Mineral Resources of the

North Pole Ridge Wilderness Study Area,

Sherman and Gilliarn Counties, Oregon

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Chapter B

Mineral Resources of the

North Pole Ridge Wilderness Study Area,

Sherman and Gilliam Counties, Oregon

By SCOTT A. MINOR, JAY A. ACH, JAMES G. FRISKEN, and 

RICHARD J. BLAKELY 

U.S. Geological Survey

HARRY W. CAMPBELL 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1743

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

JOHN DAY REGION, OREGON
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade names and trademarks 

in this publication is for descriptive 

purposes only and does not constitute 

endorsement by the U.S. Geological Survey

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For sale by the

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Library of Congress Cataloging-in-Publication Data

Mineral resources of the North Pole Ridge Wilderness 

Study Area, Sherman and Cilliam Counties, Oregon.

(Mineral resources of wilderness study areas John Day 

region, Oregon ; ch. B) (U.S. Geological Survey bulletin ; 

1743-B)

Bibliography: p.

Supt. of Docs, no.: I 19.3:1743-8

1. Mines and mineral resources Oregon North Pole 

Ridge Wilderness. 2. North Pole Ridge Wilderness (Or.) I. 

Minor, Scott A. II. Series. III. Series: U.S. Geological 

Survey bulletin ; 1743-B.

QE75.B9 no. 1743-B 557.3 s 88-600275 

[TN24.07] [553'.09795'64]
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Area

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 1976) requires the 

U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys on certain areas to 

determine the mineral values, if any, that may be present. Results must be made available to the public 

and submitted to the President and the Congress. This report presents the results of a mineral survey of 

part of the North Pole Ridge Wilderness Study Area (OR-005-008), Sherman and Gilliam Counties, 

Oregon.

CONTENTS

Summary Bl

Abstract Bl

Character and setting Bl

Identified resources Bl

Mineral resource potential B2 

Introduction B3

Location and physiography B3

Previous and present investigations B3

Acknowledgments B5 

Appraisal of identified resources B5

Mining history B5

Appraisal of mineral resources B5 

Assessment of mineral resource potential B6

Geology B6

Geochemical studies B7

Geophysical studies B9

Mineral and energy resource potential B9 

References cited Bll 

Appendixes

Definition of levels of mineral resource potential and certainty of assessment B16

Resource/reserve classification B17

Geologic time chart B18

FIGURES

1. Index map showing location of North Pole Ridge Wilderness Study Area, Sherman and Gilliam 

Counties, Oregon B2

2. Map showing generalized geology, mineral resource potential, and location of claim group in North 

Pole Ridge Wilderness Study Area, Sherman and Gilliam Counties, Oregon B4

Contents

Mineral Resources of the

North Pole Ridge Wilderness Study Area,

Sherman and Gilliam Counties, Oregon

By Scott A. Minor, Jay A. Ach, James G. Frisken, and 

Richard J. Blakely 

U.S. Geological Survey

Harry W. Campbell 

U.S. Bureau of Mines

SUMMARY

Abstract

At the request of the U.S. Bureau of Land Management, 

5,830 acres of the North Pole Ridge Wilderness Study Area 

(OR-005-008) in Sherman and Gilliam Counties, north-central Oregon, were evaluated for identified mineral resources 

(known) and mineral resource potential (undiscovered). 

Throughout this report, "wilderness study area" and "study 

area" refer to those acres for which mineral surveys were 

requested. Fieldwork for this report was carried out from 

1985 through 1987. No mines or mining districts are located 

inside the study area; however, 11 active (1986) gold claims 

are in the study area, and the study area is under lease for oil 

and gas. The study area has no identified mineral resources. 

The eastern part of the study area has moderate potential and 

the rest of the area has low potential for gold resources in 

small epithermal deposits. Along the John Day River there is 

low potential for gold resources in small placer deposits. The 

entire study area has low potential for oil and gas and no 

potential for geothermal energy resources.

Character and Setting

The North Pole Ridge Wilderness Study Area is located on the Deschutes-Umatilla plateau of north-central 

Oregon (fig. 1), about 45 mi southeast of The Dalles, Oreg. 

The terrain is dominated by the precipitous, 1,500-ft-deep 

canyon entrenched by the meandering John Day River.

Manuscript approved for publication, June 21, 1988.

Segments of several prominent tributary canyons are also 

present in the study area. Bedrock in the study area consists of Miocene (see appendixes for geologic time chart) 

basalt flows of the Columbia River Basalt Group (fig. 2) 

that are predominantly gently tilted toward the north. Older 

Paleogene volcanic and sedimentary rocks and Mesozoic 

sedimentary rocks are exposed just south of the study area 

and probably extend underneath the study area at shallow 

depths. A north-trending zone of normal faulting, folding, 

and related deformation that crosses the eastern part of the 

study area terminates a regional, gentle, east-trending fold 

structure located east of the zone (fig. 2). The study area 

contains alluvium-mantled meander scars perched as much 

as 600 ft above river level in the John Day River canyon. 

Massive landslide deposits and recent and active alluvium 

conceal much of the bedrock in the deeper parts of the John 

Day River canyon.

Identified Resources

No mineral resources were identified in the North Pole 

Ridge Wilderness Study Area. The Micron claim group 

(11 claims), located in the southern part of the study area 

(fig. 2), was staked at the site of a previously reported geochemical anomaly of gold. No gold or other mineral resources were identified on these claims.

Stone, sand, and gravel from the study area could be 

quarried and used for construction purposes; however, 

suitable material is common in the region and more accessible to potential markets.

Mineral Resources of the North Pole Ridge Wilderness Study Area, Oregon B1
Mineral Resource Potential

The North Pole Ridge Wilderness Study Area has

study area has low energy resource potential for oil and gas 

and no potential for geothermal energy.

Spotty, locally strong gold and gold-pathfinder geomoderate and low resource potential for gold in epithermal chemical anomalies have been detected primarily in the 

deposits and low resource potential for placer gold. The eastern part of the study area in the general area of a group

120°30' 120°15'

APPROXIMATE BOUNDARY OF 

LOWER JOHN DAY 

97 1 WILDERNESS STUDY AREA 

(OR-005-006)

APPROXIMATE BOUNDARY OF

THIRTYMILE 

WILDERNESS STUDY AREA

(OR-005-001)

[_ SHERMANI CO _ 

WASCO/CO

GILLIAM CO 

WHEELER CO

APPROXIMATE BOUNDARY

OF

NORTH POLE RIDGE

WILDERNESS STUDY AREA

(OR-005-008)

Petroleum-test drill holes '

» \

Burgess »

WASCOCQ 

JEFFERSON CO

Ashwood-Horse Heaven 

mining districts

Figure 1. Index map showing location of North Pole Ridge Wilderness Study Area, Sherman and Gilliam Counties, Oregon. 

Locations of Lower John Day and Thirtymile Wilderness Study Areas shown for reference purposes.

