Mineral Resources of the

Spring Basin Wilderness Study Area,

Wheeler County, Oregon

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Chapter C

Mineral Resources of the

Spring Basin Wilderness Study Area,

Wheeler County, Oregon

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

RICHARD J. BLAKELY 

U.S. Geological Survey

RICHARD A. WINTERS and THOMAS J. PETERS 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1 743

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

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purposes only and does not constitute 

endorsement by the U.S. Geological Survey

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Mineral resources of the Spring Basin Wilderness Study 

Area, Wheeler County, Oregon.

(U.S. Geological Survey bulletin ; 1743-C

Bibliography: p.

Supt. of Docs. no. : I 19.3:1743-C

1. Mines and mineral resources Oregon Spring Basin 

Wilderness. 2. Geology Oregon Spring Basin Wilderness. 

3. Spring Basin Wilderness (Or.) I. Ach, Jay A. II. Series. 

QE75.B9 no. 1743-C 557.3s 88-600388 

[TN24.07] [553'.09795'81]
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Areas

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 of certain areas to 

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

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

of part of the Spring Basin (OR-005-009) Wilderness Study Area, Wheeler County, Oregon.

CONTENTS

Summary Cl 

Abstract Cl 

Character and setting Cl 

Identified resources Cl 

Mineral resource potential Cl 

Introduction C2

Area description C2 

Previous and present investigations C2 

Acknowledgments C3 

Appraisal of identified resources C3 

Assessment of mineral resource potential C3 

Geology C3 

Geochemical studies C5 

Geophysical studies C6 

Magnetic data C7 

Gravity studies C7 

Radiometric data C7 

Conclusions C8

Mineral and energy resource potential of the Spring Basin Wilderness Study Area C8 

Mineral resource potential C8 

Energy resource potential C9 

References cited CIO 

Appendixes

Definition of levels of mineral resource potential and certainty of assessment C14 

Resource/reserve classification CIS 

Geologic time chart C16

FIGURES

1 Index map showing location of the Spring Basin Wilderness Study Area, Wheeler County, 

Oregon C2

2 Map showing mineral resource potential and geology of the Spring Basin Wilderness Study Area, 

Wheeler County, Oregon C4

Contents

Mineral Resources of the

Spring Basin Wilderness Study Area,

Wheeler County, Oregon

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

U.S. Geological Survey

Richard A. Winters and Thomas J. Peters 

U.S. Bureau of Mines

SUMMARY 

Abstract

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

approximately 5,982 acres of the Spring Basin (OR-005-009) 

Wilderness Study Area in north-central Oregon were evaluated for mineral resources (known) and mineral resource 

potential (undiscovered). In this report, "wilderness study 

area" and "study area" refer to the 5,982 acres for which 

mineral surveys were requested. Fieldwork for this report was 

carried out in 1987. No identified mineral resources are 

known to exist within the study area. No mines or mining 

districts are located inside the study area; however, a part of 

the area is under lease for oil and gas exploration.

An area in the easternmost part of the study area has low 

mineral resource potential for silver, gold, and mercury. A 

small area in the central part of the study area has low 

mineral resource potential for mercury. The study area has a 

low resource potential for oil and gas and no resource potential for uranium or for geothermal energy.

Character and Setting

The Spring Basin Wilderness Study Area is located in 

the northwestern part of the Blue Mountains physiographic 

province of north-central Oregon and is centered about 13 

mi southwest of Fossil, Oregon (fig. 1). The canyon of the 

John Day River bounds the west side of the study area. In 

the study area, the terrain consists of moderately steep, 

rugged volcanic uplands and has several buttes that rise as 

high as 1,000 ft above surrounding areas. Most of the 

study area is underlain by Eocene and early Oligocene (see 

appendixes for geologic time chart) andesite flows, plugs, 

and domes and associated intertonguing volcaniclastic

Manuscript approved for publication, October 7, 1988.

rocks. Rhyolite ash-flow tuff that was erupted sometime 

between the late Eocene and early Miocene unconformably 

overlies these rocks in a small part of the study area. 

Mesozoic marine sedimentary rocks have been encountered 

in drill holes in the vicinity, and similar rocks are probably 

present a few thousand feet beneath the study area. Structurally the study area is simple. The rocks generally dip 

less than 5° and are cut by a few normal faults of small 

displacement.

Identified Resources

No identified mineral resources are known to exist 

within the study area. Three extant claims apparently were 

located for lapidary material. Samples of agate from the 

claims were evaluated and found to be of poor quality. No 

mines or mining districts are located inside the study area; 

however, approximately 23 percent of the area is under 

lease for oil and gas exploration.

Mineral Resource Potential

The Spring Basin Wilderness Study Area has a low 

mineral resource potential for silver and gold in epithermal 

deposits in the easternmost part of the study area. This part 

of the area also has a low mineral resource potential for 

epithermal mercury deposits. The potential for both types 

of deposits is indicated by low-level geochemical 

anomalies and by geologic similarities to deposits in the 

Ash wood/Horse Heaven mining district 10 to 15 mi to the 

west-southwest. Low-level geochemical anomalies indicate 

that a small area in the center of the study area also has low 

mineral resource potential for mercury in epithermal 

deposits.

Mineral Resources of the Spring Basin Wilderness Study Area, Wheeler County, Oregon C1
The study area has low potential for oil and gas. Dry 

holes are located approximately 3, 4, and 26 mi from the 

study area. Well logs and various geochemical studies 

indicate that suitable source and reservoir rocks are not 

present at these drill sites, but the possibility of more favorable source and reservoir rocks beneath the study area 

cannot be ruled out. No favorable reservoir structures are 

known in the study area.

No resource potential exists for uranium or for geothermal energy in the study area.

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. 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 the 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. Geo120°30' 120° 15'

45°00'

44°50'

 - r . _. _ _:_ __ _ _GILUAM_coyNTY__ ~"~~^ ~ WHEELER COUNTY

» Oregon Petroleum Company Clamo No. 1

Clarno Basin Company Burgess No. 2

APPROXIMATE BOUNDARY

OF

SPRING BASIN 

WILDERNESS STUDY AREA

WASCqcp

JEFFERSON CO

AREA OF MAP.?

