50 KILOMETERS

47°

MICHIGAN

46° WISCONSIN

Figure 1. Index map of part of Michigan showing the 

location of the Sturgeon River Wilderness Study 

Area.
STURGEON RIVER WILDERNESS 3

Ottawa National Forest in Houghton and Baraga Counties in the northern peninsula of Michigan.

The area is easily reached by traveling about 5 

km north on Forest Service road 191, which joins 

Michigan Highway 28 immediately east of the town of

Figure 2. Waterfalls on the Sturgeon River. 

Bedrock is basalt flows of the Siemens Creek 

Formation that dip gently in a downstream direction.
4 STUDIES RELATED TO WILDERNESS

Sidnaw, Mich., or by traveling about 15 km south on 

Forest Service road 191 from Michigan Highway 35 

from near Alston, Mich. Forest Service roads 191, 

192, and 193 provide access to much of the study 

area's perimeter. Access to the interior is by foot 

over logging trails, now closed to motor vehicle 

traffic. Railroad tracks of the Soo Line pass within 3 km of the southern boundary of the area.

The northwest-flowing Sturgeon River and its 

tributaries have incised deep valleys, mostly 

through unconsolidated glacial deposits. Elevations 

range from about 244 m in the north to 427 m in the 

south. The most scenic attractions are Sturgeon 

Falls (fig. 2), caused by basalt flows, and the 

gorge carved through basalt and overlying sandstone 

immediately downstream from the falls (fig. 3).

Trees include birch, aspen, maple, red pine, 

white pine, jack pine, balsam fir, cedar, and hemlock. Although the area has been logged extensively, several mature stands of timber remain.

Figure 3. Gorge downstream from waterfalls. The 

gorge is cut through horizontally layered 

Jacobsville Sandstone and basalt of the Siemens 

Creek Formation at lower left of exposure.
STURGEON RIVER WILDERNESS 5

The area has been used especially for timbering and recreation. Ownership records indicate 

that the area may have been considered as a site 

for hydroelectric power.

PRESENT INVESTIGATION

The mineral-resource potential of the area was 

evaluated by several means. Previously collected 

geologic and geophysical data from many sources 

were compiled to give a geologic framework on which 

to base field studies and by which a preliminary 

assessment could be made.

Fieldwork included examining known outcrops of 

bedrock for favorable signs of mineralization and 

sampling the bedrock for laboratory tests. All 

previously reported exposures of bedrock were located, and their positions were plotted on a topographic base map. No additional exposures were 

found. Because of the very limited number of outcrops in the area, rock units known or inferred to 

be present in the area were examined and sampled at 

their nearest known exposures outside the area. 

Clay beds in Pleistocene glacial deposits were also 

sampled to test their suitability for ceramic 

uses. We collected samples of soil and stream sediments throughout the area that were analyzed in 

the laboratory for metal content. Stream sediments 

were collected at several places along the Sturgeon 

River and from each major tributary. Because these 

streams derive their sedimentary load almost totally from the Pleistocene deposits, metal concentrations in these deposits will be detected in stream 

sediment samples more so than in soils. The location of sample sites is shown in figure 4.

Samples collected by the U.S. Bureau of Mines 

were analyzed spectrographically for 43 elements by 

the Reno Metallurgy Research Center of the U.S. Bureau of Mines, Reno, Nev. Selected samples were 

analyzed by fire assay methods for gold and silver. Copper content was determined by atomic absorption. Uranium scans were performed on all sandstone samples. The Tuscaloosa Metallurgy Research 

Center of the U.S. Bureau of Mines, Tuscaloosa, 

Ala., evaluated ceramic properties of glacial clays.
6 STUDIES RELATED TO WILDERNESS

Samples collected by the U.S. Geological Survey were tested for 65 elements by semiquantitative 

spectrographic analysis, and selected samples were 

analyzed for gold by combined fire assay-atomic absorption procedure at the U.S. Geological Survey 

analytical laboratories, Reston, Va. All exposures 

of bedrock were tested in the field for uranium by 

using a portable scintillometer.

Data on mineral-right ownerships were obtained 

from the U.S. Forest Service and were updated by 

examining records at the Baraga and Houghton County 

courthouses. Bureau of Land Management records 

were checked for leasing activity.

Representatives of the mining industry, as 

well as State and Federal agencies, were asked to 

give their views on the mineral resource potential 

of the area.

GEOLOGY AND GEOPHYSICAL INTERPRETATION

By W. F. Cannon and Elizabeth R. King

INTRODUCTION

The Sturgeon River Wilderness Study Area is 

astride a major geologic contact between Precambrian rocks of two different ages, types, and geologic histories. About two-thirds of the area is 

underlain by middle Precambrian (Precambrian X) 

graywacke and slate, deposited in a deep ancient sea 

about 2 billion years ago. These rocks have subsequently been deformed and recrystallized, uplifted, and then deeply eroded. The northern third of 

the area is underlain by much younger basalt, about 

1 billion years old, that was extruded in a continental environment. The basalt flows were later 

tilted and eroded and then covered by younger sandstone. As recently as 10,000 years ago, continental glaciers covered the area. When the last of 

these melted, the area was covered with a thick 

blanket of sediments deposited from the glacial 

meltwaters.
STURGEON RIVER WILDERNESS

R. 36 W. 88°40' R. 35 W.

46°40'

46°35' -

Base from U.S. Geological Survey, 1954

0 .5 1 2 3 4 KILOMETERS

0 Vi 1 2 MILES 

EXPLANATION

X Samples collected by U.S. Geological Survey 

O Samples collected by U.S. Bureau of Mines

Figure 4. The Sturgeon River Wilderness 

Study Area showing the locations of sample sites.
8 STUDIES RELATED TO WILDERNESS

Only locally, near Sturgeon Falls, has erosion 

removed the glacial deposits to expose the underlying bedrock. Consequently, little is known directly of the bedrock in the area. Aeromagnetic and 

gravity surveys, however, along with projection of 

information from outcrops outside the wilderness, 

provide a means of inferring the general geologic 

relationships.

An airborne magnetometer survey of the Sturgeon River Wilderness Study Area was made by the 

U.S. Geological Survey in 1947 as part of a larger 

program to investigate the Upper Peninsula of Michigan for mineral resources, primarily iron and copper (Balsley and others, 1949). The survey was 

made by using a continuously recording fluxgate 

magnetometer along north-south flight lines spaced 

0.25 mi (0.40 km) apart and 500 ft (150 m) above 

the ground surface. The data were published as 

magnetic profiles and an accompanying map showing 

the flight lines and locations of the magnetic 

peaks and troughs (Balsley and others, 1949). 

These data were later compiled as a contour map 

with a contour interval of 50 gammas (50 nT) (Balsley and Smith, 1967). A part of this map is shown 

in figure 5.

The entire Upper Peninsula has now been covered by similar surveys by the U.S. Geological Survey. The data were recompiled as a single contour 

map after the gradient of the Earth's magnetic 

field was removed, so that only the anomalies 

caused by the rocks of the Earth's crust remain 

(Zietz and Kirby, 1971). Figure 6 shows part of 

this map, including the area of the Sturgeon River 

Wilderness Study Area.

Aeromagnetic surveys record variations in the 

Earth's total magnetic field, which are caused primarily by differences in the magnetic mineral content of the rocks beneath the surveying aircraft. 

Although several minerals are magnetic, the most 

important and common one is magnetite. Small amounts of magnetite are disseminated through many 

types of igneous rocks and give the rocks characteristic magnetic expressions. The resulting magnetic patterns are used by geologists to map these
STURGEON RIVER WILDERNESS

88P45' R.36W R. 35 W.

