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Conodont-based chronostratigraphy and conodont distribution across the Upper Ordovician western North American carbonate platform in the eastern Great Basin and a model for Ordovician-Silurian genesis of the platform margin based on interpretation of the Silurian Diana Limestone, central Nevada
Leatham, W. Britt, Ph.D.
The Ohio State University, 1987
U-M-I 300 N.ZcebRd. Ann Arbor, MI 48106
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University Microfilms International
COHODONT-BASED CHROHOSTRATIGRAPHY AND CONODONT DISTRIBUTION ACROSS THE
UPPER ORDOVICIAN WESTERN NORTH AMERICAN CARBONATE PLATFORM IN THE
EASTERN GREAT BASIN AND A MODEL FOR ORDOVICIAN-SILURIAN GENESIS
OF THE PLATFORM MARGIN BASED ON INTERPRETATION OF THE
SILURIAN DIANA LIMESTONE, CENTRAL NEVADA
DISSERTATION
Presented in Partial Fulfillment of the Requirements for
the Degree Doctor of Philosophy in the Graduate
School of The Ohio State University
by
W. Britt Leatham, B.A., M.Sc.
« x » * *
The Ohio State University
1987
Dissertation Committee: Approved by
W.I. Ausich
S.M. Bergstrom
L.A. Krissek Advisor W.C. Sweet Department of Geology and Mineralogy ACKNOWLEDGEMENTS
I thank my mentor, Dr. Walter C. Sweet, for insights on quantitative biostratigraphy and conodont paleontology. His expert advice, encouragement and stimulating discussions will always be remembered. I express gratitude to Drs. Stig M. Bergstrom, William I. Ausich, James W.
Collinson, and Lawrence A. Krissek for suggestions and comments that greatly enhanced this project. I thank the committee for a prompt and critical review of the manuscript.
Special thanks are directed to Dr. Anita G. Harris of the IISGS for access to her Ordovician-Silurian conodont collections from the Great
Basin and for permission to document critical collections from Pete
Hanson Creek and the Diana Limestone of central Nevada. Her hospitality, encouragement and lively discussions on conodonts are greatly appreciated.
I also wish to thank Dr. Peter M. Sheehan, Milwaukee Public Museum, for locality information and for many discussions on Ordovician-Silurian paleogeography of the eastern Great Basin.
Technical assistance rendered by Karlis V. Grinvalds (field assistance, 1983); Tony Leonard! (Scanning Electron Microscopy); and several work-study students (laboratory processing) is gratefully acknowledged.
ii Funding for field work in 1983 was provided by The Friends of Orton
Hall, Sigma Xi and a Chevron Field Studies grant.
My wife, Jami, and children (Brieanne and Ashley) endured my extended absences and the rigor3 associated with completion of a graduate degree. Their contribution to this document is perhaps the greatest of all.
iii VITA
July 11, 1956 ...... Born — Salt Lake City, Utah
1979 ...... • Paleontological Field Worker Intermountain Research Inc., Provo, Utah
1980 ...... Civil Engineering Technician U.S. Forest Service Materials Testing Facility, Salt Lake City, Utah
1981 ...... B.A. Geology, Weber State College, Ogden, Utah
1981 ...... Chemical Laboratory Technician Western Zirconium, Ogden, Utah
1981-1987 ...... Graduate Teaching Associate, Instructor, and Lecturer Department of Geology and Mineralogy, The Ohio State University, Columbus, Ohio
1 9 8 4 ...... M.Sc. Geology, The Ohio State University, Columbus, Ohio
1985-1986 ...... Amoco Doctoral Fellow in Micropaleontology, The Ohio State University, Columbus, Ohio
PUBLICATIONS
Leatham, W.B. 1987* A conodont-based, Late Ordovician chronostratigraphic framework for the eastern Great Basin [abst.]. Geological Society of America Abstracts with Programs, 19(5):313.
Leatham, W.B. 1987. Late Ordovician conodont distribution across the North American continental margin, eastern Great Basin [abst.]. Paleontological Society Symposium: Ordovician Radiations and Faunal Gradients, Geological Society of America Abstracts with Programs, 19(4):230.
iv Kleffner, M.A., W.B. Leatham, and W.C. Sweet. 1987. Ordovician ancestors for Silurian conodonts [abst.]. Geological Society of America Abstracts with Programs, 19(3):171.
Leatham, W.B. 1985. Age of the Fish Haven and lowermost Laketown dolomites in the Bear River Range, Utah. Utah Geological Association Guidebook 14:28-39.
Leatham, W.B. 1985. Stratigraphy and depositional environments of the Upper Ordovician and lowermost Silurian of Northern Utah [abst.]. Utah Geological Association 1985 Symposium on the Orogenic Patterns and Stratigraphy of North-Central Utah and Southeastern Idaho Program and Abstracts.
Leatham, W.B. 1985. Ordovician Ptiloncodus and the monogenean paradigm [abst.]. Geological Society of America Abstracts with Programs, 17(7):641.
Leatham, W.B. 1985. Late Ordovician conodont biofacies of the western North American midcontinent [abst.]. Geological Society of America Abstracts with Programs, 17(2):99.
Leatham, W.B. 1984. Conodont biostratigraphy of the Fish Haven and Laketown dolomites of Northern Utah [abst.]. Geological Society of America Abstracts with Programs, 16(3):152.
FIELDS OF STUDY
Major field: Paleontology
Studies in stratigraphy, biostratigraphy, paleobiology and conodont paleontology. Professors Walter C. Sweet and Stig M. Bergstrom.
Studies in paleoecology. Professor William I. Ausich.
Studies in carbonate petrology and depositional environments. Professor James W. Colllnson.
v TABLE OF CONTENTS
ACKNOWLEDGEMENTS ...... ii
VITA ...... iv
TABLE OF CONTENTS ...... vi
LIST OF FIGURES ...... viii
LIST OF TABLES ...... ,...... xiv
LIST OF PLATES ...... xv
CHAPTER I.— A LATE ORDOVICIAN, CONODONT-BASED CHRONOSTRATIGRAPHY FOR THE EASTERN GREAT BASIN ...... 1
ABSTRACT ...... 1 INTRODUCTION ...... 2 LITHOSTRATIGRAPHY ...... 3 METHODOLOGY ...... 10 LAKESIDE MOUNTAINS (83LA) 13 LONE MOUNTAIN (83LC) ...... 15 SOUTH EGAN RANGE C 8 3 L E ) ...... 17 BARN HILLS (83LF) ...... 18 SILVER ISLAND MOUNTAINS (83LB) ...... 19 TOANO RANGE (85LT) ...... 22 PETE HANSON CREEK (PHC) ...... 23 DISCUSSION...... 25 ORDOVICIAN-SILURIAN BOUNDARY ...... 28 CONCLUSIONS ...... 32 REFERENCES...... 33 ILLUSTRATIONS ...... 38
CHAPTER II.— "ONSHORE-OFFSHORE" CONODONT DISTRIBUTION ACROSS THE LATE ORDOVICIAN WESTERN NORTH AMERICAN CONTINENTAL MARGIN, EASTERN GREAT BASIN, U.S.A...... 80
ABSTRACT ...... 80 INTRODUCTION ...... 81 MORPHOGUILDS ...... 82 RELATIVE ABUNDANCE ANALYSIS ...... 87 CLUSTER ANALYSIS ...... 90 PRINCIPAL COMPONENTS ANALYSIS ...... 91
vi DISCUSSION...... 94 CONCLUSIONS ...... 97 REFERENCES...... 99 ILLUSTRATIONS ...... 103
CHAPTER III.— INTERPRETATION OF THE SILURIAN DIANA LIMESTONE, TOQUIMA RANGE, CENTRAL NEVADA, AND ITS PALEOGEOGRAPHIC IMPLICATIONS: EVIDENCE FROM MIXED CONODONT FAUNAS, CARBONATE PETROLOGY, AND STRATIGRAPHIC RELATIONSHIPS ...... 143
ABSTRACT ...... 143 INTRODUCTION ...... 143 LITHOSTRATIGRAPHY: A NAME FOR THE "UNNAMED” ...... 146 CONODONT FAUNA ...... 150 PALEOBIOGEOGRAPHIC AND PALEOECOLOGIC AFFINITY ...... 151 CORRELATION OF THE DIANA— MACROFAUNA...... 155 CONODONT BIOSTRATIGRAPHY ...... 156 GENESIS OF THE DIANA AND ITS PALEOGEOGRAPHIC SIGNIFICANCE .... 158 CONCLUSIONS ...... 163 REFERENCES...... 164 ILLUSTRATIONS ...... 172
GENERAL BIBLIOGRAPHY ...... 200
APPENDICES
APPENDIX A (Lithologic descriptions) ...... 214 APPENDIX B (Distribution and frequency of conodonts) ...... 250
vii LIST OF FIGURES
FIGURE 1.— Paleogeographic reconstruction of the Late Ordovician western North American continental margin. Wasatch Line = continental hinge, effectively separating Paleozoic epeirlc and continental margin sedimentation (Kay, 1951; Stokes, 1976). Location of paleoequator after Smith, Hurley, and Briden (1981). Same locational notation as figure 2. 38, 39
FIGURE 2.— Locality register and index map for sections used to effect the chronostratigraphic framework for the Upper Ordovician of the eastern Great Basin...... 40, 41
FIGURE 3.— Distribution of members in the Fish Haven and Ely Springs dolo3tones for localities listed in figure 2 ...... 42, 43
FIGURE 4.— Cobre lithofacies at the type section. Note dolostone clast imbrication, irregular bedding and alternating sequence of relatively light- and dark-gray dolostones. . . •...... 44, 45
FIGURE 5*— Schematic lithostratigraphic section of the Fish Haven Dolostone in the Lakeside Mountains (83LA). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphic divisions = dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I, = covered interval. Wavy lines = undulatory contacts. Dots = sampled horizons...... 46, 47
FIGURE 6.— Graphic correlation of 83LA with the CSS. Boxe3 = range bases. X = range tops. Biostratigraphically significant points are labeled. All 83LA species ranges are listed in Table 1. . . . 50, 51
FIGURE 7.— Schematic stratigraphic section of the Ely Springs Dolostone at Lone Mountain (83LC). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphicdivisions = dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I. = covered interval. Wavy lines = undulatory contacts. Dots s sampled horizons...... 52, 53
FIGURE 8.— Graphic correlation of 83LC with the CSS. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All 83LC species ranges are listed in Table 1. . . . 54, 55
viii FIGURE 9.— Schematic stratigraphic section of the Ely Springs Dolostone in the South Egan Range (83LE). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphic divisions = dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I. = covered interval. Wavy lines r undulatory contacts. Dots = sampled horizons...... 56, 57
FIGURE 10.— Graphic correlation of 83LE with the CSS. Boxes s range bases. X = range tops. Biostratigraphically significant points are labeled. All 83LE 3pecies ranges are listed in Table 1. . . . 58, 59
FIGURE 11.— Schematic stratigraphic section of the Ely Springs Dolostone in the Barn Hills (83LF). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphic divisions = dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I. = covered interval. Wavy lines = undulatory contacts. Dots = sampled horizons...... 60, 61
FIGURE 12.— Graphic correlation of 83LF with the CSS. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All 83LF species ranges are listed in Table 1. . . . 62, 63
FIGURE 13.— Schematic stratigraphic section of the Ely Springs Dolostone in the Silver Island Mountains (83LB). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphic divisions s dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I. = covered interval. Wavy lines = undulatory contacts. Dots = sampled horizons...... 64, 65
FIGURE 14.— Graphic correlation of 83LB with the CSS. Only two points provide LOC-defining arrays for the offset correlation. Therefore S and W have essentially no significance (= 0) in either of the offset lines of correlation. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All 83LB species ranges are listed in Table 1...... 66, 67
FIGURE 15.— Schematic stratigraphic section of the Ely Springs Dolostone in the Toano Range (85LT). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphicdivisions = dolostone unit3, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I. = covered interval. Wavy lines = undulatory contacts. Dots = sampled horizons...... 68, 69
FIGURE 16.— Graphic correlation of 85LT with the CSS. Only two points provide LOC-defining arrays for the offset correlation. Therefore S and W have essentially no significance (= 0) in either of the offset lines of correlation. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All 85LT species ranges are listed in Table 1...... 70, 71
ix FIGURE 17.— Graphic correlation of PHC with the CSS. Equations for the channel margins, one based solely on range bases, the other based on range top3, and the interpolated LOC in the center of the channel (dashed) are given. Width of channel = 16 meters. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All PHC species ranges are listed in Table 1. 72, 73
FIGURE 18.— -Chronostratigraphy of basal Upper Ordovician carbonates in the eastern Great Basin based on graphic correlation. Same locational notation as in figure 2. Computed position in CSS connected with lines for both transects. Error bar is maximum W in system (i.e. 6 meters). Error bar for PHC is width of channel. Transects both north and south of the Tooele Arch show that basal Upper Ordovician carbonates are consistently younger than their "offshore” counterparts...... 74, 75
FIGURE 19.— Chronostratigraphic Interpretation of lithofacies relationships of Upper Ordovician carbonates in the eastern Great Basin. CSS scaling computed from graphic correlation. Lack of interpretable facies relationships suggests strong, local tectonic controls on Upper Ordovician carbonate accumulation in the eastern Great Basin. Vertical bars = disconformity...... 76, 77
FIGURE 20.— Relative rates of rock accumulation at each of the seven studied localities compared with the Cincinnatian Standard Reference Section. Rate = slope of LOC...... 78, 79
FIGURE 21.— Localities of stratigraphically well-controlled conodont collections and generalized paleogeographic reconstruction of Late Ordovician western North America. The Wasatch Line or continental hinge (Kay, 1951; Stewart and Poole, 1974; Stokes, 1976; Picha and Gibson, 1985) separates epeiric sedimentation to the east from the western North American continental margin. Position of the paleoequator after Smith, Hurley and Briden (1981). All localities are identified in Table 2. 103, 104
FIGURE 22.— Sampled localities on two "onshore-offshore" transects across the Late Ordovician continental margin in Utah and Nevada. The northern transect, on the northern flanks of the Tooele Arch, includes sites 83LA, 83LB and 85LT. The southern transect, south of the Tooele Arch, includes sites 83LF, 83LE and 83LC and PHC. The generalized platform margin separates Upper Ordovician platform carbonates from carbonates deposited by sediment gravity processes. .... 105, 106
FIGURE 23.— Time-averaged relative abundance of the eight morphoguilds for the northern and southern transects. Locality notation same as Table 2 ...... 113, 114
FIGURE 24.— Time-averaged relative abundance of CONIFORM, RAMIF0RM, and RASTRATE "morphogroups” for the northern and southern transects. Locality notation same as Table....2 ...... 115, 116
x FIGURE 25.— Time-averaged Maysvillian relative abundance of the eight morphoguilds for the northern and southern transects. Locality notation same as Table 2 ...... 117* 118
FIGURE 26.— Time-averaged Richmondian relative abundance of the eight morphoguilds for the northern and southern transects. Locality notation same as Table 2 ...... 119* 120
FIGURE 27.— Q-mode unweighted pair group average linkage cluster analysis of euclidian dissimilarity coefficients computed from time- averaged morphoguild relative abundance for the northern and southern transects. Locality notation same as Table 2 ...... 121, 122
FIGURE 28.— Sympathetic variation of computed first principal component scores and total number of conodont elements per sample. Similar relationships are evident in samples from the other six localities used in this analysis. Line = total elements per sample. Bars = computed first principal component scores. Sample numbers = feet above top of Eureka Quartzite...... 127* 128
FIGURE 29.— Relationship between faunal associations and computed second principal component scores. 129* 130
FIGURE 30.— Faunal association relative abundance in samples with more than five elements. The sorted data set suggests gradational spatio- temporal faunal composition and lacks discrete clusters of samples with similar faunal proportions. . 131, 132
FIGURE 31.— Cumulative frequency plot of second principal component scores for the 243 samples used in the analysis. Except for sigmoidal ends, the lack of major inflections suggests gradational, not discrete, spatio-temporal faunal composition 133, 134
FIGURE 32.— Spatio-temporal fluctuation of second principal component scores for the northern transect. Temporal ordination of samples by graphic correlation (Leatham, chapter 1). Curves for 83LB and 85LT are discontinuous because of mid-Maysvillian to early Richmondian unconformities and late Richmondiancovered section...... 135, 136
FIGURE 33.— Spatio-temporal fluctuation of second principal component scores for the southern transect. Temporal ordination of samples by graphic correlation (Leatham, chapter 1)...... 137* 138
FIGURE 34.— Spatio-temporal morphoguild relative abundance for the northern transect. Temporal ordination of samples by graphic correlation (Leatham, chapter 1)...... 139, 140
FIGURE 35.— Spatio-temporal morphoguild relative abundance for the southern transect. Temporal ordination of samples by graphic correlation (Leatham, chapter 1)...... 141,142
xi FIGURE 36.— Outcrop belt of the Diana Limestone in the Ikes Canyon Window, Toquima Range, Nevada. The outcrops of the Diana are represented by the stippled pattern, and only occur in the Mill Canyon Sequence. A.C.S. = August Canyon Sequence, M.C.S. = Mill Canyon Sequence, J.C.S. = June Canyon Sequence. Major thrusts separating the three sequences are depicted with large "sawteeth” to distinguish them from minor thrusts that occur within sequences. Map is modified from Kay and Crawford (1964) and McKee (1976)...... 178, 179
FIGURE 37.— Schematic stratigraphic section of the Diana on the south wall of Ikes Canyon. Similar facies patterns are present throughout the outcrop area, although the stratigraphic sequence may vary. Sedimentary structures (i.e. synsedimentary folds) are vertically exaggerated. Phosphatic grainstone3 that characterize the base of the Diana at several localities are not present on the south wall of Ikes Canyon, but the base coincides with the abrupt appearance of the biostratigraphically mixed conodont fauna, disappearance of minor chert in the upper Antelope Valley, and occurrence of syndepo3itional deformation structures. Conodont samples from this locality are indicated by dots to the right of the column which correspond to samples 83LD-090 through 83LD-165 listed inTable 10 180, 181
FIGURE 38.— Schematic representation of Kay and Crawford's (1964) original concept of the Diana in the Mill Canyon Sequence. Except for inclusion of their "calcitite breccias" in the upper Antelope Valley, the random patterns of their massive calcarenite and well-bedded, somewhat "mottled" limestones indicate the inherent lateral variability in the original diagnosis. Facies thickness at each locality is approximate and is derived from the diagnosis (Kay and Crawford, 1964, pg. 437)...... 182, 183
FIGURE 39.— a) Carbonate Rudstone Facies on the south wall of Ikes Canyon. Note mixture of tabular and rounded subequant clasts, b) Contact print from acetate peel of polished slab with carbonate rudstone clast from Carbonate Rudstone/BrecciaFacies...... 184, 185
FIGURE 40.— a) Polymictic carbonate rudstones below "magic marker" grade vertically into raonomictic internal breccias (above marker) which also grade into the Well-bedded Limestone Facies at top of illustration. Marker is 12 cm long, b) Lithologic sequence of the Diana on the south flank of Copper Mt. Well-bedded limestones near the base of the formation are scoured and overlain by carbonate debris flows...... 186, 187
FIGURE 41.— a) Intraformational truncation surfaces in the Well-bedded Limestone Facies exposed on the south wall of Ikes Canyon, b) Slumps and syndepositional folding developed in exposures of the Diana on the southeast side of Copper Mt. 188, 189
xii FIGURE 42.— a) Syndepositional folding in slump/slide with internal "core11 (underlying sledge at center of photo) of carbonate rudstone/breccia. Exposure on southeast side of Copper Mt. b) Contact print from acetate peel of polished slab of Massive Laminated Facies from south wall of Ikes Canyon. Laminations are not recognizable on the outcrop...... 190, 191
FIGURE 43.— a) Relative percentages of all biostratigraphically significant conodont elements in samples collected from the Diana Limestone in Ikes Canyon, b) Percentage of biostratigraphically significant conodont elements plotted by sample. Several samples of cla3ts (e.g. 83LD-120c and 83LD-150c) and "whole rock" (clasts and matrix in samples 83LD-120w and 83LD-150w) were collected from the Carbonate Rudstone/Breccia Facies. The biostratigraphic composition of conodont faunas of those samples does not differ significantly, possibly because clasts are difficult to separate from matrix during sampling. 194, 195
FIGURE 44.— a) Contact print from acetate peel. Flame structure developed in the upper Antelope Valley Limestone on south wall of Ikes Canyon, b) Bouma A-C sequence in thin-bedded limestones of the upper Antelope Valley Formation on the south wall of Ikes Canyon. 196, 197
FIGURE 45.— Schematic representation of Ordovician-Silurian development and depositional processes of the outer continental margin profile in central Nevada (not to scale). Westernmost exposures of platform carbonates and sandstones occur at Lone Mountain and are incorporated into a generalized east-west trending transect through the Ikes Canyon Window 60 km to the northwest. Evolution of the margin occurred in three structural stages. STAGE 1— Offshore carbonates accumulated along a ramp extending west from the platform margin near Lone Mountain. Conodonts ranging from Ordovician Faunas 6 through 13, present in sediment gravity deposits of the Diana, suggest that accumulation of carbonate along the ramp was quasicontinuous. STAGE 2— Llandoverian subsidence of the ramp Induced downward flexure of the margin near the shelf-break, as evidenced at Lone Mt. Resultant ramp-steepening, coupled with flexure-induced seismic waves, effected general slope failure of the quasistable ramp. Emplacement of Diana carbonates by subaqueous slides, slumps, and sediment gravity flows occurred during this stage. Subaqueous removal of section along inter- and intraformational truncation surfaces was commonplace in carbonates west of the flexure. STAGE 3— The carbonate platform ea3t of the shelf-break near Lone Mt. prograded westward over sediment gravity deposits of the continental slope (Roberts Mountains Formation) after Llandoverian marginal flexure. This aggradational/progradational cycle terminated in the Lochkovian. T.R = Toquima Range; L.R. = Lone Mountain...... 198, 199
xiii LIST OF TABLES
TABLE 1.— Ranges of conodont species in Upper Ordovician sections of the eastern Great Basin. Ranges are stated in meters above the Eureka/Swan Peak-Upper Ordovician carbonate formational contact. Same locational notation as in figure 2 ...... 48, 49
TABLE 2.— Locality register of stratigraphically well-controlled conodont collections used in this study. 107, 108
TABLE 3.— Taxonomic composition of the eight Late Ordovician morphoguilds. 111, 112
TABLE — Eigenvectors (principal components), eigenvalues and associated variance of an uncentered, Q-mode principal components analysis on square-root transformed conodont elemental frequency. Only the first two principal components, which account for about 60% of the total variance, are readily interpretable 123, 124
TABLE 5.— Q-mode principal component loadings for the first three principal components...... 125, 126
TABLE 6.— Mixed conodont faunal assemblages of the Diana Limestone. 192, 193
TABLE 7--—Elemental frequency of conodont species from 83LA. .
