~1~~f.~f?Hi51;~«{~Zz{f{~~~}lj\~ Appra1sal Program: Background Information 

~~~~~~~j to Accompany Folio of Geologic, 

~\\\Wii~il*WNi~~~f:~itf~~~~tt~ . . . ~~~l~~!f~Mttth~~~:~~~~~})\~zi:i}}~~ Geochemical, Geophys1cal, and M1neral 

The Conterminous United States Mineral 

Appraisal Program: Background Information 

to Accompany Folio of Geologic, 

Geochemical, Geophysical, and Mineral 

Resource Maps of the Medford -1 ° by 2° 

Quadrangle, Oregon and California 

By James G. Smith, Richard J. Blakely, Maureen G. Johnson, Norn"\r.~n J Page, 

Jocelyn A. Peterson, Donald A. Singer, and Charles l. Whittington 

U . S . G E 0 l 0 G I C A l S U R V E Y C I R C U l A R 97 6 

1986 
Department of the Interior 

DONALD PAUL HODEL, Secretary 

U.S. Geological Survey 

Dallas L. Peck, Director 

Library of Congress Cataloging-in-Publication Data 

The Conterminous United States Mineral Appraisal 

Program. 

U.S. Geological Survey Circular 976 

Bibliography 

Supt. of Docs. no.: I 19.4/2:976 

1. Geology-Oregon-Medford Region. 2. ProspectingOregon-Medford Region. 3. Mines and mineral resourcesOregon-Medford Region. I. Smith, James G., 1939-

II. Conterminous United States Mineral Appraisal 

Program. III. Series. 

TN24.07C66 19 86 557.95'27 86-600072 

Free on application to Distribution Branch, Text Products Section, 

U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 
CONTENTS 

Page 

Abstract ------------------------------------------------------------ 1 

Introduction -------------------------------------------------------- 1 

Location and geography ----------------------------------------- 1 

Previous work -------------------------------------------------- 2 

Present study ~------------------------------------------------- 3 

Geologic map (OF-82-955) -------------------------------------------- 3 

Aeromagnetic map (MF-1383-B) ---------------------------------------- 6 

Mineral-resource assessment maps (MF-1383-C) ------------------------ 6 

Characteristics of lode gold (MF-1383-D) ---------------------------- 7 

Granitic plutons (MF-1383-E) ---------------------------------------- 7 

Probability of mineral exploration (MF-1383-F) ---------------------- 7 

Geochemical studies maps (MF-1383-G, H, I, J, and K) ---------------- 8 

Gravity map (MF-1383-L) --------------------------------------------- 8 

Selected bibliography ----------------------------------------------- 9 

ILLUSTRATION 

Page 

Figure 1. Medford 1° by 2° quadrangle ----------------------------- 2 

TABLE 

Pagn 

Table 1. Contents of Medford 1° by 2° CUSMAP folio ---------------- 4 

III 

The Conterminous United States Mineral Appraisal Program: 

Background Information to Accompany Folio of Geologic, 

Geochemical, Geophysical, and Mineral Resource Maps of the 

Medford 1° by 2° Quadrangle, Oregon and California 

By James G. Smith, Richard J. Blakely, Maureen G. Johnson, Norman J Page, 

Jocelyn A. Peterson, Donald A. Singer, and Charles L. Whittington 

Abstract 

The Medford 1° by 2° quadrangle in southern 

Oregon and northern California was studied by an 

interdisciplinary research team to appraise its 

mineral resources. The appraisal is based on 

geological, geochemical, and geophysical field and 

laboratory investigations, the results of which are 

published as a folio of maps, figures, and tables, 

with accompanying discussions. This circular 

provides background information on the investigations and integrates the information presented in 

the folio. The bibliography lists selected 

references to the geology, geochemistry 

geophysics, and mineral deposits of the Medford 1° 

by 2° quadrangle. 

INTRODUCTION 

This circular, as well as a separately 

published folio of maps, is part of a series of U.S. 

Geological Survey reports that give information 

about the mineral-resource potential of the 

conterminous United States. Both this circular 

and the folio maps were compiled under the 

Conterminous United States Mineral Assessment 

Program (CUSMAP). CUSMAP is intended to 

provide regional mineral appraisal information 

both to assist in the formulation of a long-range 

national minerals policy and to assist Federal, 

State, and local governments in their land-use 

planning. The products of CUSMAP are also 

intended to increase geological, geochemical, and 

geophysical knowledge of the conterminous United 

States. Thus, the program provides a regional 

geologic and mineral-resource framework for 

mineral exploration and for specific studies such 

as the mineral appraisal of wilderness areas. 

Location and geography 

. The M~dfo~ 1° by 2° quadrangle, the 

subJect of this folio, covers approximately 19,000 

1 

km 2 in southern Oregon and northern Crlifornia. 

Less than 2 percent of the quadrangle lie~ within 

California. The quadrangle lies between lat 42° 

and 43° N. and long 122° and 124° W. (fig. 1). 

Most of the quadrangle lies within the Klamath 

Mountains and Cascade Range physbgraphic 

provinces. A small part in the northwest corner of 

the quadrangle is in the Coast Range province, and 

a strip along the eastern border lies within the 

Basin and Range province. Overall the qu1drangle 

is mountainous with rugged relief. E1~vations 

range from about 150 m to nearly 2,80U m, but 

mostly are between 900 m and 1,600 m. The climate is mild and precipitation is heavy, er'>ecially 

during winter storms; as a result, slooes are 

thickly covered with trees and underbrush. 

The major river in the quadrangle is the 

Rogue which, along with its tributaries such as the 

Illinois and Applegate, drains more than two-thirds 

of the quadrangle. Small areas are draine,-:1 by the 

Middle Fork Coquille, South Fork Ump~·ua, and 

Klamath Rivers in the northwest, north--central, 

and eastern parts of the quadrangle, respf'<!tively. 

The main stem of each of these last thre.e rivers 

makes a short loop into the quadrangle. Crater 

Lake and part of upper Klamath Lake lie within 

the quadrangle. Smaller lakes are commcn in the 

Cascade Range; man-made reservoirs are common 

throughout the quadrangle. 

The Medford quadrangle is served by an 

extensive road network. Interstate 5 run-:- generally from southeast to northwest acr0ss the 

quadrangle, and serves all major towns. Other 

federal, state, and county roads generall·? follow 

major streams. The Forest Service, Bt~reau of 

Land Management, and private wood-~>roducts 

companies maintain extensive networks of hardsurfaced and graveled roads throughout forested 

areas. Away from roads, however, movement 

cross country is painfully slow and outcrops few. 

Major towns are Medford, Grants Pass, Ashland, 

Cave Junction, and Canyonville. 
122° 

CRATOR L KE 

Crcoter 

1 ·Lake 0 

NATIONAL 

PARK 

DOUGLAS COUNTY 

\May Creek 

0 10 20 30 KILOMETERS 

• Shale City 

/}_ Hyatt 

Reservoir 

Figure 1. Medford 1° by 2° quadrangle. 