46°40'

46°35' -

Base from US Geological Survey, 1954

0 ,5 1 234 KILOMETERS 

_J____|_____|

0 Vi 1 2 MILES

Figure 5. Aeromagnetic map of map of 

the Sturgeon River Wilderness Study 

area (part of a map by Balsley and 

Smith, 1967). Contour interval is 50 

gammas (50 nT). Profile along line 

A-A 1 is shown in figure 12. Flight 

lines trend N-S at 0.4-km intervals.
10 STUDIES RELATED TO WILDERNESS

88°45' 88°30'

46°45'

46°30'

i i i i

I T I I

15 KILOMETERS

I 

SMILES

Figure 6. Regional aeromagnetic expression of three 

geologic terranes in the vicinity of the Sturgeon 

River Wilderness Study Area (part of a map by 

Zietz and Kirby, 1971). Contour interval is 

100 gammas (100 nT). Dashed lines separate zones 

of different magnetic character. Zones A, B, and 

C are discussed in the text.
STURGEON RIVER WILDERNESS 11

rocks, even where they are covered by soil, glacial 

drift, or sedimentary rocks (which are commonly much 

less magnetic). Magnetite also occurs in metamorphic rocks, such as the iron-format ion of the 

iron districts of Michigan, Minnesota, and Wisconsin.

46°45'

46°30'

15 KILOMETERS 

J

0 5 MILES

Figure 7. Regional Bouguer anomaly gravity map 

of the Sturgeon River Wilderness Study Area and 

surrounding area (modified from a map by Bacon, 

1966) . Contour interval is 2 mgal (2 X 10* 

m/s 8 ). Circles indicate locations of gravity 

stations. Profile along line B-B 1 is shown in 

figure 13.
12 STUDIES RELATED TO WILDERNESS

Another geophysical method that is useful in 

this region is the measurement of variations in 

gravity (Bacon, 1966). Dense rocks, such as basalt, 

have a higher gravitational attraction than the 

granitic and metamorphic rocks typical of much of 

the region. Sedimentary rocks, such as sandstone 

and arkose, have relatively low density and produce 

lower gravitational attraction.

A large number of gravity measurements have 

been made in the Upper Peninsula and have been compiled and contoured as a regional map by Bacon 

(1966). The measurements in the Sturgeon River area 

were made by Campbell (1952) along road traverses 

separated by approximately 10 mi (16 km) with stations spaced about every mile. The gravity anomalies of this map, part of which are shown in figure 

l t show a good correlation with the regional magnetic patterns. Thus, it is possible to infer the distribution of dense, magnetic units of rocks. In 

some places, the gravity data can be used to calculate the approximate thickness of buried rock, units.

PHYSIOGRAPHY

The Sturgeon River Wilderness Study Area lies 

near the west edge of the Baraga Plains, a gently 

rolling upland underlain by thick Pleistocene glacial deposits. The study area contains deep (as 

much as 100 m) steep-sided gorges cut into the Baraga plains by the north-flowing Sturgeon River and 

its tributaries. Flat uplands, remnants of the once 

more extensive Baraga Plains, lie between the 

gorges. The steep topography of the area is in 

striking contrast to the gently rolling topography 

of much of the surrounding area (fig. 8).

The Sturgeon River is largely a graded meandering stream that has a narrow flood plain. Lateral 

cutting against steep valley sides locally forms 

oversteepened slopes and results in prominent 

slumping and landsliding.

Only at Sturgeon Falls in sec. 16, T. 49 N., R. 

35 W., and for a few hundred meters downstream from 

the falls, does the river flow on bedrock. There, 

the river is fast moving with short reaches of white
STURGEON RIVER WILDERNESS 13

p..

water. Elsewhere, it is slow moving and flows on

* unconsolidated Pleistocene deposits (or river sand 

and gravel derived from the deposits).

LITHOLOGY

Five stratigraphic units are present in the 

> Sturgeon River Wilderness Study Area. The stratij graphic relationships are shown in figure 9, and 

their areal distribution is shown in figure 10.

Only three of the units, Pleistocene glacial 

I deposits, Jacobsville Sandstone, and basalt of the 

Siemens Creek Formation, are exposed in the wilderi ness. Diabase dikes of Keweenawan age and gray4 wacke and slate of the Michigamme Formation are inferred to be present because a distinctive magnetic 

pattern produced by these exposed rocks in nearby 

, areas extends into the Wilderness Study Area.

Figure 8. View from Silver Mountain looking southeastward. The Sturgeon River Wilderness Study Area 

is in the foreground. Steep-sided stream valleys 

in the study area are cut into the Baraga Plains, 

which form the flat upland surface in the distance. 

Higher hills on the horizon are underlain by 

graywacke and slate of the Michigamme Formation.
14

NW

STUDIES RELATED TO WILDERNESS

'Present topographic surface SE

Basalt 

(Siemens Creek Formation)

Figure 9. Schematic cross section of the Sturgeon 

River Wilderness Study Area showing the stratigraphic, intrusive, and structural relationships of the rock units in the area.

PLEISTOCENE GLACIAL DEPOSITS

Pleistocene glacial deposits form a thick blanket of unconsolidated material over most of the 

area. The steep stream gorges are cut mostly 

through this material, but, because it slumps rapidly, exposures of undisturbed material are rare and 

confined to areas where streams are actively cutting 

laterally into valley sides (fig. 11). Most of the 

material is light-brown, rather well-sorted sand 

composed mostly of quartz and lesser amounts of 

feldspar. Heavy minerals generally form less than 1 

percent of the sand. The sand is well bedded (fig. 

11, top), and crossbedding is common. Locally, 

gravel beds as much as 1 m thick are inter bedded 

with the sand.

Units of silt-and clay-size particles, generally 

well intermixed, also make up a part of the Pleistocene deposits. They are reddish-brown to tan and 

generally massive with no discernible internal bedding (fig. 11, center). Units as much as 6 m thick 

are exposed along the Sturgeon River, but the lateral continuity of such beds is not known.
STURGEON RIVER WILDERNESS 15 

JACOBSVILLE SANDSTONE

The Jacobsville Sandstone is exposed in nearly 

vertical valley walls along the Sturgeon River near 

Sturgeon Falls (fig. 3). It is well bedded in nearly horizontal units. Crossbedding and ripple marks 

are common. Owing to alternate zones in which small 

amounts of iron are in reduced and oxidized form, 

the color varies on a small scale from very light 

tan to red brown. In places, such zones follow bedding planes, making the bedding very easily visible 

(fig. 3) . According to Roberts (1940), grain size 

varies from conglomeritic beds having 1-cm pebbles 

to beds of very fine sandstone. Average grain size 

is about 1 mm. The sand grains are generally well 

rounded and in well-sorted beds. The average mineral composition near Sturgeon Falls is 50 percent 

quartz, 30 percent potassium feldspar, 10 percent 

muscovite, and 2 percent plagioclase. The remainder 

is mostly heavy minerals. The heavy-mineral suite 

consists of about 10 percent garnet, 3 percent leucoxene, 1-2 percent zircon, and the remainder is 

opaque minerals, mostly magnetite and ilmenite (Denning, 1949) .

DIABASE DIKES

No diabase dikes are exposed in the area, but 

their presence is inferred from very distinctive 

west-trending linear negative magnetic anomalies 

that are invariably associated with diabase dikes to 

the east, where bedrock is better exposed. There, 

the rock ranges from coarse- to fine-grained massive 

diabase consisting of plagioclase, clinopyroxene, 

and rarely olivine, as well as small amounts of magnetite and other opaque minerals. Large boulders of 

diabase are found along the bed of the Sturgeon River near the falls and may be locally derived. The 

nearest exposure of diabase is at Mt. Kallio, about 

2 km east of the area (fig. 10) .
16 STUDIES RELATED TO WILDERNESS

88-40' R.35W.

46°35'. -

Base from US Geological Survey, 1954

0 .5 1 2 3 4 KILOMETERS

i I____|____|____

2 MILES

Figure 10. (See caption on facing page.)

