Geology of the Blue Mountains Region 

of Oregon, Idaho, and Washington 

Geologic hnplications of Paleozoic and Mesozoic 

Paleontology and Biostratigraphy, 

Blue Mountains Province, 

Oregon and Idaho 

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1435 
Geology of the Blue Mountains Region 

of Oregon, Idaho, and Washington 

Geologic Implications of Paleozoic and Mesozoic 

Paleontology and Biostratigraphy, 

Blue Mountains Province, 

Oregon and Idaho 

TRACY L. VALLIER and HOWARD C. BROOKS, editors 

U.S. GEOLOGICi\L SURVEY PROFESSIONAL PAPER 1435 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1986 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Library of Congress Cataloging-in-Publication Data 

Geologic implications of Paleozoic and Mesozoic paleontology and biostratigraphy, Blue Mountains province, Oregon and 

Idaho. 

(U.S. Geological Survey Professional Paper 1435. Geology of the Blue Mountains region of Oregon, Idaho, and Washington.) 

Bibliography included. 

Supt. ofDocs. no.: I 19.16: 1435 

1. Geology-Blue Mountains (Oreg. and Wash.) 2. Geology-Blue Mountains Region (Oreg. and Wash.) 

3. Geology-Idaho. 4. Paleontology-Blue Mountains Region (Oreg. and Wash.) 5. Paleontology-Idaho. 

I. Vallier, T. L. (Tracy L.) II. Brooks, Howard C. III. Series: Geological Survey Professional Paper 1435. 

QE156.B57G46 1986 557.95'7 86-600005 

For sale by the Books and Open-File Reports Section, 

U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 
PREFACE 

This U.S. Geological Survey Professional Paper is 

one volume of a series that focuses on the geology, 

paleontology, and mineral resources of eastern Oregon, 

western Idaho, and southeastern Washington. The purpose of this series is to familiarize readers with the work 

that has been completed in the Blue Mountains region 

and to emphasize the region's importance for understanding island-arc processes and the accretion of an 

allochthonous terrane. These professional papers 

provide current interpretations of a complex island-arc 

terrane that was accreted to ancient North America in 

the late Mesozoic Era, of a large batholith that was 

intruded after accretion had occurred, and of overlying 

Cenozoic volcanic rocks that were subsequently uplifted 

and partly stripped off the older rocks by erosion. 

Modern island arcs are not well understood, and 

even less so are ancient arcs that have been deformed, 

metamorphosed, and subsequently accreted to continents. We have learned that characteristics of modern 

arcs change significantly both along and across the arcs' 

axes, and that studies of arc fragments are less than 

satisfactory because they generally do not characterize 

an entire arc. For example, the landward trench slopes 

of arcs can differ greatly, depending on whether materials from the descending slab are being accreted or the 

slope is being tectonically eroded; which process dominates apparently is related to the volume of sediment in 

the adjacent trench and the vector of plate convergence. 

In addition, some arcs (Aleutian) have broad, long, and 

sediment-filled forearc basins, whereas in others 

(Tonga-Kermadec) the forearc insular slopes descend 

precipitously to trench depths and are only interrupted 

in places by narrow fault-bounded terraces. Moreover, 

some arcs have erupted primarily tholeiitic igneous 

products throughout their histories (Tonga-Kermadec) 

and others (Aleutian) have a long history of both calcalkaline and tholeiitic eruptive activity. Ridge axes of 

the arcs may be narrow or broad, and in some arcs 

(Solomons and Vanuatu) the axial regions have 

extended to form deep bathymetric and sedimentary 

basins. Even back-arc basins may have different origins 

and histories of development. Some (Mariana Trough 

and Lau Basin) have active spreading ridges, whereas 

others (Aleutian basin of the Bering Sea) are floored by 

ancient oceanic crust that was trapped behind the arc. 

Because our knowledge of the diverse processes 

within modern arcs is limited, it becomes even more 

important to study ancient analogues. Just by the 

nature of their on-land exposures, ancient arcs can 

provide insights into sedimentary facies, magmatic evolution, and deep crustal processes that can only be studied in modern arcs by geophysical methods, dredging, 

and drilling. Few ancient island arcs have exposures as 

well developed and as extensive as those in the Blue 

Mountains province. Particularly spectacular and helpful are outcrops provided by intensive stream erosion, 

which has left some canyon walls more than 2 km deep 

(Snake River Canyon west of the Seven Devils Mountains). 

Most earth scientists who have worked in the Blue 

Mountains region agree that the pre-Tertiary rocks 

there form one or more allochthonous terranes. The 

importance of such terranes in the evolution of circumPacific continental margins has been recognized for 

about a decade, but many complex questions remain. 

For example, how, when, and where did most of the 

circum-Pacific allochthonous terranes form? How did 

they accrete to continents? What are the mechanisms of 

amalgamation processes during terrane formation and 

transport? And, perhaps most importantly, what are the 

effects of these processes on mineral and hydrocarbon 

resources? While these volumes provide some answers, 

the data and interpretations contained in them will no 

doubt raise new and equally intriguing questions for 

future generations of earth scientists. 

III 

CONTENTS 

[Numbers designat e t he cha pters] 

1. Paleozoic and Mesozoic faunas of the Blue Mountains province: a review of their geologic implications 

and comments on papers in the volume 

Tracy L. Vallier and Howard C. Brooks ---------------------------------------------------------

2. Late Triassic bivalves of the Martin Bridge Limestone, Hells Canyon, Oregon: taphonomy, paleoecology, 

paleozoogeography 

CathrynR. ~ewton --------------------------------------------------------------------------

3. Late Triassic coelenterate faunas of western Idaho and northeastern Oregon: implications for 

biostratigraphy and paleogeography 

Page 

1 

7 

George D. Stanle~J~ ------------------------------------------------------------------------23 

4. A ~orian (Late Triassic) ichthyosaur from the Martin Bridge Limestone, Wallowa Mountains, Oregon 

William ~. Orr _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 41 

5. Jurassic ammonites and biostratigraphy of eastern Oregon and western Idaho 

Ralph W. Imlay ----------------------------------------------------------------------------- 53 

6. Conodont ages for limestones of eastern Oregon and their implication for pre-Tertiary melange terranes 

Ellen Mullen Morris and Bruce R. Wardlaw ------------------------------------------------- 59 

7. Faunal affinities and tectonogenesis of Mesozoic rocks in the Blue Mountains province of eastern Oregon 

and western Idaho 

Emile A. Pessagno, Jr., and Charles D. Blome -------------------------------------------------- 65 

8. Geologic implications of radiolarian-bearing Paleozoic and Mesozoic rocks from the Blue Mountains 

province, eastern Oregon 

Charles D. Blome, David L. Jones, Benita L. Murchey, and Margaret Liniecki _____________________ 79 

v 

1. PALEOZOIC AND MESOZOIC FAUNAS OF THE BLUE MOUNTAINS 

PROVINCE: A REVIEW OF THEIR GEOLOGIC IMPLICATIONS AND 

COMMENTS ON PAPERS IN THE VOLUME 

By TRACY L. VALLIER and HowARD C. BROOKs 1 

ABSTRACT 

This volume contains, besides the present review, seven papers 

on the biostratigraphy of pre-Tertiary rocks in the Blue Mountains 

province. Geologic implications ofthe faunal data are discussed in the 

context of terrane analyses. Most of the authors agree that the preTertiary rocks of this province were formed in a complex island arc 

within a low-latitude faunal realm and subsequently moved northward and accreted to the North American continent. The use of different terrane names for parts of the Blue Mountains province by 

different authors may lead to some confusion. We suggest that future 

authors use the term "Blue Mountains island arc" for the pre-Tertiary 

province and, if there is a need for subdivision, that they use the 

terrane names proposed by Silberling and others (1984). 

INTRODUCTION 

Papers in this volume discuss the Paleozoic and 

Mesozoic megafossil and microfossil faunas in the Blue 

Mountains province of eastern Oregon and western 

Idaho. We compiled and edited these papers so that new 

data and interpretations become available, not only to 

earth scientists who are directly concerned with 

unraveling the geologic history of the region and determining its resources, but also to those working in other 

allochthonous terranes that rim the world's oceans (see 

Jones and others, 1977, 1982; Silberling and others, 

1984). The pre-Tertiary rocks of the Blue Mountains 

province form one large allochthonous terrane. A better 

understanding of that terrane is the major purpose of 

this volume and of the companion volumes that are in 

the process of preparation. 

The earlier work of other geologists and biostratigraphers is gratefully acknowledged. Without 

their pioneering spirit and interpretations, a collection 

of papers such as this would not now be possible. In 

particular, the works ofLindgren (1901), Merriam (1901), 

Pardee and Hewett (1914), Anderson (1930), Gilluly 

(1937), Ross (1938), Smith and Allen (1941), Merriam 

10regon Department of Geology and Mineral Industries, Baker, Oregon 97814 

(1942), Merriam and Berthiaume (1943), Wagner (1945), 

Bostwick and Koch (1962), Hamilton (1963), Thayer and 

Brown (1964), and Buddenhagen (1967) are recognized 

as important contributions to our understanding of the 

Blue Mountains region. 

In this paper we review the major interpretations of 

the authors (this volume) and summarize the geologic 

implications of their conclusions. The approximate 

areas they discuss are shown in figure 1.1. 

ACKNOWLEDGMENTS 

We appreciate the reviews of C. Blome, C. Newton, 

and W Orr, which substantially improved the manuscript. We thank Juanita Mascardo for assistance with 

the manuscripts during early stages and Ann Garrett 

for last-minute typing and the final compilation of the 

papers. Robin Frisch and Gary Mann helped with drafting. 

MAJOR CONCLUSIONS OF PAPERS IN THIS 

VOLUME 

Newton (Chapter 2: Late Triassic bivalves of the 

Martin Bridge Limestone) describes a rich, well-preserved silicified early Norian invertebrate fauna that 

was collected from the Martin Bridge Limestone. Analyses indicate that the fossils represent storm lag (tempestite) concentrations. Many of the bivalve species (76 

percent) are either new or indeterminate. The faunas in 

general show hybrid zoogeographic affinities that fit 

Tozer's (1982) paleogeographic model of central Pacific 

island arcs with mixed east and west Pacific faunas. Two 

major lithofacies are rhythmically interbedded in the 

Spring Creek outcrops, pelbiosparites making up most 

of the rocks and biopelsparrudites forming lensoid lag 

concentrations. Most bivalves, Newton reports, are suspension feeders. Some of the bivalve species reflect 

mixed zoogeographic affinities typical of North America, South America, and Japan. The large bivalve 

1 
2 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

0 

Pendleton 

WASHINGTON 

0 La Grande 

0 Enterprise 

WALLOWA 

MTS 

I 

I 

11111111111111111111111111:1 

=I :I :I 

~~ :I 

~~ IDAHO 

=I :I 

:I 

=I :I 

:I 

=~---~ 

Riggins §1 

:I 

=I :I 

=I :I 

:I 

=I :I 

6-------------------------------------------------r4·Jr-~~~~~ -------------~ 45° 

McCall 0 

0 Baker 

0 25 

I I 

0 40 

50 Miles 

I 

80 Kilometers 

I 

I 

I 

I 

I 

Weiser 

i 

I 

I 

I 

I 

I 

I 

FIGURE 1.1-Index map of eastern Oregon, western Idaho and southeastern Washington, showing the approximate boundaries of areas 

discussed in this volume. Numbers refer to individual chapters, authored as follows: 2, Newton; 3, Stanley; 4, Orr; 5, Imlay; 6, Morris and 

Wardlaw; 7, Pessagno and Blome;· 8, Blome, Jones, Murchey, and Liniecki. 

Mysidioptera cf. M. williamsi is of particular significance because it has previously been reported only from 

cratonal sedimentary rocks of northeastern British 

Columbia. These findings indicate to Newton that the 

Hells Canyon area had zoogeographic exchange with 

the North American continent during the Late Triassic 

and that the extent of North and South American faunal 

exchange with Cordilleran allochthonous terranes has 

been underestimated. 

Stanley (Chapter 3: Late Triassic coelenterate 

faunas of western Idaho and northeastern Oregon) studied coral and spongiomorph taxa from three localities 

in eastern Oregon and western Idaho and compared 

them with taxa in the Wrangellia terrane of Alaska and 

Vancouver Island. He identified 39 different corals and 9 

spongiomorphids and determined the following ages: 

for Hells Canyon, early Norian Kerri Zone; for Wallowa Mountains (Eagle Creek), probable early Norian; 

and for outcrops near Lewiston, Idaho, probable late 

Norian. The corals in these faunas lived in warm shallow water and are found together with other benthic 

invertebrates in rich biostromal deposits 1-12 m thick. 

They display strong Tethyan affinities, fully threefourths of the fauna being conspecific with distant counterparts in alpine regions of central Europe. Stanley 

found very little similarity with coeval early Norian 
1. PALEOZOIC AND MESOZOIC FAUNAS OF THE BLUE MOUNTAINS PROVINCE: A REVIEW 3 

collections in North America. This finding necessitates 

a critical evaluation of Late Triassic paleogeography and 

perhaps a re-examination of relationships between 

Wrangellia and the Wallowa-Seven Devils region. He 

concludes from the significant differences in the coral 

faunas that during the Late Triassic the Wallowa terrane may have been geographically separated from 

Wrangellia, at least by a body of water deep enough or 

one extensive enough to substantially reduce the 

exchange of coral larvae. 

Orr (Chapter 4: A Norian (Late Triassic) ichthyosaur from the Martin Bridge Limestone) relates the 

fossil animal found in the Wallowa Mountains to those 

in other localities in the United States and elsewhere. 

The ichthyosaur is assigned to the genus Shastasaurus 

which previously was known only from Upper Triassic 

rocks in northern California. Orr suggests that the correlation of this occurrence with localities in northern 

California, but not with localities on "cratonal" North 

America, strengthens the accreted-terrane hypothesis 

for a large part of the Western United States. 

Imlay (Chapter 5: Jurassic ammonites and biostratigraphy of eastern Oregon and western Idaho) 

shows that the major depositional basins formed in the 

Early Jurassic, particularly in the Hettangian through 

the Pliensbachian. In the Middle Jurassic, a large depocenter existed in the Izee-Seneca area, where the most 

complete Jurassic stratigraphic sequence in eastern 

Oregon is preserved. A much less complete sequence 

occurs in the Suplee region, indicating that it probably 

was undergoing erosion during much of the Early and 

Middle Jurassic. The youngest continuous deposition 

occurred in the earliest Callovian, but the youngest 

Jurassic sedimentary rocks thus far discovered in the 

region are middle Oxfordian strata that crop out along 

the Snake River Canyon near the Oregon-Washington 

border. Apparently, the region was largely above sea 

level during the Hettangian and Oxfordian and entirely 

so during early Pliensbachian and all of Kimmeridgian 

and Tithonian times. 

Morris and Wardlaw (Chapter 6: Conodont ages for 

limestones of eastern Oregon) report on new conodont 

ages from both the Baker and Grindstone terranes and 

discuss their age implications. Conodont ages range 

from Devonian through Late Triassic. In the Grindstone 

(melange) terrane, large blocks of limestone previously 

yielded Devonian, Mississippian, and Permian fossils, 

whereas some sandstone blocks yielded Pennsylvanian 

fossils. Chert between the various limestone blocks contains Permian radiolarians and Early Triassic conodonts. A similar range of ages is shown in the Baker 

(melange) terrane. For example, within the Miller 

Mountain melange near Canyon Mountain, Permian 

limestone blocks and Upper Triassic chert are juxtaposed. Moreover, an arc-related rock assemblage in 

the Greenhorn Mountains northwest of Baker has Permian fusilinids and conodonts, whereas oceanic 

assemblages east and southeast of Baker contain conodonts of Middle and Late Triassic age. Pennsylvanian 

and Permian conodonts in limestone blocks near Baker 

are associated with fusilinids showing Tethyan 

affinities. Pennsylvanian conodonts were recovered 

from a limestone block near Vinegar Hill in the Greenhorn Mountains, and Devonian conodonts were found in 

a limestone pod farther north. The major conclusions of 

the authors are that (1) Devonian rocks probably are 

more abundant than previously thought, (2) geographic 

subdivision of the melange terrane appears artificial, 

(3) subdivision into arc-related melange, oceanic 

melange, serpentinite-matrix melange, and ophiolitic 

complex seems more reasonable, and ( 4) exotic blocks in 

the melange terrane may be accounted for by docking 

(accreting) a pre-existing terrane into a forearc accretionary prism, or they may have been olistostromal 

blocks derived from an uplifted older arc. 

Pessagno and Blome (Chapter 7: Faunal affiniti·3S 

and tectonogenesis of Mesozoic rocks in the Blue Mountains province) strengthen the conclusions reached earlier by Thayer (1973) and more recently by Vallier and 

Engebretson (1984) that the various pre-Tertiary terranes of the Blue Mountains may all be parts of a single 

island arc (Blue Mountains island arc). They suggest 

that the island arc originated in the eastern Pacific and 

was subsequently moved northward by a large meg ashear somewhat analogous to the San Andreas fauit. 

The Blue Mountains island arc apparently was situated 

in the Central Tethyan Province, either north or south of 

the paleoequator, during the Late Triassic and Early 

Jurassic. Interpretations of ammonite and radiolarian 

data from the John Day inlier show that by early Bajocian time (about 183 Ma, according to the time scale of 

Palmer, 1983), the Blue Mountains island arc was situated within the Northern Tethyan Province (approximately 15° to 30° north latitude). Subsequent 

displacement to higher, Boreal latitudes (about 40° 

north) probably occurred during the Late Jurassic. The 

authors emphasize that megafossil assemblages in volcanic successions of the so-called Nevadian complex of 

California and Nevada show the same shift from the 

Tethyan Faunal Realm to the Boreal Faunal Realm during the course of Mesozoic time: Triassic and Early 

Jurassic assemblages have strong Tethyan affinities; 

Upper Jurassic rocks have faunas with both Tethyan 

and Boreal affinities. Pessagno and Blome use these 

data to conclude that the so-called Nevadian terrane 

and the Blue Mountains island arc could be parts of the 

same island arc complex, which originated at nearequatorial latitudes in the eastern Pacific and was then 
4 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

carried northward along a large megashear. 

Blome, Jones, Murchey, and Liniecki (Chapter 8: 

Geologic implications of radiolarian-bearing Paleozoic 

and Mesozoic rocks from the Blue Mountains province) 

use faunal and structural data to recognize five 

tectonostratigraphic terranes: Grindstone, Izee, Olds 

Ferry, Baker, and Wallowa. They discuss three of these 

(Grindstone, lzee, and Baker) in relation to their radiolarian ages. The Grindstone terrane has radiolarians 

of Early Permian to Early Triassic age. The Baker terrane contains Late Triassic radiolarians in cherts in the 

southwestern part and both Permian and Late Triassic 

radiolarians (possibly also some as young as Early 

Jurassic) in the northeastern part. The authors include 

the Miller Mountain and Frenchy Butte melange areas 

in the Baker terrane on the basis oflithologies, identical 

characteristics of the radiolarian faunas, and the fact 

that the Grindstone terrane contains no known chert 

younger than Early Triassic. Though Carboniferous 

chert is absent from the Grindstone terrane, it occurs as 

clasts in the conglomeratic rocks within the basal part of 

the Izee terrane. This indicates that the Grindstone 

terrane was not the source for Izee terrane detritus; 

rather, the Baker terrane was the probable source. 

Moreover, coeval Upper Triassic radiolarian cherts in 

the Brisbois Member of the Vester Formation, in the 

herein-revised Rail Cabin Mudstone Member of the Vester Formation, and in the Fields Creek Formation indicate that the Vester Formation was not the source of 

detritus for the Fields Creek Formation. An important 

point the authors make is that the abundance of Permian sedimentary rocks in the Baker terrane (ages 

based on radiolarians, conodonts, and fusilinids) attest 

that these rocks are not "exotic" blocks. Ages seem to 

young from west to east in the Baker terrane. The age 

range of the Elkhorn Ridge Argillite is extended to 

include the Middle Pennsylvanian to the Late Triassic 

and possibly the earliest Jurassic. 

GEOLOGIC IMPLICATIONS 

The terrane concept has greatly helped the interpretation of geologic relationships in the Blue 

Mountains province, but it has also led to some confusion. Different terrane names have been proposed by 

several authors (Vallier and others, 1977; Brooks and 

Vallier, 1978; Dickinson and Thayer, 1978; Brooks, 1979; 

Dickinson, 1979), and even more recently (see papers in 

this volume and in Silberling and others, 1984) new 

names have been proposed for various parts and parcels 

of the Blue Mountains province. It seems premature to 

propose formal terrane names in the Blue Mountains 

region, because sound definitions of island-arc terranes 

should be tied to the processes that formed them and 

these processes related to those occurring in modern 

island arcs. Unfortunately, although our understanding 

of modern island arcs is rapidly increasing, many questions remain to be answered concerning island arc processes. 

Island arcs are major features of the earth's land 

surface; they are mountain ranges that are mostly submerged. For example, the intra-oceanic part of the Aleutian structural arc is approximately 2,200 km (1,375 

miles) long and 200 km (125 miles) wide and has a total 

area of about 440,000 km2 (170,000 mi2 ). It rises from a 

depth of 7.3 km below sea level (floor of the Aleutian 

Trench) to about 3 km above sea leveL If the thick 

sediment accumulation in the trench were removed, the 

trench would have some depths greater than 11 km 

(Scholl and others, 1982) and the total relief would be 

more than 14 km (about 8.75 miles or 46,000 feet). In 

addition to appreciating the sizes of island arcs, we are 

gaining insights into sedimentation patterns and formation of major basins within the arcs (see, for example, 

Scholl and others, 1983, 1985; Katz, 1984). The diverse 

assemblages of pre-Cenozoic rocks in the Blue Mountains island arc can be compared, both areally and geologically, to assemblages within the present-day intraoceanic island arcs. At present, however, we do not know 

how much of the Blue Mountains island arc may have 

been destroyed by subduction or displaced to other 

regions by transcurrent faults. 

For other workers attempting to unravel the geologic history of the Blue Mountains province, we endorse 

the suggestion ofPessagno and Blome (this volume) that 

the pre-Tertiary rocks collectively be referred to as the 

Blue Mountains island arc. If there are reasons to subdivide, workers are encouraged to use the nomenclature 

referred to in Blome and others (this volume; terrane 

names proposed by Silberling and others, 1984). 

The original location of the Blue Mountains island 

arc is not dealt with in detail by the topical papers in 

this volume. Newton, Stanley, and Pessagno and Blome 

(all this volume) both imply and suggest an eastern 

Pacific, near-equatorial initial location for the Blue 

Mountains island arc. They may agree in part with 

Dixon (1984), who inferred that terranes in the Pacific 

moved northwestward by lateral transport during the 

opening of the Atlantic Ocean. Interpretations by 

Engebretson (1983) and Vallier and Engebretson (1984) 

make a western Pacific source region possible, if the 

Blue Mountains island arc were brought across the 

Pacific on the Farallon Plate. This would imply a Devonian to Early Jurassic connection with terranes in Australia (for example, New England fold belt), New 

Zealand, New Caledonia, and New Guinea. Faunal data, 

however, have thus far not supported such a western 

Pacific connection. 
1. PALEOZOIC AND MESOZOIC FAUNAS OF THE BLUE MOUNTAINS PROVINCE: A REVIEW 5 

The suggestion by Imlay (this volume) that there 

were multiple source areas for Jurassic sediments in the 

Blue Mountains island arc agrees with our knowledge of 

processes in modern island arcs, where each basin may 

have a separate sediment source (for example, see Scholl 

and others, 1983). The regional uplift of the Blue Mountains island arc that apparently took place in the Late 

Jurassic may correlate with the beginning of Late 

Jurassic plutonism. The oldest plutons of the Jurassic 

and Cretaceous plutonism, which includes the Bald 

Mountain and Wallowa batholiths, are dated at about 

160 Ma (Armstrong and others, 1977) and this age correlates with a Late Jurassic hiatus in sedimentation 

(beginning of Oxfordian is about 163 Ma, according to 

the time scale of Palmer, 1983). Collision of the Blue 

Mountains island arc with the North American continent probably took place after the Late Jurassic (Callovian) because no continental detritus has yet been 

reported in the Jurassic sedimentary rocks. The formation of the depocenters and source-region highlands can 

be explained by normal island arc processes. 

REFERENCES 

Anderson, A.L., 1930, The geology and mineral resources of the region 

about Orofino, Idaho: Idaho Bureau of Mines and Geology Pamphlet 34, 63 p. 

Armstrong, R.L., Taube neck, W.H., and Hales, P.O., 1977, Rb-Sr and KAr geochronometry of Mesozoic granitic rocks and Sr isotopic 

composition, Oregon, Washington, and Idaho: Geological Society 

of America Bulletin, v. 88, p. 397-411. 

Bostwick, D.A. and Koch, G.S., 1962, Permian and Triassic rocks of 

northeastern Oregon: Geological Society of America Bulletin, v. 

73, p. 419-421. 

Brooks, H. C., 1979, Plate tectonics and the geologic history of the Blue 

Mountains: Oregon Geology, v. 41, p. 71-80. 

Brooks, H. C. and Vallier, T.L., 1978, Mesozoic rocks and tectonic evolution of eastern Oregon and western Idaho, in Howell, D.G., and 

McDougall, K.A., eds., Mesozoic paleogeography of the Western 

United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 2, p. 133-146. 

Buddenhagen, H.J., 1967, Structure and orogenic history of the southwestern part of the John Day uplift, Oregon: Ore Bin, v. 29, p. 

129-138. 

Dickinson, W.R., 1979, Mesozoic forearc basin in central Oregon: 

Geology, v. 7, p. 166-170. 

Dickinson, W.R., and Thayer, T.P., 1978, Paleogeographic and paleotectonic implications of Mesozoic stratigraphy and structure in the 

John Day inlier of central Oregon, in Howell, D.G., and 

McDougall, K.A., eds., Mesozoic paleogeography of the Western 

United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium2, p.147-161. 

Dixon, J.S., 1984, Mesozoic-Cenozoic tectonic evolution of western 

North America-an alternative to the orocline, in Watson, S. T., 

ed., Transactions of the Third Circum-Pacific Energy and Mineral Resource Conference: Circum-Pacific Council for Energy 

and Mineral Resources, p. 589-592. 

Engebretson, D.C., 1983, Relative motions between oceanic and continental plates in the Pacific basin: Stanford, Calif., Stanford 

University, Ph.D. dissertation, 211 p. 

Gilluly, James, 1937, Geology and mineral resources of the Baker 

quadrangle, Oregon: U.S. Geological Survey Bulletin 879, 119 p. 

Hamilton, W.B, 1963, Metamorphism in the Riggins region, western 

Idaho: U.S. Geological Survey Professional Paper 436, 95 p. 

Jones, D.L., Silberling, N.J., and Hillhouse, J.W., 1977, Wrangellia-a 

displaced terrane in northwestern North America: Canadian 

Journal of Earth Sciences, v. 14, p. 2565- 2577. 

Jones, D.L., Cox, Allan, Coney, Peter, and Beck, Myrl, 1982, The 

growth of western North America: Scientific American, v. 24 7, p. 

70-84. 

Katz, H.R., 1984, Southwest Pacific island arcs: sedimentary basins 

and petroleum prospects in the New Hebrides and Solomon 

Islands, in Watson, S.T., ed., Transactions of the Third CircumPacific Energy and Mineral Resource Conference: CircumPacific Council for Energy and Mineral Resources, p. 181-189. 

Lindgren, Waldemar, 1901, The gold belt of the Blue Mountains of 

Oregon: U.S. Geological Survey Annual Report 22, p. 551-776. 

Merriam, J.C., 1901, A contribution to the geology of the John Day 

Basin, Oregon: University of California, Bulletin of the Department of Geology, v. 2, p. 269-314. 

Merriam, C.W., 1942, Carboniferous and Permian corals from central 

Oregon: Journal of Paleontology, v. 16, p. 372-381. 

Merriam, C. W., and Berthiaume, S .A., 1943, Late Paleozoic formations 

of central Oregon: Geological Society of America Bulletin, v. 54, 

p.145-171. 

Palmer, A.R., 1983, The Decade of North American Geology 1983 

geologic time scale: Geology, v. 11, p. 503-504. 

Pardee, J.T., and Hewett, D.F., 1914, The geology and mineral 

resources of the Sumpter quadrangle, Oregon: Mineral 

Resources ofOregon, v. 1, no. 6, p. 4-128. 

Ross, C.P., 1938, The geology of part of the Wallowa Mountains, 

Oregon: Oregon Department of Geology and Mining Industries 

Bulletin 3, 74 p. 

Scholl, D.W., Vallier, T.L., and Stevenson, A.J., 1982, Sedimentation 

and deformation in the Amlia fracture zone sector of the Aleutian trench: Marine Geology, v. 48, p. 105-134. 

---1983, Arc, forearc, and trench sedimentation and tectonics: 

Amlia corridor of the Aleutian Ridge, in Watkins, J.S., and 

Drake, C.L., eds., Studies in Continental Margin Geology: American Association of Petroleum Geologists Memoir 34, p. 413- 439. 

Scholl, D.W., Vallier, T.L., and Packham, Gordon, 1985, Framework 

geology and resource potential of the southern Tonga platform 

and adjacent terranes: a synthesis, in Scholl, D.W., and Vallier, 

T.L. eds., Geology and resource potential of island arc regions: 

Southern Tonga Region: Circum-Pacific Council Earth Science 

Series, v. 2, p. 457-475. 

Silberling, N.J., Jones, D.L., Blake, M.C., and Howell, D.G., 1984, 

Lithotectonic terrane map of the western conterminous United 

States, in Silberling, N.J. and Jones, D.L., eds., Lithotectonic 

terrane maps of the North American Cordillera: U.S. Geological 

Survey Open-File Report 84-523. 

Smith, W.D., and Allen, J.E., 1941, Geology and physiography of the 

northern Wallowa Mountains, Oregon: Oregon Department of 

Geology and Mining Industries Bulletin 12, 65 p. 

Thayer, T.P., 1973, Blue Mountains region of northeastern Oregon and 

western Idaho interpreted as a pre-Cretaceous island arc system [abs.]: Geological Society of America Abstracts with Programs, v. 5, p.115-116. 

Thayer, T.P., and Brown, C.E., 1964, Pre-Tertiary orogenic and plutonic intrusive activity in central and northeastern Oregon: Geological Society of America Bulletin, v. 75, p. 1255-1262. 

Tozer, E.T., 1982, Marine Triassic faunas of North America: their 

significance for assessing plate and terrane movements: 
6 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

Geologische Rundschau, v. 71 , p. 1077-1104. 

Vallier, T.L., Brooks, H.C., and Thayer, T.P., 1977, Paleozoic rocks in 

eastern Oregon and western Idaho, in Stewart, J.H., Stevens, 

C.H., and Fritsche, A.E., eds., Paleozoic paleogeography of the 

Western United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography 

Symposium 1, p. 455-466. 

Vallier, T.L. , and Engebretson, D.C., 1984, The Blue Mountains island 

arc of Oregon, Idaho, and Washington : an allochthonous 

coherent terrane from the ancestral western Pacific Ocean? in 

Howell, D.G. , Jones, D.L., Cox, Allan, and Nur, Amos, eds., 

Proceedings of the Circum-Pacific Terrane Conference: Stanford 

University Publications in the Geological Sciences, v. 18, p. 

197-199. 

Wagner, W.R., 1945, Geological reconnaissance between the Snake and 

Salmon Rivers north of Riggins: Idaho Bureau of Mines and 

Geology Pamphlet 74, 16 p. 
2. LATE TRIASSIC BIVALVES OF THE MARTIN BRIDGE LIMESTONE, 

HELLS CANYON, OREGON: TAPHONOMY, PALEOECOLOGY, 

PALEOZOOGEOGRAPHY 

By CATHRYN R. NEWTON 1 

ABSTRACT 

Richly fossiliferous lenses of silicified shells in the Norian Martin Bridge Limestone of Hells Canyon represent "windows" of 

unusually excellent preservation through which can be read the taphonomy, paleoecology and paleozoogeography of Late Triassic bivalves 

of the Wallowa Mountains-Seven Devils Mountains volcanic arc terrane of northeastern Oregon. Taphonomic, petrographic, and stratigraphic analysis of the shell beds discloses that they represent storm 

lag concentrations formed by processes of winnowing and local transport of shells. Despite the inferred transport, however, the autecology 

of 38 bivalve species is remarkably uniform, suggesting an epifaunal, 

suspension-feeding association that inhabited peloidal carbonate sediment. Many of these epifaunal bivalve species (74 percent) are either 

new or indeterminate on the basis of present collections. 

Because of the high frequency of new or indeterminate species, 

zoogeographic conclusions based on species are necessarily preliminary. Those species that have been previously described from other 

areas are of varied zoogeographic affinities; "Septocardia" sp. and 

Mysidoptera williamsi are North American forms; Mysidiella cf. M. 

americana and Thtcheria densestriata are closely allied to species 

from South America; and Parallelodon cf. P. monobensis and 

"Chlamys" cf. "C." mojsisovicsi resemble Japanese bivalves. This perplexing assortment of zoogeographic affinities can best be understood 

in terms of Tozer's (1982) paleogeographic model of central Pacific 

island arcs with mixed East and West Pacific faunas. It should be 

emphasized, however, that Norian bivalve species of both the North 

American craton and the suspect terranes along its margins are at 

present imperfectly documented. 

INTRODUCTION 

Diverse silicified benthic macroinvertebrates of 

Late Triassic age from the Hells Canyon region of northeastern Oregon have significance both for paleoecological reconstructions of early Mesozoic tropical 

island arc biotas and for tectonic reconstructions of 

early Mesozoic suspect terranes. This report describes 

the bivalve taphonomy, paleoecology, and paleozoogeography of silicified shell beds from the lower 

Norian part of the Martin Bridge Limestone north of 

Spring Creek on the western flank of Hells Canyon (fig. 

2.1). At this site the Martin Bridge consists of shallowwater carbonate rocks in depositional contact with 

1 Department of Geology, Syracuse University, Syracuse, New York 13244-1070 

underlying arc volcanic rocks of the Seven Devils Group 

(Vallier, 1967, 1974, 1977; Sarewitz, 1983). 

Previous paleoecologic studies of early Mesozoic 

molluscan communities have focused on rifted-margin 

sedimentary basins, such as that of the Cassian Formation of the southern Alps (Fursich and Wendt, 1977; 

Wendt and Fursich, 1980), or on latest Norian- earliest 

Hettangian arc-related mixed carbonate and clastic 

sedimentary rocks (Laws, 1982). In contrast, this study 

is an examination of the taphonomy and autecology of 

the biota in early Norian pure carbonate sediments that 

are of tropical island-arc origin (Hillhouse and others, 

1982). Such habitats are the loci for the most diverse and 

45° 116°50 w 10N 

OREGON Area of 

IDAHO 

5 KILOMETERS 

OI--......._ ......... ___.~....._T MILES 

FIGURE 2.1.-Index map of part of Snake River canyon, showing 

location of measured fossiliferous carbonate section (MBL) north of 

Spring Creek, Oregon. Stippling indicates outcrop area of the Martin Bridge Limestone, after Vallier (1974). Quaternary sediment 

locally covering the Martin Bridge is not indicated. 

7 
8 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

most rapidly evolving marine invertebrate faunas in the 

modern world ocean (Vermeij, 1978). 

Assessment of the paleobiogeographic affinities of 

the Spring Creek fauna also allows refinement of existing paleogeographic models for the Hells Canyon region 

during the early Mesozoic. Application of the tectonostratigraphic terrane concepts (for example, Jones and 

others, 1972, 1977, 1978, 1982, 1983; Jones and Silberling, 1979; Coney and others, 1980) to tectonic interpretation of the Hells Canyon area has spawned 

controversy regarding the kinship of the Wallowa Mountains-Seven Devils Mountains volcanic arc terrane of 

Brooks and Vallier (1978) to larger "suspect" terranes. 

Whether the arc formed in close proximity to North 

America during the Middle and Late Triassic, or instead 

occupied part of the demonstrably allochthonous 

Wrangellia terrane, has been a matter of dispute in the 

recent literature (Jones and others, 1977; Hillhouse and 

others, 1982; Sarewitz, 1983; Silberling, 1983). Jones and 

others (1977) first recognized the intriguing resemblance between the early Norian shelly faunas of 

Wrangellia and those of the Hells Canyon region. Newton (1983) found that similarities, for bivalve genera, of 

the Norian faunas of Hells Canyon and the Wrangell 

Mountains exceeded those of any other pair of cratonal 

or "suspect" terrane localities of North America (Simpson similarity coefficient= 77; S0renson similarity 

coefficient= 0.65). This paper considers the Hells Canyon bivalves at the specific level and attempts to use 

their ecology and zoogeography as tools for reconstructing Late Triassic depositional environments and paleogeography of the Wallowa Mountains-Seven Devils 

Mountains volcanic arc terrane. 

A prerequisite for any discussion of Mesozoic paleozoogeography of western North America is a clear 

definition of which regions are to be considered cratonal, 

sensu stricto, and which regions are to be termed 

tectonically "suspect". The only bivalve-rich Upper Triassic rocks deemed to have clear tectonic affinities to 

cratonal North America are the Pardonet Formation of 

northeastern British Columbia (McLearn, 1940, 

1941a,b; Tozer, 1965, 1982) and the upper part of the Star 

Peak Group and the lower part of the Auld Lang Syne 

Group in Nevada (Silberling, 1961; Silberling and Wallace, 1969; Burke and Silberling, 1973; Nichols and Silber ling, 1977). In other plate-bound areas of North 

America, such as the Sverdrup Basin of Arctic Canada, 

marine Norian strata are present but are not rich in 

shelly benthic faunas (Tozer, 1982). The numerous other 

Upper Triassic Cordilleran lithostratigraphic units 

with rich bivalve faunas occur west of the belt of platebound rocks and will herein be considered "suspect" 

(Coney and others, 1980); many of these units are clearly 

of allochthonous origin. 

ACKNOWLEDGMENTS 

The assistance of Tracy Vallier in the planning of 

fieldwork in Hells Canyon is much appreciated. I also 

thank Leo Laporte for help in the design and execution 

of this study and David Jones and Norman Silber ling for 

valuable discussions and for the loan of bivalve specimens. Andrzej Gazdzicki kindly examined the benthic 

foraminifers in my Spring Creek samples. Denise 

Mungioli and Joel Thompson were tireless field 

assistants, and Pat and Dixie Wilmarth were of great 

help with field logistics. I thank David Delalla for 

assistance with the acid-bath preparation of samples. K. 

Sakamoto and P. Jones assisted greatly in the photography of fossil specimens. 

This research was supported by the Atlantic 

Richfield Foundation Junior Faculty Development Fund 

to Syracuse University, by an ARCO doctoral research 

grant to the University of California, Santa Cruz, and 

by the Aaron and Elizabeth Waters Award of the University of California. 

I thank H.C. Brooks, D.L. Jones, H.T. Mullins, N.J. 

Silberling, G.D. Stanley, and T.L. Vallier for their critical reviews of the manuscript. 

PREVIOUS WORK 

Ross (1938) formally proposed the name Martin 

Bridge Formation (subsequently revised to the Martin 

Bridge Limestone by Vallier, 1977) for a massively bedded carbonate unit that crops out in the Wallowa Mountains of northeastern Oregon, though the term had 

appeared in print already years earlier (Chaney, 1932; 

Gilluly and others, 1933). Vallier (1967, 1974) extended 

this name, on the basis of stratigraphic and faunal 

resemblance, to patches of Norian limestone that occur 

on the ridges flanking Hells Canyon. Other stratigraphic studies of the Martin Bridge Limestone in 

northeastern Oregon and western Idaho include those 

of Laudon (1956), Cannon (cited in Hamilton, 1963), Nolf 

(1966), and Stanley (1979a). 

The most complete section of the Martin Bridge in 

Hells Canyon is at Kinney Creek, where Vallier (1967) 

measured 530 m of sparites, biomicrites and micrites 

intercalated with carbonate breccia. The top of the formation is not exposed at Kinney Creek, so that its total 

thickness at that site remains uncertain. As described 

by Vallier, the Kinney Creek rocks are relatively 

unfossiliferous; he reported only a single bed of bivalves 

and scattered bivalve fragments in the lower part of the 

section. 

Numerous other workers have reported bivalves 

from the Martin Bridge Limestone (Lindgren, 1901; 
2. LATE TRIASSIC BIVALVES OF THE MARTIN BRIDGE LIMESTONE, HELLS CANYON, OREGON 9 

Smith, 1927; Ross, 1938; Smith and Allen, 1941; Laudon, 

1956; Hamilton, 1963;Nolf, 1966; Stanley, 1979a), but the 

bivalve faunas have never before been examined in 

detail. Whereas most of the forms mentioned in the 

literature are halobiid bivalves that characterize pelagic 

carbonate facies (Hallam, 1981), the rich shelly faunas 

discussed here represent shallow-water benthic associations. 

The Spring Creek locality was first discovered by 

Vallier (1967). An early Norian age for the Martin Bridge 

Limestone there was inferred on the basis of N.J. Silberling's identification of Tropiceltites columbianus in the 

shell beds (Vallier, 1967, p. 246-24 7). T. columbianus is 

typical of the lowermost Norian Mojsisovicsites kerri 

zone (Silberling and Tozer, 1968). 

In addition to bivalves and ammonoid cephalopods, 

a host of other invertebrates are found in the Spring 

Creek silicified shell beds: benthic foraminifers, 

sponges, spongiomorphs, scleractinians, serpulids, 

articulate brachiopods, ?scaphopods, gastropods, and 

echinoderms. A. Gazdzicki is currently examining the 

free-living and encrusting foraminifera. Montanaro 

Gallitelli and others (1979) and Stanley (this volume) 

have presented systematic treatments of the scleractinian corals and the spongiomorphs. The Spondylospiralike articulate brachiopods are the focus of a monograph 

in preparation by P. Hoover, and I have forwarded echinoderm specimens from my collections to P. Kier for 

further study. These investigations of the rich Spring 

Creek fauna will considerably improve our knowledge of 

early Norian arc biotas. 

MATERIALS AND METHODS 

The material that forms the basis for this study is 

from U.S. Geological Survey Mesozoic collection M2672, 

made by Tracy Vallier in 1964, and from my own field 

collections made in 1982 and 1983. The U.S. Geological 

Survey collections comprise 677 fossil invertebrate specimens (excluding articulate brachiopods and scleractinian corals), of which 538 are bivalves and gastropods. 

My collections from the Spring Creek locality include 

more than 5000 macroinvertebrate specimens. 

The silicified macroinvertebrates were freed from 

the calcareous matrix using dilute hydrochloric acid. 

The M2672 samples were prepared in this manner at 

the U.S. Geological Survey in Denver by Norman Silberling. My collections were prepared in 7-percent HCI. 

Because of folding and pervasive recrystallization of 

the carbonate rocks it is difficult to construct an accurate composite section of the entire Martin Bridge Limestone at Spring Creek. A short section of part of the 

Martin Bridge containing the silicified shell beds was 

measured (fig. 2.2). 

• Cephalopods 

in float 

• 

CENTIMETERS 

[

100 

50 

0 

EXPLANATION 

Grain-supported pelmicrite, 

pelsparite, pelbiosparite 

Massive, recrystallized limestone: 

bedding indistinct 

Grain-supported biopelsparrudite, 

biopelsparite 

~ Chert, in irregular bands 

FIGURE 2.2.-Measured section of part of the Martin Bridge Limestone at the Spring Creek locality. Dots to the left of column indicate 

lithologic samples collected for this study in 1982. 

I also examined 90 thin sections and 20 acetate 

peels from the fossiliferous carbonate rocks at Spring 

Creek in order to reconstruct the depositional and 

diagenetic history of the silicified shell beds. Positions of 

these samples in the measured section are shown in 

figure 2.2. 

RESULTS 

STRATIGRAPHY AND PETROGRAPHY 

The measured section at Spring Creek consists of 

two alternating lithofacies defined by the relative abundance of skeletal allochems. The first lithofacies, which 

constitutes most of the section at the Spring Creek 

locality, consists of grain-supported fossiliferous pelbiosparites with local pelbiomicrites (fig. 2.3B). Nonskeletal allochems include peloids and a variety of 

coated grains, some of which approach ooids in regularity of outline and evenness of coating (fig. 2.3B). 

Fossils are sparse; those seen in thin section include 

free-living and encrusting foraminifers (?Tolypammina; fig. 2.3B), brachiopods and bivalves. In hand specimen and outcrop, echinoderms, bivalves, and gastropods were also observed. The cement in this 

lithofacies is predominantly sparry, with only minor 

patches of interstitial micrite. These micrite patches 
10 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

FIGURE 2.3.-Photomicrographs showing lithofacies of the Martin 

Bridge Limestone at Spring Creek. A, Silicified biopelsparrudite of 

the shell lenses. Arrow marks an encrusting foraminifer 

(?1blypammina) coating a silicified bivalve. Elongate white patches 

are skeletal allochems that have been replaced by quartz. B, 

Biopelsparite of the interbedded, sparsely fossiliferous carbonate 

rocks. Scale bars are 1 mm. 

may not represent original cement; many of them are 

probably the product of degradation of skeletal 

allochems. 

The other lithofacies, represented by the richly fossiliferous shell beds, consists of grain-supported 

biopelsparrudites with subordinate biopelmicrudites 

(fig. 2.3A). Mollusks (bivalves and gastropods) are the 

predominant skeletal allochems. Other skeletal 

allochems evident in thin section include brachiopods, 

echinoderms, free-living benthic foraminifers, and 

encrusting foraminifers. In hand specimen and outcrop, 

inozoan sponges, spongiomorphs, scleractinian corals, 

serpulids and ?scaphopods were also found. The coarse 

sand- to gravel-sized skeletal clasts occur together with 

fine sand- to silt-sized peloids and coated grains of varied outlines. Within the shell lenses, umbrella structures and other grain-sheltered patches are common; 

sediment in these patches consists of peloids and coated 

grains. 

The two major lithofacies are rhythmically interbedded; the pelbiosparites constitute most of the measured section, whereas the biopelsparrudites form 

lensoid lag concentrations (averaging 25-30 em in 

thickness and 10-15 m across) within the peloidal sand 

deposits. The bases of the biopelsparrudite lenses are 

marked by scoured surfaces (fig. 2.4), and the lower part 

of the skeletal sand concentrations commonly exhibits 

small-scale cross bedding. Many biopelsparrudite 

lenses also show normal grading, and their upper contacts are generally more gradational than their bases. 

The sedimentary rhythmite produced by the intercalation of the two lithofacies is thus marked by a basal 

scour, which forms the lower boundary of the shell bed, 

overlain by normally graded bioclastic carbonate sediment with predominantly disarticulated fossils (fig. 

2.5), succeeded by peloidal carbonate sediment that 

exhibits small-scale crosslamination. 

BIVALVE PALEOECOLOGY AND PALEOZOOGEOGRAPHY 

Epifaunal suspension feeders are dominant among 

the 38 species of bivalves in the Spring Creek fauna; 79 

percent of the species and 76 percent of the individuals 

are epifaunal, and 97 percent of the species and 99.5 

percent of individuals are suspension feeders. Twentyeight of the species (7 4 percent) are either new or indeterminate (table 2.1). 

True oysters and oysterlike bivalves are the most 

common bivalves in the Spring Creek shell beds. Taxonomic assignment of many of these forms is rendered 

extremely difficult by the paucity of well-preserved muscle scars. True oysters ofthe generaLopha andLiostrea 

(and possibly also Gryphaea), and oysterlike bivalves 

such as Plicatula (pl. 2.1, figs. 16-19), have been recognized. 

The inequivalve pterioid Cassianella c£ C. angusta 

(pl. 2.1, figs. 1-5) constitutes one of the most abundant 

bivalve taxa at Spring Creek. Cassianella was a suspension feeder that probably lived with its lower, highly 

convex valve partially sunk into the sediment, and the 

small upper valve just above the sediment-water interface. A frequent constituent of shallow-water, soft-sediment benthic marine associations of the Late Triassic, 

Cassianella is the dominant bivalve genus in the 

Ampullina association of the Alpine Formation, and is 

also common in the Thtcheria association of the Gabbs 

Formation of Nevada (Fursich and Wendt, 1977; Laws, 

1982). Cassianella has a very broad paleozoogeographic 
2. LATE TRIASSIC BIVALVES OF THE MARTIN BRIDGE LIMESTONE, HELLS CANYON, OREGON 11 

FIGURE 2.4. -Slab of the Martin Bridge Limestone, showing face 

-

perpendicular to bedding. Photograph shows the lower part of silicified shell 

bed and the upper part of the shell-rich layer; the contact is indicated by arrows. Slab has been naturally etched by fresh water; hence, 

silicified skeletal allochems have weathered out of the calcareous peloidal matrix. Scale bar represents 1 em. 

distribution. It is found both in high paleolatitude sediments of Bear Island (Bohm, 1904) and at numerous 

localities in low-latitude habitats of the Palaeotethys 

(sensu Sengor, 1979). Its longitudinal range is also very 

broad, extending from western Europe to cratonal 

North America. Hence, the genus Cassianella is not ' 

useful as a biogeographic indicator of provenance for the 

North American suspect terranes. 