B2 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
of active gold claims. No obvious hydrothermally altered 

or mineralized rocks occur there or elsewhere in the study 

area. Most of the geochemical anomalies are within or near 

a north-trending zone of folding, fracturing and high angle 

faulting that may have provided localized conduits for 

auriferous hydrothermal fluids leaking from concealed 

mineralized rocks. There is moderate resource potential for 

gold in small epithermal deposits in the eastern part of the 

study area that contains the north-trending zone of deformation, active gold claims, and most of the geochemical 

anomalies (fig. 2). The surrounding parts of the study area, 

which contain scattered, weak gold-related anomalies, have 

low potential for gold resources in epithermal deposits.

Stream-sediment, stream-sediment-concentrate, and 

alluvial (placer) samples collected in the study area indicate 

the presence of small amounts of placer gold in John Day 

River alluvium. There is a remote possibility that undiscovered, more concentrated deposits of placer gold lie 

concealed within active, recent, and (or) older perched 

alluvium in the John Day River canyon. The deeper parts 

of the John Day River canyon in the study area have low 

potential for gold resources in small placer deposits (fig. 2).

The entire study area has low potential for energy 

resources of oil and gas. Four petroleum test holes, all of 

which were essentially dry, have been drilled as close as 13 

mi from the study area. Rocks that underlie Columbia 

River basalts were encountered in the drill holes but do not 

appear to be suitable source or reservoir rocks for hydrocarbons, even though some of these lower rocks have been 

determined to be thermally mature. Although similar unfavorable basement rocks probably extend underneath the 

study area, the existence of promising source or reservoir 

rocks cannot be completely ruled out.

The study area lies in an area of relatively low heat 

flow that lacks hot or warm springs, and thus the area has 

no potential for geothermal energy resources.

INTRODUCTION

This mineral survey was requested by the U.S. Bureau 

of Land Management and is the result of a cooperative 

effort by the U.S. Geological Survey and the U.S. Bureau 

of Mines. An introduction to the wilderness review process, mineral survey methods, and agency responsibilities 

was provided by Beikman and others (1983). The U.S. 

Bureau of Mines evaluates identified resources at individual mines and known mineralized areas by collecting data 

on current and past mining activities and through field 

examination of mines, prospects, claims, and mineralized 

areas. Identified resources are classified according to a 

system that is a modification of that described by McKelvey (1972) and U.S. Bureau of Mines and U.S. Geological Survey (1980). Studies by the U.S. Geological Survey 

are designed to provide a reasonable scientific basis for

assessing the potential for undiscovered mineral resources 

by determining geologic units and structures, possible 

environments of mineral deposition, presence of geochemical and geophysical anomalies, and applicable ore-deposit 

models. Goudarzi (1984) discussed mineral assessment 

methodology and terminology as they apply to these surveys. See appendixes for the definition of levels of mineral 

resource potential and certainty of assessment and for the 

resource/reserve classification.

Location and Physiography

The North Pole Ridge Wilderness Study Area consists 

of 5,830 acres and is located on the Deschutes-Umatilla 

plateau of north-central Oregon in Sherman and Gilliam 

Counties (fig. 1), about 45 mi southeast of The Dalles, 

Oreg. The Deschutes-Umatilla plateau forms part of the 

extensive Columbia Plateau physiographic province that 

also includes much of eastern Washington and parts of 

western Idaho. The Thirtymile (OR-005-001) and the 

contiguous Lower John Day (OR-005-006) Wilderness 

Study Areas (Ach and others, 1988) are located 2 mi and 7 

mi north, respectively, of the study area.

The study area contains a 6.5-mi stretch of the meandering lower John Day River (fig. 1). The John Day River, 

which drains into the Columbia River 40 mi to the north, 

has entrenched a deep, precipitous, winding canyon into the 

Deschutes-Umatilla plateau in the vicinity of the study 

area. The terrain in the study area consists mainly of the 

sinuous John Day River canyon, which has an average 

depth of about 1,500 ft. Elevations in the study area range 

from about 2,920 ft above sea level on Horse Mountain 

along the south border to 1,020 ft where the John Day 

River crosses the northeast border (fig. 2). Several tributary streams that drain into the river, including those occupying Big Gulch and Pete Enyart Canyon (fig. 2), are intermittent, reflecting the semiarid climate of the region. 

Juniper trees, low-lying sage and other brush, and seasonal 

varieties of grasses and wildflowers grow locally in the 

study area. The larger stream channels and banks of the 

John Day River support a variety of riparian vegetation.

The most direct access into the study area is down the 

John Day River by raft from Clarno 12 mi south of the 

study area (fig. 1). Several jeep and hiking trails extend to 

the edge of the study area from county roads to the west 

and east.

Previous and Present Investigations

Few investigations have been made in the vicinity of 

the study area. The earliest published geologic map of the 

region (Newcomb, 1970) was reconnaissance in nature 

(1:500,000 scale), addressing the tectonic structure of the

Mineral Resources of the North Pole Ridge Wilderness Study Area, Oregon B3
120°30' 120°27'30"

APPROXIMATE BOUNDARY

OF

NORTH POLE RIDGE

WILDERNESS STUDY AREA

(OR-005-008)

L/BO.G 

(entire study area)

L/B Au [1] 

L/C Au [21 M/B Au[l] 

L/C Au [2]

EXPLANATION

fcilQ?] l^rea having moderate mineral or energy resource potential (M) 

[ | Area having low mineral resource potential (L)

Levels of certainty of assessment 

B Data only suggest level of potential 

C Data give good indication of level of potential

Commodities

Au Gold

O,G Oil and Gas

[ ] Deposit types

Epithermal deposits of gold 

Placer deposits of gold

Geologic map units

Qal Alluvium (Quaternary)

Qls Landslide deposits (Quaternary)

Tcr Columbia River Basalt Group (Tertiary)

Tjd John Day Formation (Tertiary)

Contact Dashed where approximate

Fault Dashed where approximate, dotted where concealed. 

Bar and ball on apparent downthrown side; doubleheaded arrows indicate uncertain sense of strike-slip 

displacement

Syncline Dashed where approximate. Large arrow points in 

direction of plunge

Anticlinal bend Dashed where approximate; dotted where 

concealed. Bar and ball on apparent downthrown side 

where accompanied by inferred normal fault

Figure 2. Generalized geology, mineral resource potential, and location of claim group in North Pole Ridge 

Wilderness Study Area, Sherman and Gilliam Counties, Oregon.

B4 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
Columbia River basalts. Swanson and others (1981), using 

established stratigraphic nomenclature for the Columbia 

River basalts (Swanson and others, 1979), mapped the 

geology of the Columbia River basalts in northern Oregon 

and western Idaho at a scale of 1:250,000. Bela (1982) 

compiled a geologic map of the The Dalles 1° by 2° sheet 

chiefly from the mapping of Swanson and others (1981). 

The U.S. Bureau of Land Management prepared a geology, 

energy, and mineral (GEM) resources report on the Lower 

John Day Resource Area, which includes this study area 

(Davis, 1983). The petroleum potential of Oregon wilderness study areas, including this one, was evaluated by 

Fouch (1983).

