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1992
Lithostratigraphy and conodont biostratigraphy of the Grove Creek dolomite member of the Snowy Range Formation (Cambrian- Ordovician) Big Snowy Mountains Montana
Patricia G. Weaver The University of Montana
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Recommended Citation Weaver, Patricia G., "Lithostratigraphy and conodont biostratigraphy of the Grove Creek dolomite member of the Snowy Range Formation (Cambrian-Ordovician) Big Snowy Mountains Montana" (1992). Graduate Student Theses, Dissertations, & Professional Papers. 7452. https://scholarworks.umt.edu/etd/7452
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LITHOSTRATIGRAPHY AND CONODONT BIOSTRATIGRAPHY OF THE GROVE CREEK DOLOMITE MEMBER OF THE SNOWY RANGE FORMATION (CAMBRIAN-ORDOVICIAN), BIG SNOWY MOUNTAINS, MONTANA
By Patricia G. Weaver B.A., Ohio Wesleyan University, 1986
Presented in partial fulfillment of the requirements for the degree of Master of Science University of Montana 1992
Approved—by
Chairman, Board of Examiners
Dean, Graduate School
Date UMI Number; EP38253
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ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346 Weaver, Patricia, G., M.S., May 1992 Geology Lithostratigraphy and conodont biostratigraphy of the Grove Creek Dolomite Member of the Snowy Range Formation, Big Snowy Mountains, Montana (77 pp.) Director: Donald Winston Study of the lithostratigraphy and biostratigraphy of the calcareous siltstone and flat pebble conglomerate unit of the Upper Cambrian (?) through the unit to the lowest Ordovician part of the Snowy Range Formation in the Big Snowy Mountains of central Montana reveals new information about the formational status of the unit, environments of deposition, and conodont biostratigraphy. Three stratigraphie sections were measured, sampled and correlated. Although Lindsey (1980) mapped this unit as the Sage Limestone-Pebble Conglomerate Member of the Snowy Range Formation, on the basis of outcrops and thin sections, I conclude that this unit is the Grove Creek Dolomite Member of the Snowy Range Formation. Pétrographie study and comparison of faunas from this unit with others in North America reveal that the unit was deposited in a warm water shallow marine carbonate shelf environment, subject to storms and influxes of siliciclastics. The Grove Creek Member records the upper part of the long lived Sauk Sequence Transgression and is one of only three places in Montana where this part of the sequence is preserved beneath the pre-Devonian unconformity. Conodont zones from this unit range from the Clavohamulus elonaatus Subzone of the Cordvlodus proavus Zone and extend through the Cordvlodus caboti. Cordvlodus lindstromi. and Cordvlodus anaulatus zones, ending in the Rossodus manitouensis Zone. When the Cambrian-Ordovician boundary is eventually defined, these zones may be entirely Ordovician or may straddle the Cambrian-Ordovician boundary.
1 1 Table of Contents
ABSTRACT...... Ü TABLE OF CONTENTS...... i ü LIST OF ILLUSTRATIONS...... iv ACKNOWLEDGEMENTS...... v CHAPTER I Introduction...... 1 CHAPTER II Stratigraphy...... 4 CHAPTER III Carbonate Petrology...... 7 CHAPTER IV Lithostratigraphy...... 14
CHAPTER V Processes...... 21 CHAPTER VI Environments of Deposition...... 2 3 CHAPTER VII Biostratigraphy...... 2 4 CHAPTER VIII Cambrian-Ordovician Boundary...... 3 7 CHAPTER IX Faunas as indicators of Environment...... 4 2 CHAPTER X Conclusions...... 4 8 CHAPTER XI Systematic Paleontology...... 52 References...... 71
1 1 1 LIST OF ILLUSTRATIONS Figure 1. Geologic Map of the Big Snowy Mountains, Montana. ...2 2. Stratigraphie Column for Careless Creek Section A.... 8 3. Stratigraphie Column for Careless Creek Section B. ..9 4. Stratigraphie Column for Swimming Woman Canyon Section A ...... 10
5. Lithofacies Chart of the Grove Creek Dolomite in Careless Creek Section A ...... 16 6. Lithofacies Chart of the Grove Creek Dolomite in Careless Creek Section B ...... 17 7. Lithofacies Chart of the Grove Creek Dolomite in Swimming Woman Canyon Section A ...... 18 8. Lithologie Correlation Chart of Measured Sections in Careless Creek and Swimming Woman Canyons...... 19 9. World Wide Conodont Zonation Chart 2 6 10. Species Range Chart for Careless Creek Section A. ..28 11. Species Range Chart for Careless Creek Section B. ..29 12. Species Range Chart for Swimming Woman Canyon Section A ...... 30
13. Alternative Positions of the Cambrian-Ordovician Boundary...... 3 9 14. Paleobiogeographic Distribution of Cordvlodus Proavus Zone Conodonts...... 45 15. Paleobiogeographic Distribution of Cordvlodus Caboti- Cordvlodus Anaulatus ZoneConodonts ...... 4 6
Plate I ...... 69
II ...... 70
IV Acknowledgements I would like to thank my committee, Don Winston, Dave Alt, and Tom Mitchell-Olds, my parents Edwin and Dretta Weaver, for helping to finance this work, Jim Miller, and Raymond Ethington for their help in identifying the conodonts. I would also like to thank Charles Miller for his invaluable assistance in photographing the conodonts. Dave Plummer for his help with computer graphics. Du Yue, Alicia Stickney, The Splatt, Wayne Jeppson Tim Buckley, John Cuplin, Judy Fitzner, Loreen Skeel, and especially Ron and Evelyn at the Two Dot Bar for their help in various other aspects of this thesis. INTRODUCTION
Study of the lithostratigraphy and biostratigraphy of the limestone-pebble conglomerates and calcareous siltstones at the top of the Sauk Sequence (Cambrian-Ordovician) exposed in Careless Creek and Swimming Woman canyons in the Big Snowy Mountains of Montana (fig.l) has yielded new information regarding the formal status of the unit, its depositional environments, and its correlation with other known strata. First, a formal name for this unit in the Big Snowy Mountains has never been clearly established. Several authors as early as the 1930s assigned these rocks to different ages and formational names. After studying both the rock types and thin sections, I conclude that they belong to the Grove Creek Dolomite Member of the Snowy Range Formation not, as Lindsey (1980), mapped them, to the Sage Limestone-Pebble Conglomerate M e m b e r .
My studies of outcrops, thin sections and faunas, lead me to conclude that these sediments were deposited in warm water on a shallow marine platform, above storm and fair weather wave- base . I find that these strata contain a predominantly lower
Ordovician fauna. Their exposures are one of only three known localities in Montana where latest Cambrian and earliest Ordovician rocks can be studied in outcrop. The other two localities, one in the Fish Creek drainage of GEOLOGIC MAP OF THE BIG SNOWY ■ LOCATION MAP MOUNTAIN
JUDITH GAP
Big Snowy M tns.
F ig u re ml rfaken from Lindsey 119801 f
Explanation of FIgurel is on the next page northwestern Montana, (Bush et al , 1985) and the other in the Emerson Formation of the Little Rocky Mountains (Lochman-Balk, 1956) await detailed study. My study of the conodonts recovered from Careless Creek and Swimming Woman canyons reveals that they range from the very top of the Cordvlodus proavus Zone up through Cordvlodus caboti. Cordvlodus lindstromi, Cordvlodus anaulatus and end in the Rossodus manitouensis Zone. This sequence of zones compares closely to the established warm
water conodont zones recognized the world over.
explanation
LIST OF MAP UNITS
Qal ALLUVIUM (HOLOCENE)
qis LANDSLIDES (QUATERNARY)
Qp PEDIMENT DEPOSITS (QUATERNARY) CONTACT Khc HELL CREEK FORMATION (UPPER CRETACEOUS) FAULT— dashed where approximately located; Km MONTANA GROUP (UPPER CRETACEOUS) — dotted where concealed. Ball and bar on Exclusive of Hell Creek and Telegraph downthrown side Formations STRUCTURE SYMBOLS— Showing plunge, Dashed where Rc TELEGRAPH CREEK FORMATION (UPPER CRETACEOUS) approximately located AND COLORADO GROUP (UPPER AND LOWER CRETACEOUS), UNDIVIDED Anticline
Kk KOOTENAI FORMATION (LOWER CRETACEOUS) Syncline
Jme MORRISON FORMATION (UPPER JURASSIC) AND STRIKE AMD DIP OP BEDDING ELLIS GROUP (UPPER AND MIDDLE JURASSIC) DRY BOLE Pa AMSDEN GROUP (PENNSYLVANIAN) BOUNDARY OP BIG SNOWIES WILDERNESS Mbs BIG SNOWY GROUP (UPPER MISSISSIPPIAN) -- BOUNDARY OF CONTIGUOUS STUDY AREAS Mme MISSION CANYON LIMESTONE (UPPER AND LOWER MISSISSIPPIAN .
Ml LODGEPOLE LIMESTONE (LOWER MISSISSIPPIAN)
D0€ DEVONIAN. ORDOVICIAN, AND CAMBRIAN, UNDIVIDED— (shown In sections only)
Dj JEFFERSON FORMATION (UPPER AND MIDDLE DEVONIAN)
OCsr UPPER PART SNOWY RANGE FORMATION (LOWER ORDOVICIAN AND UPPER CAMBRIAN?)
UPPER AND MIDDLE CAMBRIAN FORMATIONS, UNDIVIDED
•Ef FLATHEAD SANDSTONE (MIDDLE CAMBRIAN)
Ym NEWLAND FORMATION (PROTEROZOIC Y) STRATIGRAPHY Background Several authors have assigned the cliff-forming unit of limestone-pebble conglomerates interbedded with calcareous siltstones at the top of the Sauk Sequence in the Big Snowy Mountains to various formations with various ages. For example. Reeves (1931), assigned these rocks to the Middle Cambrian Meagher Limestone. Deiss (193 6), included them in the Upper Cambrian Pilgrim Limestone. Later, Lochman-Balk (1956) assigned this limestone unit to the lower Ordovician Zortman Member of the Emerson Formation of the Litttle Rocky Mountains. In 1965 Grant extended the Upper Cambrian Snowy Range Formation to include strata in the Big Snowy Mountains because they appeared similiar in lithology to the upper part of the Snowy Range Formation. Goodwin (1964), chose to assign cliff-forming limestone and limestone-pebble conglomerate, above the shale and limey shale from Timber Creek and Swimming Woman canyons of the Big Snowy Mountains, to the cliff-forming Grove Creek Formation. Lindsey (1980), differed from Goodwin
and mapped these strata as the upper part of the Snowy Range Formation, and interpretted them to be extensions of the Sage
Limestone-pebble Conglomerate Member. The Snowy Range Formation consists of three members: the lowest is the Dry Creek Shale, which records the Dresbachian- Franconian regressive-transgressive interval. Above the Dry
Creek Shale is the Sage Limestone-Pebble Conglomerate Member, 5 which is a gray-green shaley limestone and intraformational conglomerate, that records resumption of the late Cambrian transgression. The top Member of the Snowy Range Formation is
the Grove Creek Dolomite Member, which is a cliff-forming, somewhat dolomitized calcareous siltstone and intraformational conglomerate, that records continuation of the Sauk trangressive sequence (Grant, 1965). Goodwin (1964), in the interest of convenience and regional consistency, placed similar rocks from Timber Creek and Swimming Woman canyons into what was then the Grove Creek Formation. In his opinion this unit compares closely, in both rock type and stratigraphie position, with Dorf and Lochman's (1940), original description of the formation. Grant (1965) reassigned this formation to member status and included it in the upper part of the Snowy Range Formation, because it is similar in rock types and depositional history to the underlying Sage Limestone-Pebble Conglomerate Member. The unit is now properly
called the Grove Creek Dolomite Member of the Snowy Range Formation. Goodwin (1964) described the Grove Creek strata from Timber Creek and Swimming Woman Canyons as: interbedded limestone; shale; and interformational conglomerates: gray, red, and green, glauconitic, hematitic, thin to thick bedded,
predominantly limestone and conglomerate in the upper portion. Conodont genera recovered from the Grove Creek Dolomite by Goodwin (1964), and Kurtz (1976) include Cordvlodus. Oistodus. 6 Loxodus. Acanthodus. and Acontiodus.
Assignment of the strata at Careless Creek and Swimming Woman canyons to the Grove Creek Dolomite Member In Careless Creek and Swimming Woman canyons which are a few kilometers east of Timber Creek Canyon (fig. 1), rocks of Cambrian-Ordovician age are well exposed as cliff-forming, gray-green, limestone pebble conglomerates interbedded with calcareous siltstones, which in outcrop are stained reddish- yellow near the top of the sections due to weathering below the overlying Devonian Jefferson Dolomite. Rocks from my measured sections in Careless Creek and Swimming Woman Canyons
are lithically similar to rocks Goodwin (1964) placed in the Grove Creek and are continuous with them. I concur with Goodwin (1964) and assign the Careless Creek and Swimming Woman rocks to the Grove Creek Dolomite Member of the Snowy Range Formation. Goodwin (1964), did not provide measured
sections for these areas, so detailed correlations are
impossible. In comparison with the genera recovered by Goodwin (1964) and Kurtz (1976), genera from my sections of the Grove Creek Dolomite are similar but may start somewhat
stratigraphically lower. CARBONATE PETROLOGY In thin section these gray-green limestone-pebble conglomerates and calcareous siltstones can be classified into four major rock types based on Folk's (1962) classifications: biomicrites; biosparites; intramicrites; and intrasparites. Biomicrite
The biomicrites occur mostly in the lower five feet of both sections in Careless Creek Canyon but, are not in Swimming Woman Canyon (figs. 2,3,4). They are extremely fine grained, well sorted, glauconitic, and somewhat hematitic. They contain fecal pellets, quartz silt, inarticulate brachiopod fragments, and trace amounts of mica in a lime mudstone matrix. These biomicrites are commonly evenly laminated, partly replaced by dolomite and some contain dolomite-filled burrows. The fine grain size of the skeletal fragments makes it difficult to tell what kinds of organisms
they came from. However, comparison with occasional large trilobite and pelmatozoan fragments indicates that the fragments are most likely fine-grained pieces of trilobites
and pelmatozoans.