Bivalves of the genus "Septocardia" are common at 

Spring Creek (pl. 2.1, figs. 12-13). The specimens are 

unusual representatives of the genus in having an elongate, subquadrate outline with a distinct postero-dorsal 

carination, so that in external view they bear a close 

resemblance to the carditid Palaeocardita. The presence of a conspicuous anterior myophorous buttress on 

valve interiors suggests, however, that these specimens 

should be assigned to Septocardia, based on the broad 

redefinition of this genus proposed by Keen (1980). The 

buttress is a diagnostic feature of Septocardia (Hall and 

Whitfield, 1877; Silberling, 1959, 1961; Cox and others, 

1969; Keen, 1980), whereas no buttress is mentioned in 

A. Chavan's description of Palaeocardita in the Treatise 

on Invertebrate Paleontology (Cox and others, 1969, p. 

554). A further resemblance to the genus Septocardia is 

indicated by the tuberculate nature of the posterior 

lateral teeth in the Spring Creek specimens; as noted by 

Silber ling (1961), tuberculiform laterals are more typical 

of Septocardia, whereas Palaeocardita has elongate, 
12 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

FIGURE 2.5.--Acid-etched slab of the Martin Bridge Limestone, Spring Creek, Hells Canyon, Oregon. Surface shown is parallel to bedding. Note 

incipient fragmentation offossils along fractures; thus, some of the comminuted skeletal debris seen in insoluble residues may be an artifact 

of sample preparation. Scale bar represents 1 em. Photograph by R.E. Burkholder. 

laminate lateral teeth (Cox, 1949). Certainly the Spring 

Creek specimens, along with other Late Triassic examples of"Septocardia"from North America, merit further 

study as possible transitional forms between the bivalve 

superfamilies Cardiacea and Carditacea. 

Septocardia is best categorized as an infaunal suspension-feeding bivalve, by comparison with the living 

habits of modern cardiids (Stanley, 1970). Corroboration 

for this interpretation comes from the Gabbs Formation 

of Nevada, where Laws (1982) has reported Septocardia 

in apparent life orientation, with the plane of commissure perpendicular to bedding, and the posterior 

margins of the valves oriented upward. Like many modern cardiids (Stanley, 1970), Septocardia was probably a 

shallow burrower. 

Septocardia of typical morphology and the unusual 

forms assigned to "Septocardia" are both restricted in 

paleozoogeographic distribution to cratonal North and 

South America, and to the belt of Cordilleran suspect 

terranes (Hall and Whitfield, 1877; Cox, 1949; Silberling, 1959, 1961, and cited in Muffler, 1967; Nolf, 1966; 

Hayami and others, 1977; Stanley, 1979a; Laws, 1982; 

Newton, 1983). Thus, the presence of "Septocardia" at 

Hells Canyon has important paleozoogeographic 

implications for the Spring Creek fauna. 

The large, flat pterioid Mysidioptera williamsi (pl. 

2.1, figs. 14-15), another distinctive element of the 

Spring Creek bivalve fauna, is interpreted as an epibyssate suspension feeder. The specimens from Spring 

Creek closely resemble the holotype of M. williamsi in 

overall shape, occurrence of postero-dorsal emargination and mucronation, and presence of wavy concentric 

ridges. 

This species is of paleozoogeographic significance, 

having been reported previously only from the cratonbound sediments of northeastern British Columbia 

(McLearn, 1941a). The discovery of Mysidoptera 

williamsi at Spring Creek indicates that the Hells Canyon area had zoogeographic exchange with the North 

American continent during the Late Triassic. The 

Spring Creek occurrence also suggests an extended biostratigraphic range for this species, from the upper 
2. LATE TRIASSIC BIVALVES OF THE MARTIN BRIDGE LIMESTONE, HELLS CANYON, OREGON 13 

TABLE 2.1.-Biualues from the U.S. Geological Survey collection M2672, Hells Canyon, Oregon 

[Data from 203 individuals represented by 27 4 specimens. n = number of individuals identifiable at least to ordinal level. P = proportion of identifiable individuals in the sample; 

ES = epifaunal sessile; EB =epifaunal byssate ; EC = epifaunal cementer; IM = infauna l mobile; S = suspension feeder; D = deposit feeder; H =Shannon-Wiener diversity index; 

E = observed equitability J 

Genus and species 

Abundance 

rank n p 

Life 

habit 

Feeding 

type 

Cassianella cf. C. angusta .....•.... 1 

"Septocardia" sp. • • • • . . • • • . . . • • • • . . • 2 

MYsidioptera williamsi ...••..••..... 3 

Lopha sp. 2 • • • • . • • • • • • • • • • • . • • • • • . • • 4, 5 

?Pachycardiidae, gen. uncertain ••... do 

Plicatula hekiensis ......•......•.•. 6 

Mysidiella cf. M. americana ......... 7 

Antiquilima n. sp. 2 •.•.•.•.••....•. 8,9 

?Lopha sp. 1 ••••••••••••••••••.••••• do 

Trigoniidae, new gen. 1 .•.••••....•• 10 

Pseudolimea naumanni .•.•.•....••..•. 11 

Parallelodon cf. P. monobensis •..... 12-20 

Gervillia (Cultriopsis) angusta ....• do 

Pteriidae, sp. 2 .................... do 

"Chlamys" cf. C. mojsisovicsi ..•...• do 

Pectinid B . • . • . . • . . . . . . . . • • . . • . • • • • . do 

Pectinid C .......................... do 

P,ec t inid D • • • • • • • • • • • • • • • • • • • • • • • • • • do 

Anti qui lima n. sp. 1 • . . . . • . . • . • . . • . . . do 

?Tutcheria sp. . . . . • . . . . . . . . . . . • . • . • . do 

Arcoid indet ....•....•..•..•........ 21-28 

Pteriidae, sp. 1 .................... do 

Pectinid A . • . . . . . . . . . • . . . • . . . . . . . . • . do 

MYsidioptera spinigera .............. do 

Plicatula sp. 1 • • . • • • . • • . • • • . • • • . • • . do 

"oyster" sp. 1, indet. . . • . . . . . . . . . . . do 

Tutcheria densestriata .............. do 

?Fimbriidae indet. . . . . . . • . . . . . . . . . • . do 

Nuculoid indet •....•....•.....••.... 29-38 

Pteriacean indet. • . • . . . . . • . . . . . • . . . . do 

?Antiqui lima sp. • . • . . . . . . . . . . . . . • . . . do 

Antiqui lima ? sp. 3 • • • • • • • • • • • • • • • • • do 

Liostrea sp. . . • . . . . . . . . . . . . . . . . . • . . . do 

?Gryphaea sp. • . . . . . . . . . . . . . . . . . . • . . . do 

Limacean indet. • . . . . . . . . . . . • . . . . . . . . do 

"oyster" sp. 2, in de t. . . . • . . • . . • . . . . do 

Bakevilliidae, indet ................ do 

Trigoniidae, gen. 2 . • . . . . . • . . . . . . . . do 

Bivalve indet. 

H= 1.2915* 

Hmax= 1.5798 

E= 0.8175 

Karnian in northeastern British Columbia (Tozer, 1965) 

to the lowermost Norian in Hells Canyon. 

Plicatula hekiensis is a spinose, oysterlike bivalve 

(pl. 2.1, figs. 16-19) that is inferred to have been an 

47 

23 

13 

10 

10 

9 

7 

6 

6 

5 

4 

3 

3 

3 

3 

3 

3 

3 

3 

3 

2 

2 

2 

2 

2 

2 

2 

2 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

9 

0.2435 

.1192 

.0674 

.0518 

.0518 

.0466 

.0363 

.0311 

.0311 

.0259 

.0207 

.0155 

.0155 

.0155 

.0155 

.0155 

.0155 

.0155 

.0155 

.0155 

.0104 

.0104 

.0104 

.0104 

.0104 

.0104 

.0104 

.0104 

.0052 

.0052 

.0052 

.0052 

.0052 

.0052 

.0052 

.0052 

.0052 

.0052 

(calculated H 

ES 

IM 

EB 

EC 

I?M 

EC 

EB 

EB 

EC 

IM 

E?B 

EB 

EB 

EB 

EB 

EB 

EB 

EB 

EB 

IM 

EB 

EB 

EB 

EB 

EC 

EC 

IM 

IM 

IM 

EB 

EB 

EB 

EC 

ES 

EB 

EC 

EB 

IM 

s 

s 

s 

s 

s 

?S 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

s 

D 

s 

s 

s 

s 

s 

s 

s 

s 

s 

L: P.logP.) i=1 1. 1. 

epifaunal suspension feeder. The Spring Creek specimens differ from the species as described by N akazawa 

(1955) in having a highly convex left valve in early stages 

of growth, becoming more flattened in adult specimens. 
14 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

Newton (1983) considered the presence of Plicutala 

hekiensis to suggest Japanese zoogeographic influence 

on the Hells Canyon fauna; however, this form is now 

known to occur also in Late Triassic faunas on the North 

American craton in the Canadian Arctic Archipelago (T. 

Tozer and C. Newton, personal observations, 1983). It is 

therefore clear that P hekiensis was also part of the 

North American cratonal fauna during Late Triassic 

time. 

The epibyssate mytiloid Mysidiella cf M. americana (pl. 2.1, figs. 6-7, 10-11) and the shallow infaunal 

burrower Thtcheria densestriata (pl. 2.1, figs. 8-9), 

which are suspension feeders representing epibyssate 

and infaunal burrowing habits, respectively, are typical 

of Norian assemblages of central and northern Peru 

(Korner, 1937; Cox, 1949; C. Newton, personal observations of American Museum of Natural History collections, 1983). These two species also occur in the Norian 

carbonate rocks of the Chitistone Limestone in the 

Wrangell Mountains of Alaska (Newton, 1983). 

An unusual aspect of the early Norian silicified 

fauna of Hells Canyon is the occurrence of smooth trigoniaceans with trigoniid-grade dentition (usage of 

Newell and Boyd, 1975). Although many of the available 

specimens are fragmented, the Hells Canyon forms 

apparently have subrounded outlines, in contrast to 

smooth trigoniaceans with trigonal to cuneiform outlines described by Freneix and Avias (1977) from the 

Triassic rocks of New Caledonia. Smooth trigoniaceans 

with advanced-grade dentition have not previously been 

reported from the lower Mesozoic rocks of North America. 

DISCUSSION 

GENESIS OF THE SHELL BEDS 

The silicified shell beds at Spring Creek are interpreted as the product of storm winnowing and local 

transport of skeletal material. The shell beds conform 

well to the idealized proximal carbonate tempestite 

sequence proposed by Aigner (1982). Similarities 

include the presence of a basal scour surface, predominance of disarticulated bioclasts oriented generally parallel to bedding, overall normal grading of beds, relative 

thickness of bioclastic beds, prevalence of ripple crosslamination in upper parts of the sequence, and the 

presence of umbrella structures and other grain-sheltered patches. 

The main distinction between the Muschelkalk 

storm shell beds of southwestern Germany as described 

by Aigner (1977, 1982) and the bioclastic lenses discussed here is the nature of the background sedimentation. Fair-weather sediments of the Muschelkalk reflect 

low-energy sedimentation in an epicontinental nearshore zone subject to fluctuating salinity and temperature, whereas the sand-sized and winnowed [airweather sediments at Spring Creek represent an 

agitated, shallow subtidal oceanic environment. 

Storm sequences of the Upper Jurassic coquinoid 

quartz sandstones of Wyoming and Montana may 

provide a more fitting hydrodynamic analogue for the 

Spring Creek shell beds, as the energy levels in the [airweather sedimentary regimes are more similar. Brenner and Davies (1973) described three types of storm 

deposits that punctuate moderate- to high-energy 

marine bar facies from this region: swell lags, channel 

lags, and storm lags. Swell lags are composed largely of 

articulated fossils embedded in a muddy matrix, 

whereas channel lags and storm lags typically lack 

muddy matrix and are interbedded with sandstones. 

The channel lags, which are composed of bivalve fragments, are 1-3 m thick and exhibit both planar and 

festoon cross-stratification. The storm lag concentrations, which are most similar to the Spring Creek 

lenses, have erosive bases, thicknesses of 3-30 em, normal grading, and a geometry described as "sheetlike 

lens". Fossils observed in the Jurassic storm lags 

include brachiopods, pectinacean bivalves, oysters, and 

crinoids (Brenner and Davies, 1973). Thus, despite 

lithologic contrasts, the Jurassic storm lag concentrations of Wyoming and Montana compare very 

favorably with the Triassic shell beds at Spring Creek. 

Several properties of the storm-influenced stratigraphic sequence at Spring Creek readily distinguish it 

from basin-margin sequences containing sediment 

gravity flow deposits. Perhaps the most striking of these 

is the absence of lime mudstones of periplatform-ooze 

origin that are typically intercalated with gravity flow 

deposits in basin-margin settings (Cook and Mullins, 

1983). In the Spring Creek sequence the background 

sediment is winnowed carbonate sand rich in both peloids and coated grains, including ooids. This sandy 

background sediment is very similar in allochem composition to the peloidal, fine sand- to silt-sized matrix of 

the shell beds. The pelbiosparites between shell beds 

contain a sparse benthic fauna generally similar to that 

of the shell beds, in contrast to the pelagic, deep-water 

fauna of ammonoid cephalopods and halobiid bivalves 

expected on basin-margin slopes (see Hallam, 1981). 

Other features considered typical of basin-margin 

environments, such as debris flows, modified grain 

flows, slumps, slides, and large-scale truncation structures (Cook and Mullins, 1983), have also not been 

observed in the Martin Bridge at Spring Creek. All 

available biotic, petrographic, and stratigraphic evidence points, therefore, to a shallow-water origin for 

this sequence. 
2. LATE TRIASSIC BIVALVES OF THE MARTIN BRIDGE LIMESTONE, HELLS CANYON, OREGON 15 

TAPHONOMIC AND PALEOECOLOGIC IMPLICATIONS 

Although storm shell lags clearly cannot be analyzed as in situ representations of living benthic 

communities, the skeletal debris is not allochthonous in 

the sense of being derived from a distant source. Storm 

accumulations composed of fragmented shells are most 

properly considered as parautochthonous deposits 

(Aigner, 1982; Seilacher, 1982;) that sample all skeletons 

with sufficient mechanical strength and hydrodynamic 

properties over a geographic radius defined by the magnitude of the storm. In a particularly severe storm, such 

as hurricane Carla in 1961, shells can be displaced into 

water depths that vary as much as 25m from the original habitat, and mixing of several benthic communities 

is frequent (Hayes, 1967). Breakage, abrasion, and disarticulation of bivalved skeletons are typical in very 

severe storms, and these characteristics can be used to 

define such events in the stratigraphic record. 

The high frequency of disarticulation (>99 percent) 

of bivalves in the Spring Creek fauna indicates substantial postmortem, preburial physical transport and/or 

biological reworking of skeletal material. A further 

indication that bivalve shells may have had long residence times above the sediment-water interface is the 

presence of oyster encrustations on valve interiors and 

exteriors of Mysidioptera. An oysterlike bivalve found 

cemented to the upper surface of a spongiomorph colony 

similarly indicates that the colony remained upright 

above the sediment surface for a considerable time after 

death. 

Generalizations concerning the paleoecology of the 

communities sampled by the Spring Creek storm events 

are rendered possible by the relative ecologic homogeneity of the bivalve fauna. The Spring Creek bivalve 

fauna is an epifaunal, suspension-feeding assemblage 

whose ecological characteristics indicate a warm-water 

habitat. Spinose species are present (pl. 2.1, figs. 16-19) 

and cemented bivalves are common (table 2.1); modern 

bivalve species having these characteristics are confined 

to marine waters with annual minimum temperatures 

no lower than 10 oc and most commonly the minimum 

temperature for such forms is 20 oc (Nicol, 1967, 1978). 

A number of authors have made reference to 

reeflike structures in the Martin Bridge Limestone (for 

example, Nolf, 1966; Vallier, 1967). The relatively small 

proportion of scleractinian corals and spongiomorphs, 

and the absence of lithoclasts of coralline biolithite, 

indicate that the shell beds at Spring Creek were not 

derived from a major reef complex. Instead, the Spring 

Creek assemblages are the transported relics of levelbottom communities that were dominated by mollusks, 

but which also included isolated coral colonies or thickets. This is in agreement with the observation of Stanley 

(1979a,1979b)that most occurrences of Norian scleractinians in North America repesent small coral thickets rather than ecologic reefs. 

ZOOGEOGRAPHIC IMPLICATIONS 

Zoogeographic analysis of the Hells Canyon 

bivalves assigned to taxa previously described from 

other regions suggests a mixture of American and Japanese species. Septocardia, Mysidioptera williamsi, 

Mysidiella americana, and Tutcheria densestriata are 

unknown from continents other than the Americas, 

whereas Parallelodon monobensis and "Chlamys" 

mojsisovicsi are species hitherto reported only from 

Japan (Kobayashi and Ichikawa, 1949; Nakazawa, 1952, 

1955; Ichikawa, 1954; Tokuyama, 1960; Hayami, 1975). 

This faunal mixture among bivalves lends support to 

the paleogeographic reconstructions of Tozer (1982), 

who noted that archipelagoes in the Panthalassic ocean 

could have formed zoogeographic dispersal routes. As a 

result, the former archipelagoes that now constitute 

North American suspect terranes would preserve 

faunas of mixed zoogeographic affinities (Tozer, 1982). 

However, the dearth of adequate taxonomic information on early Mesozoic cratonal North American 

bivalves suggests caution in making such zoogeographic 

interpretations. No up-to-date taxonomic information is 

available, in particular, regarding Norian cratonic representatives of the families Pectinidae and Parallelodontidae, and it is hazardous to assume that "C." 

mojsisovicsi and P. monobensis do not occur in North 

America. Illustrating this point, Plicatula hekiensis is 

reported in the literature only from Japan (Nakazawa, 

1955; Hayami, 1975), but E.T. Tozer and I have recently 

(1983) observed it in underscribed samples from the 

Canadian Arctic Archipelago. Because American Triassic bivalve faunas have received much less taxonomic 

attention than those of other regions such as Japan 

(Hallam, 1981), the overall resemblance of the Spring 

Creek assemblage to cratonal North and South American faunas has probably been underestimated. 

SUMMARY AND CONCLUSIONS 

Richly fossiliferous lenses of early Norian silicified 

macrofossils found at the Spring Creek locality of the 

Wallowa Mountains-Seven Devils Mountains volcanic 

arc terrane formed in response to storm events that 

interrupted fair-weather sedimentation in an agitated, 

warm, shallow marine environment. Though transported, the Spring Creek bivalves uniformly indicate an 

epifaunal, suspension-feeding association that dwelled 

on a peloidal sand substrate during fair weather conditions. A large proportion (74 percent) of the bivalve 

species are new or indeterminate. The few bivalve species previously described from other regions reflect 
16 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

mixed zoogeographic affinities; species typical of eratonal North America, South America, and Japan are 

present. Such diverse affinities tend to support the early 

Mesozoic paleogeographic model of Cordilleran suspect 

terranes advanced by Tozer (1982): island archipelagoes 

positioned in central portions of ocean basins would be 

expected to have faunas of mixed zoogeographic 

alliance. I speculate, however, that the extent of North 

and South American faunal exchange with Cordilleran 

suspect terranes has likely been underestimated 

because of the impoverished state of the literature on 

cratonal American bivalves. 

REFERENCES CITED 

Aigner, T., 1977, Schalenpflaster im Unteren Hauptmuschelkalk bei 

Crailsheim (Wurtt., Trias, mol)-Stratinomie, Okologie, Sedimentologie: Neues Jahrbuch fur Geologie und Palaontologie, 

Abhandlungen, v. 153, p.193-217. 

---T., 1982, Calcareous tempestites: storm-dominated stratification in upper Muschelkalk limestones (Middle Trias, SW Germany), in Einsele, G., and Seilacher, A., eds., Cyclic and Event 

Stratification: New York, Springer, p. 180-198. 

Bohm, J., 1904, Ober die obertriadische Fauna der Bareninsel: Kungl. 

Svenska Vetenskapsakademien, Handlingar, Stockholm, v. 37, 

no. 3, 71 p. 

Brenner, R.L., and Davies, D.K., 1973, Storm-generated coquinoid 

sandstone: genesis of high-energy marine sediments from the 

Upper Jurassic of Wyoming and Montana: Geological Society of 

America Bulletin, v. 84, p. 1685-1698. 

Brooks, H.C., and Vallier, T.L., 1978, Mesozoic rocks and tectonic 

evolution of eastern Oregon and western Idaho, in Howell, D.G., 

and McDougall, K.A., eds., Mesozoic paleogeography of the Western United States: Los Angeles, Calif., Pacific Section, Society of 

Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 2, p. 133-145. 

Burke, D.B., and Silberling, N.J., 1973, The Auld Lang Syne Group of 

Late Triassic and Jurassic(?) age, north-central Nevada: U.S. 

Geological Survey Bulletin 1394-E, 14 p. 

Chaney, R.W., 1932, Central Oregon: International Geological Congress, 16th, Washington, D.C., 1933, Guidebook 21, Excursion 

C-2, 14 p. 

Coney, P.J., Jones, D.L., and Monger, J.W.H., 1980, Cordilleran suspect 

terranes: Nature, v. 288, p. 329-333. 

Cook, H.E., and Mullins, H.T., 1983, Basin margin environments, in 

Scholle, P.A., Bebout, D.G., and Moore, C.H., Carbonate depositional environments: American Association of Petroleum 

Geologists Memoir 33, p. 540-617. 

Cox, L.R., 1949, Upper Triassic Mollusca from Peru: Instituto Geologico del Peru, no. 12, p. 5-50. 

Cox, L.R., Newell, N.D., and others, 1969, Bivalvia: Treatise on Invertebrate Paleontology, Part N, 2 vols., 951 p. 

Freneix, S., and Avias, J., 1977, Caledogonia, a new smooth trigoniacean bivalve from the Triassic ofNew Caledonia: Alcheringa, v. 1, 

p. 279-291. 

F\irsich, F.T., and Wendt, J., 1977, Biostratinomy and paleoecology of 

the Cassian Formation (Triassic) of the southern Alps: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 22, p. 

257-323. 

Gilluly, J., Reed, J.C., and Park, C.F., 1933, Some mining districts of 

eastern Oregon: U.S. Geological Survey Bulletin 846, 140 p. 

Hall, J., and Whitfield, R.P., 1877, Paleontology: U.S. Geological Survey Exploration of the 40th Parallel, Report, v. 4, pt. 2, p. 193-302. 

Hallam, A., 1981, The end-Triassic bivalve extinction event: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 36, p. 1-44. 

Hamilton, W, 1963, Metamorphism in the Riggins region, western 

Idaho: U.S. Geological Survey Professional Paper 436, 95 p. 

Hayami, I., 1975, A systematic survey of the Mesozoic Bivalvia from 

Japan: University ofTokyo, University Museum Bulletin, no. 10, 

249 p. 

Hayami, I., Maeda, S., and Fuller, C.R., 1977, Some Late Triassic 

Bivalvia and Gastropoda from the Domeyko Range of Chile: 

Transactions and Proceedings of the Palaeontological Society of 

Japan, no. 108, p. 202-221. 

Hayes, M.O., 1967, Hurricanes as geological agents: case studies of 

hurricanes, Carla, 1961, and Cindy, 1963: University of Texas 

Bureau of Economic Geology Report of Investigations, no. 61, 

54 p. 

Hillhouse, J.W., Gromme, C.S., and Vallier, T.L., 1982, Paleomagnetism and Mesozoic tectonics of the Seven Devils volcanic arc in 

northeastern Oregon: Journal of Geophysical Research, v. 87, 

p. 3777-3794. 

Ichikawa, K., 1954, Late Triassic pelecypods from the Kochigatani 

Group in the Sakuradani and Kito areas, Tokushima Prefecture, 

Shikoku, Japan. Part III: Osaka University, Institute of Polytechnics, Journal, Ser G, v. 2, p. 53-75. 

Jones, D.L., Howell, D.G., Coney, P.T., and Monger, J.W.H., 1983, Recognition, character, and analysis of tectonostratigraphic terranes in western North America, in Hashimoto, M., and Uyeda, 

S., eds., Accretion tectonics in the circum-Pacific regions: Tokyo, 

Torra Scientific, p. 21-35. 

Jones, D.L., Irwin, W.P., and Ovenshine, A.T., 1972, Southeastern 

Alaska-a displaced continental fragment?: U.S. Geological 

Survey Professional Paper 800-B, p. B211-B217. 

Jones, D.L., and Silberling, N.J., 1979, Mesozoic stratigraphy-the 

key to tectonic analysis of southern and central Alaska: U.S. 

Geological Survey Open-File Report 79-1200, 37 p. 

Jones, D.L., Silberling, N.J., Gilbert, W, and Coney, P.J., 1982, 

Character, distribution, and tectonic significance of accretionary 

terranes in the Alaska Range: Journal of Geophysical Research, 

v. 87, p. 3709-3717. 

Jones, D.L., Silberling, N.J., and Hillhouse, J.W., 1977, Wrangellia-a 

displaced terrane in northwestern North America: Canadian 

Journal of Earth Sciences, v. 14, p. 2565- 2577. 

---1978, Microplate tectonics of Alaska-significance for the 

Mesozoic history of the Pacific coast of North America, in Howell, 

D.G., and McDougall, K.A., eds., Mesozoic paleogeography of the 

Western United States: Los Angeles, Calif., Pacific Section, 

Society of Economic Paleontologists and Mineralogists, Pacific 

Coast Paleogeography Symposium 2, p. 71-74. 

Keen, A.M., 1980, The pelecypod family Cardiidae: a taxonomic summary: Tulane Studies in Geology and Paleontology, v. 16, p. 1-40. 

Kobayashi, T., and Ichikawa, K., 1949, 1bsapecten, gen. nov., and other 

Upper Triassic Pectinidae from the Sakawa basin, in Shikoku, 

Japan: Japanese Journal of Geology and Geography, v. 21, p. 

163-176. 

Korner, K., 1937, Marine (Cassianer-Raibler) Trias am Nevado de 

Acrotambo (Nord- Peru): Palaeontographica, Ser. A, v. 86, 

p.145-235. 

Laudon, T.S., 1956, The stratigraphy of the Upper Triassic Martin 

Bridge Formation and "Lower Sedimentary Series" of the northern Wallowa Mountains, Oregon: Madison, University ofWisconsin, M.S. thesis, 100 p. 

Laws, R.A., 1982, Late Triassic depositional environments and mol-
2. LATE TRIASSIC BIVALVES OF THE MARTIN BRIDGE LIMESTONE, HELLS CANYON, OREGON 17 

luscan associations from west-central Nevada: Palaeogeography, 

Palaeoclimatology, Palaeoecology, v. 37, p.131-140. 

Lindgren, W., 1901, The gold belt of the Blue Mountains of Oregon: U.S. 

Geological Survey, 22nd Annual Report, pt. 2, p. 551-776. 

McLearn, F.H., 1940, Triassic of Beattie Hill, Peace River Foothills, 

B.C.: Canadian Field-Naturalist, v. 54, p. 79-82. 

---1941a, Preliminary descriptions of some new Triassic pelecypods from the Peace River foothills, B.C.: Canadian FieldNaturalist, v. 55, p. 31-34. 

--1941b, Triassic stratigraphy, Mahaffy Cliffs to Red Rock Spur, 

Peace River foothills, B.C.: Canadian Field-Naturalist, v. 55, p. 

95-100. 

Montanaro Gallitelli, E., Russo, A., and Ferrari, P., 1979, Upper Triassic coelenterates of western North America: Bollettino della 

Societa Paleontologica ltaliana, v. 18, p. 133-156. 

Muffler, L.J.P., 1967, Stratigraphy of the Keku Islets and neighboring 

parts ofKuiu and Kupreanoflslands, southeastern Alaska: U.S. 

Geological Survey Bulletin 1241-C, 52 p. 

Nakazawa, K., 1952, A study on the pelecypod-fauna of the Upper 

Triassic Nabae Group in the northern part of Kyoto Prefecture, 

Japan. Part 1: Pectinids and limids: University of Kyoto, College 

of Science Memoirs, Ser. B, v. 20, p. 95-106. 

---1955, A study on the pelecypod-fauna of the Upper Triassic 

Nabae group in the northern part of Kyoto Prefecture, Japan. 

Part 3: Halobiids and others: University of Kyoto, College of 

Science Memoirs, Ser. B, v. 22, p. 243-260. 

Newell, N.D., and Boyd, D.W., 1975, Parallel evolution in early trigoniacean bivalves: American Museum of Natural History Bulletin, v. 154, p. 53-162. 

Newton, C.R., 1983, Paleozoogeographic affinities of Norian bivalves 

from the Wrangellian, Peninsular, and Alexander terranes, in 

Stevens, C.H., ed., Pre-Jurassic rocks in western North American suspect terranes: Los Angeles, Calif., Pacific Section, 

Society of Economic Paleontologists and Mineralogists, p. 37-48. 

Nichols, K.M., and Silberling, N.J., 1977, Stratigraphy and depositional history of the Star Peak Group (Triassic) northwestern 

Nevada: Geological Society of America Special Paper 178, 73 p. 

Nicol, D., 1967, Some characteristics of cold-water marine pelecypods: 

Journal ofPaleontology, v. 41, p. 1330-1340. 

---1978, Shell-cemented pelecypods: Florida Scientist, v. 41, p. 

39-41. 

Nolf, B.O., 1966, Structure and stratigraphy of part of the northern 

Wallowa Mountains, Oregon: Princeton, New Jersey, Princeton 

University, Ph.D. dissertation, 135 p. 

Ross, C.P., 1938, The geology of part of the Wallowa Mountains, 

Oregon: Oregon Department of Geology and Mineral Industries 

Bulletin 3, 74 p. 

Sarewitz, D., 1983, Seven Devils terrane: is it really a part of 

Wrangellia?: Geology, v. 11, p. 634-637. 

Seilacher, A., 1982, General remarks about event deposits, in Einsele, 

G., and Seilacher, A., eds., Cyclic and Event Stratification: New 

York, Springer, p. 161-174. 

Sengor, A.M.C., 1979, Mid-Mesozoic closure ofPermo-Triassic Tethys 

and its implications: Nature, v. 279, p. 590-593. 

Silberling, N.J., 1959, Pre-Tertiary stratigraphy and Upper Triassic 

paleontology of the Union district, Shoshone Mountains, 

Nevada: U.S. Geological Survey Professional Paper 322, 67 p. 

---1961, Upper Triassic marine mollusks from the Natchez Pass 

Formation in northwestern Nevada: Journal of Paleontology, v. 

35, p. 535-542. 

---1983, Stratigraphic comparison of the Wallowa and Huntington 

terranes, northeast Oregon [abs.]: Geological Society of America 

Abstracts with Programs, v. 15, p. 372. 

Silberling, N.J., and Tozer, E.T., 1968, Biostratigraphic classification of 

the marine Triassic in North America: Geological Society of 

America Special Paper 110, 63 p. 

Silberling, N.J., and Wallace, R.E., 1969, Stratigraphyofthe Star Peak 

Group (Triassic) and overlying Lower Mesozoic rocks, Humboldt 

Range, Nevada: U.S. Geological Survey Professional Paper 592, 

50 p. 

Smith, J.P., 1927, Upper Triassic marine invertebrate faunas of North 

America: U.S. Geological Survey Professional Paper 141, 262 p. 

Smith, W.D., and Allen, J.E., 1941, Geology and physiography of the 

northern Wallowa Mountains, Oregon: Oregon Department of 

Geology and Mineral Industries Bulletin, v. 12, 65 p. 

Stanley, G.D., 1979a, Paleoecology, structure, and distribution of Triassic coral buildups in western North America: University of 

Kansas Paleontological Contributions, Article 65, 58 p. 

---1979b, Triassic carbonate buildups of western North America: 

comparisons with the Alpine Triassic of Europe: Rivista Italiana 

di Paleontologia e Stratigrafia, v. 85, p. 877-894. 

---this volume, Upper Triassic coelenterate faunas of western 

Idaho and northeastern Oregon: implications for biostratigraphy and paleogeography: U.S. Geological Survey Professional 

Paper 1435. 

Stanley, S.M., 1970, Relation of shell form to life habits ofthe Bivalvia 

(Mollusca): Geological Society of America Memoir 125, 296 p. 

Tokuyama, A., 1960, On the pelecypod fauna of the Late Triassic 

Hirabara Formation in west Japan: Japanese Journal of Geology 

and Geography, v. 31, p. 201-218. 

Tozer, E.T., 1965, Upper Triassic ammonoid zones of the Peace River 

foothills, British Columbia, and their bearing on the classification of the Norian stage: Canadian Journal of Earth Sciences, v. 

2, p. 216-226. 

---1982, Marine Triassic faunas of North America: their significance for assessing plate and terrane movements: Geologische 

Rundschau, v. 71, p.1077-1104. 

Vallier, T.L., 1967, The geology of part of the Snake River canyon and 

adjacent areas in northeastern Oregon and western Idaho: Corvallis, Oregon State University, Ph.D. dissertation, 267 p. 

---1974, A preliminary report on the geology of part of the Snake 

River canyon, Oregon and Idaho: Oregon Department of Geology 

and Mineral Industries Geological Map Series GMS-6, 15 p. 

---1977, The Permian and Triassic Seven Devils Group, western 

Idaho and northeastern Oregon: U.S. Geological Survey Bulletin 

1437,58 p. 

Vermeij, G.J., 1978, Biogeography and adaptation: Cambridge, Harvard University Press, 332 p. 

Wendt, J., and F\irsich, F.T., 1980, Facies analysis and palaeogeography of the Cassian Formation, Triassic, southern Alps: Rivista 

ltaliana di Paleontologia e Stratigrafia, v. 85, p. 1003-1027. 

PLATE 2.1 

[Contact photograph of the plate in this chapter is available, at cost, from U.S. Geological Survey 

Library, Federal Center, Denver, Colorado 80225] 
PLATE2.1. 

[Figures natural size unless otherwise indicated. All specimens coated with ammonium cloride] 

FIGURES 1-5. Cassianella cf C. angusta Bittner. USGS Mesozoic loc. M2672 

1. Left valve interior. 

2. Left valve exterior. 

3. Fragmentary right valve exterior ( x 1.5). 

4. Left valve interior (ventral periphery and posterior broken). 

5. Left valve exterior (ventral periphery and posterior broken). 

6, 7, 10, 11. Mysidiella cf M. americana Korner. USGS Mesozoic loc. M2672. 

6. Left valve exterior of fractured specimen. 

7. Left valve interior offractured specimen (part of hinge-covering plate on 

anterior margin is broken away). 

10. Left valve interior with unbroken hinge area. 

11. Left valve exterior. 

8, 9. Tutcheria densestriata (Korner). USGS Mesozoic loc. M2672. 

8. Right valve exterior (periphery broken) ( x 1.5). 

9. Right valve interior (periphery broken) ( x 1.5). Note denticulation of inner 

shell margin. 

12, 13. "Septocardia" sp. USGS Mesozoic loc. M2672. 

12. Right valve exterior ( x 2). 

13. Right valve interior ( x 2). 

14, 15. Mysidioptera williamsi (McLearn). USGS Mesozoic loc. M2672. 

14. Detail ofleft hinge, illustrating single ligament pit. 

15. Left valve exterior (anterior, ventral margin broken). 

Note fragments of cemented oysterlike bivalve in central posterior region; 

echinoid spine cemented to center of valve; and left valve of Parallelodon on 

mid-posterior part of shell. 

16-19. Plicatula hekiensis Nakazawa. USGS Mesozoic loc. M2672. 

16. Left valve exterior ( x 1.5). Spinose outer shell layer absent over much of 

valve. 

17. Left valve interior ( x 1.5). 

18. Left valve interior ( x 1.5). 

19. Left valve exterior ( x 1.5). 

20, 21. Parallelodon aff. P monobensis Nakazawa. USGS Mesozoic loc. M2672. 

20. Right valve exterior ( x 1.5). 

21. Right valve interior ( x 1.5). 

22, 23. Parallelodon cf. P monobensis Nakazawa. USGS Mesozoic loc. M2672. 

22. Right valve exterior. 

23. Right valve interior. 
U.S ~ GEOLOGICAL SURVEY PROFESSIONAL PAPER 1435 PLATE 2.1 

1 2 3 

4 5 

8 9 

6 7 10 11 

14 

12 

18 19 

20 21 

22 23 15 

CASSJANELLA, MYSIDIELLA, TUTCHERIA, ~~EPTOCARDIA," 

MYSJDJOPTERA, PLICA TULA, PARALLELODON 

3. LATE TRIASSIC COELENTERATE FAUNAS OF WESTERN IDAHO AND 

NORTHEASTERN OREGON: IMPLICATIONS FOR BIOSTRATIGRAPHY 

AND PALEOGEOGRAPHY 

By GEORGE D. STANLEY, jR. 1 

ABSTRACT 

Rich collections of Late Triassic corals and spongiomorphs 

provide useful new data for biostratigraphic and paleogeographic 

studies of western Idaho and northeastern Oregon. The systematic 

standing of some of the corals is clarified and a new species, Cyathocoenia squiresi, is designated. The identification and stratigraphic 

distribution of 49 taxa of scleractinian corals and spongiomorphs from 

the Wallowa Mountains, Hells Canyon, and a locality near Lewiston, 

Idaho, allow comparison with faunas from Vancouver Island, British 

Columbia, and the Wrangell Mountains, Alaska. These data show a 

differentiation of early and late Norian faunas. Certain characteristic 

coral species are useful, in the absence of more diagnostic fossils, in 

recognizing the Kerri and Crickmayi Zones in the Upper Triassic 

rocks. 

The coelenterate faunas occur in distinct horizons and are 

clearly of warm shallow- water origin. Although true reef structure is 

absent, the corals locally form rich biostromal deposits 1-12 m thick, 

in association with a variety of other benthic invertebrates including 

molluscs and echinoderms. 

Strong Tethyan affinities of the coelenterates are clearly evident 

at some localities, as much as 75 percent of the fauna are conspecific 

with distant counterparts in alpine regions of central Europe. Dispersal of corals within the Triassic Panthalassa Sea was probably facilitated by the presence of numerous small continental and volcanic 

islands which were probably scattered throughout the ancestral 

Pacific. Distances between these islands and the presence of intervening bodies of deeper water may explain marked differences between 

coelenterate faunas from widely distributed terranes now part of 

North America. 

Comparisons with presumably contemporaneous early Norian 

coelenterate faunas from other regions show surprisingly little similarity. Such findings necessitate critical evaluation of Late Triassic 

paleogeography and perhaps a re-examination of relationships 

between Wrangellia and the Wallowa terrane. 

INTRODUCTION AND PAST WORK 

Triassic coelenterate faunas of North America have, 

until recently, received relatively little study. They were 

first made known by Smith (1912), who discussed the 

occurrence of Late Triassic coral reefs in the Wallowa 

Mountains of Oregon, western Nevada, and Alaska. 

Smith's idea of an early Norian north-south coral reef 

belt quickly caught the attention of geologists the world 

1Department of Geology, University ofMontana, Missoula, MT 59812 

over. Dacque (1915) referred to it in his textbook on 

paleogeography and Koppen and Wegener (1924) used it 

in the context of newly emerging ideas on continental 

drift. Smith (1927) described and illustrated the coral 

and hydrozoan taxa and noted the striking similarities 

to counterparts in reef sequences of the Alps. Few 

details of the so-called reefs were given, but nevertheless the idea of a coral reef belt, widely distributed 

with respect to latitude along the western margin of 

North America, became firmly rooted in the minds of 

stratigraphers, paleoclimatologists, and paleogeographers (Opdyke, 1962; Schwarzbach, 1974; Dott and 

Batten, 1976). Major problems revolved around explaining the high latitude occurrences of these "reefs" as well 

as the high levels of similarity with distant counterparts 

in Europe (Smith, 1927). 

Stanley (1979) conducted regional studies of some 

important localities in California, Nevada, Oregon, 

Idaho, Canada, and Alaska and established that few if 

any of these occurrences are true reefs in the ecologic 

sense of living counterparts. Most of the limestone 

sequences are small in scale compared with alpine counterparts, and the coral deposits that occur in these 

sequences are thin and laterally restricted. In addition 

to corals and hydrozoans, a variety of other groups 

including sponges, brachiopods, molluscs, and echinoderms are present. The coral deposits are locally thin 

and do not form extensive organic frameworks, and 

where they are the principal components of fauna, they 

show little evidence of having developed in high-energy 

wave environments. The localities range in age from 

Ladinian to latest Norian and thus cannot all be 

assigned to a single lower Norian coral zone such as that 

envisioned by Smith (1927). In terms of their stratigraphic and paleoecologic settings, the corals bear little 

resemblance to the well- developed reef sequences of the 

Alps (Stanley, 1980). In terms of their taxonomic composition, however, much similarity exists. 

Most coral localities in the Western United States, 

Canada, and Alaska are Norian in age (Stanley, 1982), 

but because shalllow-water sequences commonly lack 

the ammonites and halobiid and monotid bivalves 

23 
24 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

characteristic of open or deeper water, precise dating 

and chronostratigraphic correlations have been difficult. As discussed below, some coral taxa hold potential 

for resolving biostratigraphic correlations. 

The development of the concept of displaced terrane 

and its application to widely distributed rocks of western North America (Jones and others, 1982) has 

provided a new way to explain the present distributions 

of the coral faunas. Careful evaluation of these faunas 

and other Triassic benthic invertebrates from diverse 

terranes provides a basis for assessing ideas on the 

origins and subsequent tectonic displacements of these 

allochthonous units. Although the shallow-water 

benthic faunas have long been known, they have 

received relatively little attention and have not been 

utilized on any large scale for paleogeographic studies. 

Current work by Peter Hoover (Paleontological 

Research Institute, Ithaca) on brachiopods, Cathryn 

Newton (Syracuse University) on molluscs, and Porter 

Kier (Smithsonian Institution) on echinoids, promise 

additional fruitful contributions to the paleogeographic 

issues. 

This paper discusses some of the coral faunas that 

are unique to northeastern Oregon and western Idaho. 

Many of these faunas are silicified and thus well preserved and are among the richest coral faunas in North 

America. Upper Triassic corals discussed in this paper 

come from three principal areas: (1) the southern Wallowa Mountains, along Eagle Creek in northeastern 

Oregon, (2) the Nez Perce Indian Reservation south of 

Lewiston, Idaho, on Mission Creek, and (3) Hells Canyon, near the Snake River between Oregon and Idaho 

(fig. 3.1). The first two areas have been previously studied (Stanley, 1979) and I have recently examined the 

Hells Canyon locality. The rich faunas of these areas 

may be compared not only with each other but also with 

more distant faunas. Data generated from such comparisons provide powerful tools for solving biostratigraphic and paleogeographic problems. 

ACKNOWLEDGMENTS 

This project was supported by faculty research 

grants (1983-84 and 1985-86) from the University of 

Montana. Initial support by the Smithsonian Institution, and collaboration with colleagues there, is gratefully acknowledged. Later stages of this work were 

supported by a National Science Foundation Grant 

(EAR-8306421). 

Raylene Beier assisted in editing and organizing 

the manuscript, and the University of Montana Department of Geology supported the photographic and drafting work and the preparation of the manuscript. T.L. 

Vallier and H.C. Brooks served as critical reviewers of 

Lake Iliamna, Alaska 

• Wrangell Mountains, Alaska __ ___, 

• Lake Cowichan, 

/ 

( 

) 

i /~' i 

''\... 

'· I '< 

/ 

/ 

/ 

\.. 

l 

\ 

I 

...... 

I '" ....... 

/ 

......... \ • Lewiston, Idaho-------+-~"' ""- \ '-.....C' ; 

0 500 KILOMETERS 

/ J-{'t-4 

; IJ. s...PA . . ,. 4."--' 

) 

I 

\ 

' ''!· ............. ...... . 

....... ........ 

FIGURE 3.1.-Locations of important Late Triassic coelenterate faunas 

in western North America. The stippled region indicates the general 

extent of the postulated Wrangellia terrane (Jones and others, 1977). 

Squares to the left oflocality names show localities discussed in this 

report. 

the manuscript and C.R. Newton and J.A. Grant-Mackie 

provided additional comments. Dr. E. Roniewicz kindly 

reviewed the systematic part. Many constructive comments offered by N.J. Silberling and other reviewers 

were incorporated in the final draft, but the ideas presented and the conclusions drawn are entirely my own. 

STRATIGRAPHY AND PALEOECOLOGY OF THE 

CORALS 

The Triassic corals reported by Smith (1912, 1927) 

come from the type section of the Martin Bridge Limestone (Vallier, 1977) on Eagle Creek in the southern 

Wallowa Mountains, Oregon. As described by Ross 

(1938), the strata are interbedded massive and thinbedded limestone and shale about 460 m thick. The 

lower part of the sequence is characteristic of turbiditic 
3. LATE TRIASSIC COELENTERATE FAUNAS OF WESTERN IDAHO AND NORTHEASTERN OREGON 25 

sedimentation (Folio, 1985). The corals occur within a 

thin- bedded limestone about 12 m thick and their early 

Norian age is established by Halobia species that occur 

above and below these coral beds (Smith, 1927). A reinvestigation of calcareous argillaceous beds below the 

coral limestone, with rich ammonite and halobiid 

bivalve faunas (J. A. Grant-Mackie, in preparation) suggests that they span the Karnian- Norian boundary 

through the base of the Kerri zone. In this respect these 

beds could be unique to North America, yielding a biostratigraphic boundary previously unrecognized. Solitary, branching, and encrusting corals dominate. 

Unfortunately, the fossiliferous section containing the 

corals described and collected by Smith (1927, p. 10) has 

been covered by the construction of a road high on the 

east side of the creek. Coral collections were made from 

surrounding areas (Stanley, 1979); but owing to lack of 

silicification, large numbers of specimens are not available. In the northern Wallowa Mountains near Joseph, 

Oregon, similar Upper Triassic limestone has been correlated with the Martin Bridge Limestone (Nolf, 1966), 

but structural complications and metamorphism of the 

rocks, coupled with their isolation from Martin Bridge 

outcrops to the south, partially obscure the relationships. Nolf (1966) established a stratigraphic 

sequence in the northern Wallowa Mountains which is 

generally similar to that of the type locality on Eagle 

Creek, but he recognized various members not distinguishable at the type locality. My preliminary observations of the fossils and rock types at the type locality, 

suggest that this sequence, relative to that of the southern Wallowas, . represents a deeper water, more distal 

shelf setting than that at the northern Wallowa locality. 

In both localities, corals are concentrated in thin biostromal beds 1-12 m thick. Although this paper deals 

mostly with corals from the Eagle Creek locality, silicified coral faunas from the northern Wallowa Mountains are now under study, and preliminary findings 

support the early Norian age assigned by Smith (1927) 

for both localities. 

On Mission Creek, near Lewiston, Idaho, the limestone in an isolated quarry was reported by Cooper 

(1942) to be richly fossiliferous. This locality contains at 

least 150m of limestone. Thin horizons near the base 

and top of the quarry have yielded a wealth of silicified 

Late Triassic fossils. The limestone is an inlier surrounded by extensive Upper Tertiary basalts, so physical correlations outside the outcrop area have not been 

possible. The coral fauna from this quarry was first 

studied by Squires (1956). Stanley (1979) illustrated 

some of the rich silicified sponge, coral, and bivalve taxa 

that indicated a late Norian age. The recrystallized 

limestone is lithologically similar to the Martin Bridge 

Limestone. Silicified fossils form thin beds at several 

horizons. The locality is unique in having such a rich 

silicified benthic invertebrate fauna of Late Triassic age. 

It is also the easternmost exposure of marine Upper 

Triassic limestone known in the United States, lying 

about 50 km east of the easternmost outcrop of known 

Upper Triassic limestone assigned to the Martin 

Bridge. 

Near the Snake River in Hells Canyon, along the 

border of Idaho and Oregon, Upper Triassic limestone 

about 500 m thick lies above the Triassic part of the 

Seven Devils Group (Vallier, 197 4, 1977). Most of the 

limestone is recrystallized, but some thin beds yield an 

abundant silicified fauna especially rich in molluscs. 

