' .. 

Petroleum Potential of 

Wilderness Lands in 

Oregon 

By Thomas D. Fouch 

PETROLEUM POTENTIAL OF WILDERNESS LANDS IN THE 

WESTERN UNITED STATES 

GEOLOGICAL SURVEY CIRCULAR 902-J 

This chapter on the petroleum 

geology and resource potential of 

Wilderness Lands in Oregon is 

also provided as an accompanying 

pamphlet for Miscellaneous Investigations Series Map 1-1544 

CONTENTS 

Page 

Abstract---------------------------------------------------------------------- J1 

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

Purpose and methods ----------------------------------------------------------- 1 

Provinces and basins------------------------------------------------------------ 3 

Southwest Oregon pre-Tertiary province----------------------------------------- 3 

Western Oregon Tertiary basin ------------------------------------------------ 3 

Cascade Range province ------------------------------------------------------ 4 

High Plateau province ------------------------------------------------------- 4 

Yakima-Umatilla basin ------------------------------------------------------ 4 

Summary---------------------------------------------------------------------

Referencescited----------------------------------------------------------------

ILLUSTRATION 

4 

4 

Page 

FIGURE 1. Index map showing Oregon Wilderness Lands, geologic provinces, and basins ---------------------------- J2 

III 

PETROlEUM POTENTIAL OF WILDERNESS LANDS IN THE WESTERN UNITED STATES 

Petroleum Potential of Wilderness Lands in Oregon 

By Thomas D. Fouch 

ABSTRACT 

The Wilderness Lands in the State of Oregon cover nearly 

5 million acres and are located across the southwestern, central, and eastern parts of the State. The major areas of concentration of Wilderness Lands are in the region of the Cascade 

Range province and in the central and southeastern portions of 

the High Plateau province. The potential for other than trace 

or show amounts of liquid or gaseous hydrocarbons detected on 

Wilderness Lands in the State is probably quite low. However, 

small tracts of Wilderness Lands in the southeastern part of 

the State may be underlain by nonmarine sedimentary strata 

that have yielded gas shows or have local basins filled with 

sedimentary rock sequences with abundant coaly beds. Although the surface terrane of this province is generally 

covered with volcanic rocks, carbonaceous source beds may underlie or be interbedded with the volcanic units and thus have 

some potential for gas. 

Wilderness Lands of the Cascade Range are generally underlain by rocks not favorable for the formation of oil or gas. 

However, small areas may be underlain by sedimentary units 

that are carbonaceous, but the maturation state of the organic 

matter may be too low to have generated hydrocarbons in 

other than trace amounts. 

In general, geologic factors needed to evaluate the petroleum potential in Oregon are not well known and the State is 

considered a frontier area for exploration. A qualitative assessment of the petroleum potential of the Wilderness Lands in 

Oregon is reported by acreage as follows: a medium potential 

for 138.2 thousand acres; low potential, 2,869. 7 thousand acres; 

and a low to zero potential of 1,857.9 thousand acres. 

INTRODUCTION 

Wilderness Lands in the State of Oregon are located primarily in the region of the Cascade 

Range and in the central and northeastern part of 

the State (fig. 1). A relatively small complex of 

wilderness tracts is located in the southwest part 

of the State near the California border. 

The potential for other than trace or show 

amounts of liquid or gaseous hydrocarbons to be 

detected on Wilderness Lands of the State is 

probably quite low. However, small parts of tracts 

in the southeastern part of the State may be underlain by nonmarine sedimentary strata that 

have yielded gas shows in drill holes or that contain organic matter in surface rocks of adjacent regions. If rocks rich in organic matter occur in the 

Jl 

subsurface of the Wilderness Lands in these areas, 

they may have been subjected to maturation of 

the organic compounds into oil and (or) gas by 

thermal or bacterial action. 

Wilderness Lands of the Cascade Range are 

generally underlain by rocks not favorable for the 

formation of oil or gas. However, small areas may 

be underlain by sedimentary units that are carbonaceous, but the maturation state of much of 

the indigenous organic matter is believed to be too 

low to have generated petroleumlike hydrocarbons 

in other than trace amounts. Near plutonic and 

other igneous bodies, organic matter has been locally metamorphosed to a thermal state too high to 

have preserved petroleumlike hydrocarbons. 