The U.S. Geological Survey visited the study area 

during the 1985, 1986, and 1987 field seasons. Fieldwork 

included geochemical sampling and checking of existing 

geologic mapping supplemented, locally, by additional 

mapping. Gravity, aeromagnetic, and aerial gamma-ray 

data covering the study area were compiled and interpreted. 

Geochemical analyses were obtained for 1 water, 15 

stream-sediment, 21 stream-sediment-concentrate, and 35 

rock samples collected in the study area.

The U.S. Bureau of Mines conducted a library search 

for information on mines and prospects in and near the 

study area. This search included checking U.S. Bureau of 

Land Management mining claim recordation indices, GilHam and Sherman County mining claim records, and the 

U.S. Bureau of Mines Mineral Industry Location System. 

Field studies by U.S. Bureau of Mines personnel were 

conducted in 1986. Active claims in the study area were 

examined, and 11 rock samples were collected from the 

claims for geochemical analysis. Two alluvial (placer) 

samples were collected to help evaluate any possible 

placer-gold resources. The methods and results of the U.S. 

Bureau of Mines investigation in the study area were reported by Campbell (1987). Additional information is 

available from the U.S. Bureau of Mines, Western Field 

Operations Center, E. 360 Third Ave., Spokane, WA 

99202.

Acknowledgments

The authors gratefully acknowledge the cooperation of 

personnel of the U.S. Bureau of Land Management Prineville District Office, Prineville, Oreg., for providing access 

information and maps of the study area. We thank Harold 

D. Tracy for information concerning the Micron Exploration Company claim group. The able field assistance of 

Jeanette Smith, David Roth, Jim Fox, Steven Smith, and 

Randy Baker of the U.S. Geological Survey and Edward 

McHugh of the U.S. Bureau of Mines is greatly appreciated.

APPRAISAL OF IDENTIFIED RESOURCES

By Harry W. Campbell 

U.S. Bureau of Mines

Mining History

There are no mining districts in or near the study area. 

The closest districts, the Ashwood (gold) and Horse 

Heaven (mercury) mining districts, are located 20 to 25 mi 

south of the study area just east of the small town of 

Ashwood (fig. 1). In September 1983, Micron Exploration 

Company began locating 11 lode mining claims in the 

study area (Micron claim group, fig. 2) following the report 

of very high gold contents in reconnaissance geochemical 

samples of Columbia River basalt collected by the U.S. 

Bureau of Land Management (Davis, 1983). The claims 

were still active in 1986 according to U.S. Bureau of Land 

Management claim recordation indices. The entire study 

area was leased for oil and gas exploration during 1986.

Appraisal of Mineral Resources

Micron Exploration Company collected rock samples 

on their claims in the study area to determine the amount 

of gold present. Company representative H.D. Tracy 

(written commun., 1986) indicated that "company assays 

show a much stronger gold content than 150 parts per 

million" (ppm). Additionally, the representative stated that 

gold values were not restricted to any particular geologic 

structure, for basalt samples collected throughout the claim 

group yielded consistently high gold assays (as much as 

250 ppm) (H.D. Tracy, oral commun., 1986). In order to 

evaluate the mineral resources of the Micron claim group, 

11 rock samples were collected by the U.S. Bureau of 

Mines in the study area (Campbell, 1987). No gold was 

detected in any of the samples at a detection limit of 5 parts 

per billion (ppb). No mineral resources were identified at 

the Micron claim group for the following reasons: (1) the 

absence of detectable gold or anomalous concentrations of 

other metals in the U.S. Bureau of Mines samples, (2) the 

lack of visible mineralization and significant alteration, and 

(3) no reports of gold mineralization in the Columbia River 

basalts in the region.

Two reconnaissance alluvial samples were also collected by the U.S. Bureau of Mines from a river bar in the 

study area adjacent to the Micron claim group (Campbell, 

1987). Both samples contain gold in very fine (less than 

0.001 in.), subrounded, flat flakes. One of the samples also 

contains a trace of cinnabar (a common mercury-ore mineral). Gold contents of the samples do not exceed about 

0.0002 oz/yd3 . At a gold price of $400/troy oz, the gravel

Mineral Resources of the North Pole Ridge Wilderness Study Area, Oregon B5
would be worth about $0.07/yd3 too low a grade to be 

considered a resource under foreseeable economic conditions.

Stone (basalt), sand, and gravel are abundant in the 

study area and could be used for aggregate and fill. 

However, these commodities have low unit value and high 

bulk, which precludes their use for any purposes other than 

for local construction projects. Ample, more accessible 

supplies of stone, sand, and gravel outside the study area 

are adequate for regional demand.

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

By Scott A. Minor, Jay A. Ach, James C. Frisken, and 

Richard J. Blakely 

U.S. Geological Survey

Geology

The study area is located in the southern part of the 

Columbia Plateau physiographic province, which is characterized by extensive sequences of gently north-tilted, 

middle Miocene basalt flows of the Columbia River Basalt 

Group (Swanson and others, 1981; Walker, 1977). Less 

than 100 mi southeast of the study area the Columbia 

Plateau terminates against the Blue Mountains, an uplifted 

block containing Mesozoic volcanic-arc basement rocks 

(Brooks and Vallier, 1978). The active Cascades volcanic 

arc bounds the southwest side of the province about 50 mi 

west of the study area. Directly south of the study area the 

Columbia River basalts are underlain by Eocene and Oligocene volcanic and associated rocks that, in turn, overlie 

Mesozoic marine sedimentary rocks. Columbia River 

basalt in the region has locally been folded and faulted 

during the Miocene and Pliocene.

The oldest exposed rocks in the study area, at the 

bottom of the John Day River canyon, consist of basalt 

flows of the Columbia River Basalt Group (fig. 2) (Swanson and others, 1981). However, rocks of the John Day 

Formation (Merriam, 1901a) of chiefly Oligocene age, 

which lie unconformably below the Columbia River Basalt 

Group (Swanson, 1969), are exposed in the John Day River 

canyon just 1 mi south of the study area (fig. 2) (Swanson, 

1969; Robinson, 1975; Swanson and others, 1981). The 

John Day Formation near the study area consists of intercalated tuffs, tuffaceous sedimentary rocks, and mafic 

flows. Unconformably underlying the John Day Formation 

and exposed just a few miles farther south up canyon are 

rocks of the Clarno Formation (Merriam, 1901b). The 

Clarno Formation, principally Eocene in age, consists 

chiefly of interfingering andesitic flows, domes, plugs, and 

breccias and associated volcaniclastic and tuffaceous rocks. 

Presumably both the John Day and Clarno Formations,

which have a combined thickness of several thousand feet 

in the area, extend northward underneath the study area. 