A

Figure 1. Index map showing location of the Spring Basin 

Wilderness Study Area, Wheeler County, Oregon. Dots are 

dry wells.

logical 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 the appendixes for the definition of levels of mineral resource potential and certainty of 

assessment and for the resource/reserve classification.

Area Description

The part of the Spring Basin Wilderness Study Area 

(OR-005-009) evaluated for mineral resource potential 

encompasses 5,982 acres in north-central Oregon. It is 

located just east of the John Day River about 13 mi southwest of Fossil, Oregon (fig. 1). The area is characterized 

by a high ridge along the north and east boundaries. The 

principal drainages in the area, Spring Basin Canyon, Hay 

Bottom Canyon, and Eagle Canyon, flow south and west 

off this ridge and into the John Day River. Elevations 

range from 2,827 ft on Horse Mountain to 1,360 ft near the 

John Day River. The area has a semiarid climate (Strahler, 

1969) and an average of about 12 in. of precipitation a year 

(Meteorology Committee, Pacific Northwest River Basins 

Commission, 1969). Vegetation consists primarily of 

grasses, some sagebrush, and scattered juniper. Access to 

the area is provided by a dirt road and jeep trails that lead 

to the area from Oregon Highway 218.

Previous and Present Investigations

Little previous geologic work has been done in the 

study area. Swanson (1969) included the study area in a 

reconnaissance geologic study and extensively mapped the 

Columbia River Basalt Group beginning just north of the 

study area (Swanson and others, 1979,1981). Peck (1964) 

mapped a small area a few miles west of the study area.

Previous reconnaissance studies of the geology and 

mineral resources of wilderness study areas in the region 

were carried out by Davis (1983) and Fouch (1983). 

Regional uranium resource potential was evaluated as part 

of the U.S. Department of Energy National Uranium Resource Evaluation (NURE) program (High Life Helicopters, Inc./ QEB, Inc., 1981).

The U.S. Geological Survey conducted field studies in 

the study area in 1987. These studies consisted of geologic 

mapping, including checking of previously published geologic mapping, conducting further mapping, and collecting 

60 rock samples, 29 stream-sediment samples, and 22 

stream-sediment heavy-mineral-concentrate samples for 

chemical analysis. Available geophysical data were compiled and examined.

C2 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
The U.S. Bureau of Mines conducted a library search 

for information on the geology, mines, and prospects within 

the study area. Additional data were obtained from 

Wheeler County and U.S. Bureau of Land Management 

mining, lease, claim, and land status records. These data 

were used to determine the geologic setting, mining history, 

possible mineral commodities, mining claim ownership, 

and claim localities. Field studies by U.S. Bureau of Mines 

personnel were carried out in 1987 (Winters and Peters, 

1988) and involved searches for any existing mines, prospects, claims, or mineralized geologic structures; 8 rock 

samples and 13 alluvial samples were collected. Rock 

samples were checked for radioactivity and fluorescence. 

The rock samples also were analyzed for 34 elements by 

instrumental neutron activation by a contract laboratory. 

Alluvial samples were concentrated and inspected for gold 

and other valuable minerals. Complete analytical data are 

on file at 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 

the U.S. Bureau of Land Management personnel of the 

Prineville District Office, Prineville, Oregon, in providing 

access information and maps of the study area. Ranchers 

Jon Bowerman and Bill Cross graciously provided access 

to their land. Dan E. Wermiel, Oregon Department of 

Geology and Mineral Industries, provided much information pertaining to the petroleum potential of central Oregon.

APPRAISAL OF IDENTIFIED RESOURCES

By Richard A. Winters and Thomas J. Peters 

U.S. Bureau of Mines

No mining districts exist in or near the Spring Basin 

Wilderness Study Area. Three lode mining claims in the 

study area (fig. 2) apparently were located for lapidary 

material. The Crystal Peak and MEM-CAF mining claims 

were located in 1978 and 1975, respectively. The name 

and date of location of a third claim is unknown. Approximately 23 percent of the area studied is currently covered 

by oil and gas lease applications.

No identified mineral resources exist within the study 

area. Samples of agate were evaluated and determined to 

be of poor quality. Four of thirteen alluvial samples contain gold ranging from 0.0000097 to 0.000416 troy ounces 

per cubic yard ($0.005 to $0.21 per cubic yard assuming 

gold at $500 per troy ounce); significant accumulations of 

alluvium have not been deposited in the study area.

No economic concentrations of minerals were observed in the rock or alluvial samples, and concentrations 

of elements detected in rock samples do not differ from

expected crustal abundances. The basalt, andesite, and 

dacite that underlie the area studied could be used for 

construction blocks and rubble. However, these low-unitvalue, high-bulk commodities are available throughout 

Oregon in areas of better access (Barton, 1968, p. 62).

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

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

Richard J. Blakely 

U.S. Geological Survey

Geology

The Spring Basin Wilderness Study Area is located in 

the northwestern part of the Blue Mountains physiographic 

province, about 10 mi south of the adjoining Columbia 

Plateau. In the vicinity of the study area, the Blue Mountains province is characterized by complexly interbedded 

and interfingering Tertiary volcanic rocks that unconformably overlie pre-Tertiary sedimentary and metasedimentary 

basement rocks (Swanson, 1969). The rocks in the region 

are broadly folded and uplifted along northeast trends and 

are only locally faulted. The Columbia Plateau, just to the 

north of the study area, is formed by extensive sequences 

of gently north-tilted Miocene basalt flows of the Columbia 

River Basalt Group (Swanson and others, 1981; Walker, 

1977).

The oldest rocks exposed in the study area (fig. 2) form 

part of the Eocene and lowermost Oligocene(?) age Clarno 

Formation (Walker and Robinson, in press), which was 

originally named and described by Merriam (190la, b). 