Previous work 

Prior to 1900 few systematic geologic 

studies were made in the area of the Medford 1° 

by 2° quadrangle. J. S. Diller was the first to 

undertake comprehensive studies in this heavily 

wooded and poorly exposed area. His early works 

described the topographic development of the area 

(Diller, 1902), the geology and petrology of Crater 

Lake (Diller and Patton, 1902), and the mineral 

resources of a large portion of the western part of 

the quadrangle (Diller and Kay, 1908, 1909; Diller, 

1914). A later publication described the geology 

and mineral deposits of the 30-minute Riddle 

quadrangle in the northwestern part of the quadrangle (Diller and Kay, 1924). These reports were 

followed by the studies of Frances G. Wells and 

colleagues who systematically examined much of 

the Klamath Mountains during the late 1930's, 

1940's, and early 1950's and published on the 

geology and mineral deposits of the 30-minute 

Grants Pass quadrangle (Wells, 1940), the 30-

minute Kerby quadrangle (Wells, Hotz, and Cater, 

1949), the 15-minute Galice quadrangle (Wells and 

Walker, 1953), and the 30-minute Medford quadrangle (Wells, 1956). 

2 

Early interest in the Cascade Ra""ge part of 

the quadrangle concentrated on th~ geologic 

history of Crater Lake and its precur~or, Mount 

Mazama. In 1942, Howell Williams published his 

classic monograph on Mount Mazama, which 

included an often overlooked geologic reconnaissance along the crest of the range south to Mount 

Shasta (Wiliams, 1942). 

In the early part of this century, the Oregon 

Bureau of Mines and Geology (now the Oregon 

Department of Geology and Mineral Industries) 

began a comprehensive program of deEcribing and 

cataloging geology and development information 

about individual mines and prospects. The data 

were published in series of reports tt''l't covered 

the entire state or individual countier (Winchell, 

1914; Butler and Mitchell, 1916; Parks and 

Swartley, 1916; Oregon Department of Geology 

and Mineral Industries, 1940; 1942; and 1943). This 

program continues to the present witt' the publication of a series of compilations concerning 

specific ore-deposit types (chromite, Eamp, 1961; 

mercury, Brooks, 1963; gold and silver, Brooks and 

Ramp, 1968; nickel, Ramp, 1978), as well as 

revised county reports (Douglas County, Ramp, 

1972; central Jackson County, Be-:.ulieu and 
Hughes, 1977; Josephine County, Ramp and 

Peterson, 1979). 

Topical studies on selected mining districts 

and ore deposit types were conducted by members 

of the U.S. Geological Survey and others; significant among these were the studies by Shenon 

(1933a, b, c) and Lowell (1942) on copper and gold; 

Hotz (1971b) on gold; Wells, Page, and James 

(1940) on chromite; Hundhausen (1952) on coppernickel, Pecora and Hobbs (1942) and Cumberlidge 

and Chace (1968) on nickel, and Derkey (1981) and 

Koski (1981) on massive sulfide deposits. Most of 

the preceding studies concentrated on the 

Paleozoic and Mesozoic rocks in the western part 

of the quadrangle. Only Callagahan and 

Buddington (1938) examined the mineral resources 

of the Cascade Range. 

Recent studies in the western part of the 

quadrangle have focused on bedrock geology and 

its relationship to current plate tectonic models. 

A few theses and areal geology reports also 

discussed other aspects of the geology of the 

Medford 1° by 2° quadrangle and these were 

consulted as part of this study. Work by Harper 

(1980a, b), Jorgenson (1970), Coleman and others 

(1976), Garcia (1976a, b), and Irwin (1977, 1979) 

were particularly useful in our interpretation of 

the geology as well as the reports by Jones (1960), 

Jones and Imlay (1973), Lovell (1969), Kays 

(1970), Elliott (1971), Thoms (1975), Dick (1976), 

Loney and Himmelberg (1976), Miles (1977), Vail 

(1977), Donato and others (1980), Harper (1980b), 

Gray (1982), and Nilsen (1984). 

Recent studies within the Cascade Range 

have concentrated on glacial and volcanic 

geology. Among these are glacial geology along 

the crest, especially in the Mountain Lakes 

Wilderness (Carver, 1972); a reinterpretation of 

the history of Mount Mazama (Bacon, 1983a); the 

history of Mount McLoughlin (Maynard, 1974); 

aerial geology and geochemistry of the Hyatt 

Reservoir and Surveyor Mountain 15-minute 

quadrangles (Naslund, 1977); and tectonic rotation 

of the volcanic rocks of the Western Cascade 

Range (Magill and Cox, 1980). 

Present Study 

The maps and interpretations included in the 

CUSMAP folio of the Medford 1° by 2° quadrangle 

are products of numerous multidisciplinary studies, 

most of them conducted between 1974-1980. The 

study originated as a land-resource analysis 

project that sought to combine modern geologic 

mapping with reinterpretation of existing maps to 

relate mineral resources, regional structure, and 

tectonostratigraphic units with plate tectonic 

models; the project was incorporated in the 

CUSMAP program in 1976. The earlier investigations in the Klamath Mountains, principally those 

by Frances G. Wells and colleagues, were the 

starting point and foundation for compiling the 

3 

geologic map of the Medford 1° by 2° quadrangle. We used many of their original fi~ld notes 

and maps for reinterpretation and compilation 

during the CUSMAP study. We retreived ore 

samples collected during earlier stucies for 

examination and geochemical analysis; mEny were 

from mines no longer active or accessi'">le. In 

many areas new reconnaissance geologic mapping 

was done at a scale of 1:62,500. OutcrC'os were 

examined along rivers, creeks, ridges, and side 

slopes, but especially along the extensive network 

of logging roads that has developed since the early 

investigations. 

The program was integrated with studies of 

wilderness areas in the Klamath Mountains (Page, 

Gray, and others, 1981; Gray and others, 1982) and 

the Cascades (Smith 1983; Smith and Benham, 

1983b). Helicopters were used in support of some 

fieldwork in the wilderness areas and adjacent 

areas. 

The Oregon Department of Geology and 

Mineral Industries, in particular Len RE mp and 

Norm Peterson of the Grants Pass office, cooperated with members of the CUSMAP pr'1ject in 

many stages of geologic investigations. 

The results of the Medford 1° by 2° 

quadrangle CUSMAP program are presented in an 

open-file map and a series of Geological Survey 

Miscellaneous Field Studies Maps (table 1). Other 

maps and reports related to the program are 

indicated by an asterisk in the bibliograpty at the 

end of this report. Mineral-resources dEta have 

been entered into a computer file in the U.S. 

Geological Survey's Mineral-Resourcer Data 

System (MRDS); information about MRDS may be 

obtained from the Regional MRDS Repres"!ntative 

at the U.S. Geological Survey, 12201 Sunrise 

Valley Drive, Reston, VA 22092 or at the U.S. 

Geological Survey, 345 Middlefield Roac\ Menlo 

Park, CA 94025. 

GEOLOGIC MAP 

(OFR 82-955) 

The geologic map of the Medford 1 ° by 2° 

quadrangle is compiled from a combination of new 

reconnaissance geologic mapping and reinterpretation and compilation of previous rapping. 

Selected areas shown in this 1:250,00'1 scale 

compilation (Smith and others, 1982) were also 

published as detailed maps at 1:62,500 scale or 

larger (see Page and others, 1977; Page and others, 

1978; Johnson and Page, 1979; Gray, 1980a; Blair 

and others, 1981; Gray and others, 1981; Page, 

Gray, and others, 1981; Page, Moring, an1 others 

1981; Smith, 1983). 