Biosparite The biosparites or calcareous quartzose siltstones and limestones, which occur in beds throughout the three measured sections, can be divided into four rock types (figs. 2,3,4): 1) quartzose silty biosparites, 2) skeletal Stratigraphie Columns for Careless Creek Section A
CCA 120'- LEGEND illl Silty biosparite Trilobite silty biosparite
110'- Trilobite intrasparite
Trilobite intramicrite
100' Biomicrite îlil Flat pebble conglomerate 3 ? Calcareous siltstone 90'- Calcareous mudstone Left hand column represents carbonate 80'- petrography ^HrnHBrr
70'
60'-
50' m É È S t É 40'
30'
20 '
— s = B ^ nnna!gg!g
Figure. 2 CCB Stratigraphie Columns for Careless Creek Section B
LEGEND 120' Silty biosparite
^ Trilobite silty biosparite
110' Trilobite intrasparite
Rat pebble conglomerate
Calcareous siltstone 100' [ |f || Calcareous mudstone Left hand column represents carbonate 90' petrography
80'
70'
60' TzTTTTTzTTTT
50'
40'
30'
20 '
10’
Figure. 3 Stratigraphie Columns for Swimming Woman Canyon 10 Section A
SWA 120' LEGEND
Silty btospaiite 110' Trilobite silty biosparite Trilobite intrasparite
||i;| Rat pebble conglomerate
100' Calcareous siltstone Left hand column hizhiiiztit represents carbonate 90' petrography
80'
70'-
60'-
50'
40’
üiHHHiHi 30' m s s s m
2 0 - lijiiiiiiji
10'
Rgure. 4 O' 11 silty biosparites, 3) silty pellet biosparite, 4) skeletal pellet biosparites. Quartzose silty biosparites, consist primarily of quartz silt and some glauconite in a fine to medium grained sparry matrix, but lack recognizable fossil fragments and fecal pellets. Skeletal silty biosparites are composed primarily of trilobite and pelmatozoan fragments, some of which are much larger than the other grains, a few percent quartz silt and a trace of glauconite in a fine to medium grained sparry matrix, without fecal pellets. Silty pellet biosparites contain quartz silt, and fecal pellets in approximately equal percentages, with or without recognizable trilobite and pelmatozoan fragments and glauconite in a sparry matrix. Skeletal pellet biosparite also contains glauconite, and fecal pellets, with identifiable or unidentifiable fossil fragments in a sparry matrix without quartz silt. Most if not all of these types of biosparites are partly replaced by dolomite and contain fragments of inarticulate brachiopods. The dolomite has most commonly replaced the spar and fossil fragments obscuring the original material. In all three measured sections, dolomite replacement increases upward. Clays also occur in these biosparites, generally as replacement seams. Intramicrite Thin sections reveal that some of the extremely fine grained limestone-pebble conglomerates are intramicrites. Most are near the bases of the three sections (figs. 2,3,4). 12 They contain biosparite or biomicrite intraclasts in a biomicrite matrix. Clasts range in composition from the four types of biosparites discussed above to biomicrite. Some clasts are difficult to distinguish from the matrix and contain fecal pellets, quartz, glauconite, ocassional large trilobite and pelmatozoan fragments, and packstone laminae. Some specimens are a mixture of biosparite and biomicrite and contain large skeletal fragments. Dolomite rhombs commonly lie in the micrite matrix. Intrasparite The most common rocks in the three measured sections are limestone-pebble conglomerates, which thin sections show are trilobite-pelmatozoan intrasparites. The clasts within the intrasparites encompass the whole range of biosparite types. The clasts are generally flat with fairly rounded edges, and some have dolomite, glauconite, hematite or chlorite rims. A few biomicrite intraclasts occur within these intrasparites
and others occur as intraclasts within intraclasts. The
matrix of these intrasparites is mostly grain supported skeletal fragments of trilobites and pelmatozoans, in places replaced by silica. In many samples the matrix contains quartz, glauconite, fecal pellets, along with skeletal fragments, making it difficult to distinguish the matrix
from the intraclasts. Authigenic dolomite rhombs are more concentrated in the matrix than in the intraclasts. In some beds, the matrix is totally replaced by dolomite yet the 13 intraclasts remain unaltered. In other beds dolomite has replaced, both the matrix and the intraclasts. Biomicrites and clays also exist in the matrix, commonly rimming the intraclasts. Intrasparites are common throughout the three measured sections (figs. 2,3,4). LITHOSTRATIGRAPHY Regional Setting
The Sauk Sequence, which commenced in the latest Precambrian and extends through the Cambrian into the lower Ordovician records a marine transgression from the continental margins across North America (Sloss, 1963). This long-lived transgression was briefly interrupted by regressive interludes at the top of the Dresbachian Stage of the Upper Cambrian, by the Lange Ranch Regressive Event close to the base of the C. proavus Zone, and by the Black Mountain Regressive Event near the first occurrence of C . anaulatus (Miller, 1984). In Montana, the Flathead Sandstone, the Wosley Shale and the 1imestone-shale-1imestone progression of the Meagher, Park, and Pilgrim Formations, record the Sauk Sequence Transgression (Hanson, 1962). The Dry Creek Shale Member of the Snowy Range Formation represents the Dresbachian- Franconian regression. A transgression, recorded in the Sage Limestone-pebble Conglomerate and the Grove Creek Dolomite Members of the Snowy Range Formation follows the Dresbachian regression (Grant, 1965). Pre-Devonian erosion cuts down into the Upper Cambrian rocks across most of Montana. However, in the Big Snowy Mountains the Lower Ordovician
part of the Sauk Sequence is preserved below the pre- Devionian unconformity in the Grove Creek Dolomite. Big Snowy Succession
14 15 The Grove Creek Dolomite in Careless Creek and Swimming Woman canyons divide into three stratigraphically stacked lithofacies (A, B,& C, figs. 5,6,7) that can be correlated between the three sections (fig. 8). Section CCA is emphasized in this discussion (fig. 5) because it is the most complete of the three sections, and the other two sections correlate easily with it. The base of section CCA commences at the first recognizable bed above grass covered slopes. Approximately the lowest 2 5 feet characterizes lithofacies A (fig. 5). This lithofacies consists primarily of thin, (1-4 inches), planar beds of well laminated, gray-green, extremely fine grained and well sorted biomicrite and biosparite with a few thicker beds of intramicrite and intrasparite. This is the only part of the sections in which biomicrite and intramicrite are significant components. The intrasparite and intramicrite contain numerous skeletal fragments both in the matrix and the intraclasts. The intraclasts tend to be well rounded and well sorted. Lithofacies A grades gradually upwards to thicker bedded biosparite and intrasparite of lithofacies B. Approximately the next 3 0 feet in the measured sections
(part B, figs. 5,6,7) is composed of lithofacies B. This lithofacies contains thicker bedded (2-6 inches), gray- green, fine-grained biosparite and intrasparite. In this interval the biosparite beds tend to be hummocky, devoid of Lithofacies Charts of the Grove Creek Dolomite 16 in Careless Creek Section A
CCA ^120*- î î î î î î î LEGEND :: ;: ; : Intrasparite Silty biosparite Biosparite j Trilobite silty biosparite 110' Intrasparite Trilobite intrasparite Biosparite Trilobite intramicrite ICO* Intrasparite Biomicrite B i Biosparite Cover Flat pebble conglomerate Intrasparite Calcareous siltstone 90* Biosparite, trilobite beds at 91*93' Calcareous mudstone iüi Intrasparite Biosparite Left hand column represents carbonate H H s m ioa Intrasparite 80*- petrography Hummocky X-slratiMed biosparite
Intrasparite 70' Hummocky X-stratitied biosparite Intrasparite 60'- Hummocky Xstratified biosparite
Trilobite beds at 5T 50' Intrasparite w/ intraclasts imbricated at high angles thick beds
40' B Hummocky X-stratified biosparite
Intrasparite Biosparite Intrasparite Cover 20'- S Intrasparite Cover
Intrasparite/intramicrite
1 0 - Biomicrite, thin planar beds Intrasparite/intramicrite thin planar beds Biomicrite O' Intrasparite Figure. 5 Lithofacies Charts of the Grove Creek Dolomite 17 CCB in Careless Creek Section B lntrasparit«/biosparite Cover Intrasparite 120' LEGEND Cover Silty biosparite
Biosparite y ] Trilobite silty biosparite Cover 110' Intrasparite y ,^ Trilobite intrasparite Cover Intrasparite Rat pebble conglomerate Cover Biosparite Calcareous siltstone 100' [ ||± ^ Calcareous mudstone
Cover Left hand column represents carbonate 90'- petrography Intrasparite Cover Intrasparite 60'- Cover Intraspante Cover Intrasparite 70* Cover Intraspante
Cover 60'- Hummocky X-stratified beds of biosparite/intrasparite Cover 50'-
B Hummocky X-stratified 40' I alternating t>eds of biosparite/intrasparite
30' Cover Biosparite/intrasparite Cover Alternating planar beds 20 ' of biosparite/intrasparite Cover Intrasparite Cover Thin planar beds of biosparite/intrasparite Cover 10' Intrasparite Cover Thin planar beds of biosparite/intrasparite Thin planar beds of biomicrite Intrasparite Figure. 6 Lithofacies Charts of the Grove Creek Dolomite 18 in Swimming Woman Canyon Section A
120'- SWA Intrasparite LEGEND Cover Silty biosparite Intrasparite/biosparite Cover Trilobite silty biosparite 110" Intrasparite Trilobite intrasparite
Biosparite ||; i | Flat pebble conglomerate Intrasparite 100'- 1^4^ Calcareous siltstone Hummocky X-stratified biosparite Left hand column Intrasparite represents carbonate petrography 90- Biosparite Intrasparite/burrowed biosparite Cover Intrasparite 80'- Cover
70'- ^ Alternating beds of hummocky X-stratified biosparite/intrasparite
:: 60'
5 0- Cover B
4 0- Intrasparite/biosparite Intrasparite Cover % 30* Intrasparite Cover Intrasparite Cover Intrasparite 20 ' a n Cover
Intrasparite
10' Thin planar beds of biosparite > < Intrasparite ’lüüiliiiii Figure. 7 Lithologie CofTOlation Chan of Measured Sections 19 in Careless Creek and Swimming Woman Canyons
CCB CCA
120'
110 '- X T' liiiii
100'
• Ï » t *
rT'.r.r.r.'. niffiisini iiiiiiiimi
LEGEND [ -j Sitty bospatiM
Tniobrta silly biosparta
Tniobii# viuaapams
Tnlooita «waincnia
B tournent*
flat pabbi* oongiomarata Caicaraous stMsion*
Cawaraous mwdsio. a Figure 8 20 lime mud, and to contain somewhat more quartz silt than facies A below. Intraclasts are generally imbricated at a high angle to nearly vertical. Along with abundant quartz silt, biosparite and intrasparite contain large amounts of trilobite and pelmatozoan fragments. The skeletal fragments are often so small it is difficult to distinguish the trilobite from the pelmatozoan fragments. Lithofacies B grades gradually upward to even thicker bedded biosparite and intrasparite of lithofacies C. The top half of the measured sections contain lithofacies C (figs. 5,6,7). Facies C consists of relatively thick bedded (4inches-2 feet), fine to medium grained, well sorted, silty biosparite and intrasparite. Here again the biosparite beds are hummocky, devoid of lime mud, and the intrasparite has highly imbricated intraclasts. The fossils in this lithofacies are generally highly fragmented, but are coarse enough to be identifiable in the biosparite and in the matrix of the intrasparite. Inarticulate brachiopods, and trilobite cranidia, pygidia, and cheeks can be identified in outcrop. Pre-Devionian erosion cuts down into the top of this interval. In Careless Creek Canyon the Devionian Jefferson dolomite directly overlies the Grove Creek Dolomite. In Swimming Woman Canyon the Grove Creek is overlain by grassy slopes. PROCESSES The processes that affected the deposition of sediments during the latest Cambrian and earliest Ordovician in the Big Snowy Mountains, were primarily mechanical, however biological and chemical factors also had some influence. Two mechanical processes dominated sediment deposition: 1) clay and carbonate mud settle out from supension, 2) wave reworking and transport ofsediments. Lithofacies A contains the only significant amount of lime mud in the form of biomicrite and intramicrite. This mud probably settled out of suspension in relatively quiet water. Wave action had the most effect on sediment deposition, in that they broke up the fossils into fine to coarse fragments. Waves also sorted grains and fragments. Storm waves formed the hummocky cross stratification seen in lithofacies B and C. Waves as well as storm waves ripped up the and transported the intraclasts, then deposited them at high angles within the matrix of the
intrasparite and intramicrite Biological processes also affected sediment deposition during the latest Cambrian and earliest Ordovician. In outcrop the rocks show evidence of organisms leaving tracks and trails on the surface of the sediments. Worm burrows and
fecal pellets are recognizable in thin section. The fragmentary nature of the trilobites and pelmatozoans may
partly be due to some unknown predator. This unlikely because no evidence of such a predator was found.