The Clarno Formation crops out in nearly the entire study 

area, where it has a maximum exposed thickness of about 

1,700 ft. However, drill hole data from nearby localities 

suggest that the Clarno is at least 3,000 ft thick within the 

study area. The same holes indicate that Mesozoic marine 

sedimentary rocks occur beneath the Clarno Formation. 

Within the study area, the Clarno is divided into two intertonguing subunits, lava flows (including plugs and domes) 

and volcaniclastic rocks.

The lava flows, plugs, and domes range in composition 

from basalt to dacite, although most appear to be andesite. 

They commonly display columnar cooling joints and typically form cliffs. Phenocrysts mainly consist of plagioclase, pyroxene, and locally hornblende. Many of the plugs 

and domes are shallow intrusions that both cut and are 

overlain by surrounding Clarno rocks. Most of the more 

resistant rocky buttes and hills in and near the study area, 

such as Sheep Mountain and Black Rock, are probably 

intrusive plugs (Taylor, 1960) of the Clarno. Locally the 

lava flows include layers and lenses of breccia (including 

flow breccia) and volcaniclastic and tuffaceous sedimentary

Mineral Resources of the Spring Basin Wilderness Study Area, Wheeler County, Oregon C3
120°2730" 120°2230"

APPROXIMATE BOUNDARY

OF

SPRING BASIN 

WILDERNESS 

STUDY AREA 

(OR-005-009)

L/CAg,Au[R 

L/C Hg [2]A

EXPLANATION

Area of low mineral resource potential (L)

Ag 

Au 

Hg 

0,G

1

2

Figure 2.

Oregon.

Levels of certainty of assessment 

Data only suggest level of potential 

Data give good indication of level of potential

Commodities 

Silver 

Gold 

Mercury 

Oil, Gas

Deposit types

Epithermal precious- and base-metal deposits 

Epithermal mercury deposits

Qc 

Tjd 

Tcf

Tcv

Geologic map units 

Qal Alluvium (Quaternary) 

Colluvium (Quaternary)

John Day Formation (Tertiary) Ash-flow tuffs 

Clarno Formation (Tertiary) Volcanic flows, plugs,

and domes

Clarno Formation (Tertiary) Volcaniclastic rocks 

Contact 

Normal fault Bar and ball on downthrown side

 Claims

1 Crystal Peak claim

2 MEM-CAF claim

3 Unnamed claim

Map showing mineral resource potential and geology of the Spring Basin Wilderness Study Area, Wheeler County,

C4 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
rocks. Most of the clasts in these rocks are lithologically 

identical to the enclosing flows, plugs, and domes.

The volcaniclastic facies of the Clarno Formation 

consist chiefly of andesite mudflow breccia, pyroclastic 

deposits, and minor tuff. A few andesite lavas are interbedded with these rocks. Poorly sorted sedimentary rocks 

composed of clasts of the various volcanic rocks are exposed locally, and at one locality a 150-ft-thick, well-bedded fluvial sequence is exposed. Clasts in this sequence 

reach diameters of several feet and consist almost entirely 

of locally derived basalt, andesite, and dacite. The clasts 

are enclosed in tuffaceous or silt- and clay-rich matrices. 

The volcaniclastic rocks, which form exposures as thick as 

600 ft along the canyon wall of the John Day River near the 

northwest edge of the study area, probably originated as 

volcanic mudflow deposits that descended the steep flanks 

of nearby volcanoes (Taylor, 1960; Swanson, 1969). The 

lava flows of the Clarno Formation may have formed the 

volcanic edifices from which the mudflows were derived.

Welded rhyolite ash-flow tuff and basal nonwelded 

tuffaceous deposits of the John Day Formation unconformably overlie rocks of the Clarno Formation with slight 

angular discordance near the northeast corner of the study 

area (Taylor, 1960; Swanson, 1969; Robinson, 1975). The 

John Day Formation is uppermost Eocene to lower Miocene in age (Robinson and others, in press), and consists of 

intercalated ash-flow tuff, volcaniclastic rocks, and rhyolitic and mafic extrusive and intrusive rocks. The ashflow tuff in the study area is approximately 75 ft thick, 

nonwelded to densely welded, and has a cliff-forming 

upper part. Welded parts of the tuff contain fiamme (flattened pumice) that define a compaction foliation.

Overall, the rocks in the study area dip gently towards 

the northwest (Taylor, 1960; Robinson, 1975). The regional tilt may be an expression of the northwest flank of 

the northeast-trending Blue Mountain anticline, a broad 

regional structure that involves rocks as young as the 

Columbia River Basalt Group (Swanson, 1969). Other 

smaller, more local northeast-trending folds are present a 

few miles north and west of the study area. A few highangle normal faults having apparent displacements as great 

as 400 ft have been delineated in the study area; other faults 

undoubtedly are present. Three of the faults strike northeast subparallel to the nearby Hay Bottom Canyon, suggesting that the canyon has been eroded along another fault. 

Similarly, an east-striking normal fault mapped just west of 

the east-trending Eagle Canyon may extend farther east 

along the canyon.

Uplift and folding in the Blue Mountains province 

began in the Eocene during deposition of the Clarno Formation and continued for the remainder of the Tertiary 

(Fox and Reidel, 1987). Angular unconformities separating 

rocks of the Clarno Formation, John Day Formation, and 

Columbia River Basalt Group in and north of the study area 

(Swanson, 1969; Robinson, 1975) provide evidence that

uplift and tilting continued in the region during the Oligocene and early Miocene. Faulting in the region may have 

been contemporaneous with this deformation and (or) may 

have taken place between about 11 and 3 Ma (million years 

ago), late Miocene and early Pliocene, during deformation 

recognized on the Columbia Plateau (see Bela, 1982, for 

references).

Clarno lava flows and domes in the southeastern part 

of the study area locally contain zones of east-striking, 

calcite veins that reach thicknesses of 2 ft and lesser veins 

and veinlets of silica. Rocks in a small area (less than 0.1 

mi2) surrounding a vein zone 0.5 mi north of Breo Flat have 

undergone pervasive silicification and local argillic alteration. A zone of veins in Eagle Canyon is on trend with the 

east-striking fault just to the west, suggesting that these 

veins are related to an eastward extension of the fault.