The geology of the Medford 1° by 2° 

quadrangle is complex, varied, and, unfort·~11ately, 

throughout much of the quadrangle, poorly 

exposed. The western two-thirds of the 

quadrangle is composed of complexly faulted and 

metamorphosed late Paleozoic and early Mesozoic 
Table !.-Contents of the Medford 1° by 2° CUSMAP folio 

[MF, U.S. Geological Survey Miscellaneous Field Studies Map; OF, Open-File Report] 

OF 82-955 Geologic map, by James G. Smith, Norman J Page, Maureen G. Johnson, Barry C. Moring, and 

Floyd Gray 

MF 1383-B Aeromagnetic data and interpretation, by Richard J. Blakely 

MF 1383-c Mineral resource assessment maps, by Donald A. Singer, Norman J Page, James G, Smith,and 

Maureen G. Johnson 

MF 1383-D Characteristics of lode gold, by Norman J Page, Maureen G. Johnson, and Jocelyn A. Peterson 

MF 1383-E Granitic rocks, by Norman J Page, Richard J. Blakely, and Jerome J. Cannon 

MF 1383-F Mineral deposits and mineral exploration, by Roscoe M. Smith and Jocelyn A. Peterron 

MF 1383-G Abundance and distribution of copper in stream-sediment samples, by Charles L. Vhittington, 

David J. Grimes, and Reinhard W. Leinz 

MF 1383-H Abundance and distribution of silver in stream-sediment samples, by Charles L. ~7hittington, 

David J. Grimes, and Reinhard W. Leinz 

MF 1383-1 Abundance and distribution of chromium in stream-sediment samples, by Charles L. 

Whittington, David J. Grimes, and Reinhard W. Leinz 

MF 1383-J Abundance and distribution of arsenic in stream-sediment samples, by Charles L. ~7hittington, 

Reinhard W. Leinz, and David J. Grimes 

MF 1383-K Abundance and distribution of mercury in rock samples, by Charles L. Whittington, Reinhard 

W. Leinz, and David J. Grimes 

MF 1383-L Isostatic residual gravity, by Richard J. Blakely and Lisa Senior 

island-arc volcanic rocks and oceanic ophiolitic 

and ultramafic sequences intruded by later 

Mesozoic granitic plutons. After partial unroofing, the metamorphic and plutonic rocks were 

covered unconformably by Late Cretaceous and 

Paleogene sequences of marine and nonmarine 

sandstone and shale. The eastern one-third of the 

quadrangle is composed of two groups of volcanic 

and volcaniclastic rocks, which together make up 

the Cascade volcanic arc. The older Oligocene 

and Miocene group is composed dominantly of 

volcaniclastic strata and is called the volcanic 

rocks of the Western Cascade Range. The younger 

Pliocene to Holocene group is composed mostly of 

constructional volcanic edifices and is called the 

volcanic rocks of the High Cascade Range. 

The geologic and structural pattern of the 

western two-thirds of the quadrangle is one of 

tectonically juxtaposed terranes that have widely 

different lithologies and preamalgamation geologic 

histories. The terranes consist of (1) low-grade 

metavolcanic and metasedimentary sequences with 

island-arc affinities, (2) broken and dismembered 

mafic and ultramafic sequences with ophiolitic 

affinities, (3) unmetamorphosed graywacke-shale 

sequences that are interpreted to have originated 

as deep-sea fans, (4) true tectonic melanges such 

as those of the Takilma and Dutchman Butte 

areas, (5) a tectonic window of muscovite and 

chlorite schist (the Condrey Mountain Schist), (6) 

high-grade micaceous schists and amphibolite (the 

May Creek Formation, and (7) amphibolite (the 

amphibolite of Briggs Creek of Coleman and 

others, 1976). 

4 

These terranes are separated by northeasttrending structural zones that define tl'~ tectonic 

grain of this part of the quadrangle. Mo-:ot of these 

zones are shallowly to steeply east-dipping thrust 

faults that are commonly marked by dirmembered 

ophiolite sequences. In general, thru~t-bounded 

terranes are successively younger to the west. 

However, within each block stratigraphic 

sequences are generally young in the opposite 

direction to the east. In a general way from east 

to west, the metavolcanic and metasf'<:Hmentary 

rocks of the Applegate Group are thrust westward 

over similar volcanic and sedimentary island arc 

sequences of Jurassic age. These rocks are in turn 

thrust westward over the shales and graywackes of 

the Dothan Formation of Late Jurassic and Early 

Cretaceous age. Each terrane is co'tlposed of 

numerous fault slices that contain coherent, 

distinctive stratigraphic sequences of metavolcanic and metasedimentary rocks. This 

distinctiveness allowed us to reconrtruct the 

stratigraphy of the Paleozoic, Triassic, and 

Jurassic rocks. Previously, most roC''<s in the 

quadrangle were assigned to either the Applegate 

Group or the Rogue or Galice Formations. 

However, the new mapping has made it possible to 

distinguish lithologically distinct sequences in each 

terrane with the resultant reassignment of some of 

these rocks to herein-designated (n~w) rockunits. 

The simplicity of the westward thrusting 

described above is complicated by other periods of 

faulting. Before the westward thrusting took 

place, part of the Josephine ophiolite of Harper 
(1980a and 1980b), in the southwestern part of the 

quadrangle, was thrust northward over the Jurassic 

rocks. After the westward thrusting, northeasttrending faults and rock sequences were broken 

and offset by northwest-trending, steeply dipping 

faults. In addition, a major eastward-trending 

strike-slip fault system cuts across the northern 

part of the quadrangle. Correlation of volcanic 

rocks near Canyonville with those to the west in 

the Wild Rogue Wilderness indicates considerable 

pre-Oligocene strike-slip movement. Offset of a 

prominent 35 m.y. old ash-flow tuff in the Roseburg 1° by 2° quadrangle indicates post-oligocene 

rejuvenation but with dip-slip movement. 

Jurassic and Early Cretaceous granitic 

plutons intruded older thrust-faulted rocks. The 

granitic plutons are discussed and analyzed in 

detail in another part of this folio (MF 1383-E). 

By Late Cretaceous time the rocks of the 

westem part of the quadrangle had been eroded to 

considerable depth, partially unroofing the 

plutons. The Klamath Mountains acted as a local 

source terrane for a thick sequence of shallowwater to deep-water conglomerates, sandstones, 

and shales. Today these homoclinally dipping beds 

are exposed adjacent to interstate highway 1-5 

from the California border to Medford. They 

extend eastward under younger rocks for an 

unknown distance. 

During Eocene time, marine shallow- to 

deep-water sandstones were deposited in the 

northwestern part of the quadrangle. They are 

gently folded and are part of a sequence that 

extends to the northeast in the Oregon Coast 

Range. Near Medford and Ashland, poorly dated 

but approximately correlative nonmarine conglomerate and fluvial sandstone were deposited, the 

source of which was recycled Cretaceous sedimentary and basement rocks of the Klamath 

Mountains. 

The geology of the eastern one-third of the 

Medford quadrangle is dominated by the volcanic 

and volcaniclastic rocks of the Cascade volcanic 

arc. Volcanism began in early Oligocene time as 

fans of volcaniclastic debris spread out over 

Eocene nonmarine sedimentary rocks in the south 

and pre-Tertiary basement rocks in the north. 

Volcanism continued, shifting its locus from place 

to place along the Cascade volcanic arc, until 

approximately 17 Ma. This older sequence is 

called the volcanic rocks of the Western Cascade 

Range. It forms a structurally simple but stratigraphically complex sequence of continental 

volcanic, volcaniclastic, and sedimentary rocks 

about 5,500 m thick. The rocks form an eastnortheast-dipping homoclinal sequence with dips 

ranging from 30° to 5°. Folds, such as those 

mapped by Peck and others (1964) farther north, 

are absent. 

