Lithostratigraphy, Microlithofacies, and Conodont

Biostratigraphy and Biofacies of the Wahoo

Limestone (Carboniferous), Eastern Sadlerochit

Mountains, Northeast Brooks Range, Alaska

U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER

1568

j^^^fe^i^^t%t^^S%^A^tK-^^ ^.3lF
Cover: Angular unconformity separating steeply dipping pre-Mississippian 

rocks from gently dipping carbonate rocks of the Lisburne Group near Sunset 

Pass, eastern Sadlerochit Mountains, northeast Brooks Range, Alaska. The 

image is a digital enhancement of the photograph (fig. 5) on page 9.
Lithostratigraphy, Microlithofacies, and Conodont 

Biostratigraphy and Biofacies of the Wahoo 

Limestone (Carboniferous), Eastern Sadlerochit 

Mountains, Northeast Brooks Range, Alaska

By Andrea P. Krumhardt, Anita G. Harris, and Keith F. Watts

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568

Description of the lithostratigraphy, microlithofacies, and 

conodont bio stratigraphy and biofacies in a key section of 

a relatively widespread stratigraphic unit that straddles 

the Mississippian-Pennsylvanian boundary

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

GORDON P. EATON, Director

For sale by U.S. Geological Survey, Information Services 

Box 25286, Federal Center, Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government.

Published in the Eastern Region, Reston, Va. 

Manuscript approved for publication June 26, 1995.

Library of Congress Cataloging in Publication Data

Krumhardt, Andrea P.

Lithostratigraphy, microlithofacies, and conodont biostratigraphy and biofacies of the 

Wahoo Limestone (Carboniferous), eastern Sadlerochit Mountains, northeast Brooks 

Range, Alaska / by Andrea P. Krumhardt, Anita G. Harris, and Keith F. Watts.

p. cm. — (U.S. Geological Survey professional paper ; 1568)

Includes bibliographical references.

Supt, of Docs, no.: I 19.16:1568

1. Geology, Stratigraphic—Pennsylvania^ 2. Geology, Stratigraphic—Mississippian. 

3. Geology—Alaska—Sadlerochit Mountains Region. 4. Conodonts—Alaska— 

Sadlerochit Mountains Region. 5. Paleontology—Pennsylvanian. 6. Paleontology— 

Mississippian. 7. Wahoo Limestone (Alaska). I. Harris, Anita G. II. Watts, Keith F. 

III. Title. IV. Series.

QE673.K77 1996

551.7'5'097987—dc20 95-31281

CIP
CONTENTS

Abstract........................................................................................................................... 1

Introduction..................................................................................................................... 2

Acknowledgments................................................................................................... 2

Previous Studies.............................................................................................................. 4

Regional Geologic Setting.............................................................................................. 5

Lisburne Group, Northeast Brooks Range.............................................................. 5

Alapah Limestone........................................................................................... 7

Alapah Limestone-Wahoo Limestone Boundary, Northeast Brooks Range........... 7

Wahoo Limestone............................................................................................ 7

Lithostratigraphy of the Wahoo Limestone, Eastern Sadlerochit Mountains ................. 9

Lower Member of the Wahoo Limestone ............................................................... 10

Upper Member of the Wahoo Limestone................................................................ 10

Conodont Biostratigraphy of the Wahoo Limestone, Eastern Sadlerochit

Mountains ........................................................................................................... 12

muricatus Zone ....................................................................................................... 13

Lower muricatus Subzone .............................................................................. 13

Upper muricatus Subzone............................................................................... 13

noduliferus-primus Zone......................................................................................... 14

minutus Fauna......................................................................................................... 15

Lower minutus Fauna...................................................................................... 15

Idiognathodus Fauna............................................................................................... 16

The Mid-Carboniferous Boundary—An Approximation of the MississippianPennsylvanian Boundary .................................................................................... 17

Biostratigraphic Criteria.......................................................................................... 17

Conodont-Based Boundary in the Eastern Sadlerochit Mountains......................... 18

Foraminiferan-Based Boundary in the Eastern Sadlerochit Mountains ................. 18

Morrowan-Atokan Boundary.......................................................................................... 20

Conodont Biofacies......................................................................................................... 21

Conodont Biofacies and Associated Microlithofacies, Wahoo Limestone,

Eastern Sadlerochit Mountains ................................................................... 21

Mississippian Part of the Wahoo Limestone................................................... 22

Cavusgnathid Biofacies .......................................................................... 22

Near-Restricted to Open-Platform Environments........................... 22

Cavusgnathid-Kladognathid Biofacies ................................................... 25

Open-Platform to Open-Marine Environment................................ 25

Gnathodid-Hindeodid Biofacies ............................................................. 26

Low-Energy, Open-Marine Environment....................................... 26

Pennsylvanian Part of the Wahoo Limestone.................................................. 26

Lower Member of the Wahoo Limestone....................................................... 27

Adetognathid-Related Biofacies............................................................. 27

Near-Restricted to Open-Platform Environment............................ 27

Low-Energy, Open-Marine Environment....................................... 27

Upper Member of the Wahoo Limestone........................................................ 27

Adetognathid-Rhachistognathid Biofacies ............................................. 27

Restricted to Near Open-Platform Environment............................. 27

Open-Platform to Near-Shoal Open-Platform Environments......... 28

Tidal-Channel(?) Environment....................................................... 28

III
IV CONTENTS

Rhachistognathid Biofacies.................................................................... 28

Near-Shoal, Open-Platform Environment...................................... 28

Shoal or Tidal-Channel Environments............................................ 28

Near-Shoal, Open-Marine Environment......................................... 29

Declinognathodid-Related Biofacies...................................................... 30

Near-Shoal, Open-Marine Environment......................................... 30

Low-Energy, Open-Platform and (or) Open-Marine

Environment........................................................................ 30

Biofacies Summary................................................................................................. 30

Conodont Preservation and CAI Values ......................................................................... 31

Systematic Paleontology................................................................................................. 32

References Cited............................................................................................................. 50

Appendix 1. Conodont Faunas, Biofacies, and Age and Lithology of Collections

Mentioned in Text but not Described Elsewhere in this Report......................... 59

PLATES

[Plates 1-5 follow appendix 1; plate 6 in pocket]

1-3, 5. Conodonts from the Wahoo Limestone, eastern Sadlerochit Mountains, Alaska.

4. Conodonts from the Wahoo Limestone, eastern Sadlerochit Mountains, and Pogopuk Creek, Franklin

Mountains, Alaska. 

6. Conodont zones, faunal intervals, and species distribution and lithologies of the Wahoo

Limestone in the study section, eastern Sadlerochit Mountains, northeast Brooks Range, Alaska.

FIGURES

1. Map showing distribution and tectonic affinities of the Lisburne Group in the Brooks Range.................................... 3

2. Map showing distribution of the Lisburne Group, major structural features, and location of study section,

northeast Brooks Range ................................................................................................................................................ 4

3. Diagram showing generalized stratigraphic succession, northeast Brooks Range and northeast coastal plain............ 6

4. Schematic diagram showing stratigraphic relationships, lithologies, and inferred depositional environments

of the Lisburne Group, northeast Brooks Range........................................................................................................... 8

5. Photograph of study section, eastern Sadlerochit Mountains ....................................................................................... 9

6. Photograph of Mississippian-Pennsylvanian boundary beds in upper part of lower member of the Wahoo

Limestone at study section............................................................................................................................................ 11

7. Diagram showing conodont zonation/faunal succession recognized in the Wahoo Limestone at study section

compared to the North American middle Carboniferous conodont zonation of Baesemann and Lane........................ 12

8. Diagram comparing lithostratigraphic, biostratigraphic, and time-rock boundaries between study section and

nearby Sunset Pass section............................................................................................................................................ 19

9. Schematic diagram showing depositional model for and sediment characteristics of the Wahoo Limestone.............. 23

10. Schematic diagram showing generalized paleogeography, biofacies, and distribution of conodont genera,

Wahoo Limestone, eastern Sadlerochit Mountains ....................................................................................................... 24

TABLES

[Tables 1 and 2 are in pocket]

1. Conodont species distribution in the Wahoo Limestone in the study section, eastern Sadlerochit Mountains, northeast 

Brooks Range, Alaska.

2. Depositional environments interpreted from carbonate-microlithofacies and conodont-biofacies data, Wahoo Limestone, 

eastern Sadlerochit Mountains, northeast Brooks Range, Alaska.
Lithostratigraphy, Microlithofacies, and Conodont Biostratigraphy

and Biofacies of the Wahoo Limestone (Carboniferous), 

Eastern Sadlerochit Mountains, Northeast Brooks Range, Alaska

By Andrea P. Krumhardt, 1 Anita G. Harris,2 and Keith F. Watts3

ABSTRACT

The Lisburne Group (chiefly Carboniferous) is a widespread succession of platform carbonate rocks that apparently developed along a south-facing passive continental 

margin in northern Alaska. Marine transgressions onlapped 

northward across northeast Alaska allowing the Lisburne 

platform to extend over terrigenous deposits of the Endicott 

Group and local pre-Mississippian paleotopographic highs. 

The Wahoo Limestone is the youngest formation of the 

Lisburne Group in northeasternmost Alaska, ranging from 

latest Mississippian (latest Chesterian) to Middle Pennsylvanian (at least early Atokan) in age. The Wahoo Limestone 

was systematically sampled for lithostratigraphy and conodont biostratigraphy and biofacies at a relatively continuous section (about 262 m in thickness) in the eastern 

Sadlerochit Mountains.

Existing Carboniferous conodont zonations could not 

be readily applied to the study section because most zonal 

indicators are absent. Species diversity is low for a section 

that spans at least 10 million years. Twenty-four species, 

distributed among 14 genera, were identified in 72 productive samples; no new species were distinguished. The following biostratigraphic zones and faunal intervals were 

recognized: Upper muricatus Subzone (latest Chesterian); 

noduliferus-primus Zone (earliest Morrowan); minutus 

Fauna (Morrowan) containing a lower subdivision (lower 

minutus Fauna of early to middle? Morrowan age); and an 

Idiognathodus Fauna (Morrowan? to early Atokan). The 

presence of Idiognathodus incurvusl and Rhachistognathus 

minutus subspp. above the first occurrence of the foraminifer Pseudostaffella sp. in the uppermost part of the Wahoo 

Limestone indicates that the youngest beds are early Atokan 

in age. The Mississippian-Pennsylvanian boundary is

Department of Geology and Geophysics and Geophysical Institute, 

University of Alaska Fairbanks, Fairbanks, AK 99775.

2U.S. Geological Survey.

3 Geophysical Institute, University of Alaska Fairbanks, Fairbanks, 

AK 99775.

placed at 56 m above the base of the lower member of the 

Wahoo Limestone on the basis of the lowest occurrence of 

Declinognathodus noduliferus japonicus above forms transitional from Gnathodus girtyi simplex.

Established foraminiferan biostratigraphy is somewhat 

inconsistent with respect to conodont-based time-rock 

boundaries and conodont zones in the study section and in 

northern Alaska in general. This indicates that the standard 

foraminiferan and (or) conodont zonations are not locally 

applicable without modification.

Conodont collections from the Wahoo Limestone 

across the northeast Brooks Range (from Wahoo Lake to the 

Clarence River) show remarkably similar faunal successions but even less species diversity than that found in the 

study section. Fifty-six biostratigraphically significant collections documenting the distribution of faunal units recognized in the study section are described in appendix 1.

The Wahoo Limestone formed in a range of chiefly 

open-platform, near-shoal, and open-marine environments 

on the shallow, inner part of a high-energy carbonate ramp. 

In the uppermost Mississippian and lowermost Pennsylvanian part of the formation, shoal facies were uncommon so 

that open-platform and open-marine microlithofacies and 

conodont biofacies were not clearly separated. Grain types 

and, to a lesser extent, conodonts were hydraulically spread 

beyond their original settings making some paleoenvironmental interpretations equivocal. The use of conodont biofacies and microlithofacies in concert clarifies some of the 

environmental ambiguities. In the Pennsylvanian part of the 

Wahoo Limestone, extensive ooid and skeletal shoal tracts 

separated open-marine and open-platform environments 

producing more distinct biofacies and diagnostic microlithofacies. Rhachistognathids thrived in and adjacent to the 

shoal facies. After death, many of their skeletal elements 

remained in place; however, a substantial number were 

washed into surrounding environments, masking natural 

species associations. Similarly, mixing of carbonate grains 

obscures microlithofacies interpretations. The vertical succession of conodont biofacies substantiates microlithofacies 

interpretations that indicate that the upper part of the Wahoo
CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

Limestone represents a transgressive-regressive sequence 

passing from restricted platform to shoals and, finally, back 

to restricted platform. Conodont species associations, 

abraded conodonts and bioclasts, and grain-type associations indicate a high degree of postmortem hydraulic 

mixing across the carbonate platform supporting the interpretation that it represents a high-energy carbonate ramp.

Conodont color alteration indices (CAI) in the study 

section are chiefly 4 and 6, rarely 3, and very rarely 3.5 and 

4.5. Most conodont elements have a sugary and (or) corroded texture. The anomalously high CAI values of 6 have 

positive correlation with grainstones and dolomitized intervals and negative correlation with quartz-rich and poorly 

washed carbonate rocks. The range of CAI values and textures and the distribution of high CAI values suggest local, 

probably low-temperature hydrothermal alteration of the 

Wahoo Limestone.

INTRODUCTION

The Lisburne Group (chiefly Carboniferous) is a thick 

sequence of predominantly carbonate rocks that extends 

across the Brooks Range and into the subsurface of the 

North Slope (fig. 1). In the northeast Brooks Range, the Lisburne Group is at least 500 m thick and is subdivided into 

the Alapah Limestone and overlying Wahoo Limestone. 

The northeast Brooks Range is the area east of the 

Trans-Alaska Pipeline and north of the Continental Divide, 

which trends east-northeast between lat 68° and 69° N. and 

long 139° to 147° W.

The Wahoo Limestone in the eastern Sadlerochit 

Mountains, Arctic National Wildlife Refuge (ANWR), was 

measured and systematically sampled for conodonts, foraminifers, and microlithofacies (figs. 1, 2). The study section 

is well exposed, contains some of the youngest beds of the 

Wahoo Limestone in the area, and is similar to the Wahoo 

Limestone in the subsurface at Prudhoe Bay (Reiser, 1970; 

Armstrong and Mamet, 1974). It is accessible from Kaktovik, a major embarkation point for ANWR (fig. 1).

This study was undertaken to (1) establish a conodont 

biostratigraphic framework for the Wahoo Limestone in 

ANWR, (2) determine the position of the MississippianPennsylvanian boundary in the formation, (3) integrate conodont biofacies with microlithofacies studies (for example, 

Armstrong, 1972; Armstrong and Mamet, 1977; Watts, 

1990; Gruzlovic, 1991; Krumhardt, 1992), and (4) compare 

conodont and foraminiferan biostratigraphic data. Previously, foraminifers provided the primary biostratigraphic 

control for the Lisburne Group in ANWR. Inconsistent 

assignment of foraminiferan zones and lithologic boundaries by previous researchers in our study area, however, 

indicates unresolved stratigraphic problems (see fig. 8). 

More recently, conodonts have been used to refine, confirm, 

or as an alternative to foraminiferan age determinations 

(>500 conodont collections from the Lisburne Group were

analyzed by A.G. Harris from 1979 to 1994 and by Harris 

and A.P Krumhardt from 1989 to 1994; published and 

unpublished written communs.). Many of these samples 

indicate that conodonts have greater biostratigraphic resolution than foraminifers in the uppermost Mississippian and 

Lower Pennsylvanian part of the Lisburne Group. In addition, the conodont Declinognathodus noduliferus is the primary micropaleontologic indicator for the base of the 

Pennsylvanian (Lane and Manger, 1985). Thus, conodonts 

are the preferred microfossils for locating the midCarboniferous (Mississippian-Pennsylvanian) boundary.

ACKNOWLEDGMENTS

We are grateful to many people and organizations for 

their time, help, knowledge, and support during this study. 

Much of this investigation was part of a Master's thesis by 

A.P. Krumhardt at the University of Alaska Fairbanks 

(Krumhardt, 1992). Krumhardt is indebted to the U.S. Fish 

and Wildlife Service and the helicopter pilots who provided 

safe and timely transport throughout ANWR. Special 

thanks are due Kurt ("Stretch") Johnson, who wounded his 

knees and destroyed several pairs of boots collecting and 

hauling conodont samples. Her colleague, P.D. Gruzlovic, 

provided invaluable advice on thin section interpretations. 

Krumhardt acknowledges the aid of her advisors (exclusive 

of co-authors), R.K. Crowder and R.A. Gangloff. Funding 

for Krumhardt and Watts was provided by (1) the Tectonics 

and Sedimentation Research Group, University of Alaska 

Fairbanks, from contributions by Amoco, ARCO Alaska, 

ARCO Research, BP Alaska, Chevron, Conoco, Elf Aquitaine, Exxon, Japan National Oil Corporation, Marathon, 

Mobil, Murphy, Phillips, Shell, Texaco, and UNOCAL, 

(2) the U.S. Department of Energy (contract no. DE-AC22- 

89BC14471), and (3) the University of Alaska Museum 

Geist Fund to partly cover field and thin section expenses. 

Watts also acknowledges partial support from the Petroleum 

Research Fund, administered by the American Chemical 

Society, and the Geophysical Institute and College of Natural Sciences of the University of Alaska Fairbanks.

Special thanks are extended to J.F. Baesemann, H.R. 

Lane, and PL. Brenckle, Amoco Production Company, 

Houston, Tex.; Sylvie Pinard, Geological Survey of Canada; and R.C. Grayson, Jr., Baylor University, Waco, Tex., 

for their expert consultation on conodont and Foraminifera 

specimens. Many collections listed in the appendix were 

submitted to us for conodont analysis by other investigators 

identified in the appendix. We are indebted to them for 

providing stratigraphically well-positioned samples that 

yielded important data for our understanding of the biostratigraphic and paleoenvironmental distribution of conodonts in the Lisburne Group. Particular thanks are 

extended to S.K. Morgan and M.K. Eckstein, University of 

Alaska Fairbanks, for collecting many samples from their
INTRODUCTION

if |0

3 5- H-- 

>

- 0 O -" ;!i r-a: 0 

•

^ —

5 £ S>^ £• x 

^ c Er°, ^E 3 ii ^9 8*

!l|Il 1

< co ^ 12 t rt 3- co => 00 &

u.

Q.

CO0

§ Q 0 w *- .2-0

5i| 11 8

*o ^ E .<S c

3 -C T3 •>< < "° -2

2 E ® o o 2 E 

^00 §.£0 g

3 co cr <^^

:<.E o0o

\Lf 

>, 0

^:

0 

.aE^z

^

"coE

-c^

O CO

CO CD

05 0

~ O

CO -C

i: T3 

CVD E

ii

0 « 

O C/5 >- ^:

CO 0

^ P OC= CO

o 5

£°

8l

l!" CO o

CO "3

D_ co

CO ,_

13 .E

0£

O 0 

^1 0

£ c

0 =>

-2 ^ "co "c

•D 3= 

C CO 

CO o

CO ^

S a- 0 co

O 05

-C '^ £ 2

89

1^

CO "

D2

0 

•^•c*

CO CO

00C

£= co 0 ^.

05 O

>.e f~2 co -g'g

2i

CO g

^: CO ~C

O CO

23

CO 0

oo

l«

§1O w

= CO < :6

u

fT

oo ON

fc 

o 2X8Oeo

c ^

E ON

O ON

^ e

en O

•S^

o a t-H UCQ o

O [L, i-i _ O

c3 X

<u S3 P £

3 <

-O <+_ "5 O

J >. m -^

oo {«

Q | o

!-H T3 ^
CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

145°30'W.

-t*

EXPLANATION

| | Coastal-plain deposits (Quaternary to 

Cretaceous)

Sedimentary rocks (Cretaceous to 

Precambrian)-Mainly Permian to 

Cretaceous sedimentary rocks and 

subordinate pre-mid-Caboniferous 

sedimentary, metamorphic, and 

igneous rocks

Lisburne Group (Carboniferous)- 

Carbonate rocks 

—— Contact

A_*. Thrust fault-Sawteeth on 

upper plate

Anticline-Showing plunge

Measured section or 

sample locality

o 10 MILES

I l l

69° 30' N.

Figure 2. Distribution of the Lisburne Group, major structural 

features, and locations of study section (1A) and selected measured sections discussed in this report, northeast Brooks Range 

(geology modified from Bader and Bird, 1986; see fig. 1 for 

regional setting). Numbered localities refer to measured sections 

and (or) conodont collection sites described in appendix 1. Lettered and some numbered localities are sections described by other

workers referred to in text: IB, Armstrong and co-workers (Armstrong and others, 1970; Armstrong, 1972; Armstrong and Mamet, 

1975, 1977; Mamet and Armstrong, 1984; Wood and Armstrong, 

1975); C, IB, and 1C, Carlson (1987); 2, Clough and Bakke (1986) 

and Imm (1986); G, 6, and 7, Gruzlovic (1991); and 5, Morgan 

(1992).

measured sections and providing us with microlithofacies 

analyses of their samples. We are most grateful to J.A. 

Dumoulin, U.S. Geological Survey; P.H. von Bitter, Royal 

Ontario Museum and University of Toronto; L.M. Brown, 

Lake Superior State University; and G.D. Webster, 

Washington State University for their heroic, timely, and 

thorough reviews of the manuscript. This paper was considerably improved by their technical reviews.

PREVIOUS STUDIES

Schrader (1902, p. 241) first used the name "Lisburne 

formation" for limestone and shale exposed in the vicinity 

of Anaktuvuk Pass in the central Brooks Range (fig. 1). The 

regional extent and character of the formation were more 

fully described by him in a later paper in which he states 

that the Lisburne extends from Cape Lisburne to Anaktuvuk 

Pass and eastward "nearly to the international boundary and

probably beyond it" (Schrader, 1904, p. 67). Subsequently, 

in the central Brooks Range, Bowsher and Dutro (1957) 

raised the Lisburne to group rank and subdivided it into two 

new formations, the Wachsmuth Limestone and overlying 

Alapah Limestone. Brosge and others (1962) distinguished 

a third and the youngest formation of the group, the Wahoo 

Limestone, in the eastern Brooks Range.

Detailed regional biostratigraphic and microlithofacies 

analyses of the Lisburne Group accompanied the expansion 

of hydrocarbon exploration of the North Slope during the 

1970's. Armstrong and others (1970) first applied Mamet's 

Carboniferous foraminiferan zonation to the Lisburne 

Group in the northeast Brooks Range, and, later, Armstrong 

(1972) described the carbonate lithology, coral biostratigraphy, and paleoecology. Mamet and Armstrong (1972) 

examined sections in the Franklin and Romanzof Mountains (fig. 1) and later Armstrong and Mamet (1974) tied the 

Lisburne Group in the subsurface at Prudhoe Bay to exposures in ANWR. Wood and Armstrong (1975) described the
REGIONAL GEOLOGIC SETTING

diagenesis and stratigraphy of the Lisburne Group in the 

Sadlerochit Mountains and adjacent areas while Armstrong 

and Mamet (1975) extended their biostratigraphic studies to 

other sections in the northeast Brooks Range. Ultimately, 

Armstrong and Mamet (1977) produced a regional synthesis of their investigations for the entire northern Brooks 

Range. Armstrong and Mamet (1978) extended their work 

to the Lisburne Group in the allochthonous thrust sheets in 

the central and western Brooks Range. Mamet and Armstrong (1984) discussed the Mississippian-Pennsylvanian 

boundary in the Sadlerochit, Franklin, and Romanzof 

Mountains and placed the boundary at the contact between 

the Alapah and Wahoo Limestones. A revised megafossil 

zonation for the Carboniferous of the northern Brooks 

Range and its relation to Mamet's foraminiferan zonation is 

given in Dutro (1987). As in Mamet and Armstrong (1984), 

Dutro (1987) placed the Mississippian-Pennsylvanian 

boundary at the contact between the Alapah and Wahoo 

Limestones.

Since 1985, many reports have been produced on the 

geology of ANWR by investigators at the University of 

Alaska Fairbanks (for example, Crowder, 1990; Wallace 

and Hanks, 1990; Watts, 1990). Of particular importance to 

our study are reports on the depositional environments, 

cyclicity, and diagenetic history of the Wahoo Limestone in 

the eastern Sadlerochit Mountains and the stratigraphic evolution and lateral facies changes of carbonate cycles 

(parasequences) across the Lisburne Group carbonate platform (fig. 2; Carlson, 1987; Gruzlovic, 1991). Additional 

studies describing the geology of ANWR are included in 

Bird and Magoon (1987), Tailleur and Weimer (1987), and 

Grantz and others (1990).

REGIONAL GEOLOGIC SETTING

The parautochthonous rocks of northeastern Alaska 

are part of the tectonically complex Arctic Alaska terrane 

that also includes allochthonous thrust sheets of the southern Brooks Range and the relatively little deformed autochthonous rocks beneath the North Slope (fig. 1; Reiser, 1970; 

Mull, 1982; Crowder, 1990). The rocks in the Arctic Alaska 

terrane have been subdivided into the Franklinian, Ellesmerian, and Brookian tectono-depositional sequences (fig. 3; 

Grantz and May, 1983; Bird and Molenaar, 1987; Hubbard 

and others, 1987) using terminology established by Lerand 

(1973) in the Canadian Arctic.

The Franklinian sequence in the northeast Brooks 

Range includes Precambrian to Devonian sedimentary, 

metamorphic, and igneous rocks. Erosion of these rocks following orogenic uplift during the middle Paleozoic produced a paleotopography that considerably influenced 

subsequent depositional patterns and structural deformation 

(Watts and others, 1988; Wallace and Hanks, 1990).

Mississippian to Lower Cretaceous sedimentary rocks 

of the Ellesmerian sequence unconformably overlie the 

Franklinian sequence (fig. 3). The Ellesmerian sequence 

documents a long interval of sedimentation from a northerly 

source onto a broadly subsiding, passive continental margin. In the Carboniferous part of the sequence, terrigenous 

clastic sedimentary deposits of the Endicott Group (Mississippian in age in the Sadlerochit Mountains) are succeeded 

by carbonate-platform deposits of the Lisburne Group. A 

major unconformity with a hiatus of about 40 m.y. separates 

the Lisburne Group from the overlying terrigenous clastic 

deposits of the Sadlerochit Group (Permian and Triassic) 

(Crowder, 1990). The upper part of the Ellesmerian 

sequence (Triassic to Lower Cretaceous) is dominated by 

terrigenous shale of the Kingak Shale (primarily Jurassic) 

with lesser amounts of sandstone and rare phosphatic limestone and calcareous sandstone to siltstone of the Shublik 

Formation (Triassic). This report concerns the Carboniferous part of the Ellesmerian sequence.

LISBURNE GROUP, NORTHEAST 

BROOKS RANGE

The Lisburne Group (chiefly Carboniferous) is a thick 

succession (>500 m) of platform-carbonate rocks that 

apparently developed along a south-facing passive continental margin in northern Alaska (relative to present coordinates). Marine transgressions onlapped northward across 

northeast Alaska so that eventually the Lisburne platform 

extended over much of Arctic Alaska. In most of the northeast Brooks Range, the Lisburne Group gradationally overlies the fluvial to marginal-marine deposits of the Endicott 

Group (fig. 4). In the Sadlerochit Mountains, however, the 

pre-Mississippian rocks formed a paleotopographic high so 

that the Endicott Group is thin or absent (Armstrong and 

Mamet, 1975; Watts and others, 1988). Where the Endicott 

Group is absent, the Lisburne Group rests with angular discordance on southward-dipping, pre-Mississippian rocks 

(fig. 5); this relationship influenced the structural development of northeastern Alaska (Wallace and Hanks, 1990). 

South of the Sadlerochit Mountains, the Kayak Shale of the 

Endicott Group provides a major detachment surface. 

Because the Kayak Shale is absent or thin in the Sadlerochit 

Mountains, Ellesmerian rocks (fig. 3) remained attached to 

the underlying Franklinian rocks, and both deformed as a 

unit (Wallace and Hanks, 1990). Thus, the Lisburne Group 

here is parautochthonous and has undergone little northward tectonic transport.

In the northeast Brooks Range, the Lisburne Group 

consists of the Alapah Limestone and Wahoo Limestone. 

Three large-scale transgressive-regressive (TR) sequences 

are recognized in these strata (fig. 4; Gruzlovic, 1991). 

Superimposed on these large-scale sequences are many 

parasequences of variable thickness that record the response
CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

SEQUENCE

BROOKIAN

ELLESMERIAN

FRANKLINIAN

STRATIGRAPHIC UNIT

SURFICIAL DEPOSITS

GUBIK FORMATION

SAGAVANIRKTOK 

FORMATION

CANNING FORMATION

HUE SHALE

PEBBLE SHALE UNIT 

KEMIK SANDSTONE

KINGAK SHALE

KAREN CREEK SANDSTONE

SHUBLIK FORMATION

hI 

00. 

g g IVISHAK FORMATION

LU CC

r^O

g ECHOOKA FORMATION

z CL WAHOO LIMESTONE 

cc =) =>O ———

CD CC

WO AL/

_i

ENDICOTT 

GROUP

^PAH LIMESTONE

ITKILYARIAK FORMATION

KEKIKTUK CONGLOMERATE

MOUNT COPLESTON LIMESTONE

NANOOK LIMESTONE

KATAKTURUK DOLOMITE

SEDIMENTARY, METAMORPHIC, AND 

IGNEOUS ROCKS, UNDIVIDED

LITHOLOGY

|^p^£i2Sp^pw

^mmm'-^:^mm^m

^:^:^:^'~:-^-^^fJ:~:^:^:':'^

.'•."-•.V 1 '-.''-• .•'••'-.'••"•.''•vV-;1.' •'.•-: .-"•.•".- '•:.'•;' •'.• '•;. -:'.• "•:'••. ';'-.'•'•:'-• '-.•'.• V-v.'O-' ','•.'"•• "•.'"-• '•:' '•.''-• '• •"-•'-•'.• '-.'-';'.• "•.''.•". i'.' '-.-'.• '..'.- ';".••.•',•• '.•'.,•'.• -;'-V- V'.1 '-.' •'•;'- '•:'.• '•."--'•:".• ";.•'•:"

mmmmmm

MM^M^MM^M^M

ii iiii i i i

/ / / / / / X

———————————————————— L

/ / / X / X

• 1 • 1 • ] • • 1 • 1 • 

. ]. . 1 . . I- . 1 . .1 . 1-

.f.^y.f^r^y.y.y.y.f.y.y.y.y.y.y.^r^r^r.r^.f

AGE

HOLOCENE

PLEISTOCENE

PLIOCENE 

MIOCENE

OLIGOCENE

EOCENE

PALEOCENE 

LATE CRETACEOUS

EARLY CRETACEOUS

EARLY CRETACEOUS(?) 

AND

JURASSIC 

TRIASSIC

PERMIAN 

PENNSYLVANIAN

MISSISSIPPI

PRE-MISSISSIPPIAN

EXPLANATION

Metamorphic rocks, 

undivided

Contact or boundary-- 

Dashed where approximately located

Figure 3. Generalized stratigraphic succession, northeast Brooks Range and northeast coastal plain, Alaska (not to scale; 

modified from Bird and Molenaar, 1987).
REGIONAL GEOLOGIC SETTING 7

of the platform to eustacy and (or) changes in carbonate 

production and platform subsidence (fig. 4: Watts, 1990; 

Gruzlovic, 1991). The Endicott Group (where present) and 

the Alapah Limestone represent the first large-scale TR 

sequence. The remaining TR sequences generally correspond to the lower and upper members of the Wahoo 

Limestone.

ALAPAH LIMESTONE

The age of the Alapah Limestone (-200 to >500 m in 

thickness) is Meramecian and (or) Chesterian on the basis 

of foraminiferan (Armstrong and others, 1970; Armstrong 

and Mamet, 1977) and conodont biostratigraphy (this 

report). In the Sadlerochit Mountains, Alapah deposition 

began in the Chesterian (Mamet and Armstrong, 1984). The 

age of the base of the Lisburne Group is progressively older 

southward and westward. In the northern part of the northeast Brooks Range, continued transgression during much of 

the deposition of the Alapah Limestone is indicated by a 

transition from algal limestone into cross-stratified skeletal 

grainstone culminating in bryozoan-pelmatozoan limestone. 

The upper member of the Alapah Limestone is dominantly 

spiculitic dolostone and dolomitic lime mudstonewackestone containing lesser amounts of cryptalgal 

laminite (fig. 4: Watts, 1990; Gruzlovic, 1991) indicating 

restricted and (or) peritidal conditions associated with a 

major regression. The uppermost part of the Alapah Limestone is late Chesterian in age (Armstrong and Mamet, 

1977; this report). The contact with the overlying Wahoo 

Limestone is relatively sharp in the study area but is more 

gradational and difficult to define farther to the south.

ALAPAH LIMESTONE-WAHOO LIMESTONE 

BOUNDARY, NORTHEAST BROOKS RANGE

The base of the Wahoo Limestone is placed at the first 

light-weathering, cliff-forming, fossiliferous limestone 

above the slope-forming, darker limestone and dolostone 

characteristic of the underlying Alapah Limestone (fig. 5). 

A similar contact was chosen by Brosge and others (1962), 

Armstrong (1972, 1974), Wood and Armstrong (1975), and 

Carlson (1987). Other authors were inconsistent in their 

placement of the contact (see fig. 8) and used biostratigraphic rather than lithostratigraphic criteria so that their 

contact approximated the Mississippian-Pennsylvanian 

boundary (Armstrong and others, 1970; Armstrong and 

Mamet, 1974, 1975, and 1977; and Mamet and Armstrong, 

1984).

WAHOO LIMESTONE

The age of the Wahoo Limestone (0 to >350 m in 

thickness) is late Chesterian to Atokan on the basis of foraminifers (Armstrong, 1972, 1974; Wood and Armstrong, 

1975; Carlson, 1987) and conodont biostratigraphy (this 

report). Brosge and others (1962) named the Wahoo Limestone and subdivided it into lower and upper members at its 

type section near Wahoo Lake (fig. 1). They assigned the 

formation a Pennsylvanian(?) and Permian age on the basis 

of brachiopod-bryozoan assemblages in the basal part of the 

lower member and brachiopods in the uppermost part of the 

upper member. Our conodont collections from the formation, 1.5 km west of the type section, show that the lower 

member is within the late Chesterian muricatus Zone at its 

base, and the appearance of Adetognathus lautus 15 m 

higher indicates the Upper muricatus Subzone (app. 1, Iocs. 

4Ala, b). The first definitive Pennsylvanian strata are 

marked by the appearance of Declinognathodus noduliferus, the guide to the Pennsylvanian, at 155 m above the 

base of the lower member (app. 1, loc. 4Ald). The youngest 

bona fide Wahoo Limestone at the type locality is Morrowan to early Atokan in age (Watts and others, 1992; app. 

1, loc. 4E). At its type locality, Watts and others (1989) 

referred the calcareous beds of Permian age to the Echooka 

Formation in their examination of the upper member of the 

Wahoo Limestone. A collection from 4.5 m below the top of 

the formation, about 5 km west of the type section, helps 

constrain the age of the uppermost beds to the late Morrowan or early Atokan (app. 1, loc. 4D).

Grainstone makes up two-thirds of the Wahoo Limestone at the study section indicating deposition under dominantly high-energy conditions. We recognize two mappable 

members of the Wahoo Limestone: light-gray, massive, 

cliff-forming grainstone and packstone of the lower member overlain by the heterolithic upper member that forms 

ledge-and-slope topography. The lower member represents 

a large-scale TR sequence (fig. 4) consisting primarily of 

bryozoan-pelmatozoan grainstone and packstone that probably formed in an open-marine environment. Four to five 

parasequences (each 10-20 m in thickness) are recognized 

within the lower member (fig. 4; Carlson, 1987; Watts, 

1990; Gruzlovic, 1991); these probably formed in slightly 

deeper water than those of the upper member. Parasequences in the lower member are more difficult to distinguish in the field because they lack the marked lithologic 

contrasts characteristic of the upper member; parasequences 

of the lower member are best recognized by microlithofacies analysis.

In the eastern Sadlerochit Mountains, the contact 

between the lower and upper members of the Wahoo Limestone appears to be planar but locally has erosional relief 

(Carlson, 1987; Krumhardt and Harris, 1990). Farther to the 

southwest, in the Fourth Range and at Plunge Creek (fig. 2), 

this contact is gradational (Gruzlovic, 1991).

Most of the upper member of the Wahoo Limestone 

represents a TR sequence containing many parasequences 

(each 3-9 m thick) related to relative sea-level changes and 

the migration of ooid shoals. The ooid shoals formed a
CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

SYSTEM

NOlSSVIdl 

PERMIA PENNSYLVANIAN 

MISSISSIPPIAN

GROUP

hi

OQ_ 

O=) 

cro

SAD LURNE GROUPGF

ENDICOTT GROUP LISB

PRE- MISSISSIPPIAN

STRATIGRAPHIC 

UNIT

Ivishak Formation 

(part)

Echoo 

Format

— x_^ — \__s~-

Wahoo 

Limestone

Alapah 

Limestone

Itkilyari 

Formati

Kayak St

ka 

ion

p^_^ — x

upper 

member

lower 

member

upper 

member

middle 

member

lower 

member

ak 

on

nale

Kekiktuk 

Conglomerate

- ——— -^ /~ —— v, f ——— "N. /" ——— ~V

Mount Copleston Limestone

Nanook Limestone

Katakturuk Dolomite

Sedimentary, metamorphic, Land igneous rocks, undivided

LITHOLOGY

^'-^^'-••^^'-^-.^•'''••-y'^-^^'^-^-'^-'-'v^'-^ •.••.::--;•..•-'.-;•.-'-::-.••.-.•.•."-'.-•'.••-.•.'.-•.•.••-'.-••.-'--.•-'.••.'.•-'.- 

V;V. ^V.-VVV>Y: .;V:>:;V;V;'.''V''v'^''V>V-V'';-'>: 

^ --^: -V^->V '^:^.:/. V:' ;:>^\->: '-'.\ ':': -;:!-;::-:

1 .* .( > > > > .'• .' .' .' .'• .' > .* > > .'• > .^!

• t ??*"!?.'.' y .'??.' * ? ,( ?•*• ^t ; ; ;. , 4: * t uttt^ttttt 

^: -*->- -t- . x * t * * * * > ' >. t '. t

^- -v»- ^.txttt»t\xt>tt

; ; ! ; ! ; ; ! ! i':'! 1 ! ;;;;!;!: H»- -t-t- .nmttxt>tmt 

•. x;. (> ;\y ;. 1 1 •' ;->ji> > t ?»f

.fit '. ! H I 1. \ X t t .. > t t t 

i X i. t t X t ; 1 X X t X X X X X X X »^- 

. i. < 1. X .XtiHiXXtXHXt> 

X X X X . X X -i. '. X X X X X X t X X ( X

HH ^-V -^ ( '. X '. < ( X X t X ( ^ X

-^- . ' . t t '• ^ ' ——— !<•'.'.'.<'.(< '.

r-e X ( X t ( i i>XtXXXXXXX

•SE j$ Jot ? .' ? ? .'• j j j?j}j=t

i ' ' ' i ' •- •- 1 ' •- 1 ' i ' •! • ' i ' i ' i ' ' ' i ' i ' ' ' i ' i ' ' '

•w^^wwywww^wW' 

W^^:;^:!^^^:^ 

SSv&ffiSiKvKSSK&SKv-VAS 

&S&&&SSKSSSSSSSS 

SiSSS;iji;SSi;vSSijj>ijijiji;SvSi£

Wj^^^^^^^^ 'x*^AiS^f3?Wvw7S?KS^C ; <N>tV^ ^-^ y}-^wf.K:^\

*J?^ ^ V \'^v' ^V^^ iS^' v 'v

lll|B|i!;i;;

||ppi3^:;|li?

:.:M-;v;<-;'\-;^:-:v:v:::>:': rt^y/:.'->:,'/<<<<\<\*:>:<-

DESCRIPTION

Quartzose sandstone and shale \

\ Siltstone and glauconitic sandstone >

Oncolitic and peloid 

packstone and grainstone ^ ci- cai

Ooid and (or) Donezella alternating 

packstone and grainstone wj^n

Ooid grainstone bryozoanpelmatozoan 

Cryptalgal and (or) limestone 

dolomitized mudstone

Bryozoan-pelmatozoan grainstone and 

packstone

Spiculitic dolostone and dolomitic 

lime mudstone-wackestone,

cryptalgal laminite

Bryozoan-pelmatozoan limestone

Cyclical, crossbedded, skeletal grainstone 

alternating with peloidal skeletal packstone. 

Algal limestone and spiculitic dolostone and 

limestone in lower part

Sandy limestone

Black shale, containing some sandstone 

and limestone

Quartzose sandstone and conglomerate

Sedimentary, metamorphic, and igneous 

rocks

DEPOSITIONAL 

ENVIRONMENT

INTERTIDAL

^^M 

^=

^^

•••

—— N 

\

re

PLATFORM

RESTRICTED

-=— —

J

•— • — . 

- -

. _ /

/ari 

ati\

-z.

LU 

Q_ 

O

Clc

- — 

— • — 

= 

^•^

^ 

=^

- •

^^

—— .

s»-

F

me 

m

• — \

ous 

rely

DPEN PLATFORM TO

OPEN MARINE

istic

^/

r^ 

- _

-^« 

-= 

"= ^^

=K

^* •* 

•~— -.

uvi 

to 

irgir 

arir

_ /- 

lyd

SOI

rod

SHOAL

; she

^^

=^^^ -

-^=: 

— = 

— =:

— — _

— — —

=»_ 

=«.

-=: 

•— — > 

—• =.

al

lal 

e

~v_

efor 

jth-c 

<s

OPEN 

MARINE

W/i 

BA

LLJ

O

CD 

<

3lf

^^

=a 

~ •• 

~ •- 

~ -.

— 

•=»

^M

^

— — —

~ ». 

•-. —

-S~

med 

Jippi

VE 

SE

g

LU

m

^f 

^-~-

>

^ 

^

)

X __ ^

, ng

Figure 4. Stratigraphic relationships, lithologies, and inferred 

depositional environments of the Lisburne Group, northeast 

Brooks Range. At the study section, the Endicott Group is absent, 

and the Alapah Limestone rests with angular discordance on

pre-Mississippian rocks (fig. 5). Only the Wahoo Limestone was 

systematically analyzed for this study. See fig. 3 for explanation. 

(Modified from Carlson, 1987; Watts, 1990; and Gruzlovie, 1991.)
LITHOSTRATIGRAPHY OF THE WAHOO LIMESTONE, EASTERN SADLEROCHIT MOUNTAINS

L0wli MEMBER OF THE 3*-;

Figure 5. View of study section looking northeast, eastern Sadlerochit Mountains (see fig. 2 for location). Measured section follows 

ridgeline and includes upper 3 m of the Alapah Limestone, the entire Wahoo Limestone, and lower 1 m of the Echooka Formation. Note 

that the Endicott Group is absent and a marked angular unconformity separates the Alapah from underlying pre-Mississippian rocks.

broad, discontinuous belt trending westward from the northern British Mountains, near the Canadian border, to the 

Canning River and then possibly northwestward toward 

Prudhoe Bay (fig. 1). The shoals pinch out southwestward, 

down the depositional dip of the carbonate ramp 

(Gruzlovic, 1991). The lithology of the upper member varies vertically and laterally as a consequence of ooid shoal 

migration through time (Carlson, 1987; Watts, 1990; 

Gruzlovic, 1991).

A disconformity of considerable magnitude (-40 m.y.) 

separates the Lisburne Group from the overlying Echooka 

Formation of Permian age (fig. 4). Regionally, this disconformity is an irregular surface having as much as 200 m of 

section removed by erosion locally and as much as 20 m of 

local erosional relief (Crowder, 1990). The contact between 

the Lisburne Group and Echooka Formation is typically 

planar; carbonate rocks of the Lisburne Group are overlain 

by terrigenous siltstone, shale, and (or) glauconitic quartzose sandstone of the Echooka Formation (Crowder, 1990). 

Locally, erosional relief is most apparent beneath channelized conglomerates in the basal part of the Echooka Formation. Clasts in the conglomerates include limestone and 

chert derived from the Lisburne Group providing additional

evidence of erosion. Even though the Lisburne Group platform was subaerially exposed, karst features are rare (Carlson, 1990; Watts, 1990; Watts and others, 1992). Erosion 

along the disconformity produced some of the variation in 

thickness of the Wahoo Limestone and significantly influenced the age of the uppermost part of the formation. At the 

study section, the formation is not as thick as at the type 

section (262 m versus >330 m in thickness), but the uppermost part of the formation is as young as or younger than 

the highest beds at and near the type section (app. 1, Iocs. 

4E, D). In some areas, such as near the Trans-Alaska Pipeline (fig. 1), the upper part of the Lisburne Group is no 

younger than latest Mississippian (Watts, 1991).

LITHOSTRATIGRAPHY OF

THE WAHOO LIMESTONE,

EASTERN SADLEROCHIT MOUNTAINS

The study section is near the eastern limit of outcrops 

of the Wahoo Limestone in the Sadlerochit Mountains (fig. 

2). The base of the section is in the SE1/4SW1/4 sec. 5, T. 3 

N., R. 31 E. (lat 69°38'24" N., long 144°34'45" W), and the
10 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

top is in the center NW1/4 sec. 8, T. 3 N., R. 31 E. (lat 

69°38'03" N., long 144°34'45" W.), Mt. Michelson C-l 

quadrangle. This section was chosen because of (1) accessibility by helicopter (65 km southwest of Kaktovik; fig. 1), 

(2) proximity to measured sections described by previous 

workers (Armstrong and others, 1970; Wood and Armstrong, 1975; and Carlson, 1987) that were less accessible 

for conodont sampling, (3) excellent exposures of the 

Wahoo Limestone (95 percent) and its boundaries (fig. 5), 

and, in particular, (4) the relatively thick interval of upper 

Morrowan and Atokan strata.

Our measured section includes the upper 3 m of the 

Alapah Limestone, the entire Wahoo Limestone (262 m), 

and the basal 1 m of the succeeding Echooka Formation (pi. 

6). The lower 3 m of the Wahoo Limestone is massivebedded dolomitized bryozoan packstone that overlies a 

0.5-m-thick interval of light-gray, fenestral, dolomitic mudstone at the top of the Alapah Limestone. The lower and 

upper members of the Wahoo Limestone are readily distinguished; their boundary is placed at the change from 

cliff-forming, light-gray packstone below to orangeweathering, silty, cryptalgal(?) dolostone above (fig. 5). The 

contact with the overlying Echooka Formation forms a 

rubble-covered dip slope, but only a few meters of section 

are concealed. The section was systematically sampled for 

microlithofacies at 2-m intervals. Additional samples were 

taken to document obvious lithologic changes and at all 

conodont sample sites (table 1; pi. 6).

LOWER MEMBER OF THE WAHOO LIMESTONE

The lower member (Mississippian and Pennsylvanian) 

of the Wahoo Limestone is 70 m thick and is chiefly 

bryozoan-pelmatozoan grainstone and packstone. Rare beds 

of wackestone and skeletal packstone occur particularly in 

the basal part of the lower member and near the 

Mississippian-Pennsylvanian boundary and contain minor 

sponge spicules. Peloids, including completely micritized 

bioclasts, are a common constituent of the lower member 

and become abundant near the boundary. An interval of 

oolitic grainstone, 62 to 64 m above the base of the lower 

member, is the lowest occurrence of a lithology that typifies 

the upper member. Dark-gray replacement chert nodules are 

common throughout (pi. 6).