Thick, extensive alluvium underlies the flood plain of 

the John Day River adjacent to the west boundary of the 

study area. Toward the study area, the alluvium grades into 

locally thick colluvium near the base of the east wall of the 

river canyon. Smaller amounts of alluvial sand and gravel 

form bars and terraces along the major drainages in the 

study area.

Geochemical Studies

A reconnaissance geochemical investigation of the 

study area was made using samples of rock, stream sediment, and the nonmagnetic fraction of heavy-mineral concentrates from stream sediments. The stream-sediment and 

concentrate samples contain material derived from alluvium and rock units of the drainage basins within the study 

area. Sampled drainage basins range in area from less than 

one to several square miles.

From the study area, 60 rock samples, 29 stream-sediment samples, and 22 heavy-mineral-concentrate samples 

were analyzed for 35 elements by six-step semiquantitative 

emission-spectrographic methods (Crock and others, 1987). 

Additional analyses for arsenic, antimony, bismuth, cadmium, and zinc were made using inductively coupled argon 

plasma-atomic emission spectroscopy (Crock and others, 

1987). Samples were analyzed for gold by an atomicabsorption method (Crock and others, 1987) and a graphite 

furnace/atomic-absorption method that has a lower detection limit of 0.002 ppm (parts per million) (Meier, 1980). 

Analyses for mercury used the atomic absorption method of 

Koirtyohann and Khalil (1976). Five rock and two streamsediment samples were analyzed for fluorine by a specificion electrode method (Crock and others, 1987) and for 

uranium by a fluorometric method (O'Leary and Meier, 

1986). M.J. Malcolm and others (written commun., 1988) 

provided sample locations, complete analytical data, and a 

description of sampling, sample preparation, and analytical 

methods.

Mineral Resources of the Spring Basin Wilderness Study Area, Wheeler County, Oregon C5
Analyses of stream-sediment and heavy-mineral-concentrate samples are used to identify drainages that have 

anomalously high concentrations of metallic and metalrelated elements. Rock samples were collected from areas 

of altered bedrock and from each lithologic unit to obtain 

information on trace-element signatures associated with 

potentially mineralized areas and to provide data on background trace-element concentrations. For this study, 

anomalous geochemical values are considered to be those 

that exceed by a factor of two to three the mean concentration in local andesites, the dominant rock type in the study 

area.

A group of multiple-element, low-level geochemical 

anomalies delineates a part of the study area that was 

subjected to hydrothermal alteration and perhaps mineralization. This anomalous area surrounds an altered dacite 

plug located in the easternmost part of the study area, 0.5 

mi north of Breo Flat and 1 mi southeast of Sheep Mountain. The dacite and some of the surrounding rock have 

been variously altered, bleached, silicified, and (or), in a 

few locations, stained by iron oxides. Of 11 rock samples 

collected in this area, 6 are anomalously high in one or 

more elements; 5 of 7 stream-sediment samples from the 

area are similarly anomalous. Elements found in anomalous concentrations are gold, mercury, arsenic, and molybdenum. Of the six rocks having geochemical anomalies, 

one contains an anomalous concentration of gold (0.009 

ppm ), six contain mercury (0.14 to 0.52 ppm), three contain arsenic (5 to 34 ppm), and one contains molybdenum 

(5 ppm). Of the five stream-sediment samples having 

geochemical anomalies, the sample with the strongest 

anomaly contains 0.035 ppm gold, 0.30 ppm mercury, and 

44 ppm arsenic. Two other stream-sediment samples 

contain 0.005 and 0.004 ppm gold, two contain 0.16 ppm 

mercury, and two contain 7 and 6 ppm arsenic.

An additional rock sample, collected at Sheep Mountain about 1/2 mi north of the study area boundary and 

about 1 mi northwest of this anomalous area, has similarly 

anomalous geochemistry (24 ppm arsenic, 7 ppm molybdenum, and 3 ppm antimony). Sheep Mountain is another 

andesite or dacite plug that may have undergone hydrothermal alteration similar to that in the part of the study area 

near Breo Flat.

Anomalously high values for mercury, arsenic, molybdenum, and antimony are among those often associated 

with epithermal mercury mineralization (Rytuba and 

Glanzman, 1979) or epithermal silver-gold-base-metal mineralization (Bonham, 1984; Bonham and Giles, 1983), 

both of which tend to occur in silicic volcanic or related 

host rocks. Important mineral deposits of these two types 

are usually associated with the complex structures, including domes and plugs, found in volcanic eruptive centers 

(Berger, 1982).

In the central part of the study area, a zone of weak 

hydrothermal alteration is indicated by geochemical

anomalies in three of the eight rock samples collected for 

this study from within the zone. Two samples have lowlevel mercury anomalies (0.18 and 0.14 ppm) and the third 

contains antimony (3 ppm) and beryllium (7 ppm) in 

slightly anomalous concentrations. An additional rock 

sample collected by the U.S. Bureau of Land Management 

(Davis, 1983) reportedly contains 0.45 ppm mercury and 29 

ppm molybdenum. Of the two rock samples collected for 

this study within 1/8 mi of the sample described by Davis 

(1983), one has only a slightly anomalous mercury content 

(0.14 ppm) and the other is not geochemically anomalous. 

No stream-sediment samples collected in this area have 

geochemical anomalies, but one heavy-mineral-concentrate 

sample contains 50 ppm molybdenum.

In the northernmost part of the study area, a ridge top 

is capped by a thin layer of ash-flow tuff of the John Day 

Formation. The tuff locally is somewhat altered and 

slightly stained with iron oxides. Three rock samples of 

this tuff all have low-level anomalies of boron, beryllium, 

zirconium, yttrium, and lead. No stream-sediment samples 

collected in this area have geochemical anomalies. Ashflow tuffs are frequently enriched in these elements, so, 

although the concentrations in the tuff are greater than the 

surrounding andesites, the values are not actually anomalous. However, one sample does contain 24 ppm arsenic 

and 100 ppm cobalt, concentrations that are anomalous. 