BASALT

Basalt is exposed at Sturgeon Falls and at several other places for a short distance downstream 

(northward) from the falls. These rocks were assigned by Hubbard (1975) to the Siemens Creek Formation that he named for rocks near Bessemer, Mich., 

about 100 km to the west. Basalt of the Siemens 

Creek Formation is also exposed on Silver Mountain 

immediately north of the study area. These rocks
STURGEON RIVER WILDERNESS 17

EXPLANATION

Yjs Jacobsville Sandstone Reddish sandstone con- Ykd Diabase dikes Inferred from aeromagnetic

taining minor conglomerate and shale pattern

interbeds. Variably bleached to very light n-^-n

brown giving mottled appearance in outcrop '.^. Michigamme Formation Inferred from

Siemens Creek Formation Thick flows of basalt ' ' aeromagnetic pattern to be interbedded

consisting of fine-grained andesine and graywacke and slate

pyroxene. In places metamorphosed am- css?^, Outcrop area 

phibolite. Commonly vesicular near flow

margins Contact Approximately located

Figure 10. Bedrock geologic map of the Sturgeon 

River Wilderness Study Area based on magnetic 

patterns and showing the inferred distribution of 

Michigamme Formation, diabase dikes, and lower 

Keweenawan basalt. The extent of the Jacobsville 

Sandstone away from its only exposures along the 

Sturgeon River is not known. A thin blanket of 

Jacobsville probably overlies much of the area, 

though it is not shown in this map. The thickness 

of dikes shown on the map is the maximum thickness 

consistent with the shape of aeromagnetic anomalies, but, because of uncertainties in interpretation, they may be thinner than shown.

were studied in detail by Roberts (1940). At Sturgeon Falls he recognized three separate flows by 

identifying amygdaloidal zones that formed near the 

top and bottom contact of each flow. The flows are 

fine-grained (~1 mm) black massive basalt. The 

average mineral content is 45 percent andesine, 25 

percent chlorite, 20 percent augite, 5 percent 

magnetite and other opaque minerals, and 2 percent 

epidote. Amygdules are filled with combinations of 

quartz, calcite, epidote, potassium feldspar, and 

ankerite.

On Silver Mountain, Roberts found at least 14 

flows, each from 1 to 6 m thick. There, the basalt 

is metamorphosed, and original augite was converted 

to hornblende (which makes up about 40 percent of 

the rock). Andesine (40 percent), calcite (10 percent) , and leucoxene (5 percent) are other important 

constituents.

At an exposure about 300 m downstream from 

Sturgeon Falls, the basalt is overlain unconformably 

by the Jacobsville Sandstone. Weathering prior to
18 STUDIES RELATED TO WILDERNESS

Figure 11. Exposure of Pleistocene glacial deposits in a stream bank along the Sturgeon River. Crossbedded sand (lighter colored material 

near top) overlies a bed of clay (darker colored massive-appearing material near center), 

which is underlain by stratified sand mostly 

covered by slumped material near the bottom of 

the exposure.

deposition of the Jacobsville has produced a reddish-brown color in the basalt and a partially disaggregated rubbly texture. As much as 2 m of this 

soft, rubbly weathered rock is preserved beneath the 

Jacobsville.

MICHIGAMME FORMATION

The Michigamme Formation is not exposed in the 

wilderness study area. Large areas to the south and 

east of the study area are underlain by a monotonous 

sequence of graywacke and slate. The nearest outcrops are about 3 km southeast of the study area. 

These rocks are commonly in graded beds 0.5 to 1m 

thick that range from coarse-grained graywacke at 

their base to fine-grained dark-gray to black slate 

near their top. The rocks are folded about west-
STURGEON RIVER WILDERNESS 19

northwest-trending axes, and cleavage is generally 

well developed, especially in the tops of graded 

beds. Areas known to be underlain by the Michigamme 

Formation produce a characteristic uniformly low 

magnetic field. The extension of that magnetic pattern from areas where the Michigamme is exposed into 

parts of the wilderness study area indicates that 

much of the area is underlain by similar graywacke 

and slate.

STRATIGRAPHY AND STRUCTURE

In spite of sparse exposures of bedrock in the 

study area, the stratigraphic and structural relationships can be inferred with confidence because of 

abundant geophysical data. The geologic map of the 

area (fig. 10) is drawn from aeromagnetic data. 

Figure 6 shows that the wilderness study area and 

surroundings can be divided into three zones, each 

having a characteristic magnetic signature. Zone C 

is characterized by uniform and relatively low magnetic attraction. Southeast of the study area, we 

know this magnetic low correlates with thick graywacke and slate of the Michigamme Formation. We infer, therefore, that the southern part of the study 

area is also underlain by Michigamme Formation because it has the same magnetic signature. Zone B is 

characterized by very low magnetic attraction. The 

exposures of the Siemens Creek Formation at Sturgeon 

Falls and Silver Mountain are in zone B and have 

been extensively sampled by Kenneth Books, of the 

U.S. Geological Survey, for magnetic property studies. He found that they have a strong remanent magnetization acquired when the flows cooled. This 

magnetization is alined with the direction of the 

Earth's magnetic field at the time of cooling, 

slightly more than a billion years ago. The direction of magnetization in the Sturgeon River area is 

nearly opposite the direction measured in the much 

thicker series of volcanic rocks of the middle Keweenawan on the Keweenawan Peninsula to the north, 

so that the flows near Sturgeon River produce magnetic lows instead of highs. Books (1968, 1972) 

found this same reversed magnetization in lower Keweenawan flows near Ironwood, Mich. and at other
20 STUDIES RELATED TO WILDERNESS

areas around Lake Superior, so the flows in the 

Sturgeon River area must also be lower Keweenawan.

Zone A, entirely outside the study area, is 

marked by a prominent series of magnetic highs that 

form an arcuate belt that strikes westward without 

interruption into the exposed Keweenawan basalt near 

Ironwood, Mich. (King, 1975). At a depth of 730 m, 

basalt was found in a drill hole 40 km west of the 

Sturgeon River on the crest of this anomaly (Bacon, 

1966). The Jacobsville Sandstone covers the area of 

this magnetic high, which is inferred to mark the 

southern edge of a thick series of Keweenawan basalt 

flows that get progressively deeper to the northwest. This deepening is indicated by the magnetic 

contours that are widely spaced and have lower values in that direction. The gravity data show a 

broad high in that area, indicating the presence of 

a large mass of dense rock, such as basalt.

Both zones B and C have a prominent pattern of 

west-trending negative linear anomalies superimposed 

on them. These can be seen on the contoured maps 

(figs. 5 and 6) but are even more evident on the 

original profiles, one of which is shown in figure 

12. The sharp distinction between zones B and C is 

also well shown on this profile. These anomalies in 

other areas are known to be caused by diabase dikes 

that, like the basalt of the Siemens Creek Formation, have reversed magnetic polarity. The diabase 

and the basalt presumably crystallized during the 

same period of magnetic reversal. Because they do 

not cut anomalies formed by the younger basalts of 

zone A, they are believed to be feeder dikes for the 

lower Keweenawan basalt flows.

Figure 9 shows the stratigraphic and structural 

relationships of the area in schematic form. The 

oldest rocks are the Michigamme Formation, which is 

probably a thick, folded unit of graywacke and 

slate. Volcanic rocks underlying the Michigamme 

Formation well southeast of the area have been dated 

radiometrically at about 2.0 billion years (Banks 

and Van Schmus, 1971). Metamorphism, which was approximately synchronous with deformation, took place 

about 1.9 billion years ago. Although the Michigamme is a highly varied formation in many parts of
] .5 1

. I

2 3

I I

I I

2 MILE

12. A typical aeromagnetic profile from whic

drawn. See figure 5 for the location of the 

Figure 12. 

were dra..... .. __ ._ ..._ ___ _.._ _._.._.... .

areas of low magnetic attraction inferred to be 

diabase dikes.
22 STUDIES RELATED TO WILDERNESS

the Upper Peninsula, the exposures nearest to the 

study area are composed unifbrmly of graywacke and 

slate that were deposited by turbidity currents, 

probably in deep water.