TABLE 8.-— Elemental frequency of conodont species from 83LB. .
TABLE 9.-— Elemental- frequency of conodont species from 83LC. .
TABLE 10.--Elemental frequency of conodont species from 83LD . . . . 254
TABLE 11.— Elemental frequency of conodont species from 83LE. . . . 255
TABLE 12.— Elemental frequency of conodont species from 83LF. . . . 256
TABLE 13.— Elemental frequency of conodont species from 85LT. . . . 257
TABLE 14.— Elemental frequency of conodont species from PHC. .
xiv LIST OF PLATES
PLATE I.— Morphology of selected conodont elements assigned to the eight Late Ordovician morphoguilds described in the text. .... 109* 110
Plate II.— Scanning electron photomicrographs of representative Whiterockian and lower middle Ordovician conodont elements. Although representatives of illustrated conodont specimens occur throughout the Diana Limestone, figured specimens of Histiodella and Gen. et sp. indet. are from the uppermost beds of the Antelope Valley Limestone. Specimens are coated with gold-palladium and are reposited in the Orton Geological Museum at The Ohio State University...... 172, 173
Plate III.— Scanning electron photomicrographs of representative Middle and Late Ordovician conodont elements of the Diana Limestone. Specimens are coated with gold-palladiura. Hypotypes with OSU numbers (OSU //####) are reposited in the Orton Geological Museum at The Ohio State University. Hypotypes with USNM numbers (USNM tiifffitit#) are reposited at the United State National Museum and are from Anita Harris’ USGS collections...... 174, 175
Plate IV.— Scanning electron photomicrographs ofrepresentative Silurian conodont specimens from the Diana Limestone. All specimens are coated with gold-palladium. Hypotypes with OSU numbers (OSU are reposited in the Orton Geological Museum at The Ohio State University. Hypotypes with USNM numbers (USNM ######) are reposited at the United State National Museum and are from Anita Harris' USGS collections...... 176, 177
xv CHAPTER I.— A LATE ORDOVICIAH, CONODONT-BASED
CHROHOSTRATIGRAPHY FOR THE EASTERN GREAT BASIN
ABSTRACT.— Chronostratigraphic interpretation of the thick, Upper
Ordovician carbonate sequence in the eastern Great Basin has been imprecise. A poorly preserved, provincially restricted, calcareous macrobenthic fauna coupled with an inadequately understood lithostratigraphic sequence have hindered correlation of the Ely
Springs, Fish Haven, and Hanson Creek formations with the Cincinnatian stratotype.
Study of lithofacies relationships establishes two new Upper
Ordovician lithostratigraphic units: the Butterfield Springs and Cobre members of the Ely Springs Dolostone. The Butterfield Springs Member
(new name) includes all dark dolostones not intercalated with lighter lithologies immediately superposed on the basal quartz-sand-bearing Ibex
Member. The Cobre Member (new name) includes upper carbonate-ramp facies of the Ely Springs Dolostone and immediately overlies the
Butterfield Springs Member at its type section.
Based on study of more than 19,000 conodont elements contained in
184 samples collected from seven localities in western Utah and Nevada, a high-re3olution chronostratigraphic framework for the eastern Great
1 PLEASE NOTE:
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Basin Upper Ordovician is effected by graphic correlation of the ranges of 39 species with the Ordovician Composite Standard Section.
The correlations suggest that: 1) initiation of Late Ordovician carbonate accumulation over subjacent Eureka quartz-rich sand was diachronous, ranging from latest Edenian to late Maysvillian along an
"offshore-onshore’1 gradient; 2) elements of Gamachignathus,
characteristic of latest Ordovician Fauna 13 on Anticosti Island, are
chronostratigraphically equivalent with late Richmondian to post-
Richmondian Aphelognathus faunas; and 3) latest Ordovician rocks in the
eastern Great Basin range from late Richmondian to Gamachian in age.
IHTRODUCTIOH
Late Ordovician sedimentation in the eastern Great Basin is
represented by a sequence of dark- to light-gray, highly dolomitized
carbonates. Separated from epeiric sedimentation to the east by the
Wasatch Line (Kay, 1951; Stokes, 1976), these carbonates accumulated on
the passive, Lower Paleozoic, western North American continental margin
(see fig. 1). This "eastern assemblage" of Late Ordovician platform and
ramp carbonates extends westward into central Nevada and Idaho, where it
is tectonically juxtaposed against siliceous basinal facies (i.e. the
"western assemblage") of the Roberts Mountains Allochthon. Richmondian to post-Richmondian Aphelognafchua faunas; 3) that latest
Ordovician rocks in the eastern Great Basin range from late Richmondian to Gamachian in age; and 4) that carbonate accumulation in the eastern
Great Basin was controlled to a far greater extent by local characteristics of the platform (e.g. subsidence, uplift) than by eustacy.
Late Ordovician conodonts of the eastern Great Basin represent 50 species and comprise eight morphoguilds (new term). Morphoguilds are groups of morphologically similar species with poorly understood niche parameters. Relative abundance, Q-mode cluster and Q-mode principal components analyses suggest the existence of a conodont faunal gradient associated with the Late Ordovician western North American continental margin. Temporal fluctuation in faunal composition was probably related to Late Ordovician eustacy.
The Diana Limestone, exposed in the Mill Canyon Sequence of the
Ikes Canyon Window in the Toquima Range, Nevada, contains a biostratigraphically mixed conodont fauna. The fauna includes
Whiterockian through Late Llandoverian-Early Wenlockian species that characterize cold water, offshore niches. Diana lithofacies represent sediment gravity deposits chararacteristic of slope or distally steepened ramp environments. Stratigraphic concepts of the Diana
Limestone and the "unnamed limestones" of McKee (1976) and Ross (1970) are equated. Emplacement of Diana carbonates is most probably related to an Early Silurian flexure of the western North American continental margin, not to deposition on the eastern flank of the postulated Toiyabe
Ridge. Precise chronostratigraphic interpretation of the thick. Upper
Ordovician carbonate sequence based on raacrofaunal evidence is practically nonexistent. Macrofossils are typically poorly preserved and represent a provincially restricted calcareous macrobenthos broadly suggestive of the Late Ordovician (Budge, 1969, 1970, 1972, 1977; Budge
& Sheehan, 1968, 1980a; Buehler, 1955; Duncan, 1956; Elias 1983; Howe &
Reso, 1967; Langenheim et al., 1962; Richardson, 1913).
Over 19,000 conodont elements have been recovered from 189 samples at seven localities in western Utah and Nevada (see fig. 2). First and last occurrences of 39 species at those localities represent unique biostratigraphic events and are used to effect a high-resolution chronostratigraphic framework for the Upper Ordovician of the eastern
Great Basin by graphic correlation with the Ordovician Composite
Standard Section developed by Sweet (1979, 1984, in press; in Sweet and
Bergstrom, 1986).
LITHOSTRATIGRAPHY
Upper Ordovician carbonate lithologies in western Utah and Nevada include the Fish Haven Dolostone, the Ely Springs Dolostone and the
Hanson Creek Formation (listed in order of increasing distance from the continental hinge). Except for a condensed sequence near the shelf break in central Nevada (i.e. locality 83LC), the carbonates are remarkably constant in thickness and average about 150 meters thick (see fig. 3). u
The Fish Haven, Ely Springs and Hanson Creek formations are easily distinguished despite their lithologic similarity. Except for the Hanson
Creek, each formation has a distinct set of members. Typically, dark dolostones (i.e. Munsell values < - 5) are more common in the Ely
Springs than in the Fish Haven. The Hanson Creek Formation accumulated
near the shelf/slope break in central Nevada, and includes conspicuous sequences of limestone. Pervasive dolomitization distinguishes the Fish
Haven and Ely Springs dolostones from the Hanson Creek Formation.
Near the Wasatch Line in Utah and southeastern Idaho, the Fish Haven
Dolostone represents carbonate accumulation intergradational with
epeiric deposits of Bighorn Dolostone in the subsurface to the east.
The type section for the Fish Haven is near the Idaho/Utah state
boundary in the Bear River Range (Richardson, 1913)* The Fish Haven
includes three members (from bottom to top): the Paris Peak, Deep Lakes,
and Bloomington Lake members, which characterize the formation (Keller,
1963; Budge & Sheehan, 1980a, 1980b; Leatham, 1985).
The Paris Peak Member immediately overlies quartzose sandstones and
shales of the middle Ordovician Swan Peak Quartzite north of the Tooele
Arch (see fig. 2). Massive, cliff-forming, dark-gray (i.e. Munsell
values < = 5) dolostones with a common macrofauna that includes
pelmatozoa, rugosa, tabulata, and stromatoporoids characterize the Paris
Peak. The overlying Deep Lakes Member is represented by a series of predominantly light-gray, regularly bedded, medium-grained dolostones with a few darker interbeds. Calcareous macrobenthos are uncommon in this member. Sedimentary structures indicative of shallow subtidal to subaerial environments (e.g. intraclastic horizons, teepees, fenestral fabric) occur throughout.
The uppermost member, the Bloomington Lake, includes dark- and light-gray interbedded dolostones, many of which are bioturbated by
Thalassinoide3. The member i3 predominantly light- to medium-gray, fine-grained, and locally contains lenses of carbonate intra- to lithoclastic dolostone associated with some vagile macrofaunal elements
(e.g. nautiloids, gastropods) and a few orthid brachiopods.
The Ely Springs Dolostone is located between hingeline accumulations of the Fish Haven Dolostone to the east and outer shelf/3lope carbonates of the Hanson Creek to the west. Fotfr members have been defined by
Budge and Sheehan (1980a, 1980b): the Ibex, Barn Hills, Lost Canyon, and
Floride members. However, several of those members are geographically restricted and do not adequately describe the lithostratigraphy at key localities.
The Ibex Member (Budge & Sheehan, 1980a, 1980b) superpo3itionally overlies middle Ordovician Eureka Quartzite and is best developed near its type section in the Barn Hills of western Utah (i.e. site 83LF), where it reaches maximum thickness. Basal Ibex (= basal Ely Springs) 6 represents a change from dolomitic quartzose sandstone of the uppermost
Eureka to sandy dolostones. The basal contact is either sharp or gradational. Thickness of the Ibex varies. Quartz sand disseminated in a generally dark dolostone is a key criterion for identification of the
Ibex.
The Barn Hills Member (Budge & Sheehan, 1980a, 1980b) appears to be geographically restricted to the region surrounding its type section in the Confusion Range/Barn Hills of western Utah. Characteristically, the
Barn Hills Member overlies the Ibex Member (see fig. 3) and includes a series of dark- and light-gray, brownish to olive interbedded dolostones. Fenestral vugs are common and calcareous macrobenthos occur in very few of the thin- to medium-bedded, fine-grained dolostones. The
Barn Hills appears to represent shallow, subtidal to peritidal, somewhat restricted marine depositional environments on the southern flank of the
Tooele Arch, which was tectonically active during the middle Ordovician
(Hintze, 1954. 1959, 1974; Armstrong, 1968; Bick, 1966, Webb, 1956).
Several facies equivalents of the the Barn Hills and Lost Canyon members occur throughout the outcrop belt of the Ely Springs Dolostone.
Budge and Sheehan (1980b) recognized that the concepts of the Barn Hills and Lost Canyon members are difficult to apply at many localities.
Lithostratigraphically equivalent to the Barn Hills, the Butterfield
Springs Member (new name) overlies sandy dolostones of the Ibex Member in the lower Ely Springs Dolostone at localities other than those in the Confusion Range/Barn Hills of western Utah (fig. 3). Type section for the Butterfield Springs is in the South Egan Range of central Nevada
(see 83LE in locality register, fig. 2).
The Butterfield Springs includes a sequence of dark- to brown-gray
(Munsell values 1-5) dolostones that lack the prominent light-colored intercalations characteristic of the Barn Hills Member. Calcareous fossils are common and include; solitary and colonial rugosans, tabulates, orthid brachiopods, stromatoporoids, orthoconic nautiloids, gastropods and pelmatozoan debris. Bedding may be thin to medium, or absent. Bioturbation is common, but not prevalent at all Butterfield
Springs exposures. Burrows may be preferentially silicified. The
Butterfield Springs represents open-marine, subtidal environments and is depo3itionally similar to the Paris Peak Member of the Fish Haven.
The type section for the Lost Canyon Member in the Silver Island
Mountains (Budge and Sheehan, 1980a, 1980b) includes a series of interbedded light- and dark-gray dolomitized wacke- to packstones. Lost
Canyon lithologies include many dark horizons littered with oncoids (1-2 cm in diameter) and bioclasts. Laminated, bioturbated, and/or unfossiliferous horizons may be intercalated throughout. Bioclasts include solitary and colonial rugosans, gastropods, nautiloids, bryozoans, and pelmatozoan debris. Lost Canyon lithologies probably represent fluctuating subtidal to peritidal, high-energy to restricted marine deposition. The Lost Canyon Member may overlie the Barn Hills,
Butterfield Springs, or Cobre members (see fig. 2), 8
The Cobre Member (new name) is proposed for distinctive dolomitic lithofacies overlying the Butterfield Springs Member in the Toano Range
(site 85LT, see fig. 2). Exposures questionably similar to those at the type section occur at Lone Mt. (site 83LC).
At the type section, Cobre lithologies include interbedded light- and dark-gray dolostones and sedimentary structures indicative of sediment gravity deposition. Tabular and angular dolostone clasts occur both above and below scour surfaces. Clasts may be imbricated. Many beds vary greatly in thickness and pinch out laterally. Slumps, debris flows and flame structures are common (see fig. 4). Escape burrows, approximately 1 cm in diameter, occur in finely laminated dark dolostones. Several horizons are somewhat bioturbated. The calcareous
fauna includes solitary rugosans, nautiloids, and pelmatozoan debris.
The Floride Member (Osterwald, 1953, Budge & Sheehan, 1980a, 1980b) caps the dolostone sequence of the Ely Springs. Light- to medium-gray, finely to coarsely crystalline dolostones dominate. Floride lithologies
include burrow-mottled (i.e. Thalassinoides) dolostones, laminated
dolostones, bioclastic dolostones, fenestral dolostones, or light- colored sediment-gravity dolostone deposits. Generally, calcareous macrofaunal elements are not common in the Floride but tend to be most
abundant at "offshore" localities. Bioclasts include orthld and
strophomenid brachiopods, fragmentary solitary rugosans, gastropods, bryozoans, isolated dasycladacean thalli, oncoids, and orthoconic nautiloids. Frosted quartz sand is finely disseminated near the top of the Floride at many localities (e.g. Lone Mountain). Ooid-rich dolostones within the Floride occur at the South Egan Range (i.e. site
83LE) and at the Barn Hills (i.e. site 83LF). Floride lithologies suggest deposition in well-oxygenated, shallow, restricted to high- energy, and slope environments.