This may indicate that this tuff has been affected by some 

minor hydrothermal alteration or immobilization of these 

elements within the tuff. The tuff and nearby andesites and 

stream sediments were analyzed for fluorine and uranium, 

elements diagnostic of volcanogenic uranium/beryllium 

deposits of the Spor Mountain type (Lindsey, 1982; Cox, 

1983); these analyses indicate low, background concentrations (1.1 ppm or less uranium and 0.01 percent or less 

fluorine). These data contradict the airborne radiometric 

survey mentioned below under "Geophysical Studies" that 

indicated a uranium anomaly in this area (High Life Helicopters, Inc./QEB, Inc., 1981).

In the western one-third of the study area, four of nine 

rock samples collected from andesite flows of the Clarno 

Formation contain somewhat anomalous concentrations of 

chromium, nickel, and vanadium. However, no streamsediment samples collected in this area have geochemical 

anomalies. These elements are concentrated in mafic 

minerals and oxide minerals, which may be more abundant 

than average in these andesites. The anomalies are most 

likely unrelated to alteration or mineral-deposit-forming 

processes because chromium and nickel deposits are only 

known to occur in ultramafic rocks.

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 Spring

C6 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
Basin Wilderness Study Area. The sparsely distributed 

flightlines and ground stations do not permit assessment of 

mineral resource potential at deposit scales except in limited areas directly beneath detailed profiles. The data are 

adequate to address the regional structural and tectonic 

setting of the study area.

Magnetic Data

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, Inc./QEB, Inc., 1981). These data were measured approximately 400 ft above average terrain along east-west 

flightlines spaced approximately 3 mi apart and along 

north-south flightlines spaced approximately 12 mi apart. 

Only three NURE flightlines actually crossed the study 

area. Two of these were directed approximately east-west 

at lat 44° 51' 00" N. and 44° 53' 30" N.; the third was 

directed north-south at long 120° 23' 00" W. The magnetic 

data from the northern east-west profile were unusable, apparently because of magnetometer malfunction.

Magnetic anomalies within the study area are characterized by short wavelengths (800 to 4,000 ft), high amplitudes (400 nanoteslas (nT) peak to trough), and high horizontal gradients (0.1 to 1 nT per ft). Relatively unmetamorphosed volcanic rocks, such as the andesitic lava flows 

and volcaniclastic deposits of the Clarno Formation, commonly have high magnetic susceptibilities and high 

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

short-wavelength magnetic anomalies that commonly obscure anomalies caused by deeper magnetic sources. Some 

of the individual highs and lows along the magnetic profiles may indicate mineralized areas, but more likely they 

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

Gravity Studies

Gravity data from the vicinity of Spring Basin Wilderness Study Area were obtained from the National Geophysical Data Center, National Oceanic and Atmospheric 

Administration, Boulder, Colorado. Closely spaced (approximately 0.5 mi) measurements are available along Pine 

Creek just north of the study area. Elsewhere measurements are scattered at 3- to 6-mi spacing in this region. No 

measurements are available from within the study area. 

The observed gravity data, based on the International 

Gravity Standardization Net datum (Morelli, 1974), were 

reduced to free-air anomalies by using standard formulas 

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

corrections (out to a distance of 100 mi from each station) 

at a standard reduction density of 2.67 g/cm3 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 also include 

contributions from deep-crustal masses that correlate with 

topography in a manner consistent with the concept of 

isostacy. To reduce the effect of deep sources related to 

isostacy, an isostatic residual-gravity map was constructed 

from the Bouguer gravity data. Isostatic residual-gravity 

data were generated by removing a regional gravity field 

from the Bouger gravity data. The regional field was 

computed from a model of the crust-mantle interface that 

assumes Airy-type isostatic compensation (Jachens and 

Griscom, 1985). A regional gravity perspective of the 

setting of the area can be seen on 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 of the area. The 

Spring Basin Wilderness Study Area lies at the southeastern edge of a positive isostatic residual anomaly. The 

anomaly is 20 milligal (mGal) higher than surrounding 

areas and has lateral dimensions of approximately 15 mi 

east-west and 36 mi north-south. A method to locate edges 

of mass concentrations from gravity data (Blakely and 

Simpson, 1986) was applied to this anomaly. Results 

indicate that the study area straddles the southeastern edge 

of this buried mass.

The positive anomaly forms part of a chain of anomalies and gradients that trend northeast through northern 

Oregon. Northeast of the study area, the chain of anomalies is coincident with pre-Cenozoic rocks of the Blue 

Mountain anticline (Walker, 1977). Riddihough and others

(1986) noted that this lineament is on strike with similar 

gravity features in the Klamath Mountains and have suggested that it reflects a pre-Tertiary continental boundary 

extending across this part of Oregon and Washington. The 

continuation of this chain of anomalies to the study area 

suggests that the study area is underlain by similar preCenozoic rocks at shallow depth. The Mesozoic sedimentary rocks encountered in drill holes to the north of the 

study area provide geologic confirmation of this hypothesis.

Radiometric Data

Radiometric data were collected as part of the NURE 

airborne survey discussed earlier (High Life Helicopters, 

Inc./QEB, Inc., 1981). Recordings were made of gammaray flux from radioactive isotopes of potassium, thorium, 

and uranium. Flightlines were approximately 400 ft above 

average terrain and were flown along east-west flightlines 

spaced approximately 3 mi apart and along north-south 

flightlines spaced 12 mi apart. Only three flightlines cross

Mineral Resources of the Spring Basin Wilderness Study Area, Wheeler County, Oregon C7
the study area. A "uranium anomaly" was detected within 

the study area along the north-south profile over the area 

where ash-flow tuff of the John Day Formation caps a 

ridge. The definition of a uranium anomaly is described in 

detail by High Life Helicopters, Inc./QEB, Inc. (1981). In 

summary, anomalous amounts of uranium are expected if 

uranium radiation, thorium radiation, and the ratio of uranium to thorium radiation all exceed specific statistical 

thresholds. One measurement within the uranium anomaly 

showed equivalent uranium radiation four standard deviations above the mean level. Geochemical samples collected from within this area did not contain anomalous 

quantities of uranium, however.