21 22 Chemical processes also had some effect on the deposition of sediments in the Big Snowy Mountains. Evidence of chemical processes is the early partial cementation of biosparite to form the intraclasts. Dissolution and reprecipitation of carbonates in the form of styolites and dolomite replacement are also common throughout the sections. ENVIRONMENTS OF DEPOSITION The rocks deposited in the Big Snowy Mountains record the latest Cambrian and earliest Ordovician part of the Sauk Squence Transgression. Lithofacies A (figs. 5,6,7) consists primarily of thin planar beds of extremely fine grained biomicrite, biosparite, intramicrite and intrasparite indicating lime mud deposition in quiet shallow water with intraclasts eroded and transported from the more seaward lithofacies B and C by storms. Lithofacies A represents a shallow protected carbonate inner shelf deposit. Lithofacies B consists of fine-grained biosparite and intrasparite with more quartz silt in thicker hummocky cross stratified beds. This indicates a higher energy environment with more fetch and storm deposition than lithofacies A. These sediments were deposited further seaward on a transgressive carbonate shelf. Lithofacies C consists of fine-medium grained biosparite and intrasparite in thicker hummocky cross stratified beds. Lithofacies C is coarser grained than Lithofacies A or B and contains more quartz silt, this indicates that the sediments were deposited in a more open marine environment with more fetch. This lithofacies represents continued transgression.
23 BIOSTRATIGRAPHY Study of the highest Cambrian and lowest Ordovician conodonts began in 1856 with Pander's monograph in which he described many conodont taxa. From the late 1800s to about
1970, papers on these faunas were mostly taxonomic (Hinde, 1879; Furnish, 1938; Lindstrom, 1955; Muller, 1959; Nogami, 1966, 1967 ; Miller, 1969). From 1970 into the mid 1980s, studies have dealt with biostratigraphy as well as taxonomy (Miller, 1970, 1980 ; Druce and Jones, 1971; Ethington and Clark, 1971; Abaimova, 1971, 1972, 1975; Derby et. al., 1972; Muller, 1973; An and Yang, 1980 ; An, 1981, 1982 ; Miller et. al., 1982, 1984). Since the early 1970s, studies have focused on provincialism, evolution, geographic distribution of Cambrian and lower Ordovician conodonts and their occurences in various rock types (Sweet et. al., 19 59; Bergstrom and Sweet, 1966; Ethington and Clark , 1971 ; Sweet and Bergstrom, 1974; Miller, 1978, 1980, 1984, 1988 ; Landing et. al., 1980 ; Erdtmann and Miller, 1981; An, 1981; Fortey et. al., 1982 ; Ethington and Repetski, 1984). Ethington and Clark (1971) described in preliminary form a zonal scheme for Lower Ordovician conodonts from North America (Faunas A-E) (fig. 9). Because their data on the geographic and stratigraphie distribution of conodonts in lower Ordovician rocks was based on few and scattered sections, they recommended that their distributions not be considered formal faunal zones. Authors from around the
24 25 world have since recognized the same series of faunas, and
the A-E faunal units have been modified to the present scheme of Cambrian-Ordovician biostratigraphic zones. Miller (1970), building from Ethington and Clark's work further developed a preliminary conodont zonation based on faunas from Utah, Oklahoma, and Texas. This scheme was corroborated by Miller (1978, 1980, 1984), Hintze et. al. (1980), Taylor and Miller (1981), and Miller (1988). Miller's 1988 zonal scheme includes the uppermost Franconian Stage, all the Trempealeauan Stage and the lowest part of the Canadian Series. It includes faunas older than Ethington and Clark's (1971) Fauna A and extends through Fauna A to include part of Fauna B (fig. 9). The stratigraphie range of Fauna A corresponds to the upper part of the Cordvlodus proavus Zone of Miller (1978). Ethington and Clark (1982), recommended that Fauna A be abandoned in favor of Miller's zonal designation. Fauna B is now divided into the Cordvlodus caboti. the Cordvlodus lindstromi. and the Cordvlodus anaulatus Zones (Miller, 1992 personal communication). Fauna B of Ethington and Clark (1971) was originally defined as the interval between the top of
Cordvlodus proavus and the first occurrence of Loxodus bransoni (Ethington and Repetski, 1984). Miller's (1992 personal communication) new zones cover the same interval. Faunas C of Ethington and Clark, (1971) has since become the
Rossodus manitouensis Zone (Ethington, 1992 personal WORLD WIDE WARM FAUNAL REALM COLD FAUNAL REALM WESTERN USA DAVANCCHA. CHINA AUSTRALIA KAZAKHSTAN N W CANADA CONODONT ZONATION (•«ctfvi 6'«nio«i C bo I obo dm A F aun ae Cofdriotfut «nçvfatvi Or#p#r>advt U C or O r '0 (tv I C bo t onodfn# b*f tu(tb' Cord rolundatvt ■ CHART •n o v (* lu t Cord *r«d vf * ( uf îo(*è Zon# Zon* C or dr iodu I ( a I # r * Co(Or’('
Cordylodus proavus Zone As seen in figs. 10, 11, 12 appromimately the lowest 19 feet of the three measured sections contain conodonts from the upper part of Cordvlodus proavus Zone (Miller, 1978, y à s § § 8
I— jProonelodus gallatini I------— jCordylodus proavus -jTeridontus nakamurai 1 -|? Oneolodus sp. O -{Semiacontiodus nogamii z & o -|Eoconodontus nolchpoakensis S ; CO jUlahconus utahensis I -jCordylodus caboli ! (D -{Albiconus postcoslalus 01 — |Codylodus lindsiromi 0)J3 yiapalognaihus preaengansis I D (Û ------jSemiaconliodus lavadamensis t (D G? o (0 -{Cordylodus angutatus or -jUtahconus New Species #1 § I---- O Rossodus manilouensis|— O Acanihodus uncinalus)» g Oislodus (riangularis|— (D Acontiodus propinquus|— % O Orepauoisodus sp. 1 \- 3 Unident. Genus sp. A|- (p
II a â II 5 If t| Ilw II ^ -4 s? S ? S 3 K> 11 11 ilw II(ü li II 09 CCB Species Range Chart for Careless Creek 29 Section B CONODONT TRILOBITE ZONATION ZONATION
LEGEND
[lîî] Flat pebble conglomerate
110 - Calcareous siltstone Calcareous mudstone
Species only found wittiin Bellefontia 100’- a 1ft interval Rossodus xenostegium manitouensis 90*- Î I 80*- I
Symphysunna 70'- i woosteri
Cordylodus i angulatus
1 I I 1 . Symphysurina It bulbosa Cordylodus 50'- I èl I lindstromi IIIO s 40'- % I 30' ■8 Cordylodus Symphysurina cat>oti brevispicata
1 1 1 2 0 - i iTii
10'- Cordylodus Missisquoia proavus ji-L®J- typicalis after Stitt 11977) 0'- Figure. 11 Species Range Chart for Swimming Woman Canyon 30 Section A
120- SWA CONODONT TRILOBITE ZONATION ZONATION
110' l i i i l LEGEND
h\l Rat pebble conglomerate 100- Calcareous siltstone
Species only found wittiin a 1ft interval SO Bellefontia xenostegium Rossodus SO- manitouensis
70'
Symphysunna woosteri 60-
Cordylodus angulatus 50'
Symphysurina 40' bulbosa
Cordylodus lindstromi 30'
20 ' l i i i i i Cordylodus Symphysurina I caboti brevispicata 10* Cordylodus proavus Missisquoia typicalis iiill Figure. 12 after Stitt f19771 31 1980, and Miller et al., 1982). As seen in fig. 9 this zone has been recognized the world over. The base of the c. proavus Zone is placed at the lowest occurrence of C. proavus above Eoconodontus notchpeakensis (Miller, 1988). Miller (1984) divided what he inferred to be warm water faunas of the C . proavus Zone into five subzones with the Hirsutodontus hirsutus subzone at the base, ranging upward through the Frvxellodontus inornatus. Clavohamulus elonaatus. Hirsutodontus simplex, and Clavohamulus hintzei subzones. Miller (1988), has since placed the upper two subzones Hirsutodontus simplex and Clavohamulus hintzei into the overlying Cordvlodus caboti Zone leaving only Hirsutodontus hirsutus, Frvellodontus inornatus, and Clavohamulus elonaatus subzones the C. proavus Zone. This revision transforms the zones and subzones into rock intervals between biohorizons defined at lowest occurrences of successive taxa in a phylogeny (sensu Johnson, 1979). Thus the units now conform to Hedberg's, 197 6 concept of interval zones. (Miller, 1988). Accordingly the top of the Cordvlodus proavus Zone is now placed at the lowest occurerence of Cordvlodus caboti. which defines the base of the Cordvlodus caboti Zone (Miller, 1992 personal communication). Taxa, in addition to C. proavus, typically associated with the C . proavus Zone include, Frvxellodontus inornatus. Eoconodontus notchpeakensis. Teridontus nakamurai. Hirsutodontus hirsutus. Clavohamulus elonqatus. 32 and Semiacontiodus noaamii. In the Big Snowy Mountains abundant specimens of C . proavus have been recovered along with several distacodontiform species including, Eoconodontus notchpeakensis. Teridontus nakamurai. Prooneotodus qallatini, Frvxellodontus inornatus. and Semiacontiodus noaamii. However, only one specimen of Frvxellodontus inornatus was recovered and no specimens of Clavohamulus were found. Frvxel1odontus commonly ranges well into the overlying Clavohamulus elonaatus Subzone (Miller, 1988). This association of Frvxellodontus inornatus and Semiacontiodus noaamii indicates that lower parts of the measured sections in the Big Snowy Mountains probably belong to the upper part of the C . proavus Zone and are assigned to the very top of the Clavohamulus elonaatus subzone. Although no specimens of Clavohamulus were recovered, taxa commonly associated with Clavohamulus elonaatus such as Semiacontiodus noaamii and Frvxellodontus inornatus occurs in sufficient numbers to recognize the Clavohamulus elonaatus Subzone (Miller, 1992 personal communication). Because Clavohamulus is often found near algal stromatolite mounds (Miller, 1992 personal communication), the absence of Clavohamulus maybe due to the absence of stromatolite mounds in the Big Snowy Mountains. The top of the C . proavus is placed at the lowest occurrence of Cordvlodus caboti, although C. proavus continues through the overlying zone
(Miller, 1988). 33 Cordvlodus caboti Zone
As seen in figs. 10, 11, and 12 Cordvlodus caboti Zone, begins at approximately 19 feet in the measured sections and continues for about 10 feet. The C. caboti Zone has previouslly been refered to as the C. intermedius Zone (Miller, 1984, 1988). However, Nicholl has since placed the holotype of C. intermedius into synonymy with C. anaulatus. thus eliminating the species name (Miller, 1992 personal communication). Therefore, the interval between C. proavus and C. lindstromi will here be refered to as the C. caboti Zone (Miller, 1992 personal communication). The base of the Cordvlodus caboti Zone is placed at the lowest occurrence of C. caboti. However, Miller (1992 personal communication) says that the base of this zone may also be recognized at the lowest occurence of Hirsutodontus simplex. Monocostodus sevierensis. Semiacontiodus lavadamensis, or Utahconus utahensis as all of the species appear at approximately the same horizon (figs. 10, 11, 12). Chen and Gong, (1986), defined what used to be the C. intermedius Zone (now C . caboti) in China in such a way that it correlates with the Hirsutodontus simplex and Clavohamulus hintzei subzones of western United States. Subsequently, Miller (1988), reclassified the C. caboti Zone to include these two subzones. The sections in the Big Snowy Mountains contain abundant C. caboti along with most of the other commonly associated genera (figs. 10, 11, 12) such as Utahconus 34 Utahensis. Semiacontiodus lavadamensis. and Albiconus postcostatus. Again, as with the underlying C. proavus Zone, both Clavohamulus and Hirsutodontus were not found, most likely because there are no stromatolite mounds or because of small sample size. The top of the C. caboti Zone is placed at the lowest occurrence of Cordvlodus lindstromi. Cordvlodus lindstromi Zone
Chen and Gong (1986), defined the C. lindstromi Zone (fig. 9) as the rock interval between the lowest occurrence of Cordvlodus lindstromi. and the lowest occurrence of Cordvlodus angulatus, which defines the base of that overlying zone. Species commonly associated with C. lindstromi include C . proavus. C. caboti. Monocostodus sevierensis. Utahconus utahensis, and several other genera also contained in the C . caboti Zone (Miller, 1988). New taxa introduced in this zone include lapetoqnathus preaenqensis. Utahconus new species 1 (Miller, 1992 personal communication), and species of Drepanodus. As seen in figs. 10, 11, and 12 the base of the C. lindstromi Zone in the Big Snowy Mountains occurs at approximately 29 feet up in the sections and contains many of the commonly associated species such as lapetoqnathus preaenqensis, Utahconus new species 1, C. caboti, and ?Drepanodus. The top of this zone is placed at the lowest occurrence of Cordylodus anqulatus.