A single, complete, unique stratigraphic 

section of these rocks does not exist. Instead, the 

volcanic rocks of the Western Cascade Range are 

5 

composed of many overlapping and intertonguing 

volcanogenic and sedimentary units. Lithologic 

correlations, even of similar stratigraphic sequences, without corroborating K-Ar ages or 

detailed mapping cannot be trusted. Individual 

beds generally extend from a few kilometers to a 

few tens of kilometers. Rapid facies changes are 

common because as individual emplacement units 

traveled away from vents they thinned, changed 

depositional mode, and, therefore, field appearance. However, units from different, and 

commonly widely separated, volcano~s have 

identical compositions and modes of emplt:tcement 

and look nearly identical. 

For this study, conventional stratigraphic 

formations were neither mapped nor used to 

delineate rock units on the map becaus~~ of the 

stratigraphic problems mentioned above. Rather, 

a dual division based on lithology and t~me was 

used. The rocks were divided into a f£:w broad 

lithologic units that could be mapped in the field 

using reconnaissance methods. Further su'ldivision 

was based on age as determined by K -Ar methods 

and extended by mapping away from K-Ar sample 

sites. Breaks between units were chosen i .... part to 

represent the ages of Wells' (1956) formations as 

determined by K-Ar dating of samples from his 

type localities. 

There is no documented volcanism within the 

Medford 1° by 2° quadrangle between 15 m.y. and 

about 7 m.y. ago. During that time the volcanic 

rocks of the Western Cascade Range wer£: slightly 

uplifted, tilted eastward, and eroded. On this 

eroded landscape, carved into the volcar;c rocks 

of the Western Cascade Range, renewed eruption, 

starting about 7 m.y. ago and continuinrr to the 

present day, built the constructional volcanic 

edifices of the volcanic rocks of the High Cascade 

Range. 

The volcanic rocks of the High Cascade 

Range consist of spectacular andesite stratovolcanoes interspersed with less prominent basalt 

and basaltic andesite shield volcanoe~7 small 

generally monogenetic volcanoes of basalt, 

basaltic andesite, or andesite, extensive. valleyfilling flows, and cinder cones. Constr~1ctional 

volcanic landforms predominate, althougl; stream 

erosion and glacial action have conrtderably 

modified the symmetrical shapes of old£:r volcanoes. Unlike the volcanic rocks of the Western 

Cascade Range, even the oldest volcano£:"-: in this 

group have not been tilted. The products of 

individual volcanoes piled up around vents, or in 

the case of the more fluid lavas, flowed downhill 

filling streams and low areas between adjacent 

volcanoes. 

The volcanic rocks of the High Cascade 

Range in the quadrangle are from volcar0es that 

formed mostly 3.5-0.5 Ma, based on K-Ar ages and 

magnetic polarity measurments. More than threefourths of the individually mapped volcanic units 

formed during this time. 
AEROMAGNETIC MAP 

(MF-1383-B) 

Magnetic properties of certain rock types 

often produce explicit magnetic anomalies. For 

example, contacts between magnetic ophiolitic 

rocks and nonmagnetic sedimentary rocks cause 

abrupt aeromagnetic boundaries even though these 

contacts may be buried at depth below the topographic surface. Careful study of aeromagnetic 

data, therefore, can provide insights about the 

subsurface geology and the mineral-resource 

potential. 

The aeromagnetic map (sheet 1 of MF 1383-

B) was compiled from four published surveys by 

machine-contouring the digital representation of 

each survey and photographically splicing the 

resulting contour maps together. In addition, 

magnetic susceptibilities were determined for 163 

samples from various rock types to aid interpretation of the magnetic data. The magnetic 

properties of major rock types in the Medford 1° 

by 2° quadrangle often produce distinctive 

patterns of magnetic anomalies. Eleven 

(magnetic) terranes with distinctive magnetic 

patterns were identified. For example, the 

volcanic rocks of the Cascade Range produced 

scattered, high-amplitude, short-wavelength 

anomalies whereas the ophiolite belts in the 

western part of the map area produced arcuate, 

linear anomalies. Less magnetic terranes, such as 

that underlain by the Dohan Formation, characteristically show subdued anomalies. 

An interpretive map (sheet 2 of MF-1383-B) 

shows approximate boundaries of various rock 

units that have characteristic magnetic 

anomalies. These boundaries, supported in several 

cases by computer modeling experiments, allow 

the interpreter to extrapolate geologic information from known areas into covered or inaccessible 

regions. 

MINERAL-RESOURCE ASSESSMENT MAPS 

(MF-1383-c) 

The mineral-resource assessment consists of 

two maps showing tracts of land delineated by the 

type of mineral deposit that may be present, and a 

text discussing the assessment, figures, and tables 

that contain supporting information and 

references. The text is organized by deposit type 

with a summary description of the characteristics 

of each deposit type followed by a discussion of 

the geology of the Medford quadrangle that guided 

tract delineation for that type, graphical grade 

and tonnage models or a contained metal model 

for each type, and, for a few deposit types, 

estimates of the number of undiscovered or 

unrecognized deposits. 

6 

The tracts were outlined on the bl'!;is of their 

known deposits and the potential for undiscovered 

deposits as inferred from occurrences· in similar 

geologic settings elsewhere. For e;"ample, 12 

tracts were delineated, based on mapp,~d geology, 

as permissive for the occurrence of massive 

sulfide deposits in marine felsic to ill termediate 

volcanic rocks. By integrating geo~ogic, geochemical, and geophysical information1 as well as 

information about the extent and adequacy of past 

exploration and present geologic knovrledge, the 

authors subjectively estimated a r~ percent 

chance of at least one undiscovered dE:oosit, a 50 

percent chance of at least two or mor~ deposits, 

and a 10 percent chance of four or more deposits 

in the quadrangle. The grade-tonnage model for 

this deposit type indicates that about 50 percent 

of the undiscovered deposits will be lar~er than 0.2 

million metric tons and will contain ccnper, zinc, 

silver, gold, and some lead. 

In the same manner, five tracts were 

delineated for massive sulfide deposits in mafic 

volcanic rocks (Cyprus-type deposits). In addition 

to the one known deposit of this tYr~ (TurnerAlbright), an estimate was made of a 10 percent 

chance of two or more Cyprus-type deposits in the 

delineated tracts. Fifty percent of su~h deposits 

contain 1 million metric tons or more with copper, 

zinc, gold, and silver recoverable in mary. 

Widespread alteration identified rlld mapped 

during this program, as well as numerous geochemical anomalies detected, led to delineation of 

eight tracts for epithermal pre~ious-metal 

deposits in the Western Cascades of the Medford 

quadrangle. Significant clustering o~ mercury, 

arsenic, tellurium, antimony, and other elements 

within the altered areas strongly s·.tggest the 

presence of epithermal precious-metrl mineralization. A contained metal model for the deposit 

type indicates that such deposits can have large 

amounts of gold and silver. An estimate was made 

of a 50 percent chance of two or more 

undiscovered deposits in the delineated tracts. 

The nickel-bearing laterite deposit at Nickel 

Mountain near Riddle was the most important 

producer of primary nickel in the U.S. since 1956. 