Corals and spongimorphs are present in one such mollusc bed north of Spring Creek (USGS locality M2672), 

which is interpreted as a subtidal storm deposit (Newton, this volume). The corals were described by Montanaro Gallitelli and others (1979), and the specimens 

illustrated by them are now in the United States 

National Museum. Coelenterates are not a very significant component of the fauna, with corals and 

spongiomorphs occurring mainly as debris. Most of the 

corals have sheet-like growth forms, and some appear to 

have encrusted the molluscan shell material. There is 

no organic framework structure, even of small size. 

Characteristics of the carbonate rocks at Hells Canyon, 

as well as the general stratigraphic relationships, are 

similar to those of the Martin Bridge Limestone in the 

Wallowa Mountains. Fossils at both localities occur in 

thin beds of silicified, highly concentrated invertebrates 

separated by thick intervals of recrystallized limestone, 

seemingly barren of fossils. 

Details of the paleoecology of Triassic corals were 

given by Stanley (1979, 1980). Late Triassic coral faunas 

from both western North America and the Alps occur in 

a variety of rock types indicating a great range of depositional environments. These include shallow lagoon, 

reef, and deeper, basinal shelf-slope environments. The 

coral taxa are remarkably undifferentiated with respect 

to the various environments (Stanley, 1979, 1980, 1982). 

In terms of their ecologic preferences, corals of the Triassic do not appear to have been as closely adjusted to 

specific habitats as their Cenozoic and living counterparts (Stanley, 1981). 

Rather than inhabiting high-energy, shelf-edge 

environments, such as found on crests of modern coral 

reefs, most Triassic corals appear to have preferred 

lower energy, more protected or quieter environments, 

such as lagoon, protected shoal, and deeper shelf slope 

within a broad carbonate platform. Rather than a gently 

sloping reef, the ramp model proposed by Armstrong 

and others (1969) for Alaska, appears more applicable to 

the bedded Upper Triassic limestone of Oregon and 

Idaho. Thus, no true Triassic coral reefs were thought to 
26 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

be present in North America. This idea has now been 

challenged by the discovery of a massive-bedded, coraldominated reef in the southern Wallowa Mountains, 

near the Martin Bridge type locality at Eagle Creek 

(Stanley and Senowbari-Daryan, 1986). Sedimentological and paleontological characteristics are strikingly similar to the Upper Triassic Dachstein Reef 

Limestone of the Austrian and German Alps (Zankl, 

1971) and contrast markedly with Wrangellian 

sequences. 

THE COELENTERATE FAUNAS 

A total of 40 coral and 9 spongiomorph taxa are 

known from the Upper Triassic localities of northeastern Oregon, western Idaho, Vancouver Island, and 

the Wrangell Mountains of Alaska (fig. 3.1 and table 3.1). 

While some of these coelenterates are endemic to North 

America, a large number also occur in alpine reef 

sequences of central Europe. Considering all49 taxa, 55 

percent are conspecific with Late Triassic alpine forms 

from the Tethys region of central Europe. Most of those 

come from the Norian Zlambach beds of Austria (Frech, 

1890). 

Of the nine spongiomorph taxa recognized (table 

3.1) only two are known outside North America. 

Although subordinate to the corals, spongiomorphs are 

also important elements of the fauna in Hells Canyon 

and the Wallowa and Wrangell Mountains. Some 

branching forms such as Spongiomorpha ramosa 

resemble dendroid corals, and if the limestone matrix is 

strongly recrystallized, they might be confused with 

branching corals such as Retiophyllia. At the Lewiston 

locality, however, spongiomorphs are rarer and corals 

are much more important. 

The names of the scleractinian coral taxa listed in 

table 3.1 are based on a number of systematic studies 

(Smith, 1927; Squires, 1956; Montanaro Gallitelli and 

others, 1979). The generic and specific names reflect 

major new revisions that have taken place through systematic studies ofTriassic corals by French and Russian 

workers (Cuif, 1965, 1972, 1974a,b, 1975, 1976; 

Melnikova, 1967,1968,1971,1972, 1975). The affinities of 

the spongiomorph taxa listed in table 3.1 are currently 

the subject of discussion (Fhigel, 1981). Instead of the 

traditional view as hydrozoans, some workers today 

regard them as stromatoporoid sponges. Although 

occurring with corals, these fossils are not corals and 

may not even be true coelenterates. However, they are 

discussed with the corals in this paper. Further work is 

needed to clarify their systematic standing. 

Many of the North American corals are certainly 

conspecific with alpine taxa. The Norian alpine species 

are numerous and exquisitely preserved, mostly in original aragonite (Frech, 1890). The major problem arising 

in the systematic classification of North American corals is that before they can be precisely identified, they 

must be compared with the classic Norian types. These 

have been re-evaluated by Cuif (1965, 1972, 197 4a,b, 

1975, 1976), who, from details of their microstructure, 

has proposed many major revisions at generic and family levels. The Late Triassic corals of North America can 

certainly be considered well preserved because of their 

silicified nature, which reveals good surface details. 

Microstructural details, so important for comparison 

with the type species, are not present. Consequently 

many workers have adopted different approaches 

(Melnikova, 1971,1972, 1975; Roniewicz, 1974). The only 

practical and objective way to classify silicified North 

American corals is to justify observable macroscopic 

characteristics by use of the better preserved alpine 

materials, incorporating the newly proposed names 

where appropriate. A new study of the alpine Norian 

coral types, currently underway by Dr. E. Roniewicz 

(Warsaw), may produce some changes, but the integrity 

of the individual coral taxa recognized herein should not 

be greatly affected. 

Based on published information on localities in 

Oregon and Idaho, the Lewiston site, where 18 taxa are 

known, has the highest coelenterate diversity. The 

lowest diversity is in the Wallowa Mountains (12 taxa) 

and Hells Canyon, where 15 taxa are present. The 

coelenterate taxa described by Montanaro Gallitelli and 

others (1979) come from Hells Canyon (table 3.1). Significant parts of the carbonate sequence are so recrystallized as to make recognition of original fossils, textures, 

and microfacies types difficult, and therefore silicified 

intervals provide the bulk of information on the fauna. 

Equally rich silicified coral faunas occur within carbonate rocks in other areas such as Vancouver Island, where 

15 taxa are known, and in the Wrangell Mountains of 

Alaska (U.S.G.S. locality M1708), where 15 taxa are 

present. 

Applying Odum's (1971) index of similarity to the 

data in table 3.1, comparison of the presence-absence 

data from the various localities shows few striking 

examples of high similarity (table 3.2). The highest 

value (0.67) occurs between Lewiston and Vancouver 

Island. Lower levels are found between silicified faunas 

of Hells Canyon and the Wrangell Mountains (0.33), and 

Lewiston and Hells Canyon (0.24). No similarity exists 

between the Wallowa Mountains and Hells Canyon. 

Chronostratigraphic control based on fossils at these 

localities, is not continuous, but the corals occur mostly 

in thin beds dated as early Norian. It is difficult to assess 

the validity of Smith's (1927) proposed universal lower 

Norian coral zone. Certainly many examples are early 

Norian in age, and these may very well occur at consistent stratigraphic horizons. However, Karnian examples and one Ladinian (Middle Triassic) example are 
3. LATE TRIASSIC COELENTERATE FAUNAS OF WESTERN IDAHO AND NORTHEASTERN OREGON 27 

TABLE 3.1.-Coral and spongiomorph species at localities in northeastern Oregon, western Idaho, southern Vancouver Island and the Wrangell 

Mountains with occurrences in the Tethys region of Europe and Thrkey 

[X, occurrence , based on published reports of Smith (1972), Squires (1957), Stanley (1979), Montanaro-Gallitelli and others (1979), and this paper with synonymization of generic and 

specific names with more recent systematic revisions. Tethyan occurrences only shown for those species reported from North American localities; all specimens on which this table is 

based are housed in the U.S. National Museum, University of Kansas Museum of Invertebrate Paleontology, and the University of Montana Museum of Paleontology] 

Oregon - Idaho Canada - Alaska 

(I) H (I) 

0 0 Q) ,....; ~ 

Cll 'M 0 :> .-1-M 

~ Cll +.J ~ ::1'"0 Q) Cll +.J (I) (I) 0 0 ~ 00+-J Tethys ,....; ~ -M ,....; >. () Cll ~ ~ 

Species ,....; ::I ~ ,....; ~ 0.-1 Cll ::I Region Cll 0 Q) Q) Cll Cll (I) H 0 

;3:::>:! ...4 o::u :>H ;3:::>:! 

CORALS 

Actinastraea (?) sp. M. Gallitelli and others X 

Ampakabastraea aff. nodosa Cuif ................... X X 

Andrazella sp. M. Gallitelli and others . .......... X 

Astraeomorpha crassisepta Reuss ................... X X X X 

A. confusa (Winkler) .............................. X X 

A. confusa var. minor Frech . ...................... X X 

Coccophyllum acanthophorum Frech .................. X X X 

Coccophyllum sp. M. Gallitelli and others . ........ X 

Cyathocoenia idahoensis (Squires) ................. X X 

c. cf. c. juvavica (Frech) ........................ X X 

c. schafhaeutli (Winkler) ......................... X X X 

c. squiresi n. sp. . ............................... X X 

Cyathocoenia (?) sp. M. Gallitelli and others X 

Distichophyllia norica (Frech) .................... X X X X X 

D. melnikovae (M. Gallitelli) . .................... X 

Gablonzeria major (Frech) ......................... X X X 

G. profunda (Reuss) ............................... X X X X 

Guembelastraea cowichanensis (Clapp and Shimer) X 

G. vancouverensis (Clapp and Shimer) .............. X 

G. whiteavesi (Clapp and Shimer) ..................... X 

Margarastraea pulchra (M. Gallitelli) ................ X 

Margarosmi li a zieteni (Klipstein) ............... .. X X 

Opelismilja zi tteli (Frech) .......................... X X 

Pamiroseris meriani (Stoppani) .... ................ X X 

P. smi thi (Squires) ............................... X X X 

Pinacophyllum parviseptum Squires .................. X X X 

Retiophyllia caespitosa (Frech) ................... X X 

R. dawsoni (Clapp and Shimer) ..................... X X X X X 

R. delicatula (Frech) ••• •. I.e. e. I • e •• e e e e e •. e e e. e e X X 

R. fenestrata (Reuss) e • e • ••. e ••••••• I .I e. e. •. •• •. e X X 

R. norica (Frech) ............. .................... X X 

R. oppeli (Reuss) .................................. X X X 

R. suttonensis (Clapp and Shimer) ................. X X 

R. wrangelliana (Russo) ........................... X 

Retiophyllia sp. (M. Gallitelli and others) X X 

Stylina norica Frech ............................... X X 

Stylophyllopsis zi tteli Frech ....................... X X 

Stylophyllum paradoxum Frech ...................... X X 

Thamnasteriomorpha frechi (Volz) ................... X X X 

Tricycloseris sp. M. Gallitelli and others . ....... X 

SPONGIOMORPHS 

Heptastylis aquilae Smith .......................... X 

H. oregonensis Smith ................................ X 

Heptastylis sp. M. Gallitelli and others . .......... X 

Spongiomorpha gibbosa Frech •• •• e e ••. e. I ••. e • e. e. e. X X X 

s. ramosa Frech •• •. e e I I ••.•• I • e ............... e •• " ••• X X X 

s. tenuis (Smith) ................................. X X 

Stromatomorpha californi ca Smith .................. X 

Stromatomorpha sp. M. Gallitelli and others X 

Stromatomorpha sp. . ............................... X 

Total Number of Taxa 12 18 15 15 15 
28 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

Table 3.2.-Similarities between Late Triassic (Norian) coelenterate faunas from localites in northeastern Oregon and western Idaho 

[Odum's (1971) index of similarity: 2C/N1 + N2, C =number of taxa common to two localities, N1 and N2 + number of taxa in each respective sample being compared. Data calculated 

from table 3.1 using published species occurrences; 0.000 indicates no species in common; 1.00 indicates identical faunas; for each locality shown at left, the percent of species found 

also in the Alps and central Europe and of those found only in North America are indicated at the right] 

Wallowa 

Mountains Lewiston 

Wallowa Mountains ..... . 

Lewiston ..............• 

Hells Canyon . . ........• 

Vancouver Island ...... . 

Wrangell Mountains .. , .. 

1. 00 0.20 

1. 00 

also known in North America (Stanley, 1979). The 

coelenterate faunas from the different localities (table 

3.1) show a great number of Tethyan species (46-75 

percent; see table 3.2). This is especially true for the 

Wallowa Mountains where all the corals are known from 

the Alps. Interestingly, only two of the spongiomorphs 

at these localities have alpine affinities (table 3.1). The 

Hells Canyon and Wrangell Mountains localities show 

the lowest percentage of Tethyan taxa ( 4 7 percent) and 

more endemic taxa (53 percent) than any other locality. 

SYSTEMATIC PALEONTOLOGY 

Order SCLERACTINIA Bourne 1900 

Suborder ASTROCOENIINA Vaughan and Wells 1943 

Family ASTROCOENIIDAE Koby 1890 

Genus CYATHOCOENIA Duncan 1867 

Cyathocoenia cf. C. juvavica (Frech) 

Plate 3.1, figure 7 

Stephanocoeniajuvavica Smith, 1927, pl.112, figs. 7-10, 

p.132. 

Actinastaeajuvavica (Frech). Stanley, 1979, pl. 1, fig. 7. 

Remarks.-Details of the specimen fit well the 

descriptions given by both Frech and Smith. Distinctive 

features are in the septal arrangement and columnella. 

Based on the study ofMelnikova (1968), Frech's species 

must be placed in the Genus Cyathocoenia Duncan. 

Occurrences.-Wallowa Mountains (Eagle Creek); 

Lake Shasta, California; Pilot Mountains, Nevada; 

Gravina Island, Alaska; Zlambach beds, Austria. 

Repository.-Vniversity of Montana Museum of 

Paleontology, UMP 7286. 

Cyathocoenia schafbaeutli (Winkler) 

Plate 3.1, figure 11 

Prionastraea schafhaeutli Winkler, 1861, p. 488, pl. 8, 

fig.11. I 

Stylina savii Stoppani, 1858-67, p. 101-102, pl. 24, figs. 

9-12. 

lsastraea suessi Reuss, 1864, p. 165, pl. 2, fig. 4. 

Stephanocaenia schafhaeutli (Winkler). Frech, 

1890, p. 37, text and fig. 

Percent 

Percent North 

Hells Vancouver Wrangell Alpine American 

Canyon Island Mountains Species Species 

0.00 0.15 0. 15 75 25 

0. 24 0.67 0.24 61 39 

1. 00 0.20 0.33 47 53 

1. 00 0.13 53 47 

1. 00 47 53 

Cyathocoenia schafhaeutli (Winkler). Melnikova, 1968, 

pl. 3, fig. 1-4. 

Remarks.-The specimen from Lewiston fits well 

the description and illustrations in Winkler and Frech 

as well as that by Smith. 

Squires (1956, text figs. 1-3) illustrated and 

described Astrocoenia schafhaeutli (Winkler) from 

Lewiston. However, as Montanaro Gallitelli and others 

(1979) pointed out, those specimens are not similar to 

Winkler's type. Melnikova (1968) put Stephanocoenia 

juvavica Frech in synonomy with Cyathocoenia 

schafhaeutli (Winkler), with which I do not agree. Features presented by Frech, such as number and regular 

arrangement of the septa, support considering C. 

schafhaeutli as a distinct species,it must be so regarded 

until detailed study of the type material can be made. 

Occurrences.-Lewiston, Idaho; Vancouver Island 

(Lake Cowichan); Zlambach beds, Austria; southeastern Pamirs, USSR; southern Alps, Italy; Apennines. 

Repository.-V.S. National Museum of Natural 

History, USNM 252707. 

Cyathocoenia squiresi n. sp. 

Plate 3. 1, figure 10 

Astrocoenia schafhaeutli (Winkler), Squires, 1956, fig. 

1-3. 

Actinastraea schafhaeutli (Winkler), Stanley, 1979, pl. 

1, fig. 2. 

Actinastraea ohmanni (Frech), Stanley," 1979 (not 

Frech). pl. 1, figs. 3-5. 

Description.-Incrusting, nodular, or slender 

branching colonies. Broad, open corallites 1.0-2.0 mm 

diameter with a sunken calical pit 1 mm diameter. Septa 

number 23-27 and are generally straight and nonconfluent with those of adjacent corallites. Some septa 

curve about strongly where they intersect septa of adjacent corallites. The calical pit contains a slender, 

stelliform columnella, with 4-8 palli arranged symmetrically about it. 

Remarks.-This species was well illustrated by 

Squires (1956, figs.1-3) but as Montanaro Gallitelli and 

others (1979) pointed out, the size of the corallites and 
3. LATE TRIASSIC COELENTERATE FAUNAS OF WESTERN IDAHO AND NORTHEASTERN OREGON 29 

other characteristics set these specimens apart from 

Cyathocoenia schafhaeutli (Winkler) to which Squires 

assigned his material. 

Occurrences.-Lewiston, Idaho; Vancouver Island 

(Lake Cowichan). 

Repository.-University of Montana Museum of 

Paleontology, UPM 7287. 

Family THAMNASTERIIDAE Vaughn and Wells 1943 

Astraeomorpha crassisepta Reuss, 1854 

Plate 3.1, figure 12 

Astraeomorpha crassisepta Reuss, 1854, p. 127, pl. 16, 

figs. 5-7; Pratz, 1882, p.103, pl.14, figs.13, 14; Haas, 

1909, p. 153. 

Thamnastrea borealis Smith, 1927, p. 131, pl. 115, figs. 

6-10. 

Astraeomorpha bulbosa Wilkens, 1937, p. 184, pl. 9, figs. 

3-4. 

Thamnasteria (Astraeomorpha) cuneata Squires, 1956, 

p.15, figs.11-13. 

Astraeomorpha crassisepta Reuss, Melnikova, 1971, p. 

162, pl. 1, fig. 1-2. 

Astraeomorpha crassisepta Reuss, Roniewicz, 1974, p. 

113, pl. 9, fig. 4-5. 

Astraeomorpha crassisepta Reuss, Cuif, 1975, p. 117, pl. 

17, fig.1-7. 

Astraeomorpha crassisepta Reuss, Montanaro Gallitelli 

and others, 1979, p. 142, pl. 2, fig. 5-6. 

Thamnasteria smithi Squires, Stanley, 1979 (not 

Squires, pl. 1, fig. 10). 

Remarks.-Squires (1956) described Thamnasteria 

(Astraeomorpha) cuneata as a new species from 

Lewiston, Idaho, and placed Thamnastrea borealis 

Smith in synonomy. However, I concur with Montanaro 

Gallitelli and others (1979) that both Squires' type and 

Smith's holotype are best referred to as Astraeomorpha 

crassisepta Reuss. This reduces by two the number of 

endemic North American species known. 

Occurrences.-Lewiston, Idaho, Hells Canyon; 

Gravina Island, Alaska; southeastern Pamirs, USSR; 

Lombardi, Italy; Zlambach beds, Austria; Kothalp, Austria; Tatra Mts., Poland. 

Repository.-University of Kansas Museum of 

Invertebrate Paleontology, KUMIP 113705. 

Suborder FAVIINA Vaughan and Wells 1943 

Superfamily STYLOPHYLLICAE Volz 1896 

Family STYLOPHYLLIDAE Volz 1896 

Genus STYLOPHYLLUM Reuss 1854 

Stylophyllum paradoxum Frech 1890 

Plate 3.1, figures 1-3 

Stylophyllum paradoxum Frech, 1890, p. 45, pl. 14, figs. 

1-24, pl. 15, fig. 12; Squires, 1956, p. 17, figs. 14-17; 

Cuif, 1972, p. 227, fig. 9; Cuif, 1977, pl.l, figs.1-3, pl. 

2, figs. 1-2. 

Remarks.-This species was well described by 

Squires (1956), who correctly related it to Frech's species 

from the Zlambach beds of Austria. It is a very common 

species at the Lewiston locality. 

Occurrences.-Lewiston, Idaho; Zlambach beds, 

Austria. 

Repository.-University of Montana Museum of 

Paleontology UPM 7288, 7289, 7290. 

Genus COCCOPHYLLUM Reuss 1865 

Coccophyllum acanthophorum Frech 1890 

Plate 3.1, figures 8, 9 

Coccophyllum acanthophorum Frech, 1890, p. 89, pl. 29, 

figs. 4-11; Squires, 1956, figs. 19-21; Stanley, 1979, 

pl. 2, figs 3, 5-7. 

Remarks.-This species from Frech was well 

described by Squires (1956) and has also been recognized from Vancouver Island by Stanley (1979). 

Although microstructural features are missing because 

of the silicification, other surface features are adequate 

enough to relate the North American species to the 

Alpine species of Frech (1890). 

Coccophyllum (?) sp. Montanaro Gallitelli and others (1979) is different, especially in having very large 

corallites, and thus cannot be related to C. 

acanthophorum Frech. 

Occurrences.-Lewiston, Idaho (Mission Creek); 

Vancouver Island (Lake Cowichan); Zlambach beds, 

Austria. 

Repository.-U.S. National Museum, USNM 

252710; University of Montana, Museum of Paleontology, UMP 7291. 

Superfamily FAVIICAE Gregory 1900 

Family DISTICHOPHYLLIIDAE Cuif 1977 

Distichophyllia norica (Frech) 

Plate 3.1, figures 4-6 

Montlivaltia norica Frech, 1890, p. 34, pl. 3, fig. 9a,b, pl. 

10, figs.1-5, pl.13, figs.1-7, pl.18, figs.17, 17a; 

Smith, 1927 (asMontlivaultia), p.126, pl. 111, fig. 6; 

Squires, 1956, p. 21, figs. 32-4 7. 

Stylophyllopsis mojsvari Frech. Smith, 1927, p. 127, pl. 

118; fig.10. 

Montlivaltia sp. cf. M. norica Frech. Kanmera, 1964, p. 

120, pl. 12, figs. 6-10. 

Distichophyllia no rica (Frech). Cuif, 197 4a, p. 304, figs. 

2-6; 1977, pl. 3, fig. 4-8. 
30 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

Montlivaltia norica Frech. Stanley, 1979, pl. 2, figs. 

8-10. 

Disticophyllia cf. norica (Frech). Montanaro Gallitelli 

and others, 1979, p. 149, pl. 4, fig. 9a,b. 

Remarks.-Cuif (1972a) re-evaluated the microstructural details of Frech's species as well as other 

corals assigned to Montlivaltia and concluded that this 

genus cannot be present in the Triassic. He therefore 

proposed a new family, Distichophylliidae, establishing 

Montlivaltia norica Frech as the type species. The specimens that Squires assigned to Montlivaltia no rica most 

certainly belong to this species, although the microstructure is not present. 

Occurrences. Wallowa Mountains, Oregon (Eagle 

Creek); Lewiston, Idaho; Pilot Mountains, Nevada; Vancouver Island (Lake Cowichan), Canada; Wrangell 

Mountains, Alaska; Zlambach beds, Austria. 

Repository.-University of Montana, Museum of 

Paleontology, UMP 7292, 7293. 

Family TROPIPHYLLIDAE Beauvais 1980 

Genus GABLONZERIA Cuif 1976 

Gablonzeria profunda (Reuss) 1854 

Plate 3.1, figures 13, 14 

lsastraea profunda Reuss, 1864, p. 116, pl. 9, figs. 5-6; 

Frech, 1890, p. 21, pl. 5, figs. 1-3a; Smith, 1927, p. 

128, pl. 105, fig. 8, pl. 112, figs. 5-6, pl. 114, figs. 1-3. 

Elysastraea profunda (Reuss) Stanley, 1979, pl. 3, figs. 

6, 8. 

lsastraea profunda Reuss. Cuif, 1976, p. 116, pl. 11, figs. 

1-8. 

Remarks.-Squires (1956) placed his specimens in 

the Genus Elysastraea Laube, describing them as E. 

profunda. These were previously regarded as Isastraea 

in the older publications. Detailed microstructural 

studies on the Alpine types were conducted by Cuif 

(1976, p. 118), who proposed the new genus Gablonzeria 

for some species assigned to lsastraea, such as /. profunda and I. norica. Although diagnostic microstructural features ·have not been found in the North 

American specimens, they are in all likelihood assignable to Cuifs Gablonzeria ratherthanElysastraea Laube. 

Occurrences.-Lewiston, Idaho; Pilot Mountains, 

Nevada; Lake Shasta, California (Brock Mt.); southern 

Wallowa Mountains, Oregon (Eagle Creek); Vancouver 

Island (Lake Cowichan); Gravina Island, Alaska; Lake 

Iliamna, Alaska; Zlambach beds, Austria; Japan. 

Repository.-University of Montana Museum of 

Paleontology UMP 7294, 7295. 

Class HYDROZOA Owen 1843 

Order SPONGIOMORPHIDA Alloiteau 1952 

Family SPONGIOMORPHIDAE Frech 1890 

Genus SPONGIOMORPHA Frech 1890 

Spongiomorpha tenuis Smith 1927 

Plate 3.1, figure 15 

Spongiomorpha (Heptastylopsis) tenuis Smith, 1927, p. 

133, pl. 118, fig. 3. 

Spongiomorpha tenuis Stanley, 1979, pl. 6, figs. 1-2. 

Remarks. -Smith described Spongiomorpha (Heptastylopsis) tenuis from the Lake Shasta area. The subgenus Heptastylopsis cannot be maintained, as pointed 

out by Fhigel and Sy (1959). 

Occurrences.-Lewiston, Idaho; southern Wallowa 

Mountains (Eagle Creek); Lake Shasta, California 

(Squaw Creek). 

Repository.-Vniversity of Kansas Museum of 

Invertebrate Paleontology, KUMIP 113662. 

Spongiomorpha ramosa Frech 1890 

Plate 3.1, figure 16 

Spongiomorpha (Heptastylopsis) ramosa Frech, 1890, p. 

76, figs. a-c; Smith, 1927, p. 133, pl. 120, figs. 4-5, pl. 

121,figs.10-13. 

Spongiomorpha ramosa Frech. Haas, 1909, p. 155, pl. 5, 

fig. 16a,b, pl. 6, fig. 1; Renz, 1912, p. 77; Kolosvary, 

1966, p. 179; Montanaro Gallitelli and others 1979 

pl. 6, fig. 6a,b; Stanley, 1979, pl. 4, fig. 11, pl. 6: fig. 4: 

Remarks.-This species was described by Smith 

(1927) and recognized by Montanaro Gallitelli and others (1977). Characterized by a branching coenosteum 

and strong trabecular elements, it is a widespread and 

common species in the Norian. 

Occurrences.-Lewiston, Idaho; Gravina Island, 

Alaska; Iliamna Lake, Alaska; Wrangell Mountains, 

Alaska; Zlambach beds, Austria, Greece; Czechoslovakia. 

Repository.-University of Montana Museum of 

Paleontology, UMP 7296. 

Genus STROMATOMORPHA Frech 1890 

Stromatomorpha sp. 

Plate 3.1, figure 17 

Remarks.-Because of the surface structure, composed of simple vertical elements, and the lack of any 

trabecular elements organized into radial patterns, this 

specimen is referrable to Stromatomorpha Frech. It 

differs in surface organization from Stromatomorpha 

sp. Montanaro Gallitelli and others (1979, pl. 6, fig. 7a,b). 

Internal details necessary for species assignments are 

not available. 

Occurrence.-Lewiston, Idaho (Mission Creek). 

Repository.-University of Montana Museum of 

Paleontology, UMP 7297. 
3. LATE TRIASSIC COELENTERATE FAUNAS OF WESTERN IDAHO AND NORTHEASTERN OREGON 31 

AGE OF CORAL DEPOSITS 

There are still uncertainties, as mentioned above, 

about the age of some ofthe coral faunas. Occurrences of 

characteristic ammonites or bivalves stratigraphically 

close to the coralline beds help establish Norian ages. 

Presence of the ammonoid, Trophiceltites cf. T. columbianus indicates that the coral fauna of the Wrangell 

Mountains belong to the lower Norian Kerri Zone and 

faunal similarities suggest the same for the Hells Canyon locality (Silberling and Tozer, 1968). Mono tis species 

referenced by Smith (1927) from the Eagle Creek 

locality also indicate an early Norian age, but diagnostic 

ammonoids were not mentioned. The Lewiston locality 

is clearly Late Triassic in age but no stage-diagnostic 

fossils are present. On the basis of the brachiopod 

Spondylospira, however, Cooper (1942) suggested aN orian age, as was also concluded by Squires (1956). The 

rich gastropod fauna of this locality suggested a NorianRhaetian age (Haas, 1953), but re-evaluation of the coral 

faunas by Stanley (1979) indicated a late Norian age for 

the Lewiston outcrop. 

The rare Late Triassic ammonites reported from 

the coral locality at Lake Cowichan, Vancouver Island 

(Silberling and Tozer, 1968) allow assignment of that 

interval to the uppermost Norian Crickmayi Zone 

(Stanley, 1979). The coral locality in the Chitistone 

Limestone (U.S.G.S. locality M1708) in the Wrangell 

Mountains, Alaska, contains Halobia brooksi (Silberling and Tozer, 1968), which indicates an age also 

roughly equivalent to the lower Norian Kerri Zone. The 

indicated ages of the coelenterate faunas at the various 

localities are presented in figure 3.2. 

Three of the localities (Hells Canyon, Wallowa 

Mountains, and Wrangell Mountains) thus seem clearly 

to be early Norian in age. The faunas from these three 

localities are considered equivalent in age and represent the lower Norian Kerri Zone (fig. 3.2). The Vancouver Island localities on Lake Cowichan are well 

established as latest Norian. The Lewiston locality is 

more likely Norian but lacks diagnostic fossils for precise chronostratigraphic assignment; however, the corals suggest correlation with the Vancouver Island 

locality. The Lewiston coral fauna is, therefore, most 

probably late Norian in age. Comparison of the faunas 

from Vancouver Island and the other localities shows 

significant similarity only between the Lewiston and 

Vancouver Island localities, where a relatively high 

value of0.67 was found (table 3.2). This unusually high 

similarity value is evidence that the Lewiston coral 

faunas are late Norian and thus approximately timeequivalent to the Vancouver Island fauna. In addition, 

these two localities share species known nowhere else 

(Cyathocoenia idahoensis, C. squiresi n. sp. pl. 1, fig. 10; 

Retiophyllia suttonensis ). They also share the occurZone 

C horistoceras 

crickmayi 

t> ~ Coch/oceras 

2: '§ amoenom ~z 

Gnamohalorites 

cordilleranus 

Himavatites 

columbianus 

Drepanites 

rutheifordi 

Juvavites 

mag nus 

Malayites 

dawsoni 

M o jsisovicsites 

kerri 

K /amathites 

macrolobatus 

Tropites 

welleri 

Tropites 

dilleri 

• • 

• • • 

FIGURE 3.2.-Ages of the Late Triassic coelenterate faunas from western North American localities, showing recognized biostratigraphic 

zones based mostly on ammonoids and monotid bivalves (Tozer, 

1967, 1980). The basis for the age determinations at each locality is 

discussed in the text. 

renee of the coral Coccophyllum acanthophorum (pl. 1, 

figs. 8, 9), known also from Lake Iliamna, Alaska, and 

from the Norian of central Europe (Frech, 1890). 

DISPLACED TERRANES AND PROBLEMS IN 

PALEOGEOGRAPHY 

Jones and others (1977) defined Wrangellia, which 

is now one of the best known of the many displaced 

terranes recognized in the northwestern United States, 

Canada, and Alaska. The Wrangellia stratigraphic succession consists of a thick sequence of Permian and 

Middle and Upper Triassic basalts and volcaniclastic 

rocks overlain by shallow-water platform carbonate 
32 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

rocks of Karnian and Norian age. Jones and others 

(1977) cited general similarities in the paleomagnetic, 

volcanic, and stratigraphic attributes of widespread 

localities from the Wrangell Mountains of Alaska to 

Vancouver Island in British Columbia, with possible 

extensions in Hells Canyon and the Wallowa Mountains. Thus, all of the coral faunas discussed in this 

paper are from areas recognized or suspected to be part 

of the Wrangellia terrane. According to current ideas, 

this terrane was accreted to the craton ofN orth America 

sometime in the late Mesozoic and was later tectonically 

dislocated. Remnants are believed to be distributed 

throughout an extensive part of western North America, from Alaska to Idaho and Oregon. 

Accumulating paleomagnetic evidence, coupled 

with the general characteristics of the rich faunas of 

shallow-water benthic invertebrates, indicates that all 

of Wrangellia originated at low latitudes, generally 

about 16°, north or south of the Triassic equator (Jones 

and others, 1982). Triassic rocks of the Wallowa and 

Snake River region are part of the volcanic arc terrane of 

Brooks and Vallier (1978). Silberling and others (1984) 

have recently termed these rocks the Wallowa terrane, 

and that terminology will be used in the following discussion. Paleomagnetic studies by Hillhouse and others 

(1982) demonstrated that Triassic rocks of the Wallowa 

terrane originated at approximately 18° from the paleoequator and had undergone significant rotation. Their 

findings tended to support the idea of Jones and others 

(1977) that these rocks were part of the extensive 

Wrangellia terrane. 

The importance of the faunas in assessing terrane 

movements was emphasized by Tozer (1982), who relied 

mostly on open-ocean pelagic or deepwater taxa and 

treated the shelly benthos as a single association of lowlatitude origin. His paleogeographic reconstruction 

(Tozer, 1982; fig. 2) places Wrangellia in a warm-water 

setting south of the Triassic equator, far from the craton 

of Pangaea, and east of the postulated Triassic spreading center, ancestral to the East Pacific Rise. Similarities of benthic invertebrate faunas from Upper 

Triassic carbonate rocks of Wrangellia and of the Wallowa terrane were noted by Jones and others (1977), who 

suggested that the latter was a southern extension of 

Wrangellia. 

Newton (1983) assessed these apparent paleogeographic relationships in a more detailed approach 

based on analysis of numerous bivalve genera. She 

placed Wrangellia in an east-west orientation between 

15° and 18° latitude. This seems totally in agreement 

with the paleomagnetic data. At the generic level, Newton found significant similarity between the Wrangell 

Mountains and Hells Canyon, also believed to belong to 

the Wrangellia terrane, and less similarity between 

these and faunas from Puale Bay and Keku Strait, 

Alaska, thought to belong to terranes different from 

Wrangellia. Because of the lack of detailed systematic 

work on the molluscs, a more refined analysis using 

species was not possible. 

The similarity coefficients presented in table 3.2 

are based on an analysis of 49 coelenterate species. 

Compared to genera, these species should be more sensitive indicators of biogeographic variations. It is clear 

from table 3.1 that if genera only are used the results 

will be quite different, because many genera have 

numerous species and are widely distributed. 

The Hells Canyon fauna at the U.S.G.S. locality 

M2672 has been recollected by Michael Whalen (University of Montana, M.S. thesis, 1985). The results are 

expected to be published later in a systematic study now 

underway. Preliminary identifications of11 coelenterate 

taxa from the fossil bed at the Hells Canyon locality 

show a number of discrepancies with the data of Montanaro Gallitelli and others (1979). The major discrepancy is in the preponderance of spongiomorphs which 

appear to make up a major component of the Hells 

Canyon fauna but were reported by Montanaro Gallitelli and others (1979) only from the Wrangell Mountains. Further results show that some taxa reported 

only from the Wrangell Mountains occur instead in 

Hells Canyon. The possibility therefore exists that earlier collections from these two localities were mixed up 

by these authors or perhaps their material was not 

representative of the whole coelenterate fauna. 

Coefficients of similarity may be recalculated on the 

basis of new species collected from Hells Canyon, but 

they still show low similarity with other localities, 

especially the Wallowa Mountains. The new data, not 

yet published, yield a similarity of 0.31 with the 

Wrangell Mountains, a value not so different from that 

originally calculated (table 3.2). Before unequivocal 

comparisons between these two are possible, new collections from the Wrangell Mountains must be studied. 

Paleomagnetic data clearly establish the segments 

of Wrangellia present in Alaska and the Canadian 

northwest as having been formed at low latitudes, an 

inference substantiated by the general character of the 

invertebrate faunas. The importance of detailed systematic studies is readily apparent here because not 

until paleontological studies of the benthic faunas are 

complete can accurate comparisons of them be made 

and relative placement ofthe original longitudinal positions of various terranes be inferred. It is still not clear 

whether the isolated Wallowa terrane segment in northeastern Oregon and Idaho actually belongs to the 

Wrangellia terrane. More detailed paleontologic studies 

of the benthic elements of the faunas are necessary to 

clarify the paleogeography of Wrangellia, as defined by 
3. LATE TRIASSIC COELENTERATE FAUNAS OF WESTERN IDAHO AND NORTHEASTERN OREGON 33 

Jones and others (1977), and its relationship to other 

volcanic terranes such as those of Oregon and Idaho. 

CONCLUSIONS 

The Late Triassic coelenterate faunas of Oregon, 

Idaho, Vancouver Island, and the Wrangell Mountains 

have been differentiated into early and late Norian 

assemblages. This work shows that the corals can, in the 

absence of other more diagnostic fossils, be useful in 

biostratigraphic studies. While some commonly occurring corals such as Distichophyllia norica (pl. 3.1, figs. 

4-6), Retiophyllia dawsoni, and Gablonzeria profunda 

(pl. 3.1, figs. 13, 14) seem to be little differentiated 

through the Triassic, whereas other taxa such as Coccophyllum acanthophorum, Cyathocoenia idahoenis, C. 

squiresi n. sp., and Retiophyllia suttonensis are distinct 

from taxa in older rocks and assist in recognizing the 

latest Triassic (Crickmayi Zone). The spongiomorph 

taxa do not appear to be as useful as the corals in 

biostratigraphic studies. 

The high degree of similarity between Alpine 

faunas of the former western Tethys region and faunas of 

Oregon and Idaho supports the idea that the Panthalassa Sea connecting with the Tethys and surrounding Pangaea contained numerous seamounts and 

islands of volcanic and continental origins (Tozer, 1982). 

Coral larvae could use these islands as stepping stones 

for their dispersal across this sea. Various distances 

between islands and the presence or absence of intervening deep sea between continents, islands, or island 

clusters would contribute to substantial differences in 

the overall composition of coral faunas. 

All the localities studied in this paper are suspected 

to be part of Wrangellia (Jones and others, 1977). With 

the refinement of the age relationships now possible (fig. 

3.2), one would expect that contemporaneous coelenterate faunas of Wrangellia would show high levels of 

similarity to each other and be different from faunas of 

other unrelated terranes. This is, however, not the case 

with the coral faunas. With the exception of the two late 

Norian faunas of Vancouver Island and Lewiston, the 

faunas do not have much similarity with one another 

(table 3.2). For example, comparisons of Wallowa coral 

faunas with those of the Wrangell Mountains show 

extremely low similarity values. No similarity at all 

exists between the Wallowa fauna and that of Hells 

Canyon, only a short distance away (table 3.2), although 

both are of the same age according to Montanaro Gallitelli and others (1979). Previous similarity data of 

Stanley (1979) showed that early Norian corals of the 

Wallowa Mountains bear much higher levels of similarity to other, supposedly unrelated, terranes (fig. 3.1), 

such as Gravina Island, which belongs to the Alexander 

terrane (Berg, 1973), and the Luning Formation in the 

Pilot Mountains, Nevada. The latter may be related to 

the Sonomia terrane of Speed (1979). Coelenterate 

faunas from these rocks show significantly higher levels 

of similarity with the Wallowa terrane than with the 

"type locality" of Wrangellia in the Wrangell Mountains. 

Dissimilarities between the Wallowa locality and the 

nearby Lewiston site can be explained because these 

faunas are of different ages, separated by at least six 

biostratigraphic zones (fig. 3.2). Considerable evolution 

is thus represented among the coral faunas, which by 

latest Triassic time were beginning to increase their 

rates of diversification (Stanley, 1981). 

The problem of separating local environmental 

influences on the composition of the coral faunas from 

real paleogeographic differences can be partly overcome 

by recognizing the broad ecologic tolerances that 

characterized many of the coral taxa. As previously 

pointed out, Triassic corals appear not to have been so 

closely controlled by environment as their more recent 

descendents. There are definite problems in relating the 

Wallowa terrane to Wrangellia. Admittedly, the two 

localities bear much stratigraphic similarity (Silberling, 1983). In spite of these superficial similarities, 

however, Sarewitz (1983) concluded, on the basis of differences in the geochemistry of the volcanic rocks and 

contrasting geologic histories, that these two terranes 

are quite distinct from one another. The data from 

coelenterate faunas generally tend to corroborate this 

conclusion, but high similarities link late Norian faunas 

of Lewiston and Vancouver Island, which may have been 

in closer proximity than the early Norian faunas. Fifteen coral taxa listed from the Wrangell Mountains 

(table 3.1) were described by Montanaro Gallitelli and 

others (1979). Eight of these are known only from North 

America, and four others (a species of Actinastraea, 

Distichophyllia melnikovae, Margarastraea pulchra, 

and Retiophyllia wrangelliana) are found only in the 

Wrangell Mountains (table 3.1). 

Current workers envision Wrangellia in early Norian time as a subsiding volcanic-island terrane on which 

a thick series of carbonate sediments was deposited 

within platforms or shoals. Paleon1agnetic and paleontological evidence shows that Wrangellia was situated in 

a low-latitude, warm-water setting, most likely in the 

southern hemisphere. The coral fauna of such a setting, 

like those demonstrated for present-day groups of 

islands in the Carribean or Indo-Pacific regions (Wells, 

1954; Newell, 9171; "Rosen, 1975), would be expected to 

display a great deal of commonality in genera and even 

in species. The degree of commonality is especially 

strong when such an island group is oriented in an eastwest direction, because such orientation promotes uniform conditions for marine life. However, significant 
34 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

differences in the coral faunas suggest that during the 

Late Triassic the Wallowa terrane was separated from 

Wrangellia by a body of water deep or extensive enough 

to substantially reduce the exchange of coral larvae. 

After volcanic activity ceased, distant terranes could 

have developed similar stratigraphic sequences by similar responses to sea level changes induced by the mechanisms of sea- floor spreading and the accompanying 

subsidence normally affecting volcanic atolls and seamounts. 

Although preliminary, the paleontological data presented here provide a stimulus to explore further the 

paleogeographic issues. They necessitate rethinking on 

ideas about the inclusion of northeastern Oregon and 

adjacent Idaho in the Wrang~llia terrane and even question the coherence of a single Wallowa terrane. Continued structural, petrographic, and stratigraphic 

studies should be made, in concert with detailed pal eontological studies. Independent studies of the rich 

brachiopod, mollusc, echinoid, and crinoid faunas would 

allow cross-checks of paleogeographic conclusions. 

Some of the Late Triassic benthic faunas may have been 

craton-bound or at least postaccretional and thus would 

be indigenous to North America. Faunas of this type 

include those of the Sonomia (Speed, 1979) in Nevada, 

the Pardonet Formation of northeast British Columbia 

(Tozer, 1967), and possibly the Alexander terrane (Hillhouse and Gramme, 1980). Future studies must 

ultimately rely on these autochthonous, craton-bound 

fossils for the necessary paleobiogeographic controls. 

Careful and detailed study of such endemic benthic 

fossils of North and South America and comparisons 

with counterparts from various exotic terranes should 

eventually clarify details of the Triassic geography with 

a precision not currently available from the open-water 

and deeper water molluscan faunas. 

REFERENCES CITED 

Armstrong, A.K., Mackevett, E.M., Jr., and Silberling, N.J., 1969, The 

Chitistone and Nizina Limestones of part of the southern 

Wrangell Mountains, Alaska-a preliminary report stressing 

carbonate petrography and depositional environments: U.S. 

Geological Survey Professional Paper 650-D, p. D49-D62. 

Berg, H. C., 1973, Geology of Gravina Island, Alaska: U.S. Geological 

Survey Bulletin 1373, 41 p. 

Brooks, H.C., and Vallier, T.L., 1978, Mesozoic rocks and tectonic 

evolution of eastern Oregon and western Idaho, in Howell, D.G. , 

and McDougall, K.A., Mesozoic Paleogeography of the Western 

United States: Los Angeles, Calif., Pacific Section, Society of 

Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 2, p. 133-145. 

Cooper, G.A., 1942, New genera of North American brachiopods: Journal of the Washington Academy of Science, v. 32, p. 288-235. 

Cuif, J.P., 1965, Sur les rapports des generes des madreporaires, 

Montlivaltia Lam. et Thecosmilia M. Edw. et H. et leur presence 

au Trias [On the report of the genera of the corals Montlivaltia 

and Thecosmilia and their presence in the Triassic]: Bulletin de 

la Societe Geologique de France, serie 7, v. 7, p. 530-536. 

--1972, Recherches sur les madreporaires du Trias, I. Famille des 

Stylophyllidae [Research on the corals of the Triassic, I. Family 

stylophyllidae]: Bulletin du Museum National d'Historie 

Na.turelle, serie 3, no 97, Sciences de la Terre, v. 17, p. 211-291. 

---197 4a, Recherches sur les madreporaires du Trias, II. 

Astraeoida, revision des Genres Montlivaltia et Thecosmilia. 

Etude de quelques types structuraux du Trias de Turquie 

[Research on the corals of the Triassic, II. Astraeoida, revision of 

the genera Montlivaltia and Thecosmilia. Study of several types 

of structure from the Triassic of Turkey]: Bulletin du Museum 

National d'Historie Naturelle, serie 3, no. 275, Sciences de la 

Terre, v. 40, p. 293-400. 

--197 4b, Role des sclerosponges dans la faune recifale du Trias 

des dolomites (Italie du Nord) [Role of the sclerosponges in a reef 

fauna from the Triassic of the Dolomites]: Geobios, v. 7, p. 

139-154. 

--1975, Recherches sur les madreporaires du Trias, III. Etude des 

structures pennulaires chez les madreporaires triasique 

[Research on the corals of the Triassic, III. Studies of pennular 

structures in the Triassic corals]: Bulletin du Museum National 

d'Histoire Naturelle, serie 3, no. 310, Sciences de la Terre, v. 44, p. 

45-127. 

--1976, Recherches sur les madreporaires du Trias, IV Formes 

cerio-meandoides et thamnasteroiides du Trias des Alpes et du 

Taurus sudanatolien [Research on the corals of the Triassic, IV 

Forms cerio-meandroid and thamnasteroid of the Triassic of the 

Alps and Taurus, South Antolian]: Bulletin du Museum National 

d'Histoire Naturelle, serie 3, no. 381, Sciences de la Terre, v. 53, p. 

65-194. 

---1977, Arguments pour une relation phyletique entre les 

madreporaires Paleozoiques et ceux du trias [Arguments for a 

phyletic relationship between the Paleozoic corals and those of 

the Triassic]: Memoires Societe Geologique de France Nouvelle 

Serie, 54, no. 129, 54 p. 

Dacque, E., 1915, Grundlagen und methoden des palaogeographie 

[Foundations and methods of paleogeography]: Jena, Fischer, 

499 p. 

Dott, R.H., and Batten, R.L., 1976, Evolution of the Earth [2nd ed.]. 

New York, McGraw-Hill, 504 p. 

Fhigel, E., 1981, Paleoecology and facies of Upper Triassic reefs in the 

Northern Calcareous Alps, in Toomey, D.F., ed., European fossil 

reef models: Society of Economic Paleontologists and Mineralogists Special Publication no. 30, p. 291-359. 

Fltigel, E., and Sy, E., 1959, Die Hydrozoan der Trias [The hydrozoans 

of the Triassic]: Neues Jahrbuch fur Geologie und Palaontologie, 

v.109, p.1-108. 

Follo, M.J., 1985, Sedimentological investigations of a suspect terrane, 

Wallowa Mountains, Oregon: Proceedings, Pacific Division, 

American Association for the Advancement of Science, v. 4, pt. 1, 

p. 28. 

Frech, Fritz, 1890, Die korallen fauna der Trias, I. Die korallen der 

juvavischen Trias-Provinz [The coral fauna of the Triassic, I. The 

corals of the Juvavic Triassic]: Palaeontographica, v. 37, p. 1-116. 

Hass, O.H., 1909, Bericht tiber neue aufsammlungen in den Zlambach 

mergeln der Fischerwiese bei Alt-Aussee. Beitrage ztir Palaontologie in Geologie, Osterreich-Ungarns und des Orients [An 

account of new collections from the Zlambach marl of Fischerwiese near Alt-Aussee]:Mitterlungen desGeologieund Palaontologie Institut der Universitat Wien, p. 143-165. 