This assumption is supported by data from Standard Oil 

Company's Kirkpatick No. 1 petroleum test hole (Fox and 

Reidel, 1987), which is located 13 mi northeast of the study 

area (fig. 1). The hole penetrated 2,440 ft of rocks of the 

Columbia River Basalt Group before encountering 4,255 ft 

of John Day and possibly Clarno rocks. These data suggest 

that the base of the Columbia River Basalt Group may be 

only a few hundred feet below river level at the northern 

end of the study area.

Flows of the Columbia River Basalt Group form the 

bedrock throughout the study area (fig. 2). The maximum 

exposed thickness of the basalts in the study area is about 

1,600 ft, equivalent to the maximum depth of the John Day 

River canyon. The gray Columbia River basalt flows 

typically range in thickness from 50 to 100 ft and have 

conspicuous columnar joints, especially near the base of 

each flow. The upper parts of the flows are usually vesicular and autobrecciated and readily erode into ledges, 

whereas the denser, more resistant middle and lower parts 

of the flows form prominent cliffs. Such topographic 

expression of the subhorizontal flows commonly results in 

"stair-step" topography along the canyon walls. Interflow 

layers of tuffaceous rocks are present only locally in the 

sequence and rarely exceed 10 ft in thickness.

Swanson and others (1981) subdivided rocks of the 

Columbia River Basalt Group in the study area into two 

formations following the stratigraphic nomenclature of 

Swanson and others (1979). The two formations, the Picture Gorge and Grande Ronde Basalts, are in part contemporaneous and interfinger. The Picture Gorge Basalt, 

which is only exposed in the southern part of the study area 

near river level, is distinguished in the field by its mediumto coarse-grained, porphyritic (plagioclase) texture as 

compared to the generally aphyric, fine-grained nature of 

the Grande Ronde Basalt (Swanson and others, 1981). 

Rocks of the Picture Gorge and Grande Ronde Basalts have 

yielded potassium-argon radiometric ages ranging from 

16.5 to 14 million years before present (Ma).

Large (1 mi or more in length) landslide deposits near 

the base of the John Day River canyon in and near the 

study area (fig. 2) are typically expressed by hummocky topography, contain jumbled blocks of basalt, and are 

bounded on their up-slope sides by prominent arcuate 

headwall scarps. Some of the landslides, which border 

long stretches of the John Day River, may have slid off of 

the canyon walls before the river cut down to its present 

level and thus may contain and (or) conceal older river 

alluvium. The larger landslides in and south of the southern part of the study area, including a slide mass more than 

10 mi long (Swanson, 1969; Swanson and others, 1981), 

most likely failed along incompetent, clay-altered tuffaceous layers in the John Day Formation (Peck, 1964; 

Swanson, 1969).

B6 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
There is abundant geomorphic evidence in the study 

area of older, shallower (less entrenched) channels of the 

John Day River, the most conspicuous of which are several 

meander scars perched as much as 600 ft above the present 

river level along the canyon wall. Erosional remnants of 

river alluvium deposited in these older channels locally 

mantle the meander scars. Active and recent alluvium in 

the study area consist primarily of sand and gravel deposits 

that blanket the inside banks of the John Day River entrenched meanders (fig. 2). Talus aprons and cones composed of basalt debris mantle the bases of most of the large 

subvertical cliffs along canyon walls.

The area occupied by the Columbia Plateau was probably the location of a broad northeast-trending rift zone that 

developed across the Mesozoic continental margin in the 

Early Cretaceous (Fritts and Fisk, 1985a). This zone of 

rifting was inferred by Fritts and Fisk to have subsided and 

accumulated sediment and volcanic material (including the 

Columbia River basalts) more or less continuously for the 

duration of the Tertiary, thus forming the Columbia basin. 

Uplift of the Blue Mountains at the south end of the Columbia Plateau began in Eocene time during deposition of 

the Clarno Formation and continued for the remainder of 

the Tertiary (Fox and Reidel, 1987). Angular unconformities that separate rocks of the Clamo Formation, John Day 

Formation, and Columbia River Basalt Group south of the 

study area (Swanson, 1969; Robinson, 1975) provide supporting evidence that uplift and subsidence continued in the 

region during the Oligocene and early Miocene. Entrenchment of the meandering John Day River into its canyon and 

the perched meander scars in the canyon suggest that northward tilting of the southern part of the Columbia Plateau 

and (or) subsidence of the central part of the plateau may 

have continued intermittently into the latest Tertiary or 

Quaternary.

In an overall sense, the Columbia River basalt flows 

that underlie the study area form part of a regionally extensive, gently (less than 5°) northward-tilted homocline. This 

simple structural geometry is complicated in the eastern 

part of the study area by a relatively complex north-trending zone of deformation that partly coincides with the 

straight, north-trending segment of the John Day River (fig. 

2). The zone is dominated by a discontinuous north-striking, high-angle normal fault that extends across the study 

area. The throw along this fault, which has down-to-thewest apparent displacement, decreases from about 600 ft 

0.5 mi south of the study area to a negligible amount at the 

mouth of Pete Enyart Canyon (fig. 2). No fault displacement is evident along a projected strike distance of 0.5 mi 

north of this point. The fault reappears, along with an 

adjoining fault splay, in the vicinity of the tight river 

meander near the northeast corner of the study area, where 

the average fault throw is about 200 ft. The fault extends 

north of this point for 3 mi into the Thirtymile Wilderness 

Study Area. (Ach and others, 1988). The east-trending,

west-plunging axis of a broad synclinal fold extends from 

the east across the area where the projected main fault trace 

shows no displacement. This fold, which most likely is the 

westward extension of a regional fold mapped by Swanson 

and others (1981), terminates against a partly concealed 

north-trending anticlinal bend and (or) normal fault about 

0.25 mi west of the main fault (fig. 2). The latter structure, 

which downdrops rocks eastward toward the subparallel 

main fault (or its projection), is expressed by abrupt 

changes in flow dip (as steep as 21° E.), small-displacement high-angle faults, and areas of complexly sheared and 

fractured rock. The zone of deformation associated with 

the anticlinal bend extends as far east as the main fault. 

The increase in throw along the main fault north and south 

of the syncline axis suggests that the fault, and perhaps the 

entire north-trending zone of deformation, acted as a structural accomodation zone during deformation that separated 

folded rocks to the east from unfolded rocks to the west.

Several other east- to northeast-trending broad, open 

folds are in the region, mainly east of the study area 

(Swanson and others, 1981). Some of these folds are cut 

by subparallel high-angle faults that also appear to be 

genetically related to the folds.

Faulting and folding on the Columbia Plateau, which is 

attributed primarily to regional north-south compression, 

was most active between about 11 and 3 million years ago 

(see Bela, 1982, for references). Much of the tilting and 

subsidence of the southern part of the plateau was approximately coeval with this deformation.

Geochemical Studies

A reconnaissance geochemical study was undertaken 

using rock, stream-sediment, nonmagnetic- and bulkpanned-concentrate, and spring-water samples collected 

from the study area. Stream-sediment samples represent 

eroded bedrock and surficial material from drainage basins 

that collectively cover most of the surface of the study area. 