No other anomalous radiation was detected within the 

study area. However, because only three flightlines cross 

the study area and because gamma rays are strongly attenuated by passage through earth materials, the data do not 

preclude the presence of anomalous amounts of radioactive 

elements away from the flightlines or buried a few feet or 

more beneath the ground surface.

Conclusions

The short-wavelength, high-amplitude magnetic 

anomalies observed in low-altitude profiles over the study 

area are typical for this region. They are caused principally 

by lateral variations in abundance and characteristics of 

magnetite in the unmetamorphosed volcanic rocks exposed 

throughout the area. Gravity data neither indicate nor 

preclude the presence of mineralization in this area.

Radiometric data indicate anomalous amounts of uranium radiation within the study area along the 120° 23' W. 

meridian. This uranium anomaly is based on criteria described by High Life Helicopters, Inc./QEB, Inc., (1981). 

The uranium anomaly may indicate the presence of radiometric mineral accumulations, but it should be noted that 

other explanations such as meteorologic effects are possible.

Mineral and Energy Resource Potential 

of the Spring Basin Wilderness Study Area

Mineral Resource Potential

Investigations by the U.S. Geological Survey indicate 

that the easternmost part of the Spring Basin Wilderness 

Study Area has low mineral resource potential, certainty 

level C, for silver and gold in epithermal vein deposits. In 

addition, the same easternmost area has a low mineral 

resource potential, certainty level C, for mercury in epithermal deposits. Near the center of the study area, a small 

area also has low mineral resource potential, certainty level 

C, for mercury in epithermal deposits. The northern part of 

the study area has no mineral resource potential, certainty

level D, for uranium in volcanogenic deposits. (See appendixes for definitions of levels of mineral resource potential 

and certainty of assessment.)

In the easternmost part of the study area, the altered 

dacite dome and surrounding area has low mineral resource 

potential for silver, gold, and mercury. The geologic setting of the area of potential is similar to that of the mines 

and prospects in the Ashwood/Horse Heaven mining district, located between 10 and 15 mi to the west southwest. 

The mines and geology of the district are discussed by 

Libbey and Corcoran (1962), Brooks (1963), Peck (1964), 

and Brooks and Ramp (1968). Two types of mineral 

deposits, Comstock-type epithermal veins and epithermal 

mercury deposits, occur in the district in or near andesiteto-rhyolite domes and plugs that intrude andesites and 

volcanic breccias of the Clarno Formation. The Ashwood 

mine exploited an epithermal vein deposit localized along 

a fault zone in the Clarno Formation. A description of this 

deposit in Libbey and Corcoran (1962) corresponds with 

the Comstock epithermal vein deposit model of Mosier and 

others (1986). This deposit type is mined for silver and 

gold and may produce minor quantities of copper, lead, and 

zinc as by-products. The Ashwood mine produced approximately 300,000 troy oz silver, 3,700 troy oz gold, 

59,000 Ibs copper, and 110,000 Ibs lead between 1899 and 

1964 (Brooks and Ramp, 1968). Igneous plugs are found 

in the immediate area of the Ashwood mine, but it is not 

known if the plugs and this deposit are related. However, 

the Horse Heaven mine and the other mercury mines and 

prospects in the district are almost all hosted by or immediately adjacent to altered plugs of biotite rhyolite. The 

Horse Heaven mine, the largest mercury producer in the 

district, produced 17,214 flasks of mercury between 1934 

and 1958 (Brooks, 1963).

Low-level geochemical anomalies in rock and streamsediment samples are present near the altered dacite dome. 

Although parts of the dome have been bleached, altered, or 

silicified, no direct evidence of ore mineralization was 

observed. However, the presence of low-level mercury 

anomalies, along with arsenic, antimony, and molybdenum 

anomalies, near an altered dome indicates low potential in 

this area for a mercury deposit similar to the Horse Heaven 

deposit The same geochemical anomalies, in conjunction 

with the low-level gold anomalies, could also be faint 

indicators of a precious- and base-metal deposit similar to 

that at the Ashwood mine, hence the low potential for this 

type of deposit. Since the Ashwood deposit may not be 

dome- or plug-related, the proximity of the anomalies to the 

plug here may not be of importance in determining the 

potential for this type of deposit. Because of the intimate 

dome and mercury-deposit relation in the region, the existence of a mercury deposit is considered more likely than 

that of a precious- and base-metal deposit. It is important 

to note as well that volcanic domes and plugs are very 

common in this region (Brooks, 1963; Brooks and Ramp,

C8 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
1968), but that mineral deposits are only known to occur at 

a few.

A small area in the central part of the study area also 

has low potential for mercury in epithermal deposits. This 

potential is assigned solely on the basis of low-level mercury, antimony, and molybdenum anomalies in some of the 

rock and heavy-mineral-concentrate samples collected 

within the area. No evidence of hydrothermal alteration or 

mineralization was found within this area. If such alteration or mineralization is present, it is likely to be localized 

along the fault or fault zone in Hay Bottom Canyon.

The ridge in the north part of the study area that is 

capped by ash-flow tuff of the John Day Formation has no 

mineral resource potential for volcanogenic uranium. The 

NURE flightline that crosses this area gave radiometric 

data that were interpreted as a uranium anomaly (High Life 

Helicopters, Inc./QEB, Inc., 1981), but analyses of the tuff 

and stream sediments within the area indicate only low, 

background concentrations of uranium and related indicator 

elements. Additionally, the geological setting is not favorable for volcanogenic uranium. Volcanogenic uranium 

deposits are closely associated with ring-fractures, shallow 

intrusive rocks, and domes related to calderas (Rytuba and 

Glanzman, 1979; Lindsey, 1982; Cox, 1983). No calderas 

are known to exist in or near the study area.

Small deposits of sand and gravel suitable for construction are present in the study area but are too small to 

constitute a resource. No undiscovered sand and gravel 

resources are likely to be found beyond known deposits. 

The volcanic rocks that underlie the study area could be 

used for construction blocks and rubble, but suitable material is available throughout Oregon in areas of better access.