--1953, Mesozoic invertebrate faunas ofPeru, part 2, Late Triassic 

gastropods from central Peru: Bulletin of the American Museum 

of Natural History, v. 101, p. 7-319. 

Hillhouse, J.W., and Gromme, C.S., 1980, Paleomagnetism of the Tri-
3. LATE TRIASSIC COELENTERATE FAUNAS OF WESTERN IDAHO AND NORTHEASTERN OREGON 35 

assic Hound Island volcanics, Alexander Terrane, southeastern 

Alaska: Journal of Geophysical Research, v. 85 (B5), p. 

2594-2602. 

Hillhouse, J.W, Gromme, C.S., and Vallier, T.L., 1982, Paleomagnetism and Mesozoic tectonics of the Seven Devils Volcanic Arc in 

northeastern Oregon: Journal of Geophysical Research, v. 87 

(B5), p. 3777-3794. 

Jones, D.L., Cox, A., Coney, P., and Beck, M., 1982, The growth of 

western North America: Scientific American, v. 247, p. 70-84. 

Jones, D.L., Silberling, N.J., and Hillhouse, J.W., 1977, Wrangellia-a 

displaced terrane in northwestern North America: Canadian 

Journal of Earth Sciences, v. 14, p. 2565- 2577. 

Kolosvary, G.,1966, Ober Triaskorallenfauna Ungarns [Upper Triassic 

coral fauna of Hungary]: Acta Biologica, v. 12, p. 125-137. 

Koppen, W , and Wegener, A., 1924, Die klimate der geologischen 

vorzeit: Berlin, Gebruder Borntraeger, 255 p. 

Melnikova, G.K., 1967, New species of Triassic Scleractinia from the 

Pamirs: Paleontological Journal, v. 1, no. 1, p. 18-26. 

---1968, The genus Cyathocoenia (Hexacoralla): Paleontological 

Journal, v. 2, no. 1, p. 9-15. 

---1971, New data on the morphology, microstructure and systematics of the Late Triassic Thamnasteroidea: Paleontological 

Journal, v. 5, no. 2, p. 156-169. 

---1972, Revision of some Late Triassic and Early Jurassic Stylophylliidae (Scleractinia): Paleontological Journal, v. 6, no. 2, p. 

191-200. 

---1975, Pozdnetriasovie skleraktinii yugo-vostochnogo Pamira 

[Upper Triassic scleractinians from the Pamirs]: Akad. Nauk 

Tadschikskoi SSR Institute of Geology, 234 p. 

Montanaro Gallitelli, E., Russo, A., and Ferrari, P., 1979, Upper Triassic coelenterates of western North America: Estratto dal 

Bollettino della Societa Paleontologica Italiana, v. 18, no. 1, p. 

133-156. 

Newell, N.D. , 1971, An outline history of tropical organic reefs: American Museum Novitates, no. 2465, p. 1-37. 

Newton, Cathryn R., 1983, Paleozoogeographic affinities of Norian 

bivalves from the Wrangellian, Peninsular, and Alexander Terranes, western North America, in Stevens, C.H., ed., PreJurassic rocks in western North American suspect terranes: 

Pacific Section, Society of Economic Paleontologists and Mineralogists, p. 37-48. 

Nolf, B.O., 1966, Structure and stratigraphy of part of the northern 

Wallowa Mountains, Oregon: Princeton University, Princeton, 

New Jersey, Ph.D. dissertation, 135 p. 

Odum, E.P., 1971, Fundamentals of ecology [3rd ed.]. Philadelphia, 

W.B. Saunders and Company, 574 p. 

Opdyke, N.D. , 1962, Palaeoclimatology and continental drift, in Runcorn, S.K., ed., Continental drift: New York and London, Academic Press, p. 41-65. 

Pratz, C., 1882, Uber verwandschaftlichen Beziehunger einiger 

Korallengattungen mit hauptsachlicher Berticksichtigung ihrer 

Septal-Struktur [On related connections uniting corraline types 

with principal consideration of its septum structure]: Palaeontographica, Stuttgart, v. 29, p. 81-122. 

Renz, C., 1912, Die Trias in ostlichen Mittelgriechenland [The Triassic 

in eastern middle Greece]: Centrablatt Mineralogie, Geologie 

und Palaontologie, Jahrgang, Stuttgart, p. 67-85. 

Reuss, A. E., 1854, Beitrage ztir characteristik der Kreideschichten in 

der Ostalpen besonders im Gesaulthale und am Wolfgangsee 

[Contribution on the characteristics of the Cretaceous Shale in 

the eastern Alps especially in Gesanthale and near Wolfgang 

lake): Akademie De Wissenschaften, Mathematisch-Naturwissenschaft lichen, Klasse Denkschrift, v. 7, p. 67-85. 

---1864, Uber einige Anthozoen der Kossener Schichten und der 

alpinen trias [On uniting the anthozoan of the Kossener beds 

and the alpine Triassic]: Sitzungsberichte der Akademie 

Wissenschaften, Wien, v. 50, p. 153-164. 

Roniewicz, E.W.A., 1974, Rhaet'ian corals of the Tatra Mountains: Acta 

Geologica Polonica, v. 24, p. 97-116. 

Rosen, B.R., 1975, The distribution of reef corals: Report ofthe Underwater Association, v. 1 (NS), p.1-16. 

Ross, C.P., 1938, The geology of part of the Wallowa Mountains, 

Oregon: Oregon Dept. of Geology and Mineral Industries Bulletin, v. 3, p. 1-74. 

Sarewitz, Daniel, 1983, Seven Devils terrane: Is it really a piece of 

Wrangellia: Geology, v. 11, p. 634-637. 

Schwarzbach, Martin, 1974, Das klima der vorzeit [The climate of the 

past], 3rd ed.: Stuttgart, Ferd. Enke, 380 p. 

Silberling, N.J., Jones, D.L., Blake, M.C., and Howell, D. G., 1984, 

Lithotectonic terrane map of the western conterminous United 

States, in Siberling, N.J., and Jones, D.L., eds., Lithotectonic 

terrane maps of the North American Cordillera: U.S. Geological 

Survey Open-File Report 84-523. 

Silberling, N.J., and Tozer, E.T., 1968, Biostratigraphic classification of 

the marine Triassic in North America: Geological Society of 

America Special Papers 110,63 p. 

---1983, Stratigraphic comparison of the Wallowa and Huntington 

Terranes, northeast Oregon [abs.]: Geological Society of America 

Abstracts with Programs, Rocky Mountain and Cordilleran Sections, 36th Annual Meeting, Salt Lake City, Utah, 1983, p. 372. 

Smith, J.P., 1912, The occurrence of coral reefs in the Triassic of North 

America: American Journal of Science, v. 33, p. 92-96. 

---1927, Upper Triassic marine invertebrate faunas of North 

America: U.S. Geological Survey Professional Paper 141, 262 p. 

Speed, R. C., 1979, Collided Paleozoic microplate in the Western United 

States: Journal of Geology, v. 87, p. 279-292. 

Squires, D.F., 1956, A new Triassic coral fauna from Idaho: American 

Museum Novitates, no. 1797, p.1-21. 

Stanley, G.D., Jr., 1979, Paleoecology, structure, and distribution of 

Triassic coral buildups in western North America: University of 

Kansas Paleontological Contribution, v. 65, p. 1-68. 

---1980, Triassic carbonate buildups of western North America; 

comparisons with the alpine Triassic of Europe: Rivista Italiana 

di Paleontologia e Stratigrafia, v. 85, p. 877-894. 

---1981, Early history of scleractinian corals and its geological 

consequences: Geology, v. 9, p. 507-511. 

---1982, Triassic carbonate development and reefbuilding in western North America: Geologische Rundschau, v. 71, p.1057-1075. 

Stanley, G.D., Jr., and Senowbari-Daryan, B., 1986, Upper Triassic, 

Dachstein-type reef limestone from the Wallowa Mountains, 

Oregon: first reported occurrence in the United States: Palaios, 

v.1, no. 2, p. 172-177. 

Stoppani, A, 1858-60, Les petrification d'Esino ou description des 

fossils appartenant au depot triassique superieur des environs 

d'Esino en Lombardie [The fossils ofEsino and the description of 

the fossils from the Upper Triassic around the vicinity ofEsino :in 

Lombardi]: Milano, p. 1-113. 

Tozer, E.T., 1967, A standard for Triassic time: Geological Survey of 

Canada Bulletin 156, 103 p. 

---1980, Latest Triassic (Upper Norian) ammonoid and Monotis 

faunas and correlations: Rivista Italiana di Paleontologia e 

Stratigrafia, v. 85, p. 843-876. 

---1982, Marine Triassic faunas of North America; their significance for assessing plate and terrane movements: Geologische 

Rundschau, v. 71, p.1077-1104. 

Vallier, T.L., 1974, A preliminary report on the geology of the Snake 

River Canyon, Oregon and Idaho: Oregon Department of 

Geology and Mineral Industries Geological Map Series MGS-6, 
36 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

15p. 

---1977, The Permian and Triassic Seven Devils Group: U.S. Geological Survey Bulletin 1437, 58 p. 

Wells, J.W., 1954, Recent corals of the Marshall Islands: U.S. Geological Survey Professional Paper 261-I, p. 385-486. 

Wilkens, Otto, 1937, Korallen und Kalkschwamme aus dem 

obertriadischen Pharetronenkalk von Seram (Mollukken) 

[Corals and calcareous sponges from the Upper Triassic Sparetronenkalk of Seram (Mollukks)]: neues Jahrbuch fur Mineralogie und Palaontologie, Stuttgart, v. 77, Abt B, p. 171-211. 

Winkler, G., 1861, Der Oberkeuper, nach studien in den Bayrischen 

Alpen [The Upper Keuper, after studies in the Bavarian Alps]: 

Zeitschrift Deutsche Geologische Gesellschaft, Berlin, v. 13, p. 

459-521. 

Zankl, H., 1971, Upper Triassic carbonate facies in the Northern Limestone Alps, in Muller, G., ed., Sedimentology in parts of Central 

Europe: International Sedimentological Congress, 8th, 

Heidelberg, Guidebook, p. 147-185. 
PLATE 3.1 

[Contact photograph of the plate in this chapter is available, at cost, from U.S. Geological Survey 

Library, Federal Center, Denver, Colorado 80225] 
PLATE 3.1 

Late Triassic corals and spongiomorphs from western Idaho and northeastern Oregon 

FIGURES 1-3. Stylophyllum paradoxum. 

1. Calical view, UMP 7288, x 3, Lewiston. 

2. Calical view of another specimen, UMP 7289, x 3, Lewiston. 

3. Calical view of a budded individual, UMP 7290, x 1.5, Lewiston. 

4-6. Distichophyllia norica. 

4. Calical view of somewhat weathered specimen, UMP 7292, x 2.25, 

Lewiston. 

5. Natural view of calyx showing pustulate surfaces of septa, UMP 7293, 

Lewiston. 

6. Side view of specimen in figure 4. Thin epitheca is absent, UMP 7292, 

x 2.25, Lewiston. 

7. Cyathocoenia cf. C. juvavica, UMP 7286, x 3. 75, Eagle Creek, southern 

Wallowa Mountains. 

8. Coccophyllum acanthophorum, showing sheetlike growth. Incrusted by 

large solitary Distichophyllum norica and a smaller thamnasteriid 

Pamiroseris smithi (arrow), USNM 252710, x 1.25, Lewiston. 

9. Coccophyllum acanthophorum, small tip of a branching colony showing the 

deeply sunken corallites, UMP 7291, x 3. 75, Lewiston. 

10. Cyathocoenia squiresi n. sp., showing details of corallite surface, KUMIP 

7287, X3.75, Lewiston. 

11. Cyathocoenia schafhaeutli, surface of corallum, USNM 252707, x 3. 75 

Lewiston. 

12. Astraeomorpha crassisepta, small nodular colony illustrating fungiform 

corallites, KUMIP 113705, x 2.25, Lewiston. 

13. Gablonzeria profunda, natural surface view of the corallum, UMP 7294, 

x 3, Lewiston. 

14. G. profunda, a deeply weathered specimen revealing deep open calices, 

UMP 7295, x 1.5, Lewiston. 

15. Spongiomorpha tenuis, details of a small branching coenosteum, KUMIP 

113662, x 1.5, Eagle Creek, southern Wallowa Mountains. 

16. Spongiomorpha ramosa, part of a branching coenosteum showing the 

irregularities of the surface, UMP 7296, x 2.25, Lewiston. 

17. Stromatomorpha sp., details of the surface of coenosteum, UMP 7297, x 1.5, 

Lewiston. 
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1435 PLATE 3.1 

1 2 

4 

5 

7 

8 

9 

12 

11 

13 

14 15 16 17 

STYLOPHYLLUM, DIST/CHOPHYLL/A, CYATHOCOENIA, COCCOPHYLLUM, 

ASTRAEOMORPHA, GABLONZERIA, SPONGIOMORPHA, STROMA TOMORPHA 

4. A NORIAN (LATE TRIASSIC) ICHTHYOSAUR FROM THE MARTIN 

BRIDGE LIMESTONE, WALLOWA MOUNTAINS, OREGON 

By WILLIAM N. 0RR1 

ABSTRACT 

Ichthyosaur fossils of the genus Shastasaurus were recovered 

from the Martin Bridge Limestone (Norian Stage, Upper Triassic) of 

northeastern Oregon. Ichthyosaurs are known only from scattered 

localities worldwide in the interval from the Middle Triassic to the 

Late Cretaceous. The occurrence of this aquatic reptile in the Oregon 

Triassic is consistent with, but not conclusive evidence for, recent 

paleotectonic hypotheses suggesting that parts of western North 

America, including areas of eastern Oregon, are composed of exotic 

accreted terranes. 

INTRODUCTION 

One of the most striking marine reptiles of the 

Mesozoic Era was the streamlined fish-like ichthyosaur. 

Fragmentary skeletal remains of these reptiles have 

been described from scattered localities around the 

world in the time interval from the Middle Triassic to 

the latest Cretaceous. Ichthyosaur remains have been 

reported from every continent except Mrica and Antarctica. Their distribution may reflect the effects of 

global tectonics in the interval prior to and during the 

break-up of Gondwanaland in the Mesozoic. Some of the 

most complete and best preserved ichthyosaur fossils 

known are from Jurassic localities in England and Germany, where well-preserved articulated specimens have 

been found in a variety of rocks including shale, 

mudstone, and limestone. Isolated ichthyosaur centra 

(vertebrae) have turned up in many marine Mesozoic 

sequences in America, but major North American areas 

for ichthyosaur remains are limited to Triassic rocks in 

the Shoshone Range of Nevada and in Shasta County of 

northern California, Jurassic rocks in Alberta, Canada, 

and Cretaceous rocks in Wyoming. 

Much of the research carried out on ichthyosaurian 

paleontology in the United States was by John C. Merriam of the University of California near the turn of the 

century. Several · new taxa were described by Merriam 

from localities in Nevada and the Pacific slope area of 

northern California (fig. 4.1). His work was summarized 

1 Department of Geology, University of Oregon, Eugene, Oregon, 97 403 

in a series of monographs that still stand as the prime 

American references to the group. One of the most spectacular ichthyosaur finds in North America was only 

recently described by Camp (1980). Triassic (Karnian) 

rocks of the Luning Formation exposed in the Shoshone 

Range, Nye County, Nevada, have yielded about 40 

articulated ichthyosaur skeletons. Several of the skeletons are displayed in place in a series of quarries at the 

Ichthyosaur State Park, Nevada. 

Although marine Mesozoic sedimentary rocks are 

exposed over wide areas of southwestern, central and 

northeastern Oregon, ichthyosaurs in that region are 

rare. Merriam and Gilmore (1928) described and figured 

two cervical vertebrae collected by Earl Packard from 

the Cretaceous Hudspeth Formation in Wheeler 

County, north-central Oregon. The bones were associated with Albian Stage molluscs. Because of the limited 

material, it was not possible to assign even a generic 

name to the find. Marsh (1895) briefly noted a single 

ichthyosaur vertebra found in the Blue Mountains but 

N 

1 

? ® (J)' 

® 

NEVADA 

~ffiRNIA 

ICHTHYOSAUR LOCALITIES 

D Wallow a Mountains; this report 

D Other Triassic 

1. Merriam (1908) 

2. Merriam (1908) 

3. Camp (1980) 

0 Jurassic 

4. Camp (1942) 

5. Camp and Koch (1966) 

6. McGowan (1978b) 

0 Cretaceous 

7. Marsh (1895) 

8. Merriam and 

Gilmore (1928) 

500 KILOMETERS 

FIGURE 4.1.-Ichthyosaur localities in the Northwestern United 

States. The age of rocks at locality 7 is uncertain. 

41 
42 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

did not illustrate or assign an age to this specimen. In 

1961 Norman Peterson, working in southwest Oregon, 

collected an ichthyosaur rostrum and well-preserved 

teeth. This fine specimen from the Otter Point Formation in the Klamath Mountains province was later 

described by Camp and Koch (1964) and identified as the 

species Ichthyosaurus californicus. They assigned the 

material to the Late Jurassic (Tithonian) on the basis of 

molluscs in the same strata. The only other ichthyosaurian material reported from Oregon to date was 

noted by McGowan (1978b) who recognized vertebral 

centra from the Nicely Formation of Early Jurassic 

(Pliensbachian) age in east-central Oregon. As with the 

Cretaceous material described by Merriam and Gilmore 

(1928), McGowan (1978b) did not attempt to make a 

generic assignment but stated that the centra are consistent with Ichthyosaurus. This genus is also known 

from the Lower Jurassic of England and the Lower 

Jurassic Nordegg Formation of Alberta. 

The specimens reported in this paper from Baker 

County, Oregon, are from Norian (Upper Triassic) rocks 

of the Martin Bridge Limestone. In comparison with the 

rest of the Mesozoic, there is a notably high diversity of 

ichthyosaurs in the Late Triassic (six known genera). In 

spite of this, previously described fossils of these reptiles in this time interval are known only from areas in 

Italy, Nevada, and California. 

The fossils reported here represent the largest volume of ichthyosaur bone material recovered to date in 

Oregon. They comprise 23 articulated vertebrae, neural 

arches and ribs. These elements are assignable to the 

genus Shastasaurus, known until now only from Upper 

Triassic rocks in northern California. 

ACKNOWLEDGMENTS 

Kurt Katsura and the 1981 University of Oregon 

summer field party are thanked for collecting the specimens used in this study. William Kelley of the University of Oregon Museum of Natural History performed 

much of the preparation of the bone material. Howard 

Brooks, Tracy Vallier, Cathryn Newton and Norm Silberling kindly reviewed the manuscript. 

GEOLOGY AND STRATIGRAPHY 

Fossil bone specimens described here are all from 

the Martin Bridge Limestone (Vallier, 1977) at its type 

section in the southern Wallowa Mountains of northeastern Oregon (fig. 4.2). The Martin Bridge is up to 600 

meters thick and consists of well-indurated fossiliferous 

massive to thin-bedded limestones with lesser amounts 

of shale. The Martin Bridge Limestone unit is overlain 

.__ __ ___::_;sao METERS 

FIGURE 4.2.-Location of ichthyosaur locality in Wallowa Mountains, 

Oregon. Distribution of Martin Bridge Limestone (stippled) after 

Vallier (1967). Contours in feet. 

by the Upper Triassic and Lower Jurassic H urwal Formation and underlain by the Permian and Upper Triassic Clover Creek Greenstone (fig. 4.3; Ross, 1938; 

Prostka, 1962) 

The pre-Cretaceous rocks of northeast Oregon have 

been divided into four terranes believed to represent 

allochthonous oceanic and island arc material that was 

accreted to the North American plate during the Mesozoic (Vallier, 1977; Brooks and Vallier, 1978; Brooks, 

1979; Dickinson, 1979). Eastern Oregon at that time may 

have resembled a convergent plate boundary region 

UNNAMED 

SEDIMENTARY 

ROCKS 

A CLOVER CREEK 

GREENSTONE 

FIGURE 4.3.-Partial stratigraphic column for southern Wallowa 

Mountains, Oregon, showing position of the ichthyosaur locality. 
4. A NORIAN ICHTHYOSAUR FROM THE MARTIN BRIDGE LIMESTONE, WALLOWA MOUNTAINS, OREGON 43 

similar to present-day complex volcanic island arcs like 

the Marianas of the western Pacific. The Martin Bridge 

Limestone is part of the Wallowa-Seven Devils arc terrane of Mullen and Sarewitz (1983). This terrane may 

have been accreted to the continent sometime during 

the Late Triassic to Middle Cretaceous. Within the Wallowa-Seven Devils arc terrane Permian and Triassic 

volcanic rocks and sediments 6,000 meters thick represent typical volcanic island-arc constituents. The Martin Bridge Limestone, consisting of platform carbonate 

rocks and shales, has yielded conodonts of Norian age 

(Sarewitz, 1982) and cephalopods of early and middle 

Norian age (Silberling and Tozer, 1968). Newton (1982 

and this volume) described Norian benthic invertebrate 

faunas from the Martin Bridge in Hells Canyon. Her 

reconstruction of the Martin Bridge paleoenvironment 

suggests a current-swept shallow marine shelf edge. 

LOCALITY 

Fossil ichthyosaurian bones were collected by the 

University of Oregon 1981 summer camp field party 

from roadcut exposures in the Wallowa-Whitman 

National Forest along Eagle Creek at the intersection 

with Paddy Creek in the NW% sec. 21, T. 7 S., R. 44 E. 

Seven meters of massive limestone interbedded with 

black calcareous shales are exposed here along the road. 

Smith (1912) measured a 200-meter section of the Martin Bridge in this immediate vicinity. Vertebrate fossil 

material at the locality is readily visible owing to the 

dark color of the bone against the matrix of gray limestone. The resistant bone material also stands out in 

relief above the more easily eroded limestone. Fossils 

described here were all collected from immediately 

below a prominent shale layer very near the base of the 

Martin Bridge Limestone. Associated with the ichthyosaur bones is a diverse assemblage of marine invertebrates dominated by cephalopods and pelecypods. 

PALEONTOLOGY 

Twenty-three intact vertebrae with attached neural 

arches and associated ribs were collected from two sites 

at nearly the same stratigraphic level. The material 

consists of cervical and anterior dorsal centra and is all 

assignable to the genus Shastasaurus Merriam. The 

vertebrae, particularly in the dorsal series, are comparatively large for a Triassic form and indicate an 

individual on the order of 2 meters long. Centra were 

found arranged in echelon in opposite directions from a 

break in the vertebral column. A similar imbricate orientation of centra has been reported by Kauffman (1981) 

in Jurassic ichthyosaurs preserved in the Posidonienschiefer sequence of Germany. He interpreted the 

echelon orientation of the centra as a taphonomic 

artifact of carcass decay penecontemporaneous with 

burial. 

Shastasaurus Merriam 

Plate 4.1, figures 1-8 

Shastasaurus Merriam, 1895, Amer. Jour. Sci., v. 5, p.56. 

Shastasaurus osmonti Merriam, 1902, Univ. Calif, 

Publ. Geol. Sci., v. 3, p. 93, pls. 3, 9, 10, 11. 

Shastasaurus cf S. osmonti Merriam 

Description.-Vertebrae centra circular, greatest 

diameter of centrum faces average 40 mm on the cervicals and 64 mm on the dorsals. Greatest thickness 

through the vertebra averages 22 mm on cervicals and 

32 mm on the dorsals. Vertebrae bi-concave with a distinctive hour-glass cross section flared all the way from 

the periphery of the centrum face (fig. 4.4). Parapophyses well developed in the anterior (cervical) series 

but disappearing gradually in the posterior dorsal 

series. 

Diapophyses abbreviated at anterior end of vertebral column. Toward posterior of series, diapophyses 

elongate to accommodate the missing parapophyses. 

The excavation on the centra below the neural arch is a 

broad shallow groove split by a low median ridge. Neural arches elongate, well-developed and round in cross 

section, displaying slight lateral compression. Neural 

arches are all free and the arch pedicels extend laterally. 

Ribs doubleheaded only in the anterior part of the vertebral column. Anterior double-headed ribs are flattened with a shallow longitudinal groove. Rib cross 

section in double-headed series markedly dumbbell 

shaped at the proximal end to circular or slightly ovoid 

at the distal end. 

A 8 

0 2 3 CENTIMETERS 

FIGURE 4.4-Cross sections of centra of Shastasaurus from Wallowa 

Mountains, Oregon. A, Centrum from cervical region.B, Centrum 

from anterior dorsal region. 
44 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

Discussion.-The genus Shastasaurus is characterized by Merriam (1902) as having biconcave centra 

with concave even surfaces beginning close to the centrum's periphery. Longitudinal diameter of the centra is 

much shorter than the vertical or transverse except in 

the caudals. Wallowa material includes only cervical 

and dorsal elements. Cervical vertebrae, according to 

Merriam, are somewhat broader than high and this is 

shown by the Wallowa material. Rib morphology in the 

anterior vertebrae is one of the most distinctive features 

of the genus. Two sets of articular surfaces, the 

diapophyses and parapophyses, are apparent on the 

cervical series, but the latter gradually decrease in size 

posteriorly and disappear at about the fifteenth vertebra. Cervical ribs fit the vertebrae articulation, displaying a well-developed tubercule and diminished 

capitulum. As the parapophysis disappears at about 

one-fourth of the length of the vertebral column, the rib 

capitulum is also lost. Merriam suggest that S. osmonti 

had about 50 vertebrae. Wallowa specimens compare 

very well with Merriam's type specimen of S. osmonti, 

particularly in the critical details of rib articulation and 

corresponding morphology of cervical and dorsal centra. 

One significant departure is in height of the neural 

arches. Wallowa specimens compare well in this measurement in the cervicals, but in the dorsals they are 15 

to 20 mm taller than the type specimen of S. osmonti or 

any other shastasaurid (table 4.1). 

ICHTHYOSAUR DISTRIBUTION 

Ichthyosaur remains are known worldwide in the 

interval from the Middle Triassic to the latest Cretaceous (fig. 4.5). In the Middle Triassic only four genera 

are known: Pessosaurus, Possopteryx, Cymbospondylus, 

and Mixosaurus. The first three genera are known only 

from single localities in Spitzbergen and Nevada, but 

species of Mixosaurus have been reported from a striking range of environments and areas including Timor, 

China, Switzerland, Spitzbergen, the Canadian Arctic, 

Alaska and Nevada. Because of the difficulties of making species assignments to many ichthyosaurian 

remains, discussions here are confined to the generic 

level. 

In the Late Triassic, the Ichthyosauria appear to be 

more provincial than in the Middle Triassic, but this 

may be only a reflection of the meager fossil record. All 

six genera reported from the Upper Triassic are known 

only from single localities. Although it is cosmopolitan 

in the Middle Triassic, Mixosaurus is reported from a 

single Upper Triassic locality in Italy. The five other 

Late Triassic genera, Merriamia, Delphinosaurus, 1bretoenemus, Shastasaurus and Shonisaurus are known 

from single localities in California and Nevada. 

TABLE 4.1.-Dimensions of centra ofShastasaurus cf S. osmonti Merriam from the Martin Bridge Limestone, Wallowa Mountains, 

Oregon 

[All figures in millimeters. Figures in parentheses are estimates or projections made 

because bone is fractured or distorted. Blank spaces indicate structure not present 

or preserved·! 

Dimensions of centrum Heights of individual 

f e atures 

Vertebra Height Width Length Diapo- Parapo- Neural 

physis physis arch 

Series 1 

1st 39 41 22 19 (8) 54 

2nd 38 40 21 20 9 (52) 

rn 3rd (40) (45) (23) (20) (ll) (51) .--1 

o:l 4th 40 46 20 20 10 52 (.) 

.,., 5th 41 48 21 (19) (9) (52) > 6th 43 48 23 20 11 (51) ,._. 

<l) 

u 7th 44 so (22) (21) 8 (SO) 

8th 45 so 24 23 7 (52) 

9th (47) (52) (26) (27) (5) 54 

rn lOth 48 51 27 26 2 54 .--1 

o:l 11th so 51 29 29 (2) (67) rn 12th 54 53 29 (33) ,._. 

0 

~ 13th 55 52 28 32 

Series 2 

1st 75 72 33 47 83 

2nd 77 75 32 47 84 rn 

.--1 3rd (75) (71) (30) (48) (90) o:l 

rn 4th (7 4) 73 31 (47) (87) ,._. 

0 5th (76) 75 35 so (85) ~ 6th 75 73 34 (51) 86 

7th 76 77 33 55 (83) 

Triassic ichthyosaurs are readily distinguished 

morphologically from Jurassic and Cretaceous forms. 

Halstead (1968, p. 136-138) has suggested that Triassic 

forms were fish predators, whereas Jurassic ichthyosaurs fed predominantly on cephalopod molluscs. 

In this regard, Pollard (1968) has published a fascinating detailed study of the stomach contents of an Early 

Jurassic ichthyosaur from England wherein he records 

an abundance of preserved cephalopod remains. 

Despite their reported rapid evolution (McGowan, 

1972a) and the local abundance of material, early Lias 

(Jurassic) ichthyosaurs are known from three general 

geographic areas in Canada, Germany, and England, 

The genus Stenopterygius is reported from the latter 

two areas, but the genera Leptopterygius and Thmnodontosaurus are known only from England. In the early 

Lias interval, Icthyosaurus is known from England and 

Alberta, Canada. Material from the Jurassic Nicely Formation in Oregon may be of this genus. Early Lias forms 

include only two genera, and they are confined to 

England and Germany. Stenopterygius occurs in both 

areas, whereas Eurhinosaurus is known only from Germany. The Late Jurassic form Ophthalomosaurus is 

cosmopolitan and has been reported from England, the 
4. A NORIAN ICHTHYOSAUR FROM THE MARTIN BRIDGE LIMESTONE, WALLOWA MOUNTAINS, OREGON 45 

FIGURE 4.5.-Global distribution of major ichthyosaur localities. 1. 

Alberta, Canada (McGowan, 1978b) (Jurassic); 2. Wyoming (Nace, 

1939, 1941; Romer, 1968b) (Cretaceous); 3. Oregon (Merriam and 

Gilmore, 1928; McGowan, 1978b; this paper) (Triassic, Jurassic, 

Cretaceous). 4. Texas (Slaughter and Hoover, 1963, McNulty and 

Slaughter, 1962) (Cretaceous). 5. California (Camp, 1942; 1980; 

Merriam, 1908) (Triassic, Jurassic). 6. Nevada (Camp, 1980; Merriam, 1908 ) (Triassic ). 7. Alaska (McGowan, 1978b) (Triassic). 8. 

Canadian Arctic (McGowan, 1978b) (Triassic, Jurassic). 9. 

Saskatchewan (McGowan, 1978b) (Cretaceous). 10. Spitzbergen 

(Hulke, 1872; Wiman, 1910, 1916, 1929 ) (Triassic). 11. Russia 

Canadian Arctic, western North America and Argentina. Early Cretaceous forms are comparable to those 

from the Middle Triassic in their worldwide distribution. A single genus, Platypterygius is known from Australia, India, Russia, England, Germany and North and 

South America. Ophthalomosaurus has been reported 

from Lower Cretaceous rocks at a single locality in Britain. Late Cretaceous occurrences are rare, but the fossil record has been expanding rapidly in the past decade 

as new forms are unearthed. The genus Platypterygius 

has been reported from the Upper Cretaceous of Australia, England, and Saskatchewan, Canada. The 

youngest ichthyosaur remains known to date are an 

unassigned taxon from the Maastrichtian Stage in New 

Jersey. 

The present state of the ichthyosaur fossil record 

may be summarized into three segments by time periods. The Triassic interval shows comparatively high 

diversity, but most of the taxa are provincial and known 

from single localities. Only the genus Mixosaurus is 

(McGowan, 1972b) (Cretaceous). 12. Britain (McGowan, 1974a, 

1976) (Jurassic).13. Germany(McGowan, 1974a,1979) (Jurassic).14. 

France (Lennier, 1870) (Cretaceous). 15. Switzerland (KuhnSchnyder, 1964) (Triassic). 16. Italy (Kuhn-Schnyder, 1964) (Triassic) 17. China (Young, 1965) (Triassic). 18. India (McGowan, 

1972b) (Cretaceous) 19. Timor (Von Huene, 1936) (Triassic). 20. 

Australia (Teichert and Matheson, 1944) (Cretaceous). 21. Australia (W.) (Teichert and Matheson, 1944) (Cretaceous). 22. Argentina (Rusconi, 1948) (Jurassic). 23. New Jersey (McGowan, 1978a) 

(Cretaceous). 

cosmopolitan in the Triassic. Jurassic rocks have 

yielded some of the best preserved and studied ichthyosaur fossils, but most of the forms are provincial 

except for Late Jurassic ones. Cretaceous ichthyosaurs 

fall into only two genera, yet one of these, Platypterygius, is the most cosmopolitan taxon known. In a 

very general way, therefore, ichthyosaur diversity and 

geographic distribution appear to be inversely related. 

The widespread distribution of the Triassic genus 

Mixosaurus suggests that even early Mesozoic ichthyosaurs may be too cosmopolitan to group taxa into 

geographic areas. A major anomaly in this regard is the 

absence of Mixosaurus in Camp's (1980) highly fossiliferous Triassic locality in Nye County, Nevada. One 

explanation for this might be paleoenvironmental. 

Camp (1980) reported that the Nevada ichthyosaurs are 

preserved in shaley limestone and mudstone. Localities 

of Triassic forms elsewhere in western North America 

described by Merriam (1908) are almost exclusively 

from carbonate rocks. 
46 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

In a report of the first record of the genus Stenopterygius from the early Lias of England, McGowan 

(1978b) discussed the global distribution of ichthyosaurs. The rapidly growing number of finds 

prompted his conclusion that these reptiles will eventually be shown to be both spatially and tern porally 

widespread. As evidence he cites the cosmopolitan generaMixosaurus, Ophthalmosaurus, Ichthyosaurus, and 

Platypterygius and attributes the limited known 

distribution of ichthyosaurs to the paucity of good fossilbearing exposures. On the other hand, the easy recognition of exotic forms as summarized in this paper suggests that ichthyosaurs might have been as provincial as 

they appear. 

Ichthyosaur morphology resembles that of modern 

open-ocean nektonic forms. Colbert (1980, p. 166-169) 

compares the hydrodynamics of ichthyosaurs to that of 

the speediest of modern fish such as mackerel and tuna. 

His view of the ichthyosaur is of a powerful fast swimmer, quite at home in the wide expanses of the Mesozoic 

seas. Romer (1968a) suggests the ichthyosaurs were as 

highly adapted to :marine life as modern porpoises or 

dolphins. 

The diversity of entombing matrices from which 

ichthyosaurs have been recovered also implies that they 

ranged over broad areas including the open seas at 

considerable distances from land. In this regard, a quote 

from Camp (1980) is interesting. In discussing the distribution of genera found in Nye County, Nevada, Camp 

notes that only a short distance away in northern California and at nearly the same stratigraphic interval 

Meriam (1908) reported a markedly different suite of 

ichthyosaurs. Camp (1980, p. 141) wrote: 

Strangely enough, the California ichthyosaurs included in four genera 

described by John C. Merriam (1908) lived at nearly the same time and 

in the same large embayment of the Pacific as the three species here 

re-covered from a sequence of some 160 meters of strata in Nevada. 

One of the youngest and latest of the species from the Upper Triassic 

of northern California, namely the lesser-known "Shastasaurus" 

careyi, is the larg~st species assigned to that genus and is possibly 

related to our Nevada forms. Yet the differences between the genera 

from the two regions are noteworthy and seem to indicate a rapid 

change in the ichthyosaur populations of the Nevada-California seaways. 

Merriam (1902, p. 87) also had noticed the provincial characteristics of the northern California taxa and 

wrote in this regard: 

That a group of marine reptiles with the characters of 

Shastasaurus would be confined within very narrow geographic limits 

is improbable, particularly as the occurrence of its remains points 

toward a fairly deep and open sea as its habitat. 

The anomalous occurrences and distributions 

noticed by both of the above authors may well be eventually explained by long-distance transport of accreted 

terranes. 

CONCLUSIONS 

The Oregon occurrence of the Triassic ichthyosaur 

Shastasaurus may have some significance for the 

tectonic history of western North America. The locality 

in the Wallowa Mountains is a few hundred kilometers 

north of the Nevada and California Triassic localities, 

but the fossil material is evidently closely affiliated only 

with the northern California ichthyosaur fauna. Known 

diversities and biogeographic distributions do not yet 

permit use of ichthyosaurs as markers for allochthonous 

terranes. On the other hand, the occurrence of 

Shastaurus in the Martin Bridge Limestone is consistent with other evidence of an allochthonous origin for 

the Wallowa-Seven Devils arc terrane. Because the 

genus Shastasaurus is known elsewhere only from 

northern California, the paleolatitude range for the 

form cannot be determined at present. 

REFERENCES CITED 

Brooks, H. C., 1979, Plate tectonics and the geologic history of the Blue 

Mountains: Oregon Geology, v. 41, no. 5, p. 71-80. 

Brooks, H.C., and Vallier, T.L., 1978, Mesozoic rocks and tectonic 

evolution of eastern Oregon and western Idaho, in Howell, D.G., 

and McDougall, K.A., eds., Mesozoic paleogeography ofthe Western United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogreography Symposium 2, p. 133-146. 

Camp, C.L., 1942, Ichthyosaur rostra from central Califronia: Journal 

ofPaleontology, v. 16, no. 2, p. 251-271. 

--1980, Large ichthyosaurs from the Upper Triassic of Nevada: 

Paleonto-graphica, Bd. 170, Abt. A, p. 139-200. 

Camp, C.L., and Koch, J.G., 1966, Late Jurassic ichthyosaur from 

coastal Oregon: Journal of Paleontology, v. 40, no. 1, p. 204-205. 

Colbert, E.H., 1980, Evolution of the vertebrates, 3d ed.: New York, 

Wiley, 510 p. 

Dickinson, W.R., 1979, Mesozoic forearc basin in central Oregon: 

Geology, v. 7, no. 4, p. 166-170. 

Halstead, L.B., 1968, The pattern of vertebrate evolution: San Francisco, Freeman, 209 p. 

Hulke, J.W., 1872, Memorandum on some fossil vertebrate remains 

collected by the Swedish expeditions to Spitzenbergen in 1864 

and 1868: Bihang till Kongl. Svenska Vetenskaps-Akademien 

Handlingar, n.s., Bd. 1, no. 9, p. 2-11. 

Kauffman, E.G., 1981, Ecological reappraisal of the German Posidonienshiefer (Toarcian) and the stagnant basin model, in Gray, 

Jane, and others, eds., Communities of the past: Stroudsburg, 

Penn., Hutchinson Ross, p. 311-381. 

Kuhn-Schnyder, E., 1964, Die Wirbeltierfauna der Trias der Tessiner 

Kalkalpen: Geologische Rundschan, v. 53, p. 393-412. 

Lennier, G., 1870, Etudes geologiques et paleontologiques sur I' embouchure de la Siene et les falaises de la Haute-Normandie: Havre, 

245 p. 

Marsh, O.C., 1895, The Reptilia of the Baptanodon Beds: American 

Journal of Science, 3d ser., v. 50, p.406- 409. 

McGowan, Christopher, 1972a, Evolutionary trends in longipinnate 

ichthyosauras with particular reference to the skull and fore fin: 

Royal Ontario Museum, Life Sciences Contributions, no. 83, 

38 p. 
4. A NORIAN ICHTHYOSAUR FROM THE MARTIN BRIDGE LIMESTONE, WALLOWA MOUNTAINS, OREGON 4 7 

---1972b, The Systematics of Cretaceous ichthyosaurs with particular reference to the material from North America: Contributions to Geology (University of Wyoming), v. 11, no. 1, p. 9-29. 

---1973, A note on the most recent ichthyosaur known; an isolated 

coracoid from the upper Campanian of Saskatchewan (Reptilia, 

Ichthyosauria): Canadian Journal of Earth Sciences, v. 10, no. 8, 

p.1346-1349. 

---1974a, A revision of the logipinnate ichthyosaurs of the Lower 

Jurassic of England, with descriptions of two new species (Reptilia: Ichthyosauria): Royal Ontario Museum, Life Sciences Contributions, no. 97, 37 p. 

---1974b, A revision ofthe latipinnate ichthyosaurs of the Lower 

Jurassic of England (Reptilia: Ichthyosauria): Royal Ontario 

Museum, Life Sciences Contributions, no. 100, 30 p. 

---1976, The description and phenetic relationships of a new ichthyosaur genus from the Upper Jurassic of England: Canadian 

Journal of Earth Sciences, v. 13, p. 668-683. 

---1978a, An isolated ichthyosaur coracoid from the Maastrichtian 

of New Jersey: Canadian Journal of Earth Sciences, v. 15, p. 

169-171. 

---1978b, Further evidence for the wide geographical distribution 

of ichthyosaur taxa (Reptilia: Ichthyosauria): Journal of Paleontology, v. 52, no. 5, p.1155-1162. 

---1979, A revision of the Lower Jurassic ichthyosaurs of Germany 

with description of two new species: Paleontographica Adt. A, 

Bd. 166, p. 93-135. 

McNulty, C.L., and Slaughter, B.H., 1962, An ichthyosaurian centrum 

from the Albian of Texas: Journal of Paleontology, v. 36, no. 2, p. 

346-347. 

Merriam, J.C., 1895, On some reptilian remains from the Triassic of 

northern California: American Journal of Science, v. 1, p. 55. 

---1902, Triassic ichthyopterygia from California and Nevada: 

University of California Publications, Department of Geology 

Bulleton, v. 3, no. 4, p. 63-108. 

---1903, New ichthyosauria from the Upper Triassic of California: 

University of California Publications, Department of Geology 

Bulletin, v. 3, no. 12, p. 249-263. 

---1908, Triassic ichthyosauria, with special reference to the 

American forms: University of California Memoirs, v. 1, no. 1, 

156p. 

Merriam, J.C., and Gilmore, C.W., 1928, An ichthyosaurian reptile 

from marine Cretaceous of Oregon: Carnegie Institution Contributions to Paleontology, no. 393, p. 3-4. 

Mullen, E.D., and Sarewitz, Daniel, 1983, Paleozoic and Triassic terranes of the Blue Mountains, northeast Oregon: discussion and 

field trip guide. Pt. 1: a new consideration of old problems: 

Oregon Geology, v. 45, no. 6, p. 65-68. 

N ace, R.L., 1939, a new ichthyosaur from the Upper Cretaceous Mowry 

Formation of Wyoming: American Journal of Science, v. 237, p. 

673-686. 

---1941, A new ichthyosaur from the Late Cretaceous, northeast 

Wyoming: American Journal of Science, v. 239, p. 908-914. 

Newton, C.R., 1982, Norian (Late Triassic) bivalved molluscs of Cordilleran allochthonous terranes: paleoecology and paleozoogeography: Santa Cruz, University of California, Ph.D. dissertation, 154 p. 

Pollard, J.E., 1968, The gastric contents of an ichthyosaur from the 

lower Lias of Lyme Regis, Dorset: Palaeontology, v. 11, pt. 3, p. 

376-388. 

Prostka, H.J., 1962, Geology of the Sparta Quadrangle, Oregon: 

Oregon Department of Geology and Mineral Industries, Geologic Map Series GMS-1. 

Romer, A.S., 1968a, Notes and comments on vertebrate paleontology: 

Chicago, University of Chicago Press, p. 110-112. 

---1968b, An ichthyosaur skull from the Cretaceous ofWyoming: 

Contributions to Geology (University ofWyoming), v. 1, p. 27-41. 

Ross, C.P., 1938, Geology of part of the Wallowa Mountains: Oregon 

Department of Geology and Mineral Industries, Bulletin 3, p. 

32-37. 

Rusconi, Carlos, 1948, Ictiosaudos del Jurasico de Mendoza (Argentina): Mendoza Museo de Historia Natural, Revista, v. 2, p. 

17-160. 

Sarewitz, Daniel, 1982, The nature and evolution of the eastern margin of the Seven Devils volcanic arc: a piece ofWrangellia [abs.]: 

Geological Society of America Abstracts with Programs, v. 14, no. 

3, p.130. 

Silberling, N.J., and Tozer, E.T., 1968, Biostratigraphic classification of 

the marine Triassic in North America: Geological Society of 

America Special Paper 110, 63 p. 

Slaughter, B.H., and Hoover, B.R., 1963, Occurrences of ichthyosaurian remains in the Cretaceous ofTexas: Texas Journal of 

Science, v. 15, p. 339-343. 

Smith, J.P., 1912, The occurrence of coral reefs in the Triassic of North 

America: American Journal of Science, 4th ser., v. 33, no. 194, p. 

92-96. 

Teichert, C., and Matheson, R.S., 1944, Upper Cretaceous ichthyosaurian and plesiosaurian remains from Western Australia: 

Australian Journal of Science, v. 6, p. 167-170. 

Vallier, T.L., 1967, The geology of part of the Snake River Canyon and 

adjacent areas in northeastern Oregon and western Idaho: Corvallis, Oregon State University, Ph.D. dissertation, 267 p. 

---1977, The Permian and Triassic Seven Devils Group, western 

Idaho and northeastern Oregon: U.S. Geological Survey Bulletin 

1437, 58 p. 

Von Huene, F., 1936, Ichthyosaurierreste aus Timor: Zentralblat Mineralogie Geologie Palaeontologie, Abt. B, Monatschafte, p. 

327-334. 

Wiman, C., 1910, Ichthyosaurier aus der Trias Spitzbergen: Bulletin 

Geological Institute University ofUppsala, v. 10, p. 124-148. 

---1916, Notes on the marine Triassic reptile fauna of Spitzenbergen: University of California Publications, Department of 

Geology, Bulletin, v. 10, no. 5, p. 63-73. 

---1929, Eine neue marine Reptilien-Ordnung aus der Trias 

Spitzbergens: Bulletin Geological Institute University of 

Uppsala, v. 22, no. 4, p. 183-196. 

Young, C. C., 1965, On a revised determination of a fossil reptile from 

Jenhui, Kweichow, with a note on a new ichthyosaur probably 

from China: Vertebrata Palasiatica, v. 9, no. 4, p. 368-375. 

PLATE 4.1 

[Contact photograph of the plate in this chapter is available, at cost, from U.S. Geological Survey 

Library, Federal Center, Denver, Colorado 80225] 
PLATE 4.1 

[All figures x 0.65] 

FIGURES 1-8. Shastasaurus cf. S. osmonti Merriam from the Martin Bridge Limestone, Wallowa 

Mountains, Oregon. 

1-2. Anterior dorsal centra in lateral view. 

3-4. Anterior dorsal centra in face view. 

5. Cervical vertebra and rib fragments, showing grooved rib structure. 

6. Neural arch in cross section. 

7. Anterior dorsal centra in lateral view, showing echelon arrangement. 

8. Cervical vertebra in cross section and rib cross sections in a proximal 

area, showing rib grooves. 
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1435 PLATE 4.1 

1 2 3 

4 

5 

SHAST ASA UR US 

5. JURASSIC AMMONITES AND BIOSTRATIGRAPHY OF EASTERN 

OREGON AND WESTERN IDAHO 

By RALPH w. IMLAY 

ABSTRACT 

Jurassic clastic sedimentary rocks in the Blue Mountains region 

of eastern Oregon and western Idaho have furnished ammonites 

ranging from Hettangian to Oxfordian age. Jurassic beds are included 

in the lzee, Olds Ferry, and Wallowa terranes of Silberling and others 

(1984). 

The thickest, most complete, and best preserved Jurassic 

sequence is in the lzee terrane, where ammonite genera ofHettangian 

age are well represented. The Sinemurian and Pliensbachian stages 

are represented in the lzee, Olds Ferry, and Wallowa terranes. Toarcian and Bethonian ammonites have been found only in the lzeeSeneca area, whereas fauna of the intervening Bajocian are widespread in both the lzee and Olds Ferry terrances. The Bajocian genera 

include forms that are characteristic of the East Pacific realm. The 

Callovian is well represented in the Izee terrane and to a very limited 

extent in the Olds Ferry and Wallowa terranes. Some of the Callovian 

genera represent the Boreal Realm. 

The only known occurrence of the early Oxfordian ammonite 

Cardioceras (Scarburgiceras) found in the Western United States is 

on the Idaho side of Snake River near the southeast corner of Washington. 

INTRODUCTION 

The Jurassic sedimentary rocks in the Blue Mountains region of eastern Oregon and western Idaho have 

furnished ammonites ranging from Hettangian to early 

Oxfordian age. Jurassic beds are included in the lzee, 

Olds Ferry, and Wallowa terrances of Silberling and 

others (1984). The Jurassic sequences consist mostly of 

graywacke, shale, and siltstone but locally include considerable volcanic material and minor amounts of limestone and conglomerate. 