The stream-sediment medium reflects bedrock background 

geochemistry and can indicate major areas of mineralization. The prepared nonmagnetic fraction of panned concentrates may be useful for detecting minerals associated 

with mineralization and alteration and is more likely to 

reveal small or poorly exposed mineralized areas. The rock 

samples provide background geochemical data and may be 

used to more precisely locate mineralized areas. Spring 

water is collected to determine the presence of uranium.

We collected 15 stream-sediment, 11 nonmagneticconcentrate, 10 bulk-concentrate, and 35 rock samples from 

in and near (within 0.25 mi of) the study area. One water 

sample was collected from a spring in the study area. All 

but three of the rock samples are from outcrops; the remaining rock samples are stream cobbles. All of the rock 

samples are basalt and are not obviously mineralized or 

altered. The stream-sediment, nonmagnetic-concentrate,

Mineral Resources of the North Pole Ridge Wilderness Study Area, Oregon B7
and rock samples were analyzed for 31 elements using a 

six-step semiquantitative emission spectrographic method 

described by Grimes and Marranzino (1968) and were 

analyzed for gold by an atomic-absorption method described by Thompson and others (1968). The bulk-concentrate, stream-sediment, and rock samples were also analyzed for gold by a graphite-furnace atomic-absorption 

method (Meier, 1980) that provides a lower limit of detection of 0.002 parts per million (ppm) as compared to 0.05 

or 0.1 ppm with the Thompson method. The stream-sediment and rock samples were analyzed for mercury by a 

method described by Koirtyohann and Khalil (1976) and 

for arsenic, antimony, bismuth, cadmium, and zinc by an 

inductively coupled argon plasma-atomic emission spectrographic method described by Crock and others (1987). The 

sediment, stream-cobble, and water samples were analyzed 

for thorium and (or) uranium by methods described by 

Millard (1976), Centanni and others (1956), and the Scintex 

Corporation (1978), respectively. The nonspectrographic 

analyses were conducted to provide data on elements not 

determined spectrographically or to provide data at lower 

levels of detection. Details of the sampling, preparation, 

and analytical methods and results are being prepared by 

B.M. Adrian and others (written commun., 1988)

For the purposes of defining anomalies, the geochemical threshold values for rocks and sediments have been 

calculated at either (1) three times the arithmetic means of 

elemental concentrations obtained for basalt samples collected from this study area and the two other nearby wilderness study areas or (2) three times the published average 

elemental concentrations in basalts (Levinson, 1980). For 

elements having calculated mean values below the lower 

limit of detection, the lower limit of detection is assigned 

as the threshold value. The threshold values for the nonmagnetic concentrates are chosen on the basis of experience with the medium. The threshold value for uranium in 

water was chosen as two times the average value in river 

waters (Levinson, 1980).

Anomalous concentrations of gold, silver, arsenic, 

copper, lead, tin, and (or) tungsten occur in four of the 

stream-sediment and three of all of the concentrate samples 

collected from the study area. A flake of gold and a grain 

of the mercury-ore mineral cinnabar were observed in two 

of the concentrate samples. Stream-sediment and concentrate samples collected in the study area are not considered 

to be as reliable as they are in other areas because of the 

strong possibility of contamination from flood-stage and 

older (perched) alluvium along the John Day River. All of 

the sediment-derived samples were collected at lower elevations than those of most of the perched alluvial deposits 

(see geology section), so at least some of the anomalies 

(and mineral grains) may be derived from the John Day 

River basin upstream from the study area. The anomalies 

are significant, however, in that they indicate the presence 

of some placer gold in the study area. Even if the anomalies are accepted as representative of bedrock in the study 

area, all but two concentrate anomalies are for single elements and are not considered significant by themselves. 

The two multi-element concentrate anomalies include large 

concentrations of tin and lead (as much as 2,000 ppm for 

each), both of which may result from contamination by lead 

shot and (or) other human artifacts that were seen in some 

concentrates.

Anomalous concentrations of gold, antimony, arsenic, 

barium, bismuth, cadmium, and mercury occur in 11 of the 

rock samples from the study area. The only gold value 

detected, 2.6 ppm (average of two analyses), is from a 

vesicular, silica- and clay-filled basalt sample collected on 

a ridge about 0.25 mi north of Big Gulch and 0.5 mi west 

of the John Day River (fig. 2). This sample also contains 

anomalous concentrations of the gold-pathfinder elements 

antimony, arsenic, and mercury. The other anomalous rock 

samples from the study area contain weak, generally singleelement anomalies of bismuth and cadmium as well as the 

gold-pathfinder elements arsenic and barium. None of the 

remaining U.S. Geological Survey rock samples, however, 

contain detectable gold at the lower limit of determination 

(0.002 ppm). Gottfried and others (1972) reported that 

gold is most concentrated in mafic igneous rocks and that 

analyzed samples of Columbia River basalt averaged 0.005 

ppm gold and ranged up to 0.011 ppm. The analytical 

method we used did not break down the silicate minerals, 

and this perhaps accounts for our lower readings. Any 

secondary gold introduced by mineralizing solutions, however, should have been detected by our method.

A rock sample collected by the U.S. Bureau of Land 

Management (Davis, 1983) about 1 mi southeast of the 

collection site of our auriferous rock sample contains 

anomalous concentrations of gold (0.150 ppm), silver (0.6 

ppm) and molybdenum (7 ppm). An additional U.S. Bureau of Land Management sample collected near Horse 

Mountain in the southern part of the study area (fig. 2) 

contains 0.060 ppm gold and 8 ppm molybdenum. These 

data, together with the U.S. Geological Survey data, give 

weak geochemical evidence that gold mineralization has 

taken place in the study area. The gold anomalies, however, are very spotty and are isolated from many of the 

gold-pathfinder-element anomalies. No corroborative evidence of epithermal alteration or mineralization, such as 

quartz veins or hydrothermal breccia, is present in or near 

the study area. Rock samples collected within the northtrending zone of faulted, sheared, and folded rock in the 

study area (see geology section and fig. 2) do not contain 

detectable gold but do show most of the gold-pathfinder 

anomalies. The anomalies may be derived from localized, 

inconspicuous, permeable fracture zones in and outside of 

the zone of deformation along which auriferous hydrothermal solutions flowed over a period of time. Concealed 

silicic intrusive rocks, if present, could possibly drive such 

a system.

B8 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
No uranium or thorium anomalies were detected in any 

of the samples collected in the study area.

Geophysical Studies

Magnetic, gravity, and radiometric data from northcentral Oregon were compiled and examined in order to aid 

assessment of the mineral resource potential of the North 

Pole Ridge Wilderness Study Area. The sparsely distributed nature of all three data sets is adequate for addressing 

the regional structural and tectonic setting of the study area 

but does not permit assessment of mineral resource potential at deposit scales except in limited areas directly beneath 

detailed profiles.

The only publicly available aeromagnetic data within 

the study area were compiled under contract to the U.S. 