Energy Resource Potential

Investigations by the U.S. Geological Survey indicate 

that the Spring Basin Wilderness Study Area has low resource potential for oil and natural gas, certainty level B. 

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

Central Oregon has been explored for oil since the late 

1920'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 the 

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 thick Cenozoic volcanic 

cover causes difficulty in the interpretation of geophysical 

data (Newton, 1974). Additionally, the region is structurally complex and has Cenozoic structures that differ from 

underlying Mesozoic structures. Little is known about preMesozoic structures.

The primary petroleum exploration targets in central 

Oregon have been within two Cretaceous basins (Newton,

1968; Fritts and Fisk, 1985a, b). The larger and older of 

the basins is the Columbia River Basin of mid- to Late 

Cretaceous age (Newton, 1966, 1977; Fritts and Fisk, 

1985a, b). The study area is in the western part of this 

basin (Fritts and Fisk, 1985a, b). The smaller and slightly 

younger (latest Cretaceous) Ochoco Basin lies to the south 

and probably does not extend as far north as the study area 

(Thompson and others, 1984).

Oil and gas leases cover approximately 23 percent of 

the study area. Three deep test holes were drilled near the 

study area between 1929 and 1957, two near Clarno (3 to 

4 mi to the northwest; fig. 1) and one near Condon (26 mi 

to the northeast). Of the two wells near Clarno, the most 

detailed analysis available is on the Oregon Petroleum 

Company's Clarno No. 1. The hole was drilled in 1957 to 

a total depth of 4,340 ft, passing through volcanic tuffs and 

minor interbeds of shale and argillite of the John Day and 

(or) Clarno Formations (0-3,280 ft) and into pre-Tertiary 

shales and argillites (3,280-4,340 ft). Some graywacke 

was present toward the bottom of the hole. No oil or gas 

shows were reported from this hole. The other hole near 

Clarno, the Clarno Basin Oil Company's Burgess No. 2, 

had a gas show, presumably from Cretaceous rocks. 

Asphalt-bearing geodes have also been found near Clarno 

(Collier, 1914; Buwalda, 1921). Well logs and other records for all holes are on file at the Oregon Department of 

Geology and Mineral Industries in Portland, Oregon.

Brown and Ruth Laboratories, Inc. (1983a) conducted 

a detailed geochemical survey of the Clarno No. 1 hole to 

determine source-rock potential of the formations encountered. The results indicate low source-rock potential on the 

basis of low kerogen contents (kerogen is the organic precursor to oil and gas) and low hydrogen indexes, despite 

average to locally high total organic carbon contents 

(TOC). From visual analysis and comparison of hydrogen 

indexes to oxygen indexes, the kerogen in the rocks was 

determined to be type III, indicating a definite terrestrial 

kerogen source. This means that if these rocks produced 

any hydrocarbons, the products would be in the form of 

natural gas. Thermal maturation data from the hole are 

unusual, showing that rocks are thermally immature at 

1,000 ft, increasing to moderately mature at 2,500 ft 

However, thermal maturation increases abruptly at approximately the 2,500 ft depth, and rocks below this level are 

post-mature. Brown and Ruth Laboratories, Inc. (1983a) 

suggests that the 2,500-ft depth marks the Cretaceous-Tertiary boundary, inferring that the sharp change in thermal 

maturity indicates that a thermal event occurred before 

deposition of the Tertiary rocks. Sharp increases in thermal 

maturity could also be due to either heat from local intrusions (Fox and Reidel, 1987) or heat from geothermal 

systems (Summer and Verosub, 1987a).

Fritts and Fisk (1985a, b) and Fisk (written commun., 

1987) propose the existence in central Oregon of organicrich Tertiary rocks (Herren unit) that overlie the Mesozoic

Mineral Resources of the Spring Basin Wilderness Study Area, Wheeler County, Oregon C9
rocks and underlie the Tertiary Clarno Formation. Lithologic descriptions of the Clarno No. 1 hole give little indication of such a formation, but the mention of minor tuffaceous sandstone and the slight increase in kerogen content (S2) and hydrogen index between depths of 2,200 and 

2,500 ft may be slim evidence of such a formation. 

However, geochemical analyses from this section of the 

hole (Brown and Ruth Laboratories, Inc., 1983a) indicate 

only marginally better source-rock potential for these rocks.

The other well-studied and documented hole in the 

region is Standard Oil Company's Kirkpatrick No. 1, 26 mi 

northeast of the study area. From the surface, this hole 

penetrated the Columbia River Basalt Group (0-2,440 ft) 

then passed through volcanic and sedimentary rocks of the 

John Day and (or) Clarno Formations (2,440-6,135 ft). 

These rocks have no source-rock potential in this hole. The 

interval from 6,695 ft to the bottom of the hole at 8,726 ft 

was through Mesozoic sedimentary rocks, primarily argillite but including some graywacke and siltstone (Fox and 

Reidel, 1987). Although the Mesozoic sedimentary rocks 

are thermally mature (Newton, 1979; Summer and Verosub, 1987b), the total organic content of these rocks is low 

to very low (Brown and Ruth Laboratories, 1983b; Fox and 

Reidel, 1987). Most of the organic material present is of 

terrestrial origin and is hydrogen poor and gas prone 

(Brown and Ruth Laboratories, 1983b).

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

the wilderness study area is similar to that in the Oregon 

Petroleum Company's Clarno No. 1 hole. The study area 

does lie within the Cretaceous Columbia River Basin. The 

Mesozoic rocks are primarily argillite but include some 

graywacke and siltstone, lithologies usually having low 

porosity, thereby limiting their potential as reservoir rocks. 

Geochemistry indicates their lack of potential as source 

rocks. The Mesozoic rocks have been determined to be 

thermally post-mature.

Tertiary rocks encountered in the hole are also unlikely 

to be either good source or reservoir rocks. Most of the 

Tertiary section is composed of volcanic tuffs, which have 

no potential as source rocks. The volcaniclastic and sedimentary rocks within the section have low total organic 

contents, are mostly thermally immature, and are gas prone. 