The lower member of the Wahoo Limestone formed on 

a predominantly open-marine platform that developed 

above restricted-platform carbonate deposits of the upper 

part of the Alapah Limestone (see fig. 9). Muddy and spiculitic limestone in the lower several meters of the Wahoo 

Limestone formed in partly restricted conditions during the 

early phase of a major transgression. The upper 25 m of the 

lower member primarily formed in normal-marine conditions, but common to abundant peloids and minor spicules 

suggest intermittent restriction; locally abundant ooids

imply proximity to shoals. These grain types indicate the 

onset of regression.

Just below the Mississippian-Pennsylvanian boundary, at 56 m above the base of the lower member of the 

Wahoo Limestone, a distinct interval of peloidal-spiculitic 

wackestone is partly replaced by reddish-brown and gray 

nodular chert. This chert-bearing interval has variable thickness (<0.5 to 1 m), sharp lower and upper contacts, and 

appears to have been deposited above an irregular surface 

with as much as 1 m of relief (fig. 6). The surface has been 

interpreted to have formed during subaerial exposure (Carlson, 1990; Watts, 1990). The chert-bearing interval overlies 

a skeletal grainstone that contains definitive Mississippian 

conodonts within 10 cm of the contact and, in turn, is overlain by a peloidal-skeletal grainstone, the base of which produced the lowest definitive Pennsylvanian conodonts in the 

study section (fig. 6). The chert-bearing interval was traced 

1 km west to Carlson's (1987) section where Declinognathodus noduliferus japonicus, an index to the Pennsylvanian, occurs 1.5 m below the chert (app. 1, loc. IBlb), 

suggesting at least 1.5 m of erosion at the study section.

A comparable chert-rich interval was noted in Lower 

Pennsylvanian rocks (based on foraminiferan biostratigraphy) in the western Sadlerochit Mountains (Clough and 

Bakke, 1986; Imm, 1986). Correlation of this interval with 

the eastern Sadlerochit Mountains, however, has not been 

verified with conodonts. A chert-rich interval has not been 

noted in a similar stratigraphic position in sections to the 

south or east.

The contact between the lower and upper members of 

the Wahoo Limestone appears planar. Redeposited, latest 

Mississippian conodonts occur sporadically in the Pennsylvanian part of the lower member and increase in abundance 

a meter below the contact with the upper member (table 1). 

The redeposited conodonts indicate intermittent reworking 

of slightly older deposits of the Wahoo Limestone.

UPPER MEMBER OF THE WAHOO LIMESTONE

The upper member of the Wahoo Limestone is 192 m 

thick at the study section and contains many shallowingupward parasequences. These parasequences are superimposed on a major TR sequence.

The lower 24 m of the upper member is dominated by 

peloidal-bryozoan packstone, dolomitized silty mudstone, 

and wackestone. Cryptalgal laminites are poorly developed 

in the study section but are present in nearby exposures. 

Shallowing-upward parasequences in this interval begin 

with peloidal-bryozoan packstone (minor grainstone) and 

pass upward into dolomitized, silty, locally spiculitic, lime 

mudstone. Detrital quartz is relatively abundant (as much as 

40 percent), particularly in dolomitic mudstone. Significantly, quartz sand increases from 3 to 4.5 percent in the 

upper meter of the lower member and then abruptly rises to
LITHOSTRATIGRAPHY OF THE WAHOO LIMESTONE, EASTERN SADLEROCHIT MOUNTAINS 11

Figure 6. Mississippian-Pennsylvanian boundary beds in upper 

part of lower member of the Wahoo Limestone at the study section 

showing the distinct reddish-brown and gray, nodular chert-bearing interval (arrows mark its top and bottom). Thickness of beds 

shown is approximately 4 m. Conodont samples at locations A-D. 

Sample A, 53 m above base of the Wahoo (table 1, USGS colln. 

30757-PC), contains Gnathodus girtyi girtyi, G. g. simplex, and 

forms transitional to Declinognathodus spp. as well as 

C. bilineatus bilineatus, Hindeodus minutus, Vogelgnathus postcampbelli, and Kladognathus sp. Sample B, 54.9 m above base of 

formation (table 1, USGS colln. 31698-PC), contains Mississippian species including C. g. girtyi, Kladognathus spp., and 

Lochriea commutata as well as subadult Pa elements of C. g. simplex transitional to D. noduliferus japonicus and abundant Cavusgnathusl tytthus of Mississippian and Pennsylvanian age. Sample 

C, 55.5 m above the base and within the cherty interval (table 1, 

USGS colln. 31699-PC), produced only a few conodonts, chiefly 

C.I tytthus of Mississippian and Pennsylvanian age. In sample D, 

56 m above base of formation, D. n. japonicus (pi. 3, figs. 4-8), an 

index to the Pennsylvanian, occurs with several other species 

known to range across the Mississippian-Pennsylvanian boundary 

(table 1, USGS collns. 30758-PC and 31700-PC). Collections 1 

km to the west yielded Pennsylvanian conodonts 1.5 m below 

reddish-brown and gray chert-bearing interval suggesting that the 

irregular surface at base of chert is a disconformity that probably 

marks the Mississippian-Pennsylvanian boundary at the study section.

an average of 12 percent in the lower 20 m of the upper 

member (percent quartz determined from acid-insoluble 

residues of conodont samples). This sudden increase of terrigenous sediment at and above the lower member-upper 

member contact suggests considerable regression and some 

exposure of the Wahoo platform. Indeed, exposure surfaces 

in the lower part of the upper member and local channelization of cryptalgal laminites at the lower member-upper 

member contact have been described in the eastern Sadlerochit Mountains here and 1 km to the west (Carlson, 1987, 

1990; Watts, 1991). In addition, relatively few conodonts 

and foraminifers are found in this part of the upper member, 

possibly due to inhospitable environmental conditions. 

The lower 24 m of the upper member formed on a
12 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

predominantly restricted platform during a major regression 

and contain some of the shallowest water deposits in the 

Wahoo Limestone (Gruzlovic, 1991).

The succeeding 120 m of the upper member of the 

Wahoo Limestone are characterized by oolitic grainstones, 

particularly the upper part of the member (pi. 6). Bioclasts 

and peloids are common and grapestone lumps, intraclasts, 

and Archaeolithophyllum sp. (algae) are rare to minor in 

these high-energy grainstones and associated packstones. 

Oncolites are most common in the lower part of this interval 

whereas Donezella sp. (algae) occur in the upper part, first 

appearing at 167 m above the base of the Wahoo (P.L. 

Brenckle, written commun., 1991) suggesting some environmental restriction up section. Shallowing-upward 

parasequences typically begin with dolomitic bryozoan 

wackestone and pass upward into dominantly skeletal and 

oolitic grainstone that may be capped by dolomitized, 

locally spiculitic, lime mudstone. Repeated intervals of 

oolitic grainstone represent migration of shoals across the 

Wahoo platform. Oncoids, peloids, grapestone lumps, and 

algae indicate that open-platform depositional environments developed shoreward of the shoals. Rare, isolated 

colonial and solitary corals also occur and are locally associated with spiculitic mudstone and peloids that suggest 

proximity to partly restricted conditions. The abundant 

ooid-shoal deposits in the upper part of this interval correspond with the maximum transgression during deposition of 

the upper member of the Wahoo (Watts, 1990; Gruzlovic, 

1991).

The upper 48 m of the upper member of the Wahoo 

Limestone are chiefly peloidal-oncolitic and bryozoanpelmatozoan packstone and grainstone (pi. 6). Ooids and 

superficial ooids occur in the lower part of the member, representing the last ooid-shoal deposits of the Wahoo. 

Peloidal-spiculitic-oncolitic wackestone and spiculitic mudstone become prevalent approximately 13 m below the top 

of the formation, marking a shift from primarily openplatform to restricted-platform environments.

Persistent sea-level fluctuations during deposition of 

the Wahoo Limestone produced a mosaic of shifting environments that controlled biotic distribution. Conodont and 

foraminiferan biofacies (species associations) reflect these 

environmental changes. Biofacies, as well as postmortem 

transport of skeletal remains, controlled the occurrence of 

biostratigraphically significant species and, ultimately, the 

biozonation of the Wahoo Limestone.

CONODONT BIOSTRATIGRAPHY OF

THE WAHOO LIMESTONE, 

EASTERN SADLEROCHIT MOUNTAINS

The conodont zonation proposed by Lane and Straka 

(1974) and subsequently revised by Lane (1977) and Baesemann and Lane (1985) for uppermost Mississippian and

STUDY SECTION

SYSTEM

) ~s m ( 

iPENNSYLVANIAN ) 

( >

MISSISSIPPIAN

SERIES

x_/~ \_/~ 

LOWER 

ATOKAN

MORROWAN UPPER(OR) LOWER ATOKANND 

MORROWAN

CHESTERIAN 

(PART)

FORMATION/ 

MEMBER

WAHOO LIMESTONE )o m

^1 5-?3S

S° UPPERMEMBER >

LOWER MEMBER

ALAPAH 

LIMESTONE 

(PART)

CONODONT 

ZONE/ 

FAUNA

(262 m)^_/~v_y-x-rFirst appearance v 

of Idiognathodus x

incurvus? 

(246 m)

Idiognathodus 

Fauna

(177m)

1

^~ First appearance 

of Pseudostaffella

03 < 171 m>

c (162m) ——— 

03

05 lower 

-2 minutus 

.c Fauna 

£ 

(84 m)-l ———————

noduliferus - 

primus Zone

(56 m) ——————— 

^- First appearance 

x of G. bulloides 

(43m)

Upper 

(o m) muricatus 

Subzone

CONODONT 

ZONATION 

(Baesemann 

and Lane, 1985)

x_r~v_/-x_y~\_ 

Unzoned

Idiognathoides 

ouachitensis

Idiognathoides 

convexus

Idiognathodus 

klapperi

Idiognathodus 

sinuosus

Neognathodus 

bassleri

Neognathodus 

symmetricus

Idiognathoides 

sinuatusRhachistognathus 

minutus

Declinognathodus 

noduliferusRhachistognathus 

primus

Upper 

Rhachistognathus 

muricatus 

Subzone

Figure 7. Conodont zonation/faunal succession recognized in 

the Wahoo Limestone at study section compared to the North 

American middle Carboniferous conodont zonation of Baesemann 

and Lane (1985). Zonal indicators of Baesemann and Lane not 

found at study section include Neognathodus symmetricus, N. 

bassleri, Idiognathodus klapperi, and Idiognathoides convexus. 

Declinognathodus noduliferus first appears 13 m above Globivalvulina bulloides, the foraminiferan secondary guide to the midCarboniferous boundary (Lane and Manger, 1985). See figure 6 

and table 1 for detailed information on the MississippianPennsylvanian boundary. Idiognathodus sinuosus first appears 6 m 

above Pseudostaffella sp., a foraminiferan guide to the MorrowanAtokan boundary in the Midcontinent and Cordillera of the conterminous United States (Lane and Manger, 1985; Groves, 1986). 

The Morrowan-Atokan boundary is poorly constrained by conodonts and foraminifers. The foraminifer Pseudostaffella sp. 

appears well below the lowest definitive Atokan conodont, Idiognathodus incurvusl (table 1). G, Globivalvulina.

Pennsylvanian (Morrowan) rocks in North America only 

applies to the conodont succession in the upper part of the 

Alapah Limestone and the succeeding 84 m of the Wahoo 

Limestone (fig. 7). The Upper muricatus Subzone (uppermost Mississippian), the noduliferus-primus Zone (lowermost Pennsylvanian), and the lower part of the succeeding
CONODONT BIOSTRATIGRAPHY OF THE WAHOO LIMESTONE, EASTERN SADLEROCHIT MOUNTAINS 13

minutus Fauna (= sinuatus-minutus and symmetricus Zones 

of Baesemann and Lane, 1985) are well documented in this 

part of the section (table 1 and pi. 6). The remaining Pennsylvanian strata, however, could not be precisely dated by 

using existing conodont zonal schemes (for example, 

Baesemann and Lane, 1985; Gray son, 1990) because of a 

persistent, chiefly rhachistognathid biofacies (high-energy, 

shoal to near-shoal environments) in which most zonal indicators are rare or absent. We have, instead, used a faunal 

designation for this part of the Wahoo Limestone based on 

possible local ranges of some rhachistognathids and what is 

almost certainly a relatively late migration of Idiognathodus 

into northeast Alaska. Some of the rhachistognathids that 

appear before or originate in the lower 84 m of the Wahoo 

Limestone disappear before the lowest occurrence of Idiognathodus in the northeast Brooks Range; other rhachistognathids persist to the major unconformity that truncates the 

formation (pi. 6). Rare, sporadic occurrences of generally 

poorly preserved, nonrhachistognathid species are not originations but are clearly the result of postmortem hydraulic 

admixture from other biofacies and can be used to roughly 

tie the northeast Alaskan succession to successions in other 

parts of North America.

Species diversity is rather low for a section that spans 

at least 10 million years, from the latest Chesterian to at 

least early Atokan. Only 24 species, distributed among 14 

genera, were identified in 72 productive samples. Further 

complicating establishment of a reliable conodont succession for part of the Wahoo Limestone is the menace of redeposition. Several samples from the post-Mississippian part 

of the study section (table 1 and pi. 6), as well as many 

other spot samples from the uppermost part of the Wahoo 

Limestone in the northeast Brooks Range, produced redeposited Mississippian and earliest Pennsylvanian conodonts 

that cast some doubt on the biostratigraphic integrity of species distribution in the upper part of the formation.

The conodont zones of Baesemann and Lane (1985) 

and the conodont faunal succession established in the 

Wahoo Limestone and upper part of the Alapah Limestone 

at the study section and elsewhere in the northeast Brooks 

Range are described below.

MURICATUS ZONE

The muricatus Zone is defined by the first appearance 

of Rhachistognalhus muricatus below the occurrence of 

either Declinognathodus noduliferus or R. primus (Lane 

and Straka, 1974; Baesemann and Lane, 1985). Baesemann 

and Lane (1985) proposed a phylogeny for the rhachistognathids of the middle Carboniferous in which R. prolixus is 

the inferred ancestor. They suggested that R. prolixus probably gave rise to R. muricatus after the appearance of 

Adetognathus unicornis (= Cavusgnathus monocerus 

[Rexroad and Burton] of Brown and others, 1990) the name

bearer of the preceding conodont zone. Baesemann and 

Lane (1985) subdivided the muricatus Zone into lower and 

upper subzones. The muricatus Zone is the most widely recognized conodont zone in the Chesterian part of the 

Lisburne Group in the northeast Brooks Range. It is represented by a very thick sequence that may include much of 

the Alapah Limestone and part of the Wahoo Limestone and 

is well documented in nine sections between Atigun River 

gorge and the Clarence River (fig. 1; A.G. Harris and A.P. 

Krumhardt, unpub. data). At and near the study section, the 

muricatus Zone is at least 155 m thick and ranges from 

about 24 m above the base of the Alapah Limestone (app. 1, 

loc. 1A2) to 55.5 m above the base of the Wahoo Limestone 

(table 1, USGS colln. 30757-PC). It is apparently thickest 

(250 m) in the Romanzof Mountains (app. 1, Iocs. 9Bla, b). 

In the area of the type section of the Wahoo Limestone, the 

upper 70 m of the Alapah Limestone and lower 140 m of 

the overlying Wahoo Limestone are within the muricatus 

Zone (app. 1, Iocs. 4Ala, c).

LOWER MURICATUS SUBZONE

The Lower muricatus Subzone is defined by the first 

appearance of the zonal indicator below the occurrence of 

Adetognathus lautus. This subzone has not yet been identified at the study section or in our other collections from 

northern Alaska but may be present in the Alapah Limestone. As proposed (Baesemann and Lane, 1985), the subzone can be identified only in closely sampled sections of 

appropriate shallow-water, relatively normal-marine biofacies. Virtually all common associates of this biofacies in the 

Lower muricatus Subzone, with the possible exception of 

Hindeodus cristulus (Youngquist and Miller), extend or 

likely extend into the Upper muricatus Subzone (table 1; 

Weibel and Norby, 1992). Thus, the only guide to this zone 

is the presence of A. lautus in definitive pre-Pennsylvanian 

strata above the occurrence of Rhachistognathus muricatus 

with H. cristulus.

UPPER MURICATUS SUBZONE

This subzone is defined by the overlapping ranges of 

Rhachistognathus muricatus and Adetognathus lautus 

below the appearance of Declinognathodus noduliferus or 

R. primus. As yet, R. muricatus has not been found in the 

upper 64 m of the Alapah Limestone or the succeeding 

lower 5 m of the Wahoo Limestone in the eastern Sadlerochit Mountains. Representatives of the species were recovered 6 m above the base of the formation and well below D. 

noduliferus (table 1). Adetognathus lautus, although not 

found in the lower 84 m of the Wahoo Limestone, was 

recovered from the Alapah Limestone at 72 and 65 m below 

the base of the Wahoo Limestone at the study section (app. 

1, Iocs. lAla, b). Thus, the Upper muricatus Subzone is
14 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

present at a level considerably below the base of the Wahoo 

Limestone and is at least 127 m thick (from 72 m below the 

top of the Alapah Limestone to 56 m above the base of the 

Wahoo Limestone).

Species that occur within the Upper muricatus Subzone in the Alapah and Wahoo Limestones in the study section include, in order of decreasing abundance, 

Cavusgnathus unicornis Youngquist and Miller, Kladognathus spp., Gnathodus girtyi simplex Dunn, G. g. girtyi 

Hass, Hindeodus minutus (Ellison), Rhachistognathus 

muricatus (Dunn), Vogelgnathus postcampbelli (Austin and 

Husri), C.I tytthus Brown and Rexroad, G. bilineatus bilineatus (Roundy), Idioprioniodus spp., AdeTognathus lautus 

(Gunnell) (see app. 1, Iocs. lAla, b), Lochriea commutata 

(Branson and Mehl), G. girtyi subspp. transitional to Declinognathodus spp., C. altus Harris and Rollings worth, R. 

prolixus Baesemann and Lane?, and Gnathodus defectus 

Dunn?.

Cavusgnathus monocerus (Rexroad and Burton), a relatively common component of the R. muricatus Zone as 

well as the name bearer of the preceding conodont zone, is 

notably absent in the Brooks Range.

The Upper muricatus Subzone is recognized in the 

upper part of the Alapah Limestone and lower part of the 

Wahoo Limestone in six sections (including the study section) between Wahoo Lake and the Clarence River. The subzone is thickest (at least 133 m) at Clarence River and 

includes at least the upper 53 m of the Alapah Limestone 

and the lower 80 m of the Wahoo Limestone (app. 1, Iocs. 

lOAla-e) and at least 124.5 m near Wahoo Lake (app. 1, 

Iocs. 4Alb, c). The only other species found in the subzone 

in the northeast Brooks Range, but not in the study section, 

is Rhachistognathus websteri Baesemann and Lane (app. 1, 

loc. 4Alc).

NODULIFERUS-PRIMUS ZONE

Baesemann and Lane (1985) modified the primus 

Zone of Lane and Straka (1974) to the noduliferus-primus 

Zone, the lower boundary of which marks the base of the 

Morrowan Series and the Pennsylvanian System. Whereas 

Rhachistognathus primus has not been found outside of 

North America, Declinognathodus noduliferus has a worldwide distribution and has been recommended as the primary 

micropaleontologic guide for the base of the Pennsylvanian 

(Lane and Manger, 1985). The noduliferus-primus Zone is 

recognized by the occurrence of either D. noduliferus or R. 

primus below the appearance of R. minutus or Idiognathoides sinuatus Harris and Hollingsworth. The zone was 

subdivided into lower and upper subzones by Brenckle and 

others (1977). The lower subzone is characterized by "the 

overlap in the upper ranges of Gnathodus girtyi simplex and 

G. cf. G. bollandensis with the lower ranges of R. primus 

and D. noduliferus" (Baesemann and Lane, 1985, p. 100).

We assume that G. cf. G. bollandensis of Baesemann and 

Lane (1985) is G. bilineatus bollandensis of other workers 

or a form close to it. Gnathodus girtyi simplex has been 

reported together with D. noduliferus in Nevada (Baesemann and Lane, 1985). In our study section, G. g. girtyi and 

G. g. simplex occur relatively consistently in the lower 

54.9m of the Wahoo Limestone, 1.1 m below the first 

occurrence of D. noduliferus japonicus (table 1). Neither 

subspecies has been recovered from the succeeding 10 m, 

but 4 and 5 m higher G. g. girtyi reappears together with G. 

b. bilineatus and Kladognathus spp. as well as other species 

(table 1). We believe that these typical Mississippian forms 

are redeposited. Significantly, Carlson (1987) reported 

channelization at this level about 1 km to the west. It is possible that other Pennsylvanian occurrences of G. g. girtyi 

are also redeposited, as shown for the Granite Mountain, 

Utah section, by Wardlaw (1984). Gnathodus bilineatus 

bollandensis has not been recognized in the study section 

and G. g. simplex does not occur in the noduliferus-primus 

Zone here. Thus, we cannot recognize the subdivisions of 

the noduliferus-primus Zone at the study section. Elsewhere 

in the northeast Brooks Range, G. g. simplex is a rare, possibly indigenous constituent of the noduliferus-primus Zone 

(app. 1, Iocs. 5b, IBle).

Species that occur in the noduliferus-primus Zone in 

the study section include, in order of decreasing abundance, 

Cavusgnathusl tytthus, Declinognathodus noduliferus 

japonicus (Igo and Koike), Rhachistognathus muricatus, 

Hindeodus minutus, D. n. noduliferus (Ellison and Graves), 

Vogelgnathus postcampbelli, Idioprioniodus conjunctus 

(Gunnell)?, R. websteri, and Gnathodus girtyi subspp. transitional to Declinognathodus spp. Rhachistognathus primus 

has not been identified in this zone in our section but has 

been found elsewhere in the zone in the northeast Brooks 

Range (app. 1, loc. 4B). Additional guides for the 

noduliferus-primus Zone in the northeast Brooks Range are 

Cavusgnathusl tytthus and Vogelgnathus postcampbelli 

with or above D. noduliferus (table 1). Cavusgnathusl tytthus extends to near the top of the zone, is common, and 

appears to occupy the habitat of Adetognathus lautus, which 

is notably absent in this zone in collections in the northeast 

Brooks Range; V postcampbelli has a similar range but is 

rare in the study section. Only 1 km to the west, V. postcampbelli is relatively abundant (app. 1, loc. IBlg). Other 

species found in the zone in the northeast Brooks Range, 

but not in the study section, are G. girtyi simplex (app. 1, 

Iocs. 4B, 4Ald, 5a) and R. prolixus (app. 1, loc. 5a).

Beds 56 to 84 m above the base of the Wahoo Limestone in the study section are representative of the 

noduliferus-primus Zone (table 1). The zone is recognized 

within the lower member of the formation in three other 

sections, as far west as Wahoo Lake. These are (1) the Sunset Pass section (app. 1, Iocs. IBlb-g); (2) the Pogopuk 

Creek section (app. 1, Iocs. 5a, b), where the zone is thickest 

in the northeast Brooks Range (at least 80 m) and where the
CONODONT BIOSTRATIGRAPHY OF THE WAHOO LIMESTONE, EASTERN SADLEROCHIT MOUNTAINS 15

highest sample in the zone contains Gnathodus girtyi simplex suggesting a level presumably within the lower part of 

the zone; and (3) in the vicinity of the type section near 

Wahoo Lake (app. 1, Iocs. 4Ald, 4B).

MINUTUS FAUNA

Considerable controversy surrounds the time of origin 

of Rhachistognathus minutus. Baesemann and Lane (1985) 

proposed a phylogeny for rhachistognathids in which R. 

minutus evolved from R. muricatus some time after the 

appearance of R. primus and Declinognathodus noduliferus. 

Lane and others (1985b) noted that Higgins (1975) reported 

R. minutus below the first appearance of D. noduliferus in 

the Craven basin, northern England. In order to explain the 

succession of rhachistognathids in chiefly shallow-water 

carbonate rocks of North America, a hiatus was inferred in 

the Craven basin succession encompassing the interval of 

the North American unicornis, muricatus, noduliferusprimus, and most of the sinuatus-minutus Zones (Lane and 

others, 1985b). However, Riley and others (1987) demonstrated persuasively that R. minutus appears substantially 

later in North America than in northern England. Manger 

and Sutherland (1992) support the interpretation of Riley 

and others (1987) in their comprehensive summary of this 

controversy. We agree that the appearance of R. minutus in 

many areas of North America is a migration event, so that 

the lower boundary of the sinuatus-minutus Zone (based on 

R. minutus) is diachronous from England to North America. 

Rhachistognathus minutus has a very short range in 

England but is relatively long ranging and widespread in the 

Cordillera of North America (including Alaska) where it is 

most abundant in high-energy, shallow-water deposits. 

According to Baesemann and Lane (1985), R. minutus 

extends into at least the lower Atokan.

We are introducing a minutus Fauna to identify the 

local range of Rhachistognathus minutus subspp. below the 

range of Idiognathodus spp. The lower boundary of this 

fauna undoubtedly varies within the northeast Brooks 

Range because its distribution is biofacies dependent. The 

sinuatus-minutus Zone of Baesemann and Lane (1985) is 

not used because Idiognathoides sinuatus (as defined by 

Grayson and others, 1990) was found in only a single sample high in the study section (table 1). Furthermore, the succeeding symmetricus Zone (as used by Lane and Straka, 

1974) cannot be recognized because of the apparent 

absence of the zonal indicator in the Brooks Range. In the 

western Canada sedimentary basin of the Canadian Cordillera, Higgins and others (1991) recognize a minutus Zone 

that includes the sinuatus-minutus and symmetricus Zones 

of Baesemann and Lane (1985) because of the absence of 

Idiognathoides sinuatus and Neognathodus symmetricus in 

their sections. The minutus Zone of western Canada contains diverse rhachistognathids and is probably equivalent

to the lower part of our minutus Fauna. Indeed, we recognize a lower subdivision of the minutus Fauna by the overlapping ranges of R. minutus subspp. and R. websteri. In our 

section, R. websteri ranges slightly higher than R. muricatus. Baesemann and Lane (1985) indicate that R. websteri 

does not occur above their symmetricus Zone in North 

America, and they show R. muricatus extending into the 

lower Atokan. According to J.F. Baesemann and H.R. Lane 

(oral commun., 1992), R. muricatus may be absent from the 

upper Morrowan part of the Wahoo Limestone and is rare in 

the post-Morrowan part. These late forms of the species are 

small and atypical of early R. muricatus. The only small 

rhachistognathids from the highest part of the Wahoo Limestone are juveniles of R. minutus that occur with adults of R. 

minutus subspp. (table 1, USGS colln. 30800-PC).

In our section, the upper limit of the minutus Fauna is 

defined by the first appearance of Idiognathodus sp., 177 m 

above the base of the Wahoo Limestone (15m above the 

disappearance of Rhachistognathus websteri; table 1). The 

upper 15 m of the minutus Fauna contains few conodonts; 

most samples have a few specimens each of Declinognathodus noduliferus subspp., R. minutus subspp., and Adetognathus lautus. These upper 15 m may be equivalent to part 

of the Idiognathodus Fauna. Similarly, many other collections from single-sample localities or partial sections in the 

northeast Brooks Range contain R. minutus subspp. above 

or with D. noduliferus subspp. and (or) R. primus and lack 

R. muricatus, R. websteri, and idiognathodids. Such collections have been assigned to the minutus Fauna although, 

similar to the upper 15 m of the minutus Fauna in the study 

section, they could be equivalent to the Idiognathodus 

Fauna. For example, about 10 km north of Wahoo Lake, 

samples from the upper 132 m of the Wahoo Limestone 

contain R. minutus subspp., R. primus, D. n. noduliferus, 

adetognathids, and idioprioniodids and are assigned to the 

minutus Fauna (app. 1, Iocs. 4Cla-c).

In the northeast Brooks Range, the minutus Fauna is 

thickest (93 m) in the eastern Sadlerochit Mountains (table 

1) and is at least 70 m thick at Katakturuk gorge, western 

Sadlerochit Mountains (app. 1, Iocs. 2a-g).

The foraminifers Pseudostaffella sp. and Eoschubertella sp. first appear in the upper part of the minutus Fauna 

at 171 m and 175 m above the base of the Wahoo Limestone, respectively (P.L. Brenckle, written commun., 1991). 

These species are used to approximate the base of the Atokan in much of North America (Groves, 1986). Their first 

occurrence in Alaska relative to the Morrowan-Atokan 

boundary remains uncertain, and conodonts provide no 

additional control.

LOWER MINUTUS FAUNA

The lower subdivision of the minutus Fauna is defined 

by the local overlapping ranges of Rhachistognathus
16 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

muricatus, R. websteri, and R. minutus subspp. below the 

range of Idiognathodus spp. (pi. 6). In the northeast Brooks 

Range, this faunal interval contains the greatest diversity 

and abundance of rhachistognathids. Associated conodonts 

within the lower minutus Fauna in the study section include, 

in order of decreasing abundance, Rhachistognathus muricatus, R. minutus minutus (Higgins and Bouckaert), Adetognathus lautus, R. m. havlenai Baesemann and Lane, R. 

websteri, Declinognathodus noduliferus noduliferus, R. m. 

declinatus Baesemann and Lane, A. spathus, D. n. japonicus, Idioprioniodus spp., Hindeodus minutus, Gnathodus 

defectus, and R. prolixusl. The interval contains a few specimens of Kladognathus spp. in one sample, which we consider redeposited. No additional species have been 

recognized within the lower minutus Fauna in our many 

collections from the northeast Brooks Range.

Rhachistognathus websteri and R. muricatus do not 

occur above the lower minutus Fauna in the study section 

(table 1). Rhachistognathids generally maintain their dominance higher in the section, but with reduced diversity; R. 

m. declinatus is the most abundant rhachistognathid above 

the lower minutus Fauna. The lower minutus Fauna is likely 

Morrowan in age because the foraminiferan guides to the 

base of the Atokan occur in the upper part of the minutus 

Fauna. The lower minutus Fauna roughly correlates with the 

sinuatus-minutus to symmetricus Zones of Baesemann and 

Lane (1985; fig. 7, this report).

Rhachistognathus minutus appears 84 m above the 

base of the Wahoo Limestone (14 m above the base of the 

upper member) and R. websteri disappears 78 m higher in 

the study section (table 1). At Katakturuk River gorge, in 

the western Sadlerochit Mountains (fig. 2, loc. 2), at least 

34.5 m of the Wahoo Limestone contain the lower minutus 

Fauna (app. 1, Iocs. 2a-d). The fauna is also present in a 

43.5-m-thick interval in the lower member of the formation 

at Pogopuk Creek (app. 1, Iocs. 5c-e) and in a single sample 

from the upper member in the Clarence River area (app. 1, 

loc. lOAlf).

IDIOGNATHODUS FAUNA

This fauna is characterized chiefly by the association 

of Idiognathodus spp., Rhachistognathus minutus subspp., 

and Adetognathus lautus; the first appearance of 

Idiognathodus spp. in the Wahoo Limestone marks its lower 

boundary. The upper boundary cannot be defined biostratigraphically but is placed at the unconformity that separates 

the Wahoo Limestone from the overlying Echooka Formation (Permian). The lower boundary could be as old as the 

sinuosus Zone (late Morrowan) of Baesemann and Lane 

(1985) or as young as early Atokan. At least half the idiognathodids in our collections from the northeast Brooks 

Range cannot be determined to species because of poor 

preservation. Many of the rocks that produce abundant

Idiognathodus are high-energy oolitic to skeletal grainstones resulting in incomplete and moderately to extremely 

abraded specimens. Most of the better preserved specimens 

are assigned to /. sinuosus Ellison and Graves following the 

species concept of Grayson and others (1989; 1990). This 

species ranges from the base of the sinuosus Zone (upper 

Morrowan) to at least the Upper Pennsylvanian; it ranges 

from 187 to 243 m above the base of the Wahoo Limestone 

in our section (table 1) and above the lowest occurrence of 

Pseudostaffella sp. (fig. 7). If the latter approximates the 

base of the Atokan in Alaska, then the first occurrence of 

/. sinuosus (16m higher in the study section) is in the early 

Atokan and considerably later than its debut in the type 

Morrowan in Arkansas. Two specimens from 246 to 250 m 

above the base of the Wahoo Limestone are assigned to 

/. incurvus Dunn? sensu Grayson and others (1989) 

(table 1). Idiognathodus incurvus is restricted to the Atokan 

and lower Desmoinesian (Grayson and others, 1989); therefore, the upper 16 m of the Idiognathodus Fauna in the 

study section is probably no older than Atokan. In addition, 

R. minutus subspp., identified in samples from the uppermost part of the Wahoo Limestone, is not known to extend 

above the lower Atokan (Baesemann and Lane, 1985). 

Therefore, the top of the Idiognathodus Fauna in our section 

is considered no younger than early Atokan in age.

Conodonts that occur in the Idiognathodus Fauna in 

the study section include, in order of decreasing abundance, 

Rhachistognathus minutus declinatus, Declinognathodus 

noduliferus noduliferus, Idiognathodus sinuosus, Adetognathus lautus, D. n. japonicus, R. m. havlenai, R. m. minutus, A. spathus, Idioprioniodus spp., Hindeodus minutus, 

Idiognathoides sinuatus (Harris and Hollingsworm), Idiognathodus incurvusl, Diplognathodusl ellesmerensisl', and 

Neognathodusl sp. indet. Taken together, our many collections from the Idiognathodus Fauna from elsewhere in the 

northeast Brooks Range have fewer species than the study 

section (see app. 1).

The Idiognathodus Fauna is widespread in the uppermost part of the Wahoo Limestone across the northeast 

Brooks Range, from the Philip Smith Mountains to the 

Yukon (fig. 1). Some of the localities (see app. 1) that produced this fauna include [samples are from the upper 1 m of 

the Wahoo Limestone, except as noted] (1) northwestern 

Philip Smith Mountains (Iocs. 3A, B), (2) 4.5 m below the 

top of the Wahoo Limestone near its type section, Philip 

Smith Mountains (loc. 4D), (3) Pogopuk Creek, Franklin 

Mountains (loc. 5f), (4) central Fourth Range (loc. 7b), (5) 

central Shublik Mountains (loc. 8), (6) 6-m-thick interval in 

upper part of the Wahoo Limestone (Iocs. 2h, i) and the 

uppermost (loc. 2j) beds, Katakturuk River gorge, western 

Sadlerochit Mountains, (7) eastern Sadlerochit Mountains 

(loc. 1C), (8) central Romanzof Mountains (loc. 9A), (9) 

upper 45 m of the Wahoo Limestone, Clarence River, northern British Mountains, Alaska (Iocs. lOAlg, h), and (10) 

near the top of Wahoo Limestone, northern British Moun-
THE MID-CARBONIFEROUS BOUNDARY 17

tains, Alaska-Yukon border (loc. 10B; figs. 1, 2). The Idiognathodus Fauna may extend lower at localities that represent single collections

THE MID-CARBONIFEROUS 

BOUNDARY—AN APPROXIMATION

OF THE MISSISSIPPIANPENNSYLVANIAN BOUNDARY

BIOSTRATIGRAPHIC CRITERIA

Three major fossil groups, ammonoids, foraminifers, 

and conodonts, have been used for zoning the Carboniferous and as guides to the mid-Carboniferous boundary 

(Sutherland and Manger, 1984b; Manger and Sutherland, 

1992). In 1983, the Subcommission on Carboniferous 

Stratigraphy (SCCS) approved several recommendations 

regarding the various biostratigraphic criteria for establishing an international mid-Carboniferous boundary (Lane and 

Manger, 1985). These include—

(1) The transition between the Eumorphoceras and 

Homoceras ammonoid zones. Homoceras, however, is 

geographically restricted and not useful for global correlations.

(2) The first appearance of the conodont Declinognathodus 

noduliferus, preferably together with its ancestor Gnathodus girtyi simplex.

Secondary guides to the boundary include the first 

appearance of the conodonts Adetognathus lautus, Rhachistognathus primus, and R. minutus and the foraminifers 

Globivalvulina sp. D of Brenckle (=G. moderata = G. 

bulloides; PL. Brenckle, oral commun., 1991), Millerella 

pressa Thompson, and M. marblensis Thompson.

These recommendations are not yet ratified because a 

stratotype has not been selected. Nevertheless, the recommendations of the SCCS are useful for defining the 

mid-Carboniferous boundary in marine successions (Lane 

and others, 1985b; Riley and others, 1987) and are followed 

here.

The faunal succession across the mid-Carboniferous 

boundary in North America and elsewhere has been extensively documented (for example, Ziegler and Lane, 1985; 

Brenckle and Manger, 1990; Sutherland and Manger, 1992). 

The lithofacies and conodont succession in our section are 

most like those described from Nevada, Utah, and Montana 

(Wardlaw, 1984; Baesemann and Lane, 1985; Davis and 

Webster, 1985; Morrow and Webster, 1991, 1992). These 

studies, however, indicate significant inconsistencies in 

conodont distribution and possible misinterpretations of 

depositional continuity that affect zonal schemes. For 

example, in the Arrow Canyon section, Nevada, Baesemann 

and Lane (1985) place the Mississippian-Pennsylvanian 

boundary at the simultaneous first occurrence of Declinognathodus noduliferus, Rhachistognathus primus, and R.

websteri immediately above beds containing Adetognathus 

lautus, R. muricatus, and Gnathodus girtyi simplex. Gnathodus girtyi simplex occurs in 10 samples taken through a 

6-m-thick interval above the boundary (Baesemann and 

Lane, 1985, fig. 2). Thus, beds representing the Upper muricatus Subzone are overlain by beds representing the Lower 

noduliferus-primus Zone. Their lithic column shows a 

2-m-thick clastic-rich interval less than 1 m above the 

boundary that occurs in a limestone. According to field 

observations made by K.F. Watts in 1989, the systemic 

boundary lies at a lithic change from crinoidal 

packstone-grainstone to packstone having a greenish matrix 

and sand-filled burrows in its uppermost part. The clastic 

interval less than 1 m above the boundary contains a variety 

of lithologies including mixed-pebble conglomerate in a 

carbonate and lesser quartz sand matrix and flat-pebble conglomerate. These features suggest a change in depositional 

regime, possibly beginning at the boundary but certainly 

occurring less than 1 m above it. The first appearance of 

Declinognathodus and new species of Rhachistognathus 

may be a migration event related to changing environmental 

factors associated with the lithic changes. Conodont collections made by B.R. Wardlaw and R.G. Stamm (U.S. Geological Survey, unpub. data), at 0.5-m intervals from 14.5 m 

below to 2 m above the boundary as designated by Baesemann and Lane (1985) reveal additional problems. In these 

collections, R. primus is limited to one sample 4 m below 

the only sample containing D. noduliferus (taken at the systemic boundary). Thus, in Arrow Canyon, R. primus 

appears before, rather than together with, D. noduliferus.

At Granite Mountain, Utah, Morrow and Webster 

(1992) report the appearance of Rhachistognathus primus 9 

m below the first Declinognathodus noduliferus. They place 

the Mississippian-Pennsylvanian boundary at the first 

occurrence of D. noduliferus on the basis of comparisons to 

other localities where R. primus occurs below D. noduliferus. We agree with Morrow and Webster (1991) that the 

rarity of D. noduliferus and gnathodids at Granite Mountain 

is biofacies related and that the first appearance of D. noduliferus is a migration event. We do not, however, agree with 

their placement of the primus Zone interval in the Mississippian (Morrow and Webster, 1992), as it could just as well 

be partly or entirely Pennsylvanian in age.

As documented above, our own and published data 

suggest Rhachistognathus primus evolved shortly before 

Declinognathodus noduliferus. Rhachistognathus primus is 

relatively rare in the northeast Brooks Range. Only one collection contains R. primus not constrained by D. noduliferus; it is assigned to the noduliferus-primus Zone (app. 

l,loc.4B)

The ancestry of Declinognathodus noduliferus, the 

micropaleontologic guide to the base of the Pennsylvanian, 

remains controversial with conflicting evidence indicating 

ancestry from either Gnathodus girtyi simplex or G. bilineatus. Grayson and others (1985b), Grayson and others
18 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

(1990), and Grayson (1990) consider G. bilineatus ancestral 

to D. noduliferus on the basis of apparatus comparisons. 

Indeed, examination of chiefly Pa elements from a proposed 

mid-Carboniferous stratotype section in middle Asia 

strongly supports the G. bilineatus ancestry (Nigmadganov 

and Nemirovskaya, 1992a, 1992b; Nemirovskaya and 

Nigmadganov, 1994). Our data, however, are equally convincing for a G. g. simplex ancestry (see below). The controversy concerning the ancestry of D. noduliferus may be 

the result of homeomorphy. Pa elements documenting the 

evolution of G. bilineatus bollandensis to G. postbilineatus 

to D. praenoduliferus and, finally, to D. noduliferus noduliferus (Nigmadganov and Nemirovskaya, 1992a; 

Nemirovskaya and Nigmadganov, 1994) are just as convincing as those documenting the evolution of G. girtyi simplex to D. n. japonicus and (or) D. n. noduliferus (Dunn, 

1970b; this report). It may be that the Pa elements presently 

recognized as those of D. noduliferus are polyphyletic.

Presently, the leading candidate section for the midCarboniferous boundary stratotype is in Arrow Canyon, 

Nev. (Baesemann and Lane, 1985). The first appearance of 

Declinognathodus noduliferus inaequalis, D. n. japonicus, 

or D. n. noduliferus in the section marks the midCarboniferous boundary and will be used to mark the base 

of the Pennsylvanian System.

CONODONT-BASED BOUNDARY IN THE 

EASTERN SADLEROCHIT MOUNTAINS

Gnathodus girtyi simplex transitional to Declinognathodus noduliferus japonicus first appears at 53 m above the 

base of the Wahoo Limestone (table 1). Additional specimens were found at 54.9 m above the base of the formation, 

immediately below a reddish-brown and gray chert-bearing 

peloidal spiculitic wackestone interval (fig. 6). Declinognathodus noduliferus japonicus first appears immediately 

above the chert-bearing interval, at 56 m above the base of 

the Wahoo Limestone (table 1). The mid-Carboniferous 

boundary may be no higher than 55 m above the base of the 

Wahoo Limestone and below the chert-bearing interval at 

the study section because 1 km to the west (app. 1, Iocs. 

IBla-g) D. n. japonicus is common in a 1.5-m interval 

below a reddish-brown and gray chert-bearing peloidal spiculitic wackestone. The chert-bearing interval can be traced 

between the two localities. Collections from within it contain similar conodont faunules (app. 1, loc. IB If; table 1, 

USGS colln. 31699-PC). Its base is a discontinuity and has 

a relief of at least 1 m. It may be that the 1.5-m interval containing D. n. japonicus below the discontinuity to the west 

was cut out at the study section.

Other, less diagnostic guides to the mid-Carboniferous 

boundary are either rare or absent in the boundary interval. 

Adetognathus lautus does not occur in this interval for environmental reasons but does occur 121 m below it (app. 1, 

loc. lAlb) and 28 m above it (table 1), and Rhachistognathus primus has not been recognized. Additional guides 

include the last appearance of Cavusgnathus spp. at 3 m 

below the boundary and the continuation of C.I tytthus and 

Vogelgnathus postcampbelli to 20.5 m above the boundary. 

A few representatives of species believed to be restricted to 

the Mississippian occur sporadically above the boundary; 

these are shown in table 1 as redeposited.

FORAMINIFERAN-BASED BOUNDARY IN THE 

EASTERN SADLEROCHIT MOUNTAINS

The Mamet and Skipp (1970) foraminiferan zonation 

has been used extensively to correlate the Lisburne Group 

in northern Alaska (for example, Armstrong and others, 

1970, Armstrong and Mamet, 1975, 1977; Dutro, 1987). 

Mamet and Skipp (1970) and subsequent publications by 

Mamet and his co-workers place the mid-Carboniferous 

(Mississippian-Pennsylvanian) boundary coincident with 

the boundary between foraminiferan Zones 19 and 20. The 

base of Zone 20 is defined by the appearance of the 

Lipinella-Millerella sensu stricto assemblage (Armstrong 

and others, 1970). Later, Mamet (1975) amended Zone 20 

to include the first diaphanotheca-bearing Globivalvulina.

Studies in the eastern Sadlerochit Mountains show 

inconsistencies in lithostratigraphic and chronostratigraphic 

boundaries with the foraminiferan zonation (fig. 8). Armstrong's (1972) boundary between the Alapah Limestone

Figure 8. Comparison of lithostratigraphic, biostratigraphic, 

and time-rock boundaries between study section and the nearby 

Sunset Pass section analyzed in previous reports. Prior to Carlson (1987; column 4), all interpretations for the Sunset Pass section (fig. 2, loc. IB) were based on one composite section 

(Armstrong and others, 1970, sections 68A-4A, 4B); Carlson's 

section is along the same traverse. The Alapah LimestoneWahoo Limestone boundary is at the same stratigraphic level in 

columns 2, 4, and 5 but differs from that in columns 1 and 3. 

Foraminiferan zonal boundaries in columns 1-4 were determined by B.L. Mamet; foraminiferan data for column 5 are from 

P.L. Brenckle (b; written commun., 1991) and Sylvie Pinard (p; 

written commun., 1991). In column 5, the first occurrence of the 

diagnostic foraminifer that approximates the base of the Pennsylvanian, Globivalvulina bulloides, is at least 13 m below the 

first Declinognathodus noduliferus. P.L. Brenckle (written commun., 1991) also noted the last occurrence of Brenckleina rugosa well above its known range in the conterminous United 

States (at or very slightly above the base of the Pennsylvanian). 

See figure 6 and table 1 for specific information on the 

Mississippian-Pennsylvanian boundary. The Morrowan-Atokan 

boundary is poorly constrained by conodonts. Pseudostaffella 

sp. is used to approximate this boundary in the Midcontinent and 

Cordillera of the conterminous United States (Lane and Manger, 

1985; Groves, 1986). In the study section, it appears 14 m above 

the lowest occurrence of its plectostaffellid ancestor and 75 m 

below the first definitive Atokan conodont. NML, "No Man's 

Land" as used by B.L. Mamet in Carlson (1987) and Gruzlovic 

(1991).
THE MID-CARBONIFEROUS BOUNDARY 19

5

Study section

o>

"^ c

1

CO

O

32 1

Mamet, Armstrong, 1972,4; and Armstrong others, and rmstrong Wood Armstrong, Mamet 1975; Armstrong and 970; 

1984 Armstrong, 1975 Mamet, 1977 

o o o o _ 

THICKNESS ^ S LO ° S O (METERS) CM CM ^ ,- LD ^

.g —————— ?

pLU „ ^ S~ =5

co 11- S2-S ^^ <u 

O? irj? ^

o 5 § £§ S

< Q; LLJ "- "O

QO S

LL. 05 T 

Q. C

C- (/j

§1 | 1 c |

§1 i 1" «l

N "- '-5 iTS

1 " \

d3aiAI3IAI 

/NOllVIAIdO

• CD C

11 ^ 

^ W ?, CD

ir| ||

^ ^p^ "55 _Q

- o ~— - jj ^^

VI CM< —— —— >

i- Cj CO |ii

o-Z, <a A g 

S 1-5

eunej sninuiiu I

< ——— 

o ~—

CM < ——

S CD y -J ^—

^ CQ O 

Q. O N 

Q_ ^ o

ID 3 ^

jaqoiauj jaddn l*$^^ijjj»ij$t auojsaain ^

J auojsaain ooi)ey\/\ [fcfSI;; ;>s ;K; u.edi2|v ^

on.uno UE>|OJVl UB>|0}V J8MO| (JO) . ipMO 1 iriJAr adlddb J9MO| frue UBMOJJOIAI J8ddn uc/v\vjjj\j|f^

iAi3isAs NVINVAlASNN3d |§

T

C

3NOZ

d39IAI3IAI

/NOIlVIAIdOd •

S3ld3S

IAI31SAS

lower inmember assigned to 

comparison section intoi 

Sunset graphic assignments at 

workers by other 

position Mississippian- of 3boundary for >ylvanian the 

studies s 

w "§ "co w ^ ^ .0

CQ ®i Q- >

:l|||;ipU81S8L|0 X :i|| j

llillldlSSISSIIAI t ^^ 1

48

Si 8

jaqaiaai jaddn |e^p|(w|;ia^}i suoif

auojsaain ooL)ey\/\ if: ;?;;;; *;

UB>|O1V

SSLUHMBdBIV

UBMOJJOIAI flllill UBU81S8MQ

NVINVAlASNN3d lllllil NVIddlSSISSIIAI

i fc-" 1 !-"1 '/ •'!-..'• •'-.-'• ••'••' -'•"•- :•••. '.•-•' .':•'. .'••''. 