Department of Energy as part of the National Uranium 

Resource Evaluation (NURE) program (High Life Helicopters, IncVQEB, Inc., 1981). These data were measured 400 

ft above average terrain along east-west profiles spaced 6 

mi apart and north-south profiles spaced 24 mi apart. Only 

one NURE profile actually crossed the study area; it was 

flown approximately east-west at latitude 45° 6.5' N. 

Anomalies within the study area are characterized by short 

wavelengths (500 to 6,000 ft), high amplitudes (100 to 

1,500 nanoteslas, nT), and high gradients (1 nT per ft). 

Unmetamorphosed basaltic rocks, such as the Columbia 

River basalt flows exposed throughout the study area, 

commonly have high magnetic susceptibilities and high 

remanent magnetizations. In low-level aeromagnetic profiles, these volcanic rocks typically cause high-amplitude, 

short-wavelength magnetic anomalies that often obscure 

anomalies caused by deeper magnetic sources. Some of the 

individual highs and lows along magnetic profiles may 

indicate mineralized areas, but they are more likely to be 

the result of lateral variations in the abundance and characteristics of magnetite grains in shallow basaltic rocks.

The NURE magnetic profile indicates a region of relatively low magnetic intensity about 1 mi wide and centered 

at longitude 120°28' W. This depression approximately coincides with the north-trending zone of deformation in the 

eastern part of the study area (fig. 2) and may indicate 

associated alteration of magnetic minerals. There is no 

clear continuation of this magnetic depression, however, to 

adjacent NURE profiles to the north and south.

Gravity data from the vicinity of the study area were 

obtained from the National Geophysical Data Center, National Oceanic and Atmospheric Administration, Boulder, 

CO 80303. Gravity measurements are scattered at 3- to 6- 

mi spacing in the region, and none are actually within the 

study area. Observed gravity measurements, based on the 

International Gravity Standardization Net datum (Morelli, 

1974), were reduced to free-air anomalies using standard 

formulas (Telford and others, 1976). Bouguer, curvature, 

and terrain corrections (out to a distance of 103.6 mi from

each station) at a standard reduction density of 2.67 grams 

per cm3 (167 Ib per ft3) were added to the free-air anomaly 

at each station to determine complete Bouguer gravity 

anomalies.

Bouguer anomalies typically reflect shallow density 

contrasts of interest to resource appraisals, but they also 

include contributions from deep-crustal masses that correlate with topography in a manner consistent with the concept of isostasy. To reduce the effect of deep sources 

related to isostasy, an isostatic residual-gravity map was 

constructed from the Bouguer gravity data by removing a 

regional gravity field computed from a model of the crustmantle interface, assuming Airy-type isostatic compensation (Jachens and Griscom, 1985). A regional perspective 

of the gravitational setting of the area can be seen on the 

isostatic residual map of Jachens and others (1985).

The sparse distribution of gravity measurements precludes a detailed analysis of mass distributions within or 

adjacent to the study area but is sufficient to illuminate the 

regional tectonic and structural setting. The study area lies 

within a broad positive isostatic residual anomaly. The 

anomaly is 20 milligals higher in amplitude than measurements in surrounding areas, has lateral dimensions of approximately 15 mi east-west and 30 mi north-south, and 

forms part of a chain of anomalies that trends northeast 

through northern Oregon. Riddihough and others (1986) 

noted that this lineament is on strike with similar gravity 

features in the Klamath Mountains in northwest California 

and have suggested that it reflects a pre-Tertiary continental 

boundary extending across this part of Oregon and Washington.

Radiometric data were collected as part of the NURE 

survey discussed earlier (High Life Helicopters, Inc./QEB, 

Inc., 1981). Recordings were made of gamma-ray flux 

from radioactive isotopes of potassium, thorium, and uranium along east-west flightlines spaced approximately 6 mi 

apart and at an average altitude of 400 ft above terrain. 

Only one profile actually crossed the study area. Count 

rates were low on this profile, and no anomalous radiation 

was detected. However, because only one flightline 

crossed the study area and because gamma rays are 

strongly attenuated by passage through earth materials, 

these data do not preclude the presence of anomalous 

amounts of radioactive elements away from the flightline or 

buried a few feet or more beneath the ground surface.

Mineral and Energy Resource Potential

The North Pole Ridge Wilderness Study Area has 

moderate to low resource potential for gold in two types of 

deposits. The study area has low energy resource potential 

for oil and gas. There is no potential for geothermal energy.

The active Micron claims in the eastern part of the 

study area (fig. 2) reportedly yielded rock samples

Mineral Resources of the North Pole Ridge Wilderness Study Area, Oregon B9
containing economically significant concentrations of gold. 

Our geologic investigations in this and all other parts of the 

study area did not indicate the presence of any 

hydrothermally altered or mineralized rocks. Aeromagnetic data collected over the eastern part of the study 

area, however, give some indication of altered magnetic 

minerals in rocks near the north-trending zone of 

deformation that crosses the eastern part of the study area 

(fig. 2). A few gold and gold-pathfinder geochemical 

anomalies detected in the present study also remotely 

suggest that auriferous hydrothermal fluids may have 

permeated localized fracture networks and porous rocks, 

mainly in the eastern part of the study area. These fluids 

may have deposited small amounts of gold or gold-bearing 

minerals at or near the surface. Such metal-bearing fracture 

networks, if present, may be interconnected with, and 

genetically related to, the north-trending zone of 

deformation. A possible heat source for a hydrothermal 

convection system in the region would be shallow, silicicto-intermediate intrusions emplaced after eruption of, but 

concealed by, flows of the Columbia River Basalt Group. 

Mineralized fluids could have migrated upward from such 

intrusions into wall rock along pre-existing conduits such 

as high-angle faults and fractures. Gold and mercury 

epithermal ore deposits in the Ashwood and Horse Heaven 

mining districts south of the study area are associated with 

rhyolitic to andesitic near-surface plugs and adjoining 

faults of probable Oligocene age (Brooks, 1963; Peck, 

1964; Brooks and Ramp, 1968). However, no intrusive 

rocks younger than Oligocene have been recognized in the 

region, and existing geophysical data do not suggest the 

presence of subsurface intrusive bodies. Thus, 

hydrothermal leakage along faults and fractures as a cause 

of the spotty gold geochemical anomalies in the study area 

is highly speculative, and assessing the likelihood for 

undiscovered ore deposits of gold and gold-related metals 

is difficult The eastern part of the study area has moderate 

potential, certainty level B, for gold resources in epithermal 

deposits (fig. 2). This part of the study area contains most 

of the geochemical anomalies, the north-trending zone of 

faults, fractures, and folds, and the Micron (gold) claim 

group. The remainder of the study area, lacking any 

noticeable deformation and containing weak, scattered 

geochemical anomalies, has low resource potential, 

certainty level B, for gold in epithermal deposits.