Numerous other nickel-bearing lateri+es in the 

Medford quadrangle are lower in grade and 

tonnage than laterite deposits that have produced 

or for which capital expenditures have been made 

for production. 

Other metal-bearing mineral resources in the 

Medford quadrangle include placer gold, and small 

tonnage lode deposits containing chromite, 

antimony, mercury, nickel, molybdenu"'l, manganese, or tungsten. Resources of cor 1 at Eden 

Ridge and adjacent Squaw Ridge centered just to 

the west in the Coos Bay 1° by 2° quaorangle, oil 

shale at Shale City, limestone, sand, r-ravel, and 

rock suitable for various industrial and construction purposes exist in the quadrang~e. 
CHARACTERISTICS OF LODE GOLD 

(MF-1383-D) 

The relationships of about 500 lode gold 

occurrences, prospects, and mines that have been 

reported from the Medford 1° by 2° quadrangle 

are analyzed in map, graph, diagram, and table 

form with respect to pertinent geologic and 

economic characteristics. Significant features 

described include the geographic distribution of 

deposits and their relation to geologic and lithologic features, production information, mineralogy 

of the ore and gangue, gold-silver ratios, and 

speculations on possible genetic models for some 

types of deposits. 

Geologic units not associated with precious 

metals in lode gold deposits and probably not 

related to the genesis of the deposits include the 

volcanic rocks of the High Cascade Range, the 

marine and nonmarine sedimentary rocks of 

Tertiary age, and the sedimentary rocks of 

Jurassic and Cretaceous age. Volcanic rocks of 

Jurassic age, rocks of dismembered ophiolite 

sequences of Jurassic age, and volcanic rocks of 

Paleozoic and Triassic age are host to, by far, the 

greatest number of lode gold deposits. Gold has 

been recovered from a variety of genetically 

different deposit types: (1) gossans and oxidized 

parts of volcanogenic massive sulfide deposits and 

as a by-product of copper mining of unoxidized 

ore, (2) gold-quartz-base-metal veins that are the 

feeders of plumbing systems for massive sulfide 

deposits and occur in metavolcanic and metasedimentary rocks, (3) gold-quartz veins unrelated 

to massive sulfide deposits which occur in a 

variety of host rocks, and (4) epithermal vein 

systems in the volcanic rocks of the Western 

Cascade Range. The bulk of the lode gold production came from six mines; the largest, the 

Greenback, had a production of 100,000 oz; 75 

percent of the lode gold deposits produced less 

than 100 oz. The most common mineral 

assemblages are gold, gold-pyrite, and gold-pyritechalcopyrite-galena. Other moderately common 

minerals are arsenopyrite, sphalerite, and telluride 

minerals. Gold-silver ratios average about 3.6 and 

locally zonal patterns of this ratio appear to be 

associated with some of the plutons. 

GRANITIC PLUTONS 

(MF-1383-E) 

The granitic plutons in the Medford 1° by 2° 

quadrangle are analyzed in map, graph, diagram, 

and table form with respect to pertinent geologic, 

geochemical, and geophysical characteristics. 

Signifcant features described include petrographic 

and modal data, age data, geochemical data for 

selected elements, magnetic susceptibility, 

magnetic expression in relation to outcrop pat7 

terns, and relation to a gravity high \\ithin the 

quadrangle. 

Tonalite and quartz diorite are the most 

common phases within granitic plutons, but areas 

of dioritic, monzodioritic, quartz monzodioritic, 

granodioritic, monzonitic, quartz monzo"litic and 

granitic composition also occur. Rock textures 

range from medium- to coarse-grained, hypidiomorphic, inequigranular to equigranular Pith local 

areas of porphyritic textures. Some plutons are 

composite and consist of distinct phas~s. The 

plutons range in age from 143 to 166 Ma based on 

isotopic dating and have contact aureoles that 

locally reach the pyroxene-hornfels facies. 

Magnetic anomalies over the plutons outline both 

the shape of the pluton and the distribution of 

magnetic minerals within it. Pluton~ in the 

quadrangle were divided into classes on the basis 

of their magnetic expression: plutC'rtS that 

produced magnetic anomalies that correspond 

closely with their mapped lateral extent. plutons 

with anomalies that are not associated with 

outcrops, and plutons that produce no anomalies. 

All of the highly magnetic plutons fell within a 

positive gravity anomaly whereas the ~·~akly or 

nonmagnetic plutons were outside of it. 

PROBABILITY OF MINERAL EXPLORATION 

(MF-1383-F) 

MF-1383-F consists of a computer tabulated 

list of 1,428 mines and prospects and four computer-plotted maps of commodities four1 in the 

Medford quadrangle. The maps are organized as 

follows: 

Map I.-Nonmetallic deposits and prospects 

including barite, building stone (granite), clay, 

coal, diatomite, feldspar, gems, gypsum, 

limestone, marble, olivine, petroleum, pumice, 

quartz, and talc. 

Map 2.-Asbestos, chromite, and nickel deposits 

and prospects. 

Map 3.-Metallic mineral deposits and pro~oects of 

antimony, copper, gold, iron, lead, m~~ganese, 

mercury, molybdenum, silver, tungsten, and 

zinc. 

Map 4.-Placer deposits and prospects of gold and 

platinum. 

The list of properties was tabulated 

primarily from the U.S. Geological Survey Mineral 

Resource Data System (MRDS). Tl ~ table 

summarizes information about locatior" name, 

workings, commodities, deposit size, h<lst rock, 

production, reserves, and references for each 

property. Modified versions of these data are 

stored currently in the MRDS system; tl ~ MRDS 

record number is given in the table. Inquiries may 

be addressed to the Regional MRDS 

Representative at the U.S. Geological Survey, 
12201 Sunrise Valley Drive, Reston, VA 22092 or 

at the U.S. Geological Survey, 345 Middlefield 

Road, Menlo Park, CA 94025. Procedures for 

public access can be obtained through either of 

these representatives. 

The probability of exploration for specific 

commodities is illustrated on maps 2 and 3. Each 

outlined area on the map is assigned one of four 

categories for probability of exploration: (1) 

frequent or continuous exploration in areas of 

favorable host rocks or known active or inactive 

deposits and prospects, (2) intermittent exploration in areas of favorable host rocks, but where 

known deposits or prospects are depleted or low 

grade, (3) possible exploration in areas of exposed 

favorable host rocks or host rocks concealed by 

younger rocks but few, if any, known deposits and 

prospects, and (4) unlikely exploration in areas of 

no favorable host rocks for the commodities 

presented on the map. Exploration potential for 

commodities shown on maps 1 and 4 are indicated 

in the marginal texts. 

GEOCHEMICAL STUDIES MAPS 

(MF-1383-G, H, I, J, and K) 

The geochemical maps contain data that 

show the distribution and abundance of selected 

elements and delineate areas with anomalous 

concentrations of these elements. 

Geochemical studies consisted of the 

collection and analysis of 3,146 rock, 1,529 

stream-sediment, 1,529 oxide-residue, and 35 soil 

samples and the compilation and interpretation of 

the analytical data. Sample preparation and 

analysis was carried out in mobile laboratories at 

field camps or in U.S. Geological Survey laboratories in Denver, Colo. Rock samples were 

collected from all major rock types in the quadrangle. These included fresh unaltered rocks for 

determining normal trace elment populations, as 

well as rocks containing visible signs of mineralization or alteration. In preparation for analysis, 

rocks were crushed, split, and ground to 

approximately 0.1 mm in a pulverizer equipped 

with ceramic plates. 