/ :^.r. •.••••.^.••.•.rv.-:.>j:^.< ,.. .:,

S/S

/ VL . •' -: -.---^. .^-v-:^.--.-'; -.^-i.-..,- 

/ ^Ji';,;-W^*ftft*;:' / .•,-*0^:SS\L ^-fc-:^

3NOZ

NOIlVIAIdOd

S3ld3S

IAI31SAS

CM CM -;:"? f-^'l ^ J|:^ S

8U01S8LU!1 OOL|BM | -;:|||| gf 8UO1S8UJ!1 MBdB|V

UB>|OIV UBMOJJOIAI llllil||||l UBUSISSLIQ

NVINVAlASNN3d llfl 11 NVIddlSSISSIIAI >>-;:^.iv:*tt ?' ; ;^-r;-^-

T — *

CM C

3NOZ

NOIlVIAIdOd

S3ld3S

IAI31SAS

TM\

M M^^l;:^^

£S!lfeMfc?

.;.:;. ••• .. !•;-• .*:' i'-i :.- .-: >ij:

3 *I

•>v-v"A;: .:v..:^^.'^-^.

8U01S8UJ!1 OOL|BM ll|f|l 1| 8UO1S8UJH MBdB|V

UB>|01V UBMOJJO|/\| ;

"••.•. ''.'•'-... ,"L:

NVINVAlASNN3d If

•-.- '-• •.-•-"

CM C

3NOZ

NOIlVIAIdOd

S3ld3S

IAI31SAS

cvic^

§1

V] ;;;£;.; 

^•Bfl

-...-V.-....-

8UOlS8LUn OOL|B/\/\ HI

UB>|O1V UBMOJJO|/\| I!

NVINVAlASNN3d II

UBU81S8L|0

-.';--^ L ••'" -'•-.-.•'..- .L1 .-"1 . 1 :.-:.^

Ililfl NVIddlSSISSIIAI

liii

.- : - :/:?;':•. :?-.•." ;? 

-^••:;^' *•/;'.;

-'.;v:.V'; i;:.^::;/: ;-;; ^^ ".:.*•"! * :'.-v\:-:.-

-vA'-Ev^S-^-JCi:-

^Bv-tJ^*--^ -^-i---*^-^:'-

1 lllfl 8UO1S8LUH l|BdB|V

1 1 1 II UBU81S8L|Q

lilill NVIddlSSISSIIAI

(Sd313IAl) o

SS3N»OIH1 o

in

o 

o

o 

o

CO

o 

o

CM
20 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

and Wahoo Limestone and his systemic boundary are similar to our results; however, Armstrong and Mamet (1975, 

1977) subsequently changed the position of both boundaries 

(fig. 8). Most of the reports cited in figure 8 use the original 

section measurements and thin sections that were first used 

by Armstrong and others (1970). Carlson's (1987) section is 

at or immediately adjacent to Armstrong's original section 

but was sampled in more detail. Analysis of Carlson's samples by Mamet (in Carlson, 1987) produced results different 

than those in previous reports. The reasons for changing 

lithostratigraphic and chronostratigraphic boundaries, however, were not explained. It is likely that biostratigraphic 

criteria changed, and the formation boundary was moved to 

approximate the systemic boundary.

In the northeast Brooks Range, Mamet and Armstrong 

(1984, p. 435) recognized an "...undetermined interval 

between Zones 19 and 20 [which] represents a very small 

amount of the sedimentation column but is a stratigraphic 

break lacking any characteristic paleontologic association." 

Mamet called this interval "No Man's Land" or NML (in 

Carlson, 1987; in Gruzlovic, 1991; this report, fig. 8). 

According to Mamet (in Clough and Bakke, 1986; in Carlson, 1987), the NML interval is correlative with the 

Mississippian-Pennsylvanian regional unconformity of the 

Midcontinent of North America.

Because foraminifers have been the principal fossils 

used for correlating the Lisburne Group, we were eager to 

tie our conodont biostratigraphy to Mamet's foraminiferan 

zonation. Unfortunately, the original Sunset Pass section 

was not logistically suitable for conodont sampling, but our 

study section, 1 km to the east, is close enough to assure 

lithologic correlation and thus permit comparison of conodont and foraminiferan data. Microlithofacies samples 

were taken every 2 m or less to coincide with conodont 

samples and lithologic changes and were also used for foraminiferan analyses. The conodont-based MississippianPennsylvanian boundary generally does not agree with the 

boundary determined by foraminifers. Figure 8 shows the 

conodont-based boundary at about the same stratigraphic 

level as given in columns 1 and 2, but about 25 m higher 

than in column 3, and about 17 m lower than in column 4 

(see fig. 8 caption for details). If the first appearance of the 

foraminifer Globivalvulina bulloides is used as a guide to 

the base of the Pennsylvanian in our section, the midCarboniferous boundary would be 13 m lower than the 

conodont-based boundary but would still not match other 

levels determined by Mamet using his own zonation (foraminiferan analysis by PL. Brenckle, Amoco Production 

Company, written commun., 1991). Sylvie Pinard (Geological Survey of Canada) analyzed the foraminifers (written 

commun., 1991) in the same thin sections as those examined by PL. Brenckle and placed the boundary 9 m higher 

than his determination (fig. 8; 4 m below the conodontbased boundary).

The last appearance of the foraminifer Brenckleina 

rugosa may be an additional guide to the midCarboniferous boundary in the Cordillera of the conterminous United States where the species disappears at, or 

slightly above, the base of the Pennsylvanian and before the 

first occurrence of Globivalvulina (Brenckle and others, 

1982). At the study section (fig. 8), however, B. rugosa 

extends at least 25 m above the first appearance of D. noduliferus and 38 m above the first Globivalvulina (PL. 

Brenckle, written commun., 1991).

It is obvious that taxonomic interpretations, biostratigraphic models, and paleobiogeography, as well as spacing 

and selection of foraminifer and conodont samples, control 

boundary placements. As taxonomic interpretations stabilize and global biostratigraphic data increase for both foraminifers and conodonts, correlations should improve the 

usefulness these groups separately and in concert.

MORROWAN-ATOKAN BOUNDARY

The foraminiferan zonation of Mamet and Skipp 

(1970) has been used extensively to correlate the Lisburne 

Group and to approximate the position of the standard 

North American Midcontinent series boundaries within it. 

Armstrong and Mamet (1977, p. 18) place the base of the 

Atokan Series at the boundary between foraminiferan 

Zones 20 and 21. They define the base of Zone 21 as the 

"outburst of abundant Eoschubertella, Pseudostaffella, and 

Globivalvulina of the group G. bulloides.'" Groves (1986) 

also uses Eoschubertella and (or) Pseudostaffella to define 

the base of the Atokan in the southern Midcontinent and 

Cordillera of the conterminous United States and to approximate this boundary in northeast Alaska. Sutherland and 

Manger (1984b) recommended that the base of the Atokan 

Series in the southern Midcontinent be marked by the 

appearance of the foraminifer Eoschubertella spp. and the 

conodont Diplognathodus spp.

Diplognathodusl was found in only one sample in our 

section (pi. 5, figs. 18, 19; pi. 6; table 1) and is rare in the 

Lisburne Group in northern Alaska. Moreover, the proposal 

to use Diplognathodus as a guide to the base of the Atokan 

preceded the recognition of Morrowan diplognathodids 

(von Bitter and Merrill, 1990). For now, Diplognathodusl 

orphanus appears to be the only known diplognathodid 

restricted to the Atokan. Consequently, other conodonts or 

groups are needed to identify rocks of Atokan age. Grayson 

(1990) and Whiteside and Grayson (1990), in their revision 

of Idiognathodus sinuosus, I. klapperi, and /. incurvus, suggest that the appearance of /. incurvus indicates an Atokan 

or slightly younger Pennsylvanian age in the southern Midcontinent, including the type area of the Atokan. Additionally, /. incurvus probably overlaps the upper range of its 

ancestor /. klapperi within the lower Atokan (Grayson and 

others, 1989). We were unable to confirm the phylogeny
CONODONT BIOFACIES 21

proposed by Grayson and his co-workers. Nearly all of the 

idiognathodids recovered from our section are either too 

poorly preserved for specific identification or are representatives of the long-ranging species, /. sinuosus. Two specimens of /. incurvus? were identified. The first appearance 

of /. sinuosus in the study section is probably unrelated to 

its origin and could represent any level within the lower part 

of its stratigraphic range. The occurrence of /. incurvus? 

with Rhachistognathus minutus subspp. suggests an age no 

younger than early Atokan for the uppermost part of the 

Wahoo Limestone in the study section.

Foraminiferan data suggest that the first appearance of 

Idiognathodus sinuosus in the study section is within the 

Atokan (figs. 7, 8). The foraminiferan guides to the Atokan, 

Pseudostaffella and Eoschubertella, first appear 16 m and 

12m, respectively, below /. sinuosus (171 and 175 m above 

the base of the Wahoo Limestone, P.L. Brenckle, written 

commun., 1991). Furthermore, Plectostaffella, the ancestor 

of Pseudostaffella, first appears 14 m below its descendant 

(157 m above the base of the Wahoo Limestone) and continues to 183 m above the base of the Wahoo Limestone. Plectostaffella is unknown in North America except from 

northern Alaska (Groves, 1986, 1988). The sudden appearance of its descendant, Pseudostaffella, at the base of the 

Atokan in the North American Midcontinent indicates its 

migration from the Eurasian-Arctic Faunal Realm to the 

Midcontinent-Andean Faunal Realm (Groves, 1988). Thus, 

Pseudostaffella probably is not a reliable guide to the base 

of the Atokan in northern Alaska. The base of the Atokan 

could lie at some level between the first appearance of 

Pseudostaffella and /. incurvus!. Figures 7 and 8 show the 

relative position of the lower boundary of the Atokan on the 

basis of conodonts versus foraminifers. A third fossil group 

may be needed to distinguish evolutionary from migratory 

patterns in foraminifers and conodonts.

CONODONT BIOFACIES

The distribution of conodonts was chiefly controlled 

by the physical and chemical characteristics of the water 

mass and its trophic resources and, on a grander scale, by 

paleogeography. These factors influence biostratigraphic 

analyses because most zonation is based on first appearances. Thus, the presence or absence of a species is not only 

related to evolution but also to a wide range of paleogeographic, paleoenvironmental, and postmortem factors (Merrill and von Bitter, 1976; Rexroad and Horowitz, 1990; 

Pohler and Barnes, 1990).

Studies that are useful for conodont biofacies analysis 

of the Wahoo Limestone include Webster (1969), Merrill 

(1973a), Merrill and Martin (1976), Merrill and von Bitter 

(1976, 1979, 1984), Driese and others (1984), Davis and 

Webster (1985), Wilson (1985), Sweet (1988), Rexroad and 

Horowitz (1990), and Morrow and Webster (1991, 1992).

Of these, Davis and Webster (1985) and Morrow and Webster (1991, 1992) best approximate the age, paleoenvironmental conditions, and species associations found in the 

Wahoo Limestone. Davis and Webster (1985) proposed four 

conodont biofacies for middle Carboniferous, shallowwater, carbonate-shelf deposits in central Montana: 

Declinognathodus-Idiognathoides, Rhachistognathus, 

Adetognathus, and Neognathodus biofacies. Morrow and 

Webster (1991) recognized only the Rhachistognathus and 

Adetognathus biofacies in offshore barrier-shoal and 

nearshore-lagoon environments through the midCarboniferous boundary interval in the Ely Limestone of 

west-central Utah. All but the Neognathodus biofacies have 

been recognized, with some modifications, in the Wahoo 

Limestone. According to Davis and Webster (1985), the 

Declinognathodus-Idiognathoides biofacies (= 

Idiognathodus-Streptognathodus biofacies of Merrill, 

1973a, and Merrill and von Bitter, 1976, 1979) represents 

an offshore, shallow, open-marine environment. The Rhachistognathus biofacies represents a higher energy regime 

that is associated with shoals transitional between the openplatform and open-marine environments (see fig. 10C). The 

Adetognathus biofacies (= Cavusgnathus biofacies of Merrill and von Bitter, 1976, 1979) occupies the open- to 

restricted-platform area behind a shoal, an area of variable 

salinities represented by a variety of lithologies.

Like Morrow and Webster (1991, 1992), we relied on 

regional stratigraphic relationships, field observations, such 

as stratigraphic sequence and bedding characteristics, and, 

most heavily, on microlithofacies to confirm and constrain 

conodont paleoenvironmental interpretations.

CONODONT BIOFACIES AND ASSOCIATED

MICROLITHOFACIES, WAHOO LIMESTONE,

EASTERN SADLEROCHIT MOUNTAINS

Conodont biofacies and depositional environments of 

the Wahoo Limestone in the eastern Sadlerochit Mountains 

are intermediate between those presented by Davis and 

Webster (1985) and Morrow and Webster (1991, 1992) for 

sections in Montana and Utah. Rhachistognathus and 

Adetognathus, however, are distributed across a wider range 

of depositional environments in the Wahoo Limestone. This 

probably resulted from hydraulic mixing of conodont elements from adjacent environments during periodic highenergy conditions on the Wahoo carbonate platform. The 

predominance of grainstone (65 percent, including oolitic 

grainstone) in the Wahoo indicates deposition on the shallow inner part of a carbonate ramp. Lacking reefal barriers, 

carbonate ramps are particularly susceptible to reworking 

and redistribution of sediment by waves and storm surges 

(Oslenger, 1991). Conodont elements in our section are 

commonly abraded, further evidence of hydraulic transport.
22 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

Our data are from 72 samples. Initially, samples were 

collected at about 5-m intervals. Subsequently, intervals 

containing important biostratigraphic boundaries and (or) 

few conodonts were resampled at closer spacing. Because 

the main focus of this study was biostratigraphic, some 

lithologies, representing environments unfavorable for conodonts, were avoided. For example, rocks representing 

restricted-marine and oolitic and oncolitic shoal environments were not sampled initially. After preliminary biostratigraphic analysis, however, even rocks known or 

inferred to be unfavorable for conodont recovery were collected near lithostratigraphic and biostratigraphic boundaries. None of these samples were devoid of conodonts, but 

predictably, they produced few if any biostratigraphically 

significant species and, even worse, too few for biofacies 

analysis (for example, tables 1 and 2; 62-80.8 m and 167- 

182 m above the base of the Wahoo Limestone). Consequently, 26 samples could not be used for biofacies analysis. 

Ten of these contain common to abundant peloids and (or) 

spicules, and another 12 contain common to abundant 

ooids, superficial ooids, and (or) oncoids. Five samples that 

contain common but not abundant ooids, superficial ooids, 

and (or) oncoids did qualify for biofacies analysis. The positive aspect of these largely negative results is that most of 

our prejudices about "offensive" rock types were reinforced, but, in a few cases, we learned not to suggest depositional environments using minimal conodont data (see 

table 2, samples not qualifying for biofacies analysis).

Only generically identifiable conodonts, including all 

apparatus elements, were used for biofacies analysis. Samples with fewer than 20 elements identifiable to genus and 

genera represented by less than 5 elements were not used 

for analysis. Cavusgnathusl tytthus, listed separately on 

table 2, is combined with cavusgnathids in Mississippian 

collections and adetognathids in Pennsylvanian collections. 

Following Ziegler and Sandberg (1990), conodont biofacies 

are designated using the name of one or two generic components that make up about 70 percent of the fauna. If the two 

most abundant genera do not reach this percentage, the conodont association is, with some exceptions, considered the 

result of postmortem hydraulic transport, bioturbation, and 

(or) unfortunate sampling. Although most of the samples 

analyzed show evidence of some hydraulic transport and 

mixing, those dominated by one or two genera are interpreted to represent a living association or an association 

derived from laterally adjacent environments.

For the most part, biofacies are closely related to specific paleoenvironments. In some instances, however, the 

associated biota and (or) degree of abrasion of conodonts 

and grain types influenced environmental interpretations 

(table 2). Biofacies and microlimofacies environmental 

analyses agree in general but may differ in some details.

Paleoenvironments (fig. 9) were interpreted from 

regional and local and vertical and lateral stratigraphic relationships, bedding characteristics, sedimentary structures,

carbonate lithology (megascopic and microscopic textural 

classification of Dunham, 1962), carbonate grain types, and 

fossil assemblages. The data set for this study is given in 

tables 1 and 2 and plate 6.

MISSISSIPPIAN PART OF THE WAHOO LIMESTONE

Regional relationships suggest that the Mississippian 

part of the lower member of the Wahoo Limestone was 

deposited in a predominantly open-platform to open-marine 

setting. Three major environments were sampled in this part 

of the section: (1) near-restricted open platform4 to open 

platform, (2) moderate- to high-energy (above wave base) 

open marine, and (3) low-energy (below wave base) open 

marine. The general characteristics and paleogeographic 

setting of each are given in figure 9.

CAVUSGNATHID BIOFACIES 

NEAR-RESTRICTED TO OPEN-PLATFORM ENVIRONMENTS

Six collections from the Mississippian part of the 

lower member of the Wahoo Limestone represent the cavusgnathid biofacies. The samples are from moderate- to 

well-sorted bryozoan grainstone, commonly containing 

fenestrate bryozoans and fewer pelmatozoans. Minor to rare 

grains include peloids, intraclasts, and bioclasts of algae, 

foraminifers, brachiopods, gastropods, and trilobites 

(table 2). Macrofossils, which are typically incomplete, 

occur as abraded and commonly micritized bioclasts. Beds 

are generally massive, bioturbated and, where preserved, 

parallel bedded. Grainstones are better washed and slightly 

coarser grained than those in the adjacent, lower energy 

cavusgnathid-kladognathid biofacies. A seventh collection 

qualified for biofacies analysis (table 1, USGS colln. 

31698-PC) but could not be included here because no 

microlithofacies sample was saved.

Conodonts are rare (<10/kg) to common (10-25/kg) 

and average 11/kg in this biofacies. Only 43 percent of the 

conodonts, however, are generically determinate, and ramiform elements are rarely identifiable to genus or even element type reflecting a relatively high-energy regime. Most 

smaller and lighter elements were probably carried into 

nearby lower energy regimes.

Cavusgnathus, dominantly C. unicornis, makes up 69 

to 100 percent, averaging 84 percent, of all conodonts from 

this biofacies (fig. 10A); C.I tytthus makes up less than 4 

percent of the cavusgnathids. Kladognathus and Gnathodus 

average 9 and 2 percent, respectively, and hindeodids, 

lochrieids, and rhachistognathids, together, make up less 

than 5 percent of conodonts from this biofacies. One sample

4We use near restricted to indicate proximity to restricted environments such as back shoals and tital flats (see fig. 9).
CONODONT BIOFACIES 23

TERRIGENOUS 

CLASTIC INFLUX

WAVE BASE

Intertidal

Dolomitized mudstone

containing cryptalgal laminations,

nodular evaporites(?), mudcracks,

terrigenous clastic sediment

Restricted platform

Silty dolomitized mudstone

to wackestone containing

algae, foraminifers, ostracodes,

calcispheres, peloids, spicules, and

quartz and rare ooids and superficial

ooids transported from adjacent shoals

Open platform

Packstone and grainstone

containing algae, peloids, foraminifers,

bryozoans, pelmatozoans, oncolites, and

corals; partly bioturbated. Also ooids and

calcispheres transported from adjacent

environments. Common to minor calcispheres,

spicules, and peloids suggest proximity to

restricted platform (=near restricted)

Shoal

Grainstone, partly

crossbedded, containing

ooids, abraded skeletal

grains and (or) peloids

Tidal channel

Grainstone containing a

transported mixture of

intraclasts, peloids, bioclasts,

bivalves, brachiopods,

foraminifers, ostracodes, ooids,

and superficial ooids

Open marine

Above wave base, high to moderate

energy, bioclastic to bryozoanpelmatozoan grainstone and packstone

Below wave base, low energy. 

pelmatozoan-bryozoan packstone to 

wackestone and spiculitic mudstone

Figure 9. Depositional model for and sediment characteristics of the Wahoo Limestone. Terminology modified from Scoffin (1987) and 

Wilson (1975). Carbonate platform upon which the Wahoo Limestone was deposited was probably a southward-dipping homoclinal ramp 

(for example, Read, 1982).

contains 12 percent Vogelgnathus and 11 percent Rhachistognathus (table 1, 13.2 m above the base of the Wahoo 

Limestone). The presence of rhachistognathids is compatible with the high-energy, well-sorted microlithofacies interpretation. All other collections from this biofacies are from 

moderately sorted, lower energy grainstones and lack 

rhachistognathids.

Cavusgnathus dominated this and, less commonly, 

adjacent offshore environments. Most other genera were 

minor components of the population and (or) postmortem 

additions. We have not been able to identify the ecologic 

preference of Vogelgnathus in the study section because of 

its scarcity. Elsewhere, this genus is associated with 

restricted marine environments (Purnell and von Bitter,
24 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

Cavusgnathus 

(including C. 9 tytthus Cavusgnathus? tytthus 

+ Adetognathus

Hindeodus

Rhachistognathus, Lochriea 

Vogelgnathus Idioprioniodus + 

Vogelgnathus

Adetognathus

Declinognathodus

Idiognathodus

Hindeodus 

Idiognathoides 

D/plognathodus? 

Idioprioniodus

PLATFORM X / CHANN

Relative percent 

of genus in each 

environment

/ OPEN

MARINE
CONODONT BIOFACIES 25

Figure 10. Generalized paleogeography, biofacies, and distribution of conodont genera at the study section, Wahoo 

Limestone, eastern Sadlerochit Mountains (fig. 2, loc. 1A). 

A, Mississippian part of lower member. B, Pennsylvanian part 

of lower member. High-energy oolitic shoals that 

dominate the upper member of the Wahoo had not fully developed during the earliest Pennsylvanian. Instead, lithologies and 

biofacies of this time period reflect the normal-marine, low- to 

moderate-energy conditions characteristic of an open-platform 

environment. C, upper member (Pennsylvanian). N, number of 

samples.

1992). Most of the rocks in our section that might represent 

the habitat of Vogelgnathus were either not sampled or 

formed in moderate- to high-energy regimes from which the 

small skeletal elements of Vogelgnathus were probably winnowed. Vogelgnathus is abundant in a poorly washed peloidal grainstone containing minor echinoderm debris and 

spicules.

The conodont species association and taphonomy suggest that the cavusgnathid biofacies occupied a nearrestricted to moderate-energy open-platform setting. The 

predominance of Cavusgnathus strongly favors a nearshore, 

relatively variable environment (Merrill and von Bitter, 

1976, 1979). In addition, minor kladognathids and rare 

hindeodids, gnathodids, and lochrieids support an openplatform rather than an open-marine interpretation.

The Mississippian part of the lower member of the 

Wahoo Limestone formed during the early phase of a major 

TR sequence. Initially, circulation and depositional patterns 

were not well established so that shoal facies and associated 

environmental partitioning are absent. Without intervening 

shoals, the depositional setting (open platform versus open 

marine) of fossiliferous packstones and grainstones cannot 

be reliably interpreted. Microlithofacies and conodontbased interpretations of the environmental setting for samples from the cavusgnathid biofacies differ. The overwhelming dominance of Cavusgnathus and the virtual 

absence of open-marine conodont species point to an opento near-restricted platform environment. In contrast, 

microlithofacies favor a moderate- to high-energy, openmarine or open-platform environment containing a diverse 

marine fauna. We believe that the conodonts favor the 

open-platform interpretation because of the low-diversity 

conodont fauna.

CAVUSGNATHID-KLADOGNATHID BIOFACIES 

OPEN-PLATFORM TO OPEN-MARINE ENVIRONMENT

Five samples from the lower 37 m of the Wahoo Limestone contain subequal mixtures of Cavusgnathus and Kladognathus. These samples are primarily from moderately 

sorted grainstone and poorly sorted packstone that contain

bryozoans and pelmatozoans, minor peloids, and rare intraclasts. Other bioclasts include minor algae, brachiopods, 

sponge spicules, and foraminifers and rare gastropods, calcispheres, and ostracodes (table 2). Grains are moderately 

abraded and variably micritized. The rocks are less well 

sorted and slightly finer grained than those of the cavusgnathid biofacies. Massive bedding may have resulted from 

extensive bioturbation, indicating oxygenated bottom 

waters and (or) low sedimentation rates. Bryozoans and pelmatozoans probably lived within or near this environment, 

indicating normal-marine conditions. Mud-rich laminae and 

burrow fills commonly contain peloids, spicules, and (or) 

ostracodes that indicate partial derivation from adjacent 

restricted-platform environments. The three samples in the 

lower 7 m of the Wahoo Limestone are packstone and 

grainstone-packstone interbedded with dolomitic spiculitic 

mudstone; this association of lithologies further indicates 

proximity to low-energy, intermittently-restricted platform 

environments.

Samples from the cavusgnathid-kladognathid biofacies 

contain relatively abundant conodonts (26/kg), but about 60 

percent are generically indeterminate fragments, suggesting 

considerable postmortem movement. Many elements, 

including ramiforms, are complete; thus, postmortem 

movement was probably within this and (or) from nearby 

biofacies.

Four samples from the open-platform to open-marine 

environment contain 40 to 57 percent Cavusgnathus unicornis, 21 to 40 percent Kladognathus spp., and 9 to 24 percent 

Gnathodus girtyi. Rhachistognathus, chiefly R. muricatus, 

makes up as much as 9 percent of two samples and idioprioniodids, lochrieids, and vogelgnathids together make up 

less than 5 percent (table 1). Cavusgnathus probably lived 

within this environment, but many elements may have been 

transported from the adjacent higher energy cavusgnathid 

biofacies (fig. 10/4). The ecologic preference of Cavusgnathus for nearshore, relatively variable environments 

(Merrill and von Bitter, 1976, 1979) is consistent with its 

distribution in the Wahoo Limestone. Kladognathus also 

lived in this environment, as nearly all the components of its 

apparatus are present (table 1). The percentage of Kladognathus diminishes rapidly shoreward toward the cavusgnathid biofacies (fig. 10A). Gnathodus girtyi may have 

lived in this environment in low to moderate numbers. Most 

of our specimens, however, are incomplete and poorly preserved suggesting postmortem transport from the more offshore gnathodid-hindeodid biofacies (fig. 10A). During this 

time interval, Gnathodus girtyi subspp. is the dominant gnathodid in collections from normal-marine, relatively 

shallow-water deposits in the Brooks Range and elsewhere 

in the Cordillera of the United States (unpub. USGS collections). This species had a variety of ecophenotypes 

(included here in G. g. simplex) that successfully competed 

in shallow water. Rhachistognathids, in addition to other 

genera that make up less than 5 percent of the conodonts
26 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

from this environment, are considered postmortem admixtures. Rhachistognathids were probably transported from 

nearby higher energy regimes as representatives of the 

genus generally occupy near-shoal and shoal-water 

environments.

A sample from 37 m above the base of the Wahoo 

Limestone contains conodonts of the cavusgnathidkladognathid biofacies and represents an open-marine environment. Cavusgnathus and Kladognathus are equally 

abundant (36 percent) and gnathodids make up 27 percent 

of the faunule, a higher proportion than other samples in 

this biofacies. On the basis of conodonts, we would interpret the environment as open platform or possibly open 

marine. Microlithofacies suggest an open-marine to openplatform, moderate-energy environment, but the low diversity and absence of shallow-water grain types favor the 

open-marine setting. The gnathodids and grain types 

together with slightly muddier lithologies convinced us to 

extend the cavusgnathid-kladognathid biofacies into the 

open-marine environment.

GNATHODID-HINDEODID BIOFACIES

LOW-ENERGY, OPEN-MARINE ENVIRONMENT

This biofacies is represented by a single sample (53 m 

above the base of the Wahoo Limestone) that is the youngest Mississippian collection used for analysis from the formation (table 2). It is from a poorly sorted bryozoan 

packstone containing common pelmatozoan, ramose bryozoan, and brachiopod fragments, minor quartz grains, and 

rare bioclasts of foraminifers, trilobites, and algae. Microlithofacies indicate a low-energy, open-marine environment 

(table 2 and fig. 9).

Conodonts are relatively common (15/kg); 50 percent 

are generically determinate, and many elements are complete. We believe that Gnathodus (63 percent) and Hindeodus (32 percent) were living in and probably seaward of this 

environment, as these forms are rare or absent in adjacent 

shoreward biofacies (fig. 10/4). Hindeodus minutus (Ellison), the only hindeodid recovered from the Wahoo Limestone, is a long-ranging (latest Chesterian to at least Early 

Permian), cosmopolitan species that is generally a persistent 

component in samples from most normal-marine environments. The gnathodids are represented chiefly by Gnathodus girtyi simplex and G. g. girtyi (in a ratio of 3:2); rare, 

but biostratigraphically significant G. girtyi simplex transitional to Declinognathodus noduliferus as well as G. bilineatus bilineatus also occur. The species association and the 

absence of nearshore conodont species confirm the microlithofacies interpretation of a below-wave-base, openmarine depositional setting (fig. 10/4). This sample represents maximum transgression during deposition of the 

lower member of the Wahoo Limestone.

PENNSYLVANIAN PART OF THE WAHOO LIMESTONE

The maximum transgression in the latest Mississippian, represented by open-marine deposits that formed 

below wave base (fig. 10/4), was followed by rapid shallowing in the earliest Pennsylvanian. Locally, uppermost Mississippian deposits were subaerially and (or) subaqueously 

eroded as evidenced by paleotopography beneath an exposure surface (local preburial banded caliche, Watts, 1990; 

fig. 6). Rare, redeposited latest Mississippian conodonts 

occur in basal Pennsylvanian deposits above this disconformity (table 1). Depositional patterns were more complex in 

the Pennsylvanian than in the Mississippian. The lowest 

part of the Pennsylvanian, however, is generally similar to 

the Mississippian because it lacks the ooid grainstones that 

typify the upper member of the Wahoo Limestone. Additionally, the upper member contains shorter and more 

numerous shallowing-upward cycles, as reflected in its 

characteristic ledge-and-slope topography (fig. 5).

The maximum duration of regression in the Wahoo 

Limestone is apparently not at the MississippianPennsylvanian boundary but is 14 m higher at the contact 

between the lower and upper members of the formation 

(fig. 4). Redeposited Mississippian conodonts are more 

prevalent immediately below the contact, the shallowest 

water deposits in the Wahoo Limestone occur immediately 

above the contact, and quartz increases from an average of 3 

to at least 12 percent in the lower 20 m of the upper member. All these features indicate significant regression and 

some exposure and erosion of older deposits. The duration 

of this possible disconformity is unknown; it may be as 

short as a diastem or as long as most of the Morrowan.

Six depositional environments—intertidal, restricted 

platform, open platform, shoal, tidal channel, and open 

marine—are recognized in the Pennsylvanian part of the 

Wahoo Limestone. The general characteristics and paleogeographic setting of each are given in figure 9. Rocks representing the intertidal environment were not sampled for 

conodonts.

Greatly influencing conodont biofacies in the upper 

member of the Wahoo Limestone is the ooid facies that 

makes up 20 percent of the member. This high-energy 

regime caused many conodont elements, particularly rhachistognathids, to be transported beyond their biofacies, 

substantially disrupting and even obliterating original biofacies patterns. Consequently, some samples representing the 

same environment, as interpreted from microlithofacies and 

stratigraphic relationships, produce significantly different 

relative abundance of conodont genera. Postmortem mixing 

of conodonts eradicated some biofacies and artificially created others.
CONODONT BIOFACIES 27

LOWER MEMBER OF THE WAHOO LIMESTONE

ADETOGNATHID-RELATED BIOFACIES 

NEAR-RESTRICTED TO OPEN-PLATFORM ENVIRONMENT

Two samples from the Pennsylvanian part of the lower 

member of the Wahoo Limestone represent an 

adetognathid-declinognathodid biofacies (table 2). The first 

is from 56 m above the base of the Wahoo Limestone and is 

an inter laminated peloidal packstone-wackestone and moderately sorted bryozoan-pelmatozoan grainstone; this mixture of lithologies suggests hydraulic mixing of open- and 

restricted-platform grain types. The second is from 59 m 

above the base of the Wahoo Limestone and is a moderately 

sorted bryozoan grainstone-packstone containing common 

bioclasts of brachiopods and pelmatozoans and rare algae, 

foraminifers, trilobites, and peloids. The microlithofacies 

suggest a moderate-energy, open-marine setting.

Conodonts are relatively common in the adetognathiddeclinognathodid biofacies (13/kg); 50 percent are generically indeterminate indicating considerable postmortem 

transport. Adetognathids and Cavusgnathus? tytthus, 

together, account for 35 to 58 percent of the conodonts in 

this biofacies. Adetognathids are a long-ranging (latest 

Chesterian to Early Permian), relatively shallow-water, 

eurytopic group that is a common to abundant component 

of all our Pennsylvanian faunas. The group was competitively successful in partly restricted and (or) variable environments. Cavusgnathus? tytthus is relatively abundant 

(22-35 percent) in the adetognathid-declinognathodid biofacies. It is a relatively rare, short-ranging, latest Mississippian and very earliest Pennsylvanian species in the 

northeast Brooks Range. Consequently, it is restricted to the 

lower 20.5 m of the Pennsylvanian part of our section. The 

species is known only from the northeast Brooks Range, 

western Utah, and its type area in the Illinois basin. It 

appears to extend from nearshore, possibly intermittently 

restricted environments that typify the inner margins of 

intracratonic basins to the shallower part of the openplatform environment. Its presence in open-marine environments may be chiefly a consequence of postmortem hydraulic transport (fig. 105). In the adetognathiddeclinognathodid biofacies, it occurs with Declinognathodus noduliferus japonicus. Declinognathodus noduliferus is 

a cosmopolitan species that has a variety of ecophenotypes. 

We assume that the most nodose form (D. n. japonicus) 

occupied shallower and more variable environments than 

the more delicately ornamented D. n. inaequalis. Indeed, D. 

n. japonicus makes up about 90 percent of the declinognathodids in this relatively shallow-water biofacies.

Rhachistognathids are few in the Pennsylvanian part of 

the lower member of the Wahoo Limestone because their 

principal habitat, the shoal-water environment, was rare 

(fig. 105). Rhachistognathus muricatus, virtually the only 

rhachistognathid in this part of the Wahoo Limestone,

makes up 8 to 21 percent of the conodont assemblage in the 

two samples from the adetognathid-declinognathodid biofacies. This species is morphologically variable, a characteristic of conodonts that are successful in a variety of 

shallow-water environments.

LOW-ENERGY, OPEN-MARINE ENVIRONMENT

A single sample of bryozoan packstone containing 

common pelmatozoans, minor brachiopods and bivalves, 

and rare bioclasts of foraminifers, gastropods, sponge spicules, and trilobites produced conodonts of the hindeodidadetognathid biofacies (tables 1, 2; 69 m above the base of 

the Wahoo Limestone). The microlithofacies indicates a 

low-energy open-marine environment. Although the sample 

qualifies for biofacies analysis, the species association suggests a mixed assemblage. It is likely that Hindeodus minutus occupied this environment as all elements of its 

apparatus are present. This species is long ranging and consistently appears in rocks representing the relatively deeper 

depositional settings of the Wahoo Limestone (figs. 10A, 

B). This biofacies may represent the outer limit of the 

Cavusgnathus? tytthus and adetognathid habitats. More 

likely, these forms are hydraulic admixtures. In addition, 

rhachistognathids (18 percent) were probably carried here 

from their shallow-water high-energy habitat.

UPPER MEMBER OF THE WAHOO LIMESTONE

ADETOGNATHID-RHACHISTOGNATHID BIOFACIES

RESTRICTED TO NEAR OPEN-PLATFORM ENVIRONMENT

Restricted platform conditions were prominent near 

the base and top of the upper member of the Wahoo Limestone when shoals had migrated farther south. Six samples 

from the upper member were collected from restricted- to 

near open-platform environments as determined by field 

observations and microlithofacies (table 2).

Only two samples from the least restricted part of this 

environment qualified for biofacies analysis. These produced nearly equal numbers of adetognathids and rhachistognathids. One (246 m above the base of the Wahoo 

Limestone) is a peloidal grainstone containing common 

quartz and minor bioclasts of pelmatozoans, brachiopods, 

foraminifers, sponge spicules, ostracodes, and calcispheres. 

The other, at 261.5 m, is spiculitic mudstone containing 

common peloids, oncoids, and a variety of bioclasts. Conodonts in these collections represent either the edge of the 

rhachistognathid-adetognathid biofacies or, more likely, 

storm-tossed skeletons, stranded voyagers, or fecal 

droppings.

Four samples from the restricted platform did not qualify for biofacies analysis; their microlithofacies are listed in 

table 2. The conodonts that occur in these samples were
28 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

probably derived from the adjacent open-platform environment that hosted the rhachistognathid-adetognathid biofacies (fig. 10C).

OPEN-PLATFORM TO NEAR-SHOAL OPEN-PLATFORM ENVIRONMENTS

Five samples from the adetognathid-rhachistognathid 

biofacies occur in a variety of open-platform subenvironments (table 2; 84, 118, 157, 203, 241 m above the base of 

the Wahoo Limestone). These are variously sorted grainstones and one moderately sorted grainstone-packstone. 

These rocks contain locally abundant bryozoans or pelmatozoans, as well as a variety of bioclasts such as brachiopods, gastropods, and algae. Peloids, ooids, superficial 

ooids, oncoids, and intraclasts are common in several samples and grains are commonly micritized (table 2). Donezella algae are common to minor in two samples.

Conodonts are rare (6/kg) in these samples. About 50 

percent are generically determinate, most are incomplete Pa 

elements, and some are abraded. Many, particularly the rhachistognathids, were probably transported from the adjacent, higher energy, shoal-water environment. Adetognathus 

forms 40 to 54 percent of the assemblage in open-platform 

settings and shoal aprons. It probably lived in these settings 

as its relative abundance generally decreases seaward (fig. 

10C). Although rhachistognathids make up about half the 

conodonts in open-platform to near-shoal deposits, they 

become even more abundant shoalward. We cannot distinguish postmortem admixtures from in situ specimens but 

suspect that a high percentage represent the former. Collections from this biofacies are remarkably free of other genera. This may be the natural species association or an 

artifice of winnowing and breakage. Both the microlithofacies and the low diversity of conodonts favor an openplatform to near-shoal interpretation.

TIDAL-CHANNEL(?) ENVIRONMENT

One sample of very well sorted grainstone containing 

common highly abraded bioclasts of foraminifers, bryozoans, and ostracodes and minor peloids, quartz, and other 

bioclasts including algae suggests a high-energy, openplatform to open-marine setting, possibly a tidal channel 

(table 2; 113m above the base of the Wahoo Limestone). It 

produced 66 and 31 percent rhachistognathids and adetognathids, respectively. The abundance of rhachistognathids 

suggests a high-energy regime, either a shoal or tidalchannel setting. The species association favors a tidalchannel or near-shoal open-platform environment because 

adetognathids are abundant and other conodonts are rare. In 

combination, biofacies and microlithofacies data favor a 

tidal-channel setting. This sample is plotted in the

rhachistognathid-dominated shoal or tidal channel environment on figure 10C.

RHACHISTOGNATHID BIOFACIES

Rhachistognathids are the most abundant conodonts in 

a variety of high-energy environments including shoal and 

shoal aprons in open-platform and open-marine settings. 

The association of rhachistognathids and lesser adetognathids suggests a near-shoal, open-platform setting, particularly if the adetognathids are relatively intact. In shoal to 

tidal-channel environments, the number of rhachistognathids is generally much greater in the adjacent shoal 

aprons (table 2). If typically open-marine forms, such as 

declinognathodids or idiognathodids, occur with abundant 

rhachistognathids and are nearly as common as adetognathids, we favor a near-shoal, open-marine setting.

NEAR-SHOAL, OPEN-PLATFORM ENVIRONMENT

Three samples (table 2; 95, 107, and 257.5 m above the 

base of the Wahoo Limestone) from the rhachistognathid 

biofacies referred to this environment contain adetognathids 

as virtually the only other conodonts. Poorly to well-sorted 

grainstone-packstone to grainstone contain a variety of 

common to minor bioclasts (bryozoans, pelmatozoans, foraminifers, oncoids, and algae) and ooids, superficial ooids, 

peloids, and intraclasts. Conodonts are relatively common 

(12/kg); 73 percent are identifiable to genus. The abundant 

rhachistognathids (71-80 percent) indicate a relatively 

high-energy shoal to near-shoal environment. The virtual 

absence of conodonts other than adetognathids (20-29 percent) favors a back-shoal setting. Environmental interpretations, based on microlithofacies, generally match the 

conodont-based interpretations. These three samples are 

plotted with the adetognathid-rhachistognathid openplatform to near-shoal biofacies on figure 10C.

SHOAL OR TIDAL-CHANNEL ENVIRONMENTS

High-energy shoal or tidal-channel environments 

include oolitic-rich and skeletal-rich grainstones. Although 

no tidal channels were distinguished in the field, some conodont and microlithofacies samples produce a well-sorted 

mixture of grains derived from open-platform, openmarine, and shoal environments that are compatible with a 

tidal-channel setting.

Five samples qualifying for biofacies analysis are from 

massive-bedded, very well to well-sorted grainstone containing mixtures of common to minor bioclasts (foraminifers, bryozoans, pelmatozoans, algae, brachiopods, and 

bivalves), ooids, superficial ooids, peloids, intraclasts, and
CONODONT BIOFACIES 29

quartz (table 2). Conodonts are common (21/kg) and 

remarkably well preserved; 67 percent are generically 

determinate suggesting the conodonts lived in and (or) adjacent to shoal and tidal-channel environments.

Rhachistognathids overwhelmingly dominate the shoal 

and tidal-channel environments, making up 73 to 90 percent 

of the collections. In the upper member of the Wahoo Limestone, this group is probably as diverse as in any other succession thus far described (for example, Baesemann and 

Lane, 1985). Specimens are abundant and extremely robust. 

If Rhachistognathus tninutus had been first described from 

the Wahoo, its trivial name would have been gigantus. The 

rhachistognathids include, in order of decreasing abundance, R. muricatus, R. minutus subspp., and R. websteri. 

The two lowest samples are dominated by R. muricatus, the 

next higher two by R. websteri, and the stratigraphically 

highest by R. minutus subspp. Species of Rhachistognathus 

probably occupied different areas of the shoal and tidalchannel environments. The replacement of R. muricatus by 

R. websteri and subsequent replacement of R. websteri by 

R. minutus subspp. generally parallel a major transgression 

and the concomitant expansion of shoal facies in the upper 

member of the Wahoo Limestone. The same species succession is found at similar stratigraphic levels in the near-shoal 

open-platform environment (see tables 1 and 2). Morphologically, R. muricatus and R. websteri are more variable 

than R. minutus subspp., likely reflecting their adaptation to 

variable environments. Rhachistognathus minutus subspp. 

first appears in the study section 14 m above the base of the 

upper member and eventually replaces other rhachistognathids as the dominant species in environments favorable 

for the genus. The more uniform and symmetrical morphology of R. minutus subspp. suggests its adaptation to more 

uniform, normal-marine environments. Indeed, R. minutus 

subspp. is the dominant rhachistognathid in seaward 

settings.

Adetognathids, the only other group common to the 

shoal and tidal-channel environments, make up 10 to 27 

percent of the collections. Their relative abundance does not 

appear to correlate well with any particular species of Rhachistognathus. The adetognathids are probably migrants 

and (or) hydraulic admixtures from the open platform. Virtually no other conodonts occur in this biofacies in these 

environments (table 1).

NEAR-SHOAL, OPEN-MARINE ENVIRONMENT

Three samples from the rhachistognathid biofacies are 

attributed to this environment (table 2). One sample (133.5 

m above the base of the Wahoo Limestone) is from moderately sorted, bryozoan grainstone containing common pelmatozoans and a variety of minor bioclasts, peloids, 

intraclasts, and quartz. Conodonts are abundant (34/kg); 

62 percent are generically determinate. They include

rhachistognathids (77 percent), adetognathids (14 percent), 

and declinognathodids (9 percent). The rhachistognathids 

indicate proximity to a high-energy environment, and the 

declinognathodids suggest a position seaward of a shoal or 

tidal channel. Microlithofacies also suggest a near-shoal, 

open-marine setting, but of moderate energy (table 2). An 

open-marine shoal apron seems appropriate for a faunule 

dominated by cosmopolitan Rhachistognathus minutus subspp. The second sample (at 232 m) is a well-sorted bryozoan grainstone containing common pelmatozoans and 

minor bioclasts of gastropods, oncoids, foraminifers, algae, 

bivalves, and brachiopods. Conodonts are relatively common (11/kg), and 43 percent are determinable to genus. 

These include rhachistognathids (54 percent), idiognathodids (23 percent), adetognathids (12 percent), and declinognathodids (10 percent). For convenience, this sample is 

included in the rhachistognathid biofacies even though rhachistognathids make up less than 70 percent of the faunule. 

Rhachistognathids indicate proximity to a high-energy environment. The declinognathodids and idiognathodids suggest open-marine conditions, and the adetognathids, in 

particular A. spathus, may indicate proximity to an openplatform high-energy regime. Taken together, this mix 

favors a near-shoal, open-marine setting, assuming some of 

the adetognathids are postmortem admixtures. Alternatively, declinognathodids may have been carried over the 

shoals and into the open platform. Microlithofacies support 

either interpretation. In the overall TR sequence of the 

upper member of the Wahoo Limestone, both samples occur 

at the transition from open-platform to shoal conditions, 

thus possibly favoring an open-platform interpretation. The 

high percentage of declinognathodids and idiognathodids 

influenced the choice of an open-marine near-shoal depositional environment.