The thickest and most complete Jurassic stratigraphic sequence is in the lzee terrane. The rocks there 

are only weakly metamorphosed and deformed, and 

fossils are abundant. The section has been divided into 

more than 10 formations. The sequence has a total thickness of 7, 700 meters1 in the area between lzee and 

Seneca but thins westward to about 2,090 meters near 

Suplee. In the Suplee-lzee area, the Jurassic sequence 

is marked by unconformities (1) between the Upper Triassic and Sinemurian beds (except in the lzee area), (2) 

at the base of the lower Pliensbachian beds, (3) at the 

base of the Callovian beds, and (4) at the top of the 

uppermost Callovian beds. Except for the area between 

Suplee and lzee the Jurassic beds change considerably 

laterally, and dating and correlation are based mostly on 

the ammonites present. 

Jurassic beds in the Olds Ferry terrane comprise 

the Weatherby Formation (Brooks, 1979) in the eastern 

part of the terrane and unnamed beds of equivalent 

lithology and age in the western part. The sequence may 

be as much as 7,000 meters thick near the Snake River. 

Little variation in lithology is recognized throughout 

the exposure belt. The rocks are folded and cut by pervasive axial plane cleavage and are weakly metamorphosed. Ammonite fossils from those rocks have 

been collected from about 25 widely separated localities. 

In the Wallowa terrane, Lower Jurassic beds are 

represented in the upper 600 meters of the Hurwal 

Formation in the Wallowa Mountains south of Enterprise, Oregon. Early Oxfordian beds occur in the Coon 

Hollow Formation in Snake River Canyon near the 

Washington bordeL 

In previous papers (Imlay, 1964, 1968, 1973, 1981) I 

have described ammonites from eastern Oregon and 

western Idaho ranging in age from Pliensbachian to 

Oxfordian. The Hettangian and Sinemurian ammonites 

from that area have not yet been described. The 

ammonites studied were collected by many geologists, 

listed and acknowledged in the papers cited above. 

Their collections show that well-preserved ammonites 

occur in concretions obtained from shales, and that 

crushed or fragmentary ammonites mostly occur on 

bedding planes in soft shales. Some shales in which no 

megafossils can be seen on weathered surfaces actually 

contain identifiable fossil mollusks in the fresh rock. 

BIOSTRATIGRAPHIC SUMMARY 

The basal part of the Jurassic sequence in the Izee 

terrane (fig. 5.1) is present in the lzee-Seneca area and 

represented by the Graylock Formation and the Murderers Creek Graywacke (fig. 5.2), which are in different structural blocks. They are, respectively, 120 m 

and 915 m thick and contain ammonite genera of Hettangian age (Muller and Ferguson, 1939, p. 1612-1613; 

Hallam, 1965, p. 1490-1491). Those ammonites include 

53 
54 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

Waehneroceras and Psiloceras in the lower parts of the 

formations and Schlotheimia, Caloceras and Alsatites 

in the upper parts (Imlay, 1971, p. 713; 1980, p. 19-20). 

The conformably overlying Keller Creek Shale in 

the Izee-Seneca area is about 1,525 m thick. Ammonites 

from this unit include Arnioceras of early Sinemurian 

age and Eoderoceras and Crucilobiceras of latest Sinemurian age (Imlay, 1971, p. 713). The Keller Creek is 

overlain unconformably by the Robertson Formation of 

late early Pliensbachian age (Lupher, 1941, p. 235, 

245-247; Imlay, 1980, p. 20, 55). In the Huntington area 

farther east an unfossiliferous conglomerate 9-244 m 

thick is overlain by beds that contain the ammonites 

Arnioceras and Crucilobiceras, respectively of middle 

and late Sinemurian ages (Imlay, 1980, p. 56, 64). In the 

Wallowa Mountains near Enterprise, Oregon, the lower 

90 m of the Lower Jurassic part of the Hurwal Formation contain ammonites oflatest Sinemurian age (Smith 

and Allen, 1941, p. 6, 13, 14; Imlay, 1968, p. C7; Imlay, 

1980, p.65) and some ammonites that are probably of 

early Sinemurian age. 

OREGON 

0 

I I 

0 100 

120 

WASHINGTON 

100 

I 

John Day 

Suplee • 

.. "'. . Paulina Iz~ Seneca 

I 

200 

I 

200 MILES 

I 

300 KILOMETERS 

The Pliensbachian is represented in the SupleeIzee area of the Izee terrane by, from bottom to top, the 

Robertson, the Suplee, and the Nicely Formations. The 

Robertson Formation consists mostly of volcanic sandstone but includes some limestone units 2-12m thick 

and a basal conglomerate 10-25 m thick. It attains a 

maximum thickness of about 100 m, pinches out eastward, and grades laterally in other directions into the 

overlying Suplee Formation. It rests unconformably on 

the Graylock Formation (Hallam, 1965, p. 1489; Dickinson and Thayer, 1978, p. 157) of Hettangian age in the 

Suplee area and on the Keller Creek Shale of Sinemurian age in the Izee area. The Suplee Formation 

consists of gray limestone and limy sandstone, ranges in 

thickness from 9 to 45 m, and grades upward into the 

Nicely Formation. In its upper third the Suplee is 

characterized by the late Pliensbachian ammonites 

Arieticeras, Prodactylioceras, Leptaleoceras and Paltarpites (Imlay, 1968, p. C8, Fig. 5 on p. 16; 1980, p.55). The 

overlying Nicely Formation ranges in thickness from 25 

to 90 m and consists of dark gray to black limy siltstone 

MONTANA 

IDAHO 

FIGURE 5.1.-Index map showing localities mentioned in text for the general areas in which Jurassic ammonites occur in eastern Oregon 

and westernmost Idaho. 
5. JURASSIC AMMONITES AND BIOSTRATIGRAPHY OF EASTERN OREGON AND WESTERN IDAHO 55 

and claystone. It contains most of the same ammonite 

genera as the Suplee Formation and is therefore also of 

late Pliensbachian age. 

also in the upper 189 m of the Hurwal Formation 

exposed near Ent,erprise in the Wallowa Mountains 

(Imlay, 1968, p. C14-C15; 1980, p. 56, 65) ofthe Wallowa 

Late Pliensbachian ammonites have been found terrane. These ammonites include Canavaria, HarIZEE TERRANE OLDS FERRY WALLOW A TERRANE TERRANE 

"' Huntington-Brogan Wallowa Mountains Snake River canyon Characteristic Fossils 

"" Stage Suplee area Izee-Seneca area -Juniper Mtn areas Northeastern comer Pittsburg Landing ·.: near Enterprise, 32 miles south "" (west) (east) in eastern Oregon of Oregon VJ northeastern Oregon of northeast comer and Mineral, Idaho and adjacent states of Ore!!on 

Overlying beds Cenomanian Cenomanian Miocene Miocene Miocene Miocene 

0. 

0. 

::J 

u T ithonian 

,.__ 

~ 

~ ~ 

..:: s 

~ Kimmeridgian :::> 

T 

.3 .... 

"" 0. 0. 

0. 0. 

~ -=i- Oxfordian :g 

::E c:~;2;;;;= ---.::- 610 m Black mudstone; 

~ some graywacke and Cardioceras (Scarburgiceras) 

..J conglomerate manini (western Idaho only) 

g_ Lonesome Formation Fault contact at top Pseudocadoceras grewingki r2- 3050 m with Permian .,; Volcanic sandstone 

J:[;lockl 

Lilloettia stantoni, Xenocephalites Callovian ~ and black mudstone vicarius and Pseudocadoceras grewingki r-- Trowbri<!$e Shale Black phyhiti?ili"a~ l,illpetua .buckmant 

~ 915 m Mudstone Black shale 1 brown gray-

-~ 

~ and slate wacke, and con lomerate Kepplerites Xenocephalites 

..J I I_ Macrocephalites (~outhern California) 

~ r_-

..:; m Probably Parareineckda, Iniskinites, 

Bathonian r- Absent ~ Cobbanites, and Kepplerites / d mudstone, siltstone, 

~ sandstone •OO Y•> 0. South Fork(!) ti.. 

"' ~ 

~ Spiroceras, Leptosphinctes :a r-- s "0 Basey Member 

~ Schoolhou Teloceras, Chondroceras, Normannites 

" 150-750 m Member 3 Bajocian :g Warm Springs Member ~ Dorsetensia oregonensis 

::E 30- 150-225 m Papilliceras stantoni, Parabi~otites 

Weberg Member~ Dark limey siltstone, 7000 m (?) Euhoploceras, Docidoceras 

-:- ~75 m S1lty to !"'--{andy lime- claystone, Volc~nic wacke Praestrigites, Eudmetoceras I T~g{~~e~as ~ ~~~ and mudstone ; and siltstone, s some ?-

limestone beds minor tuff, 

conglomerate, g Catulloceras, Grammoceras c. ~ and Pseudolioceras 0. and limestone ::J ~ Haugia, Polyplectus, Catacoeloceras Toarcian 

--=- Hyde Formation ii: 

~ 210-450 m Massive 

s andesitic tuff and volcan ic graywacke ~ -

-~ ! . N_icely Formation 25-90 m -'---? .___'-- Arieticeras, Reynesoceras, Paltarpites, c. 

~ c. Dark limev clavstone and siltstone 

::J 1/ Suplee Formation 9-45 m 

~ Hurwal Formation Prodactyllioceras, and Leptaleoceras :::1 

-. r-- Gray limestone and limev sandstone Pliensbachian (upper part) 

~ I Robertson Formation 100 m _ ~ ~ 610 m 

..J -1 l . I lff ~ Angular Unconformity Jen Very hard, 

Creek dark gray to black Uptonia? 

Keller ? 

c. Creek Shale Member claystone and siltstone Eoderoceras an'd Crucilobiceras 0. 

1525 m 250m ::J Oxynoticeras .... Sinemurian Red and 

"' i-- Siltstone, ? ~ shale, and green 

0 ~ tuffaceous conglomerate; 

....l some limestone s graywacke and gypsum Arnioceras, Arietites, 

li Coroniceras and Regarietites 

Gray lock Murderers Schlotheimia and Alsatites Hettangian Creek Formation Graywacke 120m 915 m Wachneroceras and Psiloceras 

Underlying Beds Paleozoic\ Triassic Upper Triassic Upper Triassic Upper Triassic Upper Triassic Upper Triassic 

I) Unit named by Smith (1980). 

FIGURE 5.2.-Correlations and comparisons of Jurassic rocks in eastern Oregon and western Idaho. Parallel vertical lines indicate that strata 

of that age are not present. Wavy lines indicate presence of unconformities or disconformities; jagged lines indicate gradational or indefinite 

contacts. 
56 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

poceras, Arieticeras, Prodactylioceras, Protogrammoceras and Fuciniceras. Early Pliensbachian ammonites 

have not yet been found in Oregon or in California. 

The Toarcian in the Blue Mountains has been identified faunally only in the lzee-Seneca area where it is 

represented by the basal 38 m of the Snowshoe Formation. The fauna consists of Haugia, Polyplectus, Catacoeloceras and, at a higher level, Catulloceras, 

Grammoceras andPseudolioceras. All of these forms are 

oflate Toarcian age (Imlay, 1968, p. C14, C15, C18; 1980, 

p. 20 ). The black shale of the Snowshoe Formation from 

which these ammonites were obtained contains black 

limestone concretions and resembles the black shale in 

the Nicely Formation. 

Underlying the Snowshoe Formation is the Hyde 

Formation, which is about 310 to 450 m thick and consists mostly of thick-bedded to massive sandstone. It 

grades rather abruptly upward into the Snowshoe Formation and more gradually downward into the Nicely 

Formation. The Hyde Formation is dated as early Toarcian mainly on the basis of its stratigraphic position, 

although some shell fragments of ammonites resembling taxa in the Snowshoe Formation have been noted 

by Lupher (1941, p. 259, 262). 

The Bajocian succession in the Suplee area consists 

of, from bottom to top, the Weberg, Warm Springs and 

Basey Members of the Snowshoe Formation. These are 

bounded at top and bottom by pronounced unconformities (Fig. 5.2) and attain a thickness of about 335 m. 

In the lzee area to the east the Weberg Member changes 

from a silty or sandy limestone or limy sandstone to soft 

dark-gray siltstone and claystone that are essentially 

identical with beds in the Warm Springs Member. The 

Warm Springs Member thickens eastward into the Izee 

area and its base becomes older. The Basey Member 

consists of volcaniclastic sedimentary rocks and some 

lava in the Suplee area. Correlative beds in the Izee area 

farther east consist of siltstone, sandstone, and some 

claystone that have generally been assigned to the middle member of. the Snowshoe Formation, but have 

recently been named the Schoolhouse Member by Smith 

(1980, p. 1605). Nearly correlative beds cropping out 

northeast of lzee near the Silvies River are named the 

Silvies Member and consist of siltstone, coarse-grained 

sandstone and conglomerates. Both the Schoolhouse 

Member and the Silvies Member are overlain by Smith's 

(1980) South Fork Member, which differs from them by 

containing some thick beds of sandstone. These 

sequences attain a thickness of at least 800 min the lzee 

area and are probably thicker in the Seneca area. 

Bajocian ammonites in eastern Oregon occur in five 

inliers spaced over a distance of 192 km from Paulina on 

the west to the Snake River on the east (Wagner and 

others, 1963, p. 687-691, figs. 1, 2; Imlay, 1973, pl. 48). The 

ammonite succession is essentially the same as the 

Bajocian succession in southern Alaska (Imlay, 1973, p. 

21, 31-33), except that it lacks the genera Liroxyites, 

Bradfordia and Pseudolioceras. The succession is also 

similar to that in Europe (Imlay, 1973, p. 35, 36), but 

differs from the Bajocian succession in central and 

southern France by the presence of such forms as 

Pseudotoites, Parabigotites, Zemistephanus, Megasphaeroceras and Lupherites which characterize the 

East Pacific Realm. It differs also by lacking certain 

ammonite genera that in Europe represent the lowest 

two zones of the lower Bajocian and the upper two zones 

of the upper Bajocian. 

Bathonian beds have been identified faunally in 

eastern Oregon only in the lzee area, where they constitute the upper 210 m of the South Fork Member 

(Smith, 1980, p. 1605) at the top of the Snowshoe Formation (Imlay, 1981, p. 6-10, Figs. 5-6, tables 3-4). The rocks 

consist of dark gray siltstone and claystone and some 

fairly thick beds of volcanic sandstone. Faunally they 

are characterized by the ammonites Iniskinites, and 

Cobbanites, which are not known above the upper 

Bathonian, and by their association with 

Xenocephalites, Kepplerites and 'Ibrricelliceras, which 

are not known below the upper Bathonian and whose 

lowest occurrences are respectively 190m, 170m and 180 

m below the top of the South Fork Member. Of these 

genera Xenocephalites, Iniskinites, and Cobbanites 

characterize the East Pacific Realm; Kepplerites and 

'Ibrricelliceras are most common in the Boreal Realm. 

The early Bathonian could be represented by part of the 

250-m unfossiliferous section that underlies these fossiliferous beds of late Bathonian age and overlies beds 

that contain Leptosphinctes of early late Bajocian age. 

The Callovian is represented in the lzee terrane by 

the Trowbridge Shale and the conformably overlying 

Lonesome Formation. These formations crop out in the 

lzee, Delintment Lake, West Myrtle Butte and 

Sawtooth Creek quadrangles (Imlay, 1981, p.11, table 5). 

The Trowbridge Shale (Imlay, 1981, p. 4-7, fig. 3, 5, table 

2) occurs in four small areas in eastern Oregon. It consists of black shale, generally ranges in thickness from 

300m to 1,100 m, thickening northeastward, and rests 

unconformably on either the South Fork Member or the 

Basey Member of the Snowshoe Formation. In the lzee 

area the Trowbridge Shale thins rapidly toward the 

southwest to only 30m. Near its middle the unit contains ammonites including Lilloettia, Kepplerites and 

Xenocephalites. The presence of Lilloettia and the 

absence of Cobbanites and Iniskinites indicate an early 

Callovian age for the Trowbridge Shale. 

Black shales that crop out near Pittsburg Landing 

in the Wallowa terrane and near Mineral, Idaho, in the 

Olds Ferry terrane contain ammonites similar to those 
5. JURASSIC AMMONITES AND BIOSTRATIGRAPHY OF EASTERN OREGON AND WESTERN IDAHO 57 

in the Trowbridge Shale and are probably of the same 

age. 

The Lonesome Formation, conformably above the 

Trowbridge Shale, is overlain unconformably by beds of 

early Late Cretaceous age (Imlay, 1981, p.11, fig. 6, table 

5). It attains a thickness of about 3,000 m and consists of 

hard, thin- to thick-bedded massive volcanic rocks and 

gray to green siltstone and claystone. Ammonites 

include Xenocephalites throughout the lower 2,000 m of 

the unit, Lilloettia 380 m above its base, and 

Pseudocadoceras throughout its upper 2,900 m. The 

presence of Pseudocadoceras shows that the Lonesome 

Formation is oflate early and middle Callovian age. The 

ammonite genera found in these Callovian sequences, 

Lilloettia, Kepplerites and Pseudocadoceras, represent 

the Boreal Realm. 

The early early Oxfordian ammonite Cardioceras 

(Scarburgiceras) is represented in the Pacific Coast 

region of the United States by five specimens from a 

locality on the east (Idaho) side of the Snake River near 

the southeast corner of Washington (Imlay, 1964, p. D7, 

D11, D15-D16, pl. 2, figs. 4-5). These specimens were 

collected from hard, black shale about 90 m above an 

angular unconformity at the top of a Triassic sequence 

that is more than 1,200 m thick (Morrison, 1961, p. 

105-110). This occurrence ofCardioceras is several hundred miles south of the nearest other known occurrence 

of that genus, in British Columbia. 

CONCLUSIONS 

Evidence of age furnished by ammonites shows that 

the most complete Jurassic stratigraphic sequence is in 

the Izee-Seneca area of the Izee terrane. A much less 

complete sequence occurs in the Suplee area a few miles 

to the west. Evidently the Suplee area was undergoing a 

period of nondeposition or erosion during most of the 

Early and Middle Jurassic, whereas in the Izee-Seneca 

area deposition was continuous throughout that time 

interval except during the early Pliensbachian and 

early Callovian. The Jurassic sequence in the Olds 

Ferry terrane is about the same age as the Izee-Seneca 

sequence except that rocks of Hettangian, late Bajocian, 

Bathonian, and late Callovian age have not been found. 

In contrast, the Jurassic section in the Wallowa terrane 

is limited chronologically to rocks of Sinemurian and 

Pliensbachian age in the Wallowa Mountains and rocks 

of late early Callovian and early Oxfordian ages in 

Snake River Canyon. 

REFERENCES 

Brooks, H.C., 1979, Geological map of the Huntington and part of the 

Olds Ferry quadrangles, Baker and Malheur counties, Oregon: 

Oregon Department of Geology and Mineral Mine Industries 

Geological Map Series Map GMS-13 

Dickinson, W.R., and Thayer, T.P., 1978, Paleogeographic and paleotectonic implications ofMesozoic stratigraphy and structure in the 

John Day Inlier of central Oregon: Pacific Section, Society of 

Economic Paleontologists and Mineralogists Pacific Coast Paleogeography Symposium, v. 2, p. 147-161 

Dickinson, W.R., and Vigrass, L.W., 1965, Geology of the Suplee-Izee 

area, Crook, Grant and Harney counties, Oregon: Oregon 

Department of Geology and Mineral Industries Bulletin 58, 109 

p. 

Hallam, Anthony, 1965, Observations on marine Lower Jurassic stratigraphy of North America, with special reference to United 

States: American Association of Petroleum Geologists Bulletin, 

v. 49, p.1485-1501. 

Imlay, R.W., 1961, Late Jurassic ammonites from the western Sierra 

Nevada California: U.S. Geological Survey Professional Paper 

374-D, 30 p. 

--1964, Upper Jurassic ammonites from eastern Oregon and 

western Idaho: U.S. Geological Survey Professional Paper 

483-D, p.1-21 

--1968, Lower Jurassic (Pliensbachian and Toarcian) ammonites 

from eastern Oregon and California: U.S. Geological Survey 

Professional Paper 593-C, p. C1-C51 

--1971, Jurassic ammonite succession in the United States, in 

Colloque du Jurassique (Luxembourg, 1967): Memoires du 

France, Bureau de Recherches Geologiques et Minieres, no. 75, 

p. 709-724 

--1973, Middle Jurassic (Bajocian) ammonites from eastern 

Oregon: U.S. Geological Survey Professional Paper 756, 100 p. 

--1980, Jurassic paleobiogeography of the conterminous United 

States in its continental setting: U.S. Geological Survey Professional Paper 1062, 134 p. 

--1981, Jurassic (Bathonian and Callovian) ammonites in eastern 

Oregon and western Idaho: U.S. Geological Survey Professional 

Paper 1142,24 p. 

Lupher, R.L., 1941, Jurassic stratigraphy of central Oregon: Geological 

Society of America Bulletin, v. 52, no. 2, p. 219-270 

Morrison, R.F., 1961, Angular unconformity marks Triassic-Jurassic 

boundary in Snake River area of northeastern Oregon: Ore Bin, 

v. 23, no.ll, p.105-111 

Muller, S.W., and Ferguson, H.G., 1939, Mesozoic stratigraphy of the 

Hawthorne and Tonopah quadrangles, Nevada: Geological 

Society of America Bulletin, v. 50, p. 1573-1624 

Smith, PL., 1980, Correlation of the members of the Jurassic Snowshoe Formation in the Izee basin of east-central Oregon: Canadian Journal of Earth Sciences, v. 17, no. 12, p. 1603-1608 

Smith, W.D., and Allen, J.E., 1941, Geology and physiography of the 

northern Wallowa Mountains, Oregon: Oregon Department of 

Geology and Mineral Industries Bulletin 12, 64 p. 

Wagner, N.S., Brooks, H.C., and Imlay, R.W., 1963, Marine Jurassic 

exposures in Juniper Mountain area of eastern Oregon: American Association of Petroleum Geologists Bulletin, v. 4 7, p. 

687-691 

6. CONODONT AGES FOR LIMESTONES OF EASTERN OREGON AND 

THEIR IMPLICATION FOR PRE-TERTIARY MELANGE TERRANES 

By ELLEN MuLLEN MoRRrs1 AND BRucE R. WARDLAW 

ABSTRACT 

Limestone blocks and strata within the Grindstone and Baker 

terranes of eastern Oregon have been sampled for conodonts. The 

conodont faunas yield ages from Devonian through Permian in each of 

these melange terranes. These ages generally agree with the range of 

ages obtained by other means. Results suggest that (1) Devonian rocks 

may be more widespread than previously thought, (2) division of the 

eastern Oregon melange belt into the Grindstone and Baker terranes 

appears artificial, and (3) lithologies and faunas support division of 

the melange into oceanic, arc, serpentinite-matrix, and ophiolite rock 

assemblages. Enclosure of Paleozoic limestones within Mesozoic 

cherts is a problem deserving further work. 

INTRODUCTION 

Conodont ages and distribution provide an additional parameter for understanding the complex and 

varied geology of the pre-Tertiary terranes of eastern 

Oregon. Ages, structure, and petrology in these terranes suggest either a prolonged history of accretion or 

the accumulation of a variety of rocks of different ages at 

the leading edge of an island arc. Radiometric dates 

range from Pennsylvanian to Early Jurassic (Walker, 

1983). Paleontologic ages are from the Middle Devonian 

to Late Jurassic, with significant absences of dates in 

the Early Mississippian, Late Pennsylvanian, and early 

Middle Triassic. 

REGIONAL OVERVIEW 

Sedimentary and volcanic rocks of Paleozoic and 

Mesozoic age form the dominant part of the accreted, arc 

related pre-Tertiary terranes of the Blue Mountains in 

eastern Oregon. Two arc-related terranes are generally 

recognized on the basis of lithologic and structural 

characteristics (Brooks, 1979; Dickinson, 1979; Mullen 

and Sarewitz, 1983). These accepted terranes (fig. 6.1) 

are the Seven Devils terrane and the Huntington arc 

terrane. The Permian and Late Triassic Seven Devils 

terrane includes basaltic to andesitic volcanic rocks, 

volcaniclastic rocks, and sedimentary rocks ranging 

from graywacke and conglomerate to tuffaceous silt1 Department of Geology, Sul Ross State University, Alpine, Texas 

stones. Upper Triassic (Norian) limestone (Martin 

Bridge Limestone) and Upper Triassic and Lower 

Jurassic fine-grained clastic sediments (lower part of 

the Hurwal Formation) unconformably overlie the 

Seven Devils rocks. The Huntington arc terrane is Late 

Triassic in age and dominantly composed of andesite, 

volcaniclastic breccia, and a variety of sedimentary 

rocks ranging from coarse conglomerates to siliceous 

siltstone. Small differences in age and lithology suggest 

that the Seven Devils and Huntington arc terranes 

could be separate terranes. 

Also present in the same region is a third terrane 

known as the central melange terrane (Dickinson, 1979) 

or the oceanic/melange terrane (Mullen and Sarewitz, 

1983), which is a seemingly chaotic mixture of large 

coherent blocks of oceanic chert and greenstone separated from coherent blocks of arc-derived sedimentary 

and volcanic rocks by serpentinite-matrix melange that 

includes clasts and knockers of chert, greenstone, barrositic amphibolite, and fragmented ophiolitic plutonic 

rocks. This melange terrane also includes two coherent 

ophiolitic or plutonic complexes: the Canyon Mountain 

complex and the Sparta complex. Geochemical and mineralogical data from greenstones and plutonic rocks 

suggest that the melange terrane represents a forearc 

which may have been coeval with the arc that formed the 

Seven Devils terrane (Mullen, 1985). Ages reported from 

the melange terrane are diverse. Fusulinids of Pennsylvanian through Late Permian age have been identified 

and represent a seemingly random distribution of Tethyan and North American faunas (Nestell, 1983). Radiolarians from cherts are commonly Permain or Late 

Triassic. Other paleontological ages based upon corals 

and brachiopods are Devonian (Kleweno and Jeffords, 

1962), Mississippian, and Permian (Vallier and others, 

1977). 

The diversity in ages and rock types within the 

melange terrane has led to the recent recognition of two 

possible subterranes (Grindstone and Baker) based 

largely upon data from oceanic cherts (Blome and others, 1983). Cherts of the Grindstone terrane in the south 

are dominantly Permian (Leonardian to Ochoan), but 

some contain Early Triassic conodonts. Cherts in the 

59 
60 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

118" 

. . . MESOZOIC FOREARC BASIN TERRANE ____ _ 

Ill 

OJ]J] 

~ 

~ 

.. 

HUNTINGTON ARC TERRANE 

SEVEN DEVILS TERRANE 

BAKER MELANGE TERRANE 

GRINDSTONE MELANGE TERRANE 

COHERENT OPHIOLITE 

0 

I 

0 

LLa 

·~ Grande 

I 25 

50 

I 

IDAHO 

100 KM 

I 

I 

50 MILES 

FIGURE 6.1.-Distribution of terranes and conodont and fusulinid faunas in central Oregon. D, Devonian; M, Mississippian; IP, Pennsylvanian; P, 

Permian; R, Triassic. 

Baker terrane to the north are of Late Triassic (Karnian 

to Norian) age and contain exotic Permian and Triassic 

limestone blocks. 

The fourth commonly recognized terrane, known as 

the forearc basin terrane (Brooks, 1979; Mullen and 

Sarewitz, 1983) is Late Triassic to Late Jurassic in age 

and unconformably overlies the melange terrane. It is 

composed of a thick clastic sequence dominated by sandstones and siltstones and incorporates rare basaltic to 

andesitic volcanic rocks. This sequence was deposited 

on the subsiding Permian and Triassic arc (Dickinson, 

1979). The forearc basin terrane correlates in age with 

the Triassic sequence that unconformably overlies the 

Seven Devils terrane, and it is equivalent to the Malheur terrane of Blome and others (1983), which includes 

Late Triassic radiolarian cherts. Clasts in conglomerate 

within the Malheur terrane contain Carboniferous radiolarians in chert (Blome and others, 1983) and Permian 

fusulinids in limestone (Nestell, 1983). 

CONODONTS OF THE MELANGE TERRANE 

Conodont ages for limestones and limestone blocks 

within the melange terrane range widely and have ages 

similar to that of other paleontologic data (fig. 6.2). 

Because of the tectonic mixture involved in melanges, 

paleontologic data will be considered separately for 

blocks of oceanic, arc, and serpentinite-matrix associations. Sample locations and terrane designations of 

limestone blocks yielding conodont and fusulinid faunas 

are shown on figure 6.1 
6. CONODONT AGES FOR LIMESTONES OF EASTERN OREGON 61 

GRINDSTONE TERRANE 

The faunas and floras of the Grindstone melange 

have been reasonably well documented (Merriam and 

Berthiaume, 1943; Dickinson and Thayer, 1978; Wardlaw and others, 1982) and are briefly discussed here. 

Arc-related assemblages. -Large blocks of limestone in the southern part of the melange terrane 

(Grindstone-Twelvemile melange of Dickinson and 

Thayer, 1978) have yielded abundant Devonian, Mississippian and Permian fossils, whereas cherts between 

limestone blocks have yielded Permian radiolarians and 

Early Triassic conodonts. Sandstone blocks containing 

minor limestone have yielded Pennsylvanian plants, 

conodonts, and fusulinids. The Permian fusulinid 

faunas in the limestone blocks have North American 

affinities. 

Oceanic related assemblages.-Permian fusulinids 

have been recovered from a limestone block near Dog 

Creek in the northern part of the melange terrane (Miller Mountain melange of Dickinson and Thayer, 1978). 

Adjacent cherts yield Late Triassic radiolarians and 

conodonts. The Permian fusulinid fauna shows Tethyan 

affinities. 

BAKER TERRANE 

Arc-related assemblages.-In the western area of 

the Baker melange (fig. 6.1) the southern part of the 

Greenhorn Mountains is comprised of arc-derived volcanic greenstones and lower greenschist-facies sedimentary rocks. The sedimentary rocks are siltstone, 

graywacke, and conglomerate that contain clasts of 

chert, andesitic and basaltic volcanic rocks, and some 

tuff. Greenstones have major-element, trace-element, 

and mineral compositions that indicate calc-alkaline 

island-arc affinities (Mullen, 1985). Limestone lenses, 

usually less than one meter thick, occur within the 

clastic sediments. These carbonate rocks are deformed 

and stretched parallel to the deformation of enclosing 

sedimentary rocks, and conodont color-alteration 

indices indicate metamorphism at 300-400 °C. 

A limestone which appears to be stratigraphically 

coherent and interbedded with clastic rocks in the 

drainage of Granite Boulder Creek yielded a diversified fauna including crinoids, bryozoans, corals, 

brachiopods, sponge spicules, and fish fragments. 

Fusulinids were identified as Pseudofusulinella and 

Schwagerina, of probably Early Permian (Wolfcampian) 

IZZ Z Z Z Z Zl 

-

MESOZOIC 

FOREARC 

BASIN 

TERRANE 

HUNTINGTON 

A RC TERRANE 

s EVEN DEVILS 

T ERRANE 

~ ~ 

-- ----

~ 

-

Devonian 

E I M I L 

Conodonts 

(limestone) 

-I 

rz:z:;j IZZZZZJ -- -- -- -- -------- --

-- - ~ ~ 

c:::::J 

~ E3 ~ 

~zzzzzzz 1 IZZZ2 

Mississip- Pennsy/-

pian Permian Triassic 

E I L 

II"~A 

Conodonts 

(chert) 

vanian 

ElM I L E 

v 777/J 

Fusulinids 

(limestone) 

I L Ej M I L 

I I 

Radiolarians 

(chert) 

8 

T 

--

AKER MELANGE 

ERRANE 

G RINDSTONE 

MELANGE 

T ERRANE 

Jurassic AGE E I M I 

Other fossils 

FIGURE 6.2.-Ages derived from various faunas and floras in the terranes (Dickinson, 1979) of central Oregon. 
62 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

age (D.W. Bostwick, oral commun., 1977) and North 

American affinities. Conodonts from the same locality 

are Neogondolella idahoensis and Neostreptognathodus 

sp., both of Early Permian (Leonardian) age. 

The rocks at the locality reported here are similar 

to the Coyote Butte Formation described by Wardlaw 

and others (1982). Both limestone bodies seem stratigraphically coherent and both contain a similar and 

diverse fossil assemblage. The disparity between conodont Leonardian and fusulinid Wolfcampian ages is 

present in both. The two localities are lithologically 

similar, except for the possibly finer grain size of the 

clastic sedimentary rocks in the Coyote Butte. It seems 

reasonable to correlate the limestones and clastic sedimentary rocks in the Greenhorns with the Coyote Butte 

Formation. 

Oceanic assemblages.-Large limestone pods occur 

in an assemblage with cherts and tholeiitic greenstones 

near the eastern extremity of the Baker terrane. Two 

conodont localities in these limestones are associated 

with the Burnt River Schist (greenstone), and a third is 

associated with siliceous sedimentary rocks that appear 

to be oceanic. 

Along the Burnt River, large pods of partly silicified, clay-rich dolomitic limestone occur within the 

Burnt River Schist. These rocks are deformed and 

recystallized, and the term "marble" is more appropriate than "limestone". The associated greenstones have 

major, trace-element and relict clinopyroxene compositions which indicate affinities to mid-ocean ridge 

tholeiites (Mullen, 1985). The limestones near French 

Spring appear to represent several boudinaged beds, 

although they may have been tectonically emplaced or 

possibly olistostromal. All units, greenstones and sedimentary rocks, are pervasively sheared, obliterating 

evidence for the mode of emplacement. The conodont 

Neogondolella navicula of Middle to Late Triassic age 

occurs in these limestones. Conodonts from the Nelson 

Marble at Durkee include N. navicula and Xaniognathus sp. of Middle to Late Triassic age. The extreme 

deformation of these rocks may be related to the nearby 

Connor Creek fault, a high-angle reverse fault (Brooks, 

1979), or thrust (Roure, 1982) of possible Jurassic age, 

which juxtaposes forearc basin sedimentary rocks 

against melange. 

Large pods (50 meters in diameter) of limestone 

occur in a small fenster of pre- Tertiary siliceous sedimentary rocks along the Snake River north of Brownlee, 

Oregon. The limestone is not strongly deformed, but the 

contact between limestone and enclosing sedimentary 

rocks is sheared. Crinoidal hash is the only faunal material visible. The conodont Neogondolella polygnathiformis of Late Triassic (Karnian) age was recovered from 

this limestone. 

The conodonts associated with these oceanic 

assemblages in the eastern-most part of the Baker 

melange are therefore all Triassic in age. Conodont and 

fusulinid faunas near Baker in the center of the melange 

terrane are Pennsylvanian and Permian in age (figure 

6.1); the fusulinid faunas show Tethyan affinities. 

Melange-related assemblages.-Serpentinitematrix melange (Ferns and Brooks, 1983), exposed along 

the crest of Vinegar Hill in the Greenhorn Mountains 

(Brooks and others, 1983) and extending northwestward 

toward Olive Lake, separates arc-derived rocks on the 

south from an ocean/alkalic block to the north. This 

melange contains cherts and siliceous sedimentary 

rocks, pillowed and non-pillowed greenstone, and plutonic ophiolitic fragments, including serpentinized 

harzburgite (Mullen, 1978). Limestone collected from 

Mullen's unit on the north side of Vinegar Hill contains 

strained Middle Pennsylvanian (Demoinesian) conodonts including Adetognathus sp., Gondolella sp., Idiognathodus sp., andNeognathodus sp. Metagabbro and 

pillowed greenstone underlie the sedimentary unit that 

contains the fossiliferous limestone (Brooks and others, 

1983). 

A second locality recently discovered by James 

Evans is north of Olive Lake. It is a limestone block in a 

large exposure of argillite and chert mapped by Evans 

as part of the Elkhorn Ridge Argillite along the same 

melange trend. Conodonts recovered from this limestone pod are Middle to Late Devonian Polygnathus sp. 

Devonian rocks have previously been reported in eastern Oregon from the Suplee area (Kleweno and Jeffords, 

1962; Savage and Amundson, 1979), 125 kilometers to 

the southwest along a trend roughly parallel to the 

possible trace of the subduction zone of the Triassic arc. 

Rocks adjacent to this melange on the north are probably oceanic. To the northwest, along the North Fork of 

the John Day River, the pre-Tertiary rocks are so 

strongly sheared that whether they are plutonic or volcanic is obscure even in thin section. Major- and traceelement geochemistry suggest that volcanic rocks in 

this deformed terrane have island-arc affinities. 

Limestone exposed southeast of Sumpter contains 

a North American Permian fusulinid fauna. We are 

unable, however, to place this occurrence in a rock 

assemblage. 

IMPLICATIONS OF CONODONT AGES AND 

DISTRIBUTION 

The first conclusion from the material presented 

above is that conodont ages corroborate dates obtained 

by other means throughout eastern Oregon. The 

restricted geographic distribution of conodont samples 

makes it undesirable to interpret the conodont data 

alone. However, the combination of conodont ages and 
6. CONODONT AGES FOR LIMESTONES OF EASTERN OREGON 63 

distributions with other geochronologies leads to the 

following suggestions: 

(1) Devonian rocks may be more abundant than 

previously considered. Limited exposures in the 

melange terrane make correlation with the Suplee 

occurrence difficult. The Devonian at Suplee appears to 

be a large, coherent block within melange. 

(2) The division of the melange terrane into the 

Grindstone and Baker terranes appears artificial. 

(3) Division of the melange terrane into arc-related 

and oceanic rock assemblages, serpentinite-matrix 

melange, and ophiolite complex seems more reasonable. 

These rock assemblages cut across the melange terrane 

boundaries. Arc- related assemblages contain Devonian 

through Early Triassic fossils with fusulinid faunas of 

North American affinities and cherts no younger than 

Early Triassic. Serpentinite- matrix melanges contain 

Devonian through Permian fossils and fusulinid faunas 

of both North American and Tethyan affinities. Oceanic 

assemblages contain Pennsylvanian through Late Triassic fossils with fusulinid faunas of Tethyan affinities 

and cherts commonly of Late Triassic age. The fusulinid 

faunas of North American affinities southeast of Sumpter may be an exception, but these rocks could also lie 

within a general northwest-trending zone of serpentinite-matrix melange. 

(4) The absence of upper Lower and Middle Triassic 

sedimentary rocks, and the enclosure of Paleozoic limestone within Mesozoic cherts are fundamental problems 

of eastern Oregon geology. A possible explanation for the 

"exotic" limestones is incorporation of a "docked" terrane into a forearc accretionary prism. However, this 

solution does not explain why only limestones seem to 

have anomalous ages, and why there appear to be no 

recognizable equivalent exotic blocks of other sedimentary lithologies. Another attractive explanation is that 

limestone blocks were shed from an uplifted, older arc 

edifice or platform and represent olistostromal deposits. 

We must caution that these conclusions are tentative and preliminary because of the complex nature of 

the problem, the sparsity of conodont data, and the 

rather poor exposures. We strongly encourage collection 

of more data. 

REFERENCES 

Blome, C.D., Jones, D.L., and Murchey, B.L., 1983, Paleogeographic 

implications of radiolarian-rich rocks from eastern Oregon 

[ abs.]: Geological Society of America Abstracts with Programs, v. 

15, p. 371. 

Brooks, H. C., 1979, Plate tectonics and the geologic history of the Blue 

Mountains: Oregon Geology, v. 41, p. 71-80. 

Brooks, H.C., Ferns, M.L., Wheeler, G.R., and Avery, D.G., 1983, 

Geology and gold deposits map of the northeast quarter of the 

Bates Quadrangle, Baker and Grant Counties, Oregon: Oregon 

Department of Geology and Mineral Industries Geological Map 

Series, 29. 

Dickinson, W.R. , 1979, Mesozoic forearc basin in central Oregon: 

Geology, v. 7, p. 166-180. 

Dickinson, WR., and Thayer, T.P. , 1978, Paleogeographic and paleotectonic implications of Mesozoic stratigraphy and structure in the 

John Day inlier of central Oregon, in Howell, D.G., and 

McDougall, K.A., eds., Mesozoic Paleogeography of the Western 

United States: Society of Economic Paleontologists and Mineralogists, Pacific Section, Pacific Coast Paleogeography Symposium2,p. 147-161. 

Ferns, M.L., and Brooks, H. C. , 1983, Serpentinite-matrix melanges in 

parts of the Blue Mountains of Northeast Oregon [abs.]: Geological Society of America Abstracts with Programs, v. 15, p. 371. 

Kleweno, WP., Jr., and Jeffords, R.M., 1962, Devonian rocks in the 

Suplee-lzee area of central Oregon: Geological Society of America Special Paper 68, 34 p. 

Merriam, C.W. , and Berthiaume, S.A., 1943, Late Paleozoic Formation 

of central Oregon: Geological Society of America Bulletin, v. 54, 

p.145-172. 

Mullen, E.D., 1978, Geology of the Greenhorn Mountains, northeastern Oregon: Corvallis, Oregon State University, M.S. thesis, 

372 p. 

--1985, Petrologic character of Permian and Triassic greenstones 

from the melange terrane of eastern Oregon and their implications for terrane origin: Geology, v. 13, p. 131-134. 

Mullen, E.D. , and Sarewitz, D.M., 1983, Paleozoic and Triassic terranes of the Blue Mountains, northeast Oregon. Discussion and 

field trip guide, Part I. A new consideration of old problems. 

Oregon Geology, v. 45, p. 65-68. 

N estell, M.K., 1983, Permian foraminiferal faunas of central and eastern Oregon [abs.]: Geological Society of America Abstracts with 

Programs, v. 15, p. 372. 

Roure, F. , 1982, Mise en evidence d'und tectonique majeur de Jurassique superieur dans le Nord-Est de l'Oregon (Secteur d'Huntingtonl [Evidence for major tectonism of the upper Jurassic in 

northeast Oregon]: Comptes Rendues Habdomadaires des 

Seances de l'Academie des Sciences de Paries, ser. 2, v. 294, p. 

291-925. 

Savage, N.M., and Amundson, C.T. , 1979, Middle Devonian (Givetian) 

conodonts from central Oregon: Journal of Paleontology, v. 53, p. 

1395-1400. 

Vallier, T.L., Brooks, H.C., and Thayer, T.P., 1977, Paleozoic rocks of 

eastern Oregon and western Idaho, in Steward, J.H., Stevens, 

C.H., and Fritsche, A.E., eds., Paleozoic Paleogeography of the 

Western United States: Society of Economic Paleontologists and 

Mineralogists, Pacific Section, Pacific Coast Paleogeography 

Symposium 1, p. 455-466. 

Walker, N.W., 1983, Pre-Tertiary tectonic evolution of northeastern 

Oregon and west-central Idaho: constraints based on U/Pb ages 

of zircons [abs.]: Geological Society of America Abstracts with 

Programs, v. 15, no. 5, p. 371. 

Wardlaw, B.R., Nestell, M.K., and Dutro, J.T., Jr., 1982, Biostratigraphy and structural setting of the Permian Coyote Butt Formation of Central Oregon: Geology, v. 10, p. 13-16. 

7. FAUNAL AFFINITIES AND TECTONOGENESIS OF MESOZOIC ROCKS 

IN THE BLUE MOUNTAINS PROVINCE OF EASTERN OREGON AND 

WESTERN IDAHO 

By EMILE A. PESSAGNO, JR.,1 and CHARLES D. BLOME 

ABSTRACT 

Paleontologic, paleomagnetic, petrologic, and stratigraphic data 

from the Blue Mountains province indicate that the Seven Devils 

terrane, the central melange terrane, the Mesozoic clastic terrane, 

and the Huntington arc terrane represent dismembered components 

of a single island-arc complex-referred to herein as the Blue Mountains island arc. Paleontologic evidence (specifically, the presence of 

Weyla Boehm in Lower Jurassic strata) suggests that this terrane 

originated in the eastern Pacific. Furthermore, it can be established 

from combined paleomagnetic and paleozoogeographic data that the 

terranes of the Blue Mountains were situated in the Central Tethyan 

Province, either north or south of the paleoequator, during the Late 

Triassic and Early Jurassic. 

Both ammonite and radiolarian data (presence of Parvicingula 

Pessagno and abundant, diversified pantanelliids) from the Mesozoic 

clastic terrane (John Day Inlier) indicate that by middle Toarcian time 

the Blue Mountains island arc was situated within the Northern 

Tethyan Province (approximately 15° to 30° north). Pantanelliid diversity and abundance decline during the late Bajocian and drop dramatically during the latest Bathonian and Callovian. The dramatic drop in 

pantanelliid diversity, together with the presence of Parvicingula and 

a preponderance of Boreal over Tethyan ammonites, indicate that 

during the latest Bathonian and Callovian this terrane was situated at 

higher latitudes, within the Southern Boreal Province of the Boreal 

Realm. Final displacement of the Blue Mountains island arc to even 

higher boreal latitudes (Late Jurassic paleolatitude, 40° ± north) 

probably occurred during the Late Jurassic. 

INTRODUCTION 

Much of the western part of the Cordilleran region 

of North America appears to be a collage of displaced 

terranes that have been accreted to the margin of the 

continental craton during Paleozoic and Mesozoic times. 

Many such geologic terranes have been displaced hundreds or perhaps even thousands of kilometers from 

their points of origin. 

The brilliant recognition of the first of these displaced terranes-the Wrangellia terrane-by Jones 

and others (1977) has revolutionized geological thinking 

pertaining to the evolution of the North American Cordillera, and indeed to the evolution of the entire circum1 University of Texas at Dallas, Richardson, TX. 

Pacific margin. Wrangellia is represented primarily by 

components in the Wrangell Mountains (Alaska), the 

Queen Charlotte Islands (British Columbia), part of 

Vancouver Island (British Columbia), and in Hells Canyon along the Idaho-Oregon border. In the first three of 

these areas the physical stratigraphy is remarkedly 

similar; however, the fourth area at Hells Canyon shows 

differences in its physical stratigraphy as well as in the 

composition of its volcanic rocks (see discussion of the 

Seven Devils terrane herein). Paleomagnetic data indicate that Wrangellia originated 15° north or south of the 

Triassic paleoequator, and both the Late Triassic and 

Early Jurassic megafossil assemblages are Tethyan in 

character (Jones and others, 1977; Tipper, 1981). 

Melange belts inherent to subduction complexes 

along the circum-Pacific margin show evidence of major 

displacement of blocks even smaller than terranes such 

as Wrangellia. For example, the Jurassic and Cretaceous red manganiferous ribbon cherts characteristic 

of the Franciscan Complex (California Coast Ranges), 

the Otter Point Formation (coastal southwestern 

Oregon), and the Pacific Rim complex (west coast of 

Vancouver Island, British Columbia) all contain radiolarian faunas that are distinctly Tethyan (dominantly 

Central Tethyan) in character and are similar to those 

described by Baumgartner and others (1980) from the 

Mediterranean region and by Tippit (1981) from Oman. 

On the other hand, adjacent blocks or slabs consisting of 

flyschoid sandstone and shale with Buchias or of green 

to black tuffaceous cherts with radiolarians represent 

Boreal strata. 

The tectonic complexity of the western Cordilleran 

region resulting from displaced terranes and displaced 

strata (nannoterranes in subduction complexes) is 

immense. It behooves paleontologists to consider the 

problems posed by this complexity in their zoogeographic reconstructions and in their attempts to 

compile meaningful zonal schemes. 

The purpose of the present report is to evaluate 

Triassic and Jurassic paleontologic data from the Blue 

Mountains province of east-central and northeastern 

Oregon and to determine, if possible, how these data 

65 
66 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

reflect the tectonic history of the region. Before Jones 

and others (1977) introduced their hypothesis of displaced terranes, most attempts to discuss the Mesozoic 

faunas of the circum-Pacific region were, at best, chaotic 

and usually ended in bizarre zoogeographic reconstructions. For example, Holder (1979, p. A391), who was 

apparently unaware of the displaced terrane hypothesis, described circum-Pacific Jurassic faunas as lacking 

faunistic uniformity. He even (p. A401) entitled a section 

of his chapter: "Faunal mosaic of the Pacific Ocean." 

ACKNOWLEDGMENTS 

We wish to thank Tracy L. Vallier (U.S. Geological 

Survey, Menlo Park, California) and Howard C. Brooks 

(Oregon Department of Geology and Mineral Industries) for reviewing the manuscript. Their suggestions 

were most helpful. However, the writers take full 

responsibility for the interpretations presented in the 

final version of the manuscript. Pessagno's work has 

been supported by grants from the National Science 

Foundation (EAR 76-22029; EAR 78-12934; EAR 

81-121550) and by funding from the Atlantic Richfield 

Company, Exxon Production Research Company, and 

the Mobil Oil Corporation. We wish to thank Tod Six 

(University of Texas, Dallas) for preparing some of the 

illustrations. 