Stream-sediment sampling used a grid 

system in which the quadrangle was divided into 

sampling cells. As far as possible, a sample was 

collected in each cell in all areas containing 

bedrock exposures, generally at the most readily 

accessible site that was considered suitable. 

Preference was given to sampling sma~ flowing 

streams with small drainage basins (5 km or less), 

but dry drainages or larger streams were substituted where necessary. Where possible, the 

sample was collected in the most active part of 

the stream. Samples were air dried and sieved to 

minus 0.18 mm in stainless-steel sieves. Oxide 

residues were prepared from minus 0.18 mm 

stream sediments using an oxalic-acid leach 

8 

(Alminas and Mosier, 1976). In this pro~~dure, the 

sample is boiled with a solution of oxalic acid and 

filtered hot through a fast filter. The filtrate is 

evaporated to dryness, and the resultim; material 

is ignited to an anhydrous residue by heating at 

45 0 °c. The purpose of the procedure is to 

concentrate the soluble iron and mangar~se oxides 

from the sediment along with coprecipitated trace 

metals. 

Soil samples were collected in several areas 

where stream-sediment samples contain?.d anomalous concentrations of one or more elerr~nts. The 

soil samples were air dried and sieved to minus 

0.18 mm in stainless-steel sieves prior to 

analysis. All samples were analyzed for 18 or more 

elements by an emission spectrographi~ method. 

Oxide residues and selected rocks were analyzed 

for arsenic by colorimetry. Most rocks were 

analyzed for mercury by vapor detection techniques. Many rocks were analyzed for gold and 

tellurium by atomic absorption and for platinumgroup metals by a fire-assay emissionspectrographic technique. 

Geochemical data sets were ma.rged and 

manipulated by computers located at the U.S. 

Geological Survey's Computer Centers in Denver, 

Colo., and Menlo Park, Calif. The com'">ined data 

sets, containing multi-element analyses and 

locations of all samples, have been presented in 

open-file reports (Whittington, Grimes, and 

Peterson, 1983; Whittington, Leinz, and Speckman, 

1983). Parts of the data have been used to 

produce the geochemical distribution and abundance plots incorporated into the gE'0chemical 

maps. The elements shown on these maps were 

selected for their pertinence to the delineation of 

areas favorable for the occur:--ence of 

metalliferous mineral deposits. 

GRA Vli'Y MAP 

(MF-1383-L) 

Residual gravity anomalies manifest lateral 

density changes in the upper crust of the earth and 

provide subsurface geologic informatio'"' in rocks 

that contrast in density with their neighbors. 

Published gravity measurements in the ~"edford 1° 

by 2° quadrangle were compiled and sup'1lemented 

by 400 new measurements. Standard methods, 

including a correction for the effect of all terrain 

within 167 km of each station, were used to 

compute complete Bouguer anomaly values for 

each datum. In addition, a regional gr<:>vity field 

was calculated according to an isostrtic model 

(Simpson and others, 1983) and was subtracted 

from each datum. The machine-contom·~ map of 

these residual anomalies (sheet 1 of J.VfF 1383-L) 

provide subsurface geologic informatio'l. Ultramafic bodies within the less-dens~ Dothan 

Formation, for example, usually produce positive 
residual anomalies. A notable exception, however, 

is the Josephine Peridotite; it does not produce a 

large residual gravity anomaly and probably is a 

thin tectonic sheet. 

SBLBCTBD BffiUOGRAPHY 

The plus (+)indicates references cited in this 

report. Asterisk (*) indicates maps or reports of 

the Medford 1° by 2° quadrangle CUSMAP program other than MF 1383-B-L (table 1). 

Additional references to many mining properties 

are contained in a computer file (MRDS). MRDS is 

an acronym for the U.S. Geological Survey's 

Mineral Resource Data System, about which 

additional information may be obtained from the 

following address: U.S. Geological Survey, 920 

National Center, 12201 Sunrise Valley Drive, 

Reston, VA 22092. 

+Alminas, H. V., and Mosier, E. L., 1976, 

Oxalicacid leaching of rock, soil, and 

stream-sediment samples as an anomaly 

accentuation technique: U.S. Geological 

Survey Open-File Report 76-275, 25 p. 

Appling, R. N., Jr., 1958, Manganese deposits of 

southwestern Oregon: U.S. Bureau of Mines 

Report of Investigations 5369, 56 p. 

Bacon, c. R., 1981, Eruptive history of Mount 

Mazama [abs.]: International Association of 

Volcanology and Chemistry of the Earth's 

Interior, Symposium-Arc Volcanism, Tokyo, 

p. 22-23. 

+ 1983a, Eruption history of Mount Mazama, 

--Cascade Range, U.S.A.: Journal of Volcanology and Geothermal Research, v. 18, p. 57-

115. 

1983b, The precursory and climatic eruptions 

--of Mount Mazama and collapse of Crater 

Lake caldera, Oregon [abs.]: Geological 

Society of America, Abstracts with Programs, v. 15, no. 5, p. 330. 

Bacon, C. R., and Lanphere, M. A., 1983, K-Ar 

chronology of eruptions at Mount Mazama 

before the formation of Crater Lake Caldera 

[abs.]: Eos (American Geophysical Union, 

Transactions), v. 64, no. 45, p. 879. 

Baldwin, E. M., 1974, Eocene stratigraphy of 

southwestern Oregon: Oregon Department 

of Geology and Mineral Industries Bulletin 

83, 40 p. 

Baldwin, E. M., Beaulieu, J. D., Ramp, Len, Gray, 

J. J., Newton, V. C., Jr., and Mason, R. S., 

1973, Geology and mineral resources of Coos 

County, Oregon: Oregon Department of 

Geology and Mineral Industries Bulletin 80, 

82 p. 

*Barnard, J. B., Page, N. J, Blakely, R. J., 

Ziemianski, W. P ., Banister, C. A., and 

Giusso, J. R., 1981, Mal) showing distribution 

of serpentine minerals, density, and 

9 

magnetic suscel)tibility of rocks from the 

Kalmiopsis Wilderness, southwestern 

Oregon: U.S. Geological Survey rlliscellaneous Field Studies Map MF-1240-·B, scale 

1:62,500. 

+Beaulieu, J. D., and Hughes, P. W., 1977, Land 

use geology of central Jackson County, 

Oregon: Oregon Del)artment of Geology and 

Mineral Industries Bulletin 94, 87 p. 

Bird, M. L., 1977, Electron-microprobe anc:~lyses of 

chromite and olivine from all)ine ultramafic 

coml)lexes: U.S. Geological Survey O[>enFile Report 77-236, 66 [>., 4 figs. 

Black, G. L., Blackwell, D. D., and Steele, J. L., 

1982, Heat flow of the Oregon Cas~~ades, in 

Priest, G. R., and Vogt, B. F., Geology and 

geothermal resources of the C1scades, 

Oregon: Oregon Del)artment of Gectogy and 

Mineral Industries 0l)en-File Rel)ort 0-82-7, 

Ch. 7, l>· 152-168. 

Blackwell, D. D., Bowen, R. G., Hull, D. A., 

Riccio, Jose[>h, and Steele, J. L., 1982, Heat 

flow, arc volcanism, and subduction in 

northern Oregon: Journal of Geo[>hysical 

Research, v. 87, no. B10, l>· 8735-87f4. 