A third collection, (187 m above the base of the Wahoo 

Limestone) contains the greatest number of Rhachistognathus minutus declinatus in our sample set and is questionably included in this environment. It is the most productive sample (5 I/kg) and yields 62 percent generically 

determinate conodonts. No other rhachistognathids occur in 

this sample; other conodonts include 10 percent declinognathodids and 3 percent each of idiognathodids and adetognathids. The association suggests an open-marine shoalapron to near-shoal environment. The collection is from a 

moderately sorted bryozoan grainstone interbedded with 

fine-grained foraminiferan packstone that could have 

formed in open-platform and (or) open-marine environments. Perhaps R. m. declinatus occupied the open-marine 

shoal apron. The unusual species association may have 

resulted from sampling two lithologies with bryozoan 

grainstone producing rhachistognathids and adetognathids 

and the deeper(?) water foraminiferan packstone supplying 

idiognathodids and declinognathodids.
30 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

DECLINOGNATHODID-RELATED BIOFACIES

NEAR-SHOAL, OPEN-MARINE ENVIRONMENT

Two samples of moderately sorted bryozoan grainstone to packstone containing common pelmatozoans and 

minor brachiopod bioclasts and ooids produced a declinognathodid and declinognathodid-idiognathodid biofacies 

(table 2; 197.5 and 207 m above the base of the Wahoo 

Limestone). Conodonts are rare (6/kg); only 28 percent are 

generically determinate suggesting an abundant influx of 

fragments from high-energy environments. Declinognathodus noduliferus, chiefly D. n. noduliferus, is most abundant 

(62 percent), followed by idiognathodids (21 percent) and 

Rhachistognathus minutus declinatus (9 percent). The species association and microlithofacies suggest an openmarine, near-shoal depositional environment. Both samples 

are from strata that represent the maximum transgression 

during deposition of the upper part of the Wahoo 

Limestone.

One sample (table 2; 177 m above the base of the 

Wahoo Limestone) representing a declinognathodidrhachistognathid biofacies is from a poorly sorted grainstone that contains a variety of bioclasts (for example, 

algae, foraminifers, bryozoans, and oncoids) and peloids, 

ooids, superficial ooids, and intraclasts. Conodonts are rare 

(7/kg); 50 percent are generically determinate. Subequal 

numbers of Declinognathodus noduliferus noduliferus and 

Rhachistognathus minutus (chiefly R. m. declinatus} suggest a near-shoal, open-marine setting. The bioclasts and 

lithoclasts are a mix of open-platform (particularly several 

types of algae), shoal, and open-marine forms that might 

represent a tidal-channel in proximity to ooid shoals. The 

concdonts do not argue against this interpretation. This 

sample has been included in the shoal to tidal-channel environment on figure 10C.

LOW-ENERGY. OPEN-PLATFORM AND (OR) 

OPEN-MARINE ENVIRONMENT

Seven samples produced declinognathodids with and 

without other associated open-marine and shallow-water 

genera (table 2). Three samples (table 2; 152, 178, and 250 

m above the base of the Wahoo Limestone) indicate that the 

low-energy, open-marine environment supported only low 

numbers of declinognathodids (3/kg). The samples, from 

lowest to highest, are lime mudstone, poorly sorted packstone containing common bioclasts of bryozoans and pelmatozoans, and a dolomitized mudstone to wackestone. 

Microlithofacies and conodont biofacies both indicate an 

open-marine depositional environment.

Only two samples from the declinognathodid-related 

biofacies produced Declinognathodus noduliferus subspp. 

together with Idiognathodus sinuosus (table 2; 217.5 and 

237 m above the base of the Wahoo Limestone). Both are

poorly sorted packstone containing common bioclasts of 

bryozoans, pelmatozoans, and brachiopods and minor 

algae. Conodonts are rare to common (8-17/kg), and only 

40 percent are generically determinate. The conodont species associations indicate a low-energy, open-marine environment; microlithofacies indicate the same environment 

for one sample (at 217.5 m) and an open-platform to openmarine environment for the other sample.

Microlithofacies and conodont biofacies of the final 

two samples indicate a low-energy, open-platform or 

open-marine depositional environment (table 2; 142 and 

162 m above the base of the Wahoo Limestone). These are 

included in the low-energy open-marine environment on 

figure 10C. The lower sample is dolomitized packstone that 

contains common bryozoans and minor quartz and bioclasts 

of brachiopods and pelmatozoans. These constituents indicate a low-energy open-platform or open-marine environment. The conodont biofacies is equally ambiguous. 

Rhachistognathids (47 percent) suggest a relatively highenergy near-shoal or shoal setting; adetognathids (31 percent) suggest proximity to a back-shoal area, but declinognathodids (22 percent) favor a more open-marine setting. 

The sample could represent postmortem seaward transport 

of adetognathids and probably rhachistognathids into an 

open-marine habitat that contained low numbers of declinognathodids. Alternatively, the declinognathodids could 

have been transported to the open platform. The higher 

sample is a dolomitized packstone-wackestone containing 

some grains possibly derived from the open platform 

(minor peloids and quartz and rare ooids, spicules, and 

ostracodes). The conodonts are a mix of platform, shoal, 

and open-marine forms (29 percent adetognathids, 40 percent rhachistognathids, and 27 percent declinognathodids).

BIOFACIES SUMMARY

The Wahoo Limestone formed in chiefly openplatform, near-shoal, and open-marine environments on the 

shallow, inner part of a high-energy carbonate ramp. In the 

uppermost Mississippian and lowermost Pennsylvanian part 

of the Wahoo Limestone, shoal facies were uncommon so 

that open-platform and open-marine microlithofacies and 

conodont biofacies were not clearly separated. Grain types 

and, to a lesser extent, conodonts were hydraulically spread 

beyond their original settings making some environmental 

interpretations equivocal. The use of conodont biofacies 

and microfacies in concert clarifies some of these environmental ambiguities. In the upper member of the Wahoo 

Limestone, extensive ooid and skeletal shoal tracts separated open-marine and open-platform environments producing more distinct biofacies and diagnostic microlithofacies. 

Rhachistognathids thrived in and adjacent to the shoal 

facies. After death, many of their skeletal elements 

remained in place, however, a substantial number were
CONODONT PRESERVATION AND CAI VALUES 31

washed into surrounding environments, masking original 

species associations (see table 2). Similarly, mixing of carbonate grains obscures microlithofacies interpretations. The 

vertical succession of conodont biofacies substantiates our 

microlithofacies interpretations that indicate the upper part 

of the Wahoo Limestone formed in a TR sequence passing 

from restricted platform to shoals and, finally, back to 

restricted platform. Additional studies are needed to further 

integrate conodont biofacies and microlithofacies analyses.

CONODONT PRESERVATION 

AND CAI VALUES

Epstein and others (1977) and Rejebian and others 

(1987) demonstrated in controlled laboratory experiments 

that color alteration in conodonts is time and temperature 

dependent. These color changes were assigned color alteration indices (CAI) from 1 to 8. Conodonts visibly change 

from pale yellow to brown and black (CAIs 1 to 5) from 50° 

to 300°C as a result of carbonization of the trace amounts of 

organic matter sealed within a conodont element. Conodonts change from black to gray, opaque white, and finally 

crystal clear (CAIs 5 to 8) from 300° to >600°C as a result 

of loss of carbon and water of crystallization and 

recrystallization.

Conodonts altered during burial metamorphism have 

consistent CAI values, locally and regionally, that reflect 

depth and duration of burial; textural alteration related to 

burial thermal regimes does not generally begin until a CAI 

of 4.5 or greater. In contrast, conodonts recovered from 

contact-metamorphosed or hydro thermally altered rocks 

have a range of CAI values locally within an area and even 

within a single sample; these can be texturally unaltered to 

corroded and may be fractured or deformed. If a range of 

CAI values occurs in a small area, the minimum value is 

used to estimate the regional background (burial metamorphic) temperature (Rejebian and others, 1987). Significantly, CAI values of 6 and 7 can also be produced by 

relatively low-temperature saline solutions. These solutions 

corrode conodonts and oxidize their organic matter thereby 

producing CAI values of 6 and 7 that are unrelated to the 

thermal regimes that can also produce these values during 

burial and contact metamorphism (Rejebian and others, 

1987; Harris and others, 1990). Characteristically, conodonts from hydrothermally altered rocks tend to have low 

to medium CAI values mixed with values of 6 and 7; CAI 

values of 5, 5.5, and 8 are generally absent.

CAI values in Ordovician through Permian rocks in 

the Sadlerochit Mountains range chiefly from 3 to 4 (Johnsson and others, 1992) suggesting that regional burial temperatures reached at least 150° to 200°C. None of the 

samples reported by them have CAI values greater than 4.5. 

Nine samples from a 102-m-thick section in the upper part 

of the Wahoo Limestone at Katakturuk River gorge (fig. 2,

loc. 2), about 40 km west of the study section, produced 

conodonts having consistent CAI values of 3 to 3.5 (app. 1, 

Iocs. 2a-j).

In the study section, 71 of 73 samples could be analyzed for CAI; two samples contain conodonts that were too 

few and (or) small for CAI analysis (table 1). CAI values of 

3 to 4.5 and 6 were determined; no CAI values of 5 were 

observed. Most samples (96 percent) contain conodonts of 

CAI 4, but half of these have a mixture of CAI values 

(chiefly 4 and 6, rarely 3, and very rarely 3.5 and 4.5). In 

addition, most conodonts have a sugary and (or) corroded 

texture (many are coated with dolomite crystals; pi. 5, figs. 

18, 19). The range of CAI values and textures suggest 

hydrothermal alteration of the Wahoo Limestone. A section 

1 km west of the study section (fig. 2, loc. IBlb-e), produced CAIs of 4 and 6 in four samples taken immediately 

above the Mississippian-Pennsylvanian boundary.

What caused the anomalously "high" CAI 6 values in 

the study area? Nearly 50 percent of the samples produced 

some conodonts having a CAI of 6. About 60 percent of the 

anomalous samples are from grainstone or packstonegrainstone and another 30 percent are from a variety of 

dolomitized carbonate rocks. These data suggest positive 

correlation between anomalous CAI and rock porosity and 

permeability. However, not all grainstones or dolomitized 

carbonate rocks produced conodonts having anomalous 

CAIs. Some of the variability in CAI values could be 

related to occlusion of porosity and permeability by 

cements that formed prior to deposition of the Permian 

Echooka Formation (Watts, 1991). To date, the carbonatecement stratigraphy of the study section has not been analyzed. Carlson (1990) and Watts (1991), however, partly 

analyzed the carbonate-cement stratigraphy of a section 3 

km to the southwest (fig. 2, loc. 1C) and found that most of 

the cements in the Wahoo Limestone formed prior to deposition of the Echooka Formation. But, post-Permian 

cements do form 20 to 80 percent of the cement in the lowermost 35 m of the Wahoo Limestone. Some of this porosity 

may have still been open for fluid migration during orogenesis. The anomalous CAI values, at least in the lower member at the study section, may have formed prior to or 

concurrently with these late-stage cements, but other intervals of anomalous CAIs may be related to still other factors. 

For example, fracture porosity (related to Late Cretaceous 

to Holocene regional orogenesis; Wallace and Hanks, 1990) 

undoubtedly influenced hydrothermal circulation patterns.

Two intervals in our section lack conodonts having 

anomalous CAIs: (1) an interval from 69 to 97 m above the 

base of the Wahoo Limestone that approximates the quartzrich lower part of the upper member of the formation and 

(2) a 10-m-thick interval at the top of the upper member 

containing a higher than average percentage of undolomitized spiculitic mudstone and wackestone. These data 

suggest a negative correlation between anomalously high 

CAI values and mixed mineralogy or poorly washed
32 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

deposits; such rock types tend to have low porosity and permeability. Much of the above data suggest that the anomalous CAT values of 6 were produced by hydrothermal 

solutions (probably low-temperature saline solutions) moving through relatively permeable channelways and possibly 

elevating CAIs no more than one index value (from 3 to 3.5 

or 4), as well as corroding and bleaching some specimens to 

produce CAIs of 6. Additional samples from the uppermost 

part of the Alapah Limestone at the study section are 

severely bleached and corroded and approximate a CAT of 

7, suggesting increased alteration at this level. Watts (1990) 

also noted that porous dolostones and spar-filled caverns in 

the upper part of the Alapah Limestone probably acted as 

channelways for hydrothermal fluids. The hydrothermal 

alteration occurred after the early Atokan, most likely after 

the Permian. It is probably related to Brookian orogenesis 

and occurred after maximum burial metamorphism that elevated CAT values to 3 or 3.5 in Carboniferous and Permian 

rocks.

SYSTEMATIC PALEONTOLOGY

We have used the element notation summarized by 

Sweet (1988, fig. 2.10). Most of the generically and specifically determinate specimens in our collections are Pa elements. Wherever possible we have tried to identify other 

elements of apparatuses, particularly for hindeodids, idioprioniodids, and kladognathids (table 1). Genera are listed 

alphabetically. Many specimens are easily assignable to a 

genus but are not well enough preserved for specific determination. Most conodonts in the collections have undergone extensive postmortem transport and are thus 

incomplete and abraded; moreover, some are diagenetically 

and hydrothermally altered.

All specimens shown on plates 1-5 are reposited in the 

U.S. National Museum (USNM), Washington, D.C. All 

other specimens are in the collections of the conodont laboratory of the U.S. Geological Survey, Reston, Va., and are 

cataloged by USGS collection number. Table 1 and plate 6 

show the distribution and abundance of conodont elements, 

and figure 10 and table 2 show their inferred paleoenvironmental distribution.

Genus ADETOGNATHUS Lane, 1967

Type species.—Cavusgnathus lautus Gunnell, 1933

p. 286, pi. 31, figs. 67,68 

Adetognathus lautus (Gunnell, 1933)

Plate 1, figures 13-15,21-24

For synonymy to 1971, see Lane and Straka (1974, p. 64). 

1971 Adetognathus gigantus (Gunnell). Lane and others,

pi. l.fig. 6. 

1971 Adetognathus lautus (Gunnell). Lane and others, pi.

I,fig5.

1971 Cavusgnathus gigantus Gunnell. Merrill and King, 

p. 654-655, pi. 75, figs. 9-22 (only).

1971 Cavusgnathus lautus Gunnell. Merrill and King, p. 

655, pi. 75, figs. 23, 24, 26-29 (only).

1972 Cavusgnathus lautus Gunnell. von Bitter, p. 61-63, 

pi. 4, figs. 3a-h; pi. 5, figs. la-h.

1973 Adetognathus gigantus (Gunnell). Baesemann, p. 

696-697, pi. 2, figs. 237-28?, 32?, 33?, 35, 36, 37?, 

38^1.

1973 Adetognathus lautus (Gunnell). Baesemann, p. 697, 

pi. 2, figs. 29-31,34.

1974 Adetognathus lautus (Gunnell). Lane and Straka, 

p. 64-65, figs. 36: 17, 21, 22, 25-31; figs. 38: 1-4, 

6-8, 10-15, 20; figs. 39: 14, 15, 19, 20; figs. 40: 1- 

3, 7-14?.

1974 Cavusgnathus lautus Gunnell. Merrill, pi. 1, figs. 8, 

9.

1974 Adetognathus gigantus (Gunnell). Toomey and others, pi. 3, fig. 15.

1974 Adetognathus lautus (Gunnell). Toomey and others, 

pi. 3, fig. 14.

1975 Adetognathus gigantus (Gunnell). Perlmutter, 

p. 101, pi. 3, figs. 32, 33, 40, 41, 46, 47.

1975 Adetognathus lautus (Gunnell). Perlmutter, p. 101, 

pi. 3, figs. 34-39, 42^5.

1975 Cavusgnathus lautus Gunnell. Merrill, p. 44^6, 

figs. 14: 8?, 9, (not figs. 14: 1, 2); figs. 15: 1, 2, 13- 

16; figs. 16: 3, 4, 36, 37; (not figs. 17: 1, 2).

1979 Cavusgnathus lautus Gunnell. Einor and others, 

pi. 14, figs. 13a-c.

1979 Adetognathus gigantus (Gunnell). Semichatova and 

others, pi. 22, fig. 16.

1980 Adetognathus lautus (Gunnell). Bender, p. 8, 9,

pi. 4, figs. 26-33. 

1980 Cavusgnathus lautus Gunnell. Merrill and Powell,

pi. 1, figs. 30-33. 

1980 Adetognathus lautus (Gunnell). Tynan, p. 1298,

1299, pi. 2, figs. 12, 13, 20, 21 (not fig. 22). 

1984 Adetognathus spp. Driese and others, pi. 1, figs. 1-

3.

1984 Adetognathus lautus (Gunnell). Grayson, pi. 3,

figs. 8, 9, 26, 27. 

1985b Adetognathus lautus (Gunnell). Grayson and others,

p. 124, pi. l,figs. 22, 29. 

1985a Adetognathus lautus (Gunnell). Lane and others,

figs. 6D, E.

1985 Adetognathus lautus (Gunnell). Rexroad and

Merrill, p. 45, 46, pi. 2, figs. 5, 6?, 28-39; pi. 3,

figs. 26-28; pi. 4, figs. 22-25. 

1985 Adetognathus gigantus (Gunnell). Skipp and others,

pi. 8, fig. 7. 

1985 Adetognathus lautus (Gunnell). Skipp and others,

pi. 8, fig. 6.
SYSTEMATIC PALEONTOLOGY 33

1985 Adetognathus lautus (Gunnell). Wardlaw, p. 400,

pi. 3, fig. 7. 

1985 Adetognathus spathus (Dunn). Wardlaw, p. 400,

pi. 2, figs. 7, 8. 

1989 Cavusgnathus lautus Gunnell. Merrill and Grayson,

pi. 1, figs. 31, 32, 33?, 34?; pi. 2, figs. 20-23, 24?,

257-29?. 

1991 Adetognathus lautus (Gunnell). Brown and others,

figs. 7:8-11. 

1991 Adetognathus lautus (Gunnell). Morrow and

Webster, pi. 1, figs. 4-11.

1991 Adetognathus lautus (Gunnell). Nemirovskaya and 

others, pi. 3, figs. 20-24.

1992 Adetognathus lautus (Gunnell). Morrow and

Webster, pi. 1, fig. 12.

1992 Adetognathus lautus (Gunnell) morphotype A. 

Weibel and Norby, p. 44, 45, text-fig. 5, pi. 2, 

figs. 1-35.

1992 Cavusgnathus lautus Gunnell. Sutherland and Grayson, pi. 2, fig. 2.

Remarks.—Rexroad and Merrill (1985) suggest that A. 

spathus may be a recurrent ecophenotype of A. lautus. We 

retain A. spathus, however, as a separate taxon to test this 

concept; see remarks under A. spathus.

A few sinistral specimens (pi. 1, figs. 13-15) have a 

short right-trending carinal extension of the blade.

The first appearance of Adetognathus lautus below 

Declinognathodus noduliferus defines the Upper muricatus 

Subzone of the latest Chesterian. Adetognathus lautus 

occurs in two collections from 72 and 65 m below the top of 

the Alapah Limestone (app. 1, Iocs. lAla, b) but is represented by only one specimen in the Mississippian part of the 

overlying Wahoo Limestone. This specimen is from a sample taken 53.4 m above the base of the Wahoo Limestone 

(app. 1, loc. lAlc), about 50 m along strike from USGS 

colln. 30757-PC in the study section (table 1). Adetognathus lautus does not reappear in our collections from the 

study section until 84 m above the base of the Wahoo 

Limestone.

Distribution in the study section.—84 to 260.5 m 

above the base of the Wahoo Limestone (Morrowan to 

lower Atokan; lower minutus Fauna to Idiognathodus 

Fauna).

Known stratigraphic range.—uppermost Chesterian 

(base of Upper muricatus Subzone) to Lower Permian.

Material.—306 Pa elements.

Adetognathus spathus (Dunn, 1966)

Plate 1, figures 16-20, 25, 26

1966 Cavusgnathus spatha Dunn, p. 1297, 1299, pi. 157, 

figs. 3, 7, 8.

1967 Adetognathus lauta (Gunnell). Lane, pi. 121, figs. 4, 

5, 18.

1969 Cavusgnathus spathus Dunn. Webster, p. 28, 29, 

pi. 4, figs. 1,4,5.

1970b Adetognathus spathus (Dunn). Dunn, p. 327, textfig. 10B, pi. 61, figs. 11-13.

1970 Adetognathus gigantus (Gunnell). Thompson, 

pi. 139, fig. 26.

1971 Adetognathus spathus (Dunn). Lane and others,

pi. 1, fig. 25. 

1971 Cavusgnathus gigantus Gunnell. Merrill and King,

p. 654, 655, pi. 75, figs. 30-32 (only). 

1971 Cavusgnathus lautus Gunnell. Merrill and King,

p. 655, pi. 75, fig. 25 (only). 

?1973 Adetognathus gigantus (Gunnell). Baesemann,

p. 696, 697, pi. 2, figs. 36, 38^1.

1974 Adetognathus spathus (Dunn). Lane and Straka, 

p. 65, 66, figs. 38: 5, 9, 16-19; figs. 40: 4-6.

1975 Cavusgnathus lautus Gunnell. Merrill, figs. 14: 1, 2

(only); figs. 17: 1?, 2?. 

1985 Adetognathus spathus (Dunn). Skipp and others,

pi. 8, figs. 1,4. 

1985 Adetognathus spathus (Dunn). Wardlaw, pi. 3,

figs. 8, 9? (only).

1991 Adetognathus spathus (Dunn). Morrow and 

Webster, pi. 1, figs. 12-16; pi. 2, figs. 1-4.

1992 Adetognathus spathus (Dunn). Morrow and 

Webster, pi. 1, fig. 13.

Remarks.—Specimens of Adetognathus spathus from 

the Wahoo Limestone may have large, exaggerated antlerlike denticles on the posterior process (pi. 1, figs. 25, 26). 

Biofacies analysis does not show significant environmental 

separation in the distribution of A. spathus and A. lautus. 

This may be a consequence of postmortem hydraulic mixing. The Pa-element morphology suggests a very shallow 

water, possibly high-energy environment (G.D. Webster, 

written commun., 1994, and unpub. U.S. Geological Survey 

collections). We agree with Rexroad and Merrill (1985) 

who believe that A. spathus may be a recurrent ecophenotype of A. lautus.

Distribution in the study section.—113 to 257.5 m 

above the base of the Wahoo Limestone (Morrowan to 

lower Atokan; lower minutus Fauna to Idiognathodus 

Fauna).

Known stratigraphic range.—uppermost Chesterian 

(base of Upper muricatus Subzone) to at least Upper Pennsylvanian. Webster (1969) reported Adetognathus spathus 

from the uppermost Rhipidomella nevadensis Zone suggesting a latest Chesterian age for the lowest part of its range.

Material—54 Pa elements.

Adetognathus spp. indet.

Remarks.—Included are chiefly broken, abraded, or 

juvenile Pa elements.

Distribution in the study section.—56 to 261.5 m 

above the base of the Wahoo Limestone (Morrowan to
34 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

lower Atokan; noduliferus-primus Zone to Idiognathodus 

Fauna).

Known stratigraphic range.—uppermost Chesterian 

(base of Upper muricatus Subzone) to Lower Permian.

Material.—211 Pa and 3 Pb elements.

Genus CAVUSGNATHUS Harris and Hollingsworth, 

1933

Type species.—Cavusgnathus alia Harris and 

Hollingsworth, 1933

p. 201, lOa, b 

Cavusgnathus altus Harris and Hollingsworth, 1933

Plate 1, figure 27

For synonymy to 1968, see Thompson and Goebel (1969). 

1969 Cavusgnathus alta Harris and Hollingsworth.

Thompson and Goebel, p. 21, 22, pi. 1, figs. 19, 22. 

1979 Cavusgnathus altus Harris and Hollingsworth.

Chaplin, p. 276, pi. 3, figs. 1-3. 

1981 Cavusgnathus altus Harris and Hollingsworth.

Rexroad, p. 7, 8, pi. 1, figs. 28-34. 

1985 Cavusgnathus altus Harris and Hollingsworth.

Wardlaw, p. 400, pi. 3, fig. 13. 

1991 Cavusgnathus altus Harris and Hollingsworth.

Stone, p. 17, pi. 4, figs. 1?, 2?, 4, 5?. 

Remarks.—Three specimens of Cavusgnathus altus 

have a posterior process with 1 or 2 low denticles, a common characteristic of the species (see photograph of holotype in Rexroad and Lane, 1966).

Distribution in the study section.—1 to 22 m above the 

base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone).

Known stratigraphic range.—upper Meramecian to 

uppermost Chesterian (Upper muricatus Subzone). 

Material.—3 Pa elements.

Cavusgnathus? tytthus Brown and Rexroad, 1990

Plate 1, figures 7-12; plate 5, figure 20

1980 Adetognathus lautus (Gunnell). Tynan, p. 1298,

1299, pi. 2, fig. 22 (only). 

1980 Adetognathus n. sp. Tynan, p. 1299, pi. 2, figs. 15-

17. 

1990 Cavusgnathus tytthus Brown and Rexroad. Brown

and others, p. 81, 82, text-fig. 5 [part], pi. 1, figs. 1,

4-6, 10-12, 14, 18. 

71991 Adetognathus sp. cf. Adetognathus n. sp. Tynan.

Morrow and Webster, pi. 2, figs. 5, 6. 

Description.—Three Pa-element morphotypes occur in 

the Wahoo Limestone. The two most abundant morphotypes are right sided. The first (pi. 1, figs. 7, 8; = a morphotype of Brown and Rexroad, in Brown and others, 1990) has 

a free blade with three to four denticles that joins the right 

parapet (outer) and continues as a fixed blade bearing two

to three denticles; the posteriormost denticle is the largest; 

therefore, the upper blade profile increases in height posteriorly. The left parapet intercepts the blade two to four denticles behind its anterior margin. In lateral view, the outer 

margin is slightly to considerably higher than the inner margin. The free blade of the second morphotype (pi. 1, figs. 9, 

10; = p morphotype of Brown and Rexroad, in Brown and 

others, 1990) joins the platform on or slightly left of the 

right parapet; the very low posteriormost denticle may be 

slightly to moderately offset to the left; a notch separates the 

blade from the platform. The upper margin profile of the 

blade forms a moderate asymmetric arch that is highest in 

the middle, descends only slightly anteriorly, but steeply 

posteriorly. In lateral view, the right parapet margin is 

slightly to considerably higher than the left. The third and 

rarest Pa morphotype (pi. 1, figs. 11, 12; = y morphotype of 

Brown and Rexroad, in Brown and others, 1990) has a free 

blade that joins the platform centrally or subcentrally 

toward the right. The blade has the same upper margin profile as the p morphotype; the two very low, posteriormost 

denticles of the blade continue onto the platform as a short 

carina. In lateral view, right and left parapet margins are 

approximately equal in height.

Remarks.—Characteristics of the a morphotype do not 

appear to change ontogenetically; the p morphotype develops a carinal extension of the blade ontogenetically; no 

juveniles of the y morphotype were found. The collections 

contain chiefly adult specimens. Specimens of Cavusgnathusl tytthus in the Wahoo Limestone differ slightly 

from topotype material from the Kinkaid Limestone of the 

Illinois basin. Carinal extensions of the blade in the p and y 

morphotypes that are obvious in the material from the 

Wahoo Limestone were not noted by Brown and Rexroad 

(in Brown and others, 1990). This is probably because their 

specimens are small; the name they chose for the species 

reflects that condition. The trivial name is somewhat unsuitable for the material from the Wahoo Limestone in which 

most representatives of the species are rather large.

Because no left-bladed specimens appear to occur in 

Cavusgnathusl tytthus, it seems inappropriate to place the 

species in Adetognathus, even though its fixed blade is short 

and, in some morphotypes, may be absent. Presently, it 

seems best to questionably retain it in Cavusgnathus. The 

array of morphotypes that occur in C.I tytthus is reminiscent of morphotypes assigned to older Mississippian 

species of Taphrognathus and Cloghergnathus that are 

found in shallow-water, somewhat restricted depositional 

environments.

Brown and Rexroad (in Brown and others, 1990) theorized that Cavusgnathusl tytthus is the phylogenetic link 

between C. unicornis and C. monocerus (- Adetognathus 

unicornis (Rexroad and Burton) of Lane, 1967). Cavusgnathusl tytthus occurs with abundant representatives of C. 

unicornis in the lower part of its range in our section; C. 

unicornis does not occur above the lower 51 m of the
SYSTEMATIC PALEONTOLOGY 35

Wahoo Limestone, and C. monocerus is absent at the study 

section. Thus, our data neither confirm nor contradict 

Brown and Rexroad's phylogenetic hypothesis.

Distribution in the study section.—22 to 76.5 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

lowermost Morrowan; Upper muricatus Subzone to within 

noduliferus-primus Zone). Cavusgnathus! tytthus occurs in 

the upper part of the Alapah Limestone and in many collections from the Wahoo Limestone in the northeast Brooks 

Range including the type section at Wahoo Lake (app. 1, 

loc. 4Alc), at Plunge Creek (app. 1, loc. 6), and as far east 

as the Clarence River at the Canadian border (app. 1, Iocs. 

lOAlb, c).

Known stratigraphic range.—upper Chesterian and 

lower Morrowan (upper part of naviculus Zone (Brown and 

others, 1990) into noduliferus-primus Zone).

Material.—99 Pa and 3 Pb (pi. 5, fig. 20) elements.

Cavusgnathus unicornis Youngquist and Miller, 1949

Plate 1, figures 28-31; plate 2, figures 1-17

For synonymy to 1987, see Rexroad and Horowitz (1990).

Additions and exceptions are noted below.

1979 Cavusgnathus unicornis Youngquist and Miller.

Aisenverg and others, pi. 6, fig. 8. 

1985 Cavusgnathus unicornis Youngquist and Miller.

Skipp and others, pi. 8, fig. 10. 

1987 Cavusgnathus unicornis Youngquist and Miller.

Armstrong and Purnell, pi. 1, figs. 11-13 (only).

1989 Cavusgnathus unicornis Youngquist and Miller. 

Wang and Higgins, p. 275, 276, pi. 13, figs. 2-4.

1990 Cavusgnathus unicornis Youngquist and Miller. 

Rexroad and Horowitz, p. 499, 500, pi. 1, figs. 5-20.

1991 Cavusgnathus unicornis Youngquist and Miller. 

Morrow and Webster, pi. 3, figs. 1-3.

1992 Cavusgnathus unicornis Youngquist and Miller.

Morrow and Webster, pi. 1, fig. 1. 

1992 Cavusgnathus unicornis Youngquist and Miller.

Purnell, p. 10, 11, pi. 2, figs. 1-5, 7. 

1992 Cavusgnathus cf. unicornis Youngquist and Miller.

Purnell, pi. 2, fig. 6. 

1992 Cavusgnathus unicornis Youngquist and Miller.

Weibel and Norby, pi. 1, fig. 18. 

Remarks.—Rexroad (1981) synonymized Cavusgnathus regularis (P morphotype) and C. convexus (y morphotype) under C. unicornis (a morphotype). All specimens 

have a right-sided free blade that is shorter than the fixed 

blade. In the a morphotype, denticles decrease in size anteriorly; the largest denticle is posteriormost. The blade profile of the P morphotype is uniform in height or may 

decrease slightly anteriorly. The blade profile of the y morphotype is arched. In collections from the study section, 

many of the blade denticles are broken so that morphotypes 

are indeterminate. Of the complete specimens, a and (3 morphotypes are more common than y morphotypes.

Wardlaw (1985, pi. 2, figs. 9-11, 13) included robust, 

digyrate elements in the apparatus of Cavusgnathus naviculus that he claimed were vicariously shared by most species 

of Cavusgnathus, including C. unicornis. We strongly disagree with this reconstruction and concur with the element 

morphotypes determined by Norby (1976) from natural 

assemblages. The digyrate elements Wardlaw attributed to 

Cavusgnathus belong instead to Kladognathus (see Merrill 

and others, 1990). Armstrong and Purnell (1987) also 

included an Sc element of Kladognathus as well as two 

morphologically dissimilar M elements in the apparatus of 

C. unicornis.

Distribution in the study section.—0.4 to 50.5 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone).

Known stratigraphic range.—upper Meramecian to 

uppermost Chesterian (Upper muricatus Subzone).

Material.—415 Pa, 11 Pb, 26 M, and 6 Sc elements.

Cavusgnathus spp. indet.

Remarks.—Chiefly broken, abraded, or juvenile Pa 

elements are included in this category.

Distribution in the study section.—13.2 to 53 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone).

Known stratigraphic range.—upper Meramecian to 

uppermost Chesterian (Upper muricatus Subzone).

Material—122 Pa elements.

Cavusgnathoids

Remarks.—Included are posterior Pa-element fragments of Cavusgnathus, Cavusgnathusl, orAdetognathus.

Distribution in the study section.—0.4 to 137 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

Morrowan; Upper muricatus Subzone to lower minutus 

Fauna).

Known stratigraphic range.—upper Meramecian to 

Lower Permian.

Material.—419 Pa element fragments.

Genus DECLINOGNATHODUS Dunn, 1966

Type species.—Cavusgnathus nodulifera Ellison and

Graves, 1941 

p. 4,5, pi. 3, figs. 4, 6

Remarks.—Dunn (1970b) expanded the concept of the 

genus to include forms with a median longitudinal trough 

and a long, slightly declined, medial carina (= Declinognathodus lateralis (Higgins and Bouckaert)). Grayson and 

others (1990) concurred with Dunn's emendation but considered D. lateralis morphotypes as vertically persistent 

species of Declinognathodus that are convergent with 

Neognathodus.
36 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

Declinognathodus noduliferus (Ellison and Graves, 

1941)

Gray son and others (1990) provide an extensive synonymy for the species.

Remarks.—Declinognathodids in our collections are 

assigned to Declinognathodus noduliferus noduliferus, D. 

n. japonicus, or D. n. subspp. indeterminate. A few specimens in a single collection (USGS colln. 30786-PC; pi. 3, 

fig. 32), 187 m above the base of the Wahoo Limestone, 

resemble forms assigned to D. lateralis (Higgins and 

Bouckaert) by other workers. These specimens are the largest declinognathodids in a sample that also contains the 

most abundant and largest rhachistognathids in our collections. We suspect that these D. lateralis morphotypes are 

ecophenotypic and (or) gerontic specimens. Consequently, 

they are included in D. noduliferus.

Specimens identified as Declinognathodus noduliferus 

japonicus, however, exhibit variation in ornamentation, 

deflection of the carina, and spacing of posterior nodes 

within each sample throughout the Wahoo Limestone. 

Some specimens have transverse ridges on the anterior 

inner margin (pi. 3, figs. 6, 7). All specimens of D. n. 

japonicus have one or two accessory nodes that are in contact with or cleanly separated from the carina near the anterior platform margin. Juvenile specimens tend to have more 

widely spaced posterior nodes and a straighter carina. Specimens with very nodose ornamentation (pi. 3, fig. 22) are 

rare and considered ecophenotypes; Gray son (1984, p. 50) 

erected a separate species (Idiognathoides marginodosus', = 

Declinognathodus marginodosus of Grayson, 1990) for 

such forms. We see no stratigraphic succession of D. noduliferus morphotypes in our section and, therefore, retain 

these forms in D. n. japonicus.

Declinognathodus noduliferus japonicus (Igo and Koike, 

1964)

Plate 3, figures 1-8, 19-22

1964 Streptognathodus japonicus Igo and Koike, p. 188, 

189, pi. 28, figs. 5-10, 711-13.

1966 Declinognathodus nevadensis Dunn, p. 1300, 

pi. 158, figs. 4, 8.

1967 Gnathodus nodulifera (Ellison and Graves). Koike, 

p. 297, 298, pi. 3, figs. 9, 11 (only).

1967 Idiognathoides aff. /. nodulifera (Ellison and 

Graves). Lane, p. 938, pi. 123, figs. 10, 13 (only).

1968 Gnathodus japonicus (Igo and Koike). Higgins and

Bouckaert, p. 35, 36, pi. 4, figs. 1, 2, 4. 

1970b Declinognathodus noduliferus (Ellison and Graves).

Dunn, p. 330, pi. 62, fig. 1 only, text-fig. 9D. 

1970 Idiognathoides noduliferus (Ellison and Graves).

Thompson, p. 1046, 1047, pi. 139, figs. 2?, 3?, 5, 6,

8, 16,20.

1971 Gnathodus noduliferus (Ellison and Graves). Lane 

and others, pi. 1, fig. 32.

1971 Idiognathoides noduliferus (Ellison and Graves). 

Lane and others, pi. 1, fig. 11.

1972 Idiognathoides noduliferus (Ellison and Graves) 

transitional to Streptognathodus lateralis Higgins 

and Bouckaert. Austin, pi. 1, figs. 33, 40.

1972 Unnamed figured specimens. Austin, pi. 2, figs. 27, 

28.

1974 Idiognathoides noduliferus (Ellison and Graves). 

Lane and Straka, p. 85-87, figs. 35: 1-3, 5?, 6?, 10-

12. 13-15?.

1975 Idiognathoides noduliferus japonicus (Igo and 

Koike). Higgins, p. 54, pi. 14, figs. 7-10.

1979 Declinognathodus noduliferus (Ellison and Graves). 

Semichatova and others, pi. 22, figs. 12, 13.

1980 Idiognathoides noduliferus japonicus (Igo and 

Koike). Metcalfe, p. 306, pi. 38, figs. 14?, 17?.

?1984 Declinognathodus noduliferus japonicus (Igo and 

Koike). Orchard and Struik, pi. 2, fig. 9.

1984 Idiognathoides marginodosus Morphotype B, Grayson, p. 50, pi. 1, figs. 3, 4, 9-11 (pi. 2, fig. 17= pi. 1, 

fig. 10), 13, 14; pi. 3, fig. 19?; pi. 4, figs. 11, 12, 22.

1985 Declinognathodus noduliferus japonicus (Igo and 

Koike). van den Boogaard and Bless, p. 140, 141, 

fig. 9: 5.

1985a Declinognathodus noduliferus japonicus (Igo and 

Koike). Grayson and others, p. 163-165, pi. 1, figs.

13. 18.

1985b Idiognathoides marginodosus Grayson. Grayson 

and others, pi. 1, fig. 21.

?1985a Declinognathodus noduliferus (Ellison and Graves). 

Lane and others, figs. 7D-G [figs. 7D, E, IDeclinognathodus noduliferus; figs. 7F, G, D. noduliferus 

japonicusl].

1985 Declinognathodus noduliferus (Ellison and Graves). 

Sada and others, pi. 1, fig. 3.

1987 Declinognathodus marginodosus (Grayson). Grayson and others, pi. 8, figs. 8, 11.

1987 Declinognathodus noduliferus japonicus (Igo and 

Koike). Nemirovskaya, pi. 1, figs. 12, 15, 19.

1988 Declinognathodus noduliferus japonicus (Igo and 

Koike). Dong and Ji, pi. 6, figs. 7, 8.

1989 Declinognathodus noduliferus japonicus (Igo and 

Koike). Wang and Higgins, p. 276, pi. 1, figs. 6-9.

1990 Declinognathodus marginodosus (Grayson). Grayson, p. 90, 91, pi. 4, figs. 9, 10?, 11-13.

1990 "Declinognathodus" marginodosus (Grayson). 

Grayson and others, p. 365, pi. 1, fig. 28.

1990 "Declinognathodus" noduliferus (Ellison and 

Graves). Grayson and others, p. 365, pi. 1, fig. 21.

1992a Declinognathodus noduliferus s.l. (Ellison and 

Graves). Nigmadganov and Nemirovskaya, pi. 3, 

figs. 6?, 7, 10.
SYSTEMATIC PALEONTOLOGY 37

1992 Declinognathodus marginodosus (Grayson). Sutherland and Grayson, pi. 2, fig. 11.

Remarks.—Most specimens are identical to the types 

of Declinognathodus noduliferus japonicus. Several specimens (pi. 3, fig. 22), however, have an undeflected carina, 

relatively even-noded margin and carina, and a single, 

prominent, round node that is cleanly separated from the 

carina near the anterior margin of the outer lobe. Such 

forms were included in D. marginodosus by Grayson (1990) 

and Sutherland and Grayson (1992). We include these in D. 

n. japonicus because some populations are intergradational 

between D. n. japonicus and D. marginodosus (Grayson). 

We regard D. marginodosus to be a possible shallower 

water ecophenotype of D. n. japonicus. Partial division of 

the anteriormost node produces an incipient third node in a 

few specimens (pi. 3, fig. 9).

Distribution in the study section.—56 to 250 m above 

the base of the Wahoo Limestone (lowest Morrowan to 

lower Atokan; noduliferus-primus Zone to Idiognathodus 

Fauna).

Known stratigraphic range.—lowest Morrowan 

(base of noduliferus-primus Zone) to at least lower 

Desmoinesian(?).

Material.—144 Pa elements.

Declinognathodus noduliferus noduliferus (Ellison and 

Graves, 1941)

Plate 3, figures 10-14, 32

1941 Cavusgnathus nodulifera Ellison and Graves, p. 4,

5, pi. 3, fig. 4 (only). 

1960 Streptognathodus parallelus Clarke, p. 29, pi. 5,

figs. 6-8, 14, 15. 

1967 Gnathodus nodulifera (Ellison and Graves). Koike,

p. 297, 298, pi. 3, figs. 10, 12? (only). 

71967 Idiognathoides aff. /. nodulifera (Ellison and

Graves). Lane, p. 938, pi. 123, figs. 9, 11, 17 (only). 

1968 Gnathodus noduliferus (Ellison and Graves).

Higgins and Bouckaert, p. 33-35, pi. 2, figs. 6, 12.

1968 Idiognathoides nodulifera (Ellison and Graves). Igo 

and Koike, p. 28, 29, pi. 3, figs. 7, 8, 9?, 10 (only).

1969 Streptognathodus noduliferus (Ellison and Graves).

Webster, p. 48, 49, pi. 4, figs. 7, 8. 

1970b Declinognathodus noduliferus (Ellison and Graves).

Dunn, p. 330, pi. 62, fig. 2 (only). 

1971 Gnathodus noduliferus (Ellison and Graves). Lane

and others, pi. 1, fig. 32. 

71971 Idiognathoides noduliferus (Ellison and Graves).

Lane and others, pi. 1, fig. 11. 

1972 Idiognathoides noduliferus (Ellison and Graves)

transitional to Streptognathodus lateralis Higgins

and Bouckaert. Austin, pi. 1, figs. 2, 4, 5, 7, 11, 12,

14, 15, 16?, 17?, 18, 19, 27, 29-32, 34-36?, 38, 39,

41,44, 45, 49, 50, 53?, 54.

1972 Streptognathodus lateralis Higgins and Bouckaert.

Austin, pi. 2, fig. 31. 

1972 Unnamed figured specimen. Austin, pi. 2, fig. 33.

1974 Idiognathoides noduliferus (Ellison and Graves). 

Lane and Straka, p. 85-87, pi. 35, figs. 11-13; pi. 

41, figs. 15-17.

?1974 Gnathodus noduliferus (Ellison and Graves). Merrill, pi. 1, figs. 28,29.

1975 Idiognathoides noduliferus noduliferus (Ellison and 

Graves). Higgins, p. 54, pi. 14, figs. 15, 16.

1975 Idiognathoides noduliferus inaequalis Higgins. Higgins, pi. 12, figs. 3, 4.

1979 Declinognathodus noduliferus (Ellison and Graves). 

Aisenverg and others, pi. 6, figs. 17, 18.

1979 Streptognathodus noduliferus (Ellison and Graves). 

Einor and others, pi. 14, figs. 6, 7.

1980 Idiognathoides noduliferus (Ellison and Graves).

Bender, p. 12, pi. 1, figs. 3?, 8-15, 16?. 

1980 Idiognathoides noduliferus inaequalis Higgins.

Metcalfe, p. 306 (part), pi. 38, fig. 15. 

1980 Idiognathoides noduliferus noduliferus (Ellison and

Graves). Metcalfe, p. 306, pi. 38, figs. 16, 18.

1984 Idiognathoides marginodosus Morphotype A, Grayson, p. 50, pi. 1, fig. 7.

1985a Declinognathodus noduliferus japonicus (Igo and 

Koike). Grayson and others, p. 163-165, pi. 1, figs. 

9, 15, 25.

1985 Declinognathodus noduliferus inaequalis (Higgins).

Higgins, pi. 6.2, figs. 11, 14; pi. 6.3, figs. 1, 4. 

1985 Declinognathodus noduliferus noduliferus (Ellison

and Graves). Higgins, p. 220, pi. 6.2, figs. 13, 15; pi.

6.3, fig. 7. 

1985 Idiognathoides noduliferus (Ellison and Graves).

Plafker and others, figs. 48A, B. 

1985 Idiognathoides noduliferus (Ellison and Graves).

Savage and Barkeley, p. 1466, 1467, figs. 9: 1-8. 

?1985 Declinognathodus noduliferus (Ellison and Graves).

Skipp and others, pi. 8, fig. 8 [form transitional from

Gnathodus girtyi to D. noduliferus]. 

1985 Declinognathodus noduliferus (Ellison and Graves).

Wardlaw, p. 397, pi. l,fig. 1.

1987 Declinognathodus marginodosus (Grayson). Grayson and others, pi. 8, figs. 16?, 23, 28?. 

1987 Declinognathodus noduliferus (Ellison and Graves).

Nemirovskaya, pi. 1, figs. 7, 9, 11, 20, 21. 

1987 Declinognathodus inaequalis (Higgins). Riley and

others, pi. 3, fig. 30?. 

1987 Declinognathodus noduliferus (Ellison and Graves).

Riley and others, pi. 3, figs. 41?, 42, 43, 44?, 46, 47.

1987 Declinognathodus noduliferus noduliferus (Ellison 

and Graves). Wang and others, p. 127, pi. 3, figs. 3- 

5; pi. 7, fig. 1.

1988 Declinognathodus noduliferus inaequalis (Higgins). 

Dong and Ji, pi. 6, fig. 9.
38 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

1988 Declinognathodus noduliferus noduliferus (Ellison 

and Graves). Dong and Ji, pi. 6, figs. 5, 6.

1989 Declinognathodus noduliferus noduliferus (Ellison 

and Graves). Wang and Higgins, p. 276, 277, pi. 2, 

figs. 5-9.

1990 Declinognathodus noduliferus (Ellison and Graves). 

Grayson, pi. 1, figs. 10, 13; pi. 3, fig. 29.

1990 Declinognathodus noduliferus (Ellison and Graves). 

Grayson and others, p. 362, 363, pi. 1, fig. 21.

1991 Declinognathodus noduliferus noduliferus (Ellison 

and Graves). Gibshman and Akhmetshina, pi. 5, 

figs. 7, 8.

1991 Declinognathodus noduliferus inaequalis Higgins. 

Nemirovskaya and others, pi. 4, figs. 3, 5?, 15.

1992 Declinognathodus noduliferus (Ellison and Graves). 

Morrow and Webster, pi. 1, fig. 5.

1993 Declinognathodus noduliferus inaequalis (Higgins). 

Duan, p. 206, pi. 3, figs. 7, 8?, 9.

Remarks.—Almost all specimens from the Wahoo 

Limestone assigned to Declinognathodus noduliferus noduliferus have nodose and (or) transversely ridged parapets, an 

outwardly deflected carina, and three or more accessory 

nodes on the anterior outer margin (pi. 3, fig. 12). The carina merges with the outer parapet within or slightly posterior to the anterior half of the platform (pi. 3, figs. 11, 12). 

According to Higgins (1975, 1985), specimens of D. noduliferus in which the carina merges with the outer parapet 

within the posterior half of the platform should be referred 

to D. n. inaequalis. None of our specimens are comparable 

to the holotype of D. n. inaequalis, which has a carina that 

extends well beyond the anterior half of the platform.

Distribution in the study section.—59 to 250 m above 

the base of the Wahoo Limestone (lowest Morrowan to 

lower Atokan; base of noduliferus-primus Zone to Idiognathodus Fauna).

Known stratigraphic range.—lowest Morrowan (base 

of noduliferus-primus Zone) to lower Desmoinesian(?).

Material—285 Pa elements.

Declinognathodus noduliferus subspp. indet.

Remarks.—Included are chiefly broken, abraded, and 

juvenile Pa elements.

Distribution in the study section.—65 to 243 m above 

the base of the Wahoo Limestone (lower Morrowan to 

lower Atokan; noduliferus-primus Zone to Idiognathodus 

Fauna).

