GEOLOGY (Major) (Date) MALHEUR COUNTY, OREGON Redacted for

AN ABSTRACT FOR THE THESIS OF

BRUCE EDWARD ELLISON (Name)

for the

M.S. (Degree)

in GEOLOGY (Major)

presented on

\

11L

(Date)

Title: STRATIGRAPHY OF THE BURNS JUNCTION-ROME AREA,

MALHEUR COUNTY, OREGON

Abstract approved

Redacted for Privacy
KF 01's

Over 2500 feet of Late Tertiary continental volcanic rocks and interbedded sediments are exposed in the Burns Junction-Rome area. The oldest rocks within the area are Miocene andesites which exhibit abundant flow-breccia structure. Lying disconformably on the andesites are spherulitic rhyolite rocks. Disconformably on the rhyolite are Pliocene (?) lower basalts that built up to considerable thicknesses within the area, Younger basalts are thin (25-40 feet) and are associated with fault-controlled cinder cones and vents. All the basaltic rocks examined are of the high-alumina type, generally with a vesicular texture.
Depositional environments represented in the Rome area indude fluvial, shoreline lacustrine, lacustrine and aeolian (?). The sediments are dominantly tuffaceous mudstones, siltstones, and wackes with associated vitric tuffs. Consolidation varies from semi-

to well-consolidated in the Miocene and Pliocene rocks, to generally poorly consolidatd in the Pleistocene units. Lithic pebble conglomerates and pebble to cobble gravels occur as lenses and beds within the sediments. The quartzite, chert, and intruded volcanic lithic clasts indicate a deformed geogynclinal sequence was providing clasts during middle Pliocene and Pleistocene times. Based on 73 cross-bedding measurements the source area for this geosynclinal debris during the middle Pliocene probably was north or west of the Rome area. During the Pleistocene It is believed that the Owyhee River provided quartzite and chert from terrain south of Rome in
Nevada.
Structurally the area is part of the Basin and Range province, although the characteristic block faults so prevalent to the south and west do not occur here0 Gentle folding of the area during the Pliocene and Pleistocene (?) resulted in the development of localized basins which received up to 500 feet of sediments.
Zeolites make up the only economic deposit of potential within the map area. Extensive claims in the LtRome beds't are being maintamed to date by a mineral exploration company.

Stratigraphy of the Burns Junction-Rome Area, Maiheur County, Oregon
by
Bruce Edward Ellison
A THESIS
submitted to Oregon State University
in partial fulfillment of the requirements for the
degree of Master of Science
June 1968

APPROVED:
Redacted for Privacy
ssjate Profelsor of Geology
in charge of major
Redacted for Privacy
Chairman, Department of Geology
Redacted for Privacy
Dean of Graduate Office

Date thesis is presented

/7; ,

Typed by Muriel Davis for Bruce Edward Ellison

ACKNOWLEDGMENTS
The writer wishes to thank the Union Oil Company of California for providing financial assistance to help defray field expenses.
Sincere appreciation is extended to Dr. K.F. Oles, my major professor, for his patience, advice, careful editing of the manuscript and for his field visitation. Special thanks are due to Dr. K. H. Wolf, for his helpful suggestions in the field, and to Robert Clarke of Union Oil Company, for his field visitation. Drs. D. A. Bostwick and H. E. Enlows of Oregon State University critically read the manuscript.
The writer is particularly grateful to his wife, Nancy, whose help and understanding greatly aided in completion of this thesis.

INTRODUCTION TABLE OF CONTENTS

Page

Location and Accessibility

1

Purposes and Methods of Investigation

3

Previous Work

4

Landscape Characteristics

4

Climate

5

STRATIGRAPHY

8

Stratigraphy of Adjacent Areas

8

Thesis Area Stratigraphy

11

Miocene Units

14

Andesite Flows (Taf)

14

Rhyolite Flow (Trf)

16

Pumiceous Volcanic Wacke (Trs)

20

Miocene ('?) - Pijocene Units

24

Rocks of Mafic Vents (Tmv)

24

Scoriaceous Volcanic Wacke (Tvs)

26

Lower Basalt Flows (Tb)

31

Pliocene Units

34

"Rome Beds" (Tst)

34

Lower "Rome Beds"

35

Upper 'tRome Beds"

49

Pliocene-Pleistocene Units

53

Unnamed Sedimentary Rocks (QTs)

53

Intracanyon Basalt Flows (QTba)

57

Pleistocene Units

60

Upper Sediments (Qs)

60

Upper Basalt Flow (Qb)

63

STRUCTURAL GEOLOGY

66

Regional Structure

66

Thesis Area Structure

66

GEOMORPHOLOGY

70

HISTORICAL GEOLOGY

74

ECONOMIC GEOLOGY

78

Zeolites

78

Gravel and Building Stone

79

BIBLIOGRAPHY

80

APPENDICES

83

LIST OF FIGURES

Figure

Page

1 View from eastern map area looking west

6

2 Chart showing stratigraphic sequence of major

units and their map symbols

13

3 Rhyolite flow rocks (Trf) exbiting semi-

circular to vertical jointing

17

4 Fault scarp in scoriaceous volcanic wacke

(Tvs), striking N 80°W

28

S Blocky weathering lower basalts (Tb) dis con-

formably overlain by lower ttRome beds

36

6 Reverse grading and a carbonate concretion

in the lower 'Rome beds

36

7 Siltstone intraclast within a pebble conglomer-

ate in lower ttRome beds"

43

8 Oscillation ripple marks in lower "Rome beds" 43

9 Current rose of cross-beds within lower "Rome

beds"

46

10 Load casts in upper "Rome beds"

51

11 Cutout of upper "Rome beds" by Qs sediments 51

12 Contact between lower "Rome beds" and unnamed

sedimentary rocks (QTs)

56

13 Normal fault in lower "Rome Beds"

69

Plate
1
2

LIST OF PLATES

Page

Index map of Oregon showing location of thesis

area

2

Geologic map of the Burns-Junction-Rome area,

Malheur County, Oregon

in pocket

STRATIGRAPHY OF THE BURNS JUNCTION-ROME AREA, MALHEUR COUNTY, OREGON
INTRODUCTION
Location and Accessibility
The area investigated is located in the Owyhee Upland province of southeastern Oregon, approximately 100 miles southeast of Burns (Plate 1). Steens Mountain lies approximately 40 miles west of the area, and the Owyhee Mountains are 40-50 miles to the east and
southeast. This area includes all of T. 31 S., R. 40 E., secs. 1, 3, 10-15, 19-36, T. 31 5., R. 41 E., and the northern half of T. 32 S., R. 40 E. The small village of Rome is situated along the
north-flowing Owyhee River in the eastern part of the mapped area. Crooked Creek joins the Owyhee River in the northeastern part of the map area.
Year round access to this area is provided by U. S. Highway 95 from the south and the east, and by Oregon State Highway 78 from the northeast. From Rome, graveled secondary county roads pro-. vide access to the northern and eastern parts of T. 31 5., R. 40 E. Elsewhere low relief and scanty vegetation permit access by 4-wheel drive vehicles. As a consequence, hiking distances to any outcrop rarely exceed one-quarter mile.

0

40

80

Miles

20

60

PORTLAND

/
11

CORVALLIS

I:re
BURNS A

Plate 1. Index map of Oregon showing location of thesis area.