Cordvlodus angulatus Zone As seen in figs. 10, 11, 12, the base of the C. angulatus 35 zone varies widely between the three measured sections in the Big Snowy Mountains. The base of this zone is defined at the lowest occurrence of C. anaulatus. and the top of this zone is usually placed at the lowest occurrence of Loxodus bransoni. which defines the base of Fauna C (Ethington and Repetski, 1984). Taxa commonly associated with C. anaulatus in this zone are C. caboti. C. lindstromi. Acontiodus propinauus. species of Drepanoisodus. Scolopodus and the questionable species C. prion and C . rotundatus (Ethington and Repetski, 1984, Miller, 1988). In the Big Snowy Mountains Acontiodus propinauus, C. caboti. C. lindstromi. the questionable species C. prion, and C. rotundatus were found along with C. anaulatus from the C. anaulatus Zone (figs. 10, 11, 12). Little emphasis has been placed on the study of this zone by most workers because it is not one of the intervals being considered for defining the Cambrian- Ordovician boundary. The wide variation of the base of this zone in the Big Snowy Mountains is probably attributed to the covered intervals in sections CCB and SWA (figs. 11 and 12). CCA is the most complete of the three sections and probably accurately represents the base of the C. anqulatus
Zone.
Rossodus manitouensis Zone Ethington and Clark (1971) originally defined the interval above C. anaulatus and below Fauna D as Fauna C. Ethington has since refered to this interval as the Loxodus bransoni 36 interval and now names it as the Rossodus manitouensis Zone (Ethington, 1992 personal communication). The base of this zone is traditionally placed at the lowest occurence of Loxodus bransoni. The taxa commonly associated with this zone are C . angulatus. Rossodus manitouensis. Oistodus triangularis. and Acanthodus unicatus (Ethington and Repetski, 1984). In the Big Snowy Mountains this zone commences at aprroximately 50 feet up in the sections and continues to the top of the sections. Most of the genera commonly associated with this zone including Rossodus manitouensis. Acanthodus uncinatus. Oistodus triangularis, and C. angulatus were found except Loxodus bransoni. The absence of Loxodus bransoni is probably due to small sample size because Goodwin (1964), recovered Loxodus bransoni from his sections in Timber Creek and Swimming Woman canyons. CAMBRIAN-ORDOVICIAN BOUNDARY Though the placement of the Cambrian-Ordovician Boundary has yet to be decided (Miller, 1992 personal communication), the boundary may eventually be defined on one of the conodont zones that occurs in the Big Snowy Mountains. Three levels have been suggested for the placement of the Cambrian-Ordovician Boundary: the base of the C . proavus Zone, the base of what was the C. intermedius Zone (now C. caboti Zone), or the base of the C. lindstromi Zone (Miller, 1988). In the United States the Cambrian-Ordovician Boundary has traditionally been placed at the base of the Missisquoia deoressa subzone of the Missisquoia trilobite Zone (Stitt, 1977). This trilobite boundary marks the top of the Cambrian Croixian Series and the base of the Lower Ordovician Canadian Series. However, it falls within the Hirsutodontus hirsutus subzone of the C. proavus Zone (Ethington and Repetski, 1984, Miller, 1988). Although, this seems to be a reasonable level to place the boundary, the trilobite zones from North America are not generally recognized in other parts of the world. This level is below the planktonic graptolite Rhabdinopora Zone which traditionally, defined the base of the Orovician in Europe, and the base of C_j_ proavus is debated (Miller, 1988, Taylor et al., 1991,
Landing, 1985). Landing (1985) reported C. proavus from slope facies rocks in Vermont at a much lower level than C.
37 38 proavus is traditionally found from platform facies. This section has since been reworked by Taylor et al. (1991), and the lowest occurrence of C. proavus has been moved up. Placement of the boundary at the base of the C . proavus Zone would relegate these rocks from the Big Snowy Mountains soley to the Lower Ordovician.
The second suggestion for the placement of the Cambrian- Ordovician Boundary is at the base of what was the C. intermedius Zone, now considerd the C. caboti Zone (Chen and Gong, 1986, Miller, 1988) (fig. 13). This level was recommended by Chen and Gong (1986), however most of the Cambrian-Ordovician Boundary Working Committee generally do not accept this horizon. The base of this zone is slightly above the top of the Croixan Series in North America and slightly below the base of the Tremadoc Series in Europe (Miller, 1988). However this level is still somewhat below the lowest planktonic graptolite zone. If the boundary is placed at this level, then the sections in the Big Snowy Mountains will contain the boundary and will thus be an example of the boundary. The third and probably most prefered placement for the
Cambrian-Ordovician Boundary is at the base of the lindstromi Zone. However the validity of C. lindstromi as a species was questioned by Muller (1973); by Landing et al. (1980); by Fortey et al. (1982); by Landing (1983); and by
Nowlan (1985). Nicholl (1991) has since restudied Druce and 39 ZONE/SUBZONE ALTERNATIVE POSTIONS OF THE Rossodus CAMBRIAN-ORDOVICIAN BOUNDARY manitouensis WITHIN ESTABLISHED CONODONT ZONES Cordylodus angulatus
Cordylodus lindstromi
-7- CO Clavohamulus
Hirsutodontus simplex - 7. Clavohamulus elongatus
Fryxellodontus It/> inornatus
Hirsutodontus hirsutus -7 Cambrooistodus minutus
GO E. notchpeakensis
CD Proconodontus muelieri Figure.13 40 Jones* (1971) original material and has concluded along with other authors (Miller, 1991 personal communication, Bagnoli et al, 1988) that C. lindstromi is a valid species. However, Nicholl (1991), has confused the matter further by introducing a new species C. orolindstromi which, occurs below the first occurrence of C. lindstromi. Whether this new species is valid or not is still being debated (Miller, 1992 personal communication). The feature characteristic of C. 1indstromi. as originally defined by Druce and Jones (1971), is a secondary tip of the basal cavity under the first denticle. Nicholl (1991), sights that the major difference between C. lindstromi and C. orolindstromi is the shape of the top of that secondary tip. In C. lindstromi the basal cavity comes to a sharp point at the top of the secondary tip. In C. orolindstromi the top of the secondary tip is flat. Miller (1992 personal communication) points out that this difference may be to minor to distinguish between two species. Nevertheless, this will have serious implications for the placement of the Cambrian-Ordovician
Boundary. Of the three biohorizons discussed, the International Working Group on the Cambrian-Ordovician Boundary has recently (March, 1992) proposed that the base of the C*_ lindstromi be choosen for the boundary horizon. This is the most likely horizon for the boundary, because it includes conodonts, trilobites, and planktonic graptolites. If the 41 boundary is placed at the lowest occurrence of C. lindstromi as I think it should be, than the sections in the Big Snowy Mountains will contain the boundary and thus be a representative section for the Cambrian-Ordovician boundary. FAUNAS AS INDICATORS OF ENVIROMENT The faunas contained within these rocks include trilobites, pelmatozoans, inarticulate brachiopods, articulate brachiopods, conodonts gastropods, and an unidentified siliceous sponge-like organism. All are consistent with warm water, shallow marine, Cambrian- Ordovician carbonate platform environments. Because this study focuses conodonts, and the conodonts from the Big Snowy Moutains can be compared with what is known elsewhere about the environments which they inhabited, conodonts again will be the focus of this discussion. Sweet and Bergstrom (1974), divided Middle and Upper Ordovician conodonts into two distinct faunal provinces: the Midcontinent and the North Atlantic faunas. They based their divisions on rock types and geographic distribution of conodont faunas. The Midcontinent Faunal Province consists primarily of conodonts found in sections containing large sequences of shallow water limestones, the North Atlantic Faunal Province consists of conodonts found in sections with slope breccias
and deep water shales (Sweet and Bergstrom, 1974). These associations work very nicely for those time periods. However, they paid little attention to older faunas. Ethington and Repetski (1984) and Miller (1984), divided the latest Cambrian and the earliest Ordovician conodont faunas into warm water faunas which are equivalent to Sweet and Bergstrom's (1974) Midcontinent Faunal Province for younger
42 43 faunas, and cold water faunas which are equivalent to Sweet and Bergstrom's (1974) North Atlantic Fauna1 Province (fig. 9). Miller (1984), concluded that conodonts were apparently pelagic through most of the Cambrian and lived in a wide range of paleolatitudes. Provincialism between warm and cold faunal realms began during the latest Cambrian. The warm faunal realm during the latest Cambrian and the earliest Ordovician time included North America, Siberia, North China, Australia, and New Zealand. The Cold faunal realm included Scandinavia, Great Britian, Turkey, Iran, probably South China, and deeper water areas on the margins of North America, India, and Kazakhstan, and possibly other low- paleolatitude land masses (Miiler, 1984). Ethington and Repetski (1984), divided latest Cambrian and earliest Ordovician conodont faunas into those characteristically accumulated on 1) intertidal and shallow subtidal carbonate banks and flat in warm water and 2) those deposited on shelf areas in open ocean, and slope-rise regions in marginal basins in cold water. This is equivalent to Miller's (1984) warm and cold faunal realms and with Sweet and Bergstrom's (1974) Midcontinent and North Atlantic faunal provinces. Ethington and Repetski (1984), further describe which genera are common in each province from the
C . proavus Zone up through the Oeoikodus communis Zone. Cordvlodus proavus Zone Though c. proavus is a cosmopolitan species, many of the 44 genera associated with this zone do show provincialism. Warm water faunas include diverse taxa including
Fryxellodontidae, Clavohamulidae, and Furnishinidae (Ethington and Repetski, 1984). Landing et al. (1980), found Clavohamulus, Frvxellodontus. and Hirsutodontus to be restricted to carbonate platform deposits and suggested that geographic ranges of these taxa may have been limited by water temperature or salinity. Cold water, slope or basinal deposits tend to be lower in diversity and lack Clavohamulus. Frvxellodontus. and Hirsutodontus (Ethington and Repetski, 1984, fig. 14). The fauna from this zone in the Big Snowy Mountains is fairly diverse, contains abundant C. proavus. and does contain Frvxellodontus and is thus similar to other warm water faunas around the world. Cordvlodus caboti-Cordvlodus anoulatus Zone Ethington and Repetski (1984) combine the interval from the top of the C . proavus Zone to the lowest occurence of Loxodus bransoni into what they call Fauna B after Ethington and Clark (1971). This interval includes everything from the base of C. caboti Zone up to the top of the C. anoulatus Zone. All reported occurrences in this interval are in shelf carbonates representing warm, shallow-water deposition (Ethington and Repetski, 1984). Most faunas are dominated by Utahconus. Semiacontiodus. and other distacodiform genera, the cordylodan species being relatively less abundant (Ethington and Repetski, 1984) (fig. 15). This same pattern 45
PALEOBIOGEOGRAPHiC DISTRIBUTION Of
CORDYLOOUS PROAVUS ZONE CONOOONTS
125' 85'
Taken from Ethington and Repetski (1984)
F igure.14 46
PALEOBIOGEOGRAPHIC DISTRIBUTION OF
CORDVLODUS CABOTI - CORDVLODUS ANGULATUS ZONE CONODONTS
£5*
Founc B
iOO Mll'S
600 kilometers
Taken from Ethington and Repetski 119841 Figure.15 47 holds true for this interval in the Big Snowy Mountains, where above the C . proavus Zone proportionally fewer cordylodids were found than distacodontiform genera. Rossodus manitouensis Zone Conodonts from the Rossodus manitouensis Zone show similar distribution patterns as those from the zone below. Warm shallow water faunas have more abundant distacodontiform species than cordilodiform species (Ethington and Repetski, 1984) . In the Big Snowy Mountains species of Rossodus manitouensis. Oistodus triangularis, and Acanthodus uncinatus are proportionally more abundant than C . anoulatus. Therefore, this zone also follows the species distribution pattern for warm shallow water environments. The general faunal distribution pattern for all the zones contained within my measured sections along with the rock types represent a warm water, shallow marine, carbonate platform environment. CONCLUSIONS This study of the latest Cambrian and earliest Ordovician rocks and faunas from Careless Creek and Swimming Woman canyons has focused primarily on three problems: the formal definition of the unit; depositional processes and environments; biostratigraphy and age.
After studying the rocks both in the field and thin sections from Careless Creek and Swimming Woman canyons, I concur with Goodwin (1964) and Grant (1965) that they should be assigned to the Grove Creek Dolomite Member of the Snowy Range Formation. In outcrop the Grove Creek Dolomite consists of somewhat dolomitic gray-green calcareous siltstone and interformational conglomerate interbeds. In thin section these rocks divide into four rock types: 1) biomicrite, 2) biosparite, 3) intramicrite, and 4) intrasparite. Based on the vertical sequence of rock types, three lithofacies can be identified in my measured sections. Approximately the lowest 25 feet of the measured sections
contian lithofacies A, which consists of thin, planar beds of extermely fine-grained biomcrite, biosparite and a few thicker beds of intramicrite and intrasparite. Approximately
the next 3 0 feet of the measured sections contain lithofacies B, which consist of fine-grained biosparite and intrasparite in thicker hummocky beds. The top half of the measured sections contain lithofacies C, which consist of
48 49 even thicker hummocky beds of fine to medium grained biosparite and intrasparite.