In central Nevada, Hanson Creek lithologies are extremely variable
(Dunham, 1977; Ro3s and others, 1979; Peter Sheehan, personal communication). At the type section (see fig. 2, site PHC), basal
Hanson Creek includes dark-gray, bioturbated, dolomitized grainstones and mudstones. Fine-grained (mudstone to wackestone) limestones dominate middle Hanson Creek lithologies. Uppermost Hanson Creek carbonates include medium- to light brown-gray dolomitized, bioturbated mudstones and ooid/oncoid-rich dolomitized grainstones (Dunham, 1977).
Typically, light-gray dolostones capping the Upper Ordovician sequence in the eastern Great Basin are overlain by dark dolostones of the basal Tony Grove Lake Member of the Laketown Dolostone, or by dark dolostones of the Roberts Mountains Formation. The contact is abrupt in all cases, and most probably represents a global, rapid transgression following Late Ordovician Gondwanan glaciation (Berry and Boucot, 1973;
Brenchley and Newall, 1980, 1984; Hambrey, 1985; McKerrow, 1979). 10
METHODOLOGY
Seven sections of Upper Ordovician carbonates in the eastern Great
Basin were chosen for this study, based on stratigraphic completeness, accessibility, and paleogeographic position on the Lower Paleozoic western North American continental margin. Collectively, those sections comprise two "offshore-onshore” transects across the margin on both the northern and southern flanks of the Tooele Arch (see fig. 2).
Standard laboratory processing of bulk samples for conodonts, collected at regular stratigraphic intervals (i.e. about 4.5 meters), yielded over 19,000 discrete elements, which represent more than 45 species. Species of Red River bioprovincial affinity (Sweet and
Bergstrom, 1984) are dominant.
Graphic correlation of maximized ranges of 39 conodont species in the Ordovician Composite Standard Section (CSS) (Sweet, 1979, 1984, in press; Leatham, 1985) with local first and last occurrences in the eastern Great Basin is used to develop a high-resolution chronostratigraphy for the eastern Great Basin.
Preliminary plots of local range data with the CSS suggested that ranges of several species are greater in the eastern Great Basin than in the CSS. Furthermore, these preliminary plots suggested a sequential strategy for correlation of the seven sections with the CSS. Individual correlations are discussed in that order. 11
A line of correlation (LOC) can be fit to the graphic array of common first and last occurrences. With few exceptions, the LOC effectively separates range tops from range bases in that array and provides a means for interpolating between points of selected biostratigraphic significance. Position of the LOC is determined by subjectively choosing points considered to represent unique biostratigraphic events near the maximum extent of their chronostratigraphic range in the CSS. In positioning the LOC, preference is given to parsimonious positions that extend ranges of the fewest species in the CSS. Extension of species ranges in
"conventional11 biostratigraphy operates under similar methodological constraints.
In this study, the equation for each LOC was computed by least- squares analysis of those common range bases and tops judged to best approximate the biostratigraphic relationship between particular eastern
Great Basin localities and the CSS. Points representing common first or last occurrences far from the axis of the graphic array (i.e. LOC) are not used for computation. Subsequently, confidence in a particular correlation increases as more events are used to position the LOC.
Computation of the equation of the LOC by least-squares may effect minor extension of species ranges (normally < = 1m) used to define the LOC. 12
Resolution (or precision) of graphic correlation is wholly dependent on the LOC-defining array of common events and i3 therefore dependent on the subjective significance attributed to points in that array. Two indices are currently used to evaluate resolution. The index W (Sweet
1979» 1984, in press; Sweet & BergstriSm, 1986) is the distance between two lines, parallel with the LOC, that demarcate edges of the LOC- defining array of points. Maximum precision of the graphic network is commensurate with the highest value of W computed from those sections which maximize ranges of events in the CSS. The maximum W in the CSS, without complete recorrelation of the graphic network because of range extensions documented in this study, is six meters (Sweet & Bergstrom,
1986).
Shaw (1964) evaluates resolution of graphic correlation with the
Standard Error of Estimate (S). S is the maximum dispersion of points in the LOC-defining array and is therefore a measure of the resolution of the correlation. Based on the number of LOC-defining events, levels of confidence can be attached to S. S is often greater than Vf because maximum dispersion is not necessarily parallel with the LOC.
After compilation of new range data from the eastern Great Basin
into the CSS during the first round of correlation, each section was serially recorrelated in the same rank order with the maximized range data in the CSS. Each recorrelation requires that ranges whose CSS positions are maximized by the correlation of that section with the CSS
be reset to the closest computed value. The recorrelation permits the best information available in the system to be compared with actual first and last occurrences in each section.
Extension of species ranges in the CSS suggested by the correlations in this study dictates another recorrelation of the partially adjusted
CSS with all of its constituent members. Such a recorrelation is beyond the scope of this project.
LAKESIDE MOUNTAINS (83LA)
Except for an unsampled covered interval near the base of section
83LA (see fig. 5), 29 samples collected at regular intervals from the
Fish Haven Dolostone yielded over 1200 Ordovician conodont elements.
Some of the color alteration indices (CAI) of conodont elements from this site are anomalously high. Values range from two to six. There is no coherent stratigraphic change in CAI values. CAI values vary within many samples. Such mixtures commonly occur in hydrothermally altered rock (Harris & Rejebian, 1986). Hydrothermal alteration is also evident along an unmapped fault near the base of the section.
Range information on 28 species Is used to effect the correlation of
83LA with the CSS (see table 1). The range base of Aphelognathus shatzerl and range tops of A. shatzeri, A. floweri, Drepanoistodus suberectu3, Rhipidognathus symmetricus and Belodina confluens define the LOC (see fig. 6).
The correlation suggests that local last occurrences of N.gen.n.sp.
A and Culumbodina occidentalis in the Lakeside Mountains are younger than their apparent maximized ranges in the CSS. C. occidentalis is a common constituent in lower Upper Ordovician strata in the western North
American Midcontinent (Sweet, 1979). Last occurrences of C. occidentalis at other localities in the eastern Great Basin are consistently younger than its current maximized range in the CSS, as dictated by parsimonious correlations of those localities. Those correlations verify the range extension dictated by the correlation of this section.
N.gen.n.sp. A is a rare species. Specimens of N.gen.n.sp. A. occur only in lower Upper Ordovician dolostones north of the Tooele Arch in the eastern Great Basin. Its range is poorly known. N.gen.n.sp. A was first documented in a section of the Fish Haven in the Bear River Range of northern Utah (Leatham, 1984). Correlation of the Fish Haven at that locality with the CSS (Leatham, 1985) permitted addition of the species and its range to the CSS.
The uppermost unit of the Fish Haven at this site is typical light- gray dolostone characteristic of the Floride Member. It is overlain by dark, fossiliferous dolostones of the lowermost Laketown. Ordovician conodonts from the uppermost unit of the Fish Haven, 151 meters above 15 the base, are assumed to continue to the top of the formation. Early
Silurian conodonts occur just above the Fish Haven-Laketown contact, 153 meters above the base of the section. Projection of the LOC to the lowest stratigraphic occurrence of Silurian conodonts suggests that the
CSS can be extended an additional meter into the post-Richmondian (i.e.
Gamachian).
LONE MOUNTAIN (83LC)
Westernmost exposures of Upper Ordovician dolostones include the condensed section of Ely Springs Dolostone at Lone Mountain (see fig.
7). Lack of limestone in the section precludes its assignment to the
Hanson Creek Formation. Furthermore, lithofacies at 83LC are more indicative of Ely Springs, rather than Hanson Creek lithologies.
More than 3700 conodont elements were recovered from 18 Ely Springs samples collected from the southwestern corner of Lone Mountain. CAI values consistently range from 2 to 2.5.
Correlation of 83LC with the CSS is effected by the ranges of 19 species (see table 1). The LOC is fit to six events: the range base of
Belodina stonei, and range tops of B. confluens, B. stonei,
Amorphognathu3 ordovicicus, Panderodus feulneri. and Walliserodus amplissimus (see fig. 8) 16
Based on the correlation, last occurrences of Belodina confluens,
Protopanderodus insculptus, Pseudooneotodus mitratus, and Walliserodus amplissimus are younger at 83LC than their computed range tops in the
CSS. Least squares analysis of the LOC-defining points suggests almost negligible extension of the the ranges of B. confluens and W. amplissimus. W. amplissimus was added to the CSS by correlation of site
82LA with the CSS (Leatham, 1985).
The distribution of Upper Ordovician Protopanderodus suggests that it preferred amphicratonic, "cold” and/or open-marine environments
(Sweet and Bergstrom, 1984; Leatham, unpublished data). Ranges of most
Late Ordovician species in the CSS are defined by midcontinent localities. Range extensions of species that preferred ”offshore" habitats, such as P. insculptus, should be expected as "offshore" localities are added to the graphic network.
The distribution of Pseudooneotodus mitratus is similar to that of
Protopanderodus in the Upper Ordovician. The initial range of P. mitratus in the CSS was determined by correlation of site 82LA with the
CSS (Leatham, 1985). The extension of its range top in the CSS is verified by correlation of site 83LE with its adjusted value in the CSS
(see fig. 10). 17
SOUTH EGAN RANGE (83LE)
Outcrops of the Ely Springs Dolostone at site 83LE (see fig. 9)
contain the most diverse and abundant conodont fauna in the eastern
Great Basin. Over 7.100 elements were recovered from 32 samples. CAI
values range from 1.5 to 2 throughout the section.
First and last occurrences of 33 species effect correlation of 83LE
with the CSS (see fig. 10). The most parsimonious LOC fits through
range bases of Aphelognathu3 shatzeri, Pseudobelodina vulgaris ultima.
Pristognathus bighornenslst Belodina stonei, Plegagnathus dartoni, and
Pristognathus? rohneri, and through range tops of B. confluens,
Parabelodina denticulata, A. divergens, and Pseudooneotodus mitratus.
The correlation necessitates three range modifications to the CSS:
the range base of Pristognathus bighornensis, the range top of
Pseudobelodina torta and addition of the range of Staufferella
lindstroemi. Prior to this study, specimens of P. bighornensis were known only from a short interval at two localities in the Upper Bighorn
Group of Wyoming (Sweet, 1979). Extension of the range base of P. bighornensis in the CSS by one meter is relatively insignificant.
Elements of Pseudobelodina torta, characteristically twisted about the longitudinal axis, are not abundant In conodont faunas of the Red
River Province. Lithologies indicative of relatively static environmental parameters in the Ely Springs Dolostone at site 83LE 18 coincide with the consistent stratigraphic occurrence of P. torta in the section. Apparently, paleoenvironraental factors favoring P. torta prevailed in the lower Ely Springs at 83LE and continued through strata much younger than the latest occurrence of the species computed into the
CSS. Extension of the last occurrence of P. torta in the CSS by about
30 meters suggests substantial paleoecologic control on its distribution
in both time and space.
Staufferella lindstroemi occurs in the lower Ely Springs Dolostone at site 83LE. The uppermost range of S. lindstroemi, previously ascribed to the mid-Cincinnatian (Sweet, 1982; Sweet, Thompson and
Satterfield, 1975), can now be added with confidence to the CSS.
BARH HILLS (83LF)
A relatively thick sequence of Ely Springs Dolostone caps the prominent escarpment of Eureka Quartzite on the northwestern corner of
Gettel Playa at site 83LF (see fig. 11). Thirty-seven samples of those
Upper Ordovician dolostones yielded over 1100 conodont elements. CAI values for those elements range from two to three.
Ranges of 17 species effect correlation of 83LF with the CSS (see table 1). Definition of the LOC is determined by the range base of
Belodina stonei and range tops of Aphelognathu3 divergens and
Rhipidognathu3 symmetricus (see fig. 12). The correlation suggests that the range of Aphelognathus divergens should be extended in the CSS. Sweet (1984) bases one of his chronozones on the first occurrence of A. divergens in the CSS. As indicated by this correlation, the range base of A. divergens should be extended from 1210 m to 1203 m, and thus lowers the base of the A. divergens chronozone in the CSS. A one meter extension of the range top of A. divergens in the CSS is also dictated by the correlation methodology.
SILVER ISLAND MOUNTAINS (83LB)
Over 2300 conodont elements were recovered from 30 Ordovician samples of the Ely Springs Dolostone (see fig. 13) at site 83LB in the northern Silver Island Mountains. CAI values for those elements range from about 2 to 8. At this locality, high indices are indicative of contact metamorphism and associated hydrothermal alteration. Sampled horizons at 83LB are cut by numerous igneous dikes, probably associated with the nearby Jurassic Crater Island pluton to the north, and normal faults.
First and last occurrences of 27 species permit correlation of 83LB with the CSS (see table 1). The most parsimonious correlation is shown in fig. 14.
The array of range bases and tops that occur more than 40 meters above the base of 83LB forms a distinct channel which effectively separates range base3 from tops in the middle and upper Ely Springs and thus brackets correlation. The left channel margin includes range bases of Gamachignathus ensifer, Plegagnathu3 dartoni, and Aphelognathus divergens. The right channel margin includes range tops of Plectodina tenuis and Pseudobelodina kirki. The LOC should fall between those margins.
Lines of correlation fit to either array of points defining the channel margins have anomalously steep slopes, suggestive’ of an absurdly high rate of rock accumulation at 83LB relative to the epicontinental
Cincinnatian Standard Reference Section (SRS). Paleogeographically,
83LB represents carbonate accumulations at or near the Late Ordovician platform margin (see fig. 2). Lithofacies interpretations at 83LB do not support such absurd accumulation rates.
The LOC drawn through the range top of Plectodina tenuis and the range base of Aphelognathus divergens has a much lower gradient than lines positioned along the channel margins. The gradient of that line is similar to gradients of lines of correlation computed for other platform localities in the eastern Great Basin (e.g. 83LA, 83LE, 83LF).
Analysis of relative abundance logs of paleoecologically important conodont species substantiates correlation of the upper 108 meters at
3ite 83LB (see fig. 14). At the scale suggested by the correlation, a prominent "spike" of shallow-water species in 83LB corresponds with a 21 mid-Richraondian platform- and continent-wide inflection in relative abundance (Sweet, 1979» 1984; Leatham, unpublished data).
The upper LOC cannot be parsimoniously projected below 38 meters, without effecting major range changes (see fig. 14). Indeed, the array of points in the lower Ely Springs at 83LB suggests an offset LOC, indicative of unconformity. A LOC fit through the range base of
Aphelognathus floweri and the range top of Culumbodina occidentalis best separates range bases from tops in the lower portion of 83LB. Slope of that LOC is similar to the slope of the upper LOC.
Lithologic evidence supports the unconformity suggested by correlation. An irregular, undulatory bedding-plane, 38 meters above the base of the Ely Springs at 83LB, coincides with the noted biostratigraphic change.
Furthermore an abrupt change in the general composition of the conodont fauna occurs at the unconformity. Samples immediately below the unconformity contain a diverse fauna, dominated by abundant specimens of Plectodina or PanderodU3. Above that datum, species diversity is low and samples are dominated by specimens of
Aphelognathus. 22
TOANQ RANGE (85LT)
Collections of over 2100 conodont elements from 31 samples of Ely
Springs Dolostone at 85LT (see fig. 15) provide the basis for correlation of this section with the CSS. Mixed, high CAI values characterize these collections. Values range from about four to seven, but higher values dominate the collections. Nearby intrusions and hydrothermal alteration appear to be the underlying sources for those high CAI values.
Ranges of 27 species effect the correlation (see table 1). The array of points, implied correlation, and lithostratigraphy of 85LT (see figs. 15 and 16) are markedly similar to site 83LB (cf. figs. 13 and
14). An upper LOC is best fit through the range base of Belodina stonei and the range top of Plectodina tenuis. Position of the upper LOC is further constrained by the range base of Pseudobelodina vulgaris ultima.
Based on the array of points, projection of the upper LOC below a datum 45 meters above the base of the section is untenable. A lower
LOC, passing through the range base of Aphelognathus floweri and the range top of Culumbodina occidentalis, effectively separates bases and tops below the 45 meter datum.
The offset lines of correlation imply disconformity in 85LT, which is Independently verified by lithostratigraphic interpretation and 23
conodont faunal composition. The base of the Cobre Member at this
locality, which is the type section, occurs 45 meters above the base of
the section. Lowermost Cobre dolostones represent of sediment gravity
depositional processes and are superposed on subaqueously scoured
subtidal deposits of the Butterfield Springs.
Uppermost Butterfield Springs conodont faunas at site 85LT are
typical of the lowermost Upper Ordovician of the eastern Great Basin.
Collections include abundant specimens of Panderodus, Plectodina, and
rastrate elements. The change in faunal composition at the Butterfield
Springs-Cobre contact is abrupt. Basal Cobre faunas are enriched in
Aphelognathus, presumably by downslope transport of conodonts and
sediments that accumulated east of the Toano Range.
As at site 83LB, correlation of the Cobre and Floride members at
85LT is also confirmed by correspondence with continent-wide inflections in conodont relative abundance (Sweet, 1979» 1984; Leatham, chapter II).
PETE HANSON CREEK (PHC)
Nine Ordovician samples collected from the type section of the
Hanson Creek Formation in the Roberts Mountains by Anita Harris (USGS) contain over 1600 conodont elements. CAI values range from 4 to 4.5. 24
Ranges of 21 species (see table 1) effect limited correlation of PHC
with the CSS (see fig. 17). A well-defined channel brackets correlation
possibilities. Range bases of Belodlna stonei, Pristognathus? rohneri,
and Walliserodus amplissimus form a distinct rectilinear array, which is
further constrained by the range base of Amorphognathus ordovicicus. A
line fit to that array establishes a lower limit for the correlation.
Another line positioned through range tops of Belodina confluens and
Plectodina tenuis establishes an upper limit for correlation. Both
lines have similar slopes.
Presently, a "tighter” correlation is not justified. Samples are
too widely spaced. Significant inflections in conodont relative
abundance are absent, possibly because of the sampling interval and/or
the "offshore” nature of the fauna (Leatham, chapter II). Furthermore,
no preferential biostratigraphic significance can be assigned to those points that define the channel margins.