In general, factors needed to evaluate the hydrocarbon potential are not well known and the 

State is considered a frontier area for exploration. 

Drill holes are sparse and the distribution of 

source and reservoir beds in the subsurface of 

the State is very speculative. Although potential 

structural traps are indicated by surface data, 

subsurface traps remain unsubstantiated in the 

absence of numerous drill holes or reflection seismic information. 

PURPOSE AND METHODS 

The purpose of this paper is threefold: (1) to 

present a brief geologic characterization of rocks 

underlying wilderness tracts in Oregon emphasizing those properties that can be related to 

evaluating the potential of the rocks for yielding 

hydrocarbons, (2) to indicate some of the publicly 

available data that can be utilized in assessing the 

petroleum potential of Wilderness Lands, and (3) 

to develop a reconnaissance qualitative assessment of the potential of rocks in Oregon wilderness tracts to yield other than show or trace 

amounts of petroleumlike hydrocarbons. The 

evaluation is based on an assessment of publicly 

available data so that it can be independently 

evaluated. 
N 

t 

2 

SOUTHWEST 

OREGON 

PRE-TERTIARY 

BASIN CASCADE RANGE 

<CD 00 PROVINCE 

All 

I 

s I 

\YAKIMA-UMATILLA// 

~ \ BASIN // 

,...._ __ / 

QJ. 

4 

~~ ~ 

HIGH PLATEAU 

PROVINCE 

, . .... ' 

, ~~ J g 

tJ 

[] 

0 

I 

50 

I 

J 

100 MILES 

I 

EXPLANATION 

PETROLEUM POTENTIAL: 

• Medium ~Low f!i!i!i!i!i!i!ii!i!!ii!iJ Low to zero 

FIGURE 1.-Map of Oregon showing the location of Wilderness Lands. Geologic basin and province boundaries shown are (1) 

Southwest Oregon pre-Tertiary basin, (2) western Oregon Tertiary basin, (3) Cascade Range Province, (4) High Plateau Province, and (5) Yakima-Umatilla basin. 

For purposes of this assessment of Oregon Wilderness Lands, rocks are separated into groups 

with similar geologic properties and assigned 

geographically into five provinces or basins. 

Boundaries among the provinces and basin~ are 

approximately, and in some cases arbitrarily, 

drawn because the areal and subsurface extent of 

many of the defining geologic units is uncertain. 

Of primary concern is the recognition of the presence and character of potential reservoir, source, 

and trapping units for petroleum, the main ingreJ2 

dients of a petroleum province. Because oil and 

gas are recovered only in the northwest part of 

the State, the petroleum potential of frontier nonproductive regions is estimated largely by identifying the presence or absence of organic matter 

in the rocks (i.e., coal, carbonaceous shale, or reports of a fetid odor on freshly broken rock) and 

estimating the level of maturation of the organic 

compounds. Values of coal rank, and vitrinite and 

Rock-Eval data (T. D. Fouch and D. A. Anders, 

1981, unpublished data) provided the principal in-
dices .9f .thennochemical maturation. These indices 

were related "to the major stages of thennochemical maturation of organic matter into oil or gas by 

using data summarized by Bostick (1979). 

A qualitative estimate of the potential of the 

rocks in the wilderness tracts of Oregon to yield 

oil or gas is provided by using the tenns zero, 

low, or medium. Potential is used herein to indicate the expectation of recovering liquid and (or) 

gaseous hydrocarbons in other than trace 

amounts. Expressions of potential, such as low 

and medium are relative to other areas in the 

State of Oregon and may not equate to a similar 

expression of potential in a different hydrocarbon 

province. A map of Oregon has been prepared at 

a scale of 1:1,000,000 that shows the petroleum potential of Oregon's Wilderness Lands (Miscellaneous Investigations Series Map 1-1544, in press). 

PROVINCES AND BASINS 

SOUTHWEST OREGON PRE-TERTIARY PROVINCE 

Basin rocks include Mesozoic and late Paleozoic 

sedimentary, plutonic, and metamorphic units. 

The surface is locally underlain by Paleogene and 

Neogene sedimentary beds that contain carbonaceous organic matter. 