Blackwell, D. D., Hull, D. A., Bowen, R. G., and 

Steele, J. L., 1978, Heat flow of Oregon: 

Oregon De[>artment of Geology and Mineral 

Industries Sl)ecial Pal)er 4, 42 l>· 

*Blair, W. N., 1978, Radiolarians from Mesozoic 

rocks in western Oregon [abs.], in G~ological 

Survey Research 197 8: U.S~ G~ological 

Survey Professional Pal)er 1100, l>· 78. 

*Blair, W. N., Wong, Albert, Moring, B. C, 

Barnard, J. B., Page, N. J, and Gray, Floyd, 

1981, Reconnaissance geologic mal) of [>arts 

of the Gold Hill, Ruch, Medford, an1 Talent 

15-minute quadrangles, southwestern 

Oregon: U.S. Geological Survey Ci'len-File 

Mal) 81-1076, scale 1:62,500. 

Blakely, R. J., Jachens, R. C., Siml)son, R. W., and 

Couch, R. W ., 1985, Tectonic settirqo of the 

southern Cascade Range as interl)reted from 

its magnetic and gravity fields: Geological 

Society of America Bulletin, v. 96, no. 1, l>· 

43-48. 

Blank, H. R., Jr., 1966, General feature~ of the 

Bouguer gravity field in southwestern 

Oregon, in Geological Survey Research 

1966: U.s:-Geological Survey Professional 

Pal)er 550-c, l>· C113-C119. 

1968, Aeromagnetic and gravity surveys of 

--Crater Lake region, Oregon, in Dole, H. M., 

ed., Andesite Conference Guidebook: 

Oregon Del)artment of Geology and Mineral 

Industries Bulletin 62, p. 42-51. 

Botto, R. 1., and Morrison, G. H., 1976, Josephinite; a unique nickel-iron mineral: American Journal of Science, v. 276, no. ~- p. 241-

274. 

+Brooks, H. c., 1963, Quicksilver in Oregon: 

Oregon Department of Geology and Mineral 
Industries Bulletin 55, 223 p. 

+Brooks, H. C., and Ramp, Len, 1968, Gold and 

silver in Oregon: Oregon Department of 

Geology and Mineral Industries Bulletin 61, 

337 p. 

Burchfiel, B. C., and Davis, G. A., 1972, Structural 

framework and evolution of the southern 

part of the Cordilleran orogen, western 

United States: American Journal of Science, 

v. 272, p. 97-118. 

+Butler, G. M., and Mitchell, G. J., 1916, Preliminary survey of the geology and mineral 

resources of Curry County, Oregon: Oregon 

Bureau of Mines, Mineral Resources of 

Oregon no. 2, 134 p. 

Callaghan, Eugene, and Buddington, A. F., 1933, 

Some features of the volcanic sequence in 

the Cascade Range in Oregon: American 

Geophysical Union Transactions, v. 141, p. 

243-249. 

+ 1938, Metalliferous mineral deposits of the 

--Cascade Range in Oregon: U.S. Geological 

Survey Bulletin 893, 141 p. 

*Carlson, C. A., Page, N. J, and Carlson, R. A., (in 

press), Map showing the distribution of 

platinum-group elements and gold in rocks 

from the western half of the Medford and 

part of the adjacent Coos Bay 1° x 2° 

quadrangles, southwestern Oregon: u.s. 

Geological Survey Miscellaneous Field 

Studies Map MF- , scale 1:250,000. 

*Carlson, C. A., Page, N. J, Grimes, D. J., and 

Leinz, R. W ., 1982, Map showing geochemical characteristics of rock samples 

from the Kalmiopsis Wilderness, southwestern Oregon: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1240-C, 

scale 1:62,500. 

+Carver, G. A., 1972, Glacial geology of the 

Mountain Lakes Wilderness and adjacent 

parts of the Cascade Range, Oregon: 

Seattle, University of Washington, Ph..- D. 

dissertation, 72 p. 

Coleman, R. G., 1967, Low-temperature reaction 

zones and alpine ultramafic rocks of 

California, Oregon, and Washington: u.s. 

Geological Survey Bulletin 1247, 49 p. 

1972, The Colebrooke Schist of southwestern 

--Oregon and its relation to the tectonic 

evolution of the region: U.S. Geological 

Survey Bulletin 1339, 61 p. 

+Coleman, R. G., Garcia, Michael, and Anglin, 

Camille, 1976, The amphibolite of Briggs 

Creek: a tectonic slice of metamorphosed 

oceanic crust in southwestern Oregon? 

[abs.]: Geological Society of America 

Abstracts with Programs, v. 8, no. 3, p. 363. 

Couch, R. W ., Gem perle, Michael, McLain, W. H., 

Connrad, G. G., 1981, Total-field aeromagnetic anomaly map, Cascade Mountain 

Range, southern Oregon: Oregon Department of Geology and Mineral Industries Map 

10 

Series GMS 17, scale 1:250,000. 

Couch, R. W ., Pitts, G. s., Veen, C. A., and 

Gemperle, Michael, 1981, Free-sir gravity 

anomaly map and complete Bouguer gravity 

anomaly map, Cascade Mountain Range, 

southern Oregon: Oregon Depa .. tment of 

Geology and Mineral Industries Map Series 

GMS 16, scale 1:250,000. 

Crandell, D. R., 1965, The glacial history of 

western Washington and Oregon, in Wright, 

H. E., and Frey, D. G., eds., The Quaternary 

of the United States: Princeton, N.J., 

Princeton University Press, p. 341-354. 

+Cumberlidge, J. T., and Chace, F. M., 1968, 

Geology of the Nickel Mount•1in mine, 

Riddle, Oregon, in Ore deposits of the 

United States, 1933-1967 (Grqton-Sales 

Volume), v. 2: New York, American Institute 

of Mining, Metallurgical, and Petroleum 

Engineers, p. 1650-1672. 

+Derkey, R. E., 1981, The Silver Pea~· volcanogenic massive sulfide, northern Klamath 

Mountains, Oregon, in Silberman, M. L., 

Field, c. W ., and Berry, A. L., eds., Proceedings of the symposium or mineral 

deposits of the Pacific Northwest~ Geological Society of America, Cordilleran Section, 

Annual Meeting, Corvallis, Oreg., 1980: U.S. 

Geological Survey Open-File Repo .. t 81-355, 

p. 213-222. 

+Dick, H. J. B., 1976, The origin and emplacement 

of the Josephine Peridotite of southwestern 

Oregon: New Haven, Conn., Yale University, 

Ph. D. dissertation, 445 p. (Di~sertation 

Abstracts International, v. 37, no. 7, 

p. 3311B, 1977). 

1977, Partial melting in the Josephine --=-Peridotite; 1, The effect on mineral 

composition and its consequence for geebarometry and geothermometry: American 

Journal of Science, v. 277, no. 7, p. 801-832. 

1977 Evidence of partial melting in the 

---:J=-osephine Peridotite [abs.], ii1 Magma 

genesis 1977; Proceedings of theAmerican 

Geophysical Union Chapman conference on 

partial melting in the Earth's upp~~ mantle: 

Oregon Department of Geology an1 Mineral 

Industries Bulletin, no. 96, p. 59-62. 

Dick, H. J. B., and Gillete, H., 1976, Josephinite 

specimens from the Earth's core?: Earth and 

Planetary Science Letters, v. 31, no. 2, p. 