A tentative LOC, essentially parallel with the channel margins, can be placed along the central axis of the channel. Although this LOC passes through no points, it represents the best correlation available with the existing data. The width of the channel is equilibrated with
W. The correlation effects no range extension in the CSS and therefore does not affect the maximum W for the graphic network. 25
DISCUSSION
Initiation of carbonate accumulation both north and south of the
Tooele Arch occurred diachronously, varying with ’’onshore-offshore" position (see fig. 18). Accumulation of Upper Ordovician carbonates immediately superposed on the Eureka Quartzite at "offshore" localities
(e.g. 83LC, PHC, 85LT) began in the latest Edenian-early Maysvillian.
Closer to the Wasatch Line, the lowermost Ely Springs or Fish Haven
(e.g. 83LA, 83LF) is middle to late Maysvillian.
This spatio-temporal mosaic is indicative of a gradual marine transgression. "Offshore" localities were inundated before localities closer to the craton. Sweet (1979) reports similar interpretations for coeval epicontinental carbonates of the western Midcontinent.
Sweet's (1979) results show that inundation of the craton was essentially complete by the early Maysvillian. However, my correlations show that basal carbonates blanketing Eureka sands at the Barn Hills
(83LF), which is the most "onshore" locality along the southern transect, are middle Maysvillian. 83LF represents carbonates that accumulated on the southern flank of the Tooele Arch. Continued, though relatively minor, uplift of the arch into the Late Ordovician may have delayed initiation of carbonate accumulation at that locality.
Several generalized effects of Late Ordovician sea-level changes are evident in the chronostratigraphic distribution of lithofacies (see fig. 26
19). Lithofacies of the Paris Peak and Butterfield Springs members seem
to suggest Maysvillian inundation of the platform (see fig. 19).
Generally, Richmondian depositional environments were shallower than those of the Maysvillian, as represented by the Lost Canyon, Deep Lakes,
Bloomington Lake, and Floride members.
After the diachronous establishment of Upper Ordovician carbonates on the western North American continental margin, isochronous or interpretable diachronous lithofacies patterns are not readily evident
(see fig. 19). The patterns seem to imply that Late Ordovician carbonate accumulation in the eastern Great Basin was apparently affected to a far greater extent by local characteristics of the platform (e.g. subsidence, uplift) than by Late Ordovician eustacy and/or regional sea-level changes (Sweet, 1979a, 1979b, Leatham, chapter
II).
The slope of the LOC shows the relative rate of rock accumulation compared with the CSS (see fig. 20). Generally, rock accumulation on the Late Ordovician carbonate platform in the eastern Great Basin was significantly higher than in the Cincinnatian stratotype. However, net rock accumulation decreased significantly in "offshore" localities at or near the shelf break (i.e. 83LC, 85LT, PHC). That reduction is probably related to slides, slumps, and net removal by subaqueous sediment gravity processes. At 85LT, which was situated on a carbonate ramp beyond the platform margin, higher accumulation rates in the upper and 27 middle Ely Springs Dolostone are be3t attributed to imbricate stacking of numerous sediment gravity flows.
Samples of the Ellis Bay Formation on Anticosti Island, Quebec, below a datum a few meters above the base of Member 6, contain conodont faunas enriched in Gamachignathus (McCracken and Barnes, 1981).
Ordovician conodont Fauna 13» recognized by dominant Gamachignathus, is equated with the Gamachian Stage and is thought to represent post-
Richmondian/pre-Silurian strata (McCracken and Barnes, 1981).
Correlation of the Late Ordovician sequence on Anticosti Island with the CSS is problematic (Sweet, in press). However, based on graphic correlation with the Cincinnatian stratotype, Sweet (1979» 1984, in press; in Sweet and Bergstrom, 1986) has recognized post-
Richmondian/pre-Silurian strata on the western North American
Midcontinent, which are tentatively equated with the Gamachian, > = 1275 meters above the base of the CSS.
The paleogeographic distribution of Gamachignathus in the eastern
Great Basin supports suggestions that the genus is amphicratonic
(McCracken, Nowlan, and Barnes, 1980; McCracken and Barnes, 1981).
Samples containing abundant Gamachignathus occur near the top of sections 83LB, 85LT, and 83LC. Each of those sections represents an
"offshore" area, at or near the platform margin. 28
Those samples also contain specimens of, among others, Plectodina tenuis, Amorphognathus ordovioicu3, and Phragmodus undatus. Plectodina is noticeably absent in the Ellis Bay Formation (McCracken and Barnes,
1981).
At all Great Basin localities, ranges of midcontinent species are used for correlation. The correlations show that "offshore" Fauna 13 is coeval with late Richmondian Aphelognathus-dominated faunas from
"onshore" localities. In effect, samples that contain Fauna 13 cannot be chronostratigraphically distinguished from late Richmondian counterparts and hence imply partial overlap of the Gamachian stratotype with the late Richmondian.
ORDOVICIAN-SILURIAN BOUNDARY
In 1985, the International Union of Geological Sciences (IUGS) approved the Moffat Shales at Dob's Linn, Moffat, Scotland as the
Ordovician-Silurian systemic boundary stratotype (Bassett, 1985). The boundary is currently established at the range base of the graptoloid
Parakidograptus acuminatus in the Birkhill Shale. Recognition of that event in carbonate platformal sequences is virtually impossible
(Lesperance, Barnes, Berry, Boucot and Mu, 1987; Lesperance, 1985), although Lesperance (1985) tentatively correlates the event with the first appearance of the trilobite, Acernaspis sp. The Ellis Bay Formation on Anticosti Island, Quebec is a key reference section for faunal changes in Ordovician-Silurian carbonate facies. Studies of conodonts at that locality suggest that a major conodont faunal turnover (McCracken and Barnes, 1981) closely coincides with similar extinctions and radiations of other fossil group3
(Lesperance, 1985). The conodont faunal turnover is marked by the disappearance of several well-defined Ordovician conodont genera (e.g.
Drepanoistodus, Phragmodus, Plectodina, Aphelognathus, Pseudobelodina,
Belodina, Amorphognathus, Gamachignathus, Staufferella and
Rhipidognathus) and the appearance of several genera (e.g. Distomodu3 and Kockelella?) that extend into strata that are assuredly Silurian
(McCracken and Barnes, 1981). No discernible unconformities are present in the reference section on Anticosti Island (McCracken and Barnes,
1981).
According to Lesperance (1985), specimens of Acernaspi3 sp. have been recovered from strata 30 to 80 meters above the conodont faunal turnover on Anticosti Island. Consequently, the conodont faunal turnover may be latest Ordovician and the chronostratigraphic assignment of species that first appear following the extinction of well-defined
Ordovician stocks is uncertain. Those species may be either latest
Ordovician or earliest Silurian (Lesperance, 1985).
For this study, in full recognition of the chronostratigraphic uncertainty associated with conodont faunas near the systemic boundary, species that first appear after the the Late Ordovician extinction are 30 referred to the earliest Silurian or Early Silurian. Samples that contain specimens indicative of those species are also designated lowermost Silurian or Lower Silurian. Although the designations are not chronostratigraphically verifiable, they help establish a chronologic sequence across the conodont faunal turnover.
In the eastern Great Basin, Late Richmondian and Gamachian conodont faunas are typically impoverished: elements are sparsely distributed and diversity is low. Conversely, at all sampled localities, lowermost
Silurian conodont species are fairly diverse and moderately represented.
The conodont faunal turnover typically occurs in platform carbonates at the formational contact between the Ely Springs or Fish Haven and the overlying Laketown or Roberts Mountains formations. Projection of the
LOC to the lowermost Silurian sample at each locality shows that the latest recognizable Ordovician strata at each locality vary in age (see fig. 19)• If the upper formational contacts represent latest Ordovician glacio-eustatic regression and a subsequent, Early Silurian rapid transgression (Berry and Boucot, 1973; Brenchley and Newall, 1980, 1984;
Hambrey, 1985; McKerrow, 1979)» then local tectonic controls (i.e. subsidence and uplift) on carbonate accumulation effectively mask that eustatic event.
At localities that record deposition near the carbonate platform margin (i.e. 83LC, 83LB), lowermost Silurian conodont faunas occur slightly below the Ely Springs-Roberts Mountains formational contact. 31
The overlying Silurian Roberts Mountains carbonates at both localities exhibit sedimentary structures indicative of Early Silurian slope failure, which modified the underlying shallow-water Floride Member.
Lowermost Roberts Mountains lithologies at 83LC include several horizons of internal breccias and neptunian dikes (Sheehan, 1986;
Leatham, unpublished data) suggestive of Early Silurian marginal flexure. Dark brownish gray dolostone with an abundant Early Silurian conodont fauna has infiltrated fissure systems in the underlying light- gray, quartz-sand-bearing dolostone of the uppermost Ely Springs. Light brownish gray dolostones of the lower Roberts Mountains at that locality are also definitely involved in the flexure event, although fissures filled with those Early Silurian sediments are difficult to define on the outcrop. The Ordovician-Silurian boundary at that locality is based on a sample of the fissure-filled interval about 1 meter below the base of the Roberts Mountains Formation. That sample produced an abundant
Early Silurian fauna, essentially identical to collections from the dark overlying bed.
The uppermost quartz-sand-bearing Ely Springs Dolostone at 83LB contains a diverse and abundant Early Silurian conodont fauna. Slides, slumps, and carbonate gravity deposits characterize the overlying lowermost Roberts Mountains Formation (Sheehan and Pandolfi, 1983;
Leatham, unpublished data). At that locality, the Ely Springs-Roberts
Mountains contact is Irregular and was probably modified by subaqueous, upper-ramp, sediment-gravity processes in the Early Silurian. 32
CONCLUSIONS
1.— Chrono- and lithostratigraphic interpretations suggest that local, passive-margin tectonism controlled carbonate deposltional patterns in the eastern Great Basin to a far greater extent than eustatic events during the Late Ordovician. Establishment of two new members, the
Butterfield Springs and Cobre members, and reevaluation of lithofacies relationships further illustrates the heterogeneity of Late Ordovician carbonate environments in the eastern Great Basin.
2.— Graphic correlation of conodont range data from seven Upper
Ordovician sections with the CSS produces a high resolution chronostratigraphic framework for the eastern Great Basin, and suggests that those Upper Ordovician carbonates range from latest Edenian/early
Maysvillian to Gamachian in age.
3.— Ranges of several species should be modified in, or added to, the
CSS. The affected species ranges include: 1) Aphelognathus divergens,
2) Belodina confluens, 3) Culumbodina occidentalis, 4) Gamachignathus ensifer, 5) N.gen.n.sp. A of Leatham (1984), 6) Pristognathus bighornensis, 7) Protopanderodu3 insculptus, 8) Pseudobelodina torta, 9)
Pseudooneotodus mitratus, 10) Scabbardella altipes, 11) Staufferella lindstroemi, and 12) Walliserodus amplissimus.
4.— A gradual transgression that progressed from west to east across the western North American continental margin induced Early to Middle 33
Cincinnatian carbonate accumulations assigned to the Fish Haven, Ely
Springs, and Hanson Creek formations.
5.--Peri-platform Fauna 13, characteristic of the Gamachian on Anticosti
Island, is at least a partial chronostratigraphic equivalent of late- to post-Richmondian Aphelognathus-dominated faunas common in platform environments.
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Budge, D.R., and P.M. Sheehan. 1968. Evaluation of Laketown Dolomite faunas, north-central Utah [abst.]. Geological Society of America Special Paper, 121:490-491.
Budge, D.R, 1969. Late Ordovician and Silurian coral communities, 34
eastern Great Basin [abst.]. Geological Society of America Abstracts with Programs, 1(5):10-11.
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Budge, D.R. 1972. Paleontology and stratigraphic significance of Late Ordovician-Silurian corals from the eastern Great Basin, unpublished Ph.D. Dissertation, University of California-Berkeley, pp. 1-572.
Budge, D.R. 1977. Biostratigraphy, biochronology, and some tectonic implications of Late Ordovician corals from the eastern Great Basin [abst.]. Geological Society of America Abstracts with Programs, 9(6):712.
Budge, D.R., and P.M. Sheehan. 1980a. The Upper Ordovician and Silurian of the eastern Great Basin, Part 1, Introduction.-Milwaukee Public Museum Contributions in Biology & Geology, 28:1-26.
Budge, D.R., and P.M. Sheehan. 1980b. The Upper Ordovician and Silurian of the eastern Great Basin, Part 2, Lithologic Descriptions. Milwaukee Public Museum Contributions in Biology & Geology, 29:1-80.
Buehler, E.J. 1956. The morphology and taxonomy of the Halysitidae. Peabody Museum of Natural History Yale University Bulletin, 8:1-79.
Duncan, H. 1956. Ordovician and Silurian coral faunas of western United States. United States Geological Survey Bulletin, 1021-F:209-236.
Dunham, J.B. 1977. Depositional environments and paleogeography of the Upper Ordovician-Lower Silurian carbonate platform of central Nevada, i£ J.H. Stewart, C.H. Stevens, and A.E. Fritsche (eds.), Paleozoic Paleogeography of the Western United States. Pacific Coast Paleogeography Symposium I. Pacific Section, Society of Economic Mineralogists and Paleontologists, pp. 157-164.
Elias, R.J. 1983. Late Ordovician solitary rugose corals of the Stony Mountain Formation, southern Manitoba, and its equivalents. Journal of Paleontology, 57(5):924-957.
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Hintze, L.F. 1959. Ordovician regional relationships in north-central Utah and adjacent areas. Intermountain Association of Petroleum Geologists Guidebook, 10:46-53.
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Leatham, W.B. 1984. Conodont biostratigraphy of the Ordovician-Silurian systemic boundary in the Fish Haven and Laketown dolomites of Northern Utah. Unpublished Masters Thesis, The Ohio State University, pp. 1-198.
Leatham, W.B. 1985. Ages of the Fish Haven and lowermost Laketown dolomites in the Bear River Range, Utah. Utah Geological Association Guidebook, 14:29-38.
Lesperance, P.J. 1985. Faunal distributions across the Ordovician- Silurian boundary, Anticosti Island and Perce, Quebec, Canada. Canadian Journal of Earth Science, 22:838-849.
Lesperance, P.J., C.R. Barnes, W.B.N. Berry, A.J. Boucot, and Mu En-zhi. 1987. The Ordovician-Silurian boundary stratotype: consequences of its approval by the IUGS. Lethaia, 20:217-222.
McCracken, A.D., G.S. Nowlan, and C.R. Barnes. 1980. Gamachignathus, a new multielement conodont genus from the latest Ordovician, Anticosti Island, Quebec. Geological Survey of Canada Paper, 80-1C:103-112.
McCracken, A.D., and C.R. Barnes. 1981. Conodont biostratigraphy and paleoecology of the Ellis Bay Formation, Anticosti Island, Quebec, with special reference to Late Ordovician-Early Silurian chronostratigraphy and the systematic [sic] boundary. Geological Survey of Canada Bulletin, 329:51-134.
McKerrow, W.S. 1979. Ordovician and Silurian changes in sea level. Journal of the Geological Society of London, 136:137-145. 36
Morris, H.T., T.S. Lovering, and H.D. Goode. 1961. Stratigraphy of the East Tintic Mountains Utah with a section on Quaternary deposits. United States Geological Survey Professional Paper 361:1-145.
Mullens, T.E., and F.G. Poole. 1972. Quartz-sand-bearing zone and Early Silurian age of upper part of the Hanson Creek Formation in Eureka County, Nevada. United States Geological Survey Professional Paper 800-B:21-24.
Osterwald, F.W. 1953. Thomas Range, Utah. United States Geological Survey Report TE1-330:104-106.
Richardson, G.B. 1913. The Paleozoic section in northern Utah. American Journal of Science, 4th Series, 36:406-413.
Ross, R.J. Jr. 1970. Ordovician brachiopods, trilobites, and stratigraphy in eastern and central Nevada. United States Geological Survey Professional Paper 639:1-103.
Ross, R.J. Jr., T.B. Nolan, and A.G. Harris. 1979. The Upper Ordovician and Silurian Hanson Creek Formation of central Nevada. United States Geological Survey Professional Paper 1126-C:C1-C15.
Sheehan, P.M. 1969. Upper Ordovician brachiopods from eastern Nevada [abst.]. Geological Society of America Abstracts with Programs, 1(5):72-73.
Sheehan, P.M., and J.M. Pandolfi. 1983. Upper Ordovician-Silurian deposition at the shelf-slope boundary in northern Nevada [abst.]. Geological Society of America Abstracts with Programs, 15(5):305.
Sheehan, P.M. 1986. Internal breccias at a carbonate-shelf margin, Silurian, Central Nevada [abst.]. Geological Society of America Abstracts with Program, 18(4):324.
Stokes, W.L. 1976. What is the Wasatch Line?, in^ J.G. Hill (ed.), Geology of the Cordilleran Hingeline. Rocky Mountain Association of Geologists, pp. 11-26.
Sweet, W.C. (1987) in press. Mohawkian and Cincinnatian chronostratigraphy. New York State Museum Bulletin 464.
Sweet, W.C. 1984. Graphic correlation of upper Middle and Upper Ordovician rocks, North Americna Midcontinent Province, U.S.A. in. D.L. Bruton (ed.), Aspects of the Ordovician System. Palaeontological Contributions from the University of Oslo, Universitetsforlaget, 295:23-35. 37
Sweet, W.C. 1979. Late Ordovician conodonts and biostratigraphy of the western Midcontinent Province. Brigham Young University Geology Studies, 26(3):45-85.
Sweet, W.C., and S.M. Bergstrom. 1986. Conodonts and biostratigraphic correlation. Annual Review of Earth and Planetary Sciences, 14:85- 112.
Sweet, W.C., T.L. Thompson, and I.R. Satterfield. 1975. Conodont stratigraphy of the Cape Limestone (Maysvillian) of eastern Missouri. Missouri Geological Survey Report of Investigations, 57:1-59.
Webb, G.W. 1956. Middle Ordovician stratigraphy in eastern Nevada and western Utah. American Association of Petroleum Geologists Bulletin, 42(10):2335-2377. FIGURE 1 Paleogeographic reconstruction of the Late Ordovician western Worth American continental margin. Wasatch Line = continental hinge, effectively separating Paleozoic epeiric and continental margin sedimentation (Kay, 1951; Stokes, 1976). Location of paleoequator after Smith, Hurley, and Briden (1981). Same locational notation as figure 2.
38 39
Pacific O
CCI i
Pftc
MER * 8 3 LS
DV LATE ORDOVICIAN
• B3 LF PALEOEQUATOR
FIGURE 1 FIGURE 2.— Locality register and index map for sections used to effect the chronostratigraphic framework for the Upper Ordovician of the eastern Great Basin.