THE TETHYAN AND BOREAL FAUNAL REALMS 

DURING THE LATE TRIASSIC AND JURASSIC 

As noted by Gordon (1974, p. 139), the decline in 

mean temperature from the equator to the poles is one of 

the most important determinants of biogeographic distribution (see also Fischer, 1960). Planktonic foraminifers in modern oceans, for example, show a 

marked decrease in diversity from equatorial latitudes 

to the Arctic (see Loeblich and others, 1964, p. C126-

C127). Furthermore, it can be established that certain 

taxa such as Globigerina pachyderma (Ehrenberg) are 

cold-water (Arctic- subarctic) indicators whereas others, 

such as Sphaeroidinella dehiscens (Parker and Jones), 

are warm-water (equatorial) indicators. 

Gordon (1974, p.143), in his excellent report dealing 

with the distribution of the marine biota during the 

Jurassic, stated: 

Working in association with density variations such as occur in modern seas, the planetary wind system under the influence of a rotating 

earth would have produced a system of ocean currents which also 

would have had similarities with the modern system. Equatorial currents ancestral to those of modern time must have existed, but during 

most if not all of the Jurassic they would have formed a world-encircling girdle across the central Pacific Ocean and through the Tethys 

Sea. Within the equatorial west-bound flow an east-bound counter 

current would have existed just as it does today. In each hemisphere 

the coriolis force would have induced current gyres and at high latitudes a West Wind Drift would have existed as it does today in the 

Antarctic Ocean. 

Gordon's model for the oceanic surface currents of 

the Oxfordian (Late Jurassic) is shown in figure 7.1. It is 

apparent that if this model is correct, most ofthe western margin of Late Jurassic cratonic North America 

would be under the influence of a cold-water "paleoCalifornia" current. Stratigraphic studies in east-central Mexico (Cantu Chapa, 1971; Imlay, 1980; Longoria 

and Pessagno, unpub. data) indicate that the Gulf of 

Mexico opened in late Bathonian (Middle Jurassic) time. 

From that time onward during the Jurassic, a direct 

connection existed between the Pacific, Atlantic, and 

Mediterranean. Hence, it is inferred that the Gordon 

model can be applied through the interval from late 

Bathonian to late Tithonian times. It is likely that the 

current circulation in the Early and Middle Jurassic 

Pacific was more similar to modern Pacific circulation 

than even that in the Late Jurassic. 

There is little question that a climatic zonation 

and latitudinal temperature gradient existed 

throughout Jurassic time. This is substantiated by both 

the floral and faunal records (for example, see Gordon, 

197 4). The Tethyan Realm corresponds to the tropical 

and subtropical climatic belts in both the Northern and 

Southern Hemispheres, whereas the Boreal Realm corresponds to the temperate belt in the Northern Hemisphere. The temperature rather than Arctic nature of 

the Boreal Realm during the Jurassic is indicated by the 

presence of temperate to warm-temperature conifers at 

high latitudes (Axelrod, 1963, p. 3258). 

In this report, we rely on the global tectonic reconstructions of Smith and others (1981) to interpret the 

paleolatitudinal positions of boundries between the 

Tethyan and Boreal Realms. These reconstructions are 

regarded as being more accurate than others such as 

those of Irving (1979) because they are consistent with 

the faunal data. Whereas the paleolatitudinal lines on 

the maps of Smith and others generally parallel faunalrealm boundries, those of Irving for North America are 

positioned obliquely to such boundries. Finally, one 

must keep in mind that during Triassic to Late Jurassic 

time cratonic North America moved in a northwesterly 

direction away from the paleoequator. Hence the boundary between the Tethyan and Boreal Faunal Realms 

shifted progressively southward. 

In the following discussion of Triassic and Jurassic 

megafossil data, we regard most circum-Pacific occurrences of ammonoids, pelecypods, and gastropods as 

suspect, particularly where faunal associations or paleomagnetic data are either unknown or not cited. If the 
7. FAUNAL AFFINITIES AND TECTONOGENESIS OF MESOZOIC ROCKS 67 

displaced-terrane hypothesis is valid for the circumPacific region, Tethyan faunas conceivably could occur as 

far north as Alaska and as far south as Tierra del Fuego. 

To interpret the faunal data, we utilize megafossil occurrences from terranes which have not been greatly displaced latitudinally (for example, the western interior of 

North America and the Mediterranean area). 

Figure 7.2 shows faunal criteria for separating the 

Tethyan and Boreal Realms during the Middle and Late 

~Jurassic. It is now apparent from our studies of the 

North American radiolarian assemblages, as well as 

radiolarian studies from other regions (for example, 

Baumgartner and others, 1980), that we can distinguish 

Tethyan from Boreal radiolarian faunas. Furthermore, 

it is apparent that at least in the late Early, Middle, and 

Late Jurassic we can subdivide the Tethyan Realm into 

a Central Tethyan Province and a Northern Tethyan 

Province (fig. 7.2). The Central Tethyan Province is 

characterized by a parvicingulid assemblage that lacks 

Parvicingula Pessagno (sensu Pessagno and 1JVhalen, 

1982) but contains Ristola Pessagno and 'A'halen. The 

Northern Tethyan Province and the Southern Boreal 

Province possess a parvicingulid assemblage containing 

both taxa; however, Parvicingula is the dominant element in the southern boreal assemblage. In addition, 

pantanellid diversity remains high throughout the 

Tethyan Realm, but declines dramatically in the Boreal 

~ 

~ ---~ 

~ 

-- - ~ 

~ 

~ 

(. 

Realm (Southern Boreal Province). Figure 7.3 shows 

faunal-realm and province indicators for the Middle and 

Late Jurassic; it is based on both megafossil and microfossil data. Utilizing the paleolatitudinal reconstructions of Smith and others (1981) and the faunal data, we 

place the boundary between the Boreal and Tethyan 

Faunal Realms at approximately 30° north both in 

Europe and in cratonic North America. Furthermore, 

using these reconstructions and integrated paleomagnetic and radiolarian data from California (McWilliams 

and Howell, 1982; Pessagno and Blome, unpub. data), we 

place the northern and southern limits of our Central 

Tethyan Province at approximately 22° north and south 

of the Middle and Late Jurassic paleoequator. There is 

little question that a direct integration of the radiolarian faunal data with the paleomagnetic data will 

allow a much more accurate delimitation of faunalrealm and province boundaries in the near future. 

MESOZOIC TECTONOSTRATIGRAPHY AND 

ZOOGEOGRAPHY OF THE BLUE MOUNTAINS 

PROVINCE 

Dickinson (1979) divided the Blue Mountains 

Province into four major tectonostratigraphic terranes 

that crop out discontinuously from beneath a cover of 

Cenozoic volcanic rocks in northeast-trending belts. 

--- ---

~ 

---

--- -=-- ---- ( ( 

FIGURE 7.1.-Inferred ocean surface currents during Oxfordian times (from Gordon, 1974, fig. 4). This model can be applied to the entire late 

Bathonian to late Tithonian interval. Stratigraphic evidence from east-central Mexico indicates that the Gulf of Mexico opened up during 

the late Bathonian (Longoria, 1984). Continental areas (outlines dashed where poorly known): M= Mrica; lrn = Antarctica; As= Asia; 

Au = Australia; I= India; M =Madagascar; NA =North America; SA= South America. 
68 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

From north to south, these terranes are the Seven Devils terrane, the central melange terrane, the Mesozoic 

clastic terrane, and the Huntington arc terrane (Dickinson, 1979; see fig. 7.4). 

CENTRAL NORTHERN 

TETHYAN PROVINCE TETHYAN PROVINCE J 

TETHYAN REALM (PART) t 

A 

~ 

~~--~ I 

Q 

! 