A long gap in the geologic history of the region is represented by the unconformity between the 

Michigamme Formation and the Siemens Creek Formation. The basalt flows of the Siemens Creek spread 

over the erosion surface on the Michigamme. Gravity 

data indicate that the basalts are only a thin sheet 

in the study area and that the Michigamme is present 

in the shallow subsurface (see fig. 13). This is 

consistent with the observed low dips of if lows at 

Sturgeon Falls and Silver Mountain and the position 

of the area near the southeaster nmost edge of the 

basalt flows.

During eruption of the basalt, nearly vertical 

feeder dikes, the Baraga dikes, brought lava to the 

surface along east-west fractures. These dikes have 

been described by Graham (1953), Balsley and others 

(1949), and DuBois (1962). They were evidently emplaced during an early phase of rifting of the Lake 

Superior and midcontinent regions coincident with 

eruption of lower Keweenawan basalt. Shortly afterward, much thicker basalt, forming the middle Keweenawan rocks, accumulated to a thickness as great 

as 15 km. Although these rocks once probably covered the Sturgeon River Area, they have since been 

eroded. The rift in which the Keweenawan rocks accumulated may have been similar to the present African rift system and may have extended from Lake Superior to Kansas. The area invaded by the Baraga 

dikes was one of crustal extension associated with 

the opening of the rift.

After the flows cooled, they were tilted toward 

the northwest, and an erosion surface developed on 

them prior to deposition of the Jacobsville Sandstone. Exposures near Sturgeon Falls indicate that 

local relief was 25 m or more when the area was covered by the Jacobsville. Regional studies by Hamblin (1958) show that the Jacobsville was deposited 

by generally north- or northwest-flowing streams and 

occupied a basin nearly coincident with the present 

Lake Superior drainage basin.
Basalt 

d=2.9

Sandstone t/=2.4~

Basalt d=2.9

Pre-Keweenavyan rocks Ass

15 

0 5 10 

Figure 13. A generalized density model of the 

Study Area and surrounding area (from Bacon, 

ing a theoretical gravity anomaly to coinci

anomaly. The model indicates that Keweenawan 

thin and are underlain at a relatively sha

density, presumably part of the Michigamme 

line B-B 1 is shown in figure 7. This mode

tional data and slight recontouring in figure 
24 STUDIES RELATED TO WILDERNESS

The exact age of the Jacobsville is not known. 

Unconformable relationships with the underlying lower Keweenawan basalt and overlying Munising Sandstone (Upper Cambrian) place only widely spaced limits on the possible age (Hamblin, 1958). It is considered provisionally to be late Precambrian (Precambrian Y).

A long period having no geologic record separates the Jacobsville and Pleistocene deposits. 

Outliers of Ordovician sedimentary rocks at Limestone Mountain, a short distance north of the area, 

suggest that the entire area was once covered with 

Ordovician and possibly other Paleozoic rocks, which 

have since been removed by erosion.

The Pleistocene deposits are mostly fluvial 

sand and gravel deposited south of a retreating continental glacier. The fine-grained clayey beds were 

probably deposited in standing water, perhaps small 

lakes or channels on the fluvial plain.

MINERAL-RESOURCE POTENTIAL OF KNOWN

DEPOSITS

By James J. Hill and Peter C. Mory

An investigation of the mineral-resource potential of known deposits was undertaken by the U.S. 

Bureau of Mines in 1975. Evaluations were made for 

deposits of stone, sand and gravel, clay, and peat, 

as well as for two prospects on Silver Mountain just 

outside the study area. The study disclosed no metallic mineral deposits that can be mined economically. Minor resources of stone, sand and gravel, 

clay, and peat exist in the area, but, because they 

lie far from major demand centers, they are of little economic interest.

LAND STATUS

Investigations of mineral potential in wilderness areas are based in part on evaluations of historical activities and data. Consideration is given 

to the past availability (accessibility) of land to 

individuals and (or) industry engaged in mineral ex-
STURGEON RIVER WILDERNESS 25

ploration. This information can give some insight 

to the thoroughness with which a particular area 

might have been evaluated during times of continually evolving exploration concepts and methods.

SURFACE OWNERSHIP

U.S. Forest Service and courthouse records indicate that before 1934, when the Federal government 

began to purchase national forest land in the area, 

most of the land was in private ownership. Although 

not open to prospecting and location under the General Mining Law of 1872, it is possible that some of 

the area was accessible for exploration either 

through lease option or by actual ownership of surface and mineral rights.

As of July 1975, U.S. Forest Service and courthouse records show that approximately 25 percent of 

the land surface (fig. 14) is still privately owned.

MINERAL OWNERSHIP

After Federal purchase of lands within the national forest boundary, mineral rights were severed 

from most tracts and remain outstanding. Figure 15 

depicts Federal mineral ownership as of July 1975. 

Mineral rights on all other tracts remain in private 

ownership (table 1). After Federal purchase of 

these lands, the President's Reorganization Plan No. 

3 of 1946, Section 402, provided for the Bureau of 

Land Management to accept applications for prospecting and mining permits on acquired lands having federally owned mineral interests. Although representing a small part of the total acreage involved in 

the wilderness proposal, these Federal mineral lands 

have been accessible for exploration.

MINING ACTIVITY

No active mines are within the Sturgeon River 

Wilderness Study Area, and no record of past mineral 

production has been found. In a few places, minor 

amounts of sand and gravel from within the area have 

been used in the construction of logging roads. The
26 STURGEON RIVER WILDERNESS

R.35W. 88°4Q'

46°40

T.49N

46°35'

T.48N.

EXPLANATION

Federal surface ownership Area of report

0-51 2 3 4 KILOMETERS 

I WJ I . I

0 1/2 1 2 MILES

Figure 14. Federal surface ownership within the Sturgeon River Wilderness Study 

Area. Not all Federal ownership outside 

the area is shown.

V
STUDIES RELATED TO WILDERNESS 27

nearest mineral operations in recent times are small 

sand and gravel pits located in sees. 24 and 25, T. 

48 N., R. 35 W., approximately 2.4 km southeast of 

the study area. These pits appear to be worked intermittently to supply local needs.

PROSPECTING ACTIVITY

WITHIN THE AREA

No tangible evidence or record of exploration 

drilling and test pitting exists within the present 

study area. Several outcrops of basalt along Sturgeon River have been cored to a depth of several 

centimeters to obtain rock samples for paleomagnetic 

studies that will aid in regional stratigraphic correlation. The only other drilling of record is a 

water well drilled by the U.S. Forest Service in 

1964 at the Sturgeon River Campground (sec. 11, T. 

48 N., R. 35 W.). This well penetrated 10.3 m of 

gravel and boulders and 9.8 m of hard-rock ledge 

(Doonan and Byerlay, 1973). To our knowledge, a geologic description of the bedrock found in the water 

well is not available.

SILVER MOUNTAIN

The only physical evidence of prospecting activity in the immediate vicinity of the proposed 

wilderness is an adit and a trench located on Silver 

Mountain (fig. 16) . The prospects warrant mention 

because they are found in rock lithologically and 

stratigraphically similar to the basalt flows exposed along the Sturgeon River.

Attention may have first been directed to the 

study area by Hurt (1849, p. 849) , who described 

Silver Mountain (approximately 1.2 km west of the 

proposed wilderness boundary, on the east boundary 

of T. 49 N., R. 36 W., on the line between sees. 1 

and 6) as follows:

This mountain-like mass of greenstone 

trap is, to some extent, metalliferous; 

in nearly every part, traces of the gray
28 STUDIES RELATED TO WILDERNESS

R.35W. 88°40'

46°40' -

T.49N

46°35' -

T.48N.