HO 41
8 5 L T 83LB #8 3LA NEVADA T O O E L E ARCH
!• 8 3LC UTAH
8 3 L F 83L E
P L AT FQ ft to' M A ft G IN
100 MILES
loamTHsnrmi
sarncv mcanoN LATnUCE taCITIER TCWEHrPffiAiCE
82LA la k e sid e Mountains, Utah 40°51'14' Delle, Utah 7.5' Quad, to to SH* Sec. 13, T 2 !l. R 8 40°51'30* 132°45'44° Wi t IKfc Sec. «, I 1 H, R 8 V.
B3L3 Silver Is lard Mountains, Utah 3 9 0 5 3 .3 5 . ji3 «5 0 .2 3 ' Graham Peak, Utah 7.5' to to Quad, *Ek imsurveyed as^sa'so' 113°50'39' Sec. 25, T 3 H, R 18 V.
83IC Lone Mountain, Nevada 39°36'42' 116°16'39' Eartlne Ranch, Nevada to 35* Quad, Wi of 116*16'47* tnsurveyed Sec. 19, T 20 H, R 51 E.
83LE Scuch Egan Range, Nevada n4°58'00* Cavo Valley Veil, Nevada to 7.5’ Quad, SZr !Ek Sec. U 4 ° 5 8 ’16' 14 to SWt (Kfe Sec. 13, T 7 H, R 62 E.
8315 Earn HUls, Utah 38°59'03' 113°Z3'3L* Ihe Earn, Utah 15' Quad, to to Wot and Nr^ of Sec. 14, 3e°59’U # 113°23'49* T Z1 S, R 14 V.
65LT Toano Range, Nevada 41°02'09* l^'lS'tt" Cohre SE, Nevada 7.5’ to to Quad, UZt msurveyed 41°02’15* 114015'23' Sec, 2 i !»: unsurveyed Sec. 3, T 36 H, R 6 a E.
FHC Pate Hanson Creek, Nevada 39s 52’ 116° 19' Roberts Creek Mountain, [Anita Harris (U93S) unpublished (appro:.) (appro*.) Nevada 15' Quad, type collections] section, head of Pete Einscn Creek. T 23 II, R 50 E. FIGURE 2 FIGURE 3.— Distribution of members in the Fish Haven and Ely Springs dolostones for localities listed in figure 2.
42 LAKE- SILVER TOAHO BARH SOUTH LQHE SIDE ISLAND RANGE HILLS EGAN MT. MTS. MTS. RANGE
500' FLO- FLO- RIDE FLO- . RIDE MBR. 150 BLOOM RIDE MBR. FLO- RIDE 400- INGTON MBR. LAKE MBR. MBR*. LOST CAN LOST YON MBR. 309 LOST CAN 190 CAN YON YON MBR. DEEP MBR. LAKES MBR. COBRE 3 SO' BUTTER FLORIDE MBR. FIELD MBR. BUTTER BARN SPRINGS FIELD HILLS MBR. ?COBRE 50 SPRWGSj MBR. PARIS BUTTER- MBR. 100 PEAK MBR. FIELD MBR. SPRINGS! [butter H HBR. FIELD IBEX SPRINGS MBR. MeR. IBEX IBEX 0 [IBEX ! £ IBEXU O' FEET 83LA 83LB B5LT 03LF B3LE 83LC METERS |FISH HAVEH ELY SPRINGS DOLOSTONE
FIGURE 3 FIGURE 4.— Cobre lithofacies at the type section. Note dolostone clast imbrication, irregular bedding and alternating sequence of relatively light- and dark-gray dolostones.
44 FIGURE 4 FIGURE 5.— Schematic lithostratigraphic section of the Fish Haven Dolostone in the Lakeside Mountains (83LA). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphic divisions = dolostone units, which are described in Appendix A. Gray units = dark dolostones CMunsell values < = 5). C.I. = covered interval. Wavy lines = undulatory contacts. Dots = sampled horizons.
46 ■Cr -J ■ r* LAKE TOWN M AN 1 GAMACH 9- BLOOMINGTON LAKE MBR o. DEEP LAKES MBR PARIS PEAK MBR MAYSVILLIAN
eS > > * m a z a t N
FIGURE 5 TABLE 1.— flanges of conodont species in Upper Ordovician sections of the eastern Great Basin. Ranges are stated in meters above the Eureka/Swan Peak-Upper Ordovician carbonate formational contact. Same locational notation as in figure 2. TABLE 1
TABLE 1«— SrtClES KANCES IH IDE EASTHH CUAT BA5IH I SPECIES USED PCX CORRtUTIOH B3LA a i u t B3LB 83LB 6 ilC 03LC B3LE B3LE B3LF B3LP BSLT BSLT PHC PHC | CSS C5S j w i th nil css Leal top j bate top bai* top baa* top baa* top baa* top bate top (bate top |
JtiwrpAojnJtiiu# ardovlclcat (Brimon 6 Hehl) 27 52 101 124 22 39 )1130 1269 ] /phefognacAua d/vrrgana Sweet 78 7B | SS 75 134 163 41 137 46 73 ]1203* 1265*] Aphclojnathire f lo v c r l Sweet SS 114 j IB IB » 53 J1153 1256 | dpiielognatAv* s h a tte r ! Sweet 124 1S1 j 144 144 131 161 J 1264 12B9*( Apheipgnathwft sp. of Sweat (19791 SS 55 j 11165 1250 j S e lu d ln a caJc/prcjt/nena Sweet 27 92 | j 1169 1262 | Bwjpdina confluent Sweet 14 IB j 0 IB 0 9 0 23 0 IB 0 22 |1025 1172 j Btlodiat stoned Sweet 37 49 105 105 B7 92 7a 99 91 91 1233* 1264 j CoeJoeerorfeotu* tr l g o n iu tEthingtcn 25 23 0 so 5 5 9 57 |1015 1264 ( Calisnhodln* occidental/* Sweet 14 14 ) IB 37 0 0 0 14 5 27 0 9 j1104 1167*1 CultmbodJna penna Sweet 27 27 0 0 0 5 5 27 9 9 j1092 1167 j Dctpanelttodur tuberectus {Brmeon 4 Hehl) 14 1S1 | 0 137 0 49 0 164 0 161 0 151 0 110 j 680 1269*1 N.gen.n.ep, A of Laethaz (1934) 14 1* 1 14 14 3 S | 1141 1167*| Oulodut ulrichl {Stone t Purnlah) 14 96 j 0 101 B 23 0 143 0 137 0 101 9 U O | 1102 1288 | Panderodu* fvuJnerJ (Clanlatar) etneu lato 14 146 [ Q 143 0 61 0 141 O H e 0 151 0 1)0 1091 1Z89*] fanderodur pander/ (Stauffer) eenau lito 14 151 I 5 133 0 119 3 137 0 U O 793 12Bf*| Parab«Jpd/na drnt/cuiaca Sweet 21 23 1136 1172 j PhragKodqi undatue Beamon t Hehl 9 50 s 35 9 9 966 1282 | P lecto d in a acu/eato/dei Sweet 14 1* 1 0 32 0 23 0 5 0 9 1106 1244 j Plectodina florlda Sweet 96 96 t IB 82 0 49 3 114 5 124 0 0 |1102 1271 \ PlectodSn* tenuis (Srenioa 1 Hehl) 14 124 | 14 140 23 50 5 143 0 96 14 146 0 110 9B9 1272 j PJrgegnathui d e r to n l Stone 4 Furniih 110 110 j 105 105 96 101 1225 1269 j Piegagnethuc nelionf (Cthtngton & Furniih) IB 96 j 25 23 9 124 14 156 94 96 91 91 1129 1264 I Pr/atccnalAu* btgbocnenaIt Slone t Purniih 124 124 1249* 1262 j Prietognathuaf rohntrl (Ethlngten I Furnlah) 96 96 | B7 87 41 41 82 144 92 101 73 110 12)4 12B3 I ProeopanJeroduf Jaaculptua (Braneon 1 Hehl) 3 41 27 46 9 9 U U 1244*] PrutvpamteroJua U rlplput Kennedy, Barnee, 4 Uycno 22 72 980 1196 ] PaeudobeJwdina adentaca Sweet 22 U O ( 59 59 5 S 96 96 1163 1270 J Pstudabflpdint ilitptnta (GLeniiter) 14 IB | IB 101 0 49 0 B2 0 27 0 110 [ 985 1280 j Piaudoheiod/na inci/iutf (Beamon t Hehl) IS IB j 5 S 14 114 32 32 0 9 1092 1268 | Pseudobtiodipa kirk/ (Stone I Furnlth) 14 IB j 28 SO 0 9 0 27 14 32 5 27 | 1101 1237 ] Paei/dobeJod/na quadrat* Sweet IB 74 | 23 30 [ 1104 1270 j PaaudobeJod/na tort* Sweet 14 14 5 59 23 23 | 1104 1149*] PstuJobelodina vuifarie ujti« Sweat 142 146 | 144 144 156 161 137 137 j 1264 12B6 j Pieudobeiod/na vulgar/e v u lg a r is Sweet 14 1)4 j IB 137 0 S 0 143 3 B7 S 94 j lies 1273 j Ptaudoonaotodue mitcatus (KockalenVo} 5 IB 0 69 0 337 S 14 0 9 | * 1261*| IhJpidognacfiua s/aaetrlcus Branaon, Hehl 6 tranaon 74 157 | 73 73 134 134 41 154 39 73 | 1058 127S j Steufferelle brev/ap/natf McCracken 4 Barnea IB IB | 0 IB 50 73 32 101 ( HOB 1274 j VaJliaermfut asiplitsltva (Serpagll) 14 96 j IB 96 0 59 0 105 87 92 5 14 0 110 |1131 1203*| 1 t J 1 HISC* SPECIES RANGES 1 i t t I 1 D apeU odus cufcatus (Branson & htehl) IB IB 22 22 | r [ GiaudiignathnB cru/ier )fcCrackai, Itwinn t t o m w 137 142 50 50 137 151 | 1263* 1274*] mOl$taAitr vcnustus Stauffer 3 19 0 37 5 30 146 146 0 » 1 y [ Pscudtuneotodus fodbnimi (Qlsehoff t Sannarann) 49 49 0 SO 6 * \ *■ 1 SrahfiTftto/Je a l t i f X * (Muinlngucroon) IB IB S 50 0 39 137 146 G 9 ( I 1272 j Stauffnrslla JiAdstrtunf (EUUnntm C Sdurmchcr) 0 23 1 * 1171*1 * Range extention Affected by thte atudy
x Speclea known froa atratt older thin th* Upper Ordovician of the eiftcrn Greet Stein but nut coiapiled In the CSS
y Range not eatabllihed beeauee of taxonoalc uncertainty
t Specie* occur* In itnta both younger and older thin the Upper Ordovician of tfce>lectern Great lasln and the lower range ha« not been coapiled in the CSS
Rangel In eietera. -fcr VO FIGURE 6.— Graphic correlation of 83LA with the CSS. Boxes = range bases. X s range tops. Biostratigraphically significant points are labeled. All 83LA species ranges are listed in Table 1.
50 Q 3 Lft (METERS 199 - 1-38 163 -i 189 FIGURE 6 10 15 10 15 20 1225 1200 1175 1150 1125 1190 t C. occidentalis N.genus = S = METERS 3 -3- 1155 = W SS=0.885y C A METERS
AEIE MOUNTAINS LAKESIDE X-B. S (METERS) CSS confluen R. synuetricus R.synuetricus t -l i i ri— e w -flo ft. □ □ P. v . u ltin a —i a ltin u . v P. t shatzeri--/ - - i r e z t a h s ft, □. subsreclos — □.subsreclos 20 1275 1250 X i ------.pandeW ' w W e d n a P.p fi. shatzeri-r s q
\_ ~
r
i — 1300 51 FIGURE 7.— Schematic stratigraphic section of the Ely Springs Dolostone at Lone Mountain (83LC). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphic divisions r dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I.= covered interval. Wavy lines = undulatory contacts. Dots = sampled horizons.
52 00C
ROBERTS MOUNTAINS FM. LLANDOVERIAN a o M - 1 Z QAU. MBR, FLORIDE O (n COBRE? MBR. O a RICHMONDIAN
SPRINGS DOLOMITE BUTTERFIELD SPRINGS MBR. ELY ELY CINCINNATIAN MAYSVILLIAN =5 2m Sx o o 3 3 _ m 3 H c > o -I N ffl X
FIGURE 7 FIGURE 8.— Graphic correlation of 83LC with the CSS. Boxes = range bases. X = range tops. Blostratigraphically significant points are labeled. All 83LC species ranges are listed in Table 1. « 3 I_H (METERS) - 8 2 3 3 40 18 80 70 59- FIGURE 8 10 15 10 15 20 25 20 1275 1250 1225 1200 1175 1150 1125 1100 □ W » = METERS 6 = S S225 * 1151 * SS=2.255y C 1 . nlsiu * g * g; > ** anplissiuus W. l i i r i i i i El METERS 4 . l -j s n e flu n o c B. a X P? rohneri □ □ rohneri P? X .jsupu □' □ L P. jnsculpius OE MOUNTAIN LONE
S X y A W. anp . neri i i- r e ln u e f P. 1 smu issm A t 'A ) 'A t A ‘i A XX 5 A V —j y ;tonei " ' ' f J X X i — 1308 55 FIGURE g.—Schematic stratlgraphic section of the Ely Springs Dolostone in the South Egan Range (83LE). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphic divisions = dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.X. = covered interval. Wavy line3 = undulatory contacts. Dots = sampled horizons. 56 MAYSVILLIAN LAKE- TOWH IBEX T.fi.L. FLORtDE MBR MBR. MBR. FIGURE 10.— Graphic correlation of 83LE with the CSS. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All 83LE species ranges are listed in Table 1. 58 r. 129 1 129 r. D3LE (METER ! 0 100 1*30 160 160 1BQ1 29- 40- 6a - B9 IU E 10 FIGURE iiae - 5 ^ 9 ~ n □ 079 + 1154 + =0.769y S S C = METERS 4 = S METERS 5 = W D 15 10 15 20 1225 1200 1175 1150 1125 □ □ . X a t r o t P. L. ntc lata ticu en d —LP. X ^ □ _ OT EO RANGE EGON SOUTH ?X C penna C. X . ddent lis ta n e d cd o C. f B confluens rB. S (METERS) CSS ? ohner □ ri e n h ro P? . f i n rfo a d P. . ghor s □ X X X X. X. □ is s n e rn o h ig b P. □ . anei □ i e n ta s B. . t us s fu a itr n P. / . dvres E A. divergens . zeri-! r e tz a h s A. / 1256 1 ------/ X * X xx M 1275 r ^ X X X x 1300 FIGURE 11.— Schematic stratigraphic section of the Ely Springs Dolostone in the Barn Hills (83LF). Chronostratigraphic division of section suggested by graphic correlation. LIthostratigraphic divisions = dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I. = covered interval. Wavy lines = undulatory contacts. Dots = sampled horizons. 60 cr> 9 < ‘I? 1 J AU. 0 o o tfl FLORIDE MBR. t*. s DOLOMITE 5 5 ? h A . LOST CANYON MBR.BARN KILLS MBR. LOST CANYON MBR.BARN RICHMONDIAN M O SPRINGS CINCINNATIAN s i l I- ELY o o MAYSVILL1AN 9 3 3 _ EUREKA OTZT H O FIGURE 12.— Graphic correlation of 83LF with the CSS. Boxes = range bases. X = range top3. Biostratigraphically significant points are labeled. All 83LF species ranges are listed in Table 1. 62 Q3L.F □ fR HILLS BfiRN S X X / 1275 > X v 1300 63 FIGURE 13-— Schematic stratigraphic section of the Ely Springs Dolostone in the Silver Island Mountains (83LB). Chronostratigraphic division of section suggested by graphic correlation. Lithostratigraphic divisions = dolostone units, which are described in Appendix A. Gray units = dark dolostones (Munsell values < = 5). C.I. = covered interval. Wavy lines = undulatory contacts. Dots = sampled horizons. U1 MTS. FM. ROBERTS VERIAN LLANDO- I FLORIDE MBR. | o o 3 (J O ?- DOLOMITE RICHMONDIAN M O ± frfKl. I. U) o SPRINGS _!L CINCINNATIAN o o, _L_ BUTTERFIELD SPRINGS MBR. ELY V IL L IAN MAYS MBR. ■'j-aa: IBEX LOST CANYON MBR. a - a m m c * > a FIGURE 13 FIGURE 1*t.— Graphic correlation of 83LB with the CSS. Only two points provide LOC-defining arrays for the offset correlation. Therefore S and W have essentially no significance (= 0) in either of the offset lines of correlation. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All 83LB species ranges are listed in Table 1. 66 0 03LD inn IUE 14 FIGURE - S=.8y 1139 + CSS=8.783y S=.0y 1159 + CSS=0.807y UPR LOO (UPPER LWR LOO (LOWER . dent ls ta n e id c c o C. . ouer- ^/x c penna c< x / ^ rl-, e u lo P A. l . x .□ 3 IVR SAD MOUNTAINS ISLAND SILVER 1150 □ □ A . vr nsn en iverg d A. 1175 L . confluens B. ? ohneri-J n h ro P? S (METERS)CSS 1230 . d-artoni P. x I □ 1225 X 20 25 12O0 1275 1250 . snui , x / -, is u n ts P. i i i i : Sx X x: 68 C\ KO Cn m m \V*E 2 H = H o > fz o £ £ o a M H H cr z = OS 0 m GAM.' 8 8 31 31 ?- ; Ji5i Ji5i FLOBIDE MBR. s LOST CANYON MBR. RICHMONDI AN RICHMONDI A MM O O SPRINGS SPRINGS DOLOMITE C O B R EMBR. CINCINNATIAN o cn ■*:&&+ } * < • & ELY o o -JI i i MBR. BUTTERFIELD SPRINGS BUTTERFIELD MAYSVILL1AN t ! ! - IBEX MBB. O 3 3 FIGURE 15 FIGURE 16.— Graphic correlation of 85LT with the CSS. Only two points provide LOC-defining arrays for the offset correlation. Therefore S and V/ have essentially no significance (= 0) in either of the offset lines of correlation. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All 85LT species ranges are listed in Table 1. 70 85LT CMtTTERS) 100 129 140- -1 180 160- 29 40- 60-1 80 IU E 16 FIGURE 1106 0 i I u D .s. l A n.sp. □ ariplissinus I (LDWERL0C> 1134 ->CSS=1.211y 1189 -> CSS=0.5676y UPR LOG) (UPPER N.genus 1125 . dent i ' ^ ' - lis ta n e id c c o C. □ C. penna-! penna-! C. 1150 -X □ 1 . diuergens-i A. X OtO RANGE TOftNO 1175 - confluens . t-E . eu ns. A n.sp. genus N. S (METERS*CSS ^ - 1298 X P- tortaX . tje □ stcjnei B. P. □ 1225 uulgaris ultiaa-i X X P. 1250 tenuis—| X /-v V X f U " X K X YY * Y v X X B st i e n to s B. r X 251300 1275 . A X X ^ f V 71 FIGURE 17.— Graphic correlation of PHC with the CSS. Equations for the channel margins, one based solely on range bases, the other based on range tops, and the interpolated LOC in the center of the channel (dashed) are given. Width of channel = 16 meters. Boxes = range bases. X = range tops. Biostratigraphically significant points are labeled. All PHC species ranges are listed in Table 1. 72 PHC (METERS) 100 120 im IBS * ■ S=J8 + 17 1 1147- + «*»■ CSS=1J48y 60 B9 - 9 4 29- 1109 IU E 17 FIGURE - - D □ S=.2y 1131 - * CSS=1.127y N. aaplissimus 3=J3 v 1139 v C3S=1J33y A.ordauiclcu (BASES) (INTERPOLATED) (TOPS) 1125 □ 1150 EE ASN CREEK HANSON PETE . penna C. — X 1175 -. occidentalis [-C. S (METERS)CSS i r e n h o r 1200 N = 6 METERS 16 = "N" — l s n e flu n D C 1225 1250 * . s X X 1275 Ssrr xxxc . tenuis P. anei e n ta s 1300 73 FIGURE 18.— Chronostratigraphy of basal Upper Ordovician carbonates in the eastern Great Basin based on graphic correlation. Same locational notation as in figure 2. Computed position in CSS connected with lines for both transects. Error bar is maximum W in system (i.e. 6 meters). Error bar for PHC is width of channel. Transects both north and south of the Tooele Arch show that basal Upper Ordovician carbonates are consistently younger than their "offshore" counterparts. 74 wwn 1139 1158- 1160 - 1160 1178- IUE 18 FIGURE ORLTO O SCIN BASES SECTION OF CORRELATION 5T 3B 3A H 8L 8L 83LF 83LE 83LC PHC 83LA 83LB 85LT OFFSHORE-f-JONSHORE NORTHERH TRANSECT NORTHERH / V i i 1 i 1 i i l i * i i QFFSHORE<-*OHSHORE SOUTHERN TRANSECT SOUTHERN i 75 FIGURE 19-— Chronostratigraphic interpretation of lithofacies relationships of Upper Ordovician carbonates in the eastern Great Basin. CSS scaling computed from graphic correlation. Lack of interpretable facies relationships suggests strong, local tectonic controls on Upper Ordovician carbonate accumulation in the eastern Great Basin. Vertical bars = disconformity. 76 77 1308-> INORTHERN TRANSECT] SOUTHERN FLORJDE. TRANSECT MEMBER BLOOM 12B0 ■ INGTON LAKES MEMBER & ■ 1260 • LOST fc-v* v. V CANVOH MEMBER 1248 ■ COBRE MEMBER V V VVV vvvw VVVW DEEP 1220 - WVwVJfvvw LAKES &S588 yyyyyyvyvj/ MEMBER ivn.vyyxsc^ v x vvvyx BUTTER 1200- t S v v w 1 FIELD VWW VWW SPRINGS v V V W vA/vNA/ MEMBER 1 1 8 8 - PARIS PEAK MEMBER 11S8- BARN HILLS Jssijis J MEMBER 1148* IBEK MEMBER Z S . EGAN BARN CSS TOANO SILVER LAKESIDE LONE RANGE ISLAND MTS. Li MT. RANGE HILLS G m h ia t u s C85LT) (83LB ) CB3LA) Li <83LC) <83LE) CB3LF) FIGURE 19 FIGURE 20.— Relative rates of rock accumulation at each of the seven studied localities compared with the Cincinnatian Standard Reference Section. Rate = slope of LOC, 78 RELATIVE RATES OF ROCK ACCUMULATION IN THE EASTERN GREAT BASIN COMPARED WITH THE ClHCWNATIflfi STRATOTYPE Northern lransact TQfiHQ RANGE SILVER ISLAND MTS. LAKESIDE MTS. 1.211 0.733 0.805 0.56B 0.807 Southern Transect PETE HANSON CREEK LONE HT. SOUTH ESAH RANGE BARN HILLS 1.133 2.255 0.769 0 .6 4 3 FIGURE 20 CHAPTER II "ONSHORE-OFFSHORE" CONODONT DISTRIBUTION ACROSS THE LATE ORDOVICIAN WESTERN NORTH AMERICAN CONTINENTAL MARGIN. EASTERN GREAT BASIN, U.S.A. ABSTRACT.