308-311. 

Dickinson, W. R., and Vigrass, L. W ., 1964, PreCenozoic history of the Suplee-Ize~ district, 

Oregon: Implications for ge,'>synclinal 

theory: Geological Society of America 

Bulletin, v. 75, p. 1037-1044. 

+Diller, J. s., 1902, Topographic develcoment of 

the Klamath Mountains: U.S. Geological 

Survey Bulletin 196, 69 p. 

+ 1914, Mineral resources of sou~hwestern 

Oregon: U.S. Geological Survey Bulletin 546, 
147 p. 

+Diller, J. S., and Kay, G. F., 1908, Mines of the 

Riddle quadrangle, Oregon: U.S. Geological 

Survey Bulletin 340-A, p. 134-152. 

+ 1909, Mineral resources of the Grants Pass 

--quadrangle and bordering districts, Oregon: 

U.S. Geological Survey Bulletin 380-A, p. 48-

79. 

+ 1924, Riddle quadrangle, Oregon: U.S. 

Geological Survey Geologic Atlas of the 

United States, no. 218, 8 p., 3 maps. 

+Diller, J. S., and Patton, H. B., 1902, The geology 

and petrography of Crater Lake National 

Park: U.s. Geological Survey Professional 

Paper 3, 167 p. 

Dole, H. M., ed., 1968, Andesite conference 

guidebook-International upper mantle 

project science report 16-s: Oregon Department of Geology and Mineral Industries 

Bulletin 62, 107 p. 

+Donato, M. M., Coleman, R. G., and Kays, M. A., 

1980, Geology of the Condrey Mountains 

schist, northern Klamath Mountains, California and Oregon: Oregon Geology, v. 42, 

no. 7, p. 125-129. 

Dott, R. H., Jr., 1971, Geology of the southwestern Oregon coast west of the 124th 

Meridian: Oregon Department of Geology 

and Mineral Industries Bulletin 69, 63 p. 

+Elliott, M. A., 1971, Stratigraphy and petrology 

of the Late Cretaceous rocks near Hilt and 

Hornbrook, Siskiyou County, California, and 

Jackson County, Oregon: Corvallis, Oregon 

State University, Ph. D. dissertation, 171 p. 

Fieblekorn, R. B., Walker, G. W., MacLeod, N. S., 

McKee, E. H., and Smith, J. G., 1983, Index 

to K-Ar age determinations for the state of 

Oregon: Isochron/West, no. 37, p. 3-60. 

+Garcia, M. 0., 1976a, Rogue River Island arc 

complex, western Jurassic belt, Klamath 

Mountains, Oregon, [abs.]: Geological 

Society of America Abstract, v. 8, no. 3, p. 

375. 

+ 1976b, Petrology of the Rogue River area, 

--Klamath Mountains, Oregon: Problems in 

the identification of ancient volcanic arcs: 

Los Angeles, University of California, Ph. D. 

dissertation 185 p. ___ 1979, Petrology of the Rogue and Galice 

Formations, Klamath Mountains, Oregon: 

Identification of a Jurassic island arc 

sequence: Journal of Geology, v. 87, no. 1, 

p. 29-41. 

*Gray, Floyd, 1980a, Geology of the igneous 

complex at Tincup Peak, Kalmiopsis Wilderness area, southwestern Oregon: U.S. 

Geological Survey Open-File Report 80-1243, 

77 p., scale 1:12,000. 

* 1980b, Lherzolitic and wehrlitic rock series at --Tincup Peak, Klamath Mountains, southwestern Oregon [abs.]: Geological Society 

of America Abstracts with Programs, v. 12, 

11 

no. 3, p. 108. 

+* 1982, Geology of the igneous C'lmplex at 

--rri"ncup Peak, Kalmio(:.Sis Wilder11ess Area, 

southwestern Oregon: Amherst, University of 

Massachusetts, M.S. thesis, 135 p. 

*Gray, Floyd, and McKee, E. H., 1981, New K-Ar 

dates from the Wild Rogue Wilderness, 

southwestern Oregon: Isochron/We.st, no. 32, 

p. 27-29. 

*Gray, Floyd, and Miller, M. S., 1983, W~.ld Rogue 

Wilderness, Oregon, in Marst'., S. P., 

Kropschott, S. J., and Dickinson, R. G., 

Wilderness Mineral Potential: Asse"sment of 

mineral-resource potential in U.S. Forest 

Service Lands studied 1964-1984: U.S. 

Geological Survey Professional Psper 1300, 

v. 2, p. 914-916. 

+*Gray, Floyd, Miller, M. S., Gaps, R. S., Peterson, 

J. A., Blakely, R. J., and Senior, Lisa, 1982, 

Mineral resource potential map of the Wild 

Rogue Wilderness, Coos and Curry Counties, 

Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-1381-D, scale 

1:48,000. 

*Gray, Floyd, and Peterson, J. ! ,, 1982, 

Geochemical analyses of rock and streamsediment samples from the Wild Rogue 

Wilderness Area, Coos, Curry, and Douglas 

Counties, Oregon: U.S. Geologic,'ll Survey 

Open-File Report 82-186, scale 1:~ij,OOO, 24 

p. 

*Gray, Floyd, Ramp, Len, Moring, B. c., Douglas, 

Ian, Donahoe, J. L., 1981, Geologin. map of 

the Wild Rogue Wilderness, Coos, Curry, and 

Douglas Counties, Oregon: U.S. c:·~ological 

Survey Miscellaneous Field Stucies Map 

MF-1381-A, scale 1:48,000. 

Hammond, P. E., 1983, Volcanic formatbns along 

the Klamath river near Copc':l Lake: 

California Geology, v. 36, no. 5, p. f~l-109. 

+Harper, G. D., 1980a, The Josephine O?hioliteremains of a Late Jurassic marginal basin in 

northwestern California: Geology, v. 8, no. 

7' p. 333-337 0 

+ __ 1980b, Structure and petrology of the Josephine Ophiolite and overlying metasedimentary 

rocks, northwestern California: Berkeley, 

University of California, Ph. D. disr~rtation, 

281 p. 

Hotz, P. E., 1971a, Plutonic rocks of the Klamath 

Mountains, California and Oregon: U.S. 

Geological Survey Professional Pr~;>er 684-

B, 20 p. 

+ 1971b, Geology of lode gold districts in the 

--Klamath Mountains, California and Oregon: 

U.S. Geological Survey Bulletin 129f- 91 p. 

+Hundhausen, R. J., 1952, Investigation of 

Shamrock copper-nickel mine, Jackson 

County, Oregon: U.S. Bureau of Mines 

Report of Investigations 4895, 12 p. 

Imlay, R. W ., Dole, H. M., Wells, F. G., end Peck, 

Dallas, 1959, Relations of certain Upper 
Jurassic and Lower Cretaceous formations in 

southwestern Oregon: American Association 

of Petroleum Geologists Bulletin, v. 43, 

no. 12, p. 2770-2785. 

Irwin, W. P., 1964, Late Mesozoic orogenies in the 

ultramafic belts of northwestern California 

and southwestern Oregon, in Geological 

Survey Research 1964: U.§:"" Geological 

Survey Professional Paper 501-C, p. C1-C9. ___ 1973, Sequential minimum ages of oceanic 

crust in accreted tectonic plates of Northern 

California and Southern Oregon [abs.]: 

Geological Society of America Abstracts 

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12 

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15 

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GPO 687-049/45016