EXPLANATION

Federal mineral ownership 

0 .5 1 2

Area of report

3 4 KILOMETERS

0 Vt 1 2 MILES

Figure 15. Federal mineral ownership within the Sturgeon River Wilderness Study 

Area. Not all Federal ownership outside 

the area is shown.
STURGEON RIVER WILDERNESS 29

TABLE I. Mineral ownership within and adjacent to the Sturgeon River Wilderness Study Area

T. 49 N., R.

Section Subdivision

5

6

6

7

8

8

9

15

15

16

16

16

17

18

18

18

20

21

22

22

23

26

27

28

28

29

31

31

32

32

32

32

33

34

34

35

Entire

WJj ME; WJj; Vft SE; SE SE

E% NE; NE SE

Entire

W% SW; SE SW; NW NE SW

Nij; SE%; NE NE SW; S3j

NE SW

Entire

NSj; 80s; NJj SW

SJj SW

NJj NE; NE NW

NW NW; SW SW

SE%; SJj NE; S% NW;

E% SW; NW SW

Entire

EJj NE; NW SE; NE SW

W% NE

NWJj; W% SW; SE SW; S%

SE; NE SE

Entire

Entire

EJj

WJj

Entire

Entire

Entire

WJj SE; WJj; SW NE

E3j SE; E% NE; NW NE

Entire

N%; SW3«; NW SE

&i SE; SW SE

EJj NE; NE SE

WJj NE; EJj NW; NW NW

SJj SW

SW NW; NJj SW; NW SE; S% SE

Entire

NE NE; Sh SE; SW NW; SW%

N% NW; SE NW; SJj NE;

NW NE; N% SE

Entire

35 W.

Owner

Ford Motor Co.

Worcester Lumber Co.

Ford Motor Co.

Ford Motor Co.

Worcester Lumber Co.

Federal

Ford Motor Co.

Michigan Iron and Land Co.

Unknown party

State of Michigan

Federal

Unknown party

Ford Motor Co.

State of Michigan

Federal

Ford Motor Co.

Ford Motor Co.

Ford Motor Co.

Federal

Michigan Iron and Land Co.

Michigan Iron and Land Co.

State of Michigan

Michigan Iron and Land Co.

Worcester Lumber Co.

Unknown party

Ford Motor Co.

Ford Motor Co.

Federal

State of Michigan

Ford Motor Co.

J. Van Evera

Federal

Ford Motor Co.

Federal

Michigan Iron and Land Co.

Michigan Iron and Land Co.
30 STUDIES RELATED TO WILDERNESS

TABLE 1. Mineral ownership within and adjacent to the Sturgeon River Wilderness Study Area Continued

T. 48 N. , R.

Section Subdivision

2

3

4

4

4

4

5

6

6

6

6

7

8

8

8

9

10

10

11

14

14

14

15

16

16

16

22

22

22

22

22

Entire

Entire

NE SW; N% SE; SE SE; S% NE

N% NE; NW?«

SW SE

8*5 SW; NW SW

Entire

SW NE; #5 NW; NW SW

SW SW

SE NE; NE SW

N^s NW; N*s NE; SE%; SE SW

Entire

N3j; N% SW

S% SW; N3$ SE; SW SE

SE SE

Entire

NJj NW; &} NE

Shi SJ$ NW; WJj NE

Entire

NW NW

S% NW; NE NW

E%; SW%

Entire

W%; W% NE; E*5 SE

E3s NE

W% SE

NJs NW

S3j NW; NW SW

E3s SW; SE%; SW NE; NE NE

NW NE; SE NE

SW SW

35 W.

Owner

State of Michigan

Michigan Iron and Land Co.

Federal

State of Michigan

Mary N. Bourke, and others

Von Platen

Ford Motor Co.

Joshua Stark, and others

Unknown party

Nester Lumber Co., and

others

State of Michigan

Ford Motor Co.

Nester Lumber Co., and

others

State of Michigan

Joshua Stark, and others

Ford Motor Co.

Mary N. Bourke, and others

Federal

Michigan Iron and Land Co.

Oliver Iron Mining Co.

State of Michigan

Federal

Ford Motor Co.

Federal

Mayme San born

State of Michigan

Sage Land and

Improvement Co.

Federal

State of Michigan

Oliver Iron Mining Co.

Unknown party
STURGEON RIVER WILDERNESS 31

sulphuret of copper were seen, but no 

well-defined and productive vein was 

found. On its southeasterly side two or 

three imperfectly formed veins of quartz 

and calcareous spar were seen associated 

with the gray sulphuret of copper; and in 

some places, with slight traces of green 

carbonate of steatite.

He then noted that the Sturgeon River passed over 

traprock in falls and rapids about 3 miles (5 km) 

south-southeast of Silver Mountain in T. 49 N., R. 

35 W.

R. 36 W. R. 35 W.

12

EXPLANATION

-1000- Topographic contour Contour 

interval, 50 ft (15m)

-c Adit

X Prospect trench 

== Forest Service road

0 TOO 200 300 400 METERS 

I I I I

500 1000 FEET

Figure 16. Location of the prospect adit and trench 

on Silver Mountain.
32 STUDIES RELATED TO WILDERNESS

Several other early investigators Foster and 

Whitney (1850), Wadsworth (1891), and Irving 

(1883) reported on the geology of Silver Mountain. 

Roberts (1940) , in his study of the Alston district, 

investigated Silver Mountain and, of more importance, described the rock outcrops along the Sturgeon River, the focal point of the present study.

Silver Mountain, formerly the site of a U.S. 

Forest Service lookout tower, is a dome-shaped mass 

of rock rising approximately 300 feet (91 m) above 

the surrounding terrain. Now designated on national 

forest maps as a "scenic view," it is reached by a 

gravel road leading off Forest Service Road 922. 

Just off the trail leading from a parking lot is the 

adit (fig. 16) . A Forest Service plaque notes that 

mining was carried on here by the National Co. prior 

to 1850.

The adit penetrates basalt for about 43 m along 

a fault plane, which has a bearing of about N. 70 

W. and dips 60 to the north. Fault breccia in 

fragments 2 to 30 cm in diameter (covered with talc) 

is visible in the trace exposed in the back. No 

significant mineralization was noted during this investigation, although Roberts (1940, p. 11) mentioned amygdules that carried traces of bornite and 

chalcopyrite. Foster and Whitney (1850, p. 68, 69) 

noted no metallic mineralization in the rock dump at 

the time of their investigation.

Sites of samples taken within the adit (nos. 

54-60) are shown in figure 17. The samples represent random chips taken every 5-10 cm through the 

fault zone in the roof and along the ribs over intervals indicated on figure 17. Sample analyses are 

tabulated in table 2. Very sparse mineralization is 

indicated by the results of the analyses; the highest copper value is 60 parts per million (ppm), and 

a trace of silver was found in the same sample. The 

water impounded in the rear of the adit precluded 

reaching the face for observation or sampling.

A small prospect trench is about 305 m northeast of the adit at an elevation of 329 m. First 

noted by Roberts (1940), it is presumed to have been 

opened by the same people who worked the adit. The 

trench lies within the same rock unit as the adit
STURGEON RIVER WILDERNESS 33

EXPLANATION rp

 I Sample interval and number 

0 Winze

Fault trace Showing dip. 

Dashed where inferred

Figure 17. Map and section of the Silver Mountain 

adit showing sample locations.

and has been excavated on a fault zone near the head 

of a narrow ravine that reflects the fault's trace. 

The workings are about 6.7 m long, 1.2 m wide, and 

1.8 m deep. Exposed in the face of the trench, the 

fault zone is about 1 m wide and has a strike of N. 