I then interpreted depositional processes and environments of deposition based on these lithofacies. Lithofacies A was deposited in quiet shallow water somewhat near shore. This is the only lithofacies that contains a significant amount of lime mud. Lithofacies B was deposited in somewhat more open shelf setting than lithofacies A as is evident by the thicker hummocky beds, Lithofacies C was deposited in even more open marine shelf setting than either lithofacies A or lithofacies B. All three lithofacies were deposited above storm wave-base. The fragmentary nature of the fossils contained within the rocks, the hummocky beds, and the high angle imbrication of the intraclasts of the intrasparites indicate that the main process that affected these sediments were storm waves. Other factors such as bioturbation and dissolution had a lesser affect on these sediments. The whole sequence of rocks in the measured sections show a transgression as indicated by the thickening upwards of the beds and the coarsening upward of the grains. This sequence reflects the latest Cambrian to Lower Ordovician part of the long-lived Sauk Transgressive Sequence. Conodont data was useful not only for zoning these rocks but for determining their age and for further describing the environments of deposition. Conodonts recovered from the rocks at Careless Creek and Swimming Woman canyons range 50 from the Clavohamulus elonaatus Subzone of the C. proavus Zone up through the C. caboti. C. lindstromi. C. anoulatus zones and and end in the Rossodus manitouensis Zone. The International Working Group on the Cambrian-Ordovician Boundary recently (March,1992) proposed that the Cambrian- Ordovician Boundary be placed at the lowest occurrence of C. lindstromi if this horizon is approved than these rocks from the Big Snowy Mountains are both latest Cambrian and earliest Ordovician in age. I think this is a reasonable horizon to place the boundary because it contains conodonts, trilobites and planktonic graptolites that can be recognized around the world. The conodonts are also useful for further interprettation of the environments of deposition because faunas from all five zones are consistent with faunas found from warm water shallow marine carbonate platform environments around the world. In conclusion, study of the rocks and conodonts from Careless Creek and Swimming Woman canyons in the Big Snowy
Mountains reveals that they are part of the Grove Creek Dolomite member of the Snowy Range Formation, and that they are latest Cambrian-earliest Ordovician in age. These sediments were deposited in a warm water shallow marine platform environment subject to reworking by storms and minor influxes of siliciclastic sediments. These rocks record a transgressive sequence reflecting the latest Cambrian-earliest Ordovician part of the long lived Sauk 51 Sequence transgression, and finally these sections contain conodonts from the Clavohamulus elonaatus Subzone of the C . proavus Zone up through the Rossodus manitouensis Zone and are thus useful for correlation with established warm water conodont zones from around the world. systematic Paleontology Genus ACANTHODUS Furnish, 1938 Type species.— Acanthodus uncinatus Furnish, 193 8 Diagnosis.— Genus is characterized as simple cones characterized by serration of the posterior margin of the cusp.
ACANTHODUS UNCINATUS Furnish Acanthodus uncinatus Furnish, 1938, p.337, pi.42, fig.30, text-fig.2B: Hass, 1962, p.45, text-fig.23(3); Lindstrom, 1964, p.138, text-figs.lOD, 47F; Ethington and Clark, 1981, p.17, pl.l, fig.8. ?Acanthodus uncinatus Druce and Jones, 1971, p.55-56, pi. 6, figs.9a-12c, text-fig.19b. Remarks.— This species differs from the more common and abundant A. lineatus in lacking costae. The base is expanded posteriorly but narrow anteriorly, sharp edges of the cusp continue to to the basal margin. Occurrence.— This species has been reported from the Rossodus manitouensis Zone in North America and Australia.
Number of specimens.— 79. Repository.— University of Montana Museum of
Paleontology. Genus ACONTIODUS Pander, 1856 Type species.— Acontiodus latus Pander, 1856. Remarks.— This genus is still undergoing major revisions
(Ethington and Clark, 1981). Most of the species have been reassigned to different genera. However I report them under the generic name Furnish (1938) used in the original discussion.
52 53 ••ACONTIODUS” PROPINQUU8 Furnish s.f. Acontiodus propincruus Furnish, 1938, p.326, pi.42, figs.13- 15, text-fig.IM; Repetski and Ethington, 1977, p.95; Ethington and Clark, 1981, p.24, pl.l, fig.26. ?Acontiodus cf. propinouus Muller, 1964, p.96, pi. 12, fig.8; Abaimova, 1975, p.49-50, pi.2, figs.6,7. Remarks.— This species may be rounded across the anterior margin or may taper anteriorly to a blunt edge. Occurrence.— This species occurs within the C. analutaus and the Rossodus manitouensis zones in North America, Siberia and possibly Korea. Number of specimens.— 11. Repository.— University of Montana Museum of Paleontology. Genus ALBXCONUS Miller, 1980 Type species.— Albiconus postcostatus Miller, 1980. Diagnosis.— One element apparatus of symetrical simple cones, proclined to erect; base narrow, tapering gently to tip, tip bent posteriorly; basal cavity extending to tip
(Miller, 1980) ALBICONUS POSTCOSTATUS Miller Albiconus postcostatus Miller, 1980, p.8-9, text-fig.2,
figs.A-D. Remarks.— As this species is the only species of this genus, it does not differ from the orginal species description. Occurence.— This species occurs in the C. caboti Zone in the United States and Canada.
Number of specimens.— 14. 54 Repository.— University of Montana Museum of Paleontology.
Genus CORDYLOOUS Pander, 1856 Type species.— Cordvlodus anoulatus Pander, 1856 Diagnosis.— multielement aparatus; elements simple and possesing posterior denticulate process. Rounded elements usually symetrical, with rounded cusp and denticles; denticles usually separated from one another at bases, except in advanced species. Compressed elements asymetrical, due to lateral bending of cusp and denticles, and because of prominent carina on inner side of process ; cusp and denticles strongly compressed laterally and possesing sharp edges; denticles fused at bases. Rounded elements twice as abundant as compressed elements. CORDYLOOUS ANGULATUS Pander (pi. 1, figs. 1, 2, 4, 8) Cordvlodus anoulatus Pander, 1856, p.33, pi.2, figs.27-31, pi.3, fig.10; Lindstrom (part), 1955, p.551, text-fig. 3G (not text-fig. 3E), pi. 5, fig. 9 (?) ; ?Ethington and Clark, 1965, p.189, pl.l, fig.7; Druce and Jones (part), 1971, p.66, text-fig.23a,b, pi.3, figs.4-6 (not fig.7); Jones, 1971, p.45, pi.8, figs.3a-c; Ethington and Clark (part), 1971, pl.l, figs.16,20 (not fig.15); Muller, 1973, p.27, text-fig.2G,3, pi.11, figs.1-5, ?6,7; not Van Wamel, 1974, p.58, pl.l, figs.5-7 ; Viira (part), 1974, p.63, text-fig. 4c (not text-figs.4a,b), pl.l, figs.1-3,11-13 (not fig.8); not Repetski and Ethington, 1977, pl.l, fig.3; Miller, 1980, pp.13,15,16, text-fig.4, pl.l, fig.22; An, 1981, p i .2, fig.17; Ethington and Clark, 1981, pp.34-35, pi.2, fig.24; Repetski, 1982, pp.16-17, text- fig.4, pi.4, fig.9; Taylor and Landing, 1982, text-fig.5; An et al., 1983, p.84, pi.8, figs.1-2; Nowlan, 1985, p p . 108-109, text-fig.4(10); Bagnoli et al., 1988, pp.150, 152, pl.l, figs.19-21; Kaljo et al., 1988, pp.460-463, figs.4-5. Cordvlodus so. A Druce and Jones, 1971, p.72, text-fig.23U, p i .10 fig.10. 55 (In part) Cordvlodus prion Lindstrom, 1955, p.552, pi.5, figs.14-16; Druce and Jones, 1971, p.70, text-fig. 23i, k- o, pi.2, figs.1-7; Muller, 1973, p.33, text- fig.2E,8,pl.lO, fig.4; not Van Wamel, 1974 , p.59, pl.l, figs.8-9; ?Viira (part), 1974, p.63, pl.l fig.7 (not fig. 6) • (In part) Cvrtoniodus prion Ethington and Clark, 1971, pl.l,fig.21; Miller, 1971, p.79, figs.14-16 (not fig. 17). Cordvlodus rotundatus Pander, 1856, p.33, pi.2, figs.32- 33; Lindstrom, 1955, p.553-554, pi.5, figs.17-20, text- fig.3F; Ethington and Clark, 1971, pl.l, fig.17; Druce and Jones, 1971, p.71-72, pi.3, fig.8; Jones, 1971, p.49, pi.2, figs.10-11; Muller, 1973, p.36-37, pi.11, figs.8-10, text-fig.2H; Van Wamel, 1974, p.20-21, pl.l, fig.14; Miller, 1980, p.20-21, pl.l, fig.24, text-fig.4P; An, 1981, pl.l, figs.18-19; Repetski, 1982, p.18, pi.5, fig.3, text-fig.4N; An et al., 1983, p.88-89, pi.8, figs.3-7 ; Nowlan, 1985, p . 11-112, text- fig. 4(3). Remarks.— C. anoulatus differs from other species of Cordvlodus in that its basal cavity is sigmodialy recurved toward the anterior margin. C . rotundatus is here taken to be a synonym of C. anoulatus following Bagnoli et al. (1988). Occurence.— Species is widely distributed in North America, northwestern Greenland, Scandinavia, Soviet Union, and Australia. In the Big Snowy Mountians it is found in the upper part of all three sections. The lowest occurence defines the base of the C. anoulatus Zone.
Number of specimens.— 57. Repository.— University of Monatana Museum of
Paleontology.
CORDYLOOUS CABOTI Bangoli et al., 1988 (pl. 1, fig. 5, pl. 2, fig. 2)
Cordvlodus caboti Bagnoli, Barnes, and Stevens, 1988, p.152, pl.l, figs.10-14. Cordvlodus anoulatus Lindstrom, 1955, p.551-552, text-fig.3E 56 (only). Cordvlodus proavus Druce and Jones, 1971, p.70-71, pl.l, figs.1,3 (only), text-fig.23 P-Q (only); Fortey et al., 1982, text-fig.6H (only), text-fig.BF (only). Cordvlodus cf. C. proavus Druce and Jones, 1971, p.71, pl.l, fig.10 (only). Cvrtoniodus prion Ethington and Clark, 1971, pl.l, fig.21. Cordvlodus prion Druce and Jones, 1971, p.70, pi.2, figs.6-7 (only), text-fig.23M-0; Landing and Barnes, 1981, pi.2, fig.16, text-fig.3(6); Fortey et al., text-figs.6W,Y, 81- L;Landing, 1983, text-fig.71,J, 8B,D. Cordvlodus intermedius Muller, 1973, p.30, text-fig.2C; Landing et al., 1980, p.19-20, text-figs.SE,6A; Miller, 1980, p.17-18, pl.l, fig.17 (only), text-fig.4M (only); Landing and Barnes, 1981, pi.2, fig.19, text-fig.3(5); Fortey et al., 1982, text-fig.6E-F, text-fig.8D,K; Landing, 198 3, text-fig.7H,8E. Cordvlodus lindstromi Muller, 1973, p.32, text-fig.2D; Repetski, 1982, p. 17-18, pi.5, fig.4?, text-fig.40. Cordvlodus drucei Miller, 1980, p.16-17, pl.l, fig.17 (only), text-fig.4M (only). Remarks.— This species differs from other species of Cordvlodus in that the basal cavity has a centrally located and an anterior margin which is straight to gently convexo- concave from tip to basal margin. Occurence.— This species is known from the C. caboti Zone in The United States, Canada, Australia, and China.
Number of specimens.— 40. Repository.— University of Montana Museum of
Paleontology. CORDYLODUS LINDSTROMI Druce and Jones (pi. 1, figs. 3, 7) Cordvlodus lindstromi Druce and Jones,1971, p .68,text- fig.23h, pl.l, figs. 7-9, pi.2, fig.8; Jones, 1971, p.47, pi.2, fig.4; Muller, 1973, p.32, text-figs.2D,6, pi.9, figs.10,11; Miller, 1980, pp.18-19, text-fig.4,I,J, pl.l, figs.18,19; Barnes, 1988, text-fig.14c, fig.13.(i-1); Kajlo, 1988, figs.4-5,w,x,y ,z (not figs.4-5,v); Nicholl,1991, p.231, figs.2.3,2.4. Cordvlodus anoulatus Lindstrom (part), 1955, p.551, text- fig. 3E (not fig.3G), ?not pi.5, fig.9. 57 Cvrtoniodus prion Miller (part),1971, p.79, pl.l, fig.17 (not figs.14-16).
Remarks.— This species differs from other species of Cordvlodus in that the basal cavity has a secondary apex below the first denticle on posterior process. Nicholl (1991) established C. prolindstromi below C. lindstromi on the basis of the shape of the secondary apex. This is too minor of a difference to warrant naming a new species. Thus C. prolindstromi is regected here. Occurrence.— This species is known from the United States, Canada, China, and Australia. Number of specimens.— 33. Repository.— University of Montana Museum of Paleontology.