Known stratigraphic range.—lowest Morrowan (base 

of noduliferus-primus Zone) to lower Desmoinesian(?).

Material.—18 Pa elements.

Genus DIPLOGNATHODUS Kozur and Merrill, 1975

Type species.—Spathognathodus coloradoensis Murray

and Chronic, 1965 

p. 606, 607, pi. 72, figs. 11-13

Remarks.—von Bitter and Merrill (1990) recommend 

that only forms having a spatulate carina be included within 

the genus. They admit that species presently assigned to the 

genus are morphologically variable and probably polyphyletic. A single specimen is tentatively assigned to Diplognathodusl ellesmerensis, a species questionably included in 

Diplognathodus because its Pa element has a denticulate 

carina.

Diplognathodus^ ellesmerensis Bender, 1980?

Plate 5, figures 18, 19

1980 Diplognathodus ellesmerensis Bender, p. 9, 10, 

pi. 4, figs. 5-7, 11, 15-21, 23-25.

1981 Diplognathodus coloradoensis (Murray and

Chronic). Landing and Wardlaw, p. 1257-1259,

pi. l.figs. 1,6,7,9, 10. 

1983 Diplognathodus ellesmerensis Bender, van den

Boogaard, p. 23, 24, pi. 1, fig. a. 

1985 Diplognathodus coloradoensis (Murray and

Chronic). Savage and Barkeley, p. 1473, figs. 12: 9-

16. 

1990 Diplognathodusl ellesmerensis Bender, von Bitter

and Merrill, fig. 4: 16a-c. 

1992 Diplognathodus sp. A. Sutherland and Grayson,

pi- 2, fig. 9. 

71993 Diplognathodus? orphanus Merrill. Lemos, pi. 4,

fig. 6.

Description.—One poorly preserved juvenile(?) Pa 

element has a free blade bearing eight partly fused denticles. The upper margin profile of the blade gradually 

increases in height from the anterior margin to midlength 

and then descends abruptly at the intersection of the blade 

and platform. A carina of eight mostly fused but distinct 

denticles gradually decreases in height toward the posterior 

tip of the platform. The platform margin is incomplete; the 

lobes appear to be unornamented, oval, and possibly symmetrical. The basal cavity is gnathodontid.

Remarks.—The single specimen resembles Diplognathodusl ellesmerensis but has a few more denticles on the 

carina than specimens illustrated by Bender (1980). Moreover, the upper margin profile of the posterior end of the 

carina decreases abruptly in height and is adenticulate in 

most of Bender's specimens.

We agree with Bender (1980) and von Bitter and Merrill (1990) that this species is closer to Diplognathodusl 

orphanus (Merrill) than to other diplognathodids.

Distribution in the study section.—203 m above the 

base of the Wahoo Limestone (upper Morrowan or lower 

Atokan; Idiognathodus Fauna).
SYSTEMATIC PALEONTOLOGY 39

Known stratigraphic range.—Diplognathodus? ellesmerensis is known from the Canadian Arctic islands, 

Yukon, southeast Alaska, Oklahoma, Michigan, and Spain 

and apparently ranges from upper Morrowan to Desmoinesian (von Bitter and Merrill, 1990, fig. 4). Sutherland and 

Manger (1984a) recommended that the first appearance of 

Diplognathodus or the foraminifer Eoschubertella be used 

as a guide to the base of the Atokan. This recommendation 

preceded the recognition of diplognathodids in the Morrowan (von Bitter and Merrill, 1990). Diplognathodusl 

orphanus appears to be the only known species restricted to 

the Atokan.

Material.—1 Pa element.

Genus GNATHODUS Pander, 1856

Type species.—Polygnathus bilineatus Roundy, 1926 

p. 13, pi. 3, figs. lOa-c

Remarks.—Gnathodus bilineatus (Roundy) was designated the type species of Gnathodus by Tubbs (1986) 

because the types of G. mosquensis, the oldest described 

species of the genus, were lost and its type locality was 

uncertain.

Gnathodus bilineatus bilineatus (Roundy, 1926)

Plate 2, figures 18, 19; plate 5, figure 23

Only a selected synonymy is given because this subspecies 

is widespread, commonly figured and cited in the literature, 

and relatively easily diagnosed. See Wang and others 

(1987) for additional selected synonymy through 1983. 

1926 Polygnathus bilineatus Roundy, p. 13, pi. 3,

figs. lOa-c. 

1926 Polygnathus texanus Roundy, p. 14, pi. 3,

figs. 13a, b. 

1953 Gnathodus bilineatus (Roundy). Hass, p. 78-80,

pi. 14, figs. 25-29. 

1958 Gnathodus bilineatus (Roundy). Stanley, p. 464,

465, pi. 68, fig. 7. 

1961 Gnathodus bilineatus (Roundy). Higgins, pi. 10,

fig. 5. 

71965 Gnathodus bilineatus (Roundy). Dunn, p. 1148,

pi. 140, figs. 7-9. 

1967 Gnathodus bilineatus (Roundy). Globensky, p. 440,

pi. 58, figs. 9?, 13.

1967 Gnathodus bilineatus (Roundy). Koike, p. 296, 

pi. 1, figs. 9-11.

1968 Gnathodus bilineatus bilineatus (Roundy). Higgins

and Bouckaert, p. 29, pi. 3, fig. 9. 

1971 Gnathodus bilineatus (Roundy). Rhodes and Austin,

pi. 2, fig. 1. 

1974 Gnathodus bilineatus bilineatus (Roundy). Austin

and others, pi. 1, figs. 4, 5, 15, 19, 23. 

1974 Gnathodus bilineatus (Roundy). GromczakiewiczLomnicka, pi. I, fig. 1.

1974 Gnathodus bilineatus (Roundy). Matthews and 

Thomas, pi. 50, fig. 19; pi. 51, figs. 12-15, 21-24.

1974 Gnathodus sp. Matthews and Thomas, pi. 50, 

fig. 22.

1974 Gnathodus bilineatus (Roundy). Rice and Langenheim, p. 27, pi. 1, fig. 11.

1975 Gnathodus bilineatus bilineatus (Roundy). Higgins,

p. 28, 29, pi. 11, figs. 1-4,6,7. 

1979 Gnathodus bilineatus bilineatus (Roundy). Aisenverg and others, pi. 6, fig. 12. 

1979 Gnathodus bilineatus Morphotype B. Chaplin, p.

276, 279, pi. 3, figs. 8-11; pi. 4, figs. 1, 2; pi. 5,

fig. 2. 

1985 Gnathodus bilineatus bilineatus (Roundy). Higgins,

p. 218, pi. 6.1, figs. 1,2. 

1985 Gnathodus bilineatus (Roundy). Varker and Sevastopulo, p. 199, pi. 5.4, figs. 19, 20.

1985 Gnathodus bilineatus (Roundy). Wardlaw, pi. 1, 

fig. 10.

1986 Gnathodus bilineatus bilineatus (Roundy). Ji, pi. 1,

figs. 1-4, 6, 8-10.

1986 Gnathodus bilineatus (Roundy). Li, pi. 1, figs. 1, 8. 

1986 Gnathodus bilineatus (Roundy). Mapes and

Rexroad, p. 117, pi. 2, figs. 22-31.

1986 Gnathodus bilineatus (Roundy). Ruppel and 

Lemmer, p. 28, pi. 2, figs. 14, 15.

1987 Gnathodus bilineatus (Roundy). Grayson and others, pi. 3, figs. 11, 36; pi. 4, figs. 20-23.

1987 Gnathodus bilineatus (Roundy). Merrill, p. 147- 

151, pi. 11, figs. 1-6,9-18.

1987 Gnathodus bilineatus bilineatus (Roundy). Riley 

and others, pi. 2, figs. 2, 4.

1987 Gnathodus bilineatus bilineatus (Roundy). Wang 

and others, p. 128, pi. 1, fig. 6.

1988 Gnathodus bilineatus bilineatus (Roundy). Dong 

and Ji, pi. 4, figs. 6-8, 10.

1989 Gnathodus bilineatus (Roundy). Ellison and Powell, 

pi. 2, figs. 1-6, 13-16.

1989 Gnathodus bilineatus bilineatus (Roundy). Wang 

and Higgins, p. 277, 278, pi. 6, figs. 7-11.

1990 Gnathodus bilineatus (Roundy). Grayson, pi. 1, 

figs. 25,267-31.

1990 Gnathodus bilineatus (Roundy). Grayson and others, p. 361, 362, pi. 1, figs. 1, 3-6, 10-14, 18-20 

[figs. 2, 7-9 appear to include two different Pb 

morphotypes and have thus been excluded].

1990a Gnathodus bilineatus (Roundy). Ramovs, p. 91, 92, 

pi. 4, figs. 2, 4, 5, 9, 12.

1990b Gnathodus bilineatus (Roundy). Ramovs, p. 109, pi. 

I, figs. 1-3, 11.

1991 Gnathodus bilineatus bilineatus (Roundy). Higgins

and others, pi. 3, fig. 19. 

1992a Gnathodus bilineatus bilineatus (Roundy). Nigmadganov and Nemirovskaya, pi. 1, fig. 3.
40 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

1992a Gnathodus bilineatus bollandensis Higgins and 

Bouckaert. Nigmadganov and Nemirovskaya, pi. 1, 

figs. 1, 2.

1993 Gnathodus bilineatus (Roundy). Alekseev and 

Kononova, pi. 29, figs. 8, 10.

1994 Gnathodus bilineatus (Roundy). Kolar-Jurkovsek 

and Jurkovsek, p. 432, pi. 2, figs. 6-8.

Distribution in the study section.—0.4 to 53 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone) and 69 m above the base of the 

Wahoo (lower Morrowan—redeposited?).

Known stratigraphic range.—upper Meramecian into 

lowermost Morrowan. Wang and Higgins (1989) report 

Gnathodus bilineatus bilineatus from the lowermost upper 

Carboniferous in China, but all their figured specimens are 

from uppermost lower Carboniferous strata. Gnathodus 

bilineatus bilineatus and (or) G. b. bollandensis have been 

reported from lowermost upper Carboniferous strata (in 

samples containing Declinognathodus noduliferus or other 

late Carboniferous species) in many parts of the world (for 

example, Malaysia, Metcalfe, 1980; South China, Wang and 

Higgins, 1989; Texas, Grayson and others, 1990; Ukraine, 

Nemirovskaya and others, 1991; south Tienshan, Uzbekistan, Nigmadganov and Nemirovskaya, 1992a). We regard 

the specimen of G. b. bilineatus (pi. 5, fig. 23) that occurs 

13m above the lowest D. n. japonicus in the Wahoo Limestone to be redeposited.

Material.—8 Pa elements.

Gnathodus bilineatus subsp. indet.

Remarks.—A few small specimens can be identified 

only as G. bilineatus.

Distribution in the study section.—37 to 53 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone).

Known stratigraphic range.—upper Meramecian into 

lowermost Morrowan.

Material.—3 Pa elements.

Gnathodus defectus Dunn, 1966

Plate 2, figures 23, 24, 31-33; plate 4, figure 26

1966 Gnathodus defectus Dunn, p. 1300, pi. 158, figs. 1,

5. 

1969 Gnathodus defectus Dunn. Webster, p. 32, pi. 5,

fig. 16.

1970a Gnathodus defectus Dunn. Dunn, text-fig. 4. 

1970b Gnathodus defectus Dunn. Dunn, p. 331, pi. 62,

figs. 15, 16; text-fig. 9C.

1980 Gnathodus defectus Dunn. Tynan, pi. 1, fig. 20. 

?1985a Gnathodus defectus Dunn. Grayson and others,

p. 166, pi. 1, fig. 21. 

71991 Gnathodus sp. cf. G. defectus Dunn. Higgins and

others, pi. 3, fig. 9.

1991 Gnathodus defectus Dunn. Morrow and Webster, 

pi. 3, figs. 6, 7.

1992 Gnathodus defectus Dunn. Morrow and Webster, 

pi. 1, fig. 2.

1993 Gnathodus defectus Dunn. Dumoulin and Harris, 

fig. 8£.

Remarks.—Most specimens assigned to this species 

are considerably smaller than those illustrated from Nevada 

by Dunn (1966). Most, however, are like the specimen illustrated by Dunn (1970b) on plate 62, figure 16 and 

text-figure 9C.

Distribution in the study section.—54.9? to 157 m 

above the base of the Wahoo Limestone.

Known stratigraphic range.—From within the Chesterian (from at least below the muricatus Zone) to at least the 

lower Morrowan (lower minutus Fauna). Dunn (1966) indicated that Gnathodus defectus extended into the lowest 

Morrowan because it occurred in samples with Rhachistognathus primus. Wardlaw (1984) and Morrow and Webster 

(1992) considered G. defectus in Pennsylvanian samples 

indigenous; however, it is possible that the sporadic 

occurrence of G. defectus from 30 to 102 m above the 

Mississippian-Pennsylvanian boundary in the study section 

indicates redeposition. Some redeposited Mississippian 

conodonts occur in the Pennsylvanian part of the section 

(table 1). Gnathodus defectus occurs in four samples from 

the lower member of the Wahoo Limestone between 157.5 

and 100.5 m below the Wahoo Limestone and Echooka Formation contact at Pogopuk Creek (samples collected by 

S.K. Morgan, University of Alaska Fairbanks). The conodont species association in the lowest collection indicates 

the noduliferus-primus Zone, and the remaining collections 

are indicative of the lower minutus Fauna (app. 1, loc. 5d). 

The data from Pogopuk Creek and the study section indicate that G. defectus extends well into the Morrowan (into 

the lower minutus Fauna) in the northeast Brooks Range.

Material.—9 Pa elements.

Gnathodus girtyi Hass, 1953

Remarks.—We recognize two subspecies of Gnathodus girtyi in our collections, G. g. girtyi and G. g. simplex.

Gnathodus girtyi girtyi Hass, 1953

Plate 2, figures 20-22

1953 Gnathodus girtyi Hass, p. 80, pi. 14, figs. 22-24.

1956 Gnathodus girtyi Hass. Elias, p. 118, pi. Ill, figs. 30, 

31.

1957 Gnathodus girtyi Hass. Bischoff, p. 24, 25 (part),

pi. 4, figs. 17, 22, 23.

1960 Gnathodus clavatus Clarke, p. 25, pi. 4, figs. 4-8. 

1968 Idiognathoides nodulifera (Ellison and Graves). Igo

and Koike, pi. 3, fig. 11 (only).
SYSTEMATIC PALEONTOLOGY 41

1969 Gnathodus girtyi girtyi Hass. Rhodes and others,

p. 98, 99, pi. 17, figs. 9, 10. 

1969 Gnathodus girtyi simplex Dunn. Rhodes and others,

p. 100, 101, pi. 16, figs. 1^. 

1969 Gnathodus girtyi subsp. nov. A. Rhodes and others,

p. 102, 103, pi. 17, figs. 1-3.

1969 Gnathodus girtyi simplex Dunn. Webster, p. 32, 

pi. 5, fig. 10.

1970a Gnathodus girtyi girtyi Hass. Dunn, text-fig. 4.

1970b Gnathodus girtyi girtyi Hass. Dunn, p. 331, textfig. 9A.

1970 Gnathodus girtyi Hass. Reynolds, p. 10, pi. I, 

figs. 10-12.

1972 Gnathodus girtyi Hass. Austin, pi. 2, figs. 11, 15.

1973 Gnathodus girtyi Hass. Austin and Aldridge, pi. 1,

figs. 4 -6; pi. 2, figs. 2, 13?, 14, 15. 

71974 Gnathodus girtyi girtyi Hass. GromczakiewiczLomnicka, pi. II, fig. 1. 

1974 Gnathodus girtyi simplex Dunn. GromczakiewiczLomnicka, pi. I, fig. 4. 

1974 Gnathodus girtyi Hass. Matthews and Thomas,

pi. 51, figs. 16, 17,28-31. 

1974 Gnathodus sp. Matthews and Thomas, pi. 51,

figs. 8, 9.

1974 Gnathodus girtyi girtyi Hass. Rice and Langenheim, 

pi. l.figs. 15, 16.

1975 Gnathodus girtyi girtyi Hass. Higgins, p. 31, pi. 10, 

figs. 5, 6.

1979 Gnathodus girtyi collinsoni Rhodes and others. 

Aisenverg and others, pi. 6, figs. 1, 2.

1980 Gnathodus girtyi simplex Dunn. Metcalfe, p. 304,

pi. 38, fig. 1. 

1980 Gnathodus girtyi rhodesi Higgins. Metcalfe, p. 304,

pi. 38, fig. 6.

1980 Gnathodus girtyi girtyi Hass. Tynan, p. 1302, pi. 1, 

figs. 16-18.

1981 Gnathodus girtyi Hass. Metcalfe, p. 23, 25, pi. 4,

figs. 2, 4, 5, 7. 

1985 Gnathodus girtyi girtyi Hass. Higgins, p. 220,

pi. 6.2, fig. 2. 

1985 Gnathodus girtyi rhodesi Higgins. Higgins, p. 220,

pi. 6.2, fig. 1.

1985 Gnathodus girtyi girtyi Hass. Wardlaw, pi. 1, fig. 12. 

71987 Gnathodus girtyi Hass. Armstrong and Purnell,

pi. 2, figs. 12, 13. 

1987 Gnathodus girtyi Hass. Grayson and others, pi. 7,

fig. 29. 

71987 Gnathodus girtyi girtyi Hass. Wang and others,

p. 128, pi. 7, figs. 9, 10. 

1988 Gnathodus girtyi girtyi Hass. Dong and Ji, pi. 5,

fig. 14. 

1988 Gnathodus girtyi simplex Dunn. Dong and Ji, pi. 6,

fig. 4. 

1990 (Neo)Gnathodus sp. aff. G. girtyi Hass. Grayson and

others, p. 376, 377, pi. 3, figs. 2-13.

1991 Gnathodus girtyi collinsoni Rhodes and others. Higgins and others, pi. 3, fig. 2.

1991 Gnathodus girtyi girtyi Hass. Higgins and others, 

pi. 3, figs. 3-5.

1991 Gnathodus girtyi girtyi Hass. Morrow and Webster, 

pi. 3, fig. 9.

1992 Gnathodus girtyi girtyi Hass. Morrow and Webster, 

pi. 1, fig. 3.

Remarks.—Gnathodus girtyi girtyi has a welldeveloped transversely ridged anterior inner parapet that 

continues to or close to the posterior end of the platform 

where it is noded and merges with the carina. The anterior 

part of the inner parapet is as high as or higher than the carina. The outer parapet begins posterior to and terminates 

slightly to considerably anterior of the inner parapet and is 

lower than the carina. The carina is central, straight or 

slightly deflected, and continues to the posterior tip of the 

platform where it expands to form split nodes or transverse 

ridges in adult or gerontic specimens (pi. 2, fig. 20).

We are unable to evaluate the taxonomic position of 

the specimens assigned to Gnathodus sp. cf. G. girtyi subspp. by Grayson and others (1985a) as well as many specimens assigned to G. girtyi by other workers without 

examining the actual specimens and the conodont faunule 

in which they occur.

Distribution in the study section.—0.4 to 54.9 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone) and 69 to 74 m (lower Morrowan—redeposited?).

Known stratigraphic range.—upper Meramecian to 

uppermost Chesterian (Upper muricatus Subzone).

Material.—56 Pa elements.

Gnathodus girtyi simplex Dunn, 1965

Plate 2, figures 25-27

1965 Gnathodus girtyi simplex Dunn, p. 1148, pi. 140,

figs. 2, 3, 12.

1970a Gnathodus girtyi simplex Dunn, text-fig. 4. 

1970b Gnathodus girtyi simplex Dunn, p. 331, 332, pi. 62,

fig. 17; text-fig. 9B. 

1971 Gnathodus girtyi collinsoni Rhodes and others.

Rhodes and Austin, pi. 2, fig. 3. 

71974 Gnathodus girtyi simplex Hass. GromczakiewiczLomnicka, pi. II, fig. 3.

1974 Gnathodus girtyi simplex Dunn. Rice and Langenheim, pi. l,figs. 17, 18.

1975 Gnathodus girtyi collinsoni Rhodes and others.

Higgins, p. 30, 31, pi. 10, figs. 1, 2. 

1975 Gnathodus girtyi simplex Dunn. Higgins, p. 33,

pi. 9, figs. 6, 7, 11. 

1980 Gnathodus girtyi collinsoni Rhodes and others.

Tynan, p. 1301, pi. 1, figs. 10, 11. 

1980 Gnathodus girtyi simplex Dunn. Tynan, p. 1303,

pi. 1, figs. 5-7.
42 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

1982 Gnathodus girtyi girtyi Hass. Higgins and WagnerGentis, p. 334, pi. 34, fig. 9. 

1984 Gnathodus girtyi collinsoni Rhodes and others. Qiu,

pi. 2, figs. 17-19.

1984 Gnathodus girtyi simplex Dunn. Qiu, pi. 2,

figs. 15, 16. 

1985a Gnathodus girtyi simplex. Lane and others,

figs. 7A, B.

1985 Gnathodus girtyi rhodesi Higgins. Wardlaw, pi. 1, 

fig. 11.

1986 Gnathodus girtyi simplex Dunn. Ji, pi. 1, figs. 15-

17. 

1988 Gnathodus girtyi simplex Dunn. Dong and Ji, pi. 5,

figs. 1-3. 

1991 Gnathodus girtyi simplex Dunn. Higgins and others,

pi. 3, figs. 6, 12.

1991 Gnathodus girtyi simplex Dunn. Morrow and 

Webster, pi. 3, fig. 8.

1992 Gnathodus girtyi simplex Dunn. Morrow and 

Webster, pi. l,fig. 4.

1993 Gnathodus girtyi simplex Dunn. Dumoulin and 

Harris, fig. 8C.

Remarks.—Gnathodus girtyi simplex differs from G. 

g. girtyi by having an outer parapet consisting of one or two 

nodes that are restricted to the anterior half of the platform.

Specimens from the Wahoo Limestone below the 

Mississippian-Pennsylvanian boundary are transitional to 

Declinognathodus noduliferus japonicus (pi. 2, fig. 30) confirming Dunn's (1970b) concept of the phylogeny of D. 

noduliferus.

Distribution in the study section.—6 to 54.9 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone).

Known stratigraphic range.—Chesterian into 

nodulifems-primus Zone. Lane and others (1985a) and 

Baesemann and Lane (1985) reported Gnathodus girtyi simplex from about the basal 5 m of the Pennsylvanian in their 

Arrow Canyon section, Nevada. In the northeast Brooks 

Range, G. g. simplex occurs in two sections with or above 

Declinognathodus noduliferus, 1 km west of the study section (app. 1, Iocs. IBle, g) and at Pogopuk Creek, about 220 

m below the base of the Echooka Formation (app. 1, loc. 

5b).

Material.—72 Pa elements.

Gnathodus girtyi subspp. indet.

Remarks.—Included are chiefly broken, abraded, or 

juvenile Pa elements.

Distribution in the study section.—0.4 m above the 

base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone).

Known stratigraphic range.—upper Meramecian into 

lowermost Morrowan (into noduliferus-primus Zone).

Material.—54 Pa elements.

Gnathodus girtyi subspp. Hass transitional to 

Declinognathodus spp.

Plate 2, figures 29, 30

1985a Gnathodus girtyi simplex transitional to Declinognathodus noduliferus. Lane and others, fig. 1C.

Remarks.—An array of gnathodontid Pa element morphotypes that range from Gnathodus girtyi subspp. to Declinognathodus spp. appear close to the MississippianPennsylvanian boundary. These morphologic variations 

make taxonomic assignment uncertain. Pa elements transitional between G. g. simplex and D. n. japonicus (pi. 2, 

fig. 30) in the highest Mississippian samples (53 and 54.9 m 

above the base of the Wahoo Limestone and 2 and 0.1 m 

below the base of the Pennsylvanian) support the suggestion of Dunn (1970b) and Lane and Manger (1985) that 

G. g. simplex is the ancestor to D. noduliferus. These specimens are closer to G. g. simplex because the trough separating the inner parapet from the carina does not extend to the 

posterior tip of the platform, and the node(s) forming the 

outer parapet are not cleanly separated from the carina. 

These specimens do show, however, a slight depression 

between the inner parapet and carina near the posterior tip 

of the platform. A few specimens from 13 m above the 

Mississippian-Pennsylvanian boundary are transitional 

between G. g. girtyi and D. inaequalis (Higgins) (pi. 2, 

fig. 29).

Distribution in the study section.—53 to 69 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

lowermost Morrowan; Upper muricatus Subzone into 

noduliferus-primus Zone).

Material.—9 Pa elements.

Gnathodus spp. indet.

Plate 2, figure 28

Remarks.—Included are broken, abraded, or juvenile 

Pa elements and one vicarious M element.

Distribution in the study section.—0.4 to 53 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone).

Known stratigraphic range.—Mississippian to lowermost Pennsylvanian (upper Kinderhookian into lowermost 

Morrowan).

Material.—5 Pa and 1 M (pi. 2, fig. 28) elements.

Genus HINDEODUS Rexroad and Furnish, 1964

Type species.—Spathognathodus cristula Youngquist and

Miller, 1949 

p. 621, pi. 101, figs. 1-3

Remarks.—See discussion of genus in Sweet (1977).
SYSTEMATIC PALEONTOLOGY 43

Hindeodus minutus (Ellison, 1941)

Plate 1, figures 1-6

Only a selected synonymy, chiefly for Chesterian and 

Lower Pennsylvanian occurrences, is given for this 

long-ranging, widespread species. For occurrences to 1971, 

see Sweet (1973).

1941 Spathodus minutus Ellison, p. 120, pi. 20, figs. 50- 

52.

1964 Spathognathodus echigoensis Igo and Koike, p. 187, 

pi. 28, figs. 24?, 25?.

1965 Spathognathodus minutus (Ellison). Dunn, p. 1149,

pi. 140, figs. 15,21,24. 

1967 Spathognathodus minutus (Ellison). Koike, p. 311,

pi. 3, figs. 39-12. 

1969 Spathognathodus minutus (Ellison). Palmieri, p. 9,

10, pi. 5, figs. 17, 18. 

1973b Spathognathodus minutus (Ellison). Merrill, p. 305-

308, pi. 1, figs. 1-14; pi. 2, figs. 1-28.

1973 Anchignathodus minutus (Ellison). Sweet, p. 15-17, 

pi-1, fig. 2.

1974 Spathognathodus minutus (Ellison). Lane and

Straka, p. 101, figs. 44: 7, 12. 

1974 Anchignathodus minutus (Ellison). Merrill, pi. 2,

fig. 8. 

1980 Hindeodus ex. pr. H. minutus (Ellison). Bender,

p. 10, pi. 4, fig. 22.

1980 Anchignathodus minutus (Ellison). Tynan, p. 1300, 

pi. 2, figs. 8, 9.

1981 Hindeodus minutus (Ellison). Landing and Wardlaw,

p. 1259, 1260, pi. 1, figs. 11, 12, 18, 23?. 

1984 Hindeodus sp. Driese and others, pi. 1, fig. 4.

1984 Anchignathodus minutus (Ellison). Grayson, pi. 2,

figs. 3, 26. 

1985b Hindeodus minutus (Ellison). Grayson and others,

pi. 1, figs. 47,48.

1985 Hindeodus minutus (Ellison). Rexroad and Merrill,

pi. 3, figs. 21,22.

1985 Hindeodus sp. Sada and others, pi. 1, figs. 7-10. 

1985 Hindeodus minutus (Ellison). Savage and Barkeley,

p. 1472, figs. 12: 1-8.

1985 Hindeodus minutus (Ellison). Wardlaw, p. 400, pi. 3, 

% 1.

1986 Hindeodus minutus (Ellison). Mapes and Rexroad, 

pi. 1, figs. 7-15.

1987 Hindeodus minutus (Ellison). Grayson and others, 

pi. 9, fig. 1.

1989 Hindeodus minutus (Ellison). Wang and Higgins, p. 

279, pi. 13, figs. 6, 7.

1990 Hindeodus minutus (Ellison). Grayson, pi. 2, figs. 6, 

7,8?.

1991 Hindeodus minutus (Ellison). Brown and others, 

figs. 7: 12-19.

1992 Hindeodus minutus (Ellison). Sutherland and Grayson, pi. 2, fig. 1.

1992 Hindeodus minutus (Ellison). Weibel and Norby, 

pi. 1, fig. 21.

1993 Hindeodus minutus (Ellison). Lemos, p. 87, 88, 

pi. 4, figs. 1, 2; pi. 5, figs. 1, 2?, 3, 4 (fig. 3, Sb element; fig. 4, Sc element).

1993 Hindeodus minutus (Ellison). Rexroad, figs. 3: 14- 

17, 19.

Remarks.—All specimens of the apparatus of Hindeodus minutus in the collections from the Wahoo Limestone 

conform to the multielement reconstruction shown in 

Mapes and Rexroad (1986) and Brown and others (1991).

A Pa element figured by Rexroad and Horowitz (1990, 

pi. 1, fig. 42) as Hindeodus cristula (Youngquist and Miller) 

has the same anterior denticulation as H. minutus. We 

assume this morphotype is a rare component of the H. cristula population in the lower Chesterian and is appropriately 

assigned to H. cristula.

Distribution in the study section.—27 to 237 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

lower Atokan?; Upper muricatus Subzone to Idiognathodus 

Fauna).

Known stratigraphic range.—upper Chesterian (from 

within the Cavusgnathus monocerus Zone (= Adetognathus 

unicornis Zone)) through at least the Lower Permian.

Material—41 Pa, 10 Pb, 14 M, 3 Sa, 2 Sb, and 3 Sc 

elements.

Hindeodus spp. indet.

Remarks.—Included are broken or abraded Pa 

elements.

Distribution in the study section.—37? to 253 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

lower Atokan; Upper muricatus Subzone to Idiognathodus 

Fauna).

Known stratigraphic range.—Mississippian to lowermost Triassic (middle Kinderhookian to Dienerian).

Material.—14 Pa elements.

Genus IDIOGNATHODUS Gunnell, 1931

Type species.—Idiognathodus claviformis Gunnell, 1931

p. 249-250, pi. 29, figs. 21, 22 

Idiognathodus incurvus Dunn, 1966?

Plate 5, figure 21

For synonymy of the species through 1987, see Grayson 

and others (1990).

1989 Idiognathodus incurvus Dunn Complex. Grayson 

and others, p. 87, 88, pi. 1, figs. 21-25.

1990 Idiognathodus incurvus Dunn. Grayson, pi. 4, figs. 

4-7, 8?.

1990 Idiognathodus incurvus Dunn. Whiteside and Grayson, p. 159, pi. 1, figs. 15, 20-23, 34.

1992 Idiognathodus incurvus Dunn. Sutherland and Grayson, pi. 2, figs. 4, 12.
44 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

Remarks.—Grayson and others (1989) revised the 

diagnosis for Idiognathodus sinuosus, I. klapperi, and /. 

incurvus on the basis of the position of the adcarinal ridges 

and used this characteristic to establish a phylogeny. Idiognathodus sinuosus (originating in the middle Morrowan) 

has two adcarinal ridges, the inner of which extends slightly 

anterior of the platform and parallel to the free blade; /. 

klapperi (late Morrowan) has ridges that are restricted to the 

platform; and /. incurvus (Atokan) has ridges that extend 

anteriorly beyond the platform and intersect the free blade. 

The poor preservation and apparent low diversity of idiognathodids in the Wahoo Limestone do not allow us to test 

the evolutionary model proposed for the genus by Grayson 

and others (1989). Some specimens that Grayson and others 

(1990) and Sutherland and Grayson (1992, for example, pi. 

2, fig. 21) include in /. klapperi appear to be representatives 

of the /. sinuosus complex (/. delicatus morphotype). We 

did not recognize any specimens that we could confidently 

assign to /. klapperi.

Two specimens, 16 and 12 m below the top of the 

Wahoo Limestone, are questionably assigned to Idiognathodus incurvus. One is a juvenile and the other is a large adult. 

Although the latter is abraded, the adcarinal ridges extend 

beyond the anterior platform margin to intersect the remnant of the free blade (pi. 5, fig. 21).

Distribution in the study section.—246 to 250 m above 

the base of the Wahoo Limestone (lower Atokan; Idiognathodus Fauna). Idiognathodus incurvus! is used to indicate 

a level no older than Atokan at the study section on the 

basis of its distribution in the Atoka Formation in 

Oklahoma.

Known stratigraphic range.—From within the Atokan 

(probably lower Atokan) to lower Desmoinesian.

Material.—2 Pa elements.

Idiognathodus sinuosus Ellison and Graves, 1941

Plate 3, figures 15-18, 23-25

For synonymy through 1987, see Grayson and others 

(1990).

1990 Idiognathodus sinuosus Ellison and Graves. Grayson, pi. 4, figs. 36-39.

1992 Idiognathodus sinuosus Ellison and Graves. Sutherland and Grayson, pi. 2, figs. 28, 29. 

Remarks.—See remarks under Idiognathodus incurvus! for Grayson and others' (1989) concept of/, sinuosus. 

In addition, Grayson and others (1990) synonymize /. delicatus Gunnell and /. sinuosus', we follow their concept here. 

Many subadult and adult specimens included in Idiognathodus sinuosus have nodes on only one side of the platform 

but, uncharacteristic of/, sinuosus, have a relatively straight 

platform. One subadult specimen (pi. 3, fig. 23) has rostral 

ridges of equal length that extend slightly beyond the 

anterior end of the platform. This specimen is included in /. 

sinuosus and not in /. incurvus because similar size specimens of the latter exhibit rostral ridges characteristic of that 

species. Grayson (1990, pi. 4, figs. 37-39) includes similar 

forms in /. sinuosus.

Distribution in the study section.—187 to 243 m above 

the base of the Wahoo Limestone (upper Morrowan and (or) 

lower Atokan; Idiognathodus Fauna).

Known stratigraphic range.—upper Morrowan (sinuosus Zone) to at least Upper Pennsylvanian.

Material.—100 Pa elements.

Idiognathodus spp. indet.

Remarks.—Included are broken, abraded, or juvenile 

Pa elements.

Distribution in the study section.—111 to 257.5 m 

above the base of the Wahoo Limestone (upper Morrowan 

to lower Atokan; Idiognathodus Fauna).

Known stratigraphic range.—upper Morrowan (/. sinuosus Zone) to Lower Permian.

Material.—52 Pa elements.

Genus IDIOGNATHOIDES Harris and Boilings worth, 

1933

Type species.—Idiognathoides sinuata Harris and

Hollingsworth, 1933 

p. 201-202, pi. 1, fig. 14

Idiognathoides sinuatus Harris and Hollingsworth, "/. 

ouachitensis" morphotype

Plate 5, figure 22

For synonymy of Idiognathoides sinuatus to 1987, see

Grayson and others (1990).

1992 Idiognathoides sinuatus Harris and Hollingsworth.

Lemos, pi. 3, figs. 3, 8.

1992a Idiognathoides corrugatus (Harris and Hollingsworth). Nigmadganov and Nemirovskaya, pi. 5, 

figs. 6-11. 

1992a Idiognathoides sinuatus Harris and Hollingsworth.

Nigmadganov and Nemirovskaya, pi. 5, figs. 4, 5. 

Remarks.—Grayson (1984) indicated that the length of 

the trough of the dextral Pa element of Idiognathoides ouachitensis was diagnostic of this late Morrowan species. 

Moreover, he inferred a phylogenetic succession, on the 

basis of increasing trough length, from /. corrugatus to /. 

ouachitensis. Subsequently, Grayson (1990) and Grayson 

and others (1990) synonymized these species with the longranging /. sinuatus and speculated that the character of the 

trough was environmentally controlled. Wang and others 

(1987) synonymized /. ouachitensis in /. corrugatus but 

continued to recognize /. sinuatus as a separate species. We 

follow the multielement concept implemented by Grayson 

and others (1990) by including all three within /. sinuatus.

Only three specimens of the genus were recovered 

from the study section. All are from one sample and appear 

to have troughs characteristic of the "/. ouachitensis" mor-
SYSTEMATIC PALEONTOLOGY 45

photype. Because of their rarity, we cannot evaluate the 

environmental preference of these forms. Likewise, we cannot evaluate their biostratigraphic utility.

Distribution in the study section.—217.5 m above the 

base of the Wahoo Limestone (upper Morrowan or lower 

Atokan; Idiognathodus Fauna).

Known stratigraphic distribution.—lower Morrowan 

(sinuatus-minutus Zone) through at least Atokan.

Material.—3 Pa elements.

Genus 1DIOPRIONIODUS Gunnell, 1933

Type species.—Idioprioniodus typus Gunnell, 1933 

p. 265, pi. 31, fig. 47

Remarks.—For discussion of the genus see Stone 

(1991).

Idioprioniodus conjunctus (Gunnell, 1931)?

Plate 5, figures 11, 14-17

For synonymy to 1975, see Higgins (1975) and Higgins and

Wagner-Gentis(1982).

1982 Idioprioniodus conjunctus (Gunnell). Higgins and

Wagner-Gentis, p. 332, 333, pi. 34, figs. 18, 21, 23,

27-29. 

71985 Idioprioniodus cf. /. conjunctus (Gunnell). Rexroad

and Merrill, pi. 3, figs. 15?, 16-20; pi. 4, figs. 17-

19. 

1985 Idioprioniodus conjunctus (Gunnell). Savage and

Barkeley, p. 1459, figs. 5: 1-14. 

1987 Idioprioniodus conjunctus (Gunnell). Grayson and

others, pi. 2, figs. 1-6. 

1987 Idioprioniodus cf. conjunctus. Grayson and others,

pi. 5, 7-9; pi. 6, figs. 13-20.

1990 Idioprioniodus conjunctus (Gunnell). Grayson, 

pi. 2, figs. 15-24.

1991 Idioprioniodus conjunctus (Gunnell). Brown and

others, pi. 7, figs. 23-25, 26?, 27-29. 

1993 Idioprioniodus conjunctus (Gunnell). Rexroad, figs. 

4: 1?, 2-12, 13?, 14?.

Remarks.—Idioprioniodid elements are relatively rare 

in the Wahoo Limestone; all are incomplete. Elements 

approximate the better preserved material illustrated by 

Savage and Barkeley (1985, fig. 5). We have referred virtually all representatives of Idioprioniodus in the collections 

from the Wahoo Limestone to /. conjunctus?.

Distribution in the study section.—53 to 257.5 rn 

above the base of the Wahoo Limestone (uppermost Chesterian to lower Atokan; Upper muricatus Subzone to Idiognathodus Fauna).

Known stratigraphic range.—Within the Upper Mississippian to at least Desmoinesian.

Material.—6 Pb, 7 M, 5 Sa, 10 Sb, and 7 Sc elements.

Idioprioniodus cf. /. healdi (Roundy, 1926)?

Plate 5, figure 13

For synonymy to 1987, see Stone (1991).

Remarks.—Stone (1991) assigned many Mississippian 

representatives of Idioprioniodus to /. cf. I. healdi, including /. paraclaviger (Rexroad). One Pb? element from the 

Wahoo Limestone conforms to the Sbj element illustrated 

by Stone for /. cf. /. healdi (1991, pi. 5, fig. 5). This element, unlike similar elements of /. conjunctus, has a denticle immediately anterior to the cusp that is fused to it, at 

least near its base. Pb or Sb elements of forms we assign to 

/. conjunctus? do not have an anterior denticle fused to or 

impinging on the cusp.

Distribution in the study section.—207 m above the 

base of the Wahoo Limestone (Morrowan or lower Atokan; 

Idiognathodus Fauna).

Known stratigraphic range.—upper Osagean to at 

least Chesterian. The specimen from the Wahoo Limestone 

is from Pennsylvanian strata.

Material.—1 Pb? element.

Idioprioniodus spp. indet.

Plate 5, figure 12

Remarks.-—Broken and abraded robust digyrate elements, some of which are indeterminate to morphotype.

Distribution in the study section.—0.4 to 241 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

lower Atokan?; Upper muricatus Subzone to Idiognathodus 

Fauna).

Known stratigraphic range.—Lower Mississippian 

(upper Osagean) to at least Desmoinesian.

Material.—I Pa, 3 Pb, 8 M, 6 Sa, and 7 Sb elements 

and 9 elements indeterminate to morphotype.

Genus KLADOGNATHUS Rexroad, 1958

Type species.—Cladognathus prima Rexroad, 1957

p. 28, 29, pi. 1, figs. 8-10

Kladognathus spp.

Plate 5, figures 1-10

For synonymies of several species of Kladognathus, see 

Rexroad (1981) and Rexroad and Horowitz (1990).

Remarks.—Element notation for Kladognathus spp. 

follows that of Purnell (1993). Purnell's reconstruction is 

based on a well-preserved bedding-plane assemblage in the 

gut of a conodont predator. Except for some M elements, all 

kladognathid specimens from the Wahoo Limestone are 

incomplete. Thus, we could not distinguish Pa from Pb elements, and we have not attempted to identify the four morphotypes of the Sb-Sc transition series documented by 

Purnell (1993). The end members of the Sb-Sc transition 

series are illustrated (pi. 5, figs. 9, 10).
46 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

The lowest collection from the Wahoo Limestone contains the greatest number of kladognathids (table 1, USGS 

colln. 30745-PC). Most elements appear to be Kladognathus tenuis (Branson and Mehl) as reconstructed by 

Rexroad and Horowitz (1990).

Distribution in the study section.—0.4 to 54.9 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone). Specimens from 59 to 107 m 

above the base of the formation are considered redeposited.

Known stmtigraphic range.—upper Osagean to uppermost Chesterian.

Material.—68 P, 52 M, 6 Sa, and 115 Sb-Sc elements.

Genus LOCHRIEA Scott, 1942

Type species.—Spathognathodus commutatus Branson

and Mehl, 1941b

p. 98, pi. 19, figs. 1-4

Lochriea commutata (Branson and Mehl, 1941b)

Plate 3, figures 26, 27

For synonymy to 1987, see Rexroad and Horowitz (1990).

Additions and exceptions are noted below.

194la Spathognathodus commutatus Branson and Mehl,

p. 172, pi. V, figs. 19-22. 

1941b Spathognathodus commutatus Branson and Mehl,

p. 98, pi. 19, figs. 1-4. 

1969 Gnathodus commutatus (Branson and Mehl).

Thompson and Goebel, p. 23, 24, pi. 4, figs. 4, 6, 7. 

1979 Gnathodus commutatus (Branson and Mehl). Aisenverg and others, pi. 6, figs. 3, 4. 

1979 Gnathodus commutatus commutatus (Branson and

Mehl). Einor and others, pi. 14, figs. 2, 3.

1986 Paragnathodus commutatus (Branson and Mehl). Ji, 

pi. 2, figs. 1-4, 5?, 6.

1987 Lochriea commutata (Branson and Mehl). Armstrong and Purnell, pi. 3, fig. 1.

1987 Paragnathodus commutatus (Branson and Mehl). 

Riley and others, pi. 2, figs. 1, 3.

1987 Paragnathodus commutatus (Branson and Mehl). 

Wang and others, p. 130, 131, pi. 2, fig. 12.

1988 Gnathodus commutatus commutatus (Branson and 

Mehl). Dong and Ji, pi. 5, figs. 1-3.

1989 Paragnathodus commutatus (Branson and Mehl). 

Wang and Higgins, p. 285, pi. 8, figs. 4, 5.

1990 Lochriea commutata (Branson and Mehl). Grayson,

pi. l.figs. 14-24. 

1990a Lochriea commutata (Branson and Mehl). Ramovs,

p. 94, 95, pi. 4, figs. 6, 7, 10, 11. 

1990b Lochriea commutata (Branson and Mehl). Ramovs,

p. 110, pi. 1, figs. 6, 7, 9, 12-14. 

1990 Lochriea commutata (Branson and Mehl). Rexroad

and Horowitz, p. 508-510, pi. 2, figs. 10-24. 

1990 Lochriea commutata. Whiteside and Grayson, pi. 1,

figs. 1,2.

1991 Paragnathodus commutatus (Branson and Mehl). 

Nemirovskaya and others, pi. 3, fig. 4.

1991 Paragnathodus commutatus (Branson and Mehl).

Varker and others, pi. 1, figs. 13-15. 

?1992a Paragnathodus aff. commutatus (Branson and

Mehl). Nigmadganov and Nemirovskaya, pi. 1,

fig- 5.

1992 Lochriea commutata (Branson and Mehl). Weibel 

and Norby, pi. 2, figs. 35?, 36.

1993 Paragnathodus commutatus (Branson and Mehl). 

Alekseev and Kononova, pi. 29, fig. 11.

1994 Lochriea commutata (Branson and Mehl). KolarJurkovsek and Jurkovsek, 432-433, pi. 1, figs. 3, 4. 

1994 Lochriea commutata (Branson and Mehl).

Nemirovskaya and others, pi. 2, fig. 1. 

1994 Lochriea commutata (Branson and Mehl). von Bitter and Norby, p. 861-869, figs. 2-7. 

Remarks.—All Pa and M elements conform to those 

listed in the above synonymy.

Distribution in the study section.—0.4 to 54.9 m above 

the base of the Wahoo Limestone (uppermost Chesterian; 

Upper muricatus Subzone).

Known stratigraphic range.—lower Meramecian 

(lower Arundian in England according to Metcalfe, 1981) 

into the lowermost Morrowan (noduliferus Zone or earliest 

Bashkirian in the Donets basin, Ukraine (Nemirovskaya and 

others, 1991), and South Tienshan, Uzbekistan (Nigmadganov and Nemirovskaya, 1992a).

Material.—8 Pa and 2 M elements.

Genus NEOGNATHODUS Dunn, 1970b

Type species.—Polygnathus bassleri Harris and

Hollingsworth, 1933

p. 198,199, pi. 1, figs. 13a-e

Neognathodusl sp. indet.

Remarks.—A single posterior Pa element fragment is 

assigned to Neognathodusl sp. indet.

Distribution in the study section.—257.5 m above the 

base of the Wahoo Limestone (lower Atokan; Idiognathodus Fauna).

Known stratigraphic range.—Morrowan (N. symmetricus Zone) to Desmoinesian.

Material.—1 Pa element fragment.

Genus RHACHISTOGNATHUS Dunn, 1966

Type species.—Rhachistognathus prima Dunn, 1966

p. 1301,1302, pi. 157, figs. 1,2

Rhachistognathus minutus (Higgins and Bouckaert,

1968)

Remarks.—Baesemann and Lane (1985) recognized 

three subspecies of Rhachistognathus minutus—R. m. 

declinatus, R. m. havlenai, and R. m. minutus—on the basis 

of the position of the blade attachment and the degree of
SYSTEMATIC PALEONTOLOGY 47

curvature of the anterior part of the left platform margin. 

They reported (p. 107) that "All specimens in our collections are comparatively small." In contrast, adult to gerontic 

specimens from the Wahoo Limestone are quite large (some 

incomplete specimens are at least 1 mm long; pi. 4, figs. 5- 

8). Many specimens exhibit transitional subspecies characteristics so that subspecific assignment of such forms was 

arbitrary. In addition, some specimens of R. tn. minutus are 

similar to R. muricatus (pi. 4, fig. 15; Higgins, 1985, pi. 6.2, 

fig. 9). Regularly nodose specimens were cosmopolitan 

(R. m. minutus) and probably lived in relatively uniform, 

normal-marine shallow-water environments, whereas 

increasingly asymmetrical forms (R. muricatus to R. primus} occupied more variable shallow-water environments 

and were chiefly North American Cordilleran and southern 

Midcontinent inhabitants.