SOUTHERN NORTHERN 

BOREAL PROVINCE BOREAL PROVINCE 

BOREAL REALM (PART) 

~~~~~~~~~~~~~~ A. TETHYAN PROVINCE TETHYAN PROVINCE BOREAL PROVINCE BOREAL PROVINCE 

TETHYAN REALM (PART> BOREAL REALM (PARTl 

H 

FIGURE 7.2.-Latitudinal variations during the Middle and Late 

Jurassic in the diversity and abundance of A, pantanelliid radiolarians and B, Parvicingula Pessagno (sensu Pessagno and 

Whalen, 1982) and Ristola Pessagno and Whalen. Notes on data 

used: 0, data from Alaska [North Slope, Brooks Range 

(unpublished data) and Puale Bay areas]. At Puale Bay Blome 

(1984b) recovered well-preserved middle Callovian radiolarians 

from the same horizon as Stenocadoceras Imlay, a high-latitude 

Boreal ammonite taxon that elsewhere occurs in Russia and 

Greenland. 1, Data from about the upper half of volcanogenic 

successions overlying the Coast Range ophiolite, from the overlying Great Valley sequence (California Coast Ranges), and from 

the Galice Formation, Klamath Mountains, California. 2, Data 

from the Taman and Pimienta Formations of east-central Mexico, 

where radiolarian faunas are associated with Tethyan 

ammonites, pecten (Aulacomyella Furlani), calpionellids, and 

nannoconids. 3, Data from the Mediterranean area, Turkey, Iran, 

Oman, Tibet, and various Deep Sea Drilling Project legs. No 

Central Tethyan faunas are known from North America except 

from displaced terranes and subduction complexes (for instance, 

Franciscan Complex, California; Pacific Rim Complex, Vancouver 

Island, British Columbia). 4, No data from southern hemisphere. 

Our model assumes symmetrical arrangement of faunal 

provinces and realms north and south of the paleoequator. Boundary between Central and Northern Tethyan Provinces placed at 

about 22° N. and that between Tethyan and Boreal Realms at 

about 30° N. (see text). 

SEVEN DEVILS TERRANE 

Jones and others (1977) tentatively treated the 

Seven Devils terrane as part of Wrangellia. The same 

position was maintained by Hillhouse and others, 1982). 

However, Sarewitz (1983, p. 634-637) noted major differences in the physical stratigraphy and composition of 

the Seven Devils and Wrangellian rocks. Sarewitz correctly noted that the Triassic volcanic rocks of the Seven 

Devils terrane are representative of a volcanic arc of 

probable calc-alkaline affinity, whereas coeval rocks in 

Wrangellia (sensu stricto) consist of a thick pile of 

tholeiitic basalts, subaerial basalt flows, and breccias. 

The tholeiitic character of the basalt in the Karmutsen 

Formation of Wrangellia was well documented, for 

example, in the Queen Charlotte Islands by Sutherland 

Brown (1968, p. 46-4 7) and at Vancouver Island by Carlisle and Susuki (1974). 

In spite of such ditlerences there is little question 

that the Seven Devils terrane, like Wrangellia proper, 

was displaced from low latitudes during Triassic and 

Jurassic times. Paleomagnetic data presented by Hillhouse and others (1982) in icate that the Seven Devils 

terrane originated 18° ( ±4°) north or south of the Triassic paleoequator. In addition, Jones and others (1977, 

p. 2520) found that the upper part of the Martin Bridge 

Limestone (Vallier, 1977) (Late Triassic: early Norian; 

Hells Canyon and Wallowa Mountains, Oregon) possesses a highly diversified invertebrate fauna of Tethyan 

affinities. These workers noted further that in its overall composition this fauna closely resembles that of the 

same age from the transition beds between the 

Chitistone Limestone and Nizina Limestone in the 

Wrangell Mountains of Alaska. 

The rocks of the Seven Devils terrane range in age 

from Early Permian to Late Jurassic (early Oxfordian). 

A volcanic arc assemblage is represented by the Seven 

Devils Group of Early Permian and Middle and Late 

Triassic (late Ladinian and Karnian) age (see Vallier, 

1977; Brooks and Vallier, 1978; Sarewitz, 1983). The 

Seven Devils Group is overlain by the massive, neritic, 

early Norian (Late Triassic) Martin Bridge Limestone, 

which is in turn overlain by the bathyal (?) "argillite" 

(=siliceous mudstone) and limestone of the Hurwal 

Formation (Late Triassic and Early Jurassic: Norian 

and late Pliensbachian). It should be noted, however, 

that only the part of the succession that includes the 

Martin Bridge Limestone and the Hurwal Formation 

resembles that of Wrangellia proper. The Martin Bridge 

Limestone resembles the lower gray limestone member 

of the Kunga Formation in the Queen Charlotte Islands. 

The Hurwal Formation is somewhat similar to the 

bathyal strata of the middle black limestone member 
en 

z 

I( 

; 

I( 

~ 

0 

Ci 

I( 

a: 

tJ 

;; 

en 

I( 

a: 

= w 

... 

I( 

~ 

~ 

z 

I( 

w 

~ 

~ 

~ 

i 

til 

w 

> 

~ 

I( 

> ; 

.~ . 

• .. 

.2 ? 

• 4 

~ 

til 

w ~ 

... 

i 

0 

:£ 

:£ 

I( .~ 

:: 

= 

~ 

• :; 

'1:1 

i 

7. FAUNAL AFFINITIES AND TECTONOGENESIS OF MESOZOIC ROCKS 

TETHYAN FAUNAL REALM BOREAL FAUNAL REALM 

SOUTHERN 

TETHYAN 

PROVINCE 

CENTRAL TETHYAN PROVINCE 

NORTHERN 

TETHYAN 

PROVINCE 

SOUTHERN 

BOREAL 

PROVINCE 

NORTHERN BOREAL PROVINCE 

Mirilusus Peaaaqno I ? ~-....;.;,,;.;.;.;,,;;,;.;;,;,..;....;.;,~;....----------r-----? i Parvicingu~a Pessa.gno 

lr-----~~~~~~--~------~~----------------------? 

Ristola Peasaqno and Whalen • ? 

? .~--~~~~~~~~~~~--~------------~~~------------~----- . 

? Hsuum Pessaqno 

. ? _______ Pe_r_i~sp~y-r-id_i_u~m~D-u_m_,,_.,_c•------~------------~--------1 

~ 

~ Turanta Pessaqno 4nd Blon.e 

? ~~----N-a~p-o-ra __ P_•_•_••~q-no------------r-------------.----------------------? . ? ______ .;,;H.;,;>l~a.;,;r i.;."'.;.'e.;.;x.;._T_•_k.;.;em ... u;.;,r.;.a _• n-d--N •_k_•_••-k"'lo ,...------------. ? 

Pantanellium Peuaqno 1 ! . ? !~-------~----~-------~------~ Trillus Pessaono .tnd Blome 

? I • 

? ______ .;.z.;.ar ... t.;.u_s __ Pe_•_••~q~n-o_•_nd __ B_lo_m_•----~-------------11 I I 

Emduvta Foreman 

? ~~--~~~;....~~;....----~--------~---------~--­ Tripocyclia Ha.eckel 

? ~---~~~"'--------~----------~--------~--­ Acanthocircus dicranocanthus 1

Squ•nabol i 

? ~---------------------------r,~----------~ ? P---~P.;.o.;.d.;.o.;.c~ap~s.;.a~a.;.m~p ... h.;.i.;.tr.;.e~p.;.te.;.r.;.a __ F.;.o.;.re~m.;.•.;.n __________ ~------------~ 

•Eucyrtidium" ptyctum Rtedel and S4nfdtppo 

? ~;-----~~----~~~~----... =~--~~----~:~----------~ 

i 

i Buchia Roudlae-r 

Aulacomyella Furlant 

?----.---------------------------~------------. ~ 

! 

? ! Kossmalia Uhliq 

• I 

Glochiceras Hyatt 

Idoceras Burckhardt 

! 

I 

i 

i 

Reineclr.eia Bayle 

Grossouvria Siemtradz.ki 

Stephanoceras Waaqen 

Sonn1n1a Sayle 

Calpionellids 

i 

i 

I 

I 

i 

i 

i 

i 

: 

I 

~ L 

i 

i 

i 

Amoebites uckman 

Card1oceras Neumdyr dnd Uh !J q 

. Scarburglcerds Buckmc1n 

Stenocadoceras Im l ay 

I 

Kepplerites Neumayr and Uhl1g 

Cranocephal1tes Spd th 

Ldloet1a C r1ckmdy 

. 

Arkellocera~ Frebold 

Normann1tes MunLO?r ·C halmcss 

?--~~~~--------~--------~ 

?----T-m~e ... to ~rd.;.;s __ ck_m_•_"----.-------------~ ? 

i 

! 

i 

! 

I 

i 

I 

i 

i 

! 

FIGURE 7.3.-Faunal realm and province indicators for the Middle and Late Jurassic. Distribution of selected taxa of 

radiolarians, other microfossils, and megafossils among the provinces of the Tethyan and Boreal Realms. Boundaries 

defined as in figure 7.2. 

69 
70 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

(Karnian and late Norian) and the upper thinly bedded 

argillite member (Hettangian and Sinemurian) of the 

Kunga Formation as well as the overlying Maude Formation (late Sinemurian to Toarcian) (see Sutherland 

Brown, 1968; Pessagno and Blome , 1980, 1982 ; 

Pessagno and Whalen, 1982). Finally, it should be noted 

that Imlay (1968, p. C21) indicated that the late 

Pliensbachian ammonite assemblage of the Hurwal Formation, like that of the Nicely Formation (Suplee-Izee 

area; see discussion of the Mesozoic clastic terrane 

herein) shows strong Mediterranean (Tethyan) 

affinities. 

The Seven Devils Group is overlain with marked 

angular unconformity by the Coon Hollow Formation 

(Morrison, 1961, 1964). The Coon Hollow Formation consists of about 600 m of dark gray mudstone, impure 

limestone, and occasional limestone concretions in the 

mudstone. It is exposed along Hells Canyon just south of 

the Oregon-Washington border near Cottonwood Creek 

and also somewhat farther south near Pittsburg Landing. At both the Cottonwood Creek and Pittsburg Landing localities the base of the Coon Hollow is marked by a 

conglomerate which includes clasts derived from the 

underlying Seven Devils Group (Vallier and Hooper, 

1976). The Coon Hollow Formation appears to be genetically related to similar flyschoid strata (for example, 

SDT 

~ SEVEN 

DEVILS 

TERRA NE 

0 

· Snoke 

/River 

WASH. 

-·oR~

100 

KILOMETERS 

CMT 

!>> :n:r::=l CE NTRAL MELANGE 

TERRANE 

MCT 

1:.·'· ~:.: . .-:·-:·:·::·j MESOZOIC 

CLASTIC 

TERRANE 

HAT 

HUNTINGTON 

~ 

ARC TERRANE 

FIGURE 7.4.- Geologic terranes in the Blue Mountains province (from 

Dickinson, 1979). 

the Lonesome Formation) exposed near lzee in the 

Mesozoic clastic terrane to the south. 

At the southern locality near Pittsburg Landing on 

the Oregon side of Hells Canyon, Imlay (1981, p. 12) 

recovered early Callovian ammonites from the Coon 

Hollow Formation. These include Lilloettia stantoni 

Imlay, Xenocephalites vicarius Imlay, and Grossouvria 

sp. The genusLilloettia Crickmay appears to be a Boreal 

eastern Pacific taxon. It is known from Oregon (Imlay, 

1981), from the Canadian Rocky Mountains (Fernie 

Shale, British Columbia; Hall and Stronach, 1982), and 

from Alaska (Imlay, 1981). Xenocephalites Spath, except 

for its occurrence in Greenland, is predominantly an 

eastern Pacific taxon. It is known from South America, 

Mexico, and northern and southern Alaska (Holder, 

1979, p. A402). Grossouvria Siemradzki is predominantly a Tethyan form (see Arkell and others, 1957, p. 

L319). However, Imlay (1961, p. D6) noted Grossouvria in 

association with the Boreal ammonite Kepplerites Neumayr and Uhlig in the Colfax Formation, Placer County, 

California. The association of these ammonite taxa in 

the lower Callovian part of the Coon Hollow Formation 

suggests that these strata were deposited within the 

Southern Boreal Province of the Boreal Faunal Realm 

(fig. 7.3). 

At the northern locality near Cottonwood Creek, 

Imlay (1964, p. D6) recorded early Oxfordian ammonites 

assignable to Cardioceras (Scarburgiceras) martini 

Reeside from strata (USGS Loc. 28652) occurring about 

120 m above the base of the Coon Hollow Formation. In 

Europe and in tectonically more stable portions of 

North America (for example, the Western Interior Seaway) both Cardioceras Neumayr and Uhlig and its subgenus Scarburgiceras Buckman are indicative of the 

Boreal Faunal Realm (see Imlay, 1980, p. 24-25, fig. 15). 

In North America both taxa are known only from Wyoming northward to the Canadian Arctic; Upper Jurassic 

marine strata are generally lacking farther south in the 

western interior. In northwest Europe these taxa occur 

as far south as the Paris Basin (see Enay and others, 

1971). Cardioceras is also known from Poland, European 

Russia, Siberia, and Greenland (see Arkell and others, 

1957, p. L306); Scarburgiceras is known from European 

Russia. 

The data from the Seven Devils terrane indicate 

that (1) the Seven Devils terrane originated 18° ( ± 4°) 

north or south of the Triassic paleoequator within the 

Tethyan Faunal Realm, and by Early Jurassic (late 

Pliensbachian) time it was situated at relatively low 

latitudes still within the limits of the Central Tethyan 

Province of the Tethyan Faunal Realm (figs. 7.2 and 7.3); 

(2) the Tethyan strata of the Seven Devils terrane were 

first deformed (in a local orogenic pulse characteristic of 

island-arc complexes such as the Greater Antilles) 
7. FAUNAL AFFINITIES AND TECTONOGENESIS OF MESOZOIC ROCKS 71 

between Early Jurassic (late Pliensbachian) and Middle 

Jurassic (early Callovian) time; (3) by Callovian and 

Oxfordian (Late Jurassic) time, the Seven Devils block, 

then covered unconformably by the Coon Hollow Forma;. 

tion, was situated at boreal latitudes within the Southern Boreal Province (fig. 7.3); and (4) the strata of the 

Seven Devils terrane (including the Coon Hollow Formation) were deformed in post-early Oxfordian (Late 

Jurassic) time (see Vallier and Hooper, 7 1976; Vallier, 

1977). 

CENTRAL MELANGE TERRANE 

The central melange terrane consists of disrupted 

late Paleozoic oceanic crustal blocks such as the 

ophiolitic Canyon Mountain Complex, as well as associated deep-marine sedimentary strata (Elkhorn Ridge 

Argillite) of late Paleozoic and Triassic (and possibly 

Early Jurassic) age. Extensive bodies of highly 

deformed but lithologically coherent metamorphic and 

sedimentary rocks, such as the Burnt River Schist and 

Nelson Marble, are also present (Brooks and Vallier, 

1978). It was originally believed by Dickinson and other 

workers that the rocks of the central melange terrane 

ranged in age from Middle Devonian to Middle Triassic 

(Ladinian). Subsequent investigations have established 

that younger rocks are also present. 

Nestell and MacLeod (personal commun., 1984) 

recently recovered Late Triassic (late Karnian ?; early to 

late middle Norian) radiolarians assignable to the Capnodoce Zone (Pessagno and others, 1979; Blome, 1984a) 

from the melange belt east of John Day. This radiolarian 

assemblage is identical to those from the Rail Cabin 

Mudstone Member of the Vester Formation (Blome and 

others, this volume) ( Capnodoce Zone, Xipha striata 

Subzone to Latium paucum Subzone; Blome, 1984). 

Directly northwest from the town of John Day 

across Little Dog Creek, chert samples (P-1, P-3) 

collected by Merlyn Nestell (University of Texas, 

Arlington) contained a younger fauna of latest Triassic 

(latest Norian) or possibly Early Jurassic (Hettangian) 

age (see Blome and others, this volume). 

The Middle Triassic (late Ladinian) radiolarian 

assemblage (originally called Jurassic) recovered by 

Jones, Pessagno, and Force (1976) from the Miller Mountain melange area near Vance Creek south of John Day 

bears strong resemblance to radiolarian assemblages 

figured by Kozur and Mostler (1981) from the Austrian 

Alps and to assemblages examined from Italy. Other 

black chert samples (OR 68-71; Blome, 1984a) collected 

from the same locality also contained similar age Middle Triassic (late Ladinian) or Late Triassic (early Karnian) radiolarians. This radiolarian fauna is interpreted to be of early Karnian age based on the presence 

of Gorgansium Pessagno and Blome (1980), which 

makes its first appearance in the Karnian. 

The eastern part of the central melange terrane is 

characterized by ophiolite fragments, chert, argillite, 

siliceous tuff, and rare coarse-grained sedimentary 

rocks. Most of the eastern part of this terrane has undergone low-grade metamorphism (greenschist facies), and 

in many areas it includes structurally intermixed plutonic masses. 

West of the town of Baker, chert collected by the 

junior author (see Blome and others, this volume) contained Middle Permian (Guadalupian) radiolarian 

faunas nearly identical in age and faunal composition to 

those collected in the southwestern part of the melange 

terrane near Grindstone Creek. Permian fusulinids 

from limestones near Suplee were also noted by Dickinson and Vigrass (1965 ). These workers and also Merriam 

and Berthiaume (1943) noted that the fusulinid limestones are correlative with limestones in part of the 

Elkhorn Ridge Argillite in the northeastern part of the 

central melange terrane (Taubeneck, 1955). According to 

Wardlaw and others (1982), a chert sample collected 

near Coyote Butte (southwestern part of the central 

melange terrane) contained Early Triassic (Scythian) 

conodonts and radiolarians. Metacherts collected from 

the Elkhorn Ridge Argillite east of Baker yielded poorly 

preserved radiolarian assemblages of both middle Permian (Guadalupian) and Late Triassic (early to middle 

Norian) ages. The Triassic assemblage included in these 

strata is assignable to the Xipha striata to Latium 

paucum Subzones of the Capnodoce Zone (Blome, 

1984a). The radiolarians collected thus far from the 

Elkhorn Ridge Argillite indicates that the unit is equivalent in age to the Fields Creek Formation and all but 

the lower 5 m of the Rail Cabin Mudstone Member of the 

Vester Formation (Mesozoic clastic terrane). 

A sample (BD 816) from the Elkhorn Ridge Argillite 

submitted to the senior author by Robert I. Coward 

(Department of Geology, Rice University) was found to 

contain Canoptum sp. and Canoptum anulatum 

Pessagno and Poisson (?). Investigations by Pessagno 

and Whalen (1982) and by Whalen (unpub. data) indicate that members of the Canoptum anulatum group 

first appear in highest upper Norian strata in western 

North America and occur throughout the Lower 

Jurassic (Hettangian to Toarcian). Canoptum anulatum 

s.s. is restricted to the upper Pliensbachian and Toarcian. 

It is tempting to postulate a genetic relationship 

between the Seven Devils terrane and the central 

melange terrane and to suggest that the two have been 

associated as part of the same island arc. 

Insofar as is known, no paleomagnetic data have 

been obtained from the central melange terrane. 
72 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

However, Dickinson (1979, p. 166) and Bostwick and 

Nestell (1967) indicated that both Tethyan and American fusulinid faunas occur in separate pods in both the 

eastern and western parts of the melange belt. As 

already noted, the Middle Triassic radiolarians from 

cherts near Vance Creek south of John Day are very 

similar to those figured by Kozur and Mostler (1981) 

from the Austrian Alps. The Late Triassic radiolarian 

assemblage is very similar to that of the Brisbois and 

Rail Cabin Members of the Vester Formation and hence 

may likewise be Tethyan (see following discussion on the 

Mesozoic clastic terrane). 

MESOZOIC CLASTIC TERRANE 

The Mesozoic clastic terrane consists of rocks of 

Late Triassic (late Karnian) to Middle Jurassic (middle 

Callovian) age. It lies between the central melange terrane and Seven Devils terrane to the north and the 

Huntington arc terrane to the south. As noted previously, the Coon Hollow Formation (early Callovian to 

early Oxfordian), which overlies the Triassic Seven 

Devils Group with angular unconformity, appears to be 

genetically related to strata in the Mesozoic clastic terrane (for example, the Lonesome Formation). Furthermore, the Weatherby Formation, which unconformably 

overlies the Huntington arc terrane to the southeast, 

appears to be an extension of the Mesozoic clastic terrane (Brooks and Vallier, 1978). 

The Mesozoic clastic terrane consists mainly of a 

somewhat flysch-like volcaniclastic succession, together 

with spilitic basalt and andesite flows of Late Triassic 

age (Karnian and late middle Norian; for example, Begg 

Member of the Vester Formation and Fields Creek Formation), rare andesite flows of Early Jurassic age (in the 

late Pliensbachian Nicely Formation), andesitic tuff 

breccias and andesitic flows of Middle Jurassic age 

(Bajocian; Basey Member of the Snowshoe Formation), 

and tuffs of the Middle Jurassic (Callovian) Trowbridge 

Formation (see Dickinson and Vigrass, 1965). 

Unfortunately, no detailed paleomagnetic data are 

yet available for the rocks of the Mesozoic clastic terrane. However, abundant paleontologic data (Imlay, 

1964, 1968, 1973, 1981; Pessagno and Blome, 1980, 1982; 

Pessagno and Whalen, 1982; Blome, 1983, 1984a,b) from 

the Suplee-Izee area of Dickinson and Vigrass (1965) 

and from surrounding areas suggest that this terrane, 

like the Seven Devils terrane to the north and the Huntington arc terrane to the south, originated at low latitudes within the Tethyan Faunal Realm and gradually 

moved northward to boreal latitudes during Late Triassic, Early Jurassic, and Middle Jurassic times. 

SYNTHESIS OF PALEONTOLOGICAL DATA IN 

THE. SUPLEE-IZEE AREA AND IN 

SURROUNDING AREAS 

Late Triassic (late Karnian) ammonites recorded by 

Dickinson and Vigrass (1965, table 4) from the Brisbois 

Member of the Vester Formation includeArcestes Suess, 

Discotropites Hyatt and Smith, Gymnotropites Hyatt 

and Smith, Homerites Mojsisovics, Juvavites 

Mojsisovics, Parahauerites Diener, Paratropites 

Mojsisovics, and Tropites Mojsisovics. Using the distribution of data presented by Arkell and others (1957), 

Arcestes is seen to be cosmopolitan, whereas Gymnotropites and Parahauerites are known only from California and are hence suspected to be allochthonous. 

The remaining taxa occur throughout the Alpine-Himalayan belt and can be regarded as Tethyan, probably 

Central Tethyan. 

The radiolarian assemblage from the Rail Cabin 

Mudstone Member (late Karnian?, early to late middle 

Norian) is diverse (see Pessagno and Blome, 1980; 

Blome, 1983, 1984a). Particularly noticeable in the Rail 

Cabin assemblage are the abundance and diversity of 

members of the family Pantanellidae. Pantanelliid diversity is, in part, overprinted by a period of adaptive 

radiation during the Late Triassic which gave rise to a 

variety of bizarre forms such as Capnodoce De Wever, 

Loffa Pessagno, and Renzium Blome among the Capnodocinae; longer ranging genera such as Gorgansium 

Pessagno and Blome include a relatively large number 

of species-level taxa (named and unnamed). Investigations by the writers over the past seven years indicate 

that diverse pantanelliid assemblages are characteristic of the Tethyan Faunal Realm. During the Late 

Jurassic, pantanelliid diversity and abundance decline 

drastically from the Northern Tethyan Province to the 

Southern Boreal Province (fig. 7.2). 

In the overlying Lower Jurassic formational units, 

the megafossils, where they are abundant enough to be 

significant (for example, in the Suplee and Nicely Formations), are likewise Tethyan forms. Imlay (1968, p. 

C21) noted that the late Pliensbachian ammonite 

assemblage from the Suplee Formation and the overlying Nicely Formation closely resembled that of the same 

age from the Mediterranean area (for example, Italy), as 

shown by the abundance of genera and species among 

the families Dactylioceratidae Hyatt and Hildoceratidae 

Hyatt, and by the absence of those of the family 

Amaltheidae Hyatt. In addition to the ammonites, two 

bivalve (pelecypod) taxa that occur in the Suplee and 

Robertson Formations display distributions that have 

both important latitudinal as well as longitudinal significance. The rudistid-like bivalve Plicatostylus 

Lupher and Packard occurs in the Robertson Formation 
7. FAUNAL AFFINITIES AND TECTONOGENESIS OF MESOZOIC ROCKS 73 

and in the lower part of the Suplee Formation in association with the dominantly Tethyan gastropod Nerinea 

Defrance (see Imlay, 1968, p. C6). Plicatostylus appears 

to be restricted to the eastern Pacific area; it is only 

known from California, Nevada, Oregon, and Peru (Cox, 

1969, p. 866; Imlay, 1980, p. 53-57). The pectenacid 

Weyla Boehm occurs throughout the Suplee Formation 

in the lzee area (for example, at Morgan Mountain, 

west-northwest oflzee ). Damborenea and Mancenido (1979), in their excellent analysis of the paleogeographical distribution of Weyla, indicated that it occurs 

in North Mrica, Arabia, Madagascar, the Eurasian 

Tethys, and along the eastern margin of the Pacific from 

Chile to Alaska. Thus, only in the circum-Pacific region 

does Weyla display an apparent non-Tethyan distribution. It is likely that ifone critically examines all of the 

eastern Pacific high-latitude occurrences of Weyla, it 

will always be found associated with other Tethyan molluscan taxa. Damborenea and Mancenido (1979, p. 88), 

for example, noted that Weyla is present in the Lubbe 

Creek Formation of the Wrangell Mountains, Alaska. 

There is little question that this high-latitude occurrence is due to the northward displacement of 

Wrangellia from low (Tethyan) latitudes. The occurrence of Weyla both in the Lower Jurassic strata of 

Wrangellia and of the Mesozoic clastic terrane suggests 

that both terranes originated in the Tethyan eastern 

Pacific. 

Imlay (1968, p. C14) recovered the following late 

Toarcian ammonites from the lower part (equivalent 

to the Warm Springs Member; see Smith, 1981) of 

the Snowshoe Formation in the area near lzee : 

Haugia Buckman, Polyplectus Buckman, Grammoceras Hyatt?, Catulloceras Gemmellaro, and Dumortiera Haug. Most of these genera appear to be 

widespread Central Tethyan to Southern Boreal forms; 

Catulloceras, however, appears to be dominantly Tethyan (see Ark ell and others, 195 7; Gab illy and other, 1971; 

Sapunov, 1971). 

The Early Jurassic radiolarian assemblage of the 

Nicely, Hyde, and Snowshoe Formations is also diverse 

and contains many elements (for example, 

Praeconocaryomma parvimamma Pessagno and Poisson, Orbiculiforma mclaughlini Pessagno, Canoptum 

anulatum Pessagno and Poisson) in common with Tethyan faunas. Pantanellid diversity and abundance 

remain high. However, the first occurrence of Parvicingula Pessagno in the middle Toarcian part of the 

Warm Springs Member (Snowshoe Formation) is noteworthy. This taxon is restricted to the Northern Tethyan 

Province (Tethyan Faunal Realm) and the Boreal Faunal 

Realm (see discussion below). 

The diverse Middle Jurassic ammonite assemblage 

of the Suplee-lzee area and adjoining areas has been 

monographed by Imlay (1973, 1981). Except for a few 

endemic Pacific genera, most of its Aalenian (equivalent 

to early Bajocian as used by the U.S. Geological Survey 

but not the International Subcommission on Jurassic 

Stratigraphy) and Bajocian genera occur throughout 

the Tethyan Faunal Realm and in the Southern Boreal 

Province of the Boreal Faunal Realm. In contrast, the 

late Bathonian and Callovian ammonite assemblage is 

less diverse and contains genera such as 'Ibrricelliceras 

Buckman, Kepplerites Neumayr and Uhlig, and 

Pseudocadoceras Buckman, which are mostly restricted 

to the Boreal Faunal Realm (see Imlay, 1981, p. 12-13). 

Together with these forms there are genera such as 

Lilloetia Crickmay that are known only from the boreal 

eastern Pacific, and others such as Parpatoceras Spath 

that are predominantly Tethyan. Missing are Callovian 

genera such as Reineckeia Bayle which, exclusive of the 

circum-Pacific area of suspect and displaced terranes, 

occurs in east-central Mexico (Imlay, 1980), North 

Mrica, and in the Alpine-Himalayan belt (Arkell and 

others, 1957). 

Middle Toarcian to Bajocian strata of the Snowshoe 

Formation contain a rich and diverse radiolarian 

assemblage. This assemblage is characterized by the 

abundance and diversity of species of Parvicingula 

Pessagno (sensu Pessagno and Whalen, 1982), Hsuum 

Pessagno, Thranta Pessagno and Blome, Perispyridium 

Dumitrica, and Pantanelliid genera such as Zartus 

Pessagno and Blome, Pachyonchus Pessagno and 

Blome, Gorgansium Pessagno and Blome, and Pantanellium Pessagno (figs. 7.2, 7.3). In general, the composition of the radiolarian assemblage remains much 

the same from middle Toarcian (Early Jurassic) until 

early Hauterivian (Early Cretaceous) time (base of Zone 

1 to top of Zone 5, Pessagno and others, 1984). 

The presence of Pavicingula Pessagno in the middle 

Toarcian to Bajocian assemblage is particularly significant. This taxon is restricted to the Northern Tethyan 

Province of the Tethyan Faunal Realm during this age 

interval (figs. 7.2, 7.3). Central Tethyan deposits ofMiddle and Upper Jurassic red manganiferous ribbon chert 

and limestone from the Mediterranean area 

(Baumgartner and others, 1980), Iran, Oman, Tibet, 

Puerto Rico, and the circum-Pacific region are characterized by their total lack of Parvicingula Pessagno; 

Parvicingula is replaced instead by species of Ristola 

Pessagno and Whalen (figs. 7.2, 7.3). It should be noted 

that pantanelliid diversity is high in all well-preserved 

Central Tethyan samples. 

The Upper Jurassic (Kimmeridgian to upper Tithonian) Taman Formation in east-central Mexico 

(Pessagno and Longoria, unpub. data) contains abundant radiolarians associated with ammonites, the pectenacid Aulacomyella Furlani, calpionellids, and 
7 4 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

nannoconids (fig. 7.3). The presence of calpionellids, 

coupled with a molluscan assemblage of strong Mediterranean affinities, indicates that this area was part of the 

Tethyan Faunal Realm (see Cantu Chapa, 1971; Imlay, 

1980, p. 38). The radiolarian fauna is characterized by 

the presence of Parvicingula Pessagno (sensu Pessagno 

and Whalen, 1982) and by a diverse assemblage ofpantanelliids. Species of Pantanellidae are considerably 

more abundant and diverse than they are in strata of 

Kimmeridgian or Tithonian age in the Boreal Faunal 

Realm (for example, the Galice Formation, Northern 

California, and the upper half of the volcanogenicpelagic succession overlying the Coast Range ophiolite 

at Point Sal and Stanley Mountain). There are three to 

five times more species-level taxa (named and unnamed) present in the Taman assemblage than there 

are in Boreal strata of the same age in California (fig. 

7.2). In addition, it should be noted that the upper Tithonian part of the Taman Formation contains Tethyan 

species such as Acanthocircus dicranocanthos 

Squinabol (Tithonian to lower Hauterivian) that have 

never been observed in the Boreal California faunas. A. 

dicranocanthos also occurs in red ribbon cherts from the 

Mediterranean area, Oman, the Franciscan Complex of 

California, the East Indies (Sarawak), Japan, and other 

areas; it is known as well from numerous central Tethyan Deep Sea Drilling Project samples of Late Jurassic 

to Early Cretaceous age (for example, DSDP Leg 1, Site 

5A, Blake-Bahama Basin; DSDP Leg 32, Sites 303-307; 

DSDP Leg 62, Site 463, Mid-Pacific Mountains; see 

Pessagno, 1969; Foreman, 1975; Schaaf, 1981). The 

Taman radiolarian assemblage from east-central Mexico thus seems to link the assemblage of the Central 

Tethyan Province with that of the Southern Boreal 

Province. Considering also the Tethyan nature of the 

associated mollusks, calpionellids, and nannoconids, 

this indicates that east-central Mexico is representative 

of the Northern Tethyan Province of the Tethyan Faunal 

Realm. 

In the late Bathonian fauna of the Snowshoe Formation (South Fork Member of Smith, 1980) at Izee, 

there is a dramatic drop in pantanelliid diversity, but 

Parvicingula species are abundant and diverse. This 

indicates that by latest Bathonian time the Mesozoic 

clastic terrane was in Boreal latitudes. The ammonite 

assemblage shows a mixture of both Boreal and Tethyan 

elements (predominantly Boreal, see above), suggesting 

that the Mesozoic clastic terrane was situated in the 

Southern Boreal Province by this time. The shift of the 

Mesozoic clastic terrane from lower (Tethyan) to higher 

(Boreal) latitudes is reflected in even a crude analysis of 

pantanelliid diversity. There appears to be a progressive 

drop in pantanelliid diversity from the early Bajocian 

(equals middle Bajocian as used by Imlay, 1973; 

Pessagno and Blome, 1980) onwards. Twenty plus species-level taxa (named and unnamed) are present in 

Aalenian and lower Bajocian Snowshoe samples, seven 

in upper Bajocian Snowshoe samples; two in uppermost 

Bathonian Snowshoe samples; and only one in Callovian samples from the Lonesome Formation (the upper 

Bajocian strata are included in the rotundum Zone of 

Hall and Westermann, 1980). Pantanelliids are virtually 

absent in radiolarian faunas from higher Boreal latitudes. For example, well-preserved middle Callovian 

faunas from the Shelikof Formation of Alaska contain 

Parvicingula and other elements in common with the 

Oregon uppermost Bathonian and Callovian, but they 

totally lack pantanelliids (Blome, 1984b). The Shelikof 

radiolarian assemblage is significant in that it occurs at 

the same horizon with Cadoceras (Stenocadoceras) 

(identifications by R. W. Imlay, U.S. Geological Survey). 

Stenocadoceras Imlay is a high-latitude Boreal taxon, 

which occurs also in Russia and Greenland. 

In summary, the paleontological data indicate that 

the Mesozoic clastic terrane originated at low latitudes 

(Central Tethyan Province) during the Late Triassic 

(Karnian) and was still at relatively low latitudes (Central Tethyan Province) in the Early Jurassic (late 

Pliensbachian). By Toarcian, Aalenian, and Bajocian 

times, this terrane appears to have been at somewhat 

higher latitudes but still within the Tethyan Faunal 

Realm. The presence of abundant Parvicingula in the 

middle Toarcian to Bajocian faunas suggests a latitudinal position within the Northern Tethyan Province. 

Declining pantanelliid diversity through the Bajocian 

may reflect a gradual northward shift· of this terrane 

within the Northern Tethyan Province. The dramatic 

drop in pantanelliid diversity by latest Bathonian to 

middle Callovian, coupled with an ammonite assemblage possessing Boreal taxa together with some Tethyan taxa, suggests a latitudinal position in the Southern 

Boreal Province (figs. 7.2, 7.3). The Mesozoic clastic 

terrane probably was displaced to even higher latitudes 

during the Late Jurassic. Unfortunately, no Upper 

Jurassic strata are exposed; if present, they are covered 

by Cenozoic volcanic rocks. Finally, the presence in the 

Mesozoic clastic terrane of bivalves, such as Weyla and 

Plicatostylus, which are known in the circum-Pacific 

region only from the eastern Pacific, suggests that this 

terrane originated in the eastern Pacific. 

HUNTINGTON ARC TERRANE 

Hillhouse and others (1982) indicated that the calcalkaline volcanic rocks of the Upper Triassic Huntington Formation (Brooks, 1979) formed 18° ( ± 4 °) north 

or south of the Triassic paleoequator. The Huntington 

Formation is overlain unconformably by the Jurassic 
7. FAUNAL AFFINITIES AND TECTONOGENESIS OF MESOZOIC ROCKS 75 

Weatherby Formation (Sinemurian and Callovian; see 

Brooks, 1979; Imlay, this volume). Dickinson (1979, p. 

166) included the Huntington Formation in his Huntington arc terrane and the overlying Weatherby Formation in his Mesozoic clastic terrane. The Weatherby 

Formation contains Early and Middle Jurassic 

ammonite faunas that are similar to those of the SupleeIzee area and adjoining areas in the John Day Inlier (see 

Imlay, 1973, this volume). Hence, these faunas seem to 

reflect the same latitudinal shift from the Tethyan 

Faunal Realm to the Boreal Faunal Realm during Early 

and Middle Jurassic times. 

CONCLUSIONS 

A major stumbling block to interpreting the relationships of the various tectonostratigraphic terranes in 

the Blue Mountains Province has been the correlation of 

the Seven Devils terrane with Wrangellia. If "the 

Wrangellian fly is removed from the soup," tectonostratigraphic relationships between the various terranes appear to be clearer. 

We suggest that the Seven Devils terrane, the central melange terrane, the Mesozoic clastic terrane, and 

the Huntington arc terrane are all components of a 

single island arc complex, the Blue Mountains island 

arc, and that this entire complex originated in the eastern Pacific central Tethys at paleolatitudes about 18° 

north or south (Hillhouse and others, 1982) during the 

Triassic. The combined paleomagnetic and paleontological data from the Seven Devils, Mesozoic clastic, 

and Huntington arc terranes of the Blue Mountains 

island arc indicate that this terrane had been displaced 

to Northern Tethyan latitudes by middle Toarcian to 

Bajocian time and to Southern Boreal latitudes by the 

latest Bathonian to middle Callovian. Subsequent displacement to higher boreal latitudes probably occurred 

during the Late Jurassic. 

It is important to note that the megafossil 

assemblage in volcanic successions of the so-called 

Nevadian complex of California and western Nevada 

reflects the same shift from the Tethyan Faunal Realm 

to the Boreal Faunal Realm during the Mesozoic. Triassic units in related calc-alkaline successions in western Nevada contain megafossils having strong Tethyan 

affinities. In western Nevada the Candelaria, Excelsior, 

Grantsville, Luning, and Gabbs Formations contain 

mollusks, reef corals, and brachiopods of central Tethyan aspect (see Muller and Ferguson, 1939; Silberling, 

1959). For example, Muller and Ferguson (1939, table 4, 

p. 1609) noted that the cephalopod fauna of the Gabbs 

Formation is typically Mediterranean. Their extensive 

list of taxa includes forms such as Stenoarcestes 

Moj sisovics, Cladiscites Moj sisovics, Paracladiscites 

Mojsisovics, Pinacoceras Mojsisovics, and Placites 

Mojsisovics. These forms occur outside the circumPacific region, in the Alpine-Himalayan belt (Arkell and 

others, 1957). It is also significant to note that reefbuilding corals occur in the Luning Formation (see 

Muller and Ferguson, 1939, p. 1599-1600). Silberling 

(1959, p. 20-21) noted that a late Karnian assemblage of 

ammonites similar to that described by Mojsisovics 

(1893) from the Hallstatt region of the Austrian Alps 

occurs in the Hosselkus Limestone in the Taylorsville 

area (Shasta County, California). Furthermore, Muller 

and Ferguson (1939, p.1600) noted that Norian strata in 

Shasta County, California (presumably in the Hosselkus Limestone) contained an assemblage of reef-building corals that is similar to that of the Luning 

Formation. 

The Tethyan character of the molluscan assemblage 

in so-called Nevadian rocks is likewise reflected in Early 

Jurassic successions related to calc-alkaline volcanism 

in the Sierra Nevada and in western Nevada. For example, Imlay (1968) noted that the late Pliensbachian 

ammonite assemblage of the Sailor Canyon Formation 

(Sierra Nevada) exhibits strong Mediterranean 

affinities like those of the Nicely and Hurwal Formations in the Mesozoic clastic terrane of the Blue Mountains island arc. It is also worth noting that the Tethyan 

bivalve Weyla Bohm occurs in the Potem Formation of 

north-central California and in the Hardgrave Sandstone of the Taylorsville area in northern California (see 

Imlay, 1980, p. 57, 61 ). Furthermore, Plicatostylus 

Lupher and Packard, which is associated with Weyla in 

the lower part of the Suplee Formation in Oregon, occurs 

in the Sunrise Formation of western Nevada and in the 

Thompson Limestone of the Taylorsville area in northern California (Imlay, 1980, p. 53, 57). The Middle 

Jurassic ammonite assemblage of the Sierra Nevada, 

though not as well known, contains many of the same 

faunal elements as that of Oregon. Middle Jurassic 

(Bajocian) radiolarians are unknown from so-called 

Nevadian rocks except at one locality near the Consummes River. A sample of tuffaceous chert (Sample D03-11 

from Philip Behrman, University of California, 

Berkeley) from this locality was found to contain a Central Tethyan radiolarian assemblage including Ristola 

Pessagno and Whalen, Zartus Pessagno and Blome, 

Pantanellium Pessagno, and Pachyoncus Pessagno and 

Blome (figs. 7.2, 7.3). 

The Callovian ammonite assemblage of the western 

part of the Sierra Nevada, like that in the Blue Mountains island arc of Oregon, shows a mixture of Boreal 

with Tethyan to Southern Boreal elements (see Imlay, 

1961, p. D18). Boreal elements include Cadoceras 

Fischer, Paracadoceras Crickman, Pseudocadoceras 

Buckman, and Kepplerites Neumayr and Uhlig; Teth-
76 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

yan to Southern Boreal elements include such forms as 

Choffatia Siemiradzki, Reineckeites Buckman, and 

Grossouvria Siemiradski (see Imlay, 1961, p. D6, D18). 

Oxfordian and Kimmeridgian strata in this area are 

characterized by the abundance of the Boreal bivalve 

Buchia concentrica (Sowerby), in association with 

ammonites that are strictly Boreal, such as Amoeboceras Hyatt, or that are predominantly Tethyan, such 

as Idoceras Burckhardt. Kimmeridgian radiolarian 

faunas from the lower part of the Galice Formation in 

northern California are characterized by the presence of 

Parvicingula Pessagno (sensu Pessagno and Whalen, 

1982) and a pantanellid assemblage of low diversity. 

These data, together with those from the Blue 

Mountains island arc, suggest that the so-called Nevadian terrane and the Blue Mountains island arc were 

part of the same island arc complex, which originated at 

near-equatorial latitudes in the eastern Pacific. We suggest that this island arc complex was carried northward 

along a megashear system analogous to the present day 

San Andreas fault. Such a megashear may have been 

related to those well documented by Longoria (1984) in 

east-central and northeastern Mexico, and therefore to 

the rifting and subsequent sea-floor spreading which 

formed the Gulf of Mexico and moved North America 

away from South America (Buffler and others, 1980; 

Dickinson and Coney, 1980 ). 

We further suggest that island-arc volcanism in the 

Blue Mountains island arc occurred in two phases: (1) a 

Permian to Late Triassic near-axis phase (Seven Devils 

Group, Huntington Formation, Begg Member of the Vester Formation, Fields Creek Formation) and (2) an Early 

Jurassic (late Pliensbachian) and Middle Jurassic (Callovian) off-axis phase (Nicely, Snowshoe, Trowbridge, 

and Weatherby Formations). The central melange terrane component of the Blue Mountains island arc (Paleozoic to Late Triassic; Early Jurassic?) may represent a 

subduction complex associated with the earlier phase of 

island-arc volcanism noted above. The rocks in the 

Mesozoic clastic terrane component of the Blue Mountains island arc reflect a second phase of island -arc 

development, which began in the Early Jurassic (late 

Pliensbachian) and continued at least until the Middle 

Jurassic (early Callovian). The position of the axial zone 

of the Jurassic arc that produced the sporadic tuffs, 

andesitic tuff breccias, and andesitic flows in the Mesozoic clastic terrane component of the John Day Inlier is, 

at present, enigmatic and may never be known because 

of the cover of Cenozoic volcanic rocks. However short 

lived, comparatively simple island-arc complexes, such 

as the Greater Antilles, yield some important inferences 

concerning the position of the axial zone of island-arc 

volcanism. In Puerto Rico, for example, island-arc volcanism occurred from Early Cretaceous (Aptian? and 

Albian) to early middle Eocene time along a northwestsoutheast axis, which gradually shifted northwards (see 

Christman, 1953; 1973: Lesser Antilles). The youngest 

plutonic rocks are batholiths of quartz monzonite and 

quartz diorite (Utuado and San Lorenzo batholiths), 

which were emplaced in the axial zone of early middle 

Eocene volcanism during or subsequent to a major 

orogeny that culminated island -arc volcanism and 

intensely folded and faulted all early middle Eocene and 

older rocks (Weaver, 1958; Berryhill and others, 1960; 

Mattson, 1960; Pessagno, 1960,1961, 1962; Glover, 1971). 

There appears to be a shift in "granitic" plutonic activity 

in eastern Oregon and western Idaho from west to east 

during late Triassic to early Tertiary time, and a corresponding shift in the axial zone of island-arc volcanism 

may be suggested (see Hamilton, 1978). 

REFERENCES CITED 

Arkell, W.J., Kummel, B., and Wright, C.W., 1957, Mesozoic 

Ammonoidea, in Arkell, W.J., and others, Treatise on Invertebrate Paleontology, pt. L, Mollusca 4, Cephalopods, Ammonoidea: Geological Society of America and University of 

Kansas, p. LBO-L465. 

Axelrod, D.I., 1963, Fossil floras suggest stable, not drifting continents: Journal of Geophysical Research, v. 68, p. 3257-3263. 

Baumgartner, P.O., DeWever, P., and Kocher, R., 1980, Correlation of 

tethyan Late Jurassic-Early Cretaceous radiolarian events: 

Cahiers de Micropaleontologie, v. 2, p. 23-73, pls. 1-6. 

Berryhill, H.L., Jr.; Briggs, R.P., and Glover, L.G., III, 1960, Stratigraphy, sedimentation, and structure of Late Cretaceous rocks in 

eastern Puerto Rico-preliminary report: American Association 

of Petroleum Geologists Bulletin, v. 44, no. 2, p. 137-155. 

Blome, C.D., 1983, Upper Triassic Capnuchosphaeridae and Capnodocinae (Radiolaria) from east-central Oregon: Micropaleontology, v. 29, no.1, p.ll-49, pls. 1-11 

--1984a, Upper Triassic Radiolaria and radiolarian zonation for 

North America: Bulletins of American Paleontology, v. 84, no. 

318, p. 1-98, 17 pls. 

--1984b, Middle Jurassic (Callovian) radiolarians from carbonate 

concretions, Alaska and Oregon: Micropaleontology, v. 30, no. 4, 

p. 343-389. 

Bostwick, nA., and Nestell, M.K., 1967, Permian tethyan fusilinid 

faunas of the northwestern United States in Adams, C. G. , and 

Ager, D.V. , eds. Aspects of Tethyan biogeography: Systematic 

Association Publication no. 7, p. 93-102. 

Brooks, H. C., 1979, Plate tectonics and geologic history of the Blue 

Mountains: Oregon Geology, v. 41, no. 5, p. 71-80. 

Brooks, H.C., and Vallier, T.L., 1978, Mesozoic rocks and tectonic 

evolution of eastern Oregon and western Idaho, in Howell, D.G., 

and McDougall, K. A., eds.: Mesozoic paleogeography of the 

Western United States, Pacific Coast Paleogeography Symposium 2, Pacific Section, Society of Economic Paleontologists 

and Mineralogists, Los Angeles, California, p. 133-145. 

Brown, C.E., and Thayer, T.P., 1977, Geologicmapofpre-Tertiaryrocks 

in the eastern Aldrich Mountains and adjacent areas to the 

south, Grant County, Oregon: U.S. Geological Survey Miscellaneous Investigation Map; 1-1021, scale 1:52,500. 

Buffler, R.T. , Watkins, J.S., Sahub, F.J., and Worzel, J.L., 1980, Structure and early geologic history of the deep central Gulf of Mexico 

basin, in Pilger, R.H., Jr., ed., The origin of the GulfofMexico and 
7. FAUNAL AFFINITIES AND TECTONOGENESIS OF MESOZOIC ROCKS 77 

the early opening of the central North Atlantic Ocean: Proceedings of a symposium at Louisiana State University, School of 

Geoscience, Louisiana State University, p. 1-16. 

Cantu Chapa, A., 1971, La serie Huasteca (Jurasico media-superior) 

del centro este de Mexico: Instituto Mexicano Petroleo Revista, v. 

3, no. 2, p. 17-40. 

Carlisle, D., and Susuki, T., 1974, Emergent basalt and submergent 

carbonate-clastic sequences including the Upper Triassic 

Dilleri and Welleri Zones on Vancouver Island: Canadian Journal of Earth Sciences, v. 11, p. 254-279. 

Christman, R.A., 1953, Geology of St. Bartholomew, St. Martin, and 

Anguilla, Lesser Antilles: Geological Society of America Bulletin, v. 64, p. 65-96. 

---1973, Volcanic geology of southwestern Antigua, B.W.I., in 

Shagam, R., and others, Studies in Earth and Space Sciences: 

Geological Society of America Memoir 132, p. 439-448. 

Cox, L.R. , 1969, Class, order and family uncertain, in Cox, L.R., and 

others, Treatise on Invertebrate Paleontology, pt. N, Mollusca 6, 

Bivalvia: Geological Society of America and University of Kansas, p. N866. 

Damborenea, S.E. , and Mancenido, M.O., 1979, On the palaeogeographical distribution of the pectenid Weyla (Bivalvia, Lower 

Jurassic): Palaeogeography, Palaeoclimatology, and Palaeoecology, v. 27, p. 85-102. 16 

Dickinson, WR. , 1979, Mesozoic forearc basin in central Oregon: 

Geology, v. 7, p. 166-170. 

Dickinson, W.R. , and Coney, P.J. , 1980, Plate tectonic constraints on 

the origin of the Gulf ofMexico, in Pilger, R.H., Jr., ed., The origin 

of the Gulf of Mexico and the early opening of the central North 

Atlantic Ocean: School of Geoscience, Louisiana State University, p. 27-36. 

Dickinson, W.R., and Thayer, T.P., 1978, Paleogeographic and paleotectonic implications of Mesozoic stratigraphy in the John 

Day Inlier of central Oregon, in Howell, D. G., and McDougall, 

K.A., eds., Meozoic paleogeography of the western United 

States: Pacific Coast Paleogeography Symposium 2, Pacific Section Society of Economic Paleontologists and Mineralogists, Los 

Angeles, California, p. 147-161. 

Dickinson, WR., and Vigrass, L.W., 1965, Geology of the Suplee-Izee 

area, Crook, Grant, and Harney Counties, Oregon: Oregon 

Department of Geology and Mineral Industries Bulletin 58, p. 

1-109, pls. 1-3, figs. 1-30. 

Enay, R. , Tintant, H. , and Cariou, E., 1971, Les Faunes Oxfordienes 

d'Europe meridionale essai de zonation, in Colloque du Jarassique (Luxembourg, 1967): Paris, France, Bureau de Recherches 

Geologiques et Minieres Memoires, no. 75, p. 635-657. 

Fischer, A. G., 1960, Latitudinal variations in organic diversity: Evolution, v. 14, no. 1, p. 64-81. 

Foreman, H.P., 1975, Radiolaria from the North Pacific, Deep Sea 

Drilling Project, Leg 32, in Larson, R.L., Moberly, Ralph, and 

others, Initial reports of the Deep Sea Drilling Project: Washington, D.C., U.S. Government Printing Office, v. 32, p. 579-676. 

Gabilly, J., Elmi, S., Mattei, J. , Mouterde, R., and Rioult, M. , 1971, Le 

Toarcian du centre-ouest de la France, in Colloque du Jurassique (Luxembourg, 1967): Paris, France, Bureau de Recherches 

Geologiques et Minieres Memoires, no. 75, p. 605-634. 

Glover, L., III, 1971, Geology of the Coamo area, Puerto Rico, and its 

relation to the volcanic arc-trench association: U.S. Geological 

Survey Professional Paper 636, p. 1-102, 4 pls. 

Gordon, WA., 1974, Physical controls on marine biotic distribution in 

the Jurassic Period, in Ross, C.A., ed., Paleogeographic 

provinces and provinciality: Society of Economic Paleontologists 

and Mineralogists, Special Publication no. 21, p. 136-147. 

Hall, R.L., and Stronach, N.J., 1982, A guidebook to the Fernie Formation of southern Alberta and British Columbia: Calgary, Alberta, 

Circum-Pacific Jurassic Research Group (I.G.C.P. no. 171), First 

Field Conference, p. 1-48, 10 pls. 

Hall, R.L. and Westermann, G.E.G., 1980, Lower Bajocian (Jurassic) 

cephalopod fauna from western Canada and prosed assemblage 

zones for the lower Bajocian ofN orth America: Paleontographica 

Americana, v. 9, 93 p. 

Hamilton, W., 1978, Mesozoic tectonics of the Western United States, 

in Howell, D.G., and McDougall, K., eds., Mesozoic Paleogeography of the Western United States: Pacific Coast Paleogeography 

Symposium 2, Pacific Section Society of Economic Paleontologists and Mineralogists, Los Angeles, California, p. 33-70. 

Hillhouse, J.W, Gramme, C.S., and Vallier, T.L., 1982, Geomagnetism 

and Mesozoic tectonics of the Seven Devils volcanic arc in northeastern Oregon: Journal of Geophysical Research, v. 87, no. B5, 

p. 3777-3794. 

Holder, H., 1979, Jurassic, in Berggren, W.A., and others, eds., 

Treatise on Invertebrate Paleontology, pt. A, Introduction-fossilization (Taphonomy), biogeography, and biostratigraphy: Geological Society of America and University of Kansas, p. 

A390-A417. 

Imlay, R.W., 1961, Late Jurassic ammonites from the western Sierra 

Nevada, California: U.S. Geological Survey Professional Paper 

374-D, p. D1-D30, 6 pls. 

---1964, Upper Jurassic mollusks from eastern Oregon and western Idaho: U.S. Geological Survey Professional Paper 483-D, p. 

1-21,4 pls. 

---1968, Lower Jurassic (Pliensbachian and Toarcian) ammonites 

from eastern Oregon and California: U.S. Geological Survey 

Professional Paper 593-C, p. C1-C51, 9 pls. 

---1973, Middle Jurassic (Bajocian) ammonites from eastern 

Oregon: U.S. Geological Survey Professional Paper 756, 100 p., 

48 pls. 

---1980, Jurassic paleobiogeography of the conterminous United 

States in its continental setting: U.S. Geological Survey Professional Paper 1062, p.1-134. 

---1981, Jurassic (Bathonian and Callovian) ammonites in eastern 

Oregon and western Idaho: U.S. Geological Survey Professional 

Paper 1142, p. 1-24, 4 pls. 

Irving, E., 1979, Paleopoles and paleolatitudes of North America and 

speculations about displaced terrains: Canadian Journal of 

Earth Sciences, v. 16, p. 669-694. 

Jones, D.L., Pessagno, E.A., Jr., and Force, E.R., 1976, Jurassic radiolarium chert from near John Day, Oregon [abs.]: Geological 

Society of America Abstracts with Programs, Cordilleran Section, Annual Meeting, 72d, v. 8, no. 3, p. 386. 

Jones, D.L., Silberling, N.J., and Hillhouse, J., 1977, Wrangellia-A 

displaced terrane in northwestern North America: Canadian 

Journal of Earth Sciences, v. 14, p. 2565-2577. 

Kozur, H., and Mostler, H., 1981, Beitrage zur Erforschung der mesozoischen Radiolarien. Teil IV: Thalassosphaeracea Haeckel, 

1862 emedn. Petrusevskaja, 1979, Sponguracea Haeckel, 1862 

amend. und weitere triassische Lithocycliacea, Trematodiscacea, Actinommacea und Nassallaria: Geologische Palaontologische Mitteilungen Innsbruck Sonderband, p. 1-208, 

pls.1-69. 

Loeblich, A.R. , Tappan, H., Barker, R.W Cole, WS., Douglass, R.C. 

Riechel, Manfred, and Thompson, M.L., 1964, Sarcodina, chiefly 

"Thecamoebians" and Foraminiferida: Treatise on Invertebrate 

Paleontology, pt. C, Protista 2: Geological Society of America and 

University of Kansas, p. C1-C899. 

Longoria, J.F., 1984, Mesozoic tectonostratigraphic domains in eastcentral Mexico: Geological Association of Canada Special Paper 

27, p. 65-76. 

Mattson, P.H., 1960, Geology of the Mayaguez area: Geological Society 

of America Bulletin, v. 71, p. 319-362. 
78 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

McWilliams, M.O., and Howell, D.G., 1982, Exotic terranes of western 

California: Nature, v. 297, p. 215-217. 

Merriam, C. W., and Berthiaume, S.A., 1943, Late Paleozoic formations 

of central Oregon: Geological Society of America Bulletin, v. 54, 

no. 2, p. 145-171. 

Mojsisovics, von Majsvar, Edmund, 1893, Die Cephalopoden der 

Halstatter Kalke: Abhandlungen der Kaiserlich-Koniglichen 

Geologischen Reichsanstalt, Wien (Halfte 2), 835 p. 

Morrison, R.F., 1961, Angular unconformity marks Triassic-Jurassic 

boundary in Snake River area of northeastern Oregon: Ore Bin, 

v. 23, no. 11, p. 105-111. 

---1964, Upper Jurassic mudstone unit named in Snake River 

Canyon, Oregon-Idaho boundary: Northwest Sciences, v. 38, no. 

3, p. 83-87. 

Muller, S.W., and Ferguson, H.G., 1939, Mesozoic stratigraphy of the 

Hawthorne and Tonopah quadrangles, Nevada: Geological 

Society of America Bulletin, v. 50, p. 1573-1624, 5 pls. 

Pessagno, E. A, Jr., 1960, Geology of the Ponce-Coamo area, Puerto 

Rico: Princeton, N. J., Princeton University, Ph.D. dissertation, 

147 p. 

---1961, The micropaleontology and biostratigraphy of the middle 

Eocene Jacaguas group: Micropaleontology, v. 7, no. 3, p. 

351-358. 

---1962, The Upper Cretaceous stratigraphy and micropaleontology of south-central Puerto Rico: Micropaleontology, v. 8, no. 

3, p. 349-368, pls. 1-6. 

---1969, Mesozoic planktonic foraminifera and Radiolaria, in 

Ewing, Maurice, Worzel, J.L., and others, eds., Initial reports of 

the Deep Sea Drilling Project: Washington, D.C., U.S. Government Printing Office, v. 1, p. 607-621, 

Pessagno, E.A., Jr., and Blome, C.D., 1980, Upper Triassic and 

Jurassic Pantanelliinae from California, Oregon, and British 

Columbia: Micropaleontology, v. 26, no. 3, p. 18 225-273, pls. 

1-11. 

---1982, Bizarre Nassellariina (Radiolaria) from the Middle and 

Upper Jurassic ofN orth America: Micropaleontology, v. 28, no. 3, 

p. 289-318, pls. 1-8. 

Pessagno, E.A., Jr., Blome, C.D., and Longoria, J.F., 1984, A revised 

zonation for the Upper Jurassic of western North America: Bulletins of American Paleontology, v. 87, no. 320, 51 p., 5 pls. 

Pessagno, E.A., Jr., Finch, W., and Abbott, PL., 1979, Upper Triassic 

Radiolaria from the San Hipolito Formation, Baja California: 

Micropaleontology, v. 25, no. 2, p. 160-197, pls. 1-9. 

Pessagno, E.A., Jr., and Whalen, P.A., 1982, Lower and Middle 

Jurassic Radiolaria (multicyrtid Nassellariina) from California, 

east-central Oregon, and the Queen Charlotte Islands, B.C.: 

Micropaleontology, v. 28, no. 2, p.111-169, 13 pls. 

Sapunov, I. G., 1971, Notes on the geographical differentiation of the 

Lower Jurassic ammonite faunas, in Colloque Jurassique (Luxembourg, 1967): Paris, France, Bureau de recherches Geologiques et Miniere Memoires, no. 75, p. 263-270. 

Sarewitz, Daniel, 1983, Seven Devils terrane: Is it really a piece of 

Wrangellia?: Geology, v. 11, p. 634-637. 

Schaaf, A, 1981, Late Early Cretaceous Radiolaria from Deep Sea 

Drilling Project Leg 62, in Thiede, J., Vallier, T.L., and others: 

Initial reports of the Deep Sea Drilling Project: Washington, 

D.C., U.S. Government Printing Office, v. 62, p. 419-469, pls. 

1-27. 

Silberling, N.J., 1959, Pre-Tertiary stratigraphy and Upper Triassic 

paleontology of the Union District, Shoshone Mountains, 

Nevada: U.S. Geological Survey Professional Paper 322, 67 p., 9 

pls. 

Smith, A.G., Hurley, A.M., and Briden, J.C., 1981, Phanerozoic paleocontinental world maps: Cambridge, Mass., Cambridge University Press, 102 p. 

Smith, PL., 1980, Correlation of the members of the Jurassic Snowshoe Formation in the Izee basin of east-central Oregon: Canadian Journal ofEarth Sciences, v. 17, no. 12, p. 1603-1608. 

Sutherland Brown, A, 1968, Geology of the Queen Charlotte Islands: 

British Columbia Department of Mines and Petroleum 

Resources Bulletin 54, p. 3-226, 18 pls. 

Taubeneck, W.H., 1955, The age of the Elkhorn Ridge Argillite, northeastern Oregon: Northwest Science, v. 29, p. 97-100. 

Tipper, H. W., 1981, Offset of an upper Pliensbachian geographic zonation in the North American Cordillera by Transcurrent movement: Canadian Journal of Earth Sciences, v. 18, p. 1788-1792. 

Tippit, P., 1981, The biostratigraphy and taxonomy of Mesozoic Radiolaria from the Samail Ophiolite and Hawasina Complex, Oman: 

University of Texas at Dallas, Ph.D. dissertation, 396 p. 

Vallier, T. L., 1977, The Permian and Triassic Seven Devils Group, 

western Idaho and northeastern Oregon: U.S. Geological Survey 

Bulletin 1437, 58 p. 

Vallier, T.L., and Hooper, P.R., 1976, Geologic guide to Hells Canyon, 

Snake River: Geological Society of America Annual Meeting, 

Cordilleran Section, 72d: Pullman, Washington, Washington 

State University, Department of Geology, Field Guide no. 5, p. 

1-33. 

Wardlaw, B.R., Nestell, M.K., and Dutro, J.T. , Jr., 1982, Biostratigraphy and structural setting of the Permian Coyote Butte Formation of central Oregon: Geology, v. 10, no.l, p. 13-16. 

Weaver, J.D., 1958, Utuado Pluton, Puerto Rico: Geological Society of 

America Bulletin, v. 69, p.1125-1142. 
8. GEOLOGIC IMPLICATIONS OF RADIOLARIAN-BEARING 

PALEOZOIC AND MESOZOIC ROCKS FROM THE BLUE MOUNTAINS 

PROVINCE, EASTERN OREGON 

By CHARLEs D. BLOME, DAVID L. joNES 

BENITA L. MuRCHEY, and MARGARET LINIECKI 

ABSTRACT 

The Blue Mountains province can be described as a collage of 

tectonic blocks or "terranes," some of which have been displaced from 

their original site of formation. Five such tectonostratigraphic terranes are now recognized in the province: the Grindstone, lzee, Olds 

Ferry, Baker, and Wallowa terranes. The ability to determine the ages 

of late Paleozoic and early Mesozoic radiolarian-bearing rocks in the 

southwestern part of the Blue Mountains province provides critical 

evidence for unraveling the province's stratigraphic and structural 

history. 

Most cherts from the Grindstone terrane are Early Permian to 

Early Triassic in age. Cherts from the southwestern part of the Baker 

terrane are Late Triassic, whereas those in the northeastern part are 

of both Permian and Late Triassic age. A few Baker terrane cherts may 

even be as young as Early Jurassic. The absence of cherts of Late 

Triassic age in the Grindstone terrane, its general lack of volcanic and 

volcaniclastic rocks, and its low regional metamorphic grade, all indicate that the Grindstone terrane is a separate tectonic block from the 

juxtaposed Baker and Izee terranes. 

Upper Triassic cherts collected from sedimentary units 

throughout the Izee terrane prove that some units are facies equivalents and provide new insight into their provenances. A Carboniferous age for a chert clast from the basal part of the Izee terrane 

and the Permian and Early Triassic ages established for cherts in the 

Grindstone terrane make it unlikely that the Grindstone was the sole 

source for Izee detritus. Permian and Triassic sedimentary and volcaniclastic units in the Baker terrane are an obvious source for 

detritus in the sedimentary units of the Izee terrane, as well as for the 

Jurassic flysch in the Olds Ferry terrane. 

INTRODUCTION 

Pre-Cenozoic rocks within the Blue Mountains 

province occur in a belt trending northeast from the 

area near the town of Suplee to near Grangeville, Idaho 

(fig. 8.1). Numerous inliers or windows of Paleozoic and 

Mesozoic (Devonian to Cretaceous) rocks in this belt are 

surrounded by Tertiary lavas and sedimentary rocks of 

continental origin (Brooks and Vallier, 1978). These 

inliers contain the only pre-Tertiary outcrops known 

between British Columbia and northernmost Washington on the north, and southern Oregon on the south 

(Dickinson and Thayer, 1978). 

The varied terminology used for the structural 

units within the Blue Mountains province of northeastern Oregon and southwestern Idaho can be confusing. For consistency and simplicity, the terrane map 

constructed by Silber ling and others (1984) is used here. 

They divide the east-central Oregon area, starting in 

the southwest, into five distinct tectonostratigraphic 

terranes: Grindstone, lzee, Olds Ferry, Baker, and Wallowa (fig. 8.1). 

The Grindstone terrane was first termed the Paleozoic shelf terrane by Vallier and others (1977) because of 

the presence of shallow-water Devonian rocks in its 

western part. This tectonic block was also termed the 

melange terrane by Dickinson and Thayer (1978), and it 

represents the southwesternmost part of the dismembered oceanic terrane of Brooks and Vallier (1978). 

The lzee terrane contains abundant clastic rocks 

and includes the western half of Vallier and others' 

(1977) oceanic terrane, the western half of Dickinson's 

(1979) Mesozoic clastic terrane, and the western half of 

the forearc basin terrane of Brooks (1979a). 

The rocks included in the Olds Ferry terrane were 

originally considered to form the southern part of the 

oceanic terrane and the southern part of the volcanic arc 

terrane as described by Vallier and others (1977). These 

rocks later included the Jurassic flysch terrane and 

Juniper Mountain-Cuddy Mountain volcanic arc terrane of Brooks and Vallier (1978). The Olds Ferry terrane also represents the eastern half of Dickinson's 

(1979) Mesozoic clastic terrane and was included as part 

of the forearc basin as described by Brooks (1979a). 

The Baker terrane was originally defined as the 

oceanic terrane by Vallier and others (1977) because it 

consisted of structurally dismembered blocks of oceanic 

origin. It was later termed the dismembered oceanic 

terrane by Brooks and Vallier (1978) and the central 

melange terrane by Dickinson and Thayer (1978). 

The Wallowa terrane was originally considered the 

northern part of the volcanic arc terrane of Vallier and 

others (1977). It has also been termed the Wallowa 

79 
80 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

Mountains-Seven Devils Mountains volcanic arc terrane by Brooks and Vallier (1978) and the Seven Devils 

terrane by Dickinson (1979). The Wallowa terrane is 

considered by Jones and others (1977) to represent a 

possible detached block of the Wrangellia terrane, 

known mainly from Alaska and British Columbia. 

Although the general geology of the various terranes is known, critical stratigraphic and structural 

relationships between juxtaposed terranes are yet to be 

resolved, in part because of inadequate paleontologic 

dating. Radiolarian biostratigraphy has proven helpful 

in resolving stratigraphic problems in volcanic-arc and 

ophiolite assemblages (Blome and Irwin, 1985) and in 

tectonically disrupted units such as melanges or 

olistostromes (Blome, 1984). The purposes of this paper 

are to ascertain the age relationships of radiolarianbearing rocks within some of the terranes defined by 

Silberling and others (1984) and, as far as possible, to 

establish depositional relationships within each individual terrane, as well as structural relationships 

between adjacent terranes. 

GRINDSTONE TERRANE 