Virtually no literature documents the maturation state of organic matter in pre-Tertiary strata, 

but it is probably too high for stable hydrocarbons. However, coaly material in Neogene and 

late Paleogene rocks of adjacent regions is of a 

low thermal rank and probably has not yielded 

thermally generated gas and (or) oil. As a result, 

it seems reasonable that little or no hydrocarbons 

have originated from the thermal degradation of 

carbonaceous organic matter in the basin. Cretaceous units near the coast offer the only possible exception (Braislin and otl).ers, 1971). 

WESTERN OREGON TERTIARY BASIN 

The surface of the basin is principally underlain 

by Paleogene and Neogene sedimentary rocks 

fonned from sediments deposited in littoral to 

deep marine depositional settings. Basaltic volcanic units that formed on the floor of the Eocene 

ocean are nearly ubiquitous, as are local accumulations of volcaniclastic sedimentary rocks fonned in 

association with the volcanic units. Sedimentary 

J3 

Paleogene clastic units are nonmarine in the 

southern and eastern part of the basin but grade 

to marine beds at variable positions in the central 

and western part of the basin. The Paleogene 

rocks have been variably transported from their 

original site of fonnation by tectonic forces but 

their origin can be approximated. In general, 

west- and northwest-flowing streams transported 

volcaniclastic debris across a coastal plain with a 

well developed wetland plain. Locally impounded 

and slow moving streams accumulated herbaceous 

and woody plant tissue that was subsequently 

transfonned into carbonaceous shale and coal 

beds. Much of the terrestrial organic matter was 

washed from the wetlands into oceanic settings 

and then redistributed by marine currents to sites 

well removed from the coastline. 

Late Eocene and Oligocene rocks indicate that 

streams flowing west from east of the present site 

of the Cascade Range transported micaceous arkosic sand through the ancestral Cascade Range 

to the coastal plain and seaway. This material was 

subsequently redistributed along the western 

edge of the seaway to fonn a complex of arkosic 

sandstone units that extends from at least as far 

south as the central part of the basin north into 

the State of Washington. The arkosic sandstone 

units are exposed in northwest Oregon and have 

been penetrated in drill holes over much of the 

north half of the basin (Newton, 1976). 

Newton (1980) indicates that Eocene beds in the 

south coastal part of the basin contain organic 

matter that originated from woody and herbaceous plants. Some samples contain amorphous organic matter, a type that may yield oil upon maturation. Unpublished Rock-Eval analyses (T. D. 

Fouch, D. A. Anders, B. E. Law, and C. M. 

Molenaar) indicate that most of the organic matter 

in sampled rocks originated from terrestrial 

plants. Sparse analytical data of coal rank and vitrinite and Rock-Eval analyses of the maturity of 

the matter indicate that only locally have exposed 

Paleogene units reached thennochemical maturity. It is reasonable that Paleogene beds have 

been heated to sufficient levels to yield some hydrocarbons in those areas with a thick section of 

younger Paleogene and Neogene strata. Isotopic 

analyses of the gas at Mist field in the north part 

of the basin suggest that the gas originated by 

thennal processes but at a relatively low value of 

maturation for thennal hydrocarbons (D. A. Rice, 

T. D. Fouch, unpublished data). 
CASCADE RANGE PROVINCE 

The area of the Cascade Range is underlain 

principally by volcanic and sedimentary rocks 

(Peck and others, 1964). Very young nonmarine 

sedimentary units that contain organic matter 

were developed in local mountain lakes. Near the 

boundary of the range with the Western Oregon 

basin some Paleogene carbonaceous sedimentary 

units may be present within the Cascade Range 

province, but these rocks are not thought to be 

deeply buried.The ubiquitous presence of volcanic 

rocks and the absence of source, reservoir, and 

trapping units for oil and (or) gas indicate the 

potential of the province is zero. 

HIGH PLATEAU PROVINCE 

Strata of this province are composed primarily 

of Neogene basalt locally intercalated with nonmarine sedimentary rock that contains coaly material. Local basins that formed in Neogene time are 

filled with sedimentary rock sequences with abundant coaly beds. Mesozoic and Paleozoic rocks, 

which are exposed at several localities, locally underlie the Neogene units. Oil shows have been reported in rocks as old as Jurassic (Deacon and 

Benson, 1971). The maturation level of the 

Mesozoic units is not documented, but it is 

thought to be too high in pre-Cretaceous (or 

perhaps pre-Jurassic) beds in most parts of the 

province to have preserved stable hydrocarbons. 