— Upper Ordovician carbonates deposited along the passive western North American continental margin in the eastern Great Basin contain a diverse and moderately abundant conodont fauna. Although tectonic upwarping associated with the Tooele Arch in Utah and Nevada affected paleo- and depositional environments across that "passive" margin, an open-marine to epeirlc marine (i.e. Late Ordovician "onshore- offshore") gradient is evident. Temporal ordination of samples collected along two transects across the margin in Utah and Nevada by graphic correlation of conodont species range data provides a high- resolution chronostratigraphic framework for paleoecologic interpretation of Late Ordovician continental margin conodont distribution. More than 20,000 Late Ordoviciari conodont elements recovered from 243 samples from 11 eastern Great Basin localities represent 50 species, which comprise eight morphoguilds (new term). Morphoguilds are groups of species with similar aptative morphologies and problematic niche parameters. Relative abundance, Q-mode cluster and Q-mode principal components analyses suggest the existence of a conodont faunal gradient 80 81 associated with the Late Ordovician western North American continental margin. Temporal fluctuation in faunal composition was probably related to Late Ordovician eustacy. INTRODUCTION Upper Ordovician carbonates assigned to the Ely Springs, Fish Haven, Hanson Creek, and Saturday Mountain formations in the eastern Great Basin accumulated as platform to ramp facies on the "passive" western North American continental margin (see fig. 21). Paleogeographic reconstruction suggests a definite "onshore-offshore" gradient. This gradient extends from the western edge of Late Ordovician epeiric sedimentation, roughly equivalent to the continental hinge or Wasatch Line (Stokes, 1976; Kay, 1951), to carbonate ramp facies juxtaposed on the west against approximately coeval basinal sediments of the Roberts Mountains Allochthon. The gradient represents change from epeiric environments to the east (i.e. "onshore") to open-marine, slope and/or ramp (i.e. "offshore") environments on the west. Minor tectonic modification of the margin by local uplift and subsidence (e.g. the Tooele Arch (cf. Hintze, 1954, 1959, 1974; Armstrong, 1968; Bick, 1966; Webb, 1956)) may have affected environmental parameters associated with the gradient. Late Ordovician conodonts from the eastern Great Basin are both abundant and diverse. More than 20,000 conodont elements from 243 samples at 12 localities represent at least 50 species. Seven Upper 82 Ordovician sections both north and south of the Tooele Arch (see fig. 22) provide two, paleogeographically well-controlled transects across the margin. Graphic correlation of those 3even sections effects temporal ordination of 189 samples and provides a high-resolution chronostratigraphic framework for evaluation of conodont distribution on an "onshore-offshore” gradient (Leatham, chapter I). MORPHOGUILDS Within phylogenetic limits, effective exploitation of ecospace hinges directly on the development of adaptive morphologies. The understanding of niche parameters that govern the spatio-temporal distribution of species is effected by recognition of those adaptive responses, either by functional analyses or by analyses of morphologic/environmental associations. Clearly, all morphologies are not adaptively significant. Potentially adaptive (Gould and Vrba, 1982) morphologies may be common in the fossil record. The synergistic effect of all niche axes effectively constrains those morphologies and prevents expansion of species into unfilled, or potential niche space. However, potentially adaptive morphologies may become adaptive through environmental and/or evolutionary modification. Potentially adaptive morphologies therefore represent potential ecospace utilization, and further exemplify the relationship between environmental exploitation and morphology. 83 Morphologic similarity may be either inherited or the product of convergent evolution (homoplasy) within phylogenetic constraints. Organisms of different phyletic heritage may exploit similar sets of environmental parameters by convergent evolution of adaptive morphologies. Consequently, species that exploit similar environments tend to be morphologically similar. Groups of species that inhabit similar portions of ecospace may effectively be termed guilds (Root, 1967; Bambach, 1981; Van Valkenburgh, 1982, 1985). Guilds are taxonomically independent: they do not necessarily reflect phylogenetic relationships. The definition and taxonomic content of a guild depends on how grossly one wishes to partition ecospace. Guilds may contain all members of several phyla (e.g. lophophorates in marine benthic communities) or be restricted to groups of species belonging to several genera (Root, 1967; Bambach, 1981; Van Valkenburgh, 1982, 1985). Because niche parameters restricting the paleoecologic distribution of many fossil organisms are not well understood, definition of guilds in the traditional sense is not always feasible. However, fossil species with similar, and possibly adaptive, morphologies can be recognized. Such groups, irrespective of phylogeny, are designated "morphoguilds" to distinguish them from the original guild concept. Basically, morphoguilds are groups of species with shared morphologic characters that probably reflect similar ecospace utilization. In analyses of spatio-temporal species distribution, morphoguilds minimize 84 the effects of temporally and geographically restricted species and emphasize inferred ecologic, rather than phylogenetic, constraints. The morphologic boundaries of morphoguilds are entirely dependent on how one wishes to partition hypothetical ecospace. However, groups of morphoguilds that share other, more general morphologies may be informally designated "morphogroups" to establish a heirarchy in the morphologic relationship to ecospace habitation. "Morphogroups” are effectively high-rank morphoguilds. Establishment of a heirarchal system for morphoguilds allows one to estimate the relative magnitude of environmental perturbations that limit the spatio-temporal distribution of species. Variation in the distribution of low-rank morphoguilds is most likely due to relatively minor environmental change, whereas the distribution of "morphogroups” is probably controlled by major enviromental perturbations. Based on elemental morphology and apparatus reconstruction, species of Late Ordovician conodonts can be assigned to eight morphoguilds {see plate I) that transcend taxonomic boundaries. 1) The Platfonn/Ratniform Morphoguild (PLAT) includes species characterized by ramiform apparatuses with platformed or pastiniscaphate P elements (see table 3). Most of these species have hindeodelliform dentition and are common constituents of "cold- water" conodont faunas (Sweet and Bergstrom, 1984). 85 2) The Laterally Compressed Ramiform Morphoguild (LCRAM) includes species with apparatuses composed of laterally compressed ramiform elements and angulate, pastinate, or digyrate P elements (see table 3). Elements lack hindeodelliform dentition. LCRAM species are common faunal constituents of the Ohio Valley Province (Sweet and Bergstrom, 1984). 3) The Peg-like Ramiform Morphoguild (PLRAM) includes species with stout, peg-like denticulation and apparatuses of alate, bipennate, digyrate, and dolabrate ramiform, and in some species pectiniform P elements (see table 3). PLRAM species are most abundant in Red River faunas of the North American craton (Sweet and Bergstrom, 1984). 4) The Palmate Ramiform Morphoguild (PALM) contains only one species, Rhipidognathus symmetricus. R. symmetricus has broad, spatulate denticulation, and the elements of the symmetry transition series are palmate in appearance (see plate I). 5) The Furrowed Co3tate Coniform Morphoguild (FCCON) includes species with adenticulate, nongeniculate coniform elements characterized by a prominent lateral furrow (see plate I and table 3). FCCON species are common in both "cold-" and "warm-water" faunas (Sweet and Bergstrom, 1984). 86 6) The Rastrate Morphoguild (RAST) includes species characterized by rastrate elements. Many of those elements are laterally furrowed (see plate I). Denticulation of the posterior margin and, in some cases, geniculate coniform elements serve to distinguish RAST species from FCCON species. 7) The Smooth Coniform Morphoguild (SMCON) includes species with apparatuses of unornamented coniform elements (see plate I). Although the SMCON species, Drepanoistodus suberectus, has sharp anterior and posterior margins (=costae), lack of sharp lateral costae preclude its assignment to the SCCON. 8) The Sharply Costate Coniform Morphoguild (SCCON) includes species characterized by apparatuses of nongeniculate coniform elements with sharp lateral, anterior, or posterior costae. Elements with sharp lateral costae serve to distinguish SCCON from SMCON species. The eight Late Ordovician conodont morphoguilds collectively represent three high-rank ’’morphogroups". LCRAM, PALM, PLAT, and PLRAM morphoguilds collectively include species with ramiform element apparatuses assigned to the RAMIFORM "morphogroup". SMCON, FCCON, and SCCON species are collectively characterized by coniform apparatuses, and hence comprise a CONIFORM "morphogroup11. RAST species are intermediates between RAMIFORM and CONIFORM morphoguilds and can not be justifiably assigned to either of those two major "morphogroups". 87 RELATIVE ABUNDANCE ANALYSIS Because morphoguilds deemphasize the temporal nature of species and accentuate adaptive or potentially adaptive morphologies, several distinct trends in morphoguild distribution are evident in a time- averaged relative-abundance analysis of the "onshore-offshore" paleoecoline in Utah and Nevada (see fig. 23). Although shifting paleoenvironmental parameters are lithologically and chronostratigraphically evident in the Late Ordovician of the eastern Great Basin (Leatham, chapter 1), the relative position of each locality in Utah and Nevada relative to endpoints of the "onshore-offshore" gradient (i.e. the continental hinge to the east and the platform margin to the west) was probably comparatively stable in the Late Ordovician. Time-averaging the entire Upper Ordovician section deemphasizes temporal fluctuations in morphoguild relative abundance and accentuates paleoenvironmental parameters associated with the gradient. The total number of conodont elements assignable to each Late Ordovician morphoguild i 3 computed for every locality on the two transects that flank the Tooele Arch (see fig. 23). Elements of PALM and PLRAM are most abundant in "onshore" areas. Both morphoguilds are essentially absent from platform margin environments on the southern transect. However, elements of PALM and PLRAM occur in distal platform/upper ramp carbonate sediment gravity deposits of the Ely Springs Dolostone at 85LT in the Toano Range of Nevada (Leatham, chapter I). Those elements are most probably derived 88 from "shallower" platform carbonates to the east, and correspond with a major mid-Richmondian, chronostratigraphically significant, continent- wide inflection of Aphelognathus and Rhipidognathus (Leatham, chapter 1; Sweet, 1979). Although the sampled localities are discrete because of limited exposures in the Basin and Range, the gradational decrease in PALM and PLRAM from "onshore" to "offshore" sections is suggestive of an "onshore-offshore" conodont faunal gradient, SCCON and PLAT are most abundant in samples from "offshore" localities and, except for minor occurrences, are absent in "onshore" sections. The acme of SCCON is at site 83LC, at or near the platform margin (Leatham, chapter I), At that locality, Silurian conodont faunas from the overlying Roberts Mountains Formation are also enriched in SCCON and suggest that parameters that favored SCCON returned following Richmondian-Gamachian environmental perturbations associated with glacioeustatic lowering of sea-level (Berry and Boucot, 1973; Brenchley and Newall, 1980, 1984; Hambrey, 1985; McKerrow, 1979). The relative abundance of SCCON at the type section of the Hanson Creek Formation (PHC) is much lower than that at Lone Mountain (83LC), 32 km to the northwest. PHC includes Late Ordovician carbonates that accumulated near the platform margin (Leatham, chapter I) west of the distal terminus of the Tooele Arch. Based on total faunal similarity, PHC is a faunal intermediate between the platform margin fauna of 83LC and the mid-platform fauna 83LE. Species of PLAT are also absent at PHC. 89 No distinct "onshore-offshore" trends in the relative abundance patterns of the other four morphoguilds (i.e. SMCON, RAST, FCCON, LCRAM) are evident along either the northern or the southern transects (see fig. 23). The distribution of CONIFORM and RAMIFORM "morphogroups" across the margin indicates a strong "onshore-offshore" faunal gradient (see fig. 24). Species with coniform apparatuses are more abundant in "offshore" rather than in "onshore" faunas. Conversely, species with ramiform apparatuses are most abundant in "onshore" faunas. The CONIFORM/RAMIFORM ratio gradually increases "offshore", and does not indicate abrupt change. Aldridge (1976) noted a similar increase in the relative abundance of Silurian coniform elements in "offshore" regions of the Welsh Borderland. Time-averaged Maysvillian and Richmondian conodont faunas of the eastern Great Basin, as indicated by graphic correlation (Leatham, chapter I), differ markedly in relative faunal composition. FCCON, LCRAM, RAST and SMCON tend to dominate Maysvillian faunas. Conversely, PALM and PLRAM are best represented in Richmondian/Gamachian faunas. Analyzed by stage, distribution patterns similar to those described above for the entire Late Ordovician verify the SCCON/PLAT, PALM/PLRAM, and RAMIFORM/CONIFORM gradients across the margin (see figs. 25 and 26). The correspondence of Maysvillian and Richmondian conodont distributions suggests that paleogeographic position relative to the Wasatch Line was a more important control on morphoguild distribution than were temporal fluctuations in paleoenvironment. CLUSTER ANALYSIS Q-mode cluster analysis verifies the relationship between time- averaged morphoguild distribution and the paleogeographically defined "onshore-offshore" gradient (see fig. 27). Using time-averaged morphoguild relative abundance data, euclidean dissimilarity coefficients were computed for sections from both transects across the margin. Clustering of those distance coefficients by unweighted pair group average linkage (UPGC) produces a reasonable facsimile of faunal "distance" between sections. In this analysis, the sequential monotonic fusions produced by unweighted pair group average linkage clustering (Pielou, 1984) reflect not only the faunal dissimilarity of those localities in the eastern Great Basin but also their relative position across the continental margin. The clusters can be divided into three major categories based on faunal dissimilarity but reflective of paleogeographic position. 1) The cluster that includes 83LB, 85LT, and 83LE represents mid- to outer platform/upper ramp localities. Those sections are approximately equidistant from the Wasatch Line or continental hinge (see fig. 21). 2) A primary linkage of 83LA and 83LF represents "onshore" localities north and south of the Tooele Arch. Those sections are close to the 91 Wasatch Line (see fig. 21) but are litho- and chronostratigraphically different (Leatham, chapter I). 3) The disjunct linkage of PHC and 83LC implies strong faunal disimilarity with the other clustered localities. Both PHC and 83LC are near the Late Ordovician platform margin, far from the Wasatch Line (see fig. 21). PRINCIPAL COMPONENTS ANALYSIS The paleoecologic structure of Late Ordovician conodonts in the eastern Great Basin is perhaps best interpreted by uncentered, Q-mode principal components analysis (PCA). The data base includes over 20,000 conodont elements, assigned to the eight principal conodont morphoguilds, from 243 samples collected from all 11 Great Basin localities (see fig. 21). The square root of absolute elemental abundance of each morphoguild for each sample was used for the analysis. The square root transform ensures that sample ordination is not affected by interrelated variables and deemphasizes samples with abundant elements and morphoguilds in the analysis. All samples are included in this analysis, regardless of elemental frequency. Analyses of "culled” data sets that include only those samples with eight or more elements produced similar results and interpretations. Extraction of the eight principal components or eigenvectors from the covariance-variance correlation matrix produced from that transformed data matrix reveals that 43 percent of the total variance is contained in the first principal component (see table 4). 