We are unable to evaluate the biostratigraphic utility, if 

any, of the subspecies of R. minutus from the Wahoo Limestone. All subspecies appear between 84 and 85 m above 

the base of the section and continue to near the top. We suppose that any paleoecologic partitioning of these subspecies 

was obliterated by hydraulic mixing across the Wahoo carbonate platform. The distribution of R. minutus subspp. in 

the Arrow Canyon section, Nevada (Baesemann and Lane, 

1985), is quite different from that of our section. At Arrow 

Canyon, R. m. minutus and R. m. havlenai make their 

appearance about 105 m below that of R. m. declinatus, 

co-occur for about 90 m, and disappear about 15 m below 

the first R. m. declinatus. R. m. declinatus continues as the 

only rhachistognathid in the succeeding 75 m. Unfortunately, Baesemann and Lane (1985) do not explain the 

stratigraphic succession of these subspecies nor the paleoenvironmental implications. Varker and others (1991) 

report all three subspecies together in several samples.

Rhachistognathus minutus declinatus Baesemann and 

Lane, 1985

Plate 4, figures 1-9

For synonymy through 1975, see Baesemann and Lane

(1985).

1985 Rhachistognathus minutus declinatus Baesemann

and Lane, p. 108, 109, pi. 1, figs. 1-10. 

1987 Rhachistognathus minutus declinatus Baesemann

and Lane. Nemirovskaya, pi. 1, figs. 1, 4. 

1987 Rhachistognathus minutus declinatus Baesemann

and Lane. Riley and others, pi. 3, figs. 10?, 11. 

1991 IRhachistognathus minutus declinatus Baesemann

and Lane. Nemirovskaya and others, pi. 4, figs. 1, 2. 

1991 Rhachistognathus minutus declinatus Baesemann

and Lane. Varker and others, pi. 1, figs. 30, 31.

Remarks.—Rhachistognathus minutus declinatus is

the most abundant rhachistognathid in the Wahoo

Limestone. One sample from the upper member yielded 276

Pa elements of R. m. declinatus; some specimens are transitional to R. m. havlenai (table 1, USGS colln. 30786-PC). 

The free blade joins the platform subcentrally and, with few 

exceptions, the anterior end of the left parapet is deflected 

to the left. A few gerontic specimens have the anterior end 

of the right parapet deflected to the right (pi. 4, fig. 6). The 

inner platform margin of some gerontic Pa elements have 

one or two nodes (pi. 4, figs. 7, 8); a transverse ridge may 

extend from the node(s) to the parapet (pi. 4, fig. 7).

A form geometrically similar to R. m. declinatus was 

described from Lower and Middle Pennsylvanian rocks in 

southeast Alaska by Savage and Barkeley (1985). The platform margin of their species, "Taphrognathus alaskensis" 

however, is ornamented by closely spaced, delicate transverse ridges, whereas R. m. declinatus has noded or transversely ridged and noded parapets. The new species may 

represent a part of the R. minutus plexus that occupied 

quiet, open-marine environments.

Distribution in the study section.—85 to 261.5 m 

above the base of the Wahoo Limestone (lower Morrowan 

to lower Atokan; lower minutus Fauna to Idiognathodus 

Fauna).

Known stratigraphic range.—lower Morrowan (base 

of sinuatus-minutus Zone in North America, but below the 

mid-Carboniferous boundary and within the lowermost 

Chokierian in England; Varker and others, 1991) to lower 

Atokan.

Material.—518 Pa elements.

Rhachistognathus minutus havlenai Baesemann and 

Lane, 1985

Plate 4, figures 10-12

For synonymy through 1975, see Baesemann and Lane

(1985). Additions and exceptions are noted below.

1969 Streptognathodus lanceolatus Webster, p. 47, 48,

pi. 6, fig. 14 (only). 

1985 Rhachistognathus minutus havlenai Baesemann

and Lane, p. 109-111, pi. 2, figs. 1-6, 8, 9. 

1987 Rhachistognathus minutus havlenai Baesemann

and Lane. Riley and others, pi. 3, figs. 8, 9. 

1991 Rhachistognathus minutus havlenai Baesemann

and Lane. Varker and others, pi. 1, figs. 26-29. 

Remarks.—According to Baesemann and Lane (1985), 

the offset of the free blade from the left parapet distinguishes Rhachistognathus minutus havlenai from R. m. 

minutus and R. muricatus. The anterior margin of the left 

parapet in R. m. havlenai is straight as opposed to R. m. declinatus in which it curves strongly outward (compare pi. 4, 

figs. 1, 10).

Distribution in the study section.—85 to 261.5 m 

above the base of the Wahoo Limestone (lower Morrowan 

to lower Atokan; lower minutus Fauna to Idiognathodus 

Fauna).

Known stratigraphic range.—lower Morrowan (base 

of sinuatus-minutus Zone in North America, but below the
48 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

mid-Carboniferous boundary and within the lowermost 

Chokierian in England; Varker and others, 1991) to lower 

Atokan.

Material.—228 Pa elements.

Rhachistognathus minutus minutus (Higgins and 

Bouckaert, 1968)

Plate 4, figures 13-15

For synonymy through 1975, see Baesemann and Lane

(1985). Additions and exceptions are noted below.

1969 Streptognathodus lanceolatus Webster, p. 47, 48,

pi. 6, fig. 15 (only). 

1985 Rhachistognathus minutus minutus (Higgins and

Bouckaert). Baesemann and Lane, p. Ill, 112, pi. 2,

figs. 7, 10, 11; pi. 3, figs. 1-12. 

1985 Rhachistognathus minutus (Higgins and Bouckaert).

Higgins, p. 220, pi. 6.2, figs. 3-9. 

71985 Rhachistognathus minutus n. subsp. C. Skipp and

others, pi. 8, fig. 5. 

1987 Rhachistognathus minutus minutus (Higgins and

Bouckaert). Riley and others, pi. 3, figs. 1-7. 

1991 Rhachistognathus minutus minutus (Higgins and

Bouckaert). Varker and others, pi. 1, figs. 16?, 17?,

20-22, 25.

Remarks.—Specimens from the Wahoo Limestone 

assigned to this subspecies conform to the diagnosis and 

description given in Baesemann and Lane (1985). Also see 

remarks above for Rhachistognathus minutus.

Distribution in the study section.—84 to 260.5 m 

above the base of the Wahoo Limestone (lower Morrowan 

to lower Atokan; lower minutus Fauna to Idiognathodus 

Fauna).

Known stratigraphic range.—lower Morrowan (base 

of sinuatus-minutus Zone in North America, but below the 

mid-Carboniferous boundary and within the lowermost 

Chokierian in England; Varker and others, 1991) to lower 

Atokan.

Material.—300 Pa elements.

Rhachistognathus minutus subspp. indet.

Remarks.—Included are broken, abraded, or juvenile 

Pa elements.

Distribution in the study section.— 107 to 261.5 m 

above the base of the Wahoo Limestone (Morrowan to 

lower Atokan; lower minutus Fauna to Idiognathodus 

Fauna).

Known stratigraphic range.—lower Morrowan (base 

of sinuatus-minutus Zone in North America, but below the 

mid-Carboniferous boundary and within the lowermost 

Chokierian in England; Varker and others, 1991) to lower 

Atokan.

Material.—33 Pa elements.

Rhachistognathus muricatus (Dunn, 1965)

Plate 4, figures 27-30

For synonymy through 1980, see Baesemann and Lane

(1985). Additions and exceptions are noted below.

?1966 Cavusgnathus transitoria Dunn, p. 1299, pi. 157,

fig. 9. 

1985 Rhachistognathus minutus minutus (Higgins and

Bouckaert). Baesemann and Lane, pi. 2, figs. 7, 10

(only).

1985 Rhachistognathus muricatus (Dunn). Skipp and others, pi. 8, fig. 9. 

1985 Rhachistognathus muricatus (Dunn). Wardlaw,

pi. l,fig. 9. 

1987 Rhachistognathus muricatus (Dunn). Grayson and

others, pi. 4, figs. 23, 30?, 32, 38. 

?1987 Rhachistognathus aff. muricatus (Dunn). Wang and

others, p. 131, 132, pi. 7, figs. 5, 6. 

1991 Rhachistognathus muricatus (Dunn). Higgins and

others, pi. 3, figs. 8, 13.

1991 Rhachistognathus muricatus (Dunn). Morrow and 

Webster, pi. 4, figs. 1-5.

1992 Rhachistognathus muricatus (Dunn). Morrow and 

Webster, pi. 1, fig. 6.

1993 Rhachistognathus muricatus (Dunn). Lemos, p. 88, 

90, pi. 4, figs. 3, 4, 5?.

Remarks.—This species is the most morphologically 

variable rhachistognathid and is intermediate between 

Rhachistognathus minutus and R. primus. Many specimens 

in the collections from the Wahoo Limestone conform to the 

species diagnosis, whereas others are transitional to 

R. minutus, R. primus, or R. websteri. Transition forms are 

discussed below.

Distribution in the study section.—6 to 133.5 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

Morrowan; Upper muricatus Subzone to lower minutus 

Fauna).

Known stratigraphic range.—uppermost Chesterian 

(base of muricatus Zone) to lower Atokan.

Material.—336 Pa elements.

Rhachistognathus muricatus (Dunn) transitional to 

R. primus Dunn

Plate 4, figure 25

1974 Rhachistognathus muricatus (Dunn). Lane and

Straka, p. 97, 98, figs. 35: 16, 17. 

1985 Rhachistognathus muricatus (Dunn) transitional to

R. primus Dunn. Baesemann and Lane, p. 115, pi. 4,

figs. 8, 9. 

1987 Rhachistognathus minutus (Higgins and Bouckaert).

Grayson and others, pi. 4, fig. 31. 

1991 Rhachistognathus minutus havlenai Baesemann

and Lane. Higgins and others, pi. 3, figs. 7, 11.
SYSTEMATIC PALEONTOLOGY 49

Remarks.-—The absence of a narrow, medial trough 

distinguishes R. primus from R. muricatus. Specimens considered transitional between R. muricatus and R. primus 

have a moderate trough on the anterior half of the platform 

and a shallow trough containing a row of low nodes on the 

posterior half.

Distribution in the study section.—85 to 95 m above 

the base of the Wahoo Limestone (Morrowan; lower minutus Fauna).

Material.—4 Pa elements.

Rhachistognathus muricatus (Dunn) transitional to 

R. websteri Baesemann and Lane

Plate 4, figure 16

Remarks.—Rhachistognathus websteri is distinguished from other rhachistognathids by a prominent marginal node that is distinctly offset from the posterior part of 

the outer parapet. This node is only slightly offset in the figured specimen.

Distribution in the study section.—6 m above the base 

of the Wahoo Limestone (uppermost Chesterian; Upper 

muricatus Subzone).

Material.—1 Pa element.

Rhachistognathus prolixus Baesemann and Lane, 1985?

Remarks.—Two posterior platform fragments resemble Rhachistognathus prolixus but are too incomplete for 

positive identification.

Distribution in the study section.—6 to 157 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

Morrowan; Upper muricatus Subzone to lower minutus 

Fauna).

Known stratigraphic range.—lower Chesterian to 

middle Morrowan.

Material.—3 Pa element fragments.

Rhachistognathus websteri Baesemann and Lane, 1985

Plate 4, figures 17-21

For synonymy through 1980, see Baesemann and Lane

(1985).

1983 Rhachistognathus primus Dunn. Metcalfe, pi. 2,

fig. 18. 

1985 Rhachistognathus websteri Baesemann and Lane,

p. 117-119, pi. 5, figs. 1,2,8-12. 

1985 Rhachistognathus muricatus (Durm)-Rhachistognathus primus Dunn plexus. Plafker and others,

figs. 48C, D. 

71985 Rhachistognathus minutus (Higgins and Bouckaert).

Wardlaw, pi. 1, fig. 7. 

1991 Rhachistognathus muricatus (Dunn). Higgins and

others, pi. 3, fig. 13.

1991 Rhachistognathus websteri Baesemann and Lane. 

Higgins and others, pi. 3, fig. 17.

1991 Rhachistognathus websteri Baesemann and Lane. 

Morrow and Webster, pi. 3, figs. 14, 15.

1992 Rhachistognathus websteri Baesemann and Lane.

Morrow and Webster, pi. 1, fig. 8.

1992 Rhachistognathus cf. R. websteri Baesemann and 

Lane. Weibel and Norby, pi. 2, fig. 37.

Remarks.—The morphology of Pa elements agrees 

with those synonymized above; most specimens are relatively small. Rhachistognathus websteri may be an ecophenotype of R. muricatus. Collections containing abundant R. 

muricatus generally contain relatively abundant R. websteri 

and visa versa (compare table 1, USGS collns. 30770-PC 

and 30773-PC). The same relationships persist in the northeast Brooks Range (app. 1, loc. 5d).

Distribution in the study section.—59 to 162 m above 

the base of the Wahoo Limestone (lowermost Morrowan; 

noduliferus-primus Zone to lower minutus Fauna).

Known stratigraphic range.—uppermost Chesterian 

(Upper muricatus Subzone; app. 1, loc. 4Alc) to lower and 

possibly middle Morrowan (this report).

Material.—187 Pa elements.

Rhachistognathus spp. indet.

Plate 4, figures 22-24

Remarks.—Included are broken, abraded, or juvenile 

(pi. 4, figs. 22-24) nodose Pa elements, chiefly posterior 

platform fragments.

Distribution in the study section.—6 to 260.5 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

lower Atokan; Upper muricatus Subzone to Idiognathodus 

Fauna).

Known stratigraphic range.—at least lower Chesterian 

to lower Atokan.

Material.—396 Pa elements.

Genus VOGELGNATHUS Norby and Rexroad, 1985

Type species.—Spathognathodus campbelli Rexroad,

1957

p. 37, 38, pi. 3, figs. 13-15 

Vogelgnathus postcampbelli (Austin and Husri, 1974)

Plate 3, figures 28-31

For synonymy to 1985, see Purnell and von Bitter (1992).

Additions and exceptions are listed below.

1967 Spathognathodus campbelli Rexroad. Koike, p. 310,

pi. 3, figs. 26, 27, 29, 32?. 

1974 Spathognathodus campbelli Austin and Husri, p. 57,

pi. 5, figs. 1,3,4. 

1985 Vogelgnathus n. sp. Norby and Rexroad, p. 11, 12,

pi. 1, figs. 3-5.
50 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

1985 Ozarkodina sp. (Spathognathodus campbelli

Rexroad). Sada and others, pi. 1, fig. 27 (only). 

1992 Vogelgnathus postcampbelli (Austin and Husri). 

Purnell and von Bitter, p. 327, 328, figs. 13: 1-4, 

fig. 14 (part).

1992 Vogelgnathus n. sp. of Norby and Rexroad. Weibel 

and Norby, pi. 1, fig. 23.

Remarks.—Purnell and von Bitter (1992, their table 1) 

summarize the characteristics of species of Vogelgnathus 

spp. Specimens of V postcampbelli from the Wahoo Limestone are poorly preserved Pa elements having 10 to 14 denticles. The upper margin profile of most specimens 

gradually increases in height posteriorly toward the cusp 

and then sharply decreases from the cusp to the posterior tip 

(pi. 3, figs. 28, 30). Some specimens have a cusp that is 

slightly higher and wider than adjacent denticles.

Vogelgnathus postcampbelli is locally common to 

abundant in beds above and below the MississippianPennsylvanian boundary in the northeast Brooks Range (for 

example, app. 1, loc. 7a, 50 km southwest of the study section in the Fourth Range, 20 m below the MississippianPennsylvanian boundary; app. 1, loc. IBlg, 1 km west of 

the study section—53 Pa elements from 2.8 m above the 

boundary, pi. 3, fig. 31). All specimens are nearly identical 

to and some are even more poorly preserved than those 

from the study section.

Distribution in the study section.—0.4 to 76.5 m above 

the base of the Wahoo Limestone (uppermost Chesterian to 

lower Morrowan; Upper muricatus Subzone to noduliferusprinius Zone).

Known stratigraphic range.—At least Chesterian into 

the lowermost Morrowan (no younger than noduliferusprimus Zone).

Material.— 16 Pa elements.

REFERENCES CITED

Aisenverg, D.E., and others, 1979, The Serpukhovian Stage of the 

Lower Carboniferous of the U.S.S.R., in Wagner, R.H., Higgins, A.C., and Meyen, S.V., eds.. The Carboniferous of the 

U.S.S.R.: Yorkshire Geological Society Occasional Publication No. 4, p. 43-59.

Alekseev, A.S., and Kononova, L.I., 1993, Conodonts, in 

Tikhomirov, S.V., ed.. Lower Carboniferous of the Moscow 

syneclise and the Voronezh anteclise: Moscow Society of 

Naturalists, Committee on Geology and Subsurface Exploration, Russian Academy of Sciences, p. 130-134 and 188-191, 

pis. 25-29.

Armstrong, A.K., 1972, Pennsylvanian carbonates, paleoecology, 

and rugose colonial corals, north flank, eastern Brooks 

Range, arctic Alaska: U.S. Geological Survey Professional 

Paper 747, 21 p.

————1974. Carboniferous carbonate depositional models, preliminary lithofacies and paleotectonic maps, Arctic Alaska: 

American Association of Petroleum Geologists Bulletin, v. 

58, p. 621-645.

Armstrong, A.K., and Mamet, B.L., 1974, Carboniferous biostratigraphy, Prudhoe State 1 to northeast Brooks Range, Arctic Alaska: American Association of Petroleum Geologists 

Bulletin, v. 58, p. 646-660.

————1975, Carboniferous biostratigraphy, northeastern Brooks 

Range, arctic Alaska: U.S. Geological Survey Professional 

Paper 884, 29 p.

————1977, Carboniferous microfacies, microfossils, and corals, 

Lisburne Group, arctic Alaska: U.S. Geological Survey Professional Paper 849, 144 p.

————1978, Microfacies of the Carboniferous Lisburne Group.

Endicott Mountains, Arctic Alaska, in Stelck, C.R.. and 

Chatterton, B.D.E., eds.. Western and Arctic Canadian biostratigraphy: Geological Association of Canada Special Paper 

18, p. 333-394.

Armstrong, A.K., Mamet, B.L., and Dutro, J.T.. Jr., 1970, Foraminiferal zonation and carbonate facies of Carboniferous 

(Mississippian and Pennsylvanian) Lisburne Group, central 

and eastern Brooks Range, Arctic Alaska: American Association of Petroleum Geologists Bulletin, v. 54, no. 5, p. 687- 

698.

Armstrong, H.A., and Purnell, M.A., 1987, Dinantian conodont 

biostratigraphy of the Northumberland trough: Journal of 

Micropalaeontology, v. 6, no. 2, p. 97-112.

Austin, R.L., 1972, Problems of conodont taxonomy with special 

reference to Upper Carboniferous forms: Geologica et Palaeontologica, no. 1, p. 115-126.

Austin, R.L., and Aldridge, R.J., 1973, Conodonts from horizons 

with Goniatites crenistria Phillips in North Wales and the Isle 

of Man: Geological Magazine, v. 110, no. 1, p. 37^2.

Austin, R.L., Conil, Raphael, Groessens, Eric, and Pirlet, H., 1974, 

Etude biostratigraphique de Tencrinite de Tramaka: Bulletin 

Societe Beige de Geologic, de Paleontologie, et Hydrologie, 

v. 83, p. 113-129.

Austin, R.L., and Husri, S., 1974, Dinantian conodont faunas from 

County Clare, County Limerick, and County Leitrim. An 

appendix, in Bouckaert, Jos, and Streel, Maurice, eds., International symposium on Belgian micropalaeontological limits: 

Geological Survey of Belgium, Publication 3, p. 18-69.

Bader, J.W., and Bird, K.J., 1986, Geologic map of Demarcation 

Point, Mt. Michelson, Flaxman Island, and Barter Island 

quadrangles, Alaska: U.S. Geological Survey Miscellaneous 

Investigations Map 1-1791, scale 1:250,000, 1 sheet.

Baesemann, J.F., 1973, Missourian (Upper Pennsylvanian) conodonts of northeastern Kansas: Journal of Paleontology; v. 47. 

no. 4, p. 689-710.

Baesemann, J.F., and Lane, H.R., 1985, Taxonomy of the genus 

Rhachistognathus Dunn (Conodonta: Late Mississippian to 

Early Pennsylvanian), in Lane, H.R., and Ziegler, Willi, eds., 

Toward a boundary in the middle of the Carboniferous: 

Stratigraphy and paleontology: Courier Forschungsinstitut 

Senckenberg, no. 74, p. 93-135.

Bender, K.P, 1980, Lower and Middle Pennsylvanian conodonts 

from the Canadian Archipelago: Geological Survey of Canada Paper 79-15, 27 p.

Bird, K.J.. and Magoon, L.B., eds., 1987, Petroleum geology of 

the northern part of the Arctic National Wildlife Refuge, 

northeastern Alaska: U.S. Geological Survey Bulletin 1778. 

329 p.
REFERENCES CITED 51

Bird, K.J., and Molenaar, CM, 1987, Stratigraphy, in Bird, K.J., 

and Magoon, L.B., eds., Petroleum geology of the northern 

part of the Arctic National Wildlife Refuge, northeastern 

Alaska: U.S. Geological Survey Bulletin 1778, p. 37-59.

Bischoff, Giinther, 1957, Die Conodonten-Stratigraphie des rhenoherzynischen Unterkarbons mit Beriicksichtigung der 

Wocklumeria-Stufe und der Devon/Karbon-Grenze: Abhandlungen Hessisches Landesamt fur Bodenforschung, v. 19, 

64 p.

Boogaard, Marienus van den, 1983, On some occurrences of Diplognathodus in Carboniferous strata of Western Europe and 

North Africa: Scripta Geologica, v. 69, p. 19-29.

Boogaard, Marienus van den, and Bless, M.J.M., 1985, Some conodont faunas from the Aegiranum Marine Band: Palaeontology. Proceedings, Series B, v. 88, no. 2, p. 133-154.

Bowsher. A.L., and Dutro, J.T., Jr., 1957, The Paleozoic section in 

the Shainin Lake area, central Brooks Range: U.S. Geological 

Survey Professional Paper 303-A, 39 p.

Branson, E.B., and Mehl, M.G., 1941a, Caney conodonts of Upper 

Mississippian age: Denison University Bulletin, Journal of 

the Scientific Laboratories, v. 35, p. 167-178.

————1941b, New and little known Carboniferous conodont genera: Journal of Paleontology, v. 15, no. 2, p. 97-106.

Brenckle, PL, Groves, J.R., and Skipp, Betty, 1982, A 

Mississippian-Pennsylvanian (mid-Carboniferous) boundary 

in North America based on calcareous Foraminifera, in 

Ramsbottom, W.H.C., Saunders, W.B., and Owens, Bernard, 

eds., Biostratigraphic data for a mid-Carboniferous boundary: 

Leeds, England, Subcommission on Carboniferous Stratigraphy, p. 42-51.

Brenckle, PL., Lane, H.R., Manger, W.L., and Saunders, W.B., 

1977, The Mississippian-Pennsylvanian boundary as an intercontinental biostratigraphic datum: Newsletters on Stratigraphy, v. 6, p. 106-116.

Brenckle, PL., and Manger, W.L., eds., 1990, Intercontinental correlation and division of the Carboniferous System: Courier 

Forschungsinstitut Senckenberg, no. 130, 350 p.

Brosge, W.P., Dutro, J.T., Jr., Mangus, M.D., and Reiser, H.N., 

1962, Paleozoic sequence in eastern Brooks Range, Alaska: 

Bulletin of the American Association of Petroleum Geologists, v. 46, no. 12, p. 2174-2198.

Brown, L.M., Rexroad, C.B., Beard, John, and Williams, David,

1990. Phylogenetic and zonal implications of Cavusgnathus 

tytthus n. sp. (Conodonta) from the Kinkaid Limestone 

(Upper Mississippian) of western Kentucky, U.S.A.: Geologica et Palaeontologica, no. 24, p. 77-87. 

Brown, L.M., Rexroad, C.B., Eggert, D.L., and Horowitz, A.S.,

1991. Conodont paleontology of the Providence Limestone 

Member of the Dugger Formation (Pennsylvanian, Desmoinesian) in the southern part of the Illinois basin: Journal 

of Paleontology, v. 65, no. 6, p. 945-957.

Carlson, R.C., 1987, Depositional environments, cyclicity, and 

diagenetic history of the Wahoo Limestone, eastern Sadlerochit Mountains, northeastern Alaska: Fairbanks, Alaska, University of Alaska Fairbanks, M.S. thesis, 189 p.

————1990, Cement stratigraphy in the Wahoo Formation, Sadlerochit Mountains, Alaska [abs.]: American Association of 

Petroleum Geologists Bulletin, v. 74, no. 5, p. 625.

Chaplin, J.R., 1979, Conodont biostratigraphy of Lower Carboniferous strata in the southern Appalachians, in Sutherland, P.K.,

and Manger, W.L., eds., Neuvieme Congres International de 

Stratigraphie et de Geologic de Carbonifere: Carbondale, 

Southern Illinois University Press, p. 265-281.

Clarke, W.J., 1960, Scottish Carboniferous conodonts: Transactions of the Edinburgh Geological Society, v. 18, pt. I, 31 p.

Clough, J.G., and Bakke, A.A., 1986, Measured Stratigraphie section of the Lisburne Group Limestone (85LSB), western 

Sadlerochit Mountains, Mt. Michelson C-3 quadrangle, 

Alaska: Alaska Geological & Geophysical Surveys, Public 

Data File Report 86-86h, 8 p.

Craig, J.D., Sherwood, K.W, and Johnson, P.P., 1985, Geologic 

report for the Beaufort planning area, Alaska—Regional 

geology, petroleum geology, environmental geology: U.S. 

Department of Interior Minerals Management Service, O.C.S. 

Report, MMS 85-0111, 191 p.

Crowder, R.K., 1990, Permian and Triassic sedimentation in the 

northeastern Brooks Range, Alaska: Deposition of the Sadlerochit Group: American Association of Petroleum Geologists 

Bulletin, v. 74, no. 9, p. 1351-1370.

Davis, L.E., and Webster, G.D., 1985, Late Mississippian to Early 

Pennsylvanian conodont biofacies in central Montana: 

Lethaia, v. 18, p. 67-72.

Dong, Zhizhong, and Ji, Qiang, 1988, Carboniferous conodont 

biostratigraphy of Ninglang-Lijiang area, Yunnan Province: 

Professional Papers of Stratigraphy and Palaeontology, 

no. 22, p. 35-65.

Driese, S.G., Carr, T.R., and Clark, D.L., 1984, Quantitative analysis of Pennsylvanian shallow-water conodont biofacies, Utah 

and Colorado, in Clark, D.L., ed., Conodont biofacies and 

provincialism: Geological Society of America Special Paper 

196, p. 233-250.

Duan, Jin-ying, 1993, Carboniferous conodonts from Binhai and 

Baoying, northern Jiangsu: Acta Micropalaeontologica 

Sinica, v. 10, no. 2, p. 201-212.

Dumoulin, J.A., and Harris, A.G., 1993, Lithofacies and conodonts of Carboniferous strata in the Ivotuk Hills, western 

Brooks Range, Alaska, in Dusel-Bacon, Cynthia, and Till, 

A.B., eds., Geologic studies in Alaska by the U.S. Geological 

Survey, 1992: U.S. Geological Survey Bulletin 2068, p. SI47.

Dunham, R.J., 1962, Classification of carbonate rocks according 

to texture, in Ham, W.E., ed., Classification of carbonate 

rocks: American Association of Petroleum Geologists Memoir no. l,p. 108-121.

Dunn, D.L., 1965, Late Mississippian conodonts from the Bird 

Spring Formation in Nevada: Journal of Paleontology, v. 39, 

no. 6, p. 1145-1150.

————1966, New Pennsylvanian platform conodonts from southwestern United States: Journal of Paleontology, v. 40, no. 6, 

p. 1294-1303.

————I970a, Conodont zonation near the MississippianPennsylvanian boundary in western United States: Geological Society of America Bulletin, v. 81, p. 2959-2974.

————1970b, Middle Carboniferous conodonts from the western

United States and phylogeny of the platform group: Journal 

of Paleontology, v. 44, no. 2, p. 312-342.

Dutro, J.T., Jr., 1987, Revised biostratigraphic zonation for the 

Carboniferous of northern Alaska, in Tailleur, I.L., and 

Weimer, Paul, eds., Alaskan North Slope geology: Bakersfield, California, Pacific Section Society of Economic Pale-
52 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

ontologists and Mineralogists and the Alaska Geological 

Society, v. l,p. 359-364.

Eckstein, M.K., 1993, Lateral facies changes in the Carboniferous 

Lisburne Group along the Aichilik transect, northeastern 

Alaska: Alaska Geological & Geophysical Surveys, Public 

Data File Report 93-42, 18 p.

Einor, O.L., and others, 1979, The Lower-Middle Carboniferous 

boundary, in Wagner, R.H., Higgins, A.C., and Meyen, S.V., 

eds., The Carboniferous of the U.S.S.R.: Yorkshire Geological Society Occasional Publication No. 4, p. 61-81.

Elias, M.K., 1956, Upper Mississippian and Lower Pennsylvanian 

formations of south-central Oklahoma: Bulletin of the American Association of Petroleum Geologists, v. 40, no. 10, p. 56- 

134.

Ellison, S.P, 1941, Revision of the Pennsylvanian conodonts: 

Journal of Paleontology, v. 15, no. 2, p. 107-143.

Ellison, S.P, and Graves, R.W, 1941, Lower Pennsylvanian (Dimple Limestone) conodonts of the Marathon region, Texas: 

University of Missouri School of Mines and Metallurgy Bulletin, v. 14, no. 3, 21 p.

Ellison, S.P, and Powell, J.D., 1989, Tesnus (Mississippian) conodonts, Brewster County, Texas, in Ziegler, Willi, ed.. Papers 

on Ordovician to Triassic conodonts; 1st International Senckenberg Conference and 5th European Conodont Symposium 

(ECOS V) Contributions III: Courier Forschungsinstitut 

Senckenberg, no. 117, p. 359-373.

Epstein, A.G., Epstein, J.B., and Harris, L.D., 1977, Conodont 

color alteration—An index to organic metamorphism: U.S. 

Geological Survey Professional Paper 995, 27 p.

Gibshman, N.B., and Akhmetshina, L.Z., 1991, Micropaleontologic basis for determination of the mid-Carboniferous 

boundary in the north Caspian syneclise, U.S.S.R., in 

Brenckle, PL., and Manger, W.L., eds., Intercontinental correlation and division of the Carboniferous System: Courier 

Forschungsinstitut Senckenberg, no. 130, p. 273-295.

Globensky, Yvon, 1967, Middle and Upper Mississippian conodonts from the Windsor Group of the Atlantic provinces of 

Canada: Journal of Paleontology, v. 41, no. 2, p. 432-448.

Grantz, Arthur, and May, S.D., 1983, Rifting history and structural 

development of the continental margin north of Alaska, in 

Watkins, J.S., and Drake, C.L., eds., Studies in continental 

margin geology: American Association of Petroleum Geologists, Memoir 34, p. 77-100.

Grantz, Arthur, Johnson, Leonard, and Sweeny, J.F., eds., 1990, 

The geology of North America, v. L, the Arctic Ocean region: 

Boulder, Colorado, Geological Society of America, 644 p.

Grayson, R.C., Jr., 1984, Morrowan and Atokan (Pennsylvanian) 

conodonts from the northeastern margin of the Arbuckle 

Mountains, southern Oklahoma: Oklahoma Geological Survey Bulletin 136, p. 41-63.

————1990, Canyon Creek: A significant exposure of a predominantly mudrock succession recording essentially continuous 

deposition from the Late Devonian through the Middle 

Pennsylvanian, in Ritter, S.M., ed., Early to Middle Paleozoic conodont biostratigraphy of the Arbuckle Mountains, 

southern Oklahoma: Oklahoma Geological Survey, Guidebook 27, p. 85-105.

Grayson, R.C., Jr., Davidson, W.T., Westergaard, E.H., Atchley, 

S.C., Hightower, J.H., Monaghan, P.T., and Pollard, C.D., 

1985a, Mississippian-Pennsylvanian (mid-Carboniferous)

boundary conodonts from the Rhoda Creek Formation: 

Homoceras equivalent in North America, in Lane, H.R., and 

Ziegler, Willi, eds., Toward a boundary in the middle of the 

Carboniferous: Stratigraphy and paleontology: Courier Forschungsinstitut Senckenberg, no. 74, p. 149-180. 

Grayson, R.C., Jr., Merrill, G.K., and Lambert, L.L., 1989, Phylogenetic basis for species recognition within the conodont 

genus Idiognathodus'. Applicability to correlation and boundary placement, in Boardman, D.R., II, and others, eds., Middle and Late Pennsylvanian chronostratigraphic boundaries in 

north-central Texas: Glacial-eustatic events, biostratigraphy, 

and paleoecology: Lubbock, Texas, Texas Tech University 

Studies in Geology 2, p. 75-94.

————1990, Carboniferous gnathodontid conodont apparatuses: 

Evidence of a dual origin for Pennsylvanian taxa, in Ziegler, 

Willi, ed.. Papers on conodonts and Ordovician to Triassic 

conodont stratigraphy; 1st International Senckenberg Conference and 5th European Conodont Symposium (ECOS V) 

Contributions IV: Courier Forschungsinstitut Senckenberg, 

no. 118, p. 353-396.

Grayson, R.C., Jr., Merrill, G.K., and Miller, J.F., eds., 1987, Early 

and late Paleozoic conodont faunas of the Llano uplift region, 

central Texas—Biostratigraphy, systemic boundary relationships, and stratigraphic importance, Guidebook for Field Trip 

1, Geological Society of America South-Central Section 

Meeting: Waco, Texas, Baylor University, 153 p.

Grayson, R.C., Jr., Trice, E.L., III, and Westergaard, E.H., 1985b, 

Significance of some middle Atokan to early Missourian conodont faunas from the Llano Uplift and Colorado River Valley, Texas: Southwest Section American Association of 

Petroleum Geologists 1985 Transactions, p. 117-131.

Gromczakiewicz-Lomnicka, Aleksandra, 1974, Upper Visean conodont fauna from the Carboniferous limestone north of Krzeszowice (environs of Cracow, Poland): Annales de la 

Societe Geologique de Pologne, v. 44, no. 4, p. 475-481.

Groves, J.R., 1986, Foraminiferal characterization of the 

Morrowan-Atokan (lower Middle Pennsylvanian) boundary: 

Geological Society of America Bulletin, v. 97, p. 346-353.

————1988, Calcareous foraminifers from the Bashkirian stratotype (middle Carboniferous, south Urals) and their significance for intercontinental correlations and the evolution of 

the Fusulinidae: Journal of Paleontology, v. 62, no. 3, p. 368- 

399.

Gruzlovic, P.O., 1991, Stratigraphic evolution and lateral facies 

changes across a carbonate ramp and their effect on parasequences of the Carboniferous Lisburne Group, Arctic 

National Wildlife Refuge, northeastern Brooks Range, 

Alaska: Fairbanks, Alaska, University of Alaska Fairbanks, 

M.S. thesis, 200 p.

Grybeck, D.B., Beikman, H.M., Brosge, W.P, Tailleur, I.L., and 

Mull, C.G., 1977, Geologic map of the Brooks Range, 

Alaska: U.S. Geological Survey Open-File Report 77-166B, 

scale 1:1,000,000, 2 sheets.

Gunnell, F.H., 1931, Conodonts from the Fort Scott Limestone of 

Missouri: Journal of Paleontology, v. 5, no. 3, p. 244-252.

————1933, Conodonts and fish remains from the Cherokee, 

Kansas City, and Wabaunsee groups of Missouri and Kansas: 

Journal of Paleontology, v. 7, no. 3, p. 261-297.

Harris, A.G., Rexroad, C.B., Lierman, R.T., and Askin, R.A., 

1990, Evaluation of a CAI anomaly, Putnam County, central
REFERENCES CITED 53

Indiana, U.S.A.: Possibility of a Mississippi Valley-type 

hydrothermal system, in Ziegler, Willi, ed., Papers on conodonts and Ordovician to Triassic conodont stratigraphy; 1st 

International Senckenberg Conference and 5th European 

Conodont Symposium (ECOS V) Contributions IV: Courier 

Forschungsinstitut Senckenberg, no. 118, p. 253-266.

Harris, R.W., and Hollingsworth, R.V., 1933, New Pennsylvanian 

conodonts from Oklahoma: American Journal of Science, 5th 

Series, v. 25, no. 147, p. 193-204.

Hass, W.H., 1953, Conodonts of the Barnett Formation of Texas: 

U.S. Geological Survey Professional Paper 243-F, 94 p.

Higgins, A.C., 1961, Some Namurian conodonts from North 

Staffordshire: Geological Magazine, v. 98, no. 3, p. 210-224.

————1975, Conodont zonation of the late Visean-early Westphalian strata of the south and central Pennines of northern 

England: Bulletin of the Geological Survey of Great Britain, 

no. 53, 89 p.

————1985, Conodonts of the Silesian Subsystem from Great

Britain and Ireland, part 2 of the Carboniferous System, 

chapter 6, in Higgins, A.C., and Austin, R.L., eds., A stratigraphical index of conodonts: Chichester, England, Ellis 

Horwood, British Micropalaeontological Society, p. 210- 

227.

Higgins, A.C., and Bouckaert, Jos, 1968, Conodont stratigraphy 

and paleontology of the Namurian of Belgium: Service 

Geologique de Belgique, Memoire no. 10, 64 p.

Higgins, A.C., Richards, B.C., and Henderson, C.M., 1991, Conodont biostratigraphy and paleoecology of the uppermost 

Devonian and Carboniferous of the western Canada sedimentary basin, in Orchard, M.J., and McCracken, A.D., eds., 

Ordovician to Triassic conodont paleontology of the Canadian Cordillera: Geological Survey of Canada Bulletin 417, 

p. 215-252.

Higgins, A.C., and Wagner-Gentis, C.H.T., 1982, Conodonts, 

goniatites and the biostratigraphy of the earlier Carboniferous 

from the Cantabrian Mountains, Spain: Palaeontology, v. 25, 

Part 2, p. 313-350.

Hubbard, R.J., Edrich, S.P, and Rattey, R.P, 1987, Geological 

evolution and hydrocarbon habitat of the "Arctic Alaska 

microplate," in Tailleur, I.L., and Weimer, Paul, eds., Alaskan 

North Slope geology: Bakersfield, California, Pacific Section 

Society of Economic Paleontologists and Mineralogists and 

the Alaska Geological Society, v. 2, p. 797-830.

Igo, Hisayoshi, and Koike, Toshio, 1964, Carboniferous conodonts 

from the Omi Limestone, Niigata Prefecture, central Japan 

(studies of Asian conodonts, Part I): Palaeontological Society 

of Japan, Transactions and Proceedings, new series no. 53, 

p. 179-193.

————1968, Carboniferous conodonts from Kuantan, Malaya: 

Geology and Palaeontology of southeast Asia, v. 5, p. 26-30.

Imm, T.A., 1986, Preliminary detailed stratigraphic sections and 

bedrock maps of the Lisburne Group of the Mt. Michelson 

C-3 and C-4 quadrangles, western Sadlerochit and northwestern Shublik Mountains, northeastern Alaska: Alaska Division 

of Geological & Geophysical Surveys, Public Data File 

Report 86-86e, 5 p.

Ji, Qiang, 1986, The discovery of some late Visean and early 

Namurian conodonts from the Duolingshan Formation in Lali 

of Yishan County, Guangxi, and their stratigraphic significance: Bulletin of the Institute of Geology, Chinese Academy 

of Geological Sciences, no. 14, p. 173-191.

Johnsson, M.J., Pawlewicz, M.J., Harris, A.G., and Valin, Z.C., 

1992, Vitrinite reflectance and conodont color alteration 

index data from Alaska: U.S. Geological Survey Open-File 

Report 92-409, 3 Macintosh-formatted disks containing text 

and data formatted in 3.0 Microsoft Excel.

Koike, Toshio, 1967, A Carboniferous succession of conodont faunas from the Atetsu Limestone in southwest Japan (Studies of 

Asiatic conodonts, Part VI): Science Reports of the Tokyo 

Kyoiku Daigaku, Section C, Geology, Mineralogy and Geography, v. 9, no. 93, p. 279-318.

Kolar-Jurkovsek, Tea, and Jurkovsek, Bogdan, 1994, Frasnian and 

Visean-Namurian conodonts faunas at Praprotno, Slovenia: 

Rivista Italiana di Paleontologia e Stratigrafia, v. 99, no. 4, 

p. 427-440.

Kozur, Heinz, and Merrill, G. K., 1975, Diplognathodus, in Kozur, 

Heinz, Beitrage zur Conodontenfauna des Perm: GeologischPalaontologische Mitteilungen Innsbruck, v. 3, p. 9-10.

Krumhardt, A.P., 1992, Conodont biostratigraphy and biofacies of 

the Carboniferous Wahoo Limestone, eastern Sadlerochit 

Mountains, Arctic National Wildlife Refuge, northeast 

Brooks Range, Alaska: Fairbanks, Alaska, The University of 

Alaska Fairbanks, M.S. thesis, 157 p.

Krumhardt, A.P., and Harris, A.G., 1990, Conodont biostratigraphy and biofacies of the Wahoo Limestone (Carboniferous), 

Sadlerochit Mountains, northeast Brooks Range, Alaska 

[abs.]: Geological Society of America Abstracts with Programs, v. 22, no. 1, p. 12.

Landing, Ed, and Wardlaw, B.R., 1981, Atokan conodonts from 

the Pennsylvanian outlier of the Michigan basin: Journal of 

Paleontology, v. 55, no. 6, p. 1251-1269.

Lane, H.R., 1967, Uppermost Mississippian and Lower Pennsylvanian conodonts from the type Morrowan region, Arkansas: 

Journal of Paleontology, v. 41, no. 4, p. 920-942.

————1977, Morrowan (Early Pennsylvanian) conodonts of 

northwestern Arkansas and northeastern Oklahoma, in Sutherland, P.K., and Manger, W.L., eds.. Upper ChesterianMorrowan stratigraphy and the Mississippian-Pennsylvanian 

boundary in northeastern Oklahoma and northwestern 

Arkansas: Oklahoma Geological Survey Guidebook 18, 

p. 177-180.

Lane, H.R., Baesemann, J.F, Brenckle, PL., and West, R.R., 

I985a, Arrow Canyon, Nevada—A potential midCarboniferous boundary stratotype, in Dixieme Congres 

International de Stratigraphie et de Geologic du Carbonifere, 

Madrid, 1983: Compte Rendu, v. 4, p. 429-439.

Lane, H.R., Baesemann, J.F, and Groves, J.R., 1985b, Is the base 

of the Reticuloceras Zone a reliably recognizable biostratigraphic level?, in Lane, H.R., and Ziegler, Willi, eds.. Toward 

a boundary in the middle of the Carboniferous: Stratigraphy 

and paleontology: Courier Forschungsinstitut Senckenberg, 

no. 74, p. 137-148.

Lane, H.R., and Manger, W.L., 1985, Toward a boundary in the 

middle of the Carboniferous (1975-1985): Ten years of 

progress, in Lane, H.R., and Ziegler, Willi, eds.. Toward a 

boundary in the middle of the Carboniferous: Stratigraphy 

and paleontology: Courier Forschungsinstitut Senckenberg, 

no. 74, p. 15-34.
54 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

Lane, H.R., Merrill, O.K., Straka, J.J., II, and Webster, G.D., 1971, 

North American Pennsylvanian conodont biostratigraphy: 

Geological Society of America Memoir 127, p. 395-414.

Lane, H.R., and Straka, J.J., II, 1974, Late Mississippian and Early 

Pennsylvanian conodonts, Arkansas and Oklahoma: Geological Society of America Special Paper 152, 144 p.

Lane, H.R., and Ziegler, Willi, 1984, Proposal of Gnathodus bilineatus (Roundy, 1926) as type species of the genus Gnathodus 

Pander, 1856, (Conodonta): Senckenbergiana Lethaea, v. 65, 

p. 257-263.

————eds., 1985, Toward a boundary in the middle of the Carboniferous: Stratigraphy and paleontology: Courier Forschungsinstitut Senckenberg, no. 74, 195 p.

Lemos, V.B., 1993, Conodontes do Carbonifero das Bacias do 

Amazonas e Solimoes Taxonomia—Parte I: Pesquisas, v. 19, 

no. 1, p. 75-93.

Lerand, M., 1973, Beaufort Sea, in McCrossan, R.G., ed., Future 

petroleum provinces of Canada—Their geology and potential: Canadian Society of Petroleum Geologists Memoir no. 1, 

p. 315-386.

Li, Dongjin, 1986, Discovery of the conodont fauna from the central area of Jilin Province and its significance in stratigraphy: 

Geological Jilin, v. 17, no. 1, p. 36-44.

Mamet, B.L., 1975, Carboniferous Foraminifera and algae of the 

Amsden Formation (Mississippian and Pennsylvanian) of 

Wyoming: U.S. Geological Survey Professional Paper 848- 

B, 18 p.

Mamet, B.L., and Armstrong, A.K., 1972, Lisburne Group, Franklin and Romanzof Mountains, northeastern Alaska, in Geological Survey Research 1972: U.S. Geological Survey 

Professional Paper 800-C, p. C127-C144.

————1984, The Mississippian-Pennsylvanian boundary in the 

northeastern Brooks Range, arctic Alaska, in Sutherland, 

P.K., and Manger, W.L., eds., Neuvieme Congres International de Stratigraphie et de Geologic du Carbonifere: Carbondale, Southern Illinois University Press, p. 428-436.

Mamet, B.L., and Skipp, B.A., 1970, Preliminary foraminiferal 

correlations of Early Carboniferous strata in the North American Cordillera: Congres et Colloques de 1'Universite de 

Liege, Colloque sur la Stratigraphie du Carbonifere, v. 55, 

p. 327-348.

Manger, W.L., and Sutherland, P.K., 1992, Analysis of sections 

presumed to be complete across the MississippianPennsylvanian boundary, southern Midcontinent, in Sutherland, P.K., and Manger, W.L., eds., Recent advances in 

middle Carboniferous biostratigraphy—A symposium: Oklahoma Geological Survey Circular 94, p. 69-79.

Mapes, R.H., and Rexroad, C.B., 1986, Conodonts from the Imo 

Formation (upper Chesterian) north-central Arkansas: Geologica et Palaeontologica, no. 20, p. 113-123.

Matthews, S.C., and Thomas, J.M., 1974, Lower Carboniferous 

conodont faunas from north-east Devonshire: Palaeontology, 

v. 17, pt. 2, p. 371-385.

Merrill, G.K., 1973a, Pennsylvanian conodont paleoecology, in 

Rhodes, F.H.T., ed., Conodont paleozoology: Geological 

Society of America Special Paper 141, p. 239-274.

————1973b, Pennsylvanian nonplatform conodont genera, I: 

Spathognathodus: Journal of Paleontology, v. 47, p. 289-314.

—1974, Pennsylvanian conodont localities in northeastern 

Ohio: State of Ohio, Department of Natural Resources, Division of Geological Survey, Guidebook no. 3, 25 p.

—1975, Pennsylvanian conodont biostratigraphy and paleoecology of northwestern Illinois: Geological Society of 

America Microform Publication 3, 93 p.

—1987, Topotypic material of Gnathodus bilineatus Roundy,

in Grayson, R.C., Jr., Merrill, G.K., and Miller, J.F., eds.. 