CORDYLODUS PROAVUS Muller Cordvlodus proavus Muller,1959, p.448, text-fig.3B, pi.15, figs. 11,12,18; 1973, p.35, text-figs.2A,9, pi.9, figs. 1- 9; Miller, 1969, p.424, text-fig. 3D, pi.65, figs.37-45; 1971, p.79, figs.18,19; 1980, pp.19-20, text-fig.4,G ,H, pl.l, figs.14-15; Ethinton and Clark, 1971, pl.l, figl9; 1981, pp.33-34, pi.2, figs.18-19 ; Druce and Jones (part), 1971, p.70 (not text-fig.23p), pi.1, figs.2-6 (not fig.1); Jones, 1971, p.48, pi.2, fig.9; Abaimova, 1972, text- fig.l; 1975, p.109, text-figs.8.27,8.28, pi.10, fig.16; Abaimova and Markov, 1977, p.91, pi.14, fig.1; Landing, Taylor, and Erdtman, 1978, text-fig.2F; Farhaeus and Nowlan, 1978, p.453, pi.1, figs.8,9; Tipnis, Chatterton, and Ludvigsen, 1978, pl.l, figs.8,9; An, 1979, pi.2, fig.18; An, 1982, pp.129-130, pi.16, figs.1-4,6 pi.2, figs.18-19; Fortey et al., 1982, text-figs.6(G,H),8(F,J); An et al, 1983, p.87, pl.7, figs.1-5,8,11; Landing, 1983, text-figs. 7 (G),8(A),9(A-C); Apollonov et al, 1984, pl.30, figs.2,3,5,7,11,13-15; Nowlan, 1985, p.Ill, text- fig. 5 (12,13,17,18,19) ; Bagnoli et al, 1988, pp.154-155, pl.l, figs.7-9 ; Barnes, 1988, fig.13(a-c) ; Kajlo, 1988, figs.4,5(b,c,e,g-l); Taylor et al, 1991, fig.6,(7-11). Cordvlodus cf. C. proavus Druce and Jones, 1971, p.71, text- 58 fig.23s, pi.1,figs.10,?11; Tipnis, Chatterton, and Ludvigsen, 197 8, pi.1, fig.10. Cordvlodus oklahomensis Muller, 1959, p.447, text-fig. 3A, pi.15, figs.15,16; 1973,p.33,text-figs.2B,7, pi.9, figs,12,13; Miller, 1969, p.423, text-fig.31, pi.65, figs.43-56; Ethington and Clark, 1971,pl.l, fig.24; not Druce and Jones, 1971, p. 69, text-fig.23j, pi.5, figs.6,7; ?not Jones, 1971, p.47, pi.2, figs.5-8; Abaimova, 1975, pl.l, fig.7; Fortey et al., 1982, text- figs. 6 (V),8(G,0); Landing, 1983, text- figs.7 (F),8(C) ; Apollonov et al, 1984, pl.30, fig.12; Nowlan, 1985, p.110, text-fig.4(21-25). Cordvlodus anaulatus Van Wammel (part), 1974, pl.l, fig.5 (not figs. 6,7).
Remarks.— This species differs from other species of Cordvlodus in that the anterior margin of the basal cavity is concave. Occurrence.— This species is known from the C. proavus Zone in the United States, Canada, China, Australia, Sweden, and The Soviet Union. Number of specimens.— 34. Repository.— University of Montana Museum of
Paleontology. Genus EOCONGDONTUS Miller Type species.— Proconodontus notchpeakensis Miller, 1969 Diagnosis.— Two-element apparatus, rounded and compressed elements lacking posterior process and secondary denticles. Both elements proclined to erect ; basal cavities large, moderately to very deep; cusp very short to long and composed of white matter; surface of elememnts smooth
(Miller, 1980).
EOCONGDONTUS NOTCHPEAKENSIS Miller 59 Eoconodontus notchpeakensis Miller, 1980, pp.23-24, text- fig.3 (D-E), pl.l, figs.10-12; Taylor and Landing, 1982, text-fig.5 (O); Landing, 1983, p.1177, text-fig.11(P-Q); Apollonov et al., 1984, pl.30, figs.8,9,23; Nowlan, 1985, text-fig.5(7-9,14-16) ; Bagnoli et al, 1988, pp.155-156, pi.2, figs.5-7. Proconodontus notchpeakensis Miller, 1969, p.438, text- fig.5G, pi.66, figs.21-29; 1971, text-fig.17N, pi.2, figs.19,20; Lindstrom, 1973, pp.402-403,411; Muller, 1973, p.43, pi.4, fig.6; Tipnis, Chatterton, and Ludvigsen, 1978, pl.l, fig.14,715. Proconodontus carinatus Miller, 1969, p.437, text-fig.51, pi.66, figs.13-20 ; Lindstrom, 1973, p.401-403 ; Landing, Taylor, and Erdtmann, 1978, text-fig.2A. Oneotodus nakamurai Nogami (part), 1966, p.216, text- figs.3D,E (not text-figs.3A-C), pi. 1, figs.10,11 (not figs.9,12,13) ; ?Druce and Jones (part), 1971, p.82, text- fig.23j (not text-fig.23i), pi.10, figs.1,2,5,6,(not figs.3,4,7,8); ?Jones (part), 1971, p.58, pi.4, figs.1,3, (not figs.2,4); Lee, 1975, p.81, text-figs.2E,G, pl.l, figs.6,9,10; Abaimova and Markov, 1977, p.92,pi.14, figs.12-14,16. Proconodontus mulleri mulleri [sic] Ozgul and Gedik, 1973, p . 49, pl.l, fig.6. Proconodontus so. aff. P. carinatus Ozgul and Gedik, 1973, p.49, pl.l, fig.15. ?Oneotodus altus Viira, 1970, text-fig.7, pi.10, fig.7. Remarks.— As this genus is monotypic, the species follow the generic description. Occurence.— This species is known from the C. proavus Zone in the United States, Canada, Greenland, Iran, the Soviet Union, South Korea, Turkey, China, and Australia.
Number of specimens.— 21. Repository.— University of Montana Museum of
Paleontology. Genus FRYXELLODONTÜS Miller Type species.— Frvxellodontus inornatus Miller, 1969.
Diagnosis.— Bilaterally symmtrical, multielement genus consisting of three or four types of elements symetrically 60 arranged. Elements commpressed laterally, or by symmetry transition, anterio-posteriorly; assymetrical to bilaterally symmetrical. Basal cavity large irregular in cross section, and extending to tip of cusp, which is more or less strongly bent posteriorly (Miller, 1969).
FRYXELLODONTÜS INORNATUS (pi. 1, fig. 6) Frvxellodontus inornatus Miller (part),1969, p.426, text- figs.4A,C-E, pi.65, figs.1-10,12-16,23-25 (not fig.11); Lindstrom, 1973,p.79-81; Miller, 1980, p.23, text-figs.5A- D; Landing, Ludvigsen and Bitter, 1980, p.24,25, figs.7C- G; An et al, 1983, p.98, pi.3, figs.19,20; Wang, 1984, pp.224-225, pi.2, figs.23-26; pi.12, figs.15-17; Chen, 1986, pp.142-144, text-fig. 49, figs.1-13, pi.41, figs.1-3, 5-16. Gen. et so. indet. B Druce and Jones, 1971, p.102, text- fig.33, pi.12, fig.9. Remarks.— This species consist of four elements; planus, serratus, symmetricus, and intermedius elements. Only the planar element was recovered from the Big Snowy Mountains. Occurence.— This species is known from warm water faunal provinces in the C . proavus Zone in the United States,
Canada, Greenland, and Australia.
Number of specimens.— 1. Repository.— University of Montana Museum of
Paleontology.
Genus lAPETOGNATHUS Landing, 1982 Type species.— Pravoanathus aenaensis Lindstrom, 1955 sf. Diagnosis.— Genus is represented by elements bearing only one lateral process and with antereo-posteriorly compressed cusp and denticles. Basal cavity fills base, basal tip 61 shallow and located either medially in cusp or closer to lateral process.
lAPETOGNATHUS PREAENGENSIS lapetoqnathus preaenqensis Fortey et al., 1982, p.124-126, text-figs.6,8 ; Barnes, 1988, text-fig. 13, figs.y ,z,aa-ee; Kajlo et al., 1988, text-figs. 4,5, fig.bb. Remarks.— As this genus is monotypic the species description is the same as that for the genus. Occurence.— This species is known from the C. lindstromi Zone in the United States and Canada. Number of specimens.— 16.
Repository.— University of Montana Museum of Paleontology.
Genus OISTODUS Pander, 1856 Type species.— Oistodus lanceolatus Pander, 1856. Diagnosis.— multielement genus; highly variable in cross section. ••OISTODUS” TRIANGULARIS Furnish, 1938 Oistodus? triangularis Furnish, 1938, p.330-331, pi. 42, fig.22, text-fig.IP; Ethington and Clark, 1971, p.72, pl.l, figs.18,22,23 ; Ethington and Clark, 1981, p.70-71, pi.7, figs.15,18,22,23. ?Drepanodus acutus Druce and Jones, 1971, p.73, pi.20, figs.5a- 7c, text-fig, 24a. ?Acodus housensis Jones, 1971, p.43, pi.3, 6a-c. ?Drepanodus tenuis Jones, 1971, p.55, pi.5, figs.3a-4b, pi.8, figs.9a-c. ? aff. Acodus firmus Viira, 1974, p.42, pl.l, figs.21-23, text-fig.2. Remarks.— This species is characteristically triangular in cross section. Typically the anterior margin is turned toward the more nearly planar side of the element (Ethington and Clark, 1981). 62 Occurence.— This species occurs in the Rossodus manitouensis Zone in the United States, Australia, and Estonia.
Number of specimens.— 71.
Repository.— University of Montana Museum of Paleontology.
Genus PROONEOTODUS Muller and Nogami, 1971 Type species.— Oneotodus aallatini Muller, 1959 sf. Diagnosis.— This genus is a paraconodont, that are completely hollow, tips generally recurved anteriorly. PROONEOTODUS GALLATINI Prooneotodus aallatini Fortey et al., 1982, text-fig.9, figs. h,o. Oneotodus aallatini Muller, 1959, p.457, pi.13, figs.5,6,8- 10,7(7), 12 (?) ; Goodwin, 1961, p.66, pl.l, fig.4; Miller, 1969, p. 435. Remarks.— Elements of this species contain no white matter and tips are anteriorly recurved. Occurrence.— This species occurs at the base of the C. proavus Zone in the United States and Canada.
Number of specimens.— 7. Repository.— University of Montana Museum of
Paleontology. Genus ROSSODUS Repetski and Ethington, 1983 Type species.— Rossodus manitouensis Repetski and Ethington, 1983. Diagnosis.— Multielement lamellar conodonts having an apparatus that consists of a symmetry transition series of costate, cone-like to blade—like coniform elements and an oistodontiform element (Repetski and Ethington, 198 3). 63 ROSSODUS MANITOUENSIS (pl. 1, fig. 9, pl. 2, fig. 8) Rossodus manitouensis Repetski and Ethington, 1983, p.290- 298, f igs.1A-V,2A-T,3A-R,4A-D. Acodus oneotensis Muller, 1964, p.95-96, pl.13, figs.la,b; Druce and Jones, 1971, p.56—57, pl.12, figs.3a-7c, text- fig.20; Jones, 1971, p.44, pl.l, figs.6,7, pl.8, figs.la- c, not pl.l,fig.5; Muller, 1973, p.26-27, pl.7,figs.1,3-8. ? Acodus? sp. Mound, 1968, p.407, pl.l,figs.16,28. ? Acontiodus bicurvatus. Mound, 1968, p.407, pl.l, figs.17,29. Distacodus stola stola Mound, 1968, p.410, pl.2, fig.14, not pl.2, figs.12,13. ?Acodina eurvptera Abaimova. 1971, p.75-76, pl.10, figs.2,3; Abaimova, 1972, text-fig.1(19a,b); Abaimova, 1975, p.33- 34, pl.l, figs.7-9, text-fig.6(7,8). ? Acodus aliformis Abaimova, 1971, p.76-77, pl.10, fig.5 ; Abaimova, 1972, text-fig.1 (53a,b); Abaimova, 1975, p.41- 42, pl.2, figs.1-3. Oistodus SP. Ethington and Clark, 1971, p.69, pl.2, fig.2. ? Oistodus inaecfualis Druce and Jones, 1971, p. 76, pl. 12, figs.10a-13b, text-fig.25a. ? Oistodus lanceolatus Druce and Jones, 1971, p.77-78, pl.6, figs.6a-8c, text-fig.25b; Muller, 1973, p.40-41, pl.8, figs.3-5. New Genus Repetski and Ethington, 1977, p.95, pl.11, fig.6. New Genus A. n. s p . A Repetski and Perry, 1981, p.14-16, pl.l, figs.4,6, pl.2, figs.11,12,15. New Genus 3 Ethington and Clark, 1982, p.118,119, pl.13, figs.21-23,25,27. Remarks.— This species consists of both coniform and oistodontiform elements. The coniform elements are procline to erect, with pronounced, rounded carinae anteriorly or anterolaterally and a blade-like cusp. Oistodontiform have a flexed blade-like cusp (Reptski and Ethington, 1983). Occurence.— This species occurs in the Rossodus manitouensis Zone in the united states, South Korea,
Australia, and the Soviet Union. Number of specimens.— 51. Repository.— University of Montana Museum of 64 Paleontology.
Genus SEMIACONTIODUS Miller, 1969 Type species.— Acontiodus (Semiacontiodus^ noaamii Miller, 1969, p.421.
Diagnosis.— Apparatus a symmetry transistion of two type of erect to reclined simple cones, lacking costae or keels. Basal cavity moderately deep; white basal cone often prominent. Most of cusp composed of white matter (Miller, 1980).