Geochemical results from the U.S. Geological Survey 

and U.S. Bureau of Mines stream-sediment and concentrate 

sampling indicate small amounts of placer gold in the active, recent, and possibly reworked older alluvium of the 

John Day River. The source of this gold may have been 

mineralized intrusive rocks of the John Day Formation that 

are present upstream from the study area and are similar to 

those in the Ashwood and Horse Heaven mining districts. 

Alternatively, the gold may have traveled far down river

from gold deposits in the Blue Mountains region (Brooks 

and Ramp, 1968). Although no placer gold resources have 

been identified in the study area, it is remotely possible that 

small undiscovered gold placers are contained in the older 

and (or) recent alluvium in the study area. The lower 

depths of the John Day River canyon in the study area, at 

or below the level of the perched, alluvium-mantled meander scars, have low resource potential, certainty level C, for 

gold in small placer deposits (fig. 2).

Central Oregon has been explored for oil since the 

1930's, but no economic discoveries of oil or gas have been 

made (Thompson and others, 1984). Exploration efforts 

and petroleum resource appraisals are hampered by only 

meager data available on subsurface geology in central 

Oregon (Thompson and others, 1984; Fritts and Fisk, 

1985a, b). Few deep wells have been drilled, outcrops of 

pre-Cenozoic rocks are rare, and the thick Cenozoic volcanic cover causes difficulty in the interpretation of geophysical data (Newton, 1974). In addition, Cenozoic structures of the region differ from more structurally complex, 

underlying Mesozoic structures. Little is known about preMesozoic structures (G.W. Walker, oral commun., 1987).

The primary exploration targets in central Oregon have 

been within two Cretaceous basins (Newton, 1968; Fritts 

and Fisk, 1985a, b). The largest and oldest is the Columbia 

River basin of Cretaceous age (Newton, 1966, 1977; Fritts 

and Fisk, 1985a, b). The North Pole Ridge Wilderness 

Study Area is in the southwestern part of this basin. The 

smaller and slightly younger (latest Cretaceous) Ochoco 

basin (Thompson and others, 1984) lies to the south and 

does not extend as far north as this study area.

Oil and gas leases cover the study area. Four test holes 

were drilled in the vicinity of the study area between 1929 

and 1957: three near Clarno, 12 mi to the south, and one 

near Condon, 13 mi to the northeast Well logs for all holes 

are on file at the Oregon Department of Geology and 

Mineral Industries (DOGAMI), Portland, Oreg. The holes 

near Clarno indicate that pre-Tertiary rocks are overlain by 

2,870 to 4,000 ft of rocks of the John Day and (or) Clarno 

Formations. One hole near Clarno, the Clarno Basin Oil 

Company's Burgess No. 2 (fig. 1), had a gas show, presumably from Cretaceous rocks. Asphalt-bearing geodes 

have also been found in the vicinity of Clarno (Collier, 

1914; Buwalda, 1921).

The best studied and documented hole in the region is 

Standard Oil Company's Kirkpatrick No. 1, located near 

Condon (fig. 1; see also geology section). The lower 2,031 

ft of the 8,726-ft hole was in Mesozoic sedimentary rocks, 

primarily argillite but including some graywacke and 

siltstone (Fox and Reidel, 1987). While the Mesozoic 

sedimentary rocks are thermally mature (Newton, 1979; 

L.H. Fisk, unpub. data, 1986; Summer and Verosub, 1987), 

the total organic content (TOC) of these rocks is low to 

very low (Brown and Ruth Laboratories, Inc., 1983; Fox

B10 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
and Reidel, 1987). Most of the organic material present is 

terrigenous, hydrogen poor, and gas prone (Brown and 

Ruth Laboratories, Inc., 1983).

For purposes of an oil and gas resource potential assessment, it is assumed that the subsurface stratigraphy of 

the study area is similar to that in the Kirkpatrick No. 1 

hole. The types of Mesozoic rocks present in the lower part 

of the hole usually have poor porosity, thereby limiting 

their potential as reservoir rocks. Their lack of potential as 

source rocks is indicated by their low TOC. Whereas the 

rocks have been determined to be thermally mature, local 

Oligocene rhyolite intrusions (Fox and Reidel, 1987) may 

have produced intense local heating, degrading or driving 

off nearby hydrocarbons.

Fouch (1983) rated the study area as having "low 

potential" for oil and gas, and Fox and Reidel (1987) 

considered the area around the Kirkpatrick No. 1 well to 

have "marginal hydrocarbon potential." However, Davis 

(1983) considered the study area to have "moderate potential" for hydrocarbons. The possible lack of both suitable 

source and reservoir rocks and the possible local overheating indicate that there is little likelihood for the occurrence 

of oil and gas in the study area. Therefore, under the definitions used in this study, the entire study area is assessed 

as having low resource potential for oil and gas (fig. 2). 

The stratigraphy in the nearest drill holes may differ from 

that of the study area, and the lack of available seismic data 

precludes any knowledge of subsurface structure or potential hydrocarbon traps; a certainty level of B is assigned.

The study area has no resource potential for geothermal energy, certainty level D. The study area contains no 

hot or warm springs (Bliss, 1983), and previous regional 

geothermal surveys have not indicated any geothermal 

resource potential for the area (Bowen and others, 1978; 

Riccio, 1978; Muffler, 1979; National Geophysical Data 

Center, 1982; Reed, 1983; Bliss, 1983). In addition, the 

study area lies within a small area that has lower heat flow 

than the rest of eastern Oregon and Washington (Nathenson 

and others, 1983).

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Muffler, L.J.P., ed., 1979, Assessment of geothermal resources of 

the United States 1978: U.S. Geological Survey Circular 

790, 163 p.

Nathenson, Manuel, Guffanti, Marianne, Sass, J.H., and Munroe, 

R.J., 1983, Regional heat flow and temperature gradients, in 

Reed, M.J., ed., Assessment of low-temperature geothermal 

resources of the United States 1982: U.S. Geological Survey Circular 892, p. 9-16.

National Geophysical Data Center, 1982, Geothermal resources of 

Oregon: Boulder, Colo., National Oceanic and Atmospheric 

Administration, scale 1:500,000.

Newcomb, R.C., 1970, Tectonic structure of the main part of the 

basalt of the Columbia River Group, Washington, Oregon, 

and Idaho: U.S. Geological Survey Miscellaneous Geologic 

Investigations Map 1-587, scale 1:500,000.

Newton, V.C. Jr., 1966, Oil and gas exploration in 1965: The Ore 

Bin, v. 28, no. 1, p. 20-28.

 1968, Oil and gas exploration in Oregon: The Ore Bin, v. 

30, no. 1, p. 12-20.

 1974, Oil and gas exploration in 1973: The Ore Bin, v. 36, 

no. 1, p. 4-8.

 1977, Oil and gas exploration in 1976: The Ore Bin, v. 39, 

no. 1, p. 16-17.

-1979, Petroleum source rock tests on two central Oregon

wells: Oregon Geology, vol. 41, no. 4, p. 63-64.