Most pre-Cretaceous rocks of the basin have undergone at least incipient mineral metamorphism. 

Eocene and Oligocene beds locally contain coal of 

a lignitic rank that indicates that these beds could 

only yield gas where buried much more deeply. 

Drill holes that penetrated Neogene strata in 

relatively small local basins have detected gas 

shows (Newton and Corcoran, 1963; Deacon and 

Benson, 1971). However, wilderness tracts in this 

province are not generally located in these areas. 

Those tracts that bound such areas may have a 

higher potential than tracts well removed from 

the thick sequences of Cenozoic sedimentary 

rocks. Although the surface of the province is generally underlain by volcanic rocks, carbonaceous 

source beds may underlie or be interbedded with 

the volcanic units, and thus there is a small potential for gas in the area. 

J4 

YAKIMA-UMATILLA BASIN 

.. ' 

This basin is underlain by Paleogene and N eogene volcanic and sedimentary rocks. Nonmarine 

sedimentary beds of Eocene and Oligocene age, 

which contain coal and carbonaceous matter of low 

thermal rank, are locally developed. Neogene volcanic units are locally intercalated with carbonaceous rock and could yield small quantities of gas in 

drill holes. Older Paleogene and pre-Tertiary 

sedimentary rock may underlie the Neogene units 

but this relation is speculative for most of the 

basin in the absence of drill holes. 

SUMMARY 

Of the 4,865, 739 acres included in this study for 

the assessment of the petroleum potential of the 

Wilderness Lands in Oregon, the potential acreage can be summarized as follows: medium potential, 138.2 thousand acres; low potential, 2,869. 7 

thousand acres; and low to zero potential, 1,857.9 

thousand acres. The petroleum potential by acreage of all Wilderness Land categories in the 

Western United States is shown in this circular 

by B. M. Miller in table 1, chapter P. 

REFERENCES CITED 

Bostick, N. H., 1979, Microscopic measurements of the level of 

catagenesis of solid organic matter in sedimentary rocks to 

aid exploration for petroleum and to determine former burial temperatures-a review, in Scholle, P. A., and 

Schluger, P. R., Aspects of Diagenesis: Society of 

Economic Paleontologists and Mineralogists Special Publication 25, p. 17-44. 

Braislin, D. B., Hastings, D. D., and Snavely, P. D., Jr., 1971, 

Petroleum potential of western Oregon and Washington, 

and adjacent continental margin, in Cram, I. H., ed., Future Petroleum Provinces of the United States-Their 

Geology and Potential: American Association of Petroleum 

Geologists Memoir 15, v. 1, p. 229-238. 

Deacon, R. J., and Benson, G. T., 1971, Oil and gas potential 

of eastern Oregon and Washington and Snake River basin 

of Western Idaho, in Cram, I. H., ed., Future Petroleum 

Provinces of the United States-Their Geology and Potential: American Association of Petroleum Geologists 

Memoir 15, v. 1, p. 355--359. 
NewtOil, Y. C., Jr., 1976, Geology, prospective fold structures, 

and reserV&ir characteristics in the upper Nehalem River 

basin, Oregon, in Newton, V. C., Jr., and Van Atta, R. 

0., eds., Prospects for natural gas production and underground storage of pipe-line gas in the upper Nehalem 

River basin, Columbia-Clatsop Counties, Oregon: State of 

Oregon Department of Geology and Mineral Industries Oil 

and Gas Investigations 5, p. 1-25. 

-- 1980, Geology and oil and gas prospects of the Coos 

Basin, Oregon, in Newton, V. C. Jr., ed., Prospects for oil 

and gas in the Coos Basin, Western Coos, Douglas, and 

Lane Counties, Oregon: State of Oregon Department of 

Geology and Mineral Industries Oil and Gas Investigation 

6, p. 1-15. 

Newton, V. C., Jr., and Corcoran, R. E., 1963, Petroleum 

geology of the western Snake River basin, Oregon-Idaho: 

Oregon Department of Geology and Mineral Industries Oil 

and Gas Investigations 1. 

Peck, D. L., Griggs, A. B., Schlicker, H. G., Wells, F. G., and 

Dole, H. M., 1964, Geology of the central and northern 

parts of the western Cascade Range in Oregon: U. S. 

Geological Survey Professional Paper 449, 56 p. 

J5