Suitable reservoir rocks are also unlikely to occur beneath 

the study area. In rare instances, volcanic tuffs are known 

to form reservoir rocks (Bortz and Murray, 1979; Duey, 

1979), but the poorly sorted volcaniclastic rocks are unlikely reservoir rocks. The sparsely distributed sedimentary 

rocks are primarily shale and argillite, rocks that usually 

have poor porosity and are therefore not good reservoir 

rocks. Clarno-age magmatism may have produced intense 

local heating, thereby degrading or driving off nearby 

hydrocarbons from both Tertiary and pre-Tertiary rocks.

Fouch (1983) rated the study area as having low potential for oil and gas. Fox and Reidel (1987) considered the

area around the Standard Kirkpatrick No. 1 well to have 

"marginal hydrocarbon potential." However, Davis (1983) 

considered the study area to have moderate potential for 

hydrocarbons. Given the lack of both suitable source and 

reservoir rocks in drill holes and the possible local overheating, the likelihood of the occurrence of oil and gas in 

the study area is small, and so, under the definitions used 

in this study, the area is given a low resource potential for 

oil and gas. A certainty level of B is assigned because of 

the absence of any subsurface data, either seismic or drill 

hole, from within the study area. The stratigraphy in the 

nearest drill holes may differ from that of the study area, 

and more favorable source and reservoir rocks could exist 

beneath the study area. The lack of available seismic data 

precludes any knowledge of pre-Clarno structure or potential traps beneath the study area.

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

hot springs 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).

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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, v. 41, no. 4, p. 63-64. 

O'Leary, R.M., and Meier, A.L., 1986, Analytical methods used

in geochemical exploration, 1984: U.S. Geological Survey

Circular 948, p. 42-44. 

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:

Mineral Resources of the Spring Basin Wilderness Study Area, Wheeler County, Oregon C11
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, scale 1:500,000.

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.

Robinson, P.T., Walker, G.W., and McKee, E.H., in press, Eocene(?), Oligocene, and lower Miocene rocks of the Blue 

Mountains region, in Walker, G.W., ed., Cenozoic geology 

of the Blue Mountains region: U.S. Geological Survey 

Professional Paper 1437, _p.

Rytuba, J.J., and Glanzman, R.K., 1979, Relation of mercury, 

uranium, and lithium deposits to the McDermitt caldera 

complex, Nevada-Oregon, in Ridge, J.D., ed., Papers on 

mineral deposits of western North America: Nevada Bureau 

of Mines and Geology Report 33, p. 109-117.

Strahler, Arthur, 1969, Physical geography: New York, John 

Wiley and Sons, Inc., p. 219-238.

Summer, N.S., and Verosub, K.L., 1987a, Maturation anomalies 

in sediments underlying thick volcanic strata, Oregon: evidence for a thermal event: Geology, v. 15 , no. 1, p. 30-33.

____ 1987b, 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.

Taylor, E.M., 1960, Geology of the Clarno basin, Mitchell quadrangle, Oregon: Corvallis, Oregon State University, M.S. 

thesis, 173 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, G.G., Yett, J.R., and Green, K.F., 1984, Subsurface 

stratigraphy of the Ochoco Basin, Oregon: Oregon Department of Geology and Mineral Industries Oil and Gas Investigation OGI-8, 22 p., 7 pi.

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, 5 p.

Walker, G.W., 1977, Geologic map of Oregon east of the 121st 

meridian: U.S. Geological Survey Miscellaneous Investigations Map 1-902, 2 sheets, scale 1:500,000.

Walker, G.W., and Robinson, P.T., in press, Paleocene(?), Eocene, and Oligocene(?) rocks of the Blue Mountains region, 

in Walker, G.W., ed,, Cenozoic geology of the Blue Mountains region: U.S. Geological Survey Professional Paper 

1437, _p.

Winters, R.A., and Peters, T.J., 1988, Mineral resources of the 

Spring Basin Wilderness Study Area, Wheeler County , Oregon: U.S. Bureau of Mines Open-File Report MLA-04 88, 

13 p.

C12 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
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

LJJ

o

Q_ 

LJJ

U

o

_J

LJJ 

>

A

U/A

i^/i TI i\i TI\-/VV IN rui CIN i i/\i_

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

I/O

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.

C14 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

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 Spring Basin Wilderness Study Area, Wheeler County, Oregon C15
GEOLOGIC TIME CHART

Terms and boundary ages used by the U.S. Geological Survey in this report

EON

Phanerozoic

Proterozoic

pre-Archean2

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Neogene

Subperiod

Tertiary

Paleogene

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Mississippian

Devonian

Silurian

Ordovician

Cambrian

fi Qr\f\7\

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

AGE ESTIMATES OF 

BOUNDARIES IN 

MILLION YEARS (Ma)

0.010

1.7

5

24

3 Q

 55

66

 96 

1 ia

205

~?/in

Z7U

-330

J\J\J

 410

n T r*

JWW

~ J/ \J

 1600

^+J\J\J

JULAJ

J*tlu/V/

 >iccn 

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

informal time term without specific rank.

C16 Mineral Resources of Wilderness Study Areas: John Day Region, Oregon
Mineral Resources of 

Wilderness Study Areas: 

John Day Region, Oregon

This volume was published as separate chapters A-C

U.S. GEOLOGICAL SURVEY BULLETIN 1743
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director
CONTENTS

[Letters designate the separately published chapters]

(A) Mineral Resources of the Lower John Day and Thirtymile Wilderness Study 

Areas, Sherman and Gilliam Counties, Oregon, by Jay A. Ach, Scott A. Minor, 

James G. Frisken, Richard J. Blakely, Harry W. Campbell, and Edward L. 

McHugh.

(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, 

Richard J. Blakely, and Harry W. Campbell.

(C) Mineral Resources of the Spring Basin Wilderness Study Area, Wheeler County, 

Oregon, by Jay A. Ach, Scott A. Minor, James G. Frisken, Richard J. Blakely, 

Richard A. Winters, and Thomas J. Peters.


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