Peck, D.L., 1964, Geologic reconnaissance of the Antelope-Ashwood area, north-central Oregon, with emphasis on the John 

Day Formation of late Oligocene and early Miocene age: 

U.S. Geological Survey Bulletin 1161-D, 26 p.

Reed, M.J., ed., 1983, Assessment of low-temperature geothermal 

resources of the United States 1982: U.S. Geological Survey Circular 892, 73 p.

Riccio, J.F., 1978, Preliminary geothermal resource map of Oregon: Oregon Department of Geology and Mineral Industries 

Geological Map Series GMS-11.

Riddihough, Robin, Finn, Carol, and Couch, Richard, 1986, Klamath-Blue Mountain lineament, Oregon: Geology, v. 14, no. 

6, p. 528-531.

Robinson, P.T., 1975, Reconnaissance geologic map of the John 

Day Formation in the southwestern part of the Blue Mountains and adjacent areas, north-central Oregon: U.S. Geological Survey Miscellaneous Investigations Series Map 1-872, 

scale 1:125,000.

Scintex Corporation, 1978, UA-3 uranium analyzer: Toronto, 

Canada, Scintex Corporation, 45 p.

Summer, N.S., and Verosub, K.L., 1987, Extraordinary maturation profiles of the Pacific Northwest: Oregon Geology, v. 

49, no. 11, p. 135-140.

Swanson, D.A., 1969, Reconnaissance geologic map of the east 

half of the Bend quadrangle, Crook, Wheeler, Jefferson, 

Wasco, and Deschutes Counties, Oregon: U.S. Geological 

Survey Miscellaneous Geologic Investigations Map 1-568, 

scale 1:250,000.

Swanson, D.A., Anderson, J.L., Camp, V.E., Hooper, P.R., 

Taubeneck, W.H., and Wright, T.L., 1981, Reconnaissance 

geologic map of the Columbia River Basalt Group, northern 

Oregon and western Idaho: U.S. Geological Survey OpenFile Report 81-797, 33 p., 5 sheets, scale 1:250,000.

Swanson, D.A., Wright, T.L., Hooper, P.R., and Bentley, R.D., 

1979, Revisions in stratigraphic nomenclature of the Columbia River Basalt Group: U.S. Geological Survey Bulletin 

1457-G, 59 p.

Telford, W.M., Gelhart, L.P., Sheriff, R.E., and Keyes, D.A., 

1976, Applied geophysics: New York, Cambridge University 

Press, 960 p.

Thompson, C.E., Nakagawa, H.M., and Van Sickle, G.H., 1968, 

Rapid analysis for gold in geologic materials, in Geological 

Research 1968: U.S. Geological Survey Professional Paper 

600-B, p. B130-B132.

Thompson, G.G., Yett, J.R., and Green, K.F., 1984, Subsurface 

stratigraphy of the Ochoco basin, Oregon: Oregon DepartMineral Resources of Wilderness Study Areas: John Day Region, Oregon
ment of Geology and Mineral Industries Oil and Gas Investi- Geological Survey Circular 831, 5 p.

gation OGI-8, 22 p., 7 pi. Walker, G.W., 1977, Geologic map of Oregon east of the 121st

U.S. Bureau of Mines and U.S. Geological Survey, 1980, Prin- meridian: U.S. Geological Survey Miscellaneous Investigaciples of a resource/reserve classification for minerals: U.S. tions Series Map 1-902, scale 1:500,000, 2 sheets.

Mineral Resources of the North Pole Ridge Wilderness Study Area, Oregon B13

APPENDIXES
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

LEVELS OF RESOURCE POTENTIAL

H HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of data 

indicate a high degree of likelihood for resource accumulation, where data support mineral-deposit models 

indicating presence of resources, and where evidence indicates that mineral concentration has taken place. 

Assignment of high resource potential to an area requires some positive knowledge that mineral-forming processes 

have been active in at least part of the area.

M MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of data 

indicate reasonable likelihood for resource accumulation, and (or) where an application of mineral-deposit models 

indicates favorable ground for the specified type(s) of deposits.

L LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics 

define a geologic environment in which the existence of resources is permissive. This broad category embraces 

areas with dispersed but insignificantly mineralized rock, as well as areas with little or no indication of having 

been mineralized.

N NO mineral resource potential is a category reserved for a specific type of resource in a well-defined area.

U UNKNOWN mineral resource potential is assigned to areas where information is inadequate to assign a low, 

moderate, or high level of resource potential.

LEVELS OF CERTAINTY

A Available information is not adequate for determination of the level of mineral resource potential.

B Available information only suggests the level of mineral resource potential.

C Available information gives a good indication of the level of mineral resource potential.

D Available information clearly defines the level of mineral resource potential.

<

hz

UJ

U

O 

on

UJ

UJ

>

A

U/A

UNKNOWN POTENTIAL

B

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L/B

LOW POTENTIAL

C

H/C

HIGH POTENTIAL

M/C

MODERATE POTENTIAL

L/C

LOW POTENTIAL

D

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

LEVEL OF CERTAINTY

Abstracted with minor modifications from:

Taylor, R.B., and Steven, T.A., 1983, Definition of mineral resource potential: Economic Geology, v. 78, no. 6, p. 1268-1270.

Taylor, R.B., Stoneman, R.J., and Marsh, S.P., 1984, An assessment of the mineral resource potential of the San Isabel National Forest, south-central Colorado: U.S.

Geological Survey Bulletin 1638, p. 40-42. 

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey Open-File Report 84-0787, p. 7, 8.

B16 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured

Rese

Indicated

jrves

Marginal 

Reserves

Demonstrated 

Subeconomic

Resources

i

Inferred

Inferred 

Reserves

Inferred 

Marginal 

Reserves

Inferred 

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

Hypothetical Speculative

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from McKelvey,V.E., 1972, Mineral 

resource estimates and public policy: American Scientist, v. 60, p. 32-40; and U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles 

of a resource/reserve classification for minerals: U.S. Geological Survey Circular 831, p. 5.

Mineral Resources of the North Pole Ridge Wilderness Study Area, Oregon B17
GEOLOGIC TIME CHART

Terms and boundary ages used by th<; U.S. Geological Survey in this report

1

EON

Phanerozoic

Proterozoic

Archean

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Quaternary

Neogene 

Subperiod

Tertiary 

Paleogene

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Mississippian

Devonian

Silurian

Ordovician

Cambrian

iiarvwi

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

pre-Archean2

 ._ . . . _._......... 

ACE ESTIMATES OF 

BOUNDARIES IN 

MILLION YEARS (Ma)

 0.010

 1.7

5

 24

T Q

 55

 66

96

1 QQ

205

 -240

 290 

,, * *()

-»UW

 410

 435

~ .>/ \j

JWv/

 1600

 2500

 3000 

 3400

 Azzn 

'Rocks older than 570 Ma also called Precambrian, a time term without specific rank. 

Informal time term without specific rank.

B18 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon GPO 685-041/9770
SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

Periodicals

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