SEMIACONTIODUS NOGAMII (pl. 2, fig. 7) Semiacontiodus noaamii Miller, 1980, p.32-33, text-fig.4V, pl.2,figs.10-12 ; Fortey et al., 1982, text-fig.8, figs.V,x; Nowlan, 1985, p.114, figs.5.36,5.44 ; Chen et al., 1988, text-fig.2, fig.7. Acontiodus (Semiacontiodus) noaamii Miller, 1969, p.421, text-fig.3G, pl.63, figs.41-50; 1971, text-fig.17A, pl.l, figs.1-4. Semiacontiodus noaamii Lindstrom, 1973, p.441-443. Acodus housensis Miller, 1969, p.418, text-fig.3A, pl.63,figs.11-20 ; Jones, 1971, p.43, pl.3,fig.6. Oneotodus datsonensis Druce and Jones (part), 1971, p.80, pl.14, fig.4 (not figs.1-3). Oneotodus erectus Druce and Jones, 1971, p.80, text-fig.2 6d, pl.15, figs.2-9; Jones, 1971, p.57, pl.3, fig.8, pl.8, fig.8. Oneotodus variablilis Abaimova and Markov, 1977, p.93, p l .14, fig.11, p l .15, fig.4. Remarks.— This species differs from Teridontus nakamurai by having costae and lacking a circular cross section
(Miller, 1980). Occurrence.— This species occurs in the Clavohamulus elonaatus Subzone of the C . proavus Zone in the United
States, Canada, Australia, and the Soviet Union.
Number of specimens.— 8. Repository.— University of Montana Museum of 65 Paleontology.
SEMIACONTIODUS LAVADAMENSIS Miller (pl. 2, fig. 6)
Semiacontiodus lavadamensis Miller, 1980, p.33, pl.2, fig.4; Chen et al., 1988, text-fig.2, fig.12. Acontiodus (Acontiodus) lavadamensis Miller, 1969, p.420, text-fig.30, pl.64, figs.55-61.
Remarks.— This species differs from Semiacontiodus noaamii by the addition of a posterior costa to the symetrical element.
Occurrence.— This species occurs in the C. caboti Zone in the United States. Number of specimens.— 9. Repository.— University of Montana Museum of Paleontology.
Genus TERIDONTUS Miller, 1980 Type species.— Oneotodus nakamurai Nogami, 1967. p.216. Diagnosis.— One element apparatus consisting of symmetrical simple cones, usually erect to reclined; keels and costae lacking, cross section circular to slightly oval; basal cavity moderately deep to shallow; cusp composed almost entirely of white matter (Miller, 1980). TERIDONTUS NAKAMURAI (pl. 2, fig. 4) Oneotodus so. a Muller, 1959, p.458, pl.l3, fig.17. Oneotodus nakamurai Nogami (part), 1967, p.216, text- figs.3A,B,?C (not text-figs.30,E), pl.l, figs.9,12,713 (not figs.10,11); Miller, 1969, p.435, text-fig.5E, pl.63, figs.1-10; Druce and Jones (part), 1971, p.82, text- fig.26i (not text-fig.26j), pl.lO, figs.3,4,7,8 (not figs.1,2,5,6); Jones (part), 1971, p. 58, pl.4, figs.1,3, (not figs.2,4); Muller, 1973, p.41, pl.5, fig.4; not Lee,1975, p.81, text-figs.2E,G , pl.l, figs.6,9,10; not 66 Abaimova and Markov, 1977, p. 92, pl.l4, figs.12-14,16. Oneotodus datsonensis Druce and Jones (part), 1971, p.80, text-fig.26c, pl.14, figs.1-3 (not fig.4); Jones, 1971, p . 56, pl.3, figs.5,7. Teridontus nakamurai Miller, 1980, p.33-34, text-fig.40, pl.2, figs.15,16; Nowlan, 1985, p.116, text-fig.5 (40-43); Bagnoli et al., 1988, p.156, pl.2, figs.15,16. Remarks.— This species is similar to Semiacontiodus nogamii, but is circular in cross section and lacks costae. Occurrence.— This species is long ranging throughout the g^-Proavus Zone in the United states, Canada, Greenland, Korea, the Soviet Union, and Australia. Number of specimens.— 54. Repository.— University of Montana Museum of Paleontology.
Genus Utahconus Miller, 1980 Type species.— Paltodus utahensis Miller, 1969, p.436. Diagnosis.— Apparatus consisting of two types of simple- cone elements that form a symmetry transition; elements proclined, compressed, usually bent laterally; basal cavity a round cone, cusp large and composed of white matter. UTAHCONUS UTAHENSIS (pl. 2, fig. 3) Paltodus utahensis Miller, 1969, p.436, text-fig.5F, pl.63, figs.33-40. Acontiodus fSemiacontiodus1 unicostatus Miller (part), 1969, p.421. text-fig. 5F, pl.64, figs.46-48 (not figs.49-54). Acodus severiensis Miller (part), 1969, p.418, text-fig.3H, pl.63, figs.21-24 (not figs.25-32). Scandodus furnishi Druce and Jones, 1971, p.88, text-fig.29, p l .13, figs.6-8,?9. Acodus tetrahedron Ozgul and Gedik, 1973, p.46, pl.l, fig.5. Semiacontiodus utahensis Lindstrom, 1973, p.442,443,449. Semiacontiodus unicostatus Lindstrom, 1973, p.442,443,447. Utahconus utahensis Miller, 1980, p.35-36, text- fig . 3B, C, F, G , pl.2, fig.1,2; Nowlan, 1985, p.117-118, text-fig.9 (1-3), fig.5 (45-52). 67 Remarks.— The unicostate elements of this species are indistinguishable from Utahconus tenuis. however, utahensis does not have an oistodiform bicostate element. Occurrence.— This species occurs in the C. caboti Zone in the United States, Canada, Greenland, Turkey, and Australia. Number of specimens.— 53. Repository.-- University of Montana Museum of Paleontology. UTAHCONUS NEW SPECIES 1 Miller, 1984 (pl.2, fig. 5) Remarks.— Miller ( 1992, personal communication) identified some of specimens from the C. lindstromi Zone from my material as what he calls Uthaconus new species 1. He originally reported this species from Texas (Miller, 1984) , but has yet to formally name or describe the species.
Number of specimens.— 2. Repository.— University of Montana Museum of Paleontology. 68
Explanation of Plates Cordvlodus anaulatus Plate 1, figs. 1, 2, 4, 8. Cordvlodus lindstromi Plate 1, figs. 3, 7. Cordvlodus caboti Plate 1, fig. 5, Plate 2, fig. 2. Frvxellodontus inornatus Plate 1, fig. 6. Rossodus manitouensis Plate 1, fig. 9, Plate 2, fig. 8 ? Oneotodus so. Plate 2, fig. 1. Utahconus utahensis Plate 2, fig. 3. Teridontus nakamurai Plate 2, fig. 4. Utahconus New Species 1 (Miller, 1984) Plate 2, fig. 5 Semiacontiodus lavadamensis Plate 2, Semiacontiodus noaamii Plate 2, fig. 7 Genus so. unident. Plate 2, fig. 9.
PLATE 2 7f)
A REFERENCES Abaimova, G. P., 1971, Nowye ranneordovikskiye konodonty yugo-vostoka Sibiriskoy platformy: Akad. Nauk SSSR, Paleontol. Zhurnal, no. 4, p. 74-81, pl.10. ------/ 1972, Kompleksy konodontov v ordovike yugovostoka Sibirskoy platformy: Sov. Geol., no. 10, p.124-130. ------/ 1975, Ranneordoviskii conodonty sredeva techniiya r. Leny: Sibirskogo Nauchno-issed. Inst. Geol. Geofiz. Minerai. Syrya (SNIIGGIMS), T r . , v. 207, 137 p., 10 pl. ------, and Markov, E. P., 1977, Pervye Nakhodki konodontov Nezhnerordoviskoi Zony Cordvlodus oroavus na yuge Sibirskoy platformy: Akad. Nauk SSSR, Sibirskoe otd., Inst. Geol. Geofiz., Tr., v. 372, p. 86-94, pl. 14, 15. An, T., 1981, Recent progress in Cambrian and Ordovician conodont biostratigraphy in China: Geol. Soc. Am. Spec. Pap. 187 : p.209-224, 4 pis., 3 text-figs. — , 1982, Study on the Cambrian conodonts from North and Northeastern China: Sci. Rep. Inst. Geosci. Tsukuba, Sec. B, 3: p. 113-159, 7 pis., 9 text-figs. — f and Yang Chang-shen, 1980, Cambro-Ordovician conodonts in North China, with special reference to the boundary between the Cambrian and Ordovician Systems, in Scientific papers on geology for international exchange, prepared for the 26th International Geological Congress, Part 4, Stratigraphy and Palaeontology: Publishing House of Geology, Beijing, p.7-14. — , Zhang, F., Xiang, W., Zhang, Y., et al., 1983, The Conodonts of the North China and Adjacent Regions: p. 1- 233, 33 p i s . , 14 text-figs. (in Chinese, with English Abstract) Beijing. Apollonov, M.K., Chugaeva, M. N . , and Dubinina, S. V., 1984, Trilobites and Conodonts from the Batyrbay Section (Uppermost Cambrian -Lower Ordovician) in Malyi Kratan Range (atlas of the palaeontological plates): Akad Sci. Kazakh SSR, Nauka Kazakh SSR Publishing House, 48 p., 32 pis., Alma Ata. Bagnoli, G., Barnes, C. R., and Stevens, R. T., 1987, Lower Ordovician (Tremadocian) conodonts from the Broom Point and Green Point, western Newfoundland: Bollettino della Societa Paleontologica Itliana 25 (2), p. 145-158, 2 pis. Barnes, C.R., 1988, The proposed Cambrian-Ordovician global Boundary stratotype and point (GSSP) in Western Newfoundland, Canada: Geological Magazine, 125, p.381-414. Barnes, C.R., and Farhraeus, L.E., 1975, Provinces, communities, and the proposed nektobenthic habit of Ordovician conodontophorids: Lethia, v. 8, p.133-149. Bergstrom, S- M., and Sweet, W.C., 1966, Conodonts from the Lexington Limestone (Middle Ordovician) of Kentucky and its lateral equivalent in Ohio and Indiana: Bull. Am. Pal. 50, (229): p.269-442. Bush, J. H., Kachek, D.C., and Webster, G.D., 1985, Newly
71 72 discovered Ordovician strata, Libby Trough northwestern Montana: Geol. Soc. Am. Abstracts with Programs, v .17, p.211. Chen, Jun-yuan and Gong Wei-1 i, 1986, Conodonts: in Chen, J., ed., Aspects of the Cambrian-Ordovician Boundary in Dayangcha, China (Contribution to the Dayangcha International Conferencenon the Cambrian-Ordovician Boundary) p.93-313, 82pls., China Publishing House, Beij ing. Chen, Jun-Yuan, Qian, Yi-Yuan, Zhang, Ju-Ming, Lin, Yao-Kun, Yin, Lei—Ming, Wang, Zhi-Hao, Wang, Zhong-Zhe, Yang, Jie- Dong, and Wang, Ying-Xi, 1988, The recommended Cambrian- Ordovician global Boundary stratotype of the Xiaoyangqiao section (Dayangcha, Jilin Province), China: Geological Magazine, v. 125, no.4, p.415-444. Deiss, C., 1936, Revision of type Cambrian formations and sections of Montana and Yellowstone National Park: Geological Society of America Bulletin, v. 47, no. 8, p.1257-1342. Derby, J.R. , Lane, H.R., and Norford, B.S., 1972, Uppermost Cambrian-basal Ordovician fauna1 succession in Alberta and correlaztion with similar sequences in the western United States: Int. Geol. Congr., 24th Sess., Sec.&., p. 503-512. Druce, E. C., and Jones, P. J., 1971, Cambro-Ordovician conodonts from the Burke River structural belt, Queensland: Australia Bur. Mineral Resour., Geol., Geophys., Bull. 110, 158 p., 33 figs., 20 pis. Erdtmann, B. -D., and Miller, J. F., 1981, Eustatic control of lithofacies and biofacies changes near the base of the Tremadocian, in Taylor, M. E. (ed.) Short papers for the 2nd International Symposium on the Cambrian System: U. S. Geological Survey Open-File Report 81-743, p.78-81. Ethington, R.L., and Clark., 1965, Lower Ordovician conodonts and other microfossils from the Columbia Ice Fields section, Alberta, Canada : Brigham Young University Res. Stud., Geol. Ser., v. 12, p. 185-205, 2 pis. ------, and , 1971, Lower Ordovician conodonts in North America, in Symposium on conodont biostratigraphy, W.C. Sweet and S. M. Bergstrom (eds.), Geol. Soc. Am., Mem. 127, p.63-82, 2 figs., 2 pis. ——————————— ^ and ^ 1981, Lower and Middle Ordovician conodonts from the Ibex Area Western Millard Country, Utah: Brigham Young University Geology Studies, 28, p.l- 555. ^ and Repetski, J. E ., 1984, Paleobiogeographic distribution of Early Ordovician conodonts in central and western United States: Geol. Soc. Am. Spec. Pap. 196, p. 89-101, 4 figs. Farhaeus, L.E., and Nowlan, G. S., 1978, Franconian (Late Cambrian) to Early Champlainian (Middle Ordovician) conodonts from the Cow Head Group, Western Newfoundland: J. of Paleont., 52, p. 444-471, 3 pis., 9 text-figs. 73 Folk, R. D., 1962, Spectral subdivision of limestone types. In Classification of Carbonate Rocks— a Symposium (W. E. Ham, Ed.) 62-84. Am. Ass. Petrol. Geol., Tulsa. Fortey, R. A., Landing, E., and Skevingston, D., 1982, Cambrian-Ordovician boundary sections in the Cow Head Group, western Newfoundland. In M. G. Bassettm and W. T., Dean (eds.) The Cambrian-Ordovician boundary: sections, fossil distribution, and correlations: National Museum of Wales, Geol. Ser. 3, p. 95-129, 3 pis., 9 text-figs. Furnish, W. M. , 1938, Conodonts from the Prairie du Chien (Lower Ordovician) beds of the Upper Mississippi Valley: J. of Paleont., 12, p. 318-340, 2 pis., 2 text-figs. Goodwin, P.W., 1961, Fauna and stratigraphy of the Cambrian and Lower Ordovician of the Bighorn Mountains, Wyoming: unpub. M.S. thesis, Univ. of Iowa. Goodwin, P. W., 1964, Ordovician formations of Wyoming: unpub. Ph.D. thesis, Univ. of.Iowa Grant, R.E., 1965, Faunas and stratigraphy of the Snowy Range Formation (Upper Cambrian) in southwestern Montana and northwestern, Wyoming: Geol. Soc. Am., Mem. 96, 171 p. Hanson, A.M., 1952, Cambrian stratigraphy in southwestern Montana: Montana Bureau of Mines and Geology Memoirs 33, 46 p. Hass, W. H. , 1962, Conodonts: in R.C. Moore (ed), Treatise on Invertebrate Paleontology, Part W, Miscellanea, p.W3- W69,text-fig. 1-42, Geological Society of America and University of Kansas (New York and Lawrence). Hedberg, H. D. , 1976. International Stratigraphie Guide. New York: John Wiley. 