The Grindstone terrane contains the oldest rocks 

within the Blue Mountains province. This olistostrome1 150 

WASHINGTON IDAHO 

... , _, -- .,..,.,.. 

r 

q-BA 

GS 

, __ , __ , 

~r WA 

-----·-... 

, 

IZ~ ,,'' 

_, 

WA-==:::! 

OREGON 

0 

I 

5 0 

I 

I 

I 

100 KIL O M E TERS 

I 

FIGURE 8.1.-Distribution of pre-Tertiary rocks with generalized terrane boundaries for the southwestern part of the Blue Mountains province: 

WA = Wallowa terrane; BA =Baker terrane; IZ = Izee terrane; OF = Olds Ferry terrane; and GS =Grindstone terrane (after Silberling 

and others, 1984). Star symbols indicate radiolarian collecting localities. 
8. GEOLOGIC IMPLICATIONS OF RADIOLARIAN-BEARING PALEOZOIC AND MESOZOIC ROCKS 81 

rich terrane is exposed along the southwestern border of 

the province (fig. 8.1) and contains a tectonically disrupted assemblage of (1) Middle Devonian limestone 

interstratified with cherty sandstone, chert, and 

argillite; (2) Mississippian argillite, sandy limestone, 

calcareous sandstone, and conglomeratic sandstone 

(Coffee Creek Formation); (3) Pennsylvanian mudstone, 

sandstone, and conglomerate containing plant remains 

(Spotted Ridge Formation); (4) Permian partly 

fusulinid-bearing, partly feldspathic, and sandy limestone (Coyote Butte Formation); and (5) Permian radiolarian-bearing red, black, and green chert. The first 

four of these units were first described by Merriam and 

Berthiaume ( 1943 ). 

According to Dickinson (1979), both Tethyan and 

American fusulinid faunas occur within this terrane. 

Fossiliferous limestones have yielded a variety of faunas 

ranging in age from Devonian to Permian (Merriam and 

Berthiaume, 1943; Kleweno and Jeffords, 1961; Dickinson and Vigrass, 1965). Devonian limestones containing 

stromatoporoids and other shallow-water invertebrates 

were first reported in the northwestern part of the terrane by Kleweno and Jeffords ( 1961 ). Permian fusulinids 

from limestones near Suplee were also noted by Dickinson and Vigrass (1965), and both they and Merriam and 

Berthiaume (1943) inferred that these fusulinid limestones are correlative with limestones in part of the 

Elkhort Ridge Argillite near the town of Sumpter 

(located approx 30 mi northwest of Baker, Oregon; 

Taubeneck, 1955). According to Wardlaw and others 

(1982), the Coyote Butte Formation contains conodonts, 

fusulinids, and brachiopods of Early Permian (Leonardian) age and is similar in age, fauna, and sedimentology to limestone near Quinn River Crossing, Nevada. 

Siliceous rocks within the Grindstone terrane 

include abundant blue-black, green, and red chert, 

cherty graywacke, tuff, tuffaceous breccia and chert 

breccia, as well as chert-pebble conglomerate (Dickinson and Thayer, 1978). Chert exposures predominate 

over limestone in the north and represent sparsely 

exposed, lenticular pods, most of which are elongate in a 

north-south direction. These chert exposures are generally red and green and are most continuous in the north 

near the Weberg Ranch and along the North Fork of 

Trout Creek (fig. 8.2). Chert exposures to the south 

between Grindstone and Twelvemile Creeks are 

smaller, less continuous, and more varied in color. 

Almost all the chert exposures, no matter what the 

internal color, weather to blue-black. Most of the chert, 

even where poorly exposed, exhibits well-developed bedding structure, in contrast to the massive metachert 

within the Elkhorn Ridge Argillite to the east. Cherty 

breccia, tuff, and recrystallized ( tectonized) tan chert 

and white limestone form more prominent exposures 

than the less diagenetically altered red and green chert 

and buff limestone. In the northern part of the Grindstone terrane, chert and limestone occur on the 

topographic highs, whereas tuff, chert breccia, and conglomerate occur on the ridge flanks. 

Structurally discontinuous tuffaceous red and 

green chert was collected for radiolarians in the Suplee 

quadrangle due west of the Robertson Ranch. Two 

thinly bedded blocks of chert (82CB-106, -108; see fig. 

8.2 and locality descriptions) contained radiolarian 

faunas which are probably Early Permian (late Wolfcampian or early Leonardian) and are characterized by 

Pseudoalbaillella scalprata Holdsworth and Jones, 

1980 and by P. longicornis lshiga, Kito, and Imoto, 

1982b. 

Discontinuous belts of chert, limestone, cherty 

breccia, and conglomerate continue farther south and 

southwest into the Delintment Lake quadrangle and 

the eastern half of the Twelvemile Reservoir quadrangle. Just north of Grindstone Creek in the northwest 

corner of the Delintment Lake quadrangle, these rocks 

are more metamorphosed (greenschist to amphibolite 

facies). Chert samples (82CB-105 and -111; see fig. 8.2 

and locality descriptions) collected just north of an 

unnamed reservoir along Grindstone Creek contained 

middle Permian (late Leonardian or early Guadalupian) 

radiolarian faunas (plate 8.1). Characteristic species 

include Parafollicucullus fusiformis Holdsworth and 

Jones, 1980, Pseudoalbaillella longicornis lshiga, Kito, 

and Imoto, 1982b, P. globosa Ishiga, Kito, and Imoto, 

1982b, Latentifistula sp., and other undescribed genera 

of the superfamily Latentifistulidea Nazarov and 

Ormiston, 1983. At present, this fauna appears older 

than the Lamar Limestone of Guadalupian age 

(Ormiston and Babcock, 1979). 

Chert samples collected approximately 1 mi north 

of82CB-105 yielded an equally well-preserved Permian 

radiolarian fauna of similar age. This fauna is correlative with the Follicucullus monocanthus assemblage in Japan, which Ishiga and others (1982b) 

consider to be late Leonardian or early Guadalupian in 

age. Samples of tuffaceous green chert (82CB-109A to 

C; see fig. 8.2 and locality descriptions) collected from a 

block of chert breccia in the same vicinity yielded a Late 

Permian (late Guadalupian or Ochoan) radiolarian 

fauna. Although these faunas remain largely undescribed, they do containAngulobracchia, Latentifistula, 

and other distinct cross-axon forms described by Takemura and Nakaseko (1981), as well as undescribed mammelate spheroidal spumellarians (plate 8.1). 

Samples of well-bedded chert (82CB-114A to C; see 

fig. 8.2 and locality descriptions) collected south of 

Twelvemile Creek, near Three Buttes (also known as 

Coyote Butte and designated the type locality of the 
82 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

\. ... , __ 

·-..... 

'\ 

i',_ ( ( 

\ 

\. 

'\ 

\ 

\ 

\J-.···- \ 

Shaw Table 

A. 

I 

........ ,./ 

· .. \'~~~-~ 

11 

I' 

,, 

,, 

~ ,, 

,, 

•' ,, 

~ ,, 

ol 

~ 

\1 

')) 

" ,, 

~ 

82 CB - 108 A - D * 

'-... ,., II I * 8 2CB -"1 06 A - 0 

l.. 

\ 

105 A - C EXPLANATION 

[3 Chert 

f§1?iM Conglomerate 

~Limestone 

3 4 K IL OMETERS 

FIGURE 8.2.-Radiolarian localities south of the town of Suplee along Grindstone and Twelvemile Creeks (Grindstone 

terrane) and northeast of Suplee (Begg Member of the Vester Formation, Izee terrane), Oregon (modified from 

Merriam and Berthiaume, 1943; and Buddenhagen, 1967). Stars indicate radiolarian collecting localities. 
8. GEOLOGIC IMPLICATIONS OF RADIOLARIAN-BEARING PALEOZOIC AND MESOZOIC ROCKS 83 

Coyote Butte Formation by Merriam and Berthiaume, 

1943), contained radiolarians largely correlative with 

those collected to the north of Grindstone Creek. Elements of this fauna include Pseudoalbaillella aff. P. 

globosa Ishiga, Kito, and Imoto, 1982b, P. longicornis 

Ishiga, Kito, and Imoto, 1982b (plate 8.1), Follicucullus 

aff. F. scholasticus Ormiston and Babcock, 1979, 

Albaillella asymmetrica Ishiga, Kito, and Imoto, 1982b, 

and Latentifistula cf. L. crux Nazarov and Ormiston, 

1983. A float sample ofblack chert ( 82CB-115; see fig. 8.2 

and locality descriptions) of Late Permian (late 

Guadalupian or Ochoan) age was also collected along 

the northwestern flank of Three Buttes and contained 

Neoalbaillella aff. N. grypus Ishiga, Kito, and Imoto, 

1982a, as well as open-faced, cross-axon forms (Latentibifistula) described by Takemura and N akaseko (1981). 

Chert and limestone clasts were collected from a 

block of coarse, chert-pebble conglomerate between 

Wade Butte and Grindstone Creek in the northeast 

corner of the Twelvemile Reservoir quadrangle. A distinct radiolarian fauna extracted from the black chert 

clasts (83CB-101A; see fig. 8.2 and locality descriptions) 

possessed simple spheroidal spumellarians which have 

yet to be described. This conglomerate locality corresponds closely to Merriam and Berthiaume's (1943) site 

21, which contained Permian fusulinids (Triticites) in 

limestone pods within the conglomerate. A previously 

collected chert sample from near Three Buttes (sample 

7 in Wardlaw and Jones, 1980) contained Early Triassic 

conodonts and radiolarians. 

According to Wardlaw and others (1982), most of the 

chert exposed near Three Buttes is of Triassic age. The 

abundant biostratigraphic data yielded by radiolarianbearing cherts near Three Buttes, as well as in other 

parts of the Grindstone terrane, indicate that the Grindstone cherts are mostly of Permian (late Wolfcampian or 

early Guadalupian and late Guadalupian or Ochoan) 

age. At present, the southern and western areal extent 

of the Grindstone terrane remains undefined. 

According to Dickinson and Thayer (1978), uplift 

and subsequent erosion of the Grindstone terrane 

provided all the detritus for the chert- and limestonerich conglomerates of the Begg Member of the Late 

Triassic Vester Formation (Izee terrane). If this interpretation were valid, one would expect most or all of the 

chert clasts within the Begg chert-pebble conglomerates to be of Permian age. However, as shown below, 

the Begg chert conglomerate contains radiolarians of 

Carboniferous age. 

IZEE TERRANE 

The Izee terrane contains a thick, mainly flyschoid 

sequence of clastic sedimentary rocks, along with subordinate limestones, and volcanic and volcaniclastic 

rocks, which range in age from Late Triassic (Karnian) 

through Middle Jurassic (Callovian). Complex stratigraphic relationships and local unconformities indicate 

tectonic instability during deposition. The terrane 

includes Upper Triassic turbidite sequences, with 

minor finer grained basinal deposits, that lie depositionally atop the Grindstone terrane. The northwardtrending Poison Creek fault divides the Upper Triassic 

and Lower Jurassic sedimentary rocks of the Izee terrane into two distinct stratigraphic units (fig. 8.3). 

Upper Triassic rocks west of the fault are represented by 

the Vester Formation, which includes the Begg and 

Brisbois Members, as well as the overlying Rail Cabin 

Argillite (Dickinson and Vigrass, 1965). The Rail Cabin 

Argillite was later renamed the Rail Cabin Mudstone by 

Blome (1984) and is herein revised as the Rail Cabin 

Mudstone Member of the Vester Formation. Triassic 

rocks east of the fault include the Late Triassic Fields 

Creek Formation and the Late Triassic(?) Laycock 

Graywacke of the Aldrich Mountains Group (Thayer and 

Brown, 1960). 

The Begg Member unconformably overlies the predominantly Paleozoic rocks of the Grindstone terrane 

and represents the oldest rocks within the Izee terrane. 

This unit is characterized by chert-grain sandstone, 

chert-pebble conglomerate, volcaniclastic rocks, and 

sedimentary breccia, intercalated with equal or greater 

amounts of mudstone and siltstone. The precise age of 

the Begg Member is not known, as only a sparse invertebrate fauna has been found in the unit thus far. The unit 

has been questionably assigned by Dickinson and Vigrass (1965) to the Karnian Stage, below the late 

Karnian Tropites subbullatus Zone of Smith (1927), 

although the basal part of the member could possibly 

extend down into the Middle Triassic. 

Clasts of black chert were collected from the Begg 

chert-pebble conglomerates along the southeast limb of 

the Little Bear anticline over a three-year period in the 

hope of determining both the age and provenance of the 

chert detritus. One sample (82CB-101A; see fig. 8.3 and 

locality descriptions) contained fragments of the radiolarian genus Latentifistula Nazarov and Ormiston, 

1983 (plate 8.2), as well as other undescribed taxa of the 

superfamily Latentifistulidea Nazarov and Ormiston, 

1983, and the family Entactiniidae Riedel, 1967. 

Although Latentifistula has a stratigraphic range of 

early Carboniferous (Mississippian) to Permian, the 

taxa from sample 82CB-101A are significantly different 

from Permian Latentifistulids collected in both the 

Grindstone and Baker terranes, and are therefore interpreted to be pre-Early Permian in age. Within the Begg 

conglomeratic beds, limestone blocks containing Mississippian and Permian fossils have also been reported 
84 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

0 10 1 5 2 0 

1 18° 4 5 . 

MILLER MOUNTAIN 

MELANGE AREA 

.. ../ ,..... .. 

25 KILOMETERS 

EXPLANATION 

WEST OF POISON CREEK FAULT 

D 

un.conformity 

fTI'TI'frn 

llillilil 

unconformity 

un-conformity 

~ 

uncon

~ ·form-ity 

Terrestrial sedl·mentary and 

volcanic rocks (Cenozoic) 

Bernard Formation 

(Cretaceous) 

Volcaniclastic and carbonate 

rocks (Upper Jurassic to 

Lower Jurassic) 

Vester For.matlon 

(U·pper Triassic) 

Mel'ange terrane 

(Upper Triassic to Paleozoic) 

EAST OF POISON CREEK FAU1. T 

D 

uncon·formity 

• unconformity 

unconformity 

Terrestrtal sedlmen.ta.ry and 

volcanic rocks (Cenozoic) 

V·olcanlclastlc and carbonate 

rocks (Upper Jur.a .aslc to 

Lower Juraas·lcl 

Aldrich Mountains Group 

(Lower J·ura11slc and 

Upper T·rlaaslc) 

Melange tena·ne 

(Upper Trl·asslc to Pa·leo.zolc} 

-- As map·ped, Includes .the 

ophiolitic U•pper Permian Canyo.n 

Mounta'l'n Complex. 

FIGURE 8.3.-Generalized geologic map of the John Day inlier both east and west ofthe Poison Creek fault (modified after 

Dickinson and Thayer, 1978). Star symbols indicate radiolarian collecting localities. 
8. GEOLOGIC IMPLICATIONS OF RADIOLARIAN-BEARING PALEOZOIC AND MESOZOIC ROCKS 85 

by Dickinson and Thayer (1978). Northwest of Suplee, 

Merlynd Nestell (written commun., 1983) reported wellpreserved Permian fusulinid faunas from redeposited 

limestone pods within the Begg conglomerates. 

All the radiolarian-bearing chert collected thus far 

from the Grindstone terrane has been of Permian age. 

The Carboniferous (or earliest Permian?) age of the 

single chert clast from the Begg conglomerates makes it 

doubtful that the Grindstone terrane to the west and 

southwest represents the only chert source for these 

chert-pebble conglomerates. 

The Brisbois Member of the Vester Formation consists of thin-bedded, gray to black siliciclastic sandstone 

and sandy calcarenite intercalated within a more abundant, thin-bedded, soft mudstone matrix. The calcarenite beds consist of shallow-water brachiopod, 

pelecypod, gastropod, and crinoid fragments and were 

interpreted by Dickinson and Vigrass (1965, p. 23) to be 

bioclastic in origin. Other pelecypods (Halobia sp.) and 

ammonites collected throughout this formation are 

regarded as being from displaced limestone blocks. The 

ammonites collected from the Brisbois Member are all 

indicative of the upper Karnian "Tropites subbullatus" 

Zone (Dickinson and Vigrass, 1965). Specimens of 

Halobia cf. H. ornatissima Smith, of late Karnian age, 

were reported by Blome (1984) from the upper part 

of the Brisbois Member (locality V177 in Dickinson and 

Vigrass, 1965) . 

The Rail Cabin consists predominantly of thinly 

bedded radiolarian-rich, dark-gray to black siliceous 

mudstones and cherts. Lenticular masses of gray-brown 

bioclastic limestone containing displaced shallow-water 

invertebrates occur sporadically throughout the unit. 

Minor amounts of thinly bedded, dark-gray to black 

(weathering to brown) calcilutites occur within its upper 

part. 

At the type locality of the Rail Cabin north of Morgan Mountain, a sharp lithologic break exists between 

the underlying Brisbois Member of the Vester Formation and the harder siliceous mudstones of the Rail 

Cabin. This contact was interpreted by Dickinson and 

Vigrass (1965, p. 28) to be unconformable because of the 

markedly divergent bedding attitudes exhibited above 

and below the contact at Graylocke Butte. 

The Rail Cabin is well exposed along the slopes of 

Morgan Mountain, located directly northwest of the 

town oflzee. Siliceous mudstone samples collected from 

110m (360ft) of section near Elkhorn Creek contained 

well-preserved radiolarian faunas of Late Triassic (late 

Karnian? ; early through late middle Norian) age 

(Blome, 1984). Although Dickinson and Vigrass (1965) 

interpreted the contact between the Brisbois Member of 

the Vester and the overlying Rail Cabin as being unconformable, a gradational contact was observed at this 

locality. Mudstones from the uppermost part of the Brisbois Member approximately one km southwest of Morgan Mountain contained radiolarian faunas essentially 

identical to those in the lower part of the Rail Cabin to 

the northeast (Blome, 1984). 

The lithostratigraphic and biostratigraphic evidence collected from the Brisbois and Rail Cabin indicates that the lower part of the Rail Cabin and the upper 

part of the Brisbois Member, especially south and west 

of Morgan Mountain, are sedimentary facies equivalents (Blome, 1984). On the basis of this facies equivalency, the Rail Cabin Mudstone is reduced in rank and 

assigned as the upper member of the Vester Formation. 

Additionally, a 110-m. (360-ft) section near Elkhorn 

Creek(U.S. Geological Survey lzee 15' quad. NW%SE V4 

sec. 14, T.17 S.', R. 27 E., west side ofunnamed drainage 

west of Elkhorn Creek) is herein designated as a reference section for the Rail Cabin. 

The predominantly siliceous Rail Cabin represents 

a period of pelagic sedimentation in a lower-slope depositional environment relatively free from terrigenous 

input. The minor occurrence of calcilutite (containing 

ammonites) in the upper part of the member may represent an intermittent lowering of the carbonate compensation depth (CCD). The partly contemporaneous, 

intertonguing Brisbois Member of the Vester Formation 

is interpreted as hemipelagic middle- and upper-slope 

deposits diluted by displaced calcarenite debris originally deposited in shallower water. 

East of the Poison Creek fault, the Triassic rocks 

include the Upper Triassic Fields Creek Formation and 

the Upper Triassic(?) Laycock Graywacke (fig. 8.3). The 

Fields Creek Formation rests unconformably on the 

Begg Member of the Vester Formation near the northern 

end of the Poison Creek fault (Dickinson and Thayer, 

1978). 

The Fields Creek Formation is characterized by 

massive beds of dark mudstone and minor intercalations of graded sandstone. The basal part of this formation is largely composed of slide blocks of various 

lithologies, presumably derived from the melange areas 

to the northwest (Dickinson and Thayer, 1978). 

Until recently, the only known fossils from the 

Fields Creek Formation were Norian megafossils from 

redeposited limestone blocks. These transported limestone blocks, collected from the basal part of the formation, contained middle or late Norian Halorella (Brown 

and Thayer, 1977). A siliceous mudstone sample 

(0R-123C; see fig. 8.3 and locality descriptions) collected from this olistostromal basal section contained a 

well-preserved radiolarian fauna (plate 8.3) of Late Triassic (early Karnian) age (Blome, 1984). This radiolarian fauna is identical to the radiolarian fauna from 

chert blocks in the Miller Mountain area near Vance 
86 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

Creek. The paleontologic evidence agrees with Dickinson and Thayer's (1978) concept that the basal part of the 

Fields Creek Formation represents tectonic blocks displaced from uplifted nearby melange areas, and it also 

indicates that melange formation continued in the Izee 

terrane until Late Triassic time. 

Other radiolarian-bearing mudstone samples 

(0R-123A,B; see locality descriptions) collected very 

near OR-123C, contained early Norian to late middle 

Norian radiolarian faunas essentially equivalent to 

those reported by Cheng (1982) from the stratigraphically higher middle and upper parts of the Fields 

Creek Formation. According to Dickinson and Thayer 

(1978, p. 156), the Vester Formation (Karnian and younger) was uplifted and contributed detritus to the thicker 

Aldrich Mountains Group (Norian and younger). The 

Norian age for the Fields Creek and the facies relationship established between the upper part of the Brisbois Member and the Rail Cabin Member west of the 

Poison Creek fault both suggest a different source for 

the Fields Creek detritus. 

The Laycock Graywacke conformably overlies the 

Fields Creek Formation and consists of a mixture of 

mudstone and graywacke, along with minor amounts 

of cherty sedimentary breccia and boulder conglomerate. The unit is unfossiliferous but is considered 

to be of Late Triassic(?) age because of its stratigraphic 

position beneath the Lower Jurassic Murderers Creek 

Graywacke. 

OLDS FERRY TERRANE 

The Olds Ferry terrane typically contains Upper 

Triassic mafic and intermediate volcanic and volcaniclastic rocks of the Huntington Formation described 

by Brooks (1979b), overlain by Lower Jurassic (and possibly uppermost Triassic) limestone and coarse-grained 

volcaniclastic rocks, and Lower and Middle Jurassic 

coarse- to fine-grained sedimentary rocks of the 

Weatherby Formation. According to Brooks (1979b), the 

varyingly metamorphosed Upper Triassic volcanic 

rocks are largely andesitic in composition but range 

from basalt to rhyolite. Except for rare pods of limestone, the interlayered sedimentary rocks are entirely 

volcaniclastic or tuffaceous. Ammonites and pectenacid 

bivalves (Halobia) of Late Triassic (late Karnian to middle Norian) age are known from widely scattered 

localities. Upper Triassic strata are associated with 

small bodies of quartz diorite or granodiorite, one of 

which yielded a U-Pb age of234 Ma (Walker, 1983). Generally faulted over these Upper Triassic rocks, but originally overlying them unconformably (and included 

within the Olds Ferry terrane), is the Jet Creek Member 

of the Weatherby Formation of Brooks (1979b). This 

member consists of shallow-marine limestone and gypsum and intercalated volcaniclastic conglomerate and 

sandstone of Early Jurassic (Sinemurian to late 

Pliensbachian) age. The rest of the Weatherby Formation is made up of Lower Jurassic (lower Sinemurian) 

and Middle Jurassic (lower Callovian) sandstone and 

argillite. 

Paleomagnetic data from the Upper Triassic 

basalts of the Olds Ferry terrane agree with those from 

Triassic rocks in the Wallowa terrane, both data sets 

indicating a paleolatitude of about 18° N. or S., as well as 

a large clockwise rotation (Hillhouse and others, 1982). 

Upper Triassic cherts (FR80-A to C; see fig. 8.4 and 

locality descriptions) of Elkhorn Ridge lithology containing Late Triassic (Karnian and Norian) radiolarians were collected 16 mi due west of the town of 

Huntington. According to Vallier and others (1977), outcrops of Elkhorn Ridge Argillite and Burnt River Schist 

appear locally within the area containing flyschlike 

rocks of the Olds Ferry terrane, either because they 

underlie part of the Olds Ferry and are exposed at structural windows, or because pieces of the oceanic Baker 

terrane were incorporated within the Olds Ferry as fault 

slices. Brooks and Vallier (1978, p.140) note the presence 

of serpentinite and chert clasts in the Jurassic 

Weatherby sandstones in the northern part of the Olds 

Ferry terrane. This evidence would indicate that the 

Baker terrane is a probable source of detritus for the 

juxtaposed Olds Ferry. 

BAKER TERRANE 

The Baker terrane is represented by disrupted late 

Paleozoic oceanic crustal blocks, associated deepmarine sedimentary rocks of late Paleozoic and Triassic 

age (for example, the Elkhorn Ridge Argillite), and 

tectonically mixed blocks of various rock types. Extensive zones of melange exist in the southwestern part of 

the terrane, whereas more coherent rock slices occur in 

the northwestern and eastern parts. Large bodies of 

highly deformed but lithologically coherent metamorphic and sedimentary rocks, such as the Burnt 

River Schist and Nelson Marble, are also present (Silberling and others, 1984). 

Lawsonite-bearing blueschist, associated with 

strongly sheared chert, quartzite, marble, and mafic 

metavolcanic rocks, are represented among the more 

western outliers of the Baker terrane in central Oregon. 

Near Mitchell, Oregon, these rocks have yielded an 

40 Ar _39 Ar age of about 223 Ma (Hotz and others, 1977). 

MILLER MOUNTAIN AREA 

Blocks of serpentinite, siliceous shale, chert, 

assorted metamorphosed (greenschist grade) clastic 
8. GEOLOGIC IMPLICATIONS OF RADIOLARIAN-BEARING PALEOZOIC AND MESOZOIC ROCKS 87 

• 

JOHN DAY 

EXPLANATION 

t ;J Flysch 

Q Central melange 

IITITTIJ Volcanic-arc assemblage 

0 25 

I 

5 0 K ILOM ETER S 

I 

FIGURE 8.4.-Distribution of pre-Tertiary volcanic-arc rocks, melange, and Jurassic flysch between John Day, Oregon, and the Snake River 

(modified after Vallier and others, 1977). Star symbols indicate radiolarian collecting localities. 

sedimentary rocks, greenstone, and varied volcaniclastic rocks make up a melange area in the Miller 

Mountain area, forming part of the Baker terrane. This 

melange is separated from the Canyon Mountain Complex (Brown and Thayer, 1966) by the Canyon Creek 

fault on the east and from the Aldrich Mountains Group 

of the Izee terrane by the Aldrich Mountain Fault (fig. 

8.3). The Canyon Mountain Complex, which is well 

exposed southeast of the town of John Day (Brown and 

Thayer, 1966; Ave Lallemant, 1976) represents the basement rocks for the melange (Vallier and others, 1977). 

The rocks in this melange area are largely 

unfossiliferous, particularly in its western part, but 

Early Permian fusulinids and middle Permian conodonts have been reported from limestone pods east and 

southeast of John Day (Dickinson and Thayer, 1978). 

Dickinson and Thayer (1978, p. 152) also reported Middle Triassic (late Ladinian) radiolarians in chert cropping out near Vance Creek. Black chert samples 

(0R68-71; see fig. 8.3 and locality descriptions), subsequently collected near Vance Creek, contained radiolarian faunas of similiar Middle (late Ladinian) or Late 

(early Karnian) Triassic age (Blome, 1984). These radiolarian faunas we now interpret to be of early Karnian 

age because of the presence of Gorgansium Pessagno 

and Blome (1980), a genus that makes its first 

appearance in the earliest part of the Karnian Stage. 

FRENCHY BUTTE AREA 

Composed almost entirely of serpentinite and metavolcanic rocks, the Frenchy Butte area is located north 

of the town of lzee, between the Fields Creek Formation 

(of the Aldrich Mountains Group) and the South Fork of 

the John Day River (fig. 8.3). Although unfossiliferous, 
88 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

this melange area was presumed by Dickinson and 

Thayer (1978) to be Permian and (or) Triassic in age. 

ROCKS NORTH OF MILLER MOUNTAIN AND FRENCHY 

BUTTE 

Chert similar to that in the Elkhorn Ridge Argillite 

occurs north of the Aldrich Mountains and northeast of 

the city of Mount Vernon. Samples of this chert 

(FR81-287 to -293; fig. 8.3 and locality descriptions) 

contained Late Triassic (early and middle Karnian) 

radiolarian faunas (plate 8.3). These faunas consist 

mainly of those taxa described by N akaseko and 

Nishimura (1979) and include Pseudostylosphaera helicatum, Triassocampe annulata, T japonica, and 

Yeharaia elegans, as well as ?Tripocyclia c£ T. acythus 

De Wever, 1979. This radiolarian assemblage differs 

slightly from the early Karnian fauna of the Miller 

Mountain melange area in that it contains abundant 

species of Yeharaia Nakaseko and Nishimura, 1979, a 

genus mostly restricted to Karnian age rocks. 

Directly east of Canyon City and just north of the 

ophiolitic Canyon Mountain Complex, chert samples 

were collected by Merlynd Nestell (Univ. of Texas, 

Arlington) from two separate chert blocks. One set of 

these samples (S-1, S-3, and S-6; fig. 8.3 and locality 

descriptions) contained Late Triassic (early to late middle Norian) radiolarian taxa (see Plate 8.3) identical to 

those from the uppermost part of the Brisbois and the 

Rail Cabin Mudstone Members of the Vester Formation 

and from the Fields Creek Formation (Blome, 1984). A 

short distance to the northwest, across Little Dog 

Creek, chert samples (P-1, P-3; see fig. 8.3 and locality 

descriptions) yielded a younger radiolarian faunal 

assemblage of latest Triassic (latest Norian) age. This 

distinctive faunal assemblage contained taxa incorporated in Yao and others (1982) Canoptum triassicum 

Assemblage Zone of latest Norian age, as well as elements of the Upper Triassic (upper Norian) Betraccium 

deweveri Subzone described by Blome (1984). Nassellarians similar to Jurassic (Hettangian) forms 

described by Pessagno and Whalen (1982) were also 

present. 

EASTERN PART OF THE BAKER TERRANE 

Late Paleozoic and early Mesozoic rocks in the eastern part of the Baker terrane near Baker, Oregon, 

include abundant chert, argillite, and siliceous tuff and 

rare coarse-grained sedimentary rocks. Incorporated in 

this part of the terrane are argillite, chert, tuff, and 

limestone of the Elkhorn Ridge Argillite (fig. 8.3), thinlayered phyllitic quartzite, greenstone, and marble of 

the Burnt River Schist (Gilully, 1937), and basalt flows 

and volcaniclastic rocks. Most of this terrane has undergone severe structural deformation and metamorphism 

(greenschist to amphibolite facies), and in many areas it 

is structurally intermixed with plutonic bodies. 

To the north and northeast, the Baker terrane is 

bounded by Lower Permian and Middle and Upper Triassic metavolcanic and volcaniclastic rocks, which are 

overlain by Upper Triassic and Lower Jurassic carbonate rocks and clastic sequences of the Wallowa terrane 

(Silberling and others, 1984; fig. 8.1). Late Permian 

through Middle Triassic sedimentary rocks are absent 

in the Wallowa terrane. 

The Elkhorn Ridge Argillite was named by Gilully 

(1937) for a thick succession (565 m) of argillite, tuff, 

chert and minor amounts of limestone and greenstone 

expo;ed on Elkhorn Ridge, which trends northwestsoutheast and lies mostly within the Elkhorn Peak 

quadrangle (Baldwin, 1979). The major part of the 

Elkhorn Ridge Argillite is of Permian age, but it ranges 

from Middle Pennsylvanian to Late Triassic in overall 

age. Permian fusulinids have been reported both by 

Pardee and Hewett (1914) and by Bostwick and Koch 

(1962), who state that the fusulinid-bearing limestone 

pods within the Elkhorn Ridge Argillite correlate, at 

least in part, with the Coyote Butte Formation, which 

forms part of the Grindstone terrane of Silberling and 

others (1984). Bostwick and Koch (1962) also report Late 

Permian fusulinids from limestone pods east of Baker. 

Bostwick later reported Middle Pennsylvanian 

(Desmoinesian) fusulinids and Triassic(?) hexacorals 

from rocks mapped as the Elkhorn Ridge Argillite 

(Brooks and others, 1976). 

The geology due west of the town of Baker, near 

Elkhorn Ridge in the Bourne quadrangle, is characterized by a metamorphosed Paleozoic igneous complex 

containing mostly gabbro, but with lesser amounts of 

diorite, quartz diorite, and contemporaneous metavolcanic rocks composed of basaltic lava flows and volcaniclastic rocks (Brooks and others, 1982). Metamorphosed sedimentary rocks in this area include the 

Elkhorn Ridge Argillite (Gilully, 1937), comprising dark 

argillite and chert with minor amounts of limestone, 

tuff, sandstone, and conglomerate . Siliceous rocks 

range from soft argillite to hard, indurated, uniformly 

bedded chert. 

Metacherts collected from the Elkhorn Ridge 

Argillite near Elkhorn Ridge in the Bourne quadrangle 

(83CB-110 to -112; see fig. 8.4 and locality descriptions) 

were all barren of radiolarians, probably because of 

metamorphism related to emplacement of the Late 

Jurassic and Early Cretaceous Bald Mountain batholith. Other chert samples collected by Howard Brooks 

(Oregon Department of Mineral Industries, written 

commun., 1983) produced the same negative results. 

Although further collecting may be warranted, the pos-
8. GEOLOGIC IMPLICATIONS OF RADIOLARIAN-BEARING PALEOZOIC AND MESOZOIC ROCKS 89 

sibility of obtaining datable radiolarians from the 

cherts near Elkhorn Ridge seems doubtful. Brooks and 

others (1982) note that Pennsylvanian, Permian, and 

Triassic fossils have all been found in the Elkhorn Ridge 

Argillite outside the Bourne quadrangle. 

Farther west of Elkhorn Ridge, in the Bates and 

Greenhorn quadrangles, crustal rocks include Permian 

and Triassic(?) serpentinite, serpentinized melange, 

metamorphosed gabbro and diorite, as well as Permian 

greenstones, pillow basalts, tuffs, volcaniclastic rocks, 

conglomerate, and breccia (Ferns and others, 1983). 

These, like similar rocks to the east, are associated with 

the sedimentary rocks of the Elkhorn Ridge Argillite, 

and also with the clastic sedimentary sequence, unit 

"TrPa" of Ferns and others (1983). The "TrPa" unit contains argillite, siltstone, and sandstone, with minor 

amounts of conglomerate, chert, and limestone and differs from the Elkhorn Ridge Argillite by possessing 

more coarse clastic detritus, as well as being less siliceous. 

Permian to Triassic age fossils have been reported 

from the Elkhorn Ridge Argillite within the Greenhorn 

quadrangle (Ferns and others, 1983), and in the Bates 

quadrangle in the sequence mapped as "TrPa". The 

fossils include both Early Permian (Leonardian) conodonts along with Early Permian (Wolfcampian) 

fusulinids from limestone blocks (Mullen, 1978). Ferns 

and others (1983) acknowledge the possibility that these 

Early Permian fossils may be exotic to the "TrPa" unit 

and were derived from the underlying melange by 

redeposition of limestone blocks. 

Chert samples collected from the Greenhorn quadrangle were all barren of radiolarians, with the exception of a float pebble (78SG-03; see fig. 8.4 and locality 

descriptions) collected by N.J. Silberling near Olive 

Creek in the northwestern corner of the quadrangle. 

This float sample contained an early Late Permian 

(Guadalupian) radiolarian fauna characterized by Follicucullus scholasticus Ormiston and Babcock, 1980, 

and Follicucullus ventricosus Ormiston and Babcock, 

1980. Other samples collected from well-bedded green 

and black chert nearby (83CB-120A-C; see fig. 8.4 and 

locality descriptions) were all barren of radiolarians and 

the provenance of Silberling's float sample remains 

unknown. 

A chert sample (83CB-117; fig. 8.4 and locality 

descriptions) collected from outcrops in a gravel pit 

along Granite Boulder Creek in the central part of the 

Bates quadrangle contained early Late Permian 

(Guadalupian) radiolarians almost identical to those 

from Silberling's pebble locality. Characteristic taxa 

include Follicucullus scholasticus Ormiston and Babcock, 1980, Follicucullus ventricosus Ormiston and Babcock, 1980, and Pseudoalbaillella cf. P sakmarensis 

(Kozur) 1982. In addition, another chert sample 

(83HB-703; see fig. 8.4 and locality descriptions) collected by Howard Brooks from the southwestern part of 

the Bates quadrangle (Brooks and others, 1984) yielded 

well-preserved early Late Permian (Guadalupian) radiolarians. Characteristic taxa again include Follicucullus scholasticus Ormiston and Babcock, 1980, 

and F ventricosus Ormiston and Babcock, 1980, as well 

as undescribed Pseudoalbaillella sp. 

The Permian age given by these radiolarian faunas 

and by the conodonts and fusulinids in the limestones 

disagree with those implied by the correlations of Brown 

and Thayer (1966b ). They also suggest that the blocks of 

Permian limestone are probably indigenous to the 

"TrPa" unit and not reworked from the underlying 

melange. 

South ofElkhorn Ridge, in the northeastern corner 

of the Beaverdam Creek quadrangle, a sample (BD-816; 

see fig. 8.4 and locality descriptions) of chert collected by 

Robert Coward yielded a poorly preserved radiolarian 

fauna containing Canoptum(?) analatum Pessagno and 

Poisson, 1979, and Canoptum sp. (Emile Pessagno, written commun., 1983). According to Pessagno and Whalen 

(1982) and Whalen (written commun., 1983), the multichambered Canoptum anulatum species group ranges 

in age from the very latest Norian through the Early 

Jurassic (late Pliensbachian or Toarcian). Multichambered species of Canoptum have also been reported by 

Yao and others (1982) from latest Triassic rocks in 

Japan. 

East of Baker, isolated blocks of metamorphosed 

chert and limestone occur in the eastern half and northwestern quarter of the Oxman quadrangle. Although 

both the chert and limestone occur as individual blocks 

of varied sizes, they do form an arcuate belt extending 

northeast to southwest, which is in agreement with the 

regional structural trend suggested by Vallier and others (1977, p. 461). 

In the more metamorphosed eastern part of the 

Baker terrane, cherts exhibit varying metamorphic 

grades, and some are distinctly foliated. The Elkhorn 

Ridge Argillite and Burnt River Schist are both very 

quartz-rich, but the latter unit has undergone a higher 

degree of metamorphism. Ashley (1967) proposed that 

the quartz-rich phyllites in the Burnt River Schist may 

have been derived from metamorphosed fragments of 

the Elkhorn Ridge Argillite. Metamorphosed cherts in 

the Oxman quadrangle represent another likely protolith for the phyllites of the Burnt River Schist. 

Black chert ( 83CB-1 07 A, B; see fig. 8.4 and locality 

descriptions) collected from the northwestern part of 

the Oxman quadrangle north of Second Creek contained age-diagnostic Permian (late Leonardian?; 

Guadalupian) radiolarians. Typical Guadalupian taxa 
90 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

include Follicucullus scholasticus Ormiston and Babcock, 1980, F. aff. F. ventricosus Ormiston and Babcock, 

1980, and ? Pseudoalbaillella cf. P. sakmarensis (Kozur) 

1982. Well-preserved Permian fusulinids were recently 

collected from nearby limestone pods by Merlynd 

Nestell (written commun., 1983). 

Poorly preserved radiolarian faunas of Late Triassic 

(early to middle Norian) age were extracted from cherts 

(83CB-102, -103A,B, and -104; see fig. 8.4 and locality 

descriptions) collected in the eastern half of the Oxman 

quadrangle. Late Triassic genera include Capnodoce 

De Wever, 1979, and Xipha Blome, 1984. The Permian 

and Triassic radiolarian data, although preliminary, 

indicates a younging from west to east within the suggested northeast-southwest structural belt. 

CONCLUSIONS 

Radiolarian biostratigraphy has established that 

cherts from the Grindstone terrane are Permian (late 

Wolfcampian to late Guadalupian or Ochoan) in age. In 

the Baker terrane, Late Triassic (early Karnian) cherts 

occur in the Miller Mountain area and represent a 

southwestern extension of the Elkhorn Ridge Argillite. 

Other Baker terrane cherts near John Day range in age 

from Karnian to latest Norian and some may be as 

young as earliest Jurassic (Hettangian). Cherts typical 

of the Elkhorn Ridge Argillite near Baker are of both 

Permian (Leonardian to Guadalupian) and Late Triassic (Karnian to latest Norian) ages, and one sample 

may possibly be as young as Early Jurassic. 

The Miller Mountain and Frenchy Butte melange 

areas should be placed within the Baker terrane for the 

following reasons: (1) Both these areas possess volcanogenic rock assemblages of greenschist metamorphic grade similiar to volcanic assemblages of the 

Baker terrane and (2) Late Triassic (Karnian) radiolarian faunas from the Miller Mountain area are 

nearly identical to those from the southwestern extension of the Elkhorn Ridge Argillite east and west of John 

Day. 

Although equivalent-age Permian (Leonardian and 

Guadalupian) cherts occur in both the Grindstone and 

Baker terranes, the Grindstone terrane has no Middle 

or Upper Triassic cherts, generally lacks volcanic and 

volcaniclastic rocks, and also has a lower regional metamorphic grade. These differences indicate that the 

Grindstone terrane represents a separate tectonic block 

from the Baker terrane. 

The Grindstone terrane may not be the sole chert 

source for the Karnian-age Begg conglomerates of the 

Izee terrane. The only dated chert clast from the Begg 

Member is Carboniferous or earliest Permian, an age 

unrepresented in either the Grindstone or the Baker 

terrane. The Late Triassic age for chert in the Miller 

Mountain melange area, and the Late Permian and Late 

Triassic ages for the rest of the Baker terrane chert 

appear to preclude the Baker terrane from being a 

source for Begg chert detritus. 

Correlation of radiolarian faunas shows that the 

upper part of the Brisbois Member of the Vester Formation is locally a facies equivalent of the lower part of the 

heretofore-designated Rail Cabin Mudstone. The Rail 

Cabin has subsequently been revised herein as the 

upper member of the Vester Formation. 

Identical Late Triassic (early. Karnian) radiolarian 

faunas from both the olistostromal basal part of the 

Fields Creek Formation (lzee terrane) and the Miller 

Mountain melange area (Baker terrane) substantiate 

the interpretation that redeposited blocks in the basal 

part of the Fields Creek were derived from the Baker 

terrane to the north. 

Late Triassic (late Karnian to middle Norian) 

radiolarian cherts collected from the Brisbois Member 

of the Vester Formation, the Rail Cabin Mudstone Member, and the Fields Creek Formation are coeval, indicating that the Fields Creek detritus could not have been 

derived from the uplift and erosion of the Vester Formation as was originally suggested. 

The age of the Elkhorn Ridge Argillite in the Baker 

terrane is extended up to at least latest Triassic time by 

the discovery of latest Triassic and possibly Early 

Jurassic radiolarian faunas in cherts near John Day and 

east of Baker. The Baker terrane thus contains rocks 

slightly younger than the Triassic siliciclastic rocks of 

the Izee terrane. 

Chert clasts in the Jurassic sandstones of the 

Weatherby Formation in the northern part of the Olds 

Ferry terrane, west of the town of Huntington, are of 

Elkhorn Ridge lithology and yield Late Triassic (Karnian and Norian) radiolarian faunas. This indicates that 

the Elkhorn Ridge Argillite and associated units in the 

Baker terrane may have provided some of the detritus 

for the Weatherby Formation, in much the same manner 

as the Frenchy Butte and Miller Mountain melange 

areas of the Baker terrane provided detritus for the 

Fields Creek Formation and possibly the Vester Formation in the Izee terrane. 

Radiolarian biostratigraphy has shown that the 

Baker terrane contains cherts of Permian, Late Triassic, 

and possible Early Jurassic age. These are therefore, 

essentially coeval with the Permian and Triassic metavolcanic and volcaniclastic rocks, and the Late Triassic 

and Early Jurassic carbonate and clastic sequences of 

the Wallowa terrane to the north and northwest. 

LOCALITY DESCRIPTIONS 

78SG-03 (USGS MR 0515). Float block of dark green 

chert from the Elkhorn Ridge Argillite, Baker ter-
8. GEOLOGIC IMPLICATIONS OF RADIOLARIAN-BEARING PALEOZOIC AND MESOZOIC ROCKS 91 

rane. Sample collected by Norm J. Silberling (USGS, 

Denver). USGS Greenhorn quad. (7.5'): T. 9 S., R. 35 

E., SE1/4SW% sec. 35, west side of road, in creek 

debris. 

82CB-101A(USGSMR4578). Blackchertclastcollected 

from chert pebble conglomerate of the Begg Member 

of the Vester Formation. USGS Suplee quad. (7.5'): T. 

17 S., R. 26 E., NW%NElf4 sec. 20, east side of Bull 

Creek. 

82CB-105A-C (USGS MR 4591-4593). Red chert in 

Grindstone terrane. USGS Delintment Lake quad. 

(15'): T.18 S., R. 25 E., SW%SW%cornersec. 27, north 

side of unnamed reservoir. 

82CB-106A-D (USGS MR 4596-4599). Red chert in 

Grindstone terrane. USGS Suplee quad. (7.5'): T. 18 

S., R. 25 E., NW%SE% sec. 11, top ofbutte. 

82CB-108A-D (USGS MR 4605-4608). Green chert in 

Grindstone terrane. USGS Suplee quad. (7.5'): T. 18 

S., R. 25 E., SE%NW% sec. 10, top ofbutte. 

82CB-109A-C (USGS MR 4609-4611). Green tuff bed 

from cherty breccia in Grindstone terrane. USGS 

Delintment Lake quad. (15'): T. 18 S., R. 25 E., 

NW%NW% sec. 27. 

82CB-111A,B (USGS MR 4613-4614). Thinly bedded red 

chert in Grindstone terrane. USGS Delintment Lake 

quad. (15'): T. 18 S., R. 25 E., SW%SE1/4 sec. 21. 

82CB-114A-C (USGS MR 4619-4621). Red chert in the 

Grindstone terrane. USGS Twelvemile Reservoir 

quad. (7.5'): T. 19 S., R. 25 E., NW1/4NWlf4 sec. 17, 0.2 

mi NE.of eastern extension of Three Buttes. 

82CB-115 (USGS MR 4622). Black chert float in the 

Grindstone terrane. USGS Twelvemile Reservoir 

quad. (7.5'): T. 19 S., R. 25 E., SW%NE% sec. 18, 

northern flank of Three Buttes. 

83CB-101A (USGS MR 4084). Black chert pebbles from 

chert pebble conglomerate, Grindstone terrane. 

USGS Twelvemile Reservoir quad. (7.5'): T. 18 S., R. 

24 E., SW%NElf4 sec. 25, approximately same location 

as Merriam and Berthiaume's loc. 21. 

83CB-103A,B (USGS MR 4086 and 4087 respectively). 

Light green chert interbedded with light brown tuff, 

from the Elkhorn Ridge Argillite, Baker terrane. 

USGS Oxman quad. (7.5'): T.10 S., R. 42 E., NE1/4NE% 

sec. 26, farthest east fork of Holman Creek. 

83CB-104 (USGS MR 4088). Thinly bedded, dark green 

chert from the Elkhorn Ridge Argillite, Baker terrane. USGS Oxman quad. (7.5'): T. 10 S., R. 42 E., 

SW%NE% sec.11, along north fork ofPritchard Creek. 

83CB-107A,B (USGS MR 4092 and 4093 respectively). 

Green and black chert from the Elkhorn Ridge 

Argillite, Baker terrane. USGS Oxman quad. (7.5'): T. 

9 S., R. 42 E., NE%NWlf4 sec. 33, approx. 450ft south 

of the boundary between sees. 28 and 33. 

83CB-110-112 (USGS MR 4096 to 4098 respectively). 

Black siliceous mudstone samples from the Elkhorn 

Ridge Argillite in the Baker terrane. USGS Bourne 

quad. (7.5'): T. 9 S., R. 37 E., NW%NW% sec. 30, south 

side of sharp bend in road. 

83CB-117 (USGS MR 4111). Black chert samples from 

the Elkhorn Ridge Argillite (or unit "TrPa" of Ferns 

and others, 1983), Baker terrane. USGS Bates quad. 

(15'): T.10 S., R. 34 E., NE%NE% sec. 32, north end of 

gravel pit. 

83CB-120A-C (USGS MR 4116 to 4118 respectively). 

Green chert samples from the Elkhorn Ridge 

Argillite, Baker terrane. USGS Greenhorn quad. 

(7.5'): T. 9 S., R. 35 E., SE%SW% sec. 35, east side of 

road. 

BD-816. Thin-bedded black chert from northwesttrending chert block, Baker terrane. USGS Beaverdam Creek quad. (7.5'): T. 11 S., R. 38 E., SW%SW% 

sec. 14, directly north of Big Creek and dirt road. 

FR80-A-C (USGS MR 2804 to 2806 respectively). Samples from chert blocks in Jurassic flysch, Olds Ferry 

terrane. Collected by Francois Roure. USGS 

Bridgeport quad. (15'): T.14 S., R. 42 E., northern half 

of boundary between sees. 14 and 15. 

FR81-287-293 (USGS MR 2819 to 2824). Chert in the 

Elkhorn Ridge Argillite, Baker terrane. Collected by 

FrancoisRoure. USGSMt. Vernon quad. (15'): T.12 S., 

R. 30 E., SW1/4SW% sec. 6, west side ofU.S. Route 395. 

83HB-703 (USGS MR 4406). Black chert from the 

Elkhorn Ridge Argillite. USGS Bates quad. (15'): T.12 

S., R. 34 E., SW% sec. 9, east side of Dads Creek road. 

OR-123A-C. Samples from a chert block near the base 

of the Fields Creek Formation, Izee terrane, along 

Fields Creek road, approximately 11.3 miles south of 

the intersection of Hwy. 26 and Fields Creek Road. 

USGS Aldrich Mt. quad. (15'): T. 14 S., R. 29 E., 

SE%NElf4 sec. 5. 

OR68-71. Black chert in the Miller Mountain melange 

area, now considered part of the Baker terrane. USGS 

Mt. Vernon quad. (15'): T. 14 S., R. 30 E., NE1/4SW% 

sec. 5, approximately 0.2 miles north of Vance Creek. 

P-1 and P-3 (USGS MR 2536 and 2538 respectively). 

Samples collected from a block of chert resembling 

the Elkhorn Ridge Argillite, Baker terrane. Samples 

collected by Merlynd Nestell. USGS John Day quad. 

(7.5'): T. 3 S., R. 32 E., NW%NW% sec. 32, directly 

south of road leading due west from Little Dog Creek. 

S-1, S-3, and S-6 (USGS MR 2550, 2552, and 2555 

respectively). Samples collected from a block of chert 

resembling the Elkhorn Ridge Argillite, Baker terrane. Samples collected by Merlynd Nestell. USGS 

John Day quad. (7.5'): T. 13 S., R. 32 E., NE%SE% sec. 

32, east of road along Little Dog Creek. 

REFERENCES CITED 

Ashley, R.P., 1967, Metamorphic petrology and structure of the Burnt 

River Canyon area, northeastern Oregon: Stanford Calif, Stan-
92 GEOLOGIC IMPLICATIONS OF PALEONTOLOGY AND BIOSTRATIGRAPHY, BLUE MOUNTAINS PROVINCE 

ford University, unpublished Ph.D. thesis, 193 p. 

Ave Lallemant, H.G., 1976, Structure of the Canyon Mountain 

(Oregon) ophiolite complex and its implication for sea-floor 

spreading: Geological Society of America Special Paper 173, 49 p. 

Baldwin, E.M., 1979, Carboniferous formations in Oregon, in The 

Mississippian and Pennsylvanian (Carboniferous) Systems in 

the United States: U.S. Geological Survey Professional Paper 

1110-CC,p.CC37-CC41. 

Blome, C.D., 1983, Upper Triassic Capnuchosphaeridae and Capnodocinae (Radiolaria) from east-central Oregon: Micropaleontology, v. 29, no.1, p. 11-49, 11 pis. 

---1984, Upper Triassic Radiolaria and Radiolarian zonation from 

western North America: Bulletins of American Paleontology, v. 

85, no. 318, p. 1-88, 17 pls. 

Blome, C.D., and Irwin, W.P., 1983, Tectonic significance oflate Paleozoic to Jurassic radiolarians from the North Fork Terrane, 

Klamath Mountains, California, in Stevens, C.H., ed., PreJurassic Rocks in western North American Suspect Terranes: 

Society of Economic Paleontologists and Mineralogists, p. 77-89, 

1 pl. 

---1985, Equivalent radiolarian ages from ophiolitic terranes of 

Cyprus and Oman: Geology, v. 13, p. 401-404. 

Bostwick, D.A., and Koch, G.S., 1962, Permian and Triassic rocks of 

northeastern Oregon: Geological Society of America Bulletin, v. 

73, p. 419-422. 

Brooks, H. C., 1979a, Plate tectonics and the geologic history of the 

Blue Mountains: Oregon Geology, v. 41, no. 5, p. 71-80. 

---1979b, Geologic map of the Huntington and part of the Olds 

Ferry quadrangles, Baker and Malheur Counties, Oregon: 

Oregon Department of Geology and Mineral Industries Geological Map Series GMS-13, scale 1:62,500. 

Brooks, H.C., Ferns, M.L., and Avery, D.G., 1984, Geology and Gold 

deposits map of the southwest quarter of the Bates quadrangle, 

Grant County, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series, GMS 35. 

Brooks, H.C., Ferns, M.L., Coward, R.I., Paul. E.K., and Nunlist, M., 

1982, Geology and gold deposits of the Bourne quadrangle, Baker 

and Grant Counties, Oregon: Oregon Department of Geology 

and Mineral Industries Geological Map Series GMS-19, scale 

1:24,000. 

Brooks, H.C., Mcintyre, J.R., and Walker, G.W., 1976, Geology ofthe 

Oregon part of the Baker 1 o by 2o quadrangle: Oregon Department of Geology and Mineral Industries Geological Map Series 

GMS-7, 29 p., map scale 1:250,000. 

Brooks, H.C., and Vallier, T.L., 1978, Mesozoic rocks and tectonic 

evolution of eastern Oregon and western Idaho, in Howell, D.G., 

and McDoug~ll, K.A., eds., Mesozoic paleogeography of the Western United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Paleogeography Symposium 2, p. 

133-145. 

Brown, C.E., and Thayer, T.P., 1966a, Geologic map of the Mount 

Vernon quadrangle, Grant County, Oregon: U.S. Geological Survey Geologic Quadrangle Map GQ-548, scale 1:62,500. 

---1966b, Geologic map of the Canyon City quadrangle, northeastern Oregon: U.S. Geological Survey Miscellaneous Geological Investigations Map 1-447, scale 1:250,000. 

---1977, Geologic map of pre-Tertiary rocks in the eastern Aldrich 

Mountains and adjacent areas to the south, Grant County, 

Oregon: U.S. Geological Survey Miscellaneous Investigations 

Map 1-1021, scale 1:62,500. 

Buddenhagen, H.J., 1967, Structure and orogenic history of the southwestern part of the John Day uplift, Oregon: Ore Bin, v. 29, p. 

129-138. 

Cheng, KY., 1982, Upper Triassic Radiolaria from the Fields Creek 

Formation, John Day inlier, east-central Oregon: University of 

Texas at Dallas, Masters thesis, 80 p., 9 pis. 

Cornell, W.C., and Simpson, R.D., 1985, New Permian albaillellid 

radiolarians from West Texas: Micropaleontology, v. 31, no. 3, p. 

271-279,1 pl. 

De Wever, Patrick, Sanfillipo, Annika, Riedel, W.R., and Gruber, 

Bernhard, 1979, Triassic radiolarians from Greece, Sicily and 

Turkey: Micropaleontology, v. 25, no.1, p. 75-110. 

Dickinson, W.R., 1979, Mesozoic forearc basin in central Oregon: 

Geology, v. 7, p.166-170. 

Dickinson, W.R., and Thayer, T.P., 1978, Paleogeographic and paleotectonic implications of Mesozoic stratigraphy and structure in the 

John Day Inlier of central Oregon, in Howell, D.G., and 

McDougall, K.A., eds., Mesozoic paleogeography of the Western 

United States: Pacific Section, Society of Economic Paleontologists and Mineralogists, Pacific Coast Paleogeography Symposium 2, p. 147-161. 

Dickinson, W.R., and Vigrass, L.W., 1965, Geology of the Suplee-Izee 

area, Crook, Grant, and Harney Counties, Oregon: Oregon 

Department of Geology and Mineral Industries Bulletin 58, 109 

p. 

Ferns, M.L., Brooks, H.C., and Avery, D.G., 1983, Geology and gold 

deposits map of the Greenhorn quadrangle, Baker and Grant 

counties, Oregon: Oregon Deptartment of Geology and Mineral 

Industries Geological Map Series GMS-28, scale 1:24,000. 

Gilluly, James, 1937, Geology and mineral resources of the Baker 

Quadrangle, Oregon: U.S. Geological Survey Bulletin 879,119 p. 

Hotz, P.E., Lanphere, M.A., and Swanson, D.A., 1977, Triassic blueschist from northern California and north-central Oregon: 

Geology, v. 5, no. 11, p. 659-663. 

Hillhouse, J.W., Gromme, C.S., and Vallier, T.L., 1982, Paleomagnetism and Mesozoic tectonics of the Seven Devils volcanic arc, 

northeastern Oregon: Journal of Geophysical Research, v. 87, no. 

B-5, p. 3777-3794. 

Holdsworth, B.K., and Jones, D.L., 1980, Preliminary radiolarian 

zonation for Late Devonian through Permian time: Geology, v. 8, 

no. 6, p. 281-285. 

Ishiga, Hiroaki, Kito Takeo, and Imoto, Nobuhiro, 1982a, Late Permian radiolarian assemblages in the Tamba district and an 

adjacent area, Southwest Japan: Earth Science (Chikyu 

Kagaku; Journal of the Association for the Geological collaboration in Japan), v. 36, no. 1, p. 10-22. 

---1982b, Middle Permian radiolarian assemblages in the Tamba 

district and an adjacent area, Southwest Japan: Earth Science 

(Chikyu Kagaku; Journal of the Association for the Geological 

collaboration in Japan), v. 36, no. 5, p. 272-281. 

---1982c, Permian radiolarian biostratigraphy: News of Osaka 

Micropaleontologist, Special Volume 5 (Proceedings of First 

Radiolarian Symposium), p. 17-26. 

Jones, D.L., Silberling, N.J., and Hillhouse, J., 1977, Wrangellia-A 

displaced terrane in northwestern North America: Canadian 

Journal of Earth Sciences, v. 14, no. 11, p. 2565-2577. 

Kleweno, W.P., Jr., and Jeffords, R.M., 1961, Devonian rocks in the 

Suplee area of central Oregon [abs.], in Abstracts for 1961: Geological Society of America Special Paper 68, p. 34-35. 

Kozur, H., and Mostler, H., 1862, Beitrage zur Erforschung der mesozoichen Radiolarien. Teil IV. Thalassosphaeracea Haeckel1862, 

Hexastylacea Haeckel, 1882, emend., und weitere triassische 

Lithocycliacea, Trematodiscacea, Actinommacea und Nassellaria: Geologische Palaontologische Mitteiliugen Innsbruck 

Sonderband, p. 208 p. 69 pls. 

Merriam, C.W., and Berthiaume, S.A., 1943, Late Paleozoic formations 

of central Oregon: Geological Society of America Bulletin, v. 54, 

no. 2, p.145-171. 

Muller, J.E., 1977, Evolution of the Pacific margin, Vancouver Island, 

and adjacent regions: Canadian Journal of Earth Science, v. 14, 
8. GEOLOGIC IMPLICATIONS OF RADIOLARIAN-BEARING PALEOZOIC AND MESOZOIC ROCKS 93 

no. 9,~ 2062-2085. 

Nakaseko, Kojiro, and Nishimura, Akiko, 1979, Upper Triassic Radiolaria from Southwest Japan: Science Report, College of Education, Osaka Univ., v. 29, no. 2, p. 61-109. 

Nazarov, B.B., and Ormiston, A.R., 1983, A new superfamily of 

stauraxon polycystine Radiolaria from the Late Paleozoic of the 

Soviet Union and North America: Senckenbergiana Lethaea, v. 

64, p. 363-379, 1 pl. 

---1985, Radiolaria from the Late Paleozoic of the Southern Urals 

and west Texas, USA: Micropaleontology, v. 31, no. 1, p. 1-54, 6 

pls. 

Ormiston, Allen, and Babcock, Laurel, 1979, Follicucullus, new radiolarian genus from the Guadalupian (Permian) Lamar Limestone of the Delaware Basin: Journal of Paleontology, v. 53, no. 2, 

p. 328-334, 1 pl. 

Pardee, J.T., and Hewett, D.F., 1914, Geology and mineral resources of 

the Sumpter quadrangle, Oregon: Oregon Bureau of Mines and 

Geology, Mineral Research of Oregon, v. 1, no. 6, p. 3-128. 

Pessagno, E.A., Jr., and Blome, C.D., 1980, Upper Triassic and 

Jurassic Pantanellinae from California, Oregon, and British 

Columbia: Micropaleontology, v. 26, no. 3, p. 225-273, 11 pls. 

Pessagno, E.A., Jr., and Poisson, Andre, 1979, Lower Jurassic Radiolaria from the Gumuslu allochthon of southwestern Turkey 

(Taurides Occidentales): Mineral Research and Exploration 

Institute ofTurkey Bulletin, no. 92, p. 47-69, 15 pls. 

Pessagno, E. A., Jr., and Whalen, P. A., 1982, Lower and Middle 

Jurassic Radiolaria (multicyrtid Nassellariina) from California, 

east-central Oregon, and the Queen Charlotte Islands, B.C.: 

Micropaleontology, v. 28, no. 2, p. 111-169, 13 pls. 

Riedel, W.R., 1967, Class Actinopoda Calkins 1909, in Harland, W.B., 

ed., The Fossil Record: London, Geological Society of London, p. 

291-298. 

Silberling, N.J., Jones, D.L., Blake, M.C., Jr., and Howell, D.G., 1984, 

Lithotectonic terrane map of the western conterminous United 

States, in Silberling, N.J., and Jones, D.L., eds., Lithotectonic 

terrane maps of the North American Cordillera: U.S. Geological 

Survey Open-File Report 84-523 Map, part C, 43 p. 

Smith, J.P., 1927, Upper Triassic marine invertebrate faunas of North 

America: U.S. Geological Survey Professional Paper 141, p. 

1-262, 121 pls. 

Takemura, Atsushi, and Nakaseko, Kojiro, 1981, A new Permian radiolarian genus from the Tamba Belt, southwest Japan: Transactions and Proceedings of the Paleontological Society of Japan, 

new series, no. 124, p. 208-214, 2 pls. 

Taubeneck, W.H., 1955, Age of the Elkhorn Ridge argillite, northeastern Oregon: Northwest Science, v. 29, no. 3, p. 97-100. 

Thayer, T.P., and Brown, C.E., 1960, Upper Triassic graywackes and 

associated rocks in the Aldrich Mountains, Oregon: U.S. Geological Survey Professional Paper 400-B, p. B300-B302. 

---1966, Geologic map of the Aldrich Mountain quadrangle, Grant 

County, Oregon: U.S. Geological Survey Geologic Quadrangle 

Map GQ-438, scale 1:62,500. 

Vallier, T.L., Brooks, H.C., and Thayer, T.P., 1977, Paleozoic rocks of 

eastern Oregon and western Idaho, in Stewart, J.H., and others, 

eds., Paleozoic paleogeography of the Western United States: 

Pacific Section, Society of Economic Paleontologists and 

Mineralogists, Pacific Coast Paleogeography Symposium 1, 

p. 455-466. 

Walker, N.W., and Mattinson, J.M., 1980, The Canyon Mountain Complex, Oregon: U-Pb ages of zircons and possible tectonic correlations [abs.]: Geological Society of America Abstracts with 

Programs,~ 12,no. 7, p.544. 

Wardlaw, B.R., and Jones, D.L., 1980, Triassic conodonts from 

eugeoclinal rocks of western North America and their tectonic 

significance: Revista Italiana de Paleontologia e Stratigrafia, v. 

85, p. 895-908, 1 pl. 

Wardlaw, B.R., Nestell, M.K., and Dutro, J.T., Jr., 1982, Biostratigraphy and structural setting of the Permian Coyote Butte Formation of central Oregon: Geology, v. 10, no.1, p. 13-16. 

Yao, Akira, Matsuda, Tetsuo, and Isozaki, Yukio, 1982, Triassic and 

Jurassic radiolarians from the Inuyama area, central Japan: 

Osaka City University, Journal of Geoscience, v. 23, p. 135-154. 

PLATES 8.1-8.3 

[Contact photographs of the plates in this chapter are available, at cost, from U.S. Geological 

Survey Library, Federal Center, Denver, Colorado 80225] 
PLATE 8.1 

Scanning electron photomicrographs of Permian radiolarians from cherts in the Grindstone terrane, 

east-central Oregon. 

FIGURE 1, 2 Pseudoalbaillella lanceola Ishiga, Kito, and Imoto. Loc. 82CB-105, x 420 and 

x 350, respectively. 

3-6. Pseudoalbaillella fusiformis (Holdsworth and Jones). Loc. 82CB-105, x 240, x 250, 

x 350, and x 360; respectively. 

7, 8. Pseudoalbaillella aff. P longicornis Ishiga, Kito, and Imoto. Loc. 82CB-105, x 420, 

and x 390, respectively. 

9, 10. Pseudoalbaillella longicornis Ishiga, Kito, and Imoto. Loc. 82CB-105, x 420, and 

x 420, respectively. 

11. Pseudoalbaillella fusiformis (Holdsworth and Jones). Loc. 82CB-105, x 350. 

12. Pseudoalbaillella aff. P fusiformis (Holdsworth and Jones). Loc. 82CB-105, x 360. 

13. Latentifistula(?) sp. Loc. 82CB-105, x 300. 

14-16. Pseudoalbaillella aff. P longicornis Ishiga, Kito, and Imoto. Loc. 82CB-105, x 275, 

x 400, and x 425, respectively. 

17. Latentibifistula(?) fragment. Loc. 82CB- 105, x 260. 

18. Quinqueremis(?) sp. Loc. 82CB....:.105, x 360. 

19. Latentifistula crux Nazarov and Ormiston. Loc. 82CB-105, X 225. 

20, 21. Undescribed mammelate spumellarians. Loc. 82CB-105, x 300 and x 325, 

respectively. 
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1435 PLATE 8.1 

PSEUDOALBAILLELLA, LATENTIFISTULA, LATENTIBIFISTULA, QUINQUEREMIS (?) 
PLATE 8.2 

Scanning electron photomicrographs of Carboniferous radiolarians from cherts in the Begg Member 

of the Vester Formation, Izee terrane, east-central Oregon. 

FIGURE 1-6. Undescribed Late Paleozoic forms of the family Entactiniidae. Loc. 82CB-101A, 

X 300, X 260 X 390, X 330, X 500, and 

x 330, respectively. 

7. Latentifistula fragment. Loc. 82CB-101A, x 360. 

8, 9. Undescribed Late Paleozoic forms of the family Entactiniidae. Loc. 82CB-101A, 

x 390 and x 450, respectively. 
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1435 PLATE 8.2 

LA TENT/FISTULA 
PLATE 8.3 

Scanning electron photomicrographs of Late Triassic radiolarians from the Izee and Baker terranes, 

east-central and eastern Oregon. 

FIGURE 1. Pseudostylosphaerajaponica (Nakaseko and Nishimura). Loc. FR18....:.292, x 225. 

2. Pseudostylosphaerajaponica (Nakaseko and Nishimura). Loc. FR18-290, x 240. 

3-5. Undescribed Pseudostylosphaera sp. Loc. FR81-290, x 165, x 170, and x 240, 

respectively. 

6. ?Trilonche annulata (Nakaseko and Nishimura). Loc. FR81-292, x 360. 

7. 1hassocampe(?) pulchra Kozur and Mostler. Loc. FR81-292, 170. 

8. Triassocampejaponica (Nakaseko and Nishimura). Loc. FR81-290, x 330. 

9. Triassocampejaponica (Nakaseko and Nishimura). Loc. FR81-292, x 360. 

10. Undescribed Triassocampe sp. Loc. FR81-290, x 400. 

11. Triassocampe annulata (Nakaseko and Nishimura). Loc. FR81-292, x 330. 

12. Eonapora sp. Loc. FR81-290, x 400. 

13, 18. ?Tripocycliajaponica Nakaseko and Nishimura. Loc. FR81-292, x 360 and 360, 

respectively. 

14. Triassocampe deweueri (Nakaseko and Nishimura). Loc. S-6, x 300. 

15. Proximal portion of?Yeharaia sp. Loc. FR81-290, x 360. 

16, 17. Triassocampe aff. T.japonica (Nakaseko and Nishimura). Loc. FR81-292, x 330 and 

x 360, respectively. 

19. Capnodoce cf C. angusta Blome. Loc. FR81-292, x 325. 

20. Capnodoce trauersi Pessagno. Loc. FR81-292, x 260. 

21. Capnodoce antiqua Blome. Holotype (USNM 205819),. Loc. OR-6 (in Blome, 1984, 

p. 60), Rail Cabin Mudstone Member of the Vester Formation, x 350. 

22. Quasipetasus disertus Blome. Loc. FR81-292, x 325. 

23. Quasipetasus insolitus Blome. Holotype (USNM 305963), Loc. OR-143 (in Blome, 

1984, p. 61), Rail Cabin Mudstone Member of the Vester Formation, x 350. 
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1435 PLATE 8.3 

PSEUDOSTYLOSPHAERA, ? TRILONCHE, TRIASSOCAMPE,_ EO NAPORA, 

? TRIPOCYCLIA, ?YEHARAIA, CAPNODOCE, QUASI PET ASUS 
GPO 786 .. 048/48010