92 Interpretation of the first principal component is not readily apparent from morphoguild loadings (see table 5). However, comparison of total elemental abundance with first principal component scores suggests that 43 percent of the variance in the data set is related to overall abundance (see fig. 28). Morphoguild loadings of the second principal component, which account for 16 percent of the total variance in the data matrix, demonstrate the paleoecologic significance of that axis (see tables 4 and 5). The loadings comprise four distinct groups: 1) high, positive subequal loadings of PLRAM and PALM; 2) low, positive subequal loadings of FCCON, SMCON, and RAST; 3) a low negative loading of LCRAM; and 3) high, negative subequal loadings of PLAT and SCCON (see table 5). As indicated by the loadings, samples are ordinated along the second principal component between two end members: species of PLRAM and PALM, and species of PLAT and SCCON. The loadings effectively mimic the "onshore-offshore11 distribution of time-averaged morphoguild relative abundance and suggest that the second principal component represents an "onshore-offshore" conodont faunal gradient across the platform. Each of the four groups of morphoguild loadings that contribute to the variance of the second principal component are paleobiogeographically distinct. As constituents of the Red River Conodont Bioprovince, defined by Sweet and Bergstrom (1984), PLRAM and PALM are very common in the cratonic interior of Late Ordovician North America. In order to attach paleobiogeographic significance to the 93 collective distribution of those species, both morphoguilds are herein designated the CRATONIC Faunal Association. FCCON, SMCON, and RAST species characteristically comprise 40-70 percent of the Red River fauna (Sweet, 1979; Leatham, 1984, 1985). Although FCCON, SMCON, and RAST occur in other bioprovinces (e.g. the Ohio Valley Conodont Bioprovince, Sweet and Bergstrom, 1984), they tend to dominate typical Red River faunas and are herein designated the RED RIVER Faunal Association. LCRAM is an abundant constituent of the North American Midcontinent (Barnes, Rexroad, and Miller, 1973; Sweet, 1979a, 1979b; Sweet and Bergstrom, 1984), and is herein designated the MIDCONTINENT Faunal Association. PLAT and SCCON tend to be amphicratonically distributed, and as such are designated the OFFSHORE Faunal Association. Comparison of the relative abundance of each faunal association with computed second principal component scores for every sample further substantiates the ’’onshore-offshore1' distribution of morphoguilds suggested by the relative abundance analysis (see fig. 29). Samples enriched in the CRATONIC Faunal Association correlate with high second principal component scores. Samples with low second principal component scores are enriched in the OFFSHORE Faunal Association. Although samples dominated by the MIDCONTINENT and RED RIVER faunal associations correlate with medial second principal component scores, MIDCONTINENT dominated samples have slightly lower scores than those samples with higher proportions of the RED RIVER Faunal Association. 94 DISCUSSIOH Although morphoguild loadings suggest four, comparatively discrete, faunal associations, their relative proportions can not be easily clustered (see fig. 30). Except for sigmoidal end effects, ranked second principal component scores also increase monotonically (see fig. 31). The curve substantiates the lack of clusters of relative faunal proportions. The lack of discrete clusters of either second principal component scores or relative proportions of faunal associations is indeed suggestive of a spatio-temporal gradient in faunal composition, controlled by gradational environmental conditions. Consequently, it is impractical to establish discrete conodont biofacies for the Late Ordovician of the eastern Great Basin based on relative faunal composition. The second principal component appears to be a good measure of "onshore-offshore" faunal change and associated environmental conditions. The temporal variation of those scores at localities both north and south of the Tooele Arch (see figs. 32 and 33) suggest fluctuation of environmental parameters that controlled morphoguild distribution across the continental margin. The curves are similar to the temporal fluctuation of morphoguild relative abundance (see figs. 34 and 35). Overall, second principal component scores are comparatively low for "offshore" and high for "onshore" localities. 95 At each locality, temporal fluctuation of the second principal component represents relative environmental perturbations in "onshore- offshore" conditions. Temporal fluctuation of second principal component scores is probably related to relative changes in depth and depth-related parameters such as temperature, salinity, oxygenation, or food resources and therefore serves as an indicator of relative sea- level. The general chronostratigraphic distribution of morphoguilds substantiates prior interpretations of bathymetric constraints on Late Ordovician conodont associations (Kohut and Sweet, 1968; Seddon and Sweet, 1971; Sweet, 1979a, 1979b; Sweet and Bergstrom, 1966, 1984; Barnes and Fahr eus, 1975; Barnes, LeFevre and Tixier, 1977; Barnes, Rexroad and Miller, 1973; Sweet, Turco, Warner and Wilkie, 1959; McCracken and Barnes, 1981; McCracken and Lenz, 1987; Nowlan and Barnes, 1981). In this study, interpretation of relative depth is based entirely on relative position along a verifiable "onshore-offshore" gradient and is not constrained by depositional interpretations of disjunct sections. The peak size of second principal component curves varies with "onshore-offshore" position (see figs. 32 and 33). Peaks are higher in "onshore" sections than in sections near the platform margin. That relationship reflects the relative paleoenvironmental stability across the margin. The curves suggest that fluctuations in depth and depth- related paleoenvironmental parameters had a pronounced effect on 96 conodont faunas of "onshore" areas, whereas "offshore" areas were less affected by those paleoenvironmental perturbations. Correlation of second principal component curves suggests essentially isochronous environmental control on "onshore-offshore" morphoguild distribution (figs. 32 and 33). Major inflections can be traced across the margin and do not appear to be significantly controlled by environmental perturbations related to local tectonics and sedimentation (Leatham, chapter II). Peaks of high second principal component scores can also be chronostratigraphically related to continent-wide incursions of "shallow-water" conodont genera (Sweet, 1979a, 1979b). The widespread, subisochronous fluctuation of "onshore-offshore" second principal component scores is suggestive of Late Ordovician glacioeustasy and associated variation in temperature (Berry and Boucot, 1973; Brenchley and Newall, 1980, 1984; Hambrey, 1985; McKerrow, 1979* Sheehan, 1987). Variation in glacially controlled sea-level affects the intersection of the thermocline with the continental margin. The importance of temperature as a proximal control on conodont distribution has been recognized by many authors (Sweet, 1985; Sweet and BergstrSm, 1974, 1984; Sweet, Turco, Warner and Wilkie, 1959* Bergstrom and Carnes, 1976; Geitgey and Carr, 1987; Nicoll, 1976) and low paleolatitude, Late Ordovician "cold-water" conodont faunas, which are commonly enriched in PLAT and SCCON, may have been separated from "warm-water" midcontinent faunas by the thermocline. The lack of substantial provincial overlap 97 between amphicratonically distributed, low-latitude Late Ordovician "cold-water" and "warm-water" conodont faunas (Sweet and Bergstrom, 1984) may indicate the relative strength and position of the thermocline in the Late Ordovician. Different, yet perhaps related processes may also produce correlative, subisochronous inflections in temporal plots of second principal component scores. A major, mid-Richmondian (1220-1230 meters in the CSS), "onshore" inflection is evident at all localities of the northern transect (see fig. 32). Abundant PLRAM and PALM specimens characterize that inflection (fig. 34). Lithologic interpretation of mid-Richmondian platform localities 83LA and 83LB suggests that those faunas are essentially autochthonous and accumulated in comparatively shallow depositional environments. However, sediment gravity deposits of the upper carbonate ramp at 85LT yield similar, allochthonous, isochronous conodont faunas (Leatham, chapter I), which were presumably derived from "onshore" localities to the east. CONCLUSIONS 1) Morphoguilds are herein established as groups of morphologically similar species and poorly understood niche parameters. Morphoguilds function as ecologic units and are taxonomically independent. Use of morphoguilds effectively eliminates taxonomic bias and emphasizes environmental exploitation in paleoecologic analyses. 98 2) Late Ordovician conodont species represent eight low-rank conodont morphoguilds and three ''morphogroups1' whose distribution across the Late Ordovician western North American margin is suggestive of differential "onshore-offshore" environmental exploitation. 3) Relative abundance, Q-mode cluster and Q-mode principal component analyses suggest that a conodont morphoguild faunal gradient existed across the Late Ordovician western North American continental margin. The faunal gradient corresponds with a definite "onshore-offshore" gradient. 4) Principal components analysis is an extremely useful tool for the paleoecologic interpretation of Late Ordovician conodonts along a physically verifiable "onshore-offshore" gradient. Although the largest percentage of the variance in the data set is attributable to total elemental frequency, relative "onshore-offshore" position is a dominant control on conodont distribution across the margin. Chronostratigraphic evaluation of second principal component scores suggests that temporal fluctuations across the margin were essentially isochronous. The fluctuations probably represent the response of conodont populations to eustatic change. Thus, temporal plots of second principal component scores may be used as high-resolution relative sea level curves. 99 5) The analyses substantiate previous general bathymetric interpretations of Late Ordovician conodonts and emphasize the gradational nature of faunas along an "onshore-offshore" gradient. REFEREHCES Aldridge, R.J. 1976. Comparisons of macrofossil communities and conodont distribution in the British Silurian. Geological Association of Canada Special Paper 15:91-104. Armstrong, R.L. 1968. The Cordilleran Miogeosyncline in Nevada and Utah. Utah Geological and Mineralogical Survey Bulletin, 78:1-58. Bambach, R.K. 1983. Ecospace utilization and guilds in marine communities through the Phanerozoic, in, MJS Tevesz and PL McCall (eds.), Biotic Interactions of Fossil and Recent Communities. Plenum Press Corporation, U.S.A., pp. 719-745. Barnes, C.R., and L.E. Fahraeus. 1975. Provinces, communities, and their proposed nektobenthic habit of Ordovician conodontophorids. Lethaia, 8:133-150. Barnes, C.R., C.B. Rexroad, and J.F. Miller. 1973. Lower Paleozoic conodont provincialism. Geological Society of America Special Paper 141:156-190. Bergstrom, S.M. 1971. Correlation of the North Atlantic Middle and Upper Ordovician of Europe and eastern North America, in W.C. Sweet and S.M. Bergstrom (eds.), Symposium on Conodont Biostratigraphy. Geological Society of America Memoir 127:83-157. Bergstrom, S.M., and J.B. Carnes. 1976. Conodont biostratigraphy and paleoecology of the Holston Formation (Middle Ordovician) and associated strata in eastern Tennessee., in^ C.R. Barnes (ed.), Conodont Paleoecology. Geological Association of Canada Special Paper 15:27-57. Bergstrom, S.M., and W.C. Sweet. 1966. Conodonts from the Lexington Limestone (Middle Ordovician) of Kentucky and and its lateral equivalents in Ohio and Indiana. Bulletins of American Paleontology, 50(229):271-424. Berry, W.B.N., and A.J. Boucot. 1973* Glacio-eustatic control of Late Ordovician-Early Silurian platform sedimentation and faunal changes. Geological Society of America Bulletin, 84:275-284. 100 Bick, K.F. 1966. Geology of the Deep Creek Mountains, Tooele and Juab Counties, Utah. Utah Geological and Mineralogical Survey Bulletin, 7 :1-120. Brenchley, P.J., and G. Newall. 1980. A facies analysis of Upper Ordovician regressive sequences in the Oslo region, Norway-A record of glacio-eustatic changes. Palaeogeography, Palaeocliraatology, Palaeoecology, 31:1-38. Brenchley, P.J., and G. Newall. 1984. Late Ordovician environmental changes and their effect on faunas, i£ D.L. Bruton (ed,), Aspects of the Ordovician System: Paleontological Contributions from the University of Oslo. Universitetsforlaget, Oslo, Norway, 295:65-79. Geitgey, J.E., and T.R. Carr. 1987. Temperature as a factor affecting conodont diversity and distribution, in R.L. Austin (ed.), Conodonts: Investigative Techniques and Applications. Ellis Horwood Limited, British Micropaleontological Society, Chichester, pp. 241-255. Gould, S.J., and E.S. Vrba. 1982. Exaption— A missing term in the science of form. Paleobiology, 8(1):4-15. Hambrey, M.J. 1985. The Late Ordovician-Early Silurian glacial period. Palaeogeography, Palaeoclimatology, Palaeoecology, 51:273-289. Hintze, L.F. 1954. Mid-Ordovician erosion in Utah. Geological Society of America Bulletin, 65:1343* Hintze, L.F. 1959. Ordovician regional relationships in north-central Utah and adjacent areas. Intermountain Association of Petroleum Geologists Guidebook 10:46-53. Hintze, L.F. 1974. Geologic History of Utah. Brigham Young Geology Studies, 20(3):1-181. Kay, G.M. 1951. North American geosynclines. Geological Society of America Memoir, 48:1-143. Kohut, J.J., and W.C. Sweet. 1968. The American Upper Ordovician Standard; X, Upper Maysville and Richmond conodonts from the Cincinnati Region of Ohio, Indiana, and Kentucky. Journal of Paleontology, 42:1456-1477. Le Fevre, J., C.R. Barnes, and M. Tixier. 1976. Paleoecology of Late Ordovician and Early Silurian conodontophorids, Hudson Bay Basin, irj C.R. Barnes (ed.), Conodont Paleoecology. Geological Association of Canada Special Paper 15:69-89. Leatham, W.B. 1984. Conodont biostratigraphy of the Fish Haven and Laketown dolomites of Northern Utah [abst.]. Geological Society of America Abstracts with Programs, 17(75:641. 101 Leatham, W.B. 1985. Ages of the Fish Haven and lowermost Laketown dolomites in the Bear River Range, Utah. Utah Geological Association Guidebook, 14:29-38. McCracken, A.D., and C.R. Barnes. 1981. Conodont biostratigraphy and paleoecology of the Ellis Bay Formation, Anticosti Island, Quebec, with special reference to Late Ordovician-Early Silurian chronostratigraphy and the systematic [sic] boundary. Geological Survey of Canada Bulletin, 329:51-134. McCracken, A.D., and A.C. Lenz. 1987. Middle and Late Ordovician conodont faunas and biostratigraphy of graptolitic strata of the Road River Group, northern Yukon Territory. Canadian Journal of Earth Science, 24:643-653. McKerrow, W.S. 1979. Ordovician and Silurian changes' in sea level. Journal of the Geological Society of London, 136:137-145. Morris, H.T., T.S. Lovering, and H.D. Goode. 1961. Stratigraphy of the East Tintic Mountains Utah with a section on Quaternary deposits. United States Geological Survey Professional Paper 361:1-145. Nicoll, R.S. 1976. The effect of Late Carboniferous-Early Permian glaciation on the distribution of conodonts in Australia, in C.R. Barnes (ed.), Conodont Paleoecology. Geological Association of Canada Special Paper 15:273-278. Nowlan G.S., and C.R. Barnes. 1981. Late Ordovician conodonts from the Vaureal Formation, Anticosti Island, Quebec. Geological Survey of Canada Bulletin, 329:1-49. Picha, F., and R.I. Gibson. 