46° W. and a dip of 80 ° NE.

A chip sample of fault gouge and brecciated 

country rock was taken across the face. Assay results indicate a trace of silver and 90 ppm copper. 

Random chip samples from the ribs have lower copper 

values. The sparse mineralization indicated by the 

assay data negates the possibility of any economic 

value for the prospect.

HIGH-SILICA SAND

Evaluation of analyses for the Jacobsville 

Sandstone (table 2) indicates that high aluminum, 

iron, magnesium, and titanium negate the possibility 

of this sandstone being considered a source of 

high-silica sand. Whether or not more pure sandstone underlies the glacial material in the area 

could not be determined, but examination of the few 

outcrops suggests that it does not. Because they 

lack maturity, glacial deposits in the area are not 

considered likely sources of high-silica sand.
TABLE 2. Partial chemical analyses of samples from the Sturgeon R

[Results in parts per million, except as indicated; N.a., not analyzed; N.d., not dete

limit of quantitative determination. Samples 1-49 were analyzed at U.S. Geologic

Au was determined by combined fire assay-atomic absorption technique. Rema

semiquantitative spectrographic technique for which the standard deviation of a

-33 percent. Si, Al, Fe, Mg, Ca, Na, K, Ti, P, B, Ba, Bi, Cd, Ce, Dy, Er, Eu, Ga, G

Rh, Ru, Sb, Sc, Sm, Sr, Ta, Tb, Te, Th, Tl, Tm, W, Y, and Yb were analyzed but 

lous amounts. Samples 51-82 were analyzed by U.S. Bureau of Mines, Reno Met

Sc, Mo, Ni, Pb, V, Zr analyzed by general spectrographic technique. Cu also by 

detected, are As, Au, I

Number

Soil samples 12

13

14

15

16

17

18

19

33

34

35

39

42

44

47

Stream sediment

samples 26

28

29

3a, Be, ]

Ag'

0.12

<.10

<.10

<.10

.12

.35

<.10

<.10

<.10

<.10

<.10

.14

<.10

<.10

<.10

<.46

<.46

<.46

Bi, Cd,

Au

0.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<-05

<.05

<.05

<.05

<.05

<.05

Ga, Hf , ]

Co

4.3

4.3

5.6

4.7

t 3.7

320

11

6.5

4.7

4.5

8.0

3.9

6.8

5.1

4.9

3.6

3.7

5.5

[n, Li,

Cr

16

15

26

19

15

15

48

24

19

15

27

20

26

43

23

32

29

67

, La, Y, Nb, P,

Cu Hf

14 < 100

9. 4 < 100

14 < 100

9. 5 < 100

8.2<100

8. 4 < 100

26 < 100

17 < 100

11 < 100

47 < 100

9.8<100

9.6<100

19 < 100

17 < 100

11 < 100

6.9 <21

4.0 <21

6.4 <21

Pt, Re, Sb, Sr

Mn Mo

260 <2.2

350 <2.2

370 <2.2

330 <2.2

220 <2.2

290 <2.2

420 <2.2

470 <2.4

340 <2.2

340 <2.2

260 <2.2

250 <2.2

360 <2.2

410 <2.2

340 < 2.2

540 < 2.2

360 < 2.2

670 <2.2

i, S

1

2

1

1

1

1
31

37

40

46

49

Pan concentrate

samples 34

20

25

27

30

36

41

43

45

48

71

73

78

Rock samples:

Basalt 289

51

52

53

54

55

56

57

58

59

60

<.46

<.46

<.46

<.46

<.46

<.46

<.46

<.46

<.46

.54

.58

<.46

<.46

<.46

.51

1.1

Tr

N.d.

N.d.

<.10

.28

<.10

Tr

N.d.

N.d.

.1

N.d.

Tr

N.d.

N.d.

N.d.

N.d.

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

N.d.

N.d.

N.d.

<.05

<.05

<.05

N.d. 

N.a. 

N.a. 

N.d. 

N.d. 

N.d. 

N.d.

N.a. 

N.d.

N.a.

3.0

1.6

2.4

4.2

3.4

15

16

19

4.9

27

22

4.6

2.2

20

16

31

N.d.

N.d.

N.d.

31

25

37

<10

< 10

<10

< 10

<10

<10

< 10

< 10

<10

< 10

41

30

24

35

35

96

170

130

25

450

380

44

62

240

170

530

70

70

100

280

200

140

<30

<30

60

<30

<30

30

<30

<30

<30

<30

3.5

1.6

2.9

5.6

4.7

9.1

14

30

2.3

21

14

1.2

< 1.0

17

11

22

40

30

30

92

130

92

90

40

40

40

40

60

40

<20

40

40

<46

<22

<22

< 22

< 22

<100

<22

<22

<22

220

<22

<46

<22

<22

<22

<22

N.d.

N.d.

N.d.

<100

<100

<100

N.d.

N.d.

N.d.

N.d.

N.d.

N.d.

N.d.

N.d.

N.d.

N.d.

320 < 2.2

170 <2.2

270 < 2.2

330 < 2.2

340 < 2.2

2,500 <2.2

4,400 <3.2

1,500 <2.2

530 <2.2

5,300 3.0

5,600 <4.6

1,000 <2.2

470 <2.2

8,200 <2.2

2,300 <3.2

5,800 <4.6

2, 000 < 20

2,000<20

2, 000 < 20

1,800 <3.2

1,500 <2.2

2,500 <3.2

300 N.d.

300 N.d.

600 N.d.

600 N.d.

600 N.d.

600 N.d.

300 N.d.

300 N.d.

300 N.d.

14,000 N.d.

3

3

5

5

4

3

3

5

N

N

N

6

9

6

<2

< 2

<2

<2

<2

<2

<2

<2

<2

<2
TABLE 2. Partial chemical analyses of samples from the Sturgeon River 

Rock samples:

Basalt

Diabase

Sandstone

Quartzite

Number

64

66

69

80

81

1

5

10

11

23

61

62

63

65

67

68 <

70

82

Ag 1

N.d.

N.d.

N.d.

N.d.

< .10

< .10

< .10

<.10

< .10

< .10

N.d.

N.d.

N.d.

N.d.

N.d.

:io

N.d.

N.d.

Au

N.a. <

N.a. <

N.a. <

N.a. <

N.a. <

<.05

<.05

<.05

<.05

<.05

N.a. <

N.a. «

N.a. «

N.a. «

N.a. «

N.a. «

N.a. «

N.a. -

Co Cr

: 10 < 30

: 10 < 30

; 10 60

; 10 < 30

C 10 < 30

3.8 5.6

5.6 29

4.6 22

6.2 19

6.2 19

CIO <30

C 10 < 30

CIO <30

C 10 < 30

C 10 < 30

C 10 < 30

C 10 < 30

CIO 30

Cu

40

40

N.a.

460

490

8.

16

12

11

11

30

30

30

20

20

<20

20

40

Hf

N.d.

N.d.

N.d.

N.a.

N.a.

3<100

<100

<100

<100

<100

N.a.

N.a.

N.a.

N.a.

N.a.

N.a.

N.a.

N.a.

Mn

600

600

14,000

14,000

14,000

1,400

200

330

280

280

300

300

300

300

140

140

60

140

Mo

N.d.

N.d.

N.d.

N.d.

N.d.

<2.2

<2.2.

<2.2

<2.2

<2.2

N.d.

N.d.

N.d.

N.d.

N.d.

N.d.

N.d.

N.d.

N

<20

< 2

<20

<20

2

1

1

1

1

< 2

N

< 2

< 2

< 2

< 2

N

< 

'Values for numbers 51 to end of table are given to oz/ton. 