200 p. Hinde, G. J., 1879, On conodonts from the Chazy and Cininnati Group of the Cambro-Silurian, and from the Hamilton and Genesee-shale divisions of the Devonian in Canada and the United States ; Q.J. Geol. Soc. London, v. 35, p. 351-369, pi.15-17. Hintze, L. F., Miller, J. F., and Taylor, M. E., 1980, Upper Cambrian-Lower Ordovician Notch Peak Formation in western Utah: U. S. Geological Survey Open-File Report 80-776, 67 p. Johnson, J. G., 1979, Intent and reality in biostratigraphic zonation: Journal of Paleontology v.53, p.931-942. Jones, P. J., 1971,Lower Ordovician conodonts from the Bonaparte Gulf Basin and the Daly River Basin, northwestern Australia : Australia Bur. Min. Res. Bull. 117: 80 p. 8 pis. Kajlo,D., Heinsalu, H., Mens, K., Puura, I., and Viira, V., 1988, Cambrian-Ordovician Boundary beds at Tonismagi, Tallinn, North Estonia : Geological Magazine, v. 125, no. 4, p .457—463. Kurtz, V. E., 1976, Biostratigraphy of the Cambrian and Lowest Ordovician, Bighorn Mountains and associated uplifts in Wyoming and Montana: Brigham Young University Geology Studies v. 23, p.215-227. 74 Landing, E., 1983, Highgate Gorge: Upper Cambrian and Lower Ordovician continental slope deposition and biostratigraphy, northwestern Vermont: J. of Paleont., 57, p. 1149-1187, 11 text-figs. ------/ and Barnes, C. R., 1981, Conodonts from the Cape Clay Formation (Lower Ordovician), southern Devon Island, Artie Archipelago: Can. J. Earth Sci., 18: p.1609-1628, 4 pis., 3 text-figs. ------/ Ludvigsen, R., and von Bitter, P. H., 1980, Upper Cambrian to Lower Ordovician Conodont Biostratigraphy and Biofacies, Rabbitkettle Formation, District of Mackenzie: Life Sci. Contr. R. Ontario Mus., 126., 42 p., 8 text-figs. ------, Taylor, M. E., and Erdtmann, Bernd-Dietrich, 1978, Correlation of the Cambrian-Ordovician boundary between the Acado-Baltic and North American faunal provinces: Geology, v.6, no.2, p.75-78, 3 figs. Lee, Ha-Young, 1975, Conodnts from the Upper Cambrian formations, Kangweon-Do, South Korea and its stratigraphical significance: Yonsei-Nonchong, v. 12, p. 71-89, 2 figs., 1 pi. Lindsey, D.A., 1980, Reconnaissance geologic map of the Big Snowies Wilderness and contiguous rare II study areas, Fergus, Golden Valley, and Wheatland Counties, Montana: Department of the Interior United States Geological Survey, Miscellaneous Field Studies Map MF-124 3A. Lindstrom, Maurits, 1955, Conodonts from the lowermost Ordovician strata of south-central Sweden: Geol. Foren. Stockholm. Forh, bd. 76, p. 517-604, 6 figs., 10 pis. ------, 197 3: in Catalogue of conodonts, Willi Ziegler (ed.), V. 1, 504 p., E Schweizerbart*sche Verlagsbuchhandlung (Stuttgart). Lochman-Balk, C., 1956, The Cambrian of the Rocky Mountains and southwest deserts of the United States and adjoining Sonora Province, Mexico, in Rodgers, John (ed.) Australia, America, pt. 2 of El Sisterna Cambrico, su paleogeografia, y el problema de su base: XX Congresso Geologico International, Tomo II, p. 529-660. Lochman, C., and Duncan, D., 1950, The Lower Ordovician Bellefontia fauna in central Montana: J. of Paleontol., v. 24, no. 3, p. 350-353. Miller, J. F. , 1969, Conodont fauna of the Notch Peak Limestone (Cambro-Ordovician), House Range, Utah: J . of Paleontol., v. 43, p. 413-439, 5 figs., pi. 63-66. ————————^ 197 0, Conodont evolution and biostratigraphy of the Upper Cambrian and lowest Ordovician: unpubl. Ph.D. dissertation, Univ. Wisconsin, 135 p., 20 figs., 1 pl., 3 tables. ------, 1971, Trempealeauan conodonts: in Conodonts and biostratigraphy of the Wisconsin Paleozoic, D. 1, Clark (ed.), Wisconsin Geol. Surv., Inf. Circ. 19, p. 4-9, 78- 81, 3 figs., pi. 1,2, 1 table. 75 ------, 1978, Upper Cambrian and lowest Ordovician conodont faunas of the House Range, Utah: in Upper Cambrian to Middle Ordovician conodnt faunas of western Utah, *J. F. Miller (ed.) SW. Missouri State Univ. Geosci. Ser. No. 5, p.1-33, 4 figs., 2 tables. ------f 1980, Taxonomic revision of some Upper Cambrian and Lower Ordovician conodonts with comments on their evolution: Univ. Kansas, Pal. Contr., 99, p.1-39, 2 pis., 6 text-figs. ------“ / 1984, Cambrian and earliest Ordovician conodont evolution, biofacies, and provincialism: Geological Society of America Special Paper 196, p. 43-68. , 1988, Conodonts as biostratigraphic tools for redefinition and correlation of the Cambrian-Ordovician boundary: Geological Magazine, 125, p. 349-362. ------, Taylor, M. E., Stitt, J. H., Ethington, R. L., Hintze, L. P., and Taylor, J. P., 1982, Potential Cambrian-Ordovician boundary stratotype sections in the western United States. In The Cambrian-Ordovician Boundary: Section, Fossil Distribution, and Correlations (ed. M. G. Bassett and W.T. Dean), p. 155- 180. National Museum of Wales, Geological Series No. 3. Mound, M. C. , 1968, Conodonts and biostratigraphy of the lower Arbuckle Group (Ordovician), Arbuckle Mountains, Oklahoma: Micropaleontology, v. 14, p. 393-434, 3 figs., 6 pis. Muller, K. J., 1959, Kambrische Conodonten: Dtsch. Geol. Ges. Z . , Bd. Ill, p.434-485, 11 figs., pi. 11-15. ------, 197 3, Late Cambrian and Early Ordovician conodonts from northern Iran: Iran Geol. Surv. Rep. 30, 77 p., 11 figs., 11 pis. Nicholl, R. S., 1991, Differentiation of Late Cambrian-Early Ordovician species of Cordvlodus (Conodonta) with biapical basal cavities: Australia Bur. Mineral Res., J. of Geol. Geophys., 12, no.3, p. 223-244, 18 figs. Nogami, Yasuo, 1966, Kambrische Conodonten von China, Tail 1, Conodonten aus den oberkambrischen Kushan-Schichten: Kyoto Univ., Coll. Sci., Mem. Ser. B, v . 32, p.351-367, pi. 9, 10. ------, 1967, Kambrische Conodonten von China, Teil 2, Conodonten aus den hoch oberkambrischen Yencho-Schichten: Kyoto University College of Science Memiors, Series B v. 32, p. 211-219, 1 pi. Nowlan, G.S., 1985, Late Cambrian and Early Ordovician conodonts from the Pranklinian Miogeosyncline, Canadian Artie Islands: J. of Paleont., 59, p.96-122, 10 text-figs. Ozgul, Necdet, and Gedik, Ismet, 197 3, New data on the stratigraphy and the conodont faunas of the Caltepe Limestone and Seydishir Formation, lower Paleozoic, of central Taurus Range: Geol. Soc. Turkey, Bull., v. 16, p.39-52, 2 figs., pl.l. Pander, C. H., 1856, Monographie der fossilen Fische des 76 silurischen Systems der Russisch—Baltischen Gouvernements: X + 91 p., 9 pis., K. Acad. Wiss. (St. Petersburg). Reeves, F ., 1931, Geology of the Big Snowy Mountains, Montana: United States Geological Survey Professional Paper 165-D, D135-D149. Repetski, J. E. , 1982, Conodonts from the El Paso Group (Lower Ordovician) of westernmost Texas and southern New Mexico: New Mexico Bur. Min. Miner. Res. , Mem. 40, p. 1- 117, 28 pis., 8 text-figs. - -, and Ethington, R.L., 1977, Conodonts from graptolite facies in the Ouachita Mountains, Arkansas and Oklahoma. In C. G . Stone (ed. ) Symposium on the Geology of the Ouachita Mountains: Arkansas Geol. Comm., 1, p.92-106, 2 pis. ------—— , and ------—— , 1983, Rossodus mantiouensis (Conodonta), a new Early Ordovician index fossil: Journal of Paleontology, v. 57, no.2, p. 289-301, 5 figs. - , and Perry, W.J.,Jr., 1981, Conodonts from the structural windows through Bane dome, Giles County, Virginia, Virginia Division of Mineral Resources, Publication, 27, Contribution to Virginia Geol. IV, p. 12- 22 [imprint 1980]. Seddon, George, and Sweet, W.C, 1971, An écologie model for conodonts: Journal of Paleontology, v. 45, p.869-880. Sloss, L.L., 1963, squences in the cratonic interior of north America: Geological Society of America Bulletin, v. 74, no. 2, p. 93-139. Stitt, J. H., 1977, Late Cambrian and earliest Ordovician trilobites, Wichita Mountians area, Oklahoma: Oklahoma Geol. Surv. Bull. 124, 79 p., 12 figs., 7 pi. Sweet, W. C., and Bergstrom, S. M., 1974, Provincialism exhibited by Ordovician conodonts faunas. In Ross, C.R. , (ed.), Paleogeographical provinces and provinciality: Society of Economic Paleontologists and Mineralogists Special Publication 21, p.189-202. Sweet, W. C. , Turko, C. A., Warner, E. , and Wilke, L. C. , 1959, The American Upper Ordovician Standard. I. Eden conodonts from the Cincinnati Region of Ohio and Kentucky: J. of. Paleont., v. 33, p. 1029-1068. Taylor, J . F. , Kennedy, D. J., Miller, J. F . , and Repetski, J.E., 1991, Uppermost Cambrian slope deposits at Highgate Gorge, Vermont: A minor misscorrelation with major consequences for conodont and trilobite-based chronocorrelation: J. of Paleont., v . 65, no. 5, p. 855- 863, 6 figs. Taylor, M. E. , and Landing, E. , 1982 Biostratigraphy of the Cambrian- Ordovician transition in the Bear River Range, Utah and Idaho, western United States. In M. G. Bassett and W.T. Dean (eds.) The Cambrian-Ordovician boundary: sections, fossil distributions and correlations: National Museum of Wales, Geol. Ser., 3, p.181-191, 5 text-figs. 77 ------/ and Miller, J. F., 1981, Upper Cambrain and Lower Ordovician stratigrapy and biostratigraphy, southern House Range, Utah, In Taylor,M.E., and Palmer, A. R.,(eds.) Cambrian stratigraphy and paleontology of the Great Basin and vicinty, western United States: Guide book for Field Trip 1, 0nd International Symposium on the Cambrian System, p. 103-119. Tipnis, R. S., Chatterton, B. D. E . , and Ludvigsen, R. , 1978, Ordovician conodont biostratigraphy of the southern District of Mackenzie, Canada. In C.R. Stelck and B. D. E. Chatterton (eds.) Western and Artie Canadian Biostratigraphy: Geol. Assoc. Canada, Spec. Pap. 18, p.39- 91, 9 pis., 3 text-figs. Van Wamel, W. A., 1974, Conodont biostratigraphy of the Upper Cambrian and Lower Ordovician of northwestern Oland, south-eastern Sweden: Utrecht Micropaleont. Bull. 10, 122p., 19 figs., 8 pis., 5 charts. Viira, Viive, 1970, Konodonty varanguskovy packi (verkhiny Tremadok Ectonii); Akad. Nauk Est. SSR, Izv., Khim. Geol., V . 19, p. 224-233, 10 figs., 1 pi. ------, 1974, Baltikumi Ordoviitsiumi konodondid: 142 p., 14 5 figs., 13 pis. , Akad. Nauk Est. SSR, Inst. Geol. (VALGUS) (Tallinn). Wang, Zhi-hao, 1984, Late Cambrian and Early Ordovician conodonts from North and Northeast China with comments on the Cambrian-Ordovician boundary. In Stratigraphy and paleontology of systematic boundaries in China. Cambrian- Ordovician Boundary (1), p. 195-258, pis.1-14, Anhui Sci.Tech. Publ. House (China).