Early and late Paleozoic conodont faunas of the Llano uplift 

region, central Texas—Biostratigraphy, systemic boundary 

relationships, and Stratigraphie importance, Guidebook for 

Field Trip 1, Geological Society of America South-Central 

Section Meeting: Waco, Texas, Bay lor University, p. 147- 

154.

Merrill, O.K., and Grayson, R.C., Jr., 1989, Conodont paleoecology in the type East Mountain Shale, north-central Texas, in 

Boardman, D.R., II, Barrick, J.E., Cocke, Jim, and Nestell, 

M.K., eds.. Middle and Late Pennsylvanian chronostratigraphic boundaries in north central Texas: Glacial-eustatic 

events, biostratigraphy and paleoecology: Lubbock, Texas 

Tech University Studies in Geology, pt. II, p. 235-248.

Merrill, G.K., and King, C.W., 1971, Platform conodonts from the 

lowest Pennsylvanian rocks of northwestern Illinois: Journal 

of Paleontology, v. 45, no. 4, p. 645-664.

Merrill, G.K., and Martin, M.D., 1976, Environmental control of 

conodont distribution in the Bond and Mattoon formations 

(Pennsylvanian, Missourian), northern Illinois, in Barnes, 

C.R., ed., Conodont paleoecology: Geological Association of 

Canada Special Paper 15, p. 243-271.

Merrill, G.K., and Powell, R.J., 1980, Paleobiology of juvenile 

(nepionic?) conodonts from the Drum Limestone (Pennsylvanian, Missourian—Kansas City area) and its bearing on apparatus ontogeny: Journal of Paleontology, v. 54, no. 5, p. 1058- 

1074.

Merrill, G.K., and von Bitter, PH., 1976, Revision of conodont 

biofacies nomenclature and interpretations of environmental 

controls in Pennsylvanian rocks of eastern and central North 

America: Life Sciences Contributions, Royal Ontario 

Museum, no. 108, p. 1-60.

————1979, Evolution of Carboniferous conodont communities: 

Conodont biofacies through time, in Palaeontological characteristics of the main subdivisions of the Carboniferous: 

Compte Rendu Huitieme Congres International de Stratigraphie et de Geologic Carbonifere: Moscow, "Nauka," p. 222- 

229.

————1984, Facies and frequencies among Pennsylvanian conodonts: Apparatuses and abundances, in Clark, D.L., ed., 

Conodont biofacies and provincialism: Geological Society of 

America Special Paper 196, p. 251-261.

Merrill, G.K., von Bitter, PH., and Grayson, R.C., Jr., 1990, 

The generic concept in conodont paleontology—Growth, 

changes, and developments in the last two decades, in Ziegler, Willi, ed., Papers on conodonts and Ordovician to Triassic conodont stratigraphy; 1st International Senckenberg 

Conference and 5th European Conodont Symposium (ECOS 

V) Contributions IV: Courier Forschungsinstitut Senckenberg, no. 118, p. 397-408.

Metcalfe, lan, 1980, Upper Carboniferous conodont faunas of the 

Panching Limestone, Pahang, West Malaysia: Palaeontology, 

v. 23, pt. 2, p. 297-314.
REFERENCES CITED 55

—1981, Conodont zonation and correlation of the Dinantian 

and early Namurian strata of the Craven Lowlands of northern England: Institute of Geological Sciences, Report 80/10, 

70 p.

—1983, Southeast Asia, in Diaz, C.M., ed., The Carboniferous of the World: International Union of Geological Sciences 

Publication no. 16, Instituto Geologico y Minero de Espana, 

p. 213-243.

Morgan, S.K., 1992, Down-dip profile of a carbonate ramp, changing environments of the Wahoo Limestone, preliminary 

results: Alaska Division of Geological & Geophysical Surveys Public-Data File 92-7, 29 p.

Morrow, J.R., and Webster, G.D., 1991, Carbonate microfacies and 

related conodont biofacies, Mississippian-Pennsylvanian 

boundary strata, Granite Mountain, west-central Utah: 

Brigham Young University Geology Studies, v. 37, p. 99- 

124.

———1992, New stratigraphic, petrographic, and biostratigraphic 

data on the proposed Mississippian-Pennsylvanian boundary 

stratotype, Granite Mountain, west-central Utah, in Sutherland, P.K., and Manger, W.L., eds., Recent advances in 

Middle Carboniferous biostratigraphy—A symposium: Oklahoma Geological Survey Circular 94, p. 55-67.

Mull, C.G., 1982, Tectonic evolution and structural style of the 

Brooks Range, Alaska—An illustrated summary, in Powers, 

R.B., ed., Geologic studies of the Cordilleran thrust belt: 

Denver, Rocky Mountain Association of Geologists, v. 1, 

p. 1-45.

Mull, C.G., Roeder, D.H., Tailleur, I.L., Pessel, G.H., Grantz, 

Arthur, and May, S.D., 1987, Geological sections and maps 

across the Brooks Range and Arctic Slope to Beaufort Sea, 

Alaska: Geological Society of America Map and Chart Series 

MC-28s, scale 1:500,000, 1 sheet.

Murray, F.N., and Chronic, John, 1965, Pennsylvanian conodonts 

and other fossils from insoluble residue of the Minturn Formation (Desmoinesian), Colorado: Journal of Paleontology, 

v. 39, p. 594-610.

Nemirovskaya, T.I., 1987, Lower Bashkirian conodonts of the 

Donets Basin: Byulleten' Moskovskogo Obshchestva 

Ispytateley Prirody, Otdel Geologicheskiy, v. 62, no. 4, 

p. 106-126.

Nemirovskaya, T.I., and Nigmadganov, I.M., 1994, The MidCarboniferous conodont event: Courier Forschungsinstitut 

Senckenberg, no. 168, p. 319-333.

Nemirovskaya, T.I., Ferret, M.F., and Meischner, Dieter, 1994, 

Lochriea ziegleri and Lochriea senckenbergica—New conodont species from the latest Visean and Serpukhovian in 

Europe: Courier Forschungsinstitut Senckenberg, no. 168, 

p. 311-317.

Nemirovskaya, T.I., Poletaev, V.I., and Vdovenko, M.W., 1991, 

The Kal'Mius section, Donbass, Ukraine, U.S.S.R.: A Soviet 

proposal for the Mid-Carboniferous boundary stratotype, in 

Brenckle, PL., and Manger, W.L., eds., Intercontinental correlation and division of the Carboniferous System: Courier 

Forschungsinstitut Senckenberg, no. 130, p. 247-272.

Nigmadganov, I.M., and Nemirovskaya, T.I., 1992a, MidCarboniferous boundary conodonts from the Gissar Ridge, 

south Tien Shan, middle Asia: Courier Forschungsinstitut 

Senckenberg, no. 154, p. 253-275.

————1992b, New conodont species from the mid-Carboniferous 

boundary deposits of south Tien Shan: Palaeontological Journal, no. 3, p. 51-58.

Norby, R.D., 1976, Conodont apparatuses from Chesterian (Mississippian) strata of Montana and Illinois: Urbana, Illinois, 

University of Illinois, Ph.D. thesis, 295 p.

Norby, R.D., and Rexroad, C.B., 1985, Vogelgnathus, a new Mississippian conodont genus: Indiana Department of Natural 

Resources, Geological Survey Occasional Paper 50, 14 p.

Norris, P.K., 1982, Geology of the northern Yukon and northwestern District of MacKenzie: Geological Survey of Canada 

Map 1581 A, scale 1:500,000.

Orchard, M.J., and Struik, L.C., 1984, Conodonts and stratigraphy 

of upper Paleozoic limestones in Cariboo gold belt, eastcentral British Columbia: Canadian Journal of Earth Sciences, v. 22, p. 539-552.

Osleger, David, 1991, Subtidal carbonate cycles: Implications 

from allocyclic vs. autocyclic controls: Geology, v. 19, 

p. 917-920.

Palmieri, Vincent, 1969, Upper Carboniferous conodonts from 

limestones near Murgon, south-east Queensland: Queensland 

Geological Survey Publication 341, Palaeontological Paper 

no. 17, 13 p.

Pander, C.H., 1856, Monographie der fossilen Fische des silurischen Systems der russisch-baltischen Gouvernements: 

Akademie der Wissenschaften St. Petersburg, 91 p.

Perlmutter, Barry, 1975, Conodonts from the uppermost Wabaunsee Group (Pennsylvanian) and the Admire and Council 

Grove Groups (Permian) in Kansas: Geologica et Palaeontologica, no. 9, p. 95-115.

Plafker, George, Harris, A.G., and Reed, K.M., 1985, Early Pennsylvanian conodonts from the Strelna Formation, Chitna Valley, in Bartsch-Winkler, Susan, ed., The United States 

Geological Survey in Alaska: Accomplishments during 1984: 

U.S. Geological Survey Circular 967, p. 71-74.

Pohler, S.M.L., and Barnes, C.R., 1990, Conceptual models in 

conodont paleoecology, in Ziegler, Willi, ed., Papers on conodonts and Ordovician to Triassic conodont stratigraphy; 1st 

International Senckenberg Conference and 5th European 

Conodont Symposium (ECOS V) Contributions IV: Courier 

Forschungsinstitut Senckenberg, no. 118, p. 409-440.

Purnell, M.A., 1992, Conodonts of the Lower Border Group and 

equivalent strata (Lower Carboniferous) in northern Cumbria 

and Scottish borders, U.K.: Royal Ontario Museum Life Sciences Contributions no. 156, 79 p.

————1993, The Kladognathus apparatus (Conodonta, Carboniferous): Homologies with ozarkodinids, and the prioniodinid 

bauplan: Journal of Paleontology, v. 67, p. 875-882.

Purnell, M.A., and von Bitter, PH., 1992, Vogelgnathus Norby and 

Rexroad (Conodonta): New species from the Lower Carboniferous of Atlantic Canada and northern England: Journal of 

Paleontology, v. 66, p. 311-331.

Qiu, Hongrong, 1984, Les conodontes du nord et du sud du Yorlung Zangbo au Xizang (Tibet), in Mercier, J.L., and 

Guangcen, Li, eds.. Mission Franco-Chinoise au Tibet 1980; 

Etude geologique et geophysique de la croute terrestre et du 

manteau superieur du Tibet et de 1'Himalaya: AnatoleFrance, Centre National de la Recherche Scientifique de 

France Academie, p. 109-131.
56 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

Ramovs, Anton, 1990a, Conodonten aus dem Unterkarbon von 

Jezersko, Zentral-Karawanken, Slowenien: Geologica et 

Palaeontologica, no. 24, p. 89-107.

————19905, Bine Conodontenfauna aus dem Unterkarbon 

siidlich des Eisenbergwerkes Ljubija, West-Bosnien: Geologica et Palaeontologica, no. 24, p. 109-113.

Read, J.F., 1982, Carbonate platforms of passive (extensional) 

continental margins: Types, characteristics and evolution: 

Tectonophysics, no. 81, p. 195-212.

Reiser, H.N., 1970, Northeast Brooks Range, in Adkinson, W.K., 

and Brosge, M.M., eds., Proceedings on the geologic seminar 

on the North Slope of Alaska: Los Angeles, American Association of Petroleum Geologists Pacific Section Meeting, 

p. K1-K13.

Rejebian, V.A., Harris, A.G., and Huebner, J.S., 1987, Conodont 

color and textural alteration: An index to regional metamorphism, contact metamorphism, and hydrothermal alteration: 

Geological Society of America Bulletin, v. 99, p. 471-479.

Rexroad, C.B., 1957, Conodonts from the Chester Series in the 

type area of southwestern Illinois: Illinois State Geological 

Survey Report of Investigations 199, 43 p.

————1958, Conodonts from the Glen Dean Formation (Chester) 

of the Illinois Basin: Illinois State Geological Survey Report 

of Investigations 209, 27 p.

————1981, Conodonts from the Vienna Limestone Member of 

the Branchville Formation (Chesterian) in southern Indiana: 

Indiana Department of Natural Resources, Geological Survey 

Occasional Paper 34, 16 p.

————1993, Conodonts from coal balls in the Springfield Coal

Member of the Petersburg Formation (Desmoinesian, Pennsylvanian) in southern Indiana: Proceedings of the Indiana 

Academy of Science, v. 102, p. 83-91.

Rexroad, C.B., and Burton, R.C., 1961, Conodonts from the Kinkaid Formation (Chester) in Illinois: Journal of Paleontology, 

v. 35, no. 6, p. 1143-1158.

Rexroad, C.B., and Furnish, W.M., 1964, Conodonts from the 

Pella Formation (Mississippian), south-central Iowa: Journal 

of Paleontology, v. 38, no. 4, p. 667-676.

Rexroad, C.B., and Horowitz, A.S., 1990, Conodont paleoecology 

and multielement associations of the Beaver Bend Limestone 

(Chesterian) in Indiana: Courier Forschungsinstitut Senckenberg, no. 118, p. 493-537.

Rexroad, C.B., and Lane, H.R., 1966, Clarification of Cavusgnathus a/to, type species of the conodont genus Cavusgnathus: Journal of Paleontology, v. 40, p. 1391-1392.

Rexroad, C.B., and Merrill, G.K., 1985, Conodont biostratigraphy 

and paleoecology of middle Carboniferous rocks in southern 

Illinois, in Lane, H.R., and Ziegler, Willi, eds., Toward a 

boundary in the middle of the Carboniferous: Stratigraphy 

and paleontology: Courier Forschungsinstitut Senckenberg, 

no. 74, p. 35-64.

Reynolds, M.J., 1970, A Lower Carboniferous conodont fauna 

from Flintshire, North Wales: Bulletin of the Geological Survey of Great Britain no. 32, 19 p.

Rhodes, F.H.T., and Austin, R.L., 1971, Carboniferous conodont 

faunas of Europe, in Sweet, W.C., and Bergstrom, S.M., eds.. 

Symposium on conodont biostratigraphy: Geological Society 

of America Memoir 127, p. 317-352.

Rhodes, F.H.T., Austin, R.L., and Druce, E.G., 1969, British 

Avonian (Carboniferous) conodont faunas, and their value in

local and intercontinental correlation: British Museum (Natural History) Geology, Bulletin Supplement 5, 313 p.

Rice, W.D., and Langenheim, R.L., 1974, Conodonts of the Battleship Wash Formation, Late Mississippian, Arrow Canyon 

Range, Clark County, Nevada: Wyoming Geological Association, v. 7, no. 2, p. 19-36.

Riley, N.J., Varker, W.J., Owens, Bernard, Higgins, A.C., and 

Ramsbottom, W.H.C., 1987, Stonehead Beck, Cowling, 

North Yorkshire, England: A British proposal for the midCarboniferous boundary stratotype: Courier Forschungsinstitut Senckenberg, no. 98, p. 159-177.

Roundy, P.V., 1926, Part II, The micro-fauna, in Roundy, P.V., 

Girty, G.H., and Goldman, M.I., eds., Mississippian formations of San Saba County, Texas: U.S. Geological Survey 

Professional Paper 146, p. 5-17.

Ruppel, S.C., and Lemmer, T.M., 1986, Mississippian conodonts 

from the southern Texas Panhandle: Texas Bureau of Economic Geology, Geological Circular 86-7, 36 p.

Sada, Kimiyoshi, Inoue, Masashi, and Oho, Yukimasa, 1985, The 

conodont faunas discovered from the Paleozoic in the Yuki 

area of Jinseki County, Hiroshima Prefecture: Fossils, Palaeontological Society of Japan, no. 39, p. 28-31.

Savage, N.M., and Barkeley, S.J., 1985, Early to Middle Pennsylvanian conodonts from the Klawak Formation and the Ladrones Limestone, southeastern Alaska: Journal of 

Paleontology, v. 59, no. 6, p. 1451-1475.

Schrader, F.C., 1902, Geologic section of the Rocky Mountains in 

northern Alaska: Geological Society of America Bulletin, v. 

13, p. 233-252.

————1904, A reconnaissance in northern Alaska: U.S. Geological Survey Professional Paper 20, 139 p.

Scoffin, T.P, 1987, An introduction to carbonate sediments and 

rocks: New York, Chapman and Hall, 274 p.

Scott, H.W., 1942, Conodont assemblages from the Heath Formation, Montana: Journal of Paleontology, v. 16, no. 3, p. 293- 

301.

Semichatova, S.V., and others, 1979, Bashkirian Stage as a global 

stratigraphic unit, in Wagner, R.H., Higgins, A.C., and 

Meyen, S.V., eds., The Carboniferous of the U.S.S.R.: Yorkshire Geological Society Occasional Publication No. 4, p. 99- 

116.

Skipp, Betty, Baesemann, J.F., and Brenckle, PL., 1985, A reference area for the Mississippian-Pennsylvanian (midCarboniferous) boundary in east-central Idaho, U.S.A.: Diexieme Congres International de Stratigraphie et de Geologie du 

Carbonifere, Madrid, 1983: Compte Rendu, v. 4, p. 403-428.

Stanley, E.A., 1958, Some Mississippian conodonts from the high 

resistivity shale of the Nancy Watson no. 1 well in northeastern Mississippi: Journal of Paleontology, v. 32, no. 3, p. 459- 

476.

Stone, J.J., 1991, Arundian (Lower Carboniferous) conodonts 

from south Wales: Special Papers in Palaeontology No. 46, 

63 p.

Sutherland, P.K., and Grayson, R.C., 1992, in Sutherland, P.K., 

and Manger, W.L., eds., Recent advances in Middle 

Carboniferous biostratigraphy—A symposium: Oklahoma 

Geological Survey Circular 94, p. 39-54.

Sutherland, P.K., and Manger, W.L., 1984a, The Atokan Series: An 

interval in search of a name: Oklahoma Geological Survey 

Bulletin 136, p. 1-8.
REFERENCES CITED 57

—19845, The Mississippian-Pennsylvanian boundary in 

North America, in Sutherland, P.K., and Manger, W.L., eds., 

Biostratigraphy: International Congress on Carboniferous 

Stratigraphy and Geology, v. 2, p. 319-329.

—1992, eds., Recent advances in Middle Carboniferous biostratigraphy—A symposium: Oklahoma Geological Survey 

Circular 94, 181 p.

Sweet, W.C., \973,Anchignathodus minutus (ELLISON, 1941), in 

Ziegler, Willi, ed., Catalogue of conodonts, v. I: Stuttgart, E. 

Schweizerbart'sche Verlagsbuchhandlung, p. 15-17.

————1977, Genus Hindeodus REXROAD & FURNISH, 1964, 

in Ziegler, Willi, ed., Catalogue of conodonts, v. Ill: Stuttgart, 

E. Schweizerbart'sche Verlagsbuchhandlung, p. 203-205.

————1988, The Conodonta: Morphology, taxonomy, paleoecology, and evolutionary history of a long-extinct animal phylum: New York, Oxford University Press, Oxford 

Monographs on Geology and Geophysics no. 10, 212 p.

Tailleur, I.L., and Weimer, Paul, eds., 1987, Alaskan North Slope 

geology: Bakersfield, California, Society of Economic Paleontologists and Mineralogists, Pacific Section, v. 1 and 2, 

874 p.

Thompson, T.L., 1970, Lower Pennsylvanian conodonts from 

McDonald County, Missouri: Journal of Paleontology, v. 44, 

no. 6, p. 1041-1048.

Thompson, T.L., and Goebel, E.D., 1969, Conodonts and stratigraphy of the Meramecian Stage (Upper Mississippian) in Kansas: Kansas Geological Survey Bulletin 192, 56 p.

Toomey, D.F., Baesemann, J.F, and Lane, H.R., 1974, The biota of 

the Pennsylvanian (Virgilian) Leavenworth Limestone, midcontinent region; Part 5: Distribution of miscellaneous microfossils: Journal of Paleontology, v. 48, no. 6, p. 1156-1165.

Tubbs, P.K., 1986, Opinion 1415 Polygnathus bilineatus Roundy, 

1926 designated as type species of Gnathodus Pander, 1856 

(Conodonta): Bulletin of Zoological Nomenclature, v. 43, 

p. 262-263.

Tynan, M.C., 1980, Conodont biostratigraphy of the Mississippian 

Chainman Formation, western Millard County, Utah: Journal 

of Paleontology, v. 54, no. 6, p. 1282-1309.

Varker, W.J., and Sevastopulo, G.D., 1985, The Carboniferous 

System; Part 1—Conodonts of the Dinantian Subsystem from 

Great Britain and Ireland, in Higgins, A.C., and Austin, R.L., 

eds., A stratigraphical index of conodonts: Chichester, 

England, Ellis Horwood Limited, p. 167-209.

Varker, W.J., Owens, Bernard, and Riley, N.J., 1991, Integrated 

biostratigraphy for the proposed mid-Carboniferous boundary 

stratotype, Stonehead Beck, Cowling, north Yorkshire, 

England: Courier Forschungsinstitut Senckenberg, no. 130, 

p. 221-235.

von Bitter, P.H., 1972, Environmental control of conodont distribution in the Shawnee Group (Upper Pennsylvanian) of 

eastern Kansas: University of Kansas Paleontological Contributions, Article 59, 105 p.

von Bitter, P.H., and Merrill, G.K., 1990, Effects of variation on 

the speciation and phylogeny of Diplognathodus: Courier 

Forschungsinstitut Senckenberg, no. 118, p. 105-129.

von Bitter, P.H., and Norby, R.D., 1994, Ontogenetic development 

of Pa element cup microsculpture in Lochriea commutata 

(Branson and Mehl, 1941) (Conodonta, Carboniferous): Taxonomic implications: Journal of Paleontology, v. 68, no. 4, 

p. 861-869.

Wallace, W.K., and Hanks, C.L., 1990, Structural provinces of the 

northeastern Brooks Range, Arctic National Wildlife Refuge, 

Alaska: American Association of Petroleum Geologists Bulletin, v. 74, p. 1100-1118.

Wang, Zhihao, and Higgins, A.C., 1989, Conodont zonation of the 

Namurian-Lower Permian strata in south Guizhou, China: 

Palaeontologia Cathayana, no. 4, p. 261-325.

Wang, Zhihao, Lane, H.R., and Manger, W.L., 1987, Carboniferous and Early Permian conodont zonation of north and northwest China, in Brenckle, PL., and others, eds., Selected 

studies in Carboniferous paleontology and biostratigraphy: 

Courier Forschungsinstitut Senckenberg, no. 98, p. 119-157.

Wardlaw, B.R., 1984, Conodont faunas, MississippianPennsylvanian boundary. Granite Mountain section, in Webster, G.D., and others. Road logs for the MississippianPennsylvanian boundary in the eastern Great Basin: Salt Lake 

City, Utah, to Las Vegas, Nevada (Field Trip 1), in Lintz, 

Joseph, Jr., ed., Western geological excursions, v. 1: Reno, 

Nevada, Geological Society of America and affiliated societies, Field-Trip Guidebook, p. 82-84.

————1985, Late Mississippian-Early Pennsylvanian 

(Namurian) conodont biostratigraphy of the northern Rocky 

Mountains: Diexieme Congres International de Stratigraphie 

et de Geologic du Carbonifere, Madrid, 1983: Compte 

Rendu, v. 4, p. 391-401.

Watts, K.F., 1990, Analysis of reservoir heterogeneities due to 

shallowing-upward cycles in carbonate rocks of the Pennsylvanian Wahoo Limestone of northeastern Alaska: U.S. 

Department of Energy, 1990 Annual Report, Contract DEAC22-89BC14471,76p.

————1991, Analysis of reservoir heterogeneities due to 

shallowing-upward cycles in carbonate rocks of the Pennsylvanian Wahoo Limestone of northeastern Alaska: U.S. 

Department of Energy, 1991, Annual Report, Contract DEAC22-89BC14471, 143 p.

Watts, K.F., Carlson, R.C., Imm, T.A., Gruzlovic, P.O., and Hanks, 

C.L., 1988, Influence of sub-Mississippian paleogeography 

on the Carboniferous Lisburne Group, Arctic National Wildlife Refuge, northeast Brooks Range, Alaska [abs.]: American Association of Petroleum Geologists Bulletin, v. 72, no. 

2, p. 257.

Watts, K.F., Imm, T.A., and Harris, A.G., 1989, Stratigraphy and 

paleogeographic significance of the Carboniferous Wahoo 

Limestone—Reexamination of the type section, northeastern 

Brooks Range, Alaska [abs.]: Geological Society of America 

Abstracts with Programs, v. 21, no. 5, p. 157.

Watts, K.F, and others, 1992, Unconformity above the Lisburne 

Group—A major Pennsylvanian-Permian hiatus in the 

northeastern Brooks Range, Alaska [abs.]; International Conference on Arctic Margins (1CAM) Abstracts: Anchorage, 

Alaska, Alaska Geological Society, p. 70.

Webster, G.D., 1969, Chester through Derry conodonts and stratigraphy of northern Clark and southern Lincoln counties. 

Nevada: University of California Publications in Geological 

Sciences, v. 79, p. 1-105.

Weibel, C.P., and Norby, R.D., 1992, Paleopedology and conodont 

biostratigraphy of the Mississippian-Pennsylvanian boundary 

interval, type Grove Church Shale area, southern Illinois, in 

Sutherland, P.K., and Manger, W.L.. eds., Recent advances in
58 CONODONT BIOSTRATIGRAPHY AND BIOFACIES OF THE WAHOO LIMESTONE

Middle Carboniferous biostratigraphy—A symposium: Oklahoma Geological Survey Circular 94, p. 39-54.

Whiteside, J.R., and Grayson, R.C. Jr., 1990, Carboniferous conodont faunas, northern Ouachita Mountains, Oklahoma, in 

Suneson, N.H, Campbell, J.A., and Tilford, M.J., eds.. Geology and resources of the frontal belt of the western Ouachita 

Mountains, Oklahoma: Oklahoma Geological Survey, Special 

Publication 90-1, p. 149-167.

Wilson, J.A., 1975, Carbonate facies in geologic history: New 

York, Springer-Verlag, 471 p.

Wilson, M.A., 1985, Conodont biostratigraphy and paleoenvironments at the Mississippian-Pennsylvanian boundary (Carboniferous: Namurian) in the Spring Mountains of southern 

Nevada: Newsletters on Stratigraphy, v. 14, no. 2, p. 69-80.

Wood, G.V., and Armstrong, A.K., 1975, Diagenesis and stratigraphy of the Lisburne Group limestones of the Sadlerochit 

Mountains and adjacent areas, northeastern Alaska: U.S. 

Geological Survey Professional Paper 857, 47 p.

Youngquist, Walter, and Miller, A.K., 1949, Conodonts from the 

Late Mississippian Pella Beds of south-central Iowa: Journal 

of Paleontology, v. 23, no. 6, p. 617-622.

Ziegler, Willi, and Lane, H.R., eds., 1985, Toward a boundary in 

the middle of the Carboniferous: Stratigraphy and paleontology: Courier Forschungsinstitut Senckenberg, no. 74, 195 p.

Ziegler, Willi, and Sandberg, C.A., 1990, The Late Devonian standard conodont zonation: Courier Forschungsinstitut Senckenberg, no. 121, 115 p.
APPENDIX 1
APPENDIX 1. CONODONT FAUNAS, BIOFACIES, AND AGE AND LITHOLOGY OF COLLECTIO

BUT NOT DESCRIBED ELSEWHERE IN THIS REPORT

[Map locality number keyed to figures 1 and 2. Letters in field numbers refer to collector: JC, James Clough; ME, M.K. Eckstein; PG, PD. Gruzlovic; AK, A.P. Krumhardt

Robinson; TR, I.L. Tailleur; KW, K.F. Watts. CAI, color alteration index]

MAP LOG. NO., 

FIELD NO. 

(USGSCOLLN. 

NO.)

QUADRANGLE, 

LATITUDE N7 

LONGITUDE W.

FORMATION LrTHOLOGY OCNOOCNTS fCE. BIOFACIES 

Eastern Sadlerochit Mountains

loc. 1A1a, 

AK90D-29 

(31718-PC)

loc. 1A1b, 

AK90D-36 

(31719-PC)

loc. 1A1c, 

AK92-3 

(31859-PC)

loc. 1A2, 

90ADL1-25.3 

(32227-PC)

loc. 1B1a, 

AK92-14 

(32223-PC)

Mt. Michelson 

C-1, 

69°38'24V 

144°34'45 P

Mt. Michelson 

C-1, 

69°38'05V 

144°35'00"

Mt. Michelson 

C-1, 

69°38.057 

144-36.3 1

Alapah Limestone, 

72 m below base of 

Wahoo Limestone

Alapah Limestone, 

65 m below base of 

Wahoo Limestone

Wahoo Limestone, 

53.4 m above base 

of lower member

Alapah Limestone, 

-24 m above base

Wahoo Limestone, 

-52.0 m above 

base of lower 

member and 2 m 

below key bed 

containing 

reddish-brown and 

gray chert

Poorly-sorted, dolomitized 

bryozoan, pelmatozoan 

packstone containing minor 

ostracodes, brachiopods, 

and algae.

Partly silicified, wellsorted, fine-grained 

bryozoan, pelmatozoan 

packstone. Grains 

recrystallized and highly 

fragmented.

Medium-bedded, mediumgrained, bryozoan, 

pelmatozoan, and peloid 

grainstone containing 

minor trilobites and 

Asphaltina sp. and rare 

ostracodes and gastropods.

Lime mudstone.

Bryozoan-pelmatozoan 

grainstone.

8 Pa elements Adetogriathus lautus (Gunnell) 

12 Pa elements Cavusgnathus unicornis 

Youngquist and Miller 

16 Pa element fragments of cavusgnathoids 

2 M elements Gnathodus sp. indet. 

4 Pa elements Hindeodus sp. indet. 

5 Sb-Sc elements Kladognathus sp. indet. 

UNASSIGNED ELEMENTS'

2 Pb, 1 M, and 2 Sc 

75 indet. bar, blade, and platform fragments

2 Pa elements Adetognathus lautus (Gunnell) 

1 8 Pa element fragments of cavusgnathoids 

2 unassigned M elements (2 morphotypes) 

106 indet. bar, blade, and platform fragments

1 Pa element Adetognathus lautus (Gunnell) 

3 Pa elements Cavusgnathus unicornis 

Youngquist and Miller 

3 Pa element fragments of cavusgnathoids 

3 indet. bar fragments

6 Pa elements Cavusgnathus unicornis 

Youngquist and Miller 

1 Pa element Cavusgnathus sp. indet. 

16 Pa element fragments of cavusgnathoids 

5 Pa elements Gnathodus girtyi girtyi Hass 

2 Pa elements Gnathodus sp. indet. 

1 Sa element Hindeodus sp. indet.? 

8 Sb-Sc elements Kladognathus spp. 

1 Pa element Rhachistognathus muricatus 

(Dunn) 

UNASSIGNED ELEMENTS:

1 Pb and 3 M (2 morphotypes) 

195 moderately to well-rounded bar, blade, and 

platform fragments

2 Pa elements Gnathodus bilineatus subspp. 

indet. 

16 Pa elements Gnathodus girtyi girtyi Hass 

2 Pa elements Gnathodus girtyi simplex Dunn 

2 Pa elements Hindeodus minutus (Ellison) 

1 idioprioniodid element 

Kladognathus sp. indet. 

2 Sb-Sc elements 

UNASSIGNED ELEMENTS3 M (two morphotypes) and 1 Sc 

105 indet. bar, blade, and platform fragments

Upper R. muricatus 

Subzone (very latest 

Chesterian)

R. muricatus Zone 

(very late Chesterian)

Upper R. muricatus 

Subzone (very latest 

Chesterian); based on 

underlying samples 

from study section 

AK88a (this report)

Cavusgnathid; openplatform, near rest

depositional environ

Winnow within or f

adetognathid and (o

cavusgnathid biofaci

open-platform, nea

restricted deposition

environment.

Indeterminate (too f

conodonts); open-p

possibly near restri

depositional environ

Extensive postmorte

hydraulic transport 

the cavusgnathidkladognathid biofaci

normal-marine, ne

restricted, relative

shallow water depo

environment.

Postmortem transp

within or from the g

biofacies; normal-m

depositional environ

above wave base.
loc. 1B1b, 

AK92-13 

(32224-PC)

loc. 1B1c, 

AK92-12 

(32225-PC)

loc. 1B1d, 

AK92-11 

(32226-PC)

loc. 1B1e, 

AK90E-54 

(31834-PC)

loc. 1B1f, 

AK90E-55 

(31835-PC)

Mt. Michelson 

C-1, 

69°38.05V 

144°36.3'

Wahoo Limestone, 

-52.5 m above 

base of lower 

member and 1 .5 m 

below key bed 

containing 

reddish-brown and 

gray chert

Wahoo Limestone, 

-53 m above base 

of lower member 

and 1 m below key 

bed containing 

reddish-brown and 

gray chert

Wahoo Limestone, 

-53.5 m above 

base of lower 

member and 50 cm 

below key bed 

containing 

reddish-brown and 

gray chert

Wahoo Limestone, 

-54 m above base 

of lower member 

and 30 cm below 

key bed containing 

reddish-brown and 

gray chert

Wahoo Limestone, 

-55 m above base 

of lower member 

and within key bed 

containing 

reddish-brown and 

gray chert, 20 cm 

below its top

Bryozoan, pelmatozoan, and 

peloid grainstone.

Bryozoan-pelmatozoan 

grainstone.

Bryozoan-pelmatozoan 

grainstone.

Skeletal grainstone.

Peloidal, spiculitic 

wackestone.

6 Pa elements Cavusgnathus? tytthus Brown and 

Rexroad 

1 7 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) 

27 Pa elements Gnathodus girtyi simplex Dunn 

transitional to Declinognathodus noduliferus 

japonicus (Igo and Koike) 

Hindeodus minutus (Ellison) 

2 Pa, 1 Sa, and 1 Sb elements 

1 idioprioniodid element 

1 M element Kladognathus? so. indet. 

6 Pa elements Rhachistognathus muricatus 

(Dunn) 

1 Pa element Vogelgnathus postcampbelli (Austin 

and Husri) 

UNASSIGNED ELEMENTS2 Pb, 1 M, and 1 Sb 

126 indet. bar, blade, and platform fragments

1 Pa element Cavusgnathus? tytthus Brown and 

Rexroad 

9 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) (8 juveniles) 

1 Pa element Hindeodus sp. indet. 

2 Sb-Sc elements Kladognathus sp. indet. 

2 Pa elements Rhachistognathus muricatus 

(Dunn) 

UNASSIGNED ELEMENTS:

1 Pb 

45 indet. bar, blade, and platform fragments

5 Pa elements Cavusgnathus? tytthus Brown and 

Rexroad 

1 3 Pa element fragments of cavusgnathoids 

7 Pa and 1 Sc elements Declinognathodus 

noduliferus japonicus (Igo and Koike) (3 

juveniles) 

4 Pa elements Rhachistognathus muricatus 

(Dunn) (2 juveniles) 

UNASSIGNED ELEMENTS:

1 M and 1 Sc 

36 indet. bar, blade, and platform fragments

5 Pa elements Cavusgnathus? tytthus Brown and 

Rexroad 

2 Pa element fragments of cavusgnathoids 

2 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) transitional to 

Gnathodus girtyi simplex Dunn 

2 Pa element Rhachistognathus muricatus 

(Dunn) 

1 unassigned Pb element 

15 indet. bar, blade, and platform fragments

6 juvenile Pa elements Cavusgnathus? tytthus 

Brown and Rexroad 

5 Pa element fragments of cavusgnathoids 

1 juvenile Pa element Rhachistognathus 

muricatus (Dunn) 

2 Pa elements Vogelgnathus postcampbelli 

(Austin and Husri) 

UNASSIGNED ELEMENTS2 Pb and 1 M 

8 indet. bar, blade, and platform fragments

Lower part of 

noduliferus-primus 

Zone (very earliest 

Morrowan)

Gnathodid-declinognat

normal-marine depos

environment, above wa

base.

Indeterminate (too few 

conodonts); normal-m

depositional environm

above wave base.

Indeterminate (too few 

conodonts); normal-m

depositional environm

above wave base.

Indeterminate, too few 

conodonts; postmortem 

mixing of generally sm

forms, probably a win

representing a norma

marine depositional 

environment, above wa

base.

Indeterminate, too few 

conodonts; probably a 

winnow as all elements 

small and relatively d

Relatively shallow-wa

probably normal-mar

near restricted marine 

depositional environm
APPENDIX 1. CONODONT FAUNAS, BIOFACIES, AND AGE AND LITHOLOGY OF COLLECT

BUT NOT DESCRIBED ELSEWHERE IN THIS REPORT—CONTINU

MAP LOG. NO., 

FIELD NO. 

(USGSCOLLN. 

NO.)

loc. 1B1g, 

AK90E-55.3 

(31836-PC)

loc. 1C, 

90MR28A 

(31266-PC)

QUADRANGLE, 

LATITUDE NJ 

LONGITUDE W.

Mt. Michelson 

C-1, 

69°38.05'/ 

144°36.3'

Mt. Michelson 

C-2, 

69°37.37 

144°38.7'

FORMATION

Wahoo Limestone, 

-55.3 m above 

base of lower 

member and 0-30 

cm above key bed 

containing 

reddish-brown and 

gray chert

Top of Wahoo 

Limestone at 

contact with 

Echooka Formation

LJTHOLOGY

Peloidal grainstone and 

lesser packstonewackestone containing 

minor echinoderm debris 

and spicules.

Bioclastic, bryozoan 

grainstone.

CONODONTS

9 juvenile Pa elements Cavusgnathus? tytthus 

Brown and Rexroad 

89 Pa element fragments of cavusgnathoids 

36 chiefly juvenile Pa elements Declinognathodus 

noduliferus japonicus (Igo and Kolke), 

many transitional to Gnathodus girtyl 

simplex Dunn 

1 Pa element Declinognathodus noduliferus 

noduliferus (Ellison and Graves) 

6 juvenile Pa elements Rhachistognathus 

muricatus (Dunn) 

53 chiefly juvenile Pa elements Vogelgnathus 

postcampbelli (Austin and Husri) 

UNASSIGNED ELEMENTS13 Pb (2 morphotypes), 1 M, 3 Sa and 3 Sc 

(3 morphotypes) 

+150 indet. bar, blade, and platform fragments

1 Pa element Adetognathus spathus (Dunn) 

1 Pa element fragment Adetognathus sp. indet. 

3 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) 

4 Pa element fragments Idiognathodus sp. indet. 

3 element fragments Idioprioniodus sp. indet. 

2 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

3 juvenile Pa elements Rhachistognathus 

minutus (Higgins and Bouckaert) 

5 juvenile Pa elements Rhachistognathus sp. 

indet. 

14 Pa element fragments (generally posterior 

part of platform) of cavusgnathoids and 

rhachistognathids 

UNASSIGNED ELEMENTS1 Pb and 1 Sc 

26 indet. bar, blade, and platform fragments

AGE

Lower part of 

noduliferus-primus 

Zone (very earliest 

Morrowan)

Idiognathodus Fauna 

(late Morrowan to 

early Atokan)

BIO

Probable pos

winnow withi

vogelgnathid-

biofacies; no

near restricte

environment

Indeterminate

hydraulic m

Western Sadlerochit Mountains

loc. 2a,

84TR23-3 

(29626-PC)

Mt. Michelson 

C-3, 

69°35'27'- 

31V145" 

34'30'-36'

Wahoo Limestone, 

3 m above base of 

measured section

Medium-light-brownishgray, thick- to massivebedded, crinoidal, finegrained limestone.1 juvenile Pa element Declinognathodus noduliferus noduliferus (Graves and Ellison) 

1 Pa element Hindeodus minutus (Ellison) 

3 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

1 1 indet. bar, blade, and platform fragments 

REDEPOSITED ELEMENTS?-

4 Pa elements Cavusgnathus unicornis 

Youngquist and Miller 

5 Pa elements Cavusgnathus'? tytthus Brown and 

Rexroad 

4 Pa element fragments of cavusgnathoids 

Kladognathus sp. indet. 

3 M and 6 Sb-Sc elements

lower R. minutus fauna 

(early Morrowan)

Indeterminate

faunule is p

redeposited.
loc. 2b, 

84TR23-8 

(29627-PC)

loc. 2c, 

84TR23-32.5 

(29628-PC)

loc. 2d, 

84TR23-37.5 

(29629-PC)

loc. 2e, 

84TR23-49 

(29630-PC)

loc. 21, 

84TR23-66.5 

(29631-PC)

loc. 2g, 

84TR23-73 

(29632-PC)

Mt. Michelson 

C-3, 

69°35'27'- 

31"/145° 

34 1 30"-36"

Wahoo Limestone, 

8 m above base of 

measured section

Wahoo Limestone, 

32.5 m above base 

of measured 

section

Wahoo Limestone, 

37.5 m above base 

of measured 

section

Wahoo Limestone, 

49 m above base of 

measured section

Wahoo Limestone, 

66.5 m above base 

of measured 

section

Wahoo Limestone, 

73 m above base of 

measured section

Crinoidal grainstone 

containing irregular shaly 

partings and glauconitic 

grains and layers.

Medium-brownish-gray, 

fine-grained crinoidal 

limestone.

Slabby bedded interval 

within massive limestone; 

contains bryozoans and 

brachiopods.

Very fine-grained 

limestone.

Medium-light-gray, 

crinoidal limestone 

containing some 

brachiopods.

Dark-gray, very fine 

grained limestone 

containing only a few shelly 

fragments.

2 Pa elements Gnathodus girtyi girtyi Mass 

transitional to Declinognathodus inaequalis 

(Higgins)? 

1 Pa element Idioprioniodus sp. indet. 

1 Pa element Rhachistognathus prolixus 

Baesemann and Lane 

9 indet. bar, blade, and platform fragments 

REDEPOSITED ELEMENTS?:

2 Pa Gnathodus bilineatus bilineatus (Roundy) 

3 Pa elements Gnathodus girtyi simplex Dunn

31 Pa elements Rhachistognathus muricatus 

(Dunn) including some forms transitional 

to ft. primus Dunn 

2 Pa element fragments Rhachistognathus aff. R. 

minutus (Higgins and Bouckaert) 

2 unassigned Pb elements 

16 indet. bar, blade, and platform fragments

1 Pa element fragment Adetognathus sp. indet. 

1 Pa element Rhachistognathus minutus 

declinatus Baesemann and Lane 

7 Pa elements Rhachistognathus muricatus 

(Dunn) 

1 Pa element Rhachistognathus websteri 

Baesemann and Lane 

1 unassigned Sc element 

4 indet. bar, blade, and platform fragments

1 3 Pa elements Adetognathus lautus (Gunnell) 

3 Pa elements Adetognathus spathus (Dunn) 

40 Pa elements Rhachistognathus minutus 

subspp. 

4 Pa elements Rhachistognathus muricatus 

(Dunn) 

UNASSIGNED ELEMENTS:

4 Pb (2 morphotypes), 1 M, 3 Sb, and 1 Sc 

76 indet. bar, blade, and platform fragments

24 juvenile Pa elements Declinognathodus 

noduliferus japonicus (Igo and Koike) 

3 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

2 Pa elements Rhachistognathus muricatus 

(Dunn) 

1 unassigned Pb element 

19 indet. bar, blade, and platform fragments

5 Pa elements Adetognathus lautus (Gunnell) 

13 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) 

3 Pa elements Declinognathodus noduliferus 

noduliferus (Graves and Ellison) 

7 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

22 indet. bar, blade, and platform fragments

lower R. minutus Fauna 

(early Morrowan)

R. minutus Fauna 

(Morrowan to early 

Atokan)

Indeterminate.

Rhachistognathid; hig

energy, normal-marin

probable shoal to shoa

apron depositional 

environment.

Indeterminate.

Rhachistognathidadetognathid biofacies

because all the 

rhachistognathids are 

and the adetognathids a

large this probably 

represents a near-sho

depositional environm

The rhachistognathids 

brought to the deposit

site as winnows.

Declinognathodid; ope

marine depositional 

environment near sho

Declinognathodid; ope

marine depositional 

environment near sho
APPENDIX 1. CONODONT FAUNAS, BIOFACIES, AND AGE AND LITHOLOGY OF COLLECTIONS 

BUT NOT DESCRIBED ELSEWHERE IN THIS REPORT—CONTINUED

MAP LOG. NO.,

FIELD NO.

(USGSCOLLN.

NO.)

loc. 2h,

84TR23-96

(29633-PC)

loc. 2i,

84TR23-102

(29634-PC)

loc. 2j,

84TR26A

(29873-PC)

QUADRANGLE,

LATITUDE N7

LONGITUDE W.

Mt. Michelson

C-3,

69°35'27"-

31"/145°

34 1 30"-36"

Mt. Michelson

C-3,

69°35.57

145°36.8'

FORMATION

Wahoo Limestone,

96 m above base of

measured section

Wahoo Limestone,

1 02 m above base

of measured

section

Wahoo Limestone,

0.25 m below

contact of Wahoo

Limestone and

Echcoka Formation

UTHOLOGY

Medium-gray, finegrained, massive,

fossiliferous limestone.

Dark, crinoidal layer in

generally light-colored

rubbly unit.

Crinoidal grainstone.

CCNODOMTS

1 Pa element Adetognathus aff. A. lautus

(Gunnel!)

1 Pa element Adetognathus spathus (Dunn)

1 1 Pa elements Declinognathodus noduliferus

nodulifews (Ellison and Graves)

1 late juvenile Pa element Idiognathodus

sp. indet.

48 Pa elements Rhachistognathus mlnutus

declinatus Baesemann and Lane

2 unassigned Pb elements

67 indet. bar, blade, and platform fragments

14 Pa elements Declinognathodus noduliferus

noduliferus (Ellison and Graves)

1 Pa element Idiognathodus sp. indet.

4 element fragments Idioprioniodus sp. indet.

2 Pa elements Rhachistognathus minutus

declinatus Baesemann and Lane

2 unassigned Pb elements

4 indet. bar, blade, and platform fragments

3 Pa elements Idiognathodus sinuosus Ellison

and Graves

1 Pa element Rhachistognathus minutus

declinatus Baesemann and Lane

32 indet. bar, blade, and platform fragments

fiCE

Idiognathodus Fauna

(late Morrowan to

early Atokan)

BIOFACIES

Rhachistognathid; norm

marine, near-shoal

depositional environme

Declinognathodid; open

marine depositional

environment, possibly 

shoal.

Indeterminate (too few

conodonts).

Northwestern Philip Smith Mountains

loc. 3A,

89JC501-37b

(30894-PC)

loc. 3B,

89MR-42C

(30903-PC)

Sagavanirktok

A-1,

68°55.67

148°04.8'

Sagavanirktok

A-2,

69°06.4V

147°39.6'

Uppermost part of

Wahoo Limestone

Lisburne Group, 1

m below contact

with Echooka

Formation

Limestone.

Bioclastic, bryozoan

grainstone.

2 Pa element fragments Hindeodus sp. indet.

Idiognathodus sinuosus Ellison and Graves

52 Pa and 4 Pb elements

Idioprioniodus sp. indet.

1 Sa and 1 Sb elements

81 indet. bar, blade, and platform fragments

32 Pa elements Idiognathodus sinuosus Ellison

and Graves

13 element fragments Idioprioniodus sp. indet.

1 1 Pa elements Rhachistognathus minutus

declinatus Baesemann and Lane

2 unassigned Pb elements

102 indet. bar, blade, and platform fragments

Idiognathodus Fauna

(late Morrowan to at

least early Atokan)

Idiognathodus Fauna

(late Morrowan to

early Atokan)

Idiognathodid; open-ma

moderate-energy

depositional environme

Idiognathodidrhachistognathid; norm

marine depositional

environment, possibly 

shoal.

Philip Smith Mountains, Wahoo Lake area

loc. 4A1a,

SKM91D-70

(31826-PC)

Sagavanirktok

A-1,

69°01.4V

147°00.1'

Alapah Limestone,

70 m below base of

Wahoo Limestone

Thick- to medium-bedded,

crinoidal grainstone

containing faint

laminations.