'High value due to contamination during sample preparation.
STURGEON RIVER WILDERNESS 37

STONE

Before the turn of the century, the Jacobsville 

Sandstone was quarried as dimension stone at the 

town of L'Anse, approximately 23 km northeast of the 

Sturgeon River area, and at several other localities 

near the Lake Superior shore (Kirby, 1964).

Jacobsville Sandstone in the study area would 

not be suited to quarry development even if there 

were sufficient market demand. The distance to major market areas, the vast quantities of overburden, 

as well as the lack of electrical power and access 

roads, preclude economic development and limit the 

potential of the sandstone.

Basalt of the Siemens Creek Formation within 

the study area is a minor resource of crushed stone 

and riprap. The distance to markets, the limited 

areal extent of the outcrops, and extensive overburden, plus the lack of electrical power and access 

roads, limit the possibility of economic development. The basalt at nearby Silver Mountain represents a more likely source of a very large quantity 

of stone, and a developed access road is nearby.

SAND AND GRAVEL

Sand and gravel is found in the extensive glacial deposits that blanket the study area. Deposits 

range from 0 to about 30 m in thickness in cutbanks 

along the Sturgeon River. On the basis of topographic mapping, sand and gravel in thicknesses of 

more than 61 m is estimated to be present in some 

areas.

Moraine deposits of till, lake-plain and 

stream-bench deposits of sand and clay, and outwash 

deposits of stratified sand and gravel are present 

(Doonan and Byerlay, 1973). In this heavily vegetated area, characteristics of individual deposits 

are visible mainly in stream drainages. Observations indicate that many deposits are composed of 

fine sand with interbedded silt and clay, which are 

a deterrent to commercial development.
38 STUDIES RELATED TO WILDERNESS

Coarse water-washed gravel and sand and numerous boulders are found in the Sturgeon River channel 

and along bars from a point where the river enters 

the study area in sec. 11 to the south line of sec. 

3, T. 48 N., R. 35 W. The distance from major demand centers and the high transportation costs effectively limit commercial utilization of these deposits. Because most of the surrounding area is 

national forest land, local demand is unlikely.

CLAY

Deposits of clay within the study area are 

mainly visible in stream drainages (fig. 18). The 

areal extent of most exposures is only a few meters. In several instances, deposits are overlain 

by glacial sand and gravel in excess of 15 m. The 

clay is red or tan, somewhat gritty, and locally interspersed with small pebbles.

Samples were collected during this investigation to evaluate the ceramic properties of the clay 

(table 3). Only clay sample No. 72 (table 3) shows 

any potential for use as a moderate-weather building 

brick. All other samples were found not suitable 

for use in vitreous clay products.

Limited areal extent of the deposits, poor 

quality, thickness of overburden, distance to markets, and lack of accessibility negate the possibility of their economic development.

PEAT

Minor resources of peat are found in swampy 

lowlands within the study area, for the most part in 

the SW% sec. 32, T. 49 N., R. 35 W., and the NEftj 

sec. 6, T. 48 N., R. 35 W. Because of the lack of 

local demand and distance to major markets, it is 

unlikely that the deposits will be commercially significant.
STURGEON RIVER WILDERNESS 39

 anHMgfH* ;'X;***

*Mfc..

u t

Figure 18. Exposure of Pleistocene glacial 

deposits in a stream bank along Sidnaw 

Creek in southwestern part of study area. 

A clay bed (darker massive-appearing material near center) is overlain and underlain 

by stratified sand.
TABLE 3. Evaluation of glacial clay sam

[All data presented here are based on laboratory tests that are preliminary in nature 

Slow firing te

Sample TemperSample interval , ature 

Number (feet) Raw properties (OF)

72 2.5 Water of plasticity:

Working properties:

Drying shrinkage: 5.

pH: 7.3

20.8 percent

short

,0 percent

No effervescence with HC1

74 6.0 Water of plasticity:

Working' properties:

Drying shrinkage: 5.

pH: 7.7

Slight effervescence

75 4.0 Water of plasticity:

Working properties:

Drying shrinkage: 2.

pH: 8.0

Slight effervescence

20.5 percent

plastic

. 0 percent

with HC1

22.2 percent

plastic

. 5 percent

with HC1

1800

1900

2000

2100

2200*

2300

1800

1900

2000

2100*

2200

2300

1800

1900

2000

2100*

2200

2300

 5

5

2.

2.

2.

5

5

7.

7.

5

5

2.

5

Munsell Moh's 

color hardness

YR 7/6

YR 7/6

,5 YR 6/8

,5 YR 5/6

,5 YR 3/2

 

YR 8/2

YR 8/2

,5 YR 8/4

.5 YR 6/4

 

 

YR 3/4

YR 8/4

, 5 YR 7/4

YR 4/2

 

 

2

2

3

4

7

-

3

3

3

8

-

-

2

2

3

6

-

-

Total 

shrinkage 

(percent)

5.0

5.0

5.0

5.0

12.5

Melted

5.0

5.0

5.0

10.0

Melted

 

5.0

5.0

5.0

12.5

Melted

 
76 7.5 Water of plasticity:

Working properties:

Drying shrinkage: 5.

pH: 7.8

Slight effervescence

77 6.3 Water of plasticity:

Working properties:

Drying shrinkage: 5,

pH: 8.1

Slight effervescence

79 4.0 Water of plasticity:

Working properties:

Drying shrinkage: 5,

pH: 8.2

Slight effervescence

21.0 percent

plastic

.0 percent

with HC1

20.4 percent

plastic

.0 percent

with HC1

17.2 percent

plastic

.0 percent

with HCl

1800

1900

2000

2100*

2200

2300

1800

1900

2000

2100*

2200

2300

1800

1900

2000

2100*

2200

2300

5

5

2

5

2

2

2

2

2

2

2

5

YR 8/4

YR 8/4

.5 YR 7/4

YR 5/4

 

.5 YR 7/6

.5 YR 7/6

.5 YR 6/6

.5 YR 4/2

 

 

. 5 YR 7/6

.5 YR 7/6

.5 YR 6/8

YR 4/4

 

2

2

3

7

-

-

3

3

3

7

-

-

2

2

3

6

-

"

5.0

5.0

5.0

10.0

Melted

---

5.0

5.0

5.0

10.0

Melted

5.0

5.0

5.0

5.0

Melted

t To convert sample interval to meters, multiply footage by 0.3048.

',' Tests indicate the following for all samples: Drying defects - none; Dry strength - good; Bloat

Asterisk indicates abrupt vitrification prior to reaching temperature noted.
42 STUDIES RELATED TO WILDERNESS

POTENTIAL FOR UNDISCOVERED MINERAL DEPOSITS

By W. F. Cannon, James J. Hill, and Peter C. Mory

The probability that undiscovered mineral deposits exist in the study area was evaluated in two 

ways: by geologic environment and by geochemical 

surveys. Ore deposits are commonly associated with 

a characteristic geologic environment. By comparing 

the geologic environments in the study area with 

those containing known mineral deposits elsewhere, 

it was possible to estimate what, if any,v types of 

ore deposits could occur in the area. The potential 

for mineral deposits can sometimes be assessed more 

directly by geochemical surveys. Ore deposits, even 

though buried, commonly cause anomalous metal content in soil developed over them, in bedrock in a 

halo around them, or in sediments in streams flowing 

across the mineralized area.

On the basis of these methods of evaluation, 

the area has a low probability for undiscovered mineral deposits.

ASSESSMENT BY GEOLOGIC ENVIRONMENT

Mineral commodities that have been produced in 

major quantities in nearby areas include iron from 

middle Precambrian iron-formations, copper from middle Keweenawan basalt and interbedded sedimentary 

rocks and from upper Keweenawan shale, and lesser 

amounts of gold from gold-bearing quartz veins. Also, several small deposits of uranium-rich rocks 

have been found east of the area, and uranium exploration is currently very active in much of the 

Upper Peninsula.