2 Pa elements Cavusgnathus"? tytthus Brown

and Rexroad

4 Pa element fragments cavusgnathoids

2 Pa elements Gnathodus girtyi simplex Dunn

1 Pa element Gnathodus aff. G. girtyi Hass

Hindeodus minutus (Ellison)?

2 Pa (fragments)

5 Pa elements Rhachistognathus muricatus

(Dunn)

5 indet. bar, blade, and platform fragments

R. muricatus Zone

(very late Chesterian)

Indeterminate (too few

conodonts); relatively

shallow-water, norma

marine depositional

environment.
loc. 4A1b, 

SKM91D-155 

(31828-PC)

loc. 4A1c, 

SKM91D-279.5 

(31837-PC)

loc. 4A1d, 

SKM91D-295 

(31830-PC)

loc. 4B, 

KW90D-0.5 

(31214-PC)

loc. 4C1a, 

KW90A-26 

(31210-PC)

Sagavanirktok 

A-1, 

69°01.4V 

147°00.1'

Sagavanirktok 

A-1, 

69°01'OOV 

147°00.8'

Mt. Michelson 

A-5, 

69°09.5V 

146°56.9'

Wahoo Limestone, 

15 m above base of 

lower member

Wahoo Limestone, 

about 139.5 m 

above base of 

lower member

Wahoo Limestone, 

155 m above base 

of lower member

Wahoo Limestone, 

stratigraphic level 

not known

Wahoo Limestone, 

106 m below 

contact with 

Echooka Formation

Thick- to medium-bedded, 

pelmatozoan-bryozoan 

packstone/wackestone 

containing abundant gray 

chert.

Sample is mottled and 

contains two 

microlithofacies: (1) 

bryozoan-echinoderm 

grainstone containing rare 

trilobite and brachiopod 

fragments and peloids, 

spiculitic wackestone 

intraclasts, and detrital 

quartz and (2) spiculitic 

wackestone containing 

minor ostracodes, 

calcispheres, and 

brachiopod, echinoderm, 

and bryozoan frond 

fragments.

Massive to thick-bedded 

bryozoan wackestone 

containing minor 

pelmatozoans, articulated 

brachiopods, and rare 

bivalves.

Light-medium-gray, 

massive- to mediumbedded (beds 15-50 cm 

thick), skeletalpelmatozoan packstonegrainstone containing 

silicified skeletal grains 

including articulated 

crinoids.

Massive- to thick-bedded, 

skeletal-pelmatozoan 

packstone.

1 Pa element Adetognathus lautus (Gunnell) 

10 Pa elements Cavusgnathus unicornis 

Youngquist and Miller 

7 Pa element fragments of cavusgnathoids 

Hindeodus aff. H. minutus (Ellison) 

2 Pa and 4 Pb elements 

Kladognathus sp. indet. 

5 P, 2 Sa, and 1 Sb-Sc elements 

UNASSIGNED ELEMENTS:

5 Pb (2 morphotypes), 6 M (3 morphotypes), 

1 Sb, and 4 Sc (2 morphotypes) 

49 indet. bar, blade, and platform fragments

26 Pa elements Cavusgnathus? tytthus Brown 

and Rexroad 

1 Pa element Gnathodus bilineatus bilineatus 

(Roundy) 

7 Pa elements Gnathodus girtyi girtyi Mass 

7 Pa elements Gnathodus girtyi simplex Dunn 

7 Pa elements Rhachistognathus muricatus 

(Dunn) 

1 juvenile Pa element Rhachistognathus prolixus 

Baesemann and Lane 

2 Pa elements Rhachistognathus websteri 

Baesemann and Lane 

69 Pa elements Vogelgnathus postcampbelli 

(Austin and Husri) 

UNASSIGNED ELEMENTS:

25 Pa (fragments), 6 Pb, 1 M, and 2 Sc 

161 indet. bar, blade, and platform fragments

Declinognathodus noduliferus japonicus 

(Igo and Koike) 

1 00 Pa, 4 M, and 1 Sc elements 

3 juvenile Pa elements of Gnathodus girtyi 

simplex (Dunn) 

1 M element Gnathodus sp. indet. 

42 gnathodontid Pa element fragments 

Hindeodus minutus (Ellison) 

2 Pa (fragments), 1 M, and 1 Sb elements 

7 Pa elements Vogelgnathus postcampbelli 

(Austin and Husri) 

UNASSIGNED ELEMENTS:

3 Pb (3 morphotypes) and 3 M 

84 indet. bar, blade, and platform fragments

5 Pa elements Cavusgnathus? tytthus Brown 

and Rexroad 

2 Pa element fragments of cavusgnathoids 

1 Pa element Gnathodus girtyi simplex Dunn 

1 Sb element Hindeodus sp. indet. 

1 Pa element Rhachistognathus primus Dunn 

UNASSIGNED ELEMENTS:

1 Pb and 1 Sc 

6 indet. bar, blade, and platform fragments

5 Pa element fragments Adetognathus sp. indet. 

8 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

1 1 Pa elements Rhachistognathus minutus 

havlenai Baesemann and Lane 

5 Pa elements Rhachistognathus primus Dunn 

transitional to R. muricatus (Dunn) 

35 Pa element fragments Rhachistognathus 

spp. indet. 

61 indet. bar, blade, and platform fragments

Upper R. muricatus 

Subzone (very late 

Chesterian)

D. noduliferus-R. 

primus Zone, probably 

lower part of zone 

(very earliest 

Morrowan)

lower D. noduliferusR. primus Zone (very 

earliest Morrowan)

R. minutus Fauna 

(early, but not earliest 

Morrowan to early 

Atokan, most likely 

early to middle 

Morrowan)

Postmortem transpor

within or from the 

cavusgnathid biofacies

shallow- to moderate

probably normal-ma

depositional environm

Probable postmortem 

transport within or fro

vogelgnathid-cavusgna

biofacies; normal-ma

near-restricted depos

environment.

Declinognathodid; ope

marine depositional 

environment, near wav

(virtually all ramifo

elements have been wi

away).

Indeterminate (too few 

conodonts).

Postmortem transpor

within the rhachistog

biofacies; high-energ

shallow-water, proba

shoal depositional 

environment.
APPENDIX 1. CONODONT FAUNAS, BIOFACIES, AND AGE AND LITHOLOGY OF COLLECTI

BUT NOT DESCRIBED ELSEWHERE IN THIS REPORT—CONTINUE

MAP LOG. NO., 

FIELD NO. 

(USGSCOLLN. 

NO.)

loc. 4C1b, 

KW90A-68 

(31211-PC)

loc. 4C1c, 

KW90A-105.3 

(31212-PC)

loc. 4D, 

KW90B-4.5 

(31213-PC)

loc. 4E, 

87KW2-0.0 

(30184-PC)

QUADRANGLE, 

LATITUDE Ny 

LONGITUDE W.

Mt. Michelson 

A-5, 

69°09.57 

146°56.9'

Sagavanirktok 

A-1, 

69°02V 

147°03.5'

Mt. Michelson 

A-5, 

69°01.27 

146°56. 2'

FORMATION

Wahoo Limestone, 

64 m below 

contact with 

Echooka Formation

Wahoo Limestone, 

27 m below 

contact with 

Echooka Formation

Wahoo Limestone, 

4.5 m below top of 

upper member

Top of Wahoo 

Limestone

UTHOLOGY

Massive- to thick-bedded, 

skeletal-pelmatozoan 

packstone to grainstone 

containing brachiopods.

Bryozoan-echinoderm 

packstone containing minor 

grains of foraminifers, 

brachiopods, intraclasts, 

superficial ooids, and 

peloids. Grains are 

strongly recrystallized, 

poorly sorted, and 

moderately abraded.

Recrystallized limestone; 

the only recognizable 

grains are common 

echinoderms, indeterminate 

bioclasts, and rare quartz.

Bryozoan-pelmatozoan 

grainstone containing 

micritized intraclasts of 

spiculitic mudstone and 

relatively large ramose and 

fenestrate bryozoans, 

corals, and brachiopods.

OONODONTS

2 Pa elements Adetognathus lautus (Gunnell) 

2 Pa elements Adetognathus spathus (Dunn) 

2 Pa element fragments Adetognathus sp. indet. 

4 Pa elements Declinognathodus noduliferus 

noduliferus (Ellison and Graves) 

1 Sa element Idioprioniodus sp. indet. 

3 Pa elements Rhachistognathus minutus 

havlenai Baesemann and Lane 

1 Pa element Rhachistognathus minutus minutus 

(Higgins and Bouckaert) 

4 Pa elements Rhachistognathus primus Dunn 

35 Pa element fragments Rhachistognathus 

spp. indet. 

1 unassigned Sc element 

24 indet. bar, blade, and platform fragments

1 Pa element Adetognathus lautus (Gunnell) 

3 Pa elements Declinognathodus noduliferus 

noduliferus (Ellison and Graves) 

Idioprioniodus sp. indet. 

1 M and 1 Sb? elements 

2 Pa elements Rhachistognathus minutus 

dedinatus Baesemann and Lane

10 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) 

9 Pa Declinognathodus noduliferus noduliferus 

(Ellison and Graves) 

5 Pa elements Idiognathodus sinuosus Ellison 

and Graves 

43 indet. bar, blade, and platform fragments

2 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) 

5 Pa elements Rhachistognathus minutus 

dedinatus Baesemann and Lane 

2 Pa element fragments Rhachistognathus sp. 

indet. 

1 unassigned Sb element 

6 indet. bar, blade, and platform fragments

A3E

R. minutus Fauna 

(early, but not earliest 

Morrowan to early 

Atokan, most likely 

early to middle 

Morrowan)

Idiognathodus Fauna 

(late Morrowan to 

early Desmoinesian, 

probably no younger 

than early Atokan)

early Morrowan (no 

older than lower 

minutus Fauna) to 

early Atokan

BIOFA

Postmortem tra

within the rhac

biofacies; high

shallow-water, 

shoal deposition

environment.

Indeterminate (

conodonts); mic

indicates open

near-shoal dep

environment.

Declinognathod

marine deposit

environment.

Indeterminate (

conodonts); mi

indicate redepo

grainstone (sto

interbedded wit

argillaceous lim

Franklin Mountains

loc. 5a, 

SKM91C-10 

(31824-PC)

Mt. Michelson 

A-5, 

69°07.67 

146°26.0'

Lower member of 

Wahoo Limestone, 

299.5 m below 

contact between 

Wahoo and Echooka 

Formation

Thick- to medium-bedded 

bryozoan 

packstone/wackestone .

69 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike), some transitional to Gnathodus girtyi simplex Dunn 

3 Pa elements Hindeodus minutus (Ellison) 

1 Pa element Rhachistognathus prolixus 

Baesemann and Lane 

1 1 Pa elements Vogelgnathus postcampbelli 

(Austin and Husri) 

UNASSIGNED ELEMENTS:

3 Pb and 5 Sc (3 morphotypes) 

56 indet. bar, blade, and platform fragments

D. noduliferus- R. 

primus Zone (lower 

part of zone on the 

basis of Gnathodus 

girtyi simplex in 

sample 80 m higher in 

section)

Declinognathod

open-marine de

environment, n

wave base.
loc. 5b, 

SKM91C-90 

(32222-PC)

loc. 5c, 

SKM91C-175.5 

(32231-PC)

loc. 5d, 

SKM91C-187 

(31860-PC)

loc. 5e, 

SKM91C-219 

(32232-PC)

loc. 5f, 

SKM91C-309.5 

(32233-PC)

Mt. Michelson 

A-5, 

69°07.6V 

146°26.0'

Lower member of 

Wahoo Limestone, 

219.5 m below 

contact between 

Wahoo and Echooka 

Formation

Lower member of 

Wahoo Limestone, 

134 m below 

contact between 

Wahoo and Echooka 

Formation

Lower member of 

Wahoo Limestone, 

122.5 m below 

base of Echooka 

Formation

Lower member of 

Wahoo Limestone, 

90.5 m below base 

of Echooka 

Formation

Upper member of 

Wahoo Limestone, 

49.5 m above base

Coarse-grained bryozoan 

and pelmatozoan 

grainstone-packstone 

containing minor algae and 

rare foraminifers and 

trilobite fragments; 

moderately abraded and 

poorly sorted.

Bryozoan and pelmatozoan 

packstone-grainstone 

containing minor 

brachiopod and bivalve 

fragments, intraclasts, and 

detrital clasts; moderately 

abraded and poorly sorted.

Bryozoan and pelmatozoan, 

superficial ooid grainstone 

containing minor 

brachiopod, bivalve, and 

algal fragments; strongly 

abraded and well sorted.

Bryozoan and pelmatozoan 

grainstone; moderately 

abraded and sorted.

Oolitic, brachiopod, bivalve 

grainstone containing 

minor bryozoan and 

pelmatozoan fragments, 

gastropods, superficial 

ooids, and intraclasts; 

moderately abraded and 

very poorly sorted.

1 Pa element Cavusgnathus? tytthus Brown 

and Rexroad 

8 Pa elements Declinognathodus noduliferus 

noduliferus (Ellison and Graves) 

1 Pa element Gnathodus girtyi simplex Dunn 

1 Pa element Hindeodus sp. indet. 

2 Sb-Sc elements Kladognathus sp. 

2 Pa elements Rhachistognathus muricatus 

(Dunn) 

UNASSIGNED ELEMENTS5 Pa, 4 Pb, 1 M, and 2 Sc 

21 indet. bar, blade, and platform fragments

1 Pa element Adetognathus lautus (Gunnell) 

1 idioprioniodid element 

2 Pa elements Rhachistognathus minutus 

minutus (Higgins and Bouckaert)? 

33 Pa elements Rhachistognathus muricatus 

(Dunn) 

2 Pa elements Rhachistognathus websteri 

Baesemann and Lane 

1 1 Pa elements Rhachistognathus sp. indet. 

10 indet. bar, blade, and platform fragments

5 Pa elements Gnathodus defectus Dunn 

Idioprioniodus conjunctus (Gunnell) 

1 Pa, 3 Pb, 1 M, 4 Sa, 1 Sb, and 3 Sc elements 

2 Pa elements Rhachistognathus minutus 

havlenai Baesemann and Lane 

3 Pa elements Rhachistognathus minutus 

minutus Baesemann and Lane 

59 Pa elements Rhachistognathus muricatus 

(Dunn) 

15 Pa elements Rhachistognathus websteri 

Baesemann and Lane 

UNASSIGNED ELEMENTS2 M (2 morphotypes) 

121 indet. bar, blade, and platform fragments

6 Pa elements Adetognathus lautus (Gunnell) 

1 Pa element Hindeodus sp. indet. 

2 idioprioniodid elements 

18 Pa elements Rhachistognathus minutus 

subspp. 

14 Pa elements Rhachistognathus muricatus 

(Dunn) 

6 Pa elements Rhachistognathus websteri 

Baesemann and Lane 

1 Pa element fragment Declinognathodus 

noduliferus noduliferus (Ellison and Graves)? 

10 Pa element fragments Rhachistognathus spp. 

indet. 

54 indet. bar, blade, and platform fragments

1 Pa element Adetognathus. lautus (Gunnell)? 

1 Pa element Declinognathodus noduliferus 

japonicus (Igo and Koike) 

1 juvenile Pa element Idiognathodus sp. indet. 

1 Pb? element Idioprioniodus sp. indet. 

3 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

2 Pa elements Rhachistognathus minutus 

havlenai Baesemann and Lane 

1 Pa element Rhachistognathus minutus minutus 

(Higgins and Bouckaert) 

47 indet. bar, blade, and platform fragments

D. noduliferus-R. 

primus Zone (lower 

part of zone? on the 

basis of Gnathodus 

girtyi simplex )

lower Ft. minutus Fauna 

(Morrowan, but not 

earliest Morrowan)

Idiognathodus Fauna 

(late Morrowan to 

early Atokan)

Indeterminate (too few 

conodonts); relatively 

shallow-water, norm

marine depositional 

environment.

Postmortem transpor

or within the 

rhachistognathid biofa

normal-marine, poss

shoal-apron depositio

environment.

Indeterminate (too few 

conodonts); normal-m

shallow-water, proba

high-energy depositio

environment. Micro

facies indicates a sto

induced spill-over lob
APPENDIX 1. CONODONT FAUNAS, BIOFACIES, AND AGE AND LITHOLOGY OF COLLECT

BUT NOT DESCRIBED ELSEWHERE IN THIS REPORT—CONTINU

MAP LOG. NO., 

FIELD NO. 

(USGSCOLLN. 

NO.)

loc. 6, 

87PG-F-112.0 

(30266-PC)

QUADRANGLE, 

LATITUDE N7 

LONGITUDE W.

Ml. Michelson 

B-4, 

69°15.17 

146°10.6'

FORMATION

Uppermost part of 

lower member of 

Wahoo Limestone, 

within upper 0.5 

m

LTTHOLOGY

Pelmatozoan packstone 

containing common ooids, 

bryozoans, intraclasts and 

minor peloids, algae, 

trilobites, foraminifers, 

gastropods, bivalves, and 

bryozoans.

CONODONTS

14 Pa elements Cavusgnathus? tytthus Brown and 

Rexroad 

1 8 Pa element fragments of cavusgnathoids 

1 Sc element Hindeodus minutus (Ellison) 

6 indet. bar, blade, and platform fragments

AGE

Upper muricatus 

Subzone to lower 

noduliferus-primus 

Zone (very latest 

Chesterian to very 

earliest Morrowan)

BIO

Cavusgnathid 

relatively s

probably ne

depositional 

Fourth Range

loc. 7a, 

AK90A-353 

(32473-PC)

loc. 7b, 

AK90A-490 

(31838-PC)

Ml. Michelson 

B-3, 

69°21.1V 

145°38.7'

Wahoo Limestone, 

lower member, 49 

m above contact 

with Alapah 

Limestone and 

19.5 m below 

lowest 

Pennsylvanian 

collection in the 

section

Wahoo Limestone, 

117.5 m above 

base of upper 

member and 

immediately below 

contact with 

Echooka Formation

Slightly dolomitic 

bryozoan-pelmatozoan 

packstone containing chert 

replacement grains; minor 

grain types include 

fenestrate bryozoans, and 

brachiopods.

Oolitic grainstone 

containing abundant 

superficial ooids and minor 

pelmatozoans, bryozoans, 

foraminifers, bivalves, 

ostracodes, and intraclasts.

26 Pa elements Gnathodus girtyi girtyi Mass 

15 Pa elements Gnathodus girtyi simplex Dunn 

Hindeodus minutus (Ellison) 

4 Pa, 3 M, 1 Sb, and 1 Sc elements 

Idioprioniodus sp. indet. 

1 Sb and 1 Sc elements 

Kladognathus sp. indet. 

1 P and 1 Sb-Sc element fragments 

1 36 Pa elements Vogelgnathus postcampbelli 

(Austin and Husri) 

165 indet. bar, blade, and platform fragments

4 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) 

19 Pa elements Declinognathodus noduliferus 

noduliferus (Ellison and Graves) 

1 Pa element Idiognathodus incurvus Dunn? 

36 Pa elements Idiognathodus sinuosus Ellison 

and Graves (subadult and abraded 

specimens) 

2 Idioprioniodus sp. indet. elements 

1 unassigned Pb element 

40 indet. bar, blade, and platform fraqments

late Chesterian

Idiognathodus Fauna 

(early Atokan to early 

Desmoinesian?)

Postmortem 

or from the 

gnathodid bi

marine depo

environment

Idiognathodi

declinognath

normal-mari

depositional 

Shublik Mountains

loc. 8, 

89MR-36A 

(30895-PC)

Mt. Michelson 

B-4, 

69°29.37 

145°54.5'

Uppermost part of 

Wahoo Limestone

Medium-grained bioclastic 

grainstone.

1 Pa element Adetognathus lautus (Gunnell) 

4 Pa element fragments Adetognathus sp. indet. 

1 Pa element Hindeodus minutus (Ellison) 

1 juvenile Pa element Idiognathodus sp. indet. 

9 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

1 unassigned M element 

16 indet. bar, blade, and platform fragments

Idiognathodus Fauna 

(late Morrowan to 

early Atokan)

Indeterminat

conodonts).

Romanzof Mountains

loc. 9A, 

88KWF-0.0 

(30277-PC)

Demarcation 

Point B-4, 

69°23.1Y 

143°02.7'

Wahoo Limestone, 

1 m below contact 

with Echooka 

Formation

Oolitic, pelmatozoan 

grainstone containing 

strongly abraded and wellsorted grains.

3 Pa fragments Adetognathus lautus (Gunnell) 

1 Pa element Declinognathodus noduliferus 

japonicus (Igo and Koike) 

1 Pa element fragment Idiognathodus sp. indet. 

5 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

2 rhachistognathid Pa element fragments 

UNASSIGNED ELEMENTS:

1 M 

30 indet. bar, blade, and platform fragments

Idiognathodus Fauna 

(late Morrowan to 

early Atokan)

Indeterminat

conodonts). 

indicates a s

environmen
loc. 9B1a, 

ME92C-776 

(32228-PC)

loc. 9B1b, 

ME92C-974.5 

(32229-PC)

Demarcation 

Point A-3, 

69°08.7V 

142°18.2'

Alapah Limestone, 

776 m above base

Wahoo Limestone, 

39.5 m above base

Bryozoan packstone.

Pelmatozoan packstone.

2 Pa elements Cavusgnathus unicomis 

Youngquist and Miller 

2 Pa element fragments of cavusgnathoids 

1 Pb element Idioprioniodus cf. /. healdi 

(Roundy) 

1 Pb element Idioprioniodus sp. indet. 

1 Sb-Sc element Kladognathus sp. 

1 Pa element Rhachistognathus muricatus 

(Dunn) 

1 Pa element Rhachistognathus prolixus 

Baesemann and Lane 

2 rhachistognathid?Pa elements 

33 indet. bar. blade, and platform fragments

26 Pa elements Cavusgnathus unicomis Youngquist and Miller (juveniles and adults) 

32 Pa element fragments of cavusgnathoids 

1 1 Pa elements Gnathodus girtyi girtyi Mass 

2 Pa elements Gnathodus girtyi simplex Dunn 

13 Pa elements Gnathodus girtyi subspp. 

(12 juveniles) 

1 idioprioniodid element 

Kladognathus sp. indet. 

1 P, 1 M, 2 Sa, and 6 Sb-Sc elements 

1 kladognathid element 

6 Pa elements Rhachistognathus muricatus 

(Dunn) 

24 Pa elements Vogelgnathus postcampbelli 

(Austin and Husri) 

UNASSIGNEP ELEMENTS'

2 Pb and 1 M 

187 indet. bar, blade, and platform fragments

R. muricatus Zone 

(very late Chesterian)

Indeterminate (too f

conodonts); shallow

normal-marine, mo

to high-energy depo

environment.

Normal-marine, op

platform to near pa

restricted deposition

environment.

British Mountains, Clarence River area

loc. lOAla, 

KW91Y+0.5 

(31795-PC)

loc. 10A1b, 

KW91Y+44 

(31796-PC)

loc. 10A1c, 

KW91Y+89 

(31798-PC)

Demarcation 

Point B-1, 

69°25.5V 

141°04.1'

Alapah Limestone, 

0.5 m above base 

of section and 52.8 

m below contact 

with Wahoo 

Limestone

Upper part of 

Alapah 

Limestone, 9.3 m 

below contact with 

Wahoo Limestone

Lower member of 

Wahoo Limestone, 

35.7 m above base 

of formation

Dark-gray to black, 

massive, full-frond 

bryozoan 

wackestone/bafflestone; 

bedding indistinct and 

irregular.

Medium-gray, bloclastic, 

crinoidal packstone.

Brownish-gray to mediumgray, bloclastic, 

pelmatozoan packstoneqrainstone.

4 Pa elements Adetognathus lautus (Gunnel!) 

13 Pa elements Cavusgnathus unicomis 

Youngquist and Miller 

5 Pa fragments of cavusgnathoids 

Hindeodus minutus (Ellison) 

3 Pa, 1 Pb, 1 M, 1 Sa, 5 Sb, and 2 Sc elements 

1 Sb-Sc element Kladognathus sp. indet. 

1 Pa element Vogelgnathus postcampbelli 

(Austin and Husri) 

UNASSIQNED ELEMENTS'

5 Pb, 12 M (3 morphotypes), 1 Sb, and 1 Sc 

63 indet. bar. blade, and platform fragments

2 Pa elements Adetognathus lautus (Gunnell) 

82 Pa elements Cavusgnathus unicomis 

Youngquist and Miller 

66 Pa element fragments of cavusgnathoids 

3 Pa elements Cavusgnathus? tytthus Brown 

and Rexroad 

20 Pa elements Gnathodus girtyi simplex Dunn 

Hindeodus minutus (Ellison) 

2 Pa, 1 Sa, and 1 Sc elements 

Kladognathus sp. 

7 M and 14 Sb-Sc elements 

2 Pa elements Vogelgnathus postcampbelli 

(Austin and Husri) 

UNASSIGNED ELEMENTS3 Pb and 4 M (3 morphotypes) 

-250 indet. bar, blade, and platform fragments

1 Pa element Cavusgnathus!? tytthus Brown and 

Rexroad 

2 Pa cavusgnathoid fragments 

2 indet. bar, blade, and platform fragments

Upper R. muricatus 

Subzone (very latest 

Chesterian)

Postmortem winnow 

within the cavusgna

-hindeodid biofacies

relatively shallow w

near intermittently

restricted deposition

environment.

Cavusgnathid-gnath

shallow to moderate 

depth, probably no

marine depositional 

environment.

Indeterminate (too f

conodonts); probab

shallow-water depo

environment.
APPENDIX 1. CONODONT FAUNAS, BIOFACIES, AND AGE AND LITHOLOGY OF COLLECTI

BUT NOT DESCRIBED ELSEWHERE IN THIS REPORT—CONTINUE

MAP LOG. NO., 

FIELD NO. 

(USGSCOLLN. 

NO.)

loc. 10A1d, 

KW91Y+115 

(31799-PC)

loc. 10A1e, 

KW91Y+132.5 

(31800-PC)

loc. 10A1f, 

SKM92B-196.4 

(32230-PC)

loc. 10A1g, 

KW91Y+347.6 

(31805-PC)

loc. 10A1h, 

KW91Y+TOP 

(31806-PC)

loc. 10B, 

85TR83A1 

(29888-PC)

QUADRANGLE, 

LATITUDE N7 

LONGITUDE W.

Demarcation 

Point B-1, 

69°25.5V 

141°04.1'

Demarcation 

Point, 

69°25.0V 

141°00.0'

FORMATION

Lower member of 

Wahoo Limestone, 

61 .7 m above base 

of formation

Lower member of 

Wahoo Limestone, 

79.2 m above base 

of formation

Upper member of 

Wahoo Limestone, 

196.4 m above 

base of formation 

and 79.4 m above 

base of upper 

member

Upper member of 

Wahoo Limestone, 

294.3 m above 

base of formation 

and 124 m above 

base of upper 

member

Wahoo Limestone, 

upper member, 

about 8-10 m 

below contact with 

Echooka 

Formation; 

distance above base 

of section 

uncertain

Near top of 

Lisbume Group

LITHOLOGY

Massive, medium-gray, 

bioclastic packstonegrainstone; skeletals 

locally silicified and 

include crinoids (some 

articulated columnals) and 

brachiopods.

Light-medium-gray, 

bioclastic packstone; 

skeletals include crinoids 

and ramose bryozoans; 

contains possible 

superficial ooids and 

crossbeds.

Oolitic, bryozoan, 

pelmatozoan, intraclastic 

grainstone containing 

minor algal, gastropod, and 

triloblte fragments; 

strongly abraded and 

moderately sorted.

Crinoidal packstone 

containing 30-40 percent 

chert in nodules and bands.

Osagia? grainstone.

Olive- to dark-gray, finegrained limestone.

CCNODONTS

1 1 Pa elements Cavusgnathus unicomis 

Youngquist and Miller 

3 Pa elements Gnathodus girtyi simplex Dunn 

17 indet. bar, blade, and platform fragments

1 1 Pa elements Cavusgnathus unicomis 

Youngquist and Miller 

1 cavusgnathoid Pa element fragment 

2 Pa elements Gnathodus girtyi simplex Dunn 

1 Pa element Hindeodus minutus (Ellison) 

1 Sa and 1 Sb-Sc elements Kladognathus sp. 

10 indet. bar, blade, and platform fraqments

8 Pa elements Adetognathus lautus (Gunnell) 

3 Pa elements Cavusgnathus? tytthus Brown 

and Rexroad ' 

3 Pa elementsDec//nognaf/7odus inaequalis 

(Higgins) 

4 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

3 Pa elements Rhachistognathus minutus 

havlenai Baesemann and Lane 

1 Pa element Rhachistognathus minutus minutus 

Baesemann and Lane 

4 Pa elements Rhachistognathus minutus subspp. 

indet. 

8 Pa elements Rhachistognathus muricatus 

(Dunn) (2 R. websteri morphotypes) 

52 indet. bar, blade, and platform fraqments

8 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike) 

9 Pa elements Idiognathodus sp. indet. (juveniles 

and incomplete adults) 

1 Pa element Rhachistognathus minutus 

subsp. indet. 

1 unassigned Sc element 

68 indet. bar, blade, and mostly platform 

fraqments

16 Pa elements Adetognathus lautus (Gunnell) 

1 juvenile Pa element fragment Idiognathodus 

sp. indet. 

1 Pa element Rhachistognathus minutus havlenai 

Baesemann and Lane 

UNASSIGNED ELEMENTS:

2 Pb (2 morphotypes) and 2 Sc 

10 indet. bar, blade, and platform fraqments

8 Pa elements Adetognathus lautus (Gunnell) 

5 Pa elements Declinognathodus noduliferus 

japonicus (Igo and Koike)? 

24 Pa elements Idiognathodus sinuosus Ellison 

and Graves 

1 Pa element fragment Idiognathodus sp. indet. 

3 element fragments Idioprioniodus sp. indet. 

10 Pa elements Rhachistognathus minutus 

declinatus Baesemann and Lane 

2 unassigned Pb elements 

+100 indet. bar, blade, and platform fraqments

AGE

Upper R. muricatus 

Subzone (very latest 

Chesterlan)

lower minutus Fauna 

(early, but not earliest 

Morrowan)

Idiognathodus Fauna 

(late Morrowan to 

early Atokan)

Idiognathodus Fauna 

(late Morrowan to 

early Atokan)

BIOF

Indeterminate 

conodonts); p

postmortem t

cavusgnathid 

deposited in r

shallow or mo

depths.

Indeterminate 

conodonts); n

depositional e

Rhachistogna

adetognathid b

Relatively sha

probably near

open-platform 

environment, m

hiqh energy.

Idiognathodiddeclinognathod

normal-marine

at least moder

depositional e

Adetognathid 

shallow to mod

normal-marine 

environment.

Idiognathodid

rhachistognat

marine depos

environment, 

shoal.
PLATES 1-5
PLATE 1

Conodonts from the Wahoo Limestone, eastern Sadlerochit Mountains,

northeast Brooks Range, Alaska.

[Scanning electron microscope photomicrographs of specimens coated 

with carbon and gold. Meters shown are above base of formation]

Figures 1-6. Hindeodus minutus (Ellison), X50, lower member.

1. Pa element, outer lateral view, 42 m (USGS colln. 30754-PC), 

USNM442115.

2. Pb element, inner lateral view, 69 m (USGS colln. 30762-PC),

USNM442116. 

3-4. M and Sa elements, posterior and lateral views, 53 m (USGS colln.

30757-PC), USNM 442117-118. 

5-6. Sb and Sc elements, lateral views, 69 m (USGS colln. 30762-PC),

USNM 442119-20. 

7-12. Cavusgnathus! tytthus Brown and Rexroad, Pa elements, lower member.

7-8. a morphotype, oblique upper and upper views, 56 m (USGS colln.

30758-PC), USNM 442121-122; figure 7, X50 and figure 8, X35. 

9-10. p morphotype, X50, upper and lateral views of specimen with 

left-trending carinal extension of blade, 22 m (USGS colln. 30750- 

PC), USNM 442123.

11-12. Y morphotype, X50, lower and upper views of specimen with 

central free blade and carina, 50.5 m (USGS colln. 30756-PC), 

USNM 442124. 

13-15, 21-24. Adetognathus lautus (Gunnell), Pa elements, X50, upper member.

13. Left element with short, right-trending carinal extension of blade,

lateral view, 113 m (USGS colln. 30775-PC), USNM 442125. 

14-15. Left elements with right-trending carinal extension of blade, upper 

views, 107 m (USGS colln. 30774-PC), USNM 442126-27.

21. Right element, upper view, 85 m (USGS colln. 30768-PC), USNM 

442130.

22. Right element, inner lateral view, 91 m (USGS colln. 30770-PC), 

USNM 442131.

23. Left element, upper view, 133.5 m (USGS colln. 30778-PC), 

USNM 442132.

24. Left element, upper view, 85 m (USGS colln. 30768-PC), USNM

442133. 

16-20, 25-26. Adetognathus spathus (Dunn), Pa elements, upper member.

16-18. Right element, upper, lower, and inner lateral views, 157 m (USGS 

colln. 30781-PC), USNM 442128; figure 16, X50 and figures 17- 

18.X40. 

19-20. Left element, upper and outer lateral views, X50, 157 m (USGS

colln. 30781-PC), USNM 442129. 

25-26. Left element, upper and oblique lower views, X50, 246 m (USGS

colln. 30795-PC), USNM 442134. 

27. Cavusgnathus altus Harris and Hollingsworth, Pa element, X50, upper

view, lower member, 7 m (USGS colln. 30747-PC), USNM 442135. 

28-31. Cavusgnathus unicornis Youngquist and Miller, Pa elements, lower 

member. 

28-30. Y morphotype, upper, lower, and inner lateral views, X35, 22 m

(USGS colln. 30750-PC), USNM 442136.

31. a morphotype, inner lateral view, x50, 50.5 m (USGS colln. 

30756-PC), USNM 442137.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 PLATE 1

ADETOGNATHUS, CAVUSGNATHUS, CAVUSGNATHUS1, AND HINDEODUS
PLATE 2

Conodonts from the Wahoo Limestone, eastern Sadlerochit Mountains,

northeast Brooks Range, Alaska.

[Scanning electron microscope photomicrographs of specimens coated 

with carbon and gold. Meters shown are above base of formation]

Figures 1-17. Cavusgnathus unicornis Youngquist and Miller, lower member.

1-2. Pa element, y morphotype, inner lateral and upper views,

X50, 6 m (USGS colln. 30746-PC), USNM 442138. 

3. Pa element, juvenile, X50, upper view, 13.2 m (USGS colln.

30748-PC), USNM 442139. 

4-7. Pa elements, upper and inner lateral views, 7 m (USGS

colln. 30747-PC).

4-5. a morphotype, X50, USNM 442140. 

6-7. |3 morphotype, X45, USNM 442141. 

8-9. Pa element, a morphotype, X40, outer and inner lateral

views, 42 m (USGS colln. 30754-PC), USNM 442142. 

10-12, 14-17. 0.4 m (USGS colln. 30745-PC).

10-12. Pa elements, inner lateral, upper, and inner lateral views. 

10-11. y morphotype, X45, USNM 442143.

12. a? morphotype, X50, USNM 442144. 

14-15. Two Sc elements, X30, lateral views, USNM 442146-47.

16. Pb element, X40, lateral view, USNM 442148.

17. M element, X50, lateral view, USNM 442149.

13. Pa element, X45, upper view, 22 m (USGS colln. 30750-

PC), USNM 442145.

18-19. Gnathodus bilineatus bilineatus (Roundy), Pa elements, X50, upper views, 

lower member.

18. Left element, 37 m (USGS colln. 30753-PC), USNM

442150.

19. Right element, 7 m (USGS colln. 30747-PC), USNM

442151. 

20-22. Gnathodus girtyi girtyi Hass, right Pa elements, X50, lower member.

20-21. Upper and lower views, 53 m (USGS colln. 30757-PC),

USNM 442152. 

22. Upper view, 32 m (USGS colln. 30752-PC), USNM

442153. 

23-24, 31-33. Gnathodus defectus Dunn, Pa elements, X75, upper member.

23-24. Left and right elements, upper views, 102 m (USGS colln.

30773-PC), USNM 442154-155. 

31-33. Right element, upper, lower, and inner lateral views, 85 m

(USGS colln. 30768-PC), USNM 442160. 

25-27. Gnathodus girtyi simplex Dunn, X50, right Pa elements, lower member.

25. Upper view, 32 m (USGS colln. 30752-PC), USNM

442156.

26-27. Upper and lower views, 37 m (USGS colln. 30753-PC), 

USNM 442157.

28. Gnathodus sp. indet, M element, X50, inner lateral view, lower member, 53 

m (USGS colln. 30757-PC), USNM 442158.

29. Gnathodus girtyi girtyi Hass transitional to Declinognathodus inaequalis 

(Higgins), right Pa element, X40, upper view, lower member, 69 m (USGS 

colln. 30762-PC), USNM 442159.

30. Gnathodus girtyi simplex Dunn transitional to Declinognathodus 

noduliferus japonicus (Igo and Koike), left Pa element, X50, upper view, 

lower member, 54.9 m (USGS colln. 31698-PC), USNM 483406.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 PLATE 2

CAVUSGNATHUS AND GNATHODUS
PLATE 3

All conodonts from the Wahoo Limestone at study section, 

eastern Sadlerochit Mountains, northeast Brooks Range, Alaska,

except figure 31, which is from I km to the west.

[Scanning electron microscope photomicrographs of specimens coated

with carbon and gold. Meters shown are above base of formation]

Figures 1-8, 19-22. Declinognathodus noduliferus japonicus (Igo and Koike), Pa elements. 

1-8. Right Pa elements, lower member. 

1-2. Upper and lower views, X40, 62 m (USGS colln. 30760-PC), USNM

442161.

3. Upper view, X50, 59 m (USGS colln. 30759-PC), USNM 442162. 

4-8. Figures 4-6 upper views, 7-8 upper and lower views, X50, 56 m

(USGS colln. 30758-PC), USNM 442163-166. 

19-22. Upper member.

19-20. Left element, X40, lower and upper views (blade broken during SEM 

preparation), 207 m (USGS colln. 30789-PC), USNM 442175.

21. Right element, X50, upper view, 250 m, (USGS colln. 30796-PC), 

USNM 442176.

22. Right element, X50, upper view, 207 m (USGS colln. 30789-PC),

USNM 442177.

9. Declinognathodus noduliferus japonicus (Igo and Koike) transitional to D. n. 

noduliferus (Ellison and Graves), right Pa element, X50, upper view, lower 

member, 62 m (USGS colln. 30760-PC), USNM 442167.

10-14, 32. Declinognathodus noduliferus noduliferus (Ellison and Graves), Pa elements, 

upper views, X50, upper member.

10. Right element, juvenile, 113 m (USGS colln. 30775-PC), USNM 

442168.

11. Left element, 85 m (USGS colln. 30768-PC), USNM 442169.

12. Right element, 133.5 m (USGS colln. 30778-PC), USNM 442170.

13. Left element, 177 m (USGS colln. 30785-PC), USNM 442171.

14. Right element, 250 m (USGS colln. 30796-PC), USNM 442172. 

32. Left element (lateralis morphotype), 187 m (USGS colln. 30786-PC),

USNM 442184.

15-18, 23-25. Idiognathodus sinuosus Ellison and Graves, Pa elements, X50, upper member. 

15-16. Juvenile, upper and lower views, 207 m (USGS colln. 30789-PC),

USNM 442173. 

17-18. Lower and upper views, 187 m (USGS colln. 30786-PC), USNM

442174. 

23-25. Upper and upper and lower views, 207 m (USGS colln. 30789-PC),

USNM 442178-179.

26-27. Lochriea commutata (Branson and Mehl), X50, lower member, 6 m (USGS 

colln. 30746-PC).

26. Left Pa element, upper view, USNM 442180.

27. M element, lateral view, USNM 442181.

28-31 . Vogelgnathus postcampbelli (Austin and Husri), Pa elements, lower member. 

28-29. Lateral and lower oblique views, 13.2 m (USGS colln. 30748-PC), 

USNM 442182.

30. Lateral view, 53 m (USGS colln. 30757-PC), USNM 442183.

31. Lateral view, 55.3 m (USGS colln. 31836-PC, app. 1, loc. IBlg), 

USNM 483407. From Mississippian-Pennsylvanian boundary section 

1 km west of study section. Sample from 2.8 m above the first 

appearance of Declinognathodus noduliferus japonicus in the eastern 

Sadlerochit Mountains.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 PLATE 3

DECLINOGNATHODUS, IDIOGNATHODUS, LOCHRIEA, AND VOGELGNATHUS
PLATE 4

Conodonts from the Wahoo Limestone, eastern Sadlerochit Mountains, 

northeast Brooks Range, Alaska, except figure 26 from Pogopuk Creek section,

Franklin Mountains (see text-fig. 2).

[Scanning electron microscope photomicrographs of specimens coated 

with carbon and gold. Meters shown are above base of formation]

Figures 1-9. Rhachistognathus minutus declinatus Baesemann and Lane, Pa elements, X50, 

upper member.

1. Right element, upper view, 107 m (USGS colln. 30774-PC), USNM

442185.

2. Right element, upper view, 177 m (USGS colln. 30785-PC), USNM

442186. 

3—4. Right element, lower and upper views, with node on anterior part of inner

lobe, 187 m (USGS colln. 30786-PC), USNM 442187. 

5-6. Left element, lower and upper views, 187 m (USGS colln. 30786-PC),

USNM 442188.

7. Right element, upper view, with transverse ridge connecting node on inner 

lobe to parapet, 191.5 m (USGS colln. 30787-PC), USNM 442189.

8. Right element, upper view with node on inner lobe, 232 m (USGS colln. 

30793-PC), USNM 442190.

9. Right element, upper view, 85 m (USGS colln. 30768-PC), USNM

442191.

10-12. Rhachistognathus minutus havlenai Baesemann and Lane, Pa elements, X50, upper 

views, upper member. 

10-11. Right elements, 107 m (USGS colln. 30774-PC), USNM 442192-93.

12. Left element, 162 m (USGS colln. 30782-PC), USNM 442194.

13-15. Rhachistognathus minutus minutus (Higgins and Bouckaert), Pa elements, X50, 

upper member. 

13-14. Right elements, upper and lower views, 85 m (USGS colln. 30768-PC),

USNM 442195-96. 

15. Left? element, upper view, 107 m (USGS colln. 30774-PC), USNM

442197.

16. Rhachistognathus muricatus (Dunn) transitional to R. websteri Baesemann and 

Lane, X50, upper view, lower member, 6 m (USGS colln. 30746-PC), USNM 

442198.

17-21. Rhachistognathus websteri Baesemann and Lane, Pa elements, X50, upper 

member. 

17-19. Upper, lower, and upper views, 91 m (USGS colln. 30770-PC), USNM

442199-200.

20-21. Upper and lower views, 122 m (USGS colln. 30777-PC), USNM 442201. 

22-24. Rhachistognathus spp. indet., Pa elements, juveniles, lateral, upper, and lower 

views, upper member, 260.5 m (USGS colln. 30799-PC), USNM 442202-203.

25. Rhachistognathus muricatus (Dunn) transitional to R. primus Dunn, Pa element, 

X50, upper view, upper member, 95 m (USGS colln. 30771-PC), USNM 442204.

26. Cnathodus defectus Dunn, Pa element, X50, upper view, lower member, 154.5 m 

below base of overlying Echooka Formation (USGS colln. 31860-PC, app. 1, loc. 

5D), USNM 442205. In this collection, G. defectus occurs with three species of 

Rhachistognathus, including R. minutus, indicating the lower minutus Fauna. 

27-30. Rhachistognathus muricatus (Dunn), Pa elements, lower member.

27. Upper view, X50, 56 m (USGS colln. 30758-PC), USNM 442206. 

28-29. Upper and lower views, X50, 7 m (USGS colln. 30747-PC),

USNM 442207. 

30. Upper view, X40, 69 m (USGS colln. 30762-PC), USNM 442208.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 PLATE 4

RHACHISTOGNATHUS AND GNATHODUS
PLATE 5

Conodonts from the Wahoo Limestone, eastern Sadlerochit Mountains,

northeast Brooks Range, Alaska.

[Scanning electron microscope photomicrographs of specimens coated 

with carbon and gold. Meters shown are above base of formation]

Figures 1-10. Kladognathus spp. indet., lower member.

1. P element, X50, lateral view, 0.4 m (USGS colln. 30745-PC), USNM

442209.

2. P element, X50, lateral view, 6 m (USGS colln. 30746-PC), USNM

442210.

3. P element, X50, oblique view, 0.4 m (USGS colln. 30745-PC), USNM

442215.

4. P element, X50, oblique view, 42 m (USGS colln. 30754-PC), USNM

442216.

5. M element, X45, lateral view, 7 m (USGS colln. 30747-PC), USNM

442211.

6. M element, X30, lateral view, 6 m (USGS colln. 30746-PC), USNM

442212.

7. Sa element, X50, anterolateral view, 0.4 m (USGS colln. 30745-PC), 

USNM 442213.

8. Sa element, X50, posterior view, 37 m (USGS colln. 30753-PC), 

USNM 442214.

9. Sc element, X50, lateral view, 6 m (USGS colln. 30746-PC), USNM

442217. 

10. Sb element, X50, lateral view, 0.4 m (USGS colln. 30745-PC), USNM

442218. 

11, 14-17. Idioprioniodus conjunctus (Gunnell)?, X50.

11. Pb element, lateral view, upper member, 162 m (USGS colln.

30782-PC), USNM 442219. 

14-15. Sb? element, inner and outer lateral views, upper member, 207 m

(USGS colln. 30789-PC), USNM 442222.

16-17. M and Sc elements, lateral view, lower member, 53 m (USGS colln. 

30757-PC), USNM 442223-24.

12. Idioprioniodus sp. indet., Pb element, X50, lateral view, lower member, 53 m 

(USGS colln. 30757-PC), USNM 442220.

13. Idioprioniodus cf. /. healdi (Roundy)?, Pb? element, X50, lateral view, upper

member, 207 m (USGS colln. 30789-PC), USNM 442221.

18-19. Diplognathodusl ellesmerensis Bender?, Pa element, X50, lateral and upper 

views, upper member, 203 m (USGS colln. 31710-PC), USNM 442227.

20. Cavusgnathus! tytthus Brown and Rexroad, Pb element, X50, inner lateral 

view, lower member, 54.9 m (USGS colln. 31698-PC), USNM 484526.

21. Idiognathodus incurvus Dunn?, Pa element, X40, upper view, upper member, 

250 m (USGS colln. 30796-PC), USNM 442225.

22. Idiognathoides sinuatus Harris and Hollingsworth, Pa element, X40, upper 

view, upper member, 217.5 m (USGS colln. 30790-PC), USNM 442226.

23. Gnathodus bilineatus bilineatus (Roundy), juvenile right Pa element, X90, 

upper view, lower member, 69 m (USGS colln. 30762-PC), USNM 483408. 

This specimen is possibly redeposited because it occurs 13 m above the base of 

the Pennsylvanian and all other representatives of the species are restricted to 

the Mississippian part of the Wahoo Limestone in the study section (table 1).
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1568 PLATE 5

CAVUSGNATHUSt, DIPLOGNATHODUS7, GNATHODUS, IDIOGNATHODUS, IDIOGNATHOIDES, 

IDIOPRIONIODUS, AND KLADOGNATHUS