MICHIGAMME FORMATION

If the Michigamme Formation in the study area 

is a graywacke-slate sequence, as inferred from 

aeromagnetic data, the potential for mineral depos-
STURGEON RIVER WILDERNESS 43

its in it is very low. Such sequences, which accumulate rapidly in deep marine basins, are generally 

barren of metal concentrations. This is certainly 

true in the Upper Peninsula. The graywacke-slate 

sequence of the Michigamme is extensively exposed 

south and east of the study area and is virtually 

devoid of mineralization. The stratigraphically 

lower part of the Michigamme Formation, east of the 

study area, contains iron-formation from which iron 

was produced in the past. That iron-formation, 

along with surrounding pyritic black slate, is the 

site of considerable uranium exploration activity. 

If these units underlie the study area, they are 

probably so deep below the graywacke-slate sequence 

that exploration is not feasible. Outcrops of the 

Michigamme Formation nearest the study area have 

been field checked with a scintillometer and checked 

in the laboratory by a uranium scan. They are not 

anomalously uraniferous.

BASALT AND DIBASE DIKES

Basalt and diabase, in general, are not favorable host rocks for ore deposits, but the Keweenawan 

basalts of Michigan are an exception. Extensive deposits of native copper and associated silver have 

been mined from middle Keweenawan basalt and interbedded sedimentary rocks north and west of the study 

area. In spite of this, the basalt in the study 

area is not considered favorable for copper deposits. All economic copper deposits are in middle Keweenawan rocks, whereas the basalt in the study area 

is undoubtedly lower Keweenawan as indicated by magnetic studies. Important copper mineralization is 

unknown in lower Keweenawan basalt or related diabase.

JACOBSVILLE SANDSTONE

The Jacobsville Sandstone has been studied 

widely in the Upper Peninsula (for instance, Hamblin, 1958), and no mineralization has been report-
44 STUDIES RELATED TO WILDERNESS

ed. Its barren nature elsewhere indicates little 

likelihood that it would contain mineralization in 

the study area.

GLACIAL DEPOSITS

The only possible occurrence of metallic minerals in the glacial deposits is as heavy mineral 

placer concentrates. The stratified, probably fluvial, nature of much of the glacial material indicates that placer concentration is possible, but the 

geochemical data discussed next show no indication 

that such deposits exist in the wilderness study 

area.

Deposits of nonmetallic materials, such as 

clay, peat, and sand and gravel, are abundant and 

have not been thoroughly explored or measured in 

this study. The poor ceramic quality of the known 

clay beds suggests that undiscovered clay beds are 

likewise of poor quality. Peat is likely to occur 

in marshy areas, particulary in the southwest part 

of the study area. Most marshes, however, are small 

and far from potential markets, suggesting that no 

important undiscovered peat resources are in the 

area. The area contains vast quantities of sand and 

gravel, but the abundance of similar material 

throughout the region, much of it closer to points 

of use, negates any large economic potential for 

sand and gravel in the study area.

ASSESSMENT BY GEOCHEMICAL SURVEY

A geochemical survey of the study area used 

three sample media: bedrock, soil developed on glacial deposits, and stream sediments consisting of 

both pan concentrates and grab samples. None of 

these showed highly anomalous compositions, and no 

suggestion of buried ore deposits was found. A partial listing of analyses is in table 2.

SOIL SAMPLES

Soil samples were collected from 15 localities, 

mostly on uplands near the margin of the study
STURGEON RIVER WILDERNESS 45

area. All samples were taken from soils developed 

on thick glacial deposits where the soil profile 

consisted of 1-2 cm of organic material at the surface and 10-20 cm of light-gray sandy soil over reddish-brown sand. Most samples were taken from 

depths 30-40 cm below the surface.

Because of the porous nature of the glacial deposits and their great thickness, it is unlikely 

that a mineral deposit beneath the deposits or in 

the deposits themselves would be detected in the 

soil. Except in areas of clay beds, ground water 

percolates freely downward, and there is no mechanism by which metals in anomalous concentrations 

could diffuse upward to the soil zone. The soil 

samples were intended to provide background values 

against which stream sediment samples could be compared. The results of the analyses are shown in table 2. No anomalously high values were found.

STREAM SEDIMENTS

Eight grab samples of stream sediments and 11 

heavy-mineral concentrates panned from the sediments 

were collected and analyzed. Sample sites were chosen along the Sturgeon River and on all major tributaries so that each individual drainage system was 

sampled. The stream sediments of tributaries are 

derived totally from glacial deposits, whereas those 

in the Sturgeon River, although derived principally 

from glacial deposits, also have a component introduced from upstream parts of the river outside of 

the study area. Any concentration of metals in the 

glacial deposits should cause higher concentrations 

in the stream sediments than were measured in soil 

from the adjacent uplands.

Certain elements, such as Cu, Hf, Pb, Zn, Zr, 

and Ti, showed predictably higher concentrations in 

heavy-mineral concentrates than in either grab samples of stream sediments or soil samples (see table 

4) . This reflects only that these elements are contained in heavy minerals. According to visual estimates, heavy minerals generally are less than 1 perdent of the stream sediments. Comparison of analyses of pan concentrates with those of grab samples
46 STUDIES RELATED TO WILDERNESS

TABLE 4. Comparison of analyses of some stream sediments and heavy -

mineral pan concentrates

[N.d., not detected]

Element

Cu

Hf

Pb

Zn

Zr

TiO

2

Cu

Hf

Pb

Zn

Zr

TiOi

Cu

Hf

Pb

Zn

Zr

TiO

s

Range

(ppm)

Pan concentrates

(11 samples)

<1-30

<21-220

8.5-100

<15-270

136- >2, 100

13,000-87,000

Stream sediments

(8 samples)

1.5-6.9

<21-<47

1.5- 9.9

all<15

120-480

5,000-13,000

Soil

(15 samples)

3.2-13.1

N.d.

4.8-15

<15-21

81-634

4,400-10,000

Median

(ppm)

14

<21

29

110

>2,100

37,000

4

<21

14

<15

210

8,000

5

N.d.

10

<15

230

7,000
STURGEON RIVER WILDERNESS 47

collected at the same site shows no anomalous values 

in the sediments for those elements having very high 

values in the pan concentrates.

Thus, no evidence of metal concentrates that 

approach economic grade or size was found in the 

glacial deposits.

Two pan concentrates had slightly anomalous tin 

content (45 and 52 ppm). One of the samples (20) 

was collected from the point where the Sturgeon River enters the study area; thus, small amounts of tin 

are apparently being carried into the area from some 

point upstream. The other sample (49) , collected 

from the Sturgeon River near the mouth of Funks 

Creek, also had slightly anomalous silver (1.5 ppm) 

and arsenic (210 ppm) values, for which there is no 

obvious source in the study area.

BEDROCK

Seven samples of basalt from the Siemens Creek 

Formation and 13 samples of the Jacobsville Sandstone were analyzed for anomalous metal content. In 

addition, two samples of lower Keweenawan diabase 

dikes and one sample of graywacke from the Michigamme Formation outside the study area were analyzed.

No unusual concentrations of metals were found 

in any samples except for the diabase dikes (80 and 

81 in table 2) , which contain 460 and 490 ppm copper. In outcrops, these rocks show no unusual concentrations of minerals that are likely to bear copper, and no explanation for the high copper content 

is apparent. Although these values are considerably 

higher than the typical copper content of diabase 

(150 ppm) t they are not economic concentrations. 

Because no higher grade copper concentrations have 

been found here or in any other similar diabase 

throughout a large surrounding region, these values 

are probably not associated with economically important mineralization.
48 STUDIES RELATED TO WILDERNESS

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STURGEON RIVER WILDERNESS 49

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529-541.

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£U.S. GOVERNMENT PRINTING OFFICE: 1980 O 311-344/156