1985. Cordilleran hingeline: Late Precambrian rifted margin of the North American craton and its impact on the depositional and structural history, Utah and Nevada. Geology, 13:465-468. Pielou, E.C. 1984. The Interpretation of Ecological Data: A Primer on Classification and Ordination. John Wiley and Sons, New York, 263 pp. Root, R.B. 1967. The niche exploitation pattern of the Blue-Gray Gnatcatcher. Ecological Monograph, 37C4):317-350. Seddon, G., and W.C. Sweet. 1971. An ecologic model for conodonts. Journal of Paleontology, 45:869-880. Sheehan, P.M. 1987. The Foliomena community— Life below the thermocline in the Late Ordovician [abst.]. Geological Society of America Abstracts with Programs, 19(4):245. 102 Stewart, J.H., and F.G. Poole. 1974. Lower Paleozoic and uppermost Precambrian Cordilleran miogeocline, Great Basin, western United States, in W.H. Dickinson (ed.), Tectonics and Sedimentation. Society of Economic Paleontologists and Mineralogists Special Publication 22:28-57. Stokes, W.L. 1976. What is the Wasatch Line?, i^n J.G. Hill (ed.) Geology of the Cordilleran Hingeline. Rocky Mountain Association of Geologists, pp. 11-26. Sweet, W.C. 1979a. Late Ordovician conodonts and biostratigraphy of the western Midcontinent Province. Brigham Young University Geology Studies, 26(3):45-85. Sweet, W.C. 1979b. Conodonts and conodont biostratigraphy of the post-Tyrone Ordovician rocks of the Cincinnati Region. United States Geological Survey Professional Paper 1066-G:1-25. Sweet, W.C. 1985. Conodonts: Those fascinating little whatzits. Journal of Paleontology, 59(3):485-494. Sweet, W.C., and S.M. Bergstrom. 1974. Provincialism exhibited by Ordovician conodont faunas. Society of Economic Paleontologists and Mineralogists Special Publication 21:189-202. Sweet, W.C., and S.M. Bergstrdm. 1984. Conodont provinces and biofacies of the Late Ordovician. Geological Society of America Special Paper 196:69-87. Sweet, W.C., C.A. Turco, E. Warner Jr., and L.C. Wilkie. 1959. The American Upper Ordovician Standard. I. Eden conodonts from the Cincinnati region of Ohio and Kentucky. Journal of Paleontology, 33(6):1029-1068. Van Valkenburgh, B. 1982. Evolutionary dynamics of terrestrial, large, predator guilds. Third North American Paleontololgical Convention Proceedings, 2:557-562. Van Valkenburgh, B. 1985. Locomotor diversity within past and present guilds of large predatory mammals. Paleobiology, 11(4):406-428. Webb, G.W. 1956. Middle Ordovician stratigraphy in eastern Nevada and western Utah. American Association of Petroleum Geologists Bulletin, . 42(10):2335-2377. FIGURE 21.— Localities of stratigraphically well-controlled conodont collections and generalized paleogeographic reconstruction of Late Ordovician western North America. The Wasatch Line or continental hinge (Kay, 1951; Stewart and Poole, 1974; Stokes, 1976; Picha and Gibson, 1985) separates epeiric sedimentation to the east from the western North American continental margin. Position of the paleoequator after Smith, Hurley and Briden (1981). All localities are identified in Table 2. 103 10i( Pacific MER 85LT DV * 82LE LATH ORDQViCIAN PALEOEQUATOR FIGURE 21 FIGURE 22.— Sampled localities on two "onshore-offshore" transects across the Late Ordovician continental margin in Utah and Nevada. The northern transect, on the northern flanks of the Tooele Arch, includes sites 83LA, 83LB and 85LT. The southern transect, south of the Tooele Arch, includes sites 83LF» 83LE and 83LC and PHC. The generalized platform margin separates Upper Ordovician platform carbonates from carbonates deposited by sediment gravity processes. 105 106 \ I 8 5 LT 8 3 LB • #8 3 LA TOOELE ARCH NE VA D A JT — *5— • — / PHC/> /• 8 3 LC UTAH I 8 3 LF \ I • \ I 8 3 LE X\ | ' * N. PLATFORM'MARGIN / \ / x_ 100 MILES FIGURE 22 TABLE 2.— Locality register of stratigraphically well-controlled conodont collections used in thi3 study. 107 108 TABLE 2 LOCALITY HLIJISnJi SECTION LCCA31CT LCXTLT-S Lc;cm^£ TCWi5Hi?/gacs S3LA Lakeside Mtur.cains, Utah 40°51’14’ 112a4 5 ’4O’ Celle, Utah 7.5' Quad, to to SWfc Sec. 33, T 2 tJ. R 3 40*51’30’ 112°i5'44’ W; a WA: S«c. 4, T i M, R 8 W. 8ILB Silver IsLard Mxntairs, Utah 3S®5B’35’ 113®50’23’ Geahan Peak, Utah 7.5’ to to Quad, NE3: unsurveyed jg^a'sa* 113°50’39’ Sec. 25, t 3 N, R 18 W. 831C Lcne Hanutin. Nevada 3Sa2S’A2’ 116" S ’29* Eartire Ranch, Nevada to 15’ Quad, V« of 116a16’47’ unsurveyed Sec. 19, T 20 N, R 51 E. B2IH South Egan Range, Nevada 35°23’13’ 114°53’C0’ cave Valley Veil, Nevada to 7.5’ Quad, SEt NEt Sec. H 4 C53’15’ 14 to SSs Wife Sec. 13. T 7 N. R 62 E. 821T Ba m Hills, Utah aa’ss’o-' 113°Z3’3r The B a m , Utah 15’ Quad, to to ISA: end NEx of Sec. 14, i5J;9,n ’ ■ H 3 a2 2 ,49" X 21 S. R 14 W. 8517 Xoano Range, Nevada 41°02’C5* H 4 ° 1 5 ,13* Cobra SE, Nevada 7.5’ to to Quad, NSx unsurveyed 4L®02’15' 114°15’23" Sec. 2 6 NVx unsurveyed Sec. 3, T 36 N, R 63 S. fi: Pete Hinson Creek, Nevada 2S“ 5 2 ’ 115° 1 9 ’ Roberts Creek Mountain, [Anita Harris (U30S) unpublished (approx.) (apprcx.) Nevada 15’ Quad, type collections] section, hsad of Pete Hanson Creek, T 23 N, R 50 S. HSR Mountain Bay Range, Nevada 35® 2S’ 116° 0 4 ’ Locality of Ross, NaLan [Anita Harris (C3G5) calln.] and Harris (1979). CCI Custer County, Idaho 44®19’10' U 4 ° 1 3 ’53" Locality of Hays, [Anita Harris (U3GS) colin.] to to Harris, Dutro and Ross ii'IS’lB’ H 4 ° 1 3 ’17’ (1530). w Death Valley area, California 35® 24* 116® 36’ Ryan Quadrangle, Calif. [Anita Harris (U53S) unpublished to to 1 5 ’ Quad, Secs. 10, 12, collections] 26® 2 5 ’ 116° 38’ T 26 N, R 3 E 5 Sec. 33, T 26 H, R 4 E. PLATE I.— Morphology of selected conodont elements assigned to the eight Late Ordovician morphoguilds described in the text. 109 PLATE I LATERALLY COMPRESSED RAMIFORH FURROWED COSTATE CONIFORM 8HARPLY COSTATE CONIFORM TABLE 3.— Taxonomic composition of the eight Late Ordovician morphoguilds. 111 TABLE 3 SPECIES COMPOSITION OF LATE ORDOVICIAN MORPHOGUILDS IN THE EASTERN GREAT BASIN RAMIFORM MORPHOGROUP CONIFORM MORPHOGROUP PLATFORM/RAMIFORM (PLAT) MORPHOGUILD SHARPLY COSTATE CONIFORM (SCCON) MORPHOGUILD siphclatyuithus? sj). o f Sweet (I979t>) Cncloccradcmtus trimiuus JithinctDn stiito/jiliOH'wilms otdovicieui (IJrmison & Mclil) J'mtopamkrodus spp, Gamaetiiffiailuu cnsifcr McCracken, Nowlnn & Bnrncs Stmiffcrcliu spp. Icrioilclla 5pp. Walliscrodtts amplissinuts (Scrpagli) PEG-LIKE RAMIFORM (PLRAM) MORPHOGUILD SMOOTH CONIFORM (SMCON) MORPHOGUILD siplMlotfialluts sjip. Dreptinalslailits subcrcctus (Brunson & Melil) Ouloiim ulrichi (Stone St. Furnish) *Oistotlus’ vaiusltts Stauffer Psatdooiicolothis spp. LATERALLY COMPRESSED RAMIFORM (LCRAM) MORPHOGUILD FURROWED COSTATE CONIFORM (FCCON) MORPHOGUILD Pltrarmotlus umlauts Branson St. Mctil Pkclodina aadcalaides Sweet Dnpsilodiis imitatus (Branson & M chl) Pkctodina florida Sweet Panderodus spp. Plcctodiiia lam is (Branson & Mclil) Sctibbardetla aliipes (Hcnningsmocn) Pfislo);iwlhus bighomaisls Stone it Furnish Pristogiatluis? ruhnert (l£tlii»£ton Sc. Furnish) PALMATE RAMIFORM (PALM) MORPHOGUILD RASTRATE MORPHOGROUP ftlripidayinthits qmmctricus Branson, M clil i t Branson nASTRATE (RAST) MORPHOGUILD Hetadina spp. Culiiuibadiu/i spp. N.|jen.n.sp. A of Leatliam (19IM) Pambelodiun dattictdaltt Sweet Pscudobclodbui spp. Pkua^riadius spp. 112 FIGURE 23.— Time-averaged relative abundance of the eight morphoguilds for the northern and southern transects. Locality notation same as Table 2. 113 m sw -iaep in ajp rd m<=*-**Hs>Er'i=:xi=r> FIGURE 23 FSOE ONSHORE OFFSHORE— 5T 3B 83LA B3LB B5LT N s 1 V>^l V ^ TRANSECT NORTH - m I m . m PNC FSOE OHSHORE OFFSHORE— 3C 3E 83LF B3LE B3LC TRANSECT SOUTH i M lb k m s s I 21 PLAT 0 0SCCON H M X 1 0 |§FCC0N j HAST | l§]puftAH SMCON ^ S SECTIOH ENTIRE paui FIGURE 2*1.— Time-averaged relative abundance of CONIFORM, RAMIFORM, and RASTRATE "morphogroups" for the northern and southern transects. Locality notation same as Table 2. 115 wcwHZPirsam'-o n cw -o ir'cicn 109/. FIGURE 24 49/ 49/ - 20/ 20/ - 00 6 9 / - / 9 6 By. /- FSOE ONSHORE OFFSHORE— 5T 3B 83LA 03LB 85LT TRANSECT NORTH PHC FSOE ONSHORE OFFSHORE— 3C 3E 83 83LE 63LC TRANSECT SOUTH coni/om o / i n o c Q £*) rastrate p~^j SECTION ENTIRE panif panif or« FIGURE 25.— Time-averaged Maysvillian relative abundance of the eight morphoguilds for the northern and southern transects. Locality notation same as Table 2. 117 FIGURE 25 P3«»i-i3Mr3am*a m<=*-"-i=>c'c=xc=r> FSOE ONSHORE OFFSHORE— 5 T 3B 83LA 83LB B5LT TRANSECT NDRTH ■ ■ m H 0 C 3E 03LF B3LE 03 LC PHC is FSOE ONSHORE OFFSHORE— taatstssi 20*0 TRANSECT SOUTH PC* m 553 I 1 H i VILLIAN gj gj SCCON JOflM ^ MAYS- FCCON H [2 [2 PLAT SMCON H H gjPALH MSI B plram CX) FIGURE 26.— Time-averaged Richmondian relative abundance of the eight morphoguilds for the northern and southern transects. Locality notation same as Table 2. 119 mnax-tztsioaratj FIGURE 26 FSOE ONSHORE OFFSHORE— 5 T 3B 03LA 83LB B5LT TRANSECT NORTH 1 i H BL BL 83U B3LE B3LC PHC FSOE ONSHORE OFFSHORE— TRANSECT SOUTH I «*ssa I HONDIAH RICH- S N O C 0SC LCRAN 2 f FCCON ^ T S A R 0 N O C K ||S H g]PAI* plat plraw G2L FIGURE 27-— Q-mode unweighted pair group average linkage cluster analysis of euclidian dissimilarity coefficients computed from time- averaged morphoguild relative abundance for the northern and southern transects. Locality notation same as Table 2. 121 03LC PHC 83LF 83LA 83LE DISSIMILARITY COEFFICIENTS CALCULATED FROM RELATIVE ABUNDANCE B5LT DATA 83LB EUCLIDEAN DISTANCE-UNWEIGHTED PAIR GROUP i I ~ T ~ i .2 A .6 .8 FIGURE 27 122 TABLE 4.— Eigenvectors (principal components), eigenvalues and associated variance of an uncentered, Q-mode principal components analysis on square-root transformed conodont elemental frequency, Only the first two principal components, which account for about 6056 of the total variance, are readily interpretable. 123 TABLE 4 PRINCIPAL COMPONENTS ANALYSIS SQUARE ROOT TRANSFORM, ALL SAMPLES EIGENVALUE VARIANCE CUMULATIVE VARIANCE EISV1 3.41331 4 3 ’/. 4 3 / EIGV2 1.30839 16/ 5 9 / EIGV3 1.07493 13/ 7 2 / EIGV4 B.83179 10/ 8 3 / EIGV5 0.55165 0 7 / 9 0 / EIGY6 0 .4 5 0 0 4 0 6 / 9 5 / EIGV7 0 .2 3 4 3 0 0 3 / 9 8 / E16VS 0.13558 0 2 / 1 0 0 / TABLE 5.— Q-mode principal component loadings for the first three principal components. 125 TABLE 5 PRINCIPAL COMPONENT LOADINGS FIRST THROUGH THIRD EIGENVECTORS SCUARE ROOT TRAHSFORMj ALL SAMPLES PRIN I PRJH 2 PRIH' 3 PLATFORM 8.B35799 -0.264970 0 .8 7 1 5 6 3 RAMIFORM SHARPLV 0.310668 -B.2G087S - 0 .8 0 4 1 9 6 COSTfiTE CONIFORM LATERALLV 0 .3 7 6 4 0 1 - 0 .1 3 0 6 5 9 0 .2 3 9 4 2 2 COMPRESSED RAMIFORM FURROWED 0.50 01 1 3 0 .0 0 3 7 7 1 - B . 0 4 3 8 9 3 COSTATE CONIFORM SMOOTH 0 .4 0 8 2 1 5 0 .8 1 5 3 9 8 0 .9 2 9 4 1 6 CONIFORM RASTRATE 0 .4 6 0 3 4 0 B.B45I88 -0.219935 PEG-LIKE 8 .2 3 6 4 7 0 0 .6 3 4 7 7 6 0 .0 5 1 5 5 5 RAMIFORM PALMATE - 0 .0 6 5 8 2 1 0.662846 0.359466 RAMIFORM FIGURE 28.— Sympathetic variation of computed first principal component scores and total number of conodont elements per sample. Similar relationships are evident in samples from the other six localities used in this analysis. Line = total elements per sample. Bars = computed first principal component scores. Sample numbers = feet above top of Eureka Quartzite. 127 nnsi fRuicipju, couponcnt sc o n e s FIRST PRINCIPAL COUPO/ iEk T SCORES First principal couponent sc o r es a M I a c r o t n f o l.'iu 00 1.W) ! £2?1 W' O Ksa }?cd <6n U n> - ■5 '« X h fn no iu U» & u u i3Nint)3HJ TUtttnTH Aarjino'jui Tvjinnjn Ajianoiwj -wifnnRJ r i n s r p r i n c i p a l c o u p o n e m s c o r e s FIRST PRINCIPAL COUPONDir SCORES MUST PRINCIPAL COMPONENT SCONES wow*I • m ZlTJZZfZZ&Z/TZl. ' 1 * v s :z s £lY.\ Lr£t7tSSJ77j?.t£ZZSJY& I YStrfiZLLUA— Y.ZSt/..'?S?JflZ>XJZ21 pTa1 \rr7f,rJ'r*fZ.r?*i XL'srss?. vr rrr* r ,u y h I\3rZJ.V'SZ£7J7ZI7 vx.v.5£a---- - h th u o S I*2172 Z; D O fT1*1 °M S7C \’\ l'V.1 Z_Gf o flu A j o h 3003u j *Vfmirm:j A3K3nDJilJ 7VJinflTI3 ADinnoiuj 'tfiriinna ro CD FIGURE 29.— Relationship between faunal associations and computed second principal component scores. 129 1 w i/i .4 .4 I Po 0 ll a ifl SECOND PRINCIPAL COMPONENT SCORES SECOND PRINCIPAL COMPONENT SCORES 1 .a < .a i.j A PROPORTION0 Rio RIVER FAUKiAi. ASSOCIATION PROPORTION CRATQNIC FAUNAL A SSO C IA T IO N - s o a io SECOND PRINCIPAL COMPONENT SCORES SECOND PRINCIPAL COMPONENT SCORES u> FIGURE 29 o FIGURE 30.— Faunal association relative abundance in samples with more than five elements. The sorted data set suggests gradational spatio- temporal faunal composition and lacks discrete clusters of samples with similar faunal proportions. 131 10B 7. \ \ \ r CRATQNIC □ RED RIVER v -j.v P I HID- t&J CONTINENT COHT OFFSHORE c 40y. SAMPLES WITH MORE THAN FIVE ELENEHTS FIGURE 30 132 FIGURE 31.— Cumulative frequency plot of second principal component scores for the 243 samples used in the analysis. Except for sigmoidal ends, the lack of major inflections suggests gradational, not discrete, spatio-temporal faunal composition. 133 FIGURE 31 SECOND PRINCIPAL COMPONENT SCORES 10 0 5 UUAIE FREQUENCY CUMULATIVE APE (n=243) 3 4 2 = n ( SAMPLES FIGURE 32.— Spatio-temporal fluctuation of second principal component scores for the northern transect. Temporal ordination of samples by graphic correlation (Leatham, chapter I). Curves for G3LB and 85LT are discontinuous because of mid-Maysvillian to early Richmondian unconformities and late Richmondian covered section. 135 Q 8 3 C MOUNTAINS MOUNTAINS MOUNTAINS SILVER ISLAND LAKESIDE S —5 ~i ~i r— o ! ! Huinowuyn nuiqnohhoih nuitiiasauh a s s FIGURE 33.— Spatio-temporal fluctuation of second principal component scores for the southern transect. Temporal ordination of samples by graphic correlation (Leatham, chapter I). 137 CO OJ (A m o H (A 0 C H 1 3 2 PI 3 2 3 3 q 4 TJ PI ni PI nni 3 m 2 * 5 In1 r » r3 °r§ 2 to 2 0 GAMACHIAU 1250 1275 RICHMONDIAN 1225 1200 1175 HAY9VILLMN 1150 o-- CO 01 V to A r ■n A r b) n w n V TJ I Q-* (A 3 Q I a 0 ■n I (A 1 0 3 FIGURE 33 FIGURE 3^.— Spatio-temporal morphoguild relative abundance for the northern transect. Temporal ordination of samples by graphic correlation (Leatham, chapter I). 139 : Zr Q* fr> OS 10 z a cog wz 0»/» rn a x S**1 n *^23) ° v=o r0Z Cmo bjszpi a ocwS2 uzrr MX v 2 GflMACHIRN 1275 AtS rOB A jt W&JJ 0 0 c PI 3 PI 0 1250 RICHMONDIAN 1225 m a o i w z o n ju o iw in o 1200 1175 HftVSVILLIflN 1150 i h b h m m VJUHBHI ''IHHHNI VMaitatae* \ HHHW 3 D Z 8 H 2 n a cn cn n > 3 2 H 30 0 H z tt rn FIGURE 34 FIGURE 35.— Spatio-temporal morphoguild relative abundance for the southern transect. Temporal ordination of samples by graphic correlation (Leatham, chapter I). l l i S GAMACHIAN | GAMACHIAN ■ mtt mmm ata« ata« *, i t*, m i W i m m m i mim m :. I :. M M i V B M I tMMNMUMIiaiHHI Ti in w —Ti am RICHMONDIAN HIM W J t S i S M V '.JMkkMIt V ^961200776 ^ MAVSVILLIAH m m (0 C H % pi Z WI n -I Z H 50 0 7) pi FIGURE 35 CHAPTER III .— INTERPRETATION OF THE SILURIAN DIANA LIMESTONE. TOQUIHA RANGE. CENTRAL NEVADA. AMD ITS PALEOGEOGRAPHIC IMPLICATIONS: EVIDENCE FROM MIXED COMODONT FAUNAS. CARBONATE PETROLOGY. AND STRATIGRAPHIC RELATIONSHIPS ABSTRACT.— The Diana Limestone, exposed in the Mill Canyon Sequence of the Ikes Canyon Window in the Toquima Range, Nevada, contains a biostratigraphically mixed conodont fauna. The fauna includes Whiterockian through Late Llandoverian-Early Wenlockian species that characterize cold water, offshore niches. Diana lithofacies represent a series of sediment gravity deposits chararacteristic of slope or distally steepened ramp environments. Stratigraphic concepts of the Diana Limestone and the "unnamed limestones" of McKee (1976) and Ross (1970) are equated. Emplacement of Diana carbonates is most probably related to an Early Silurian flexure of the western North American continental margin, not to deposition on the eastern flank of the postulated Toiyabe Ridge. INTRODUCTION Lower and Middle Paleozoic paleogeographic reconstructions of the Cordilleran continental margin of central Nevada hinge significantly on interpretation of rocks exposed in windows of the Roberts Mountains 143 Thrust in the Toquima Range (Kay, 1960; Kay and Crawford, 1964; Stewart and Poole, 1974; McKee, 1976; Matti and McKee, 1977; Johnson and Murphy, 1984). The Ikes Canyon Window (fig. 36) includes excellent exposures of Ordovician through Devonian carbonate facie3 deposited in outer shelf to slope/basinal environments. Those carbonates are transitional with platform carbonate facies to the east (eastern assemblage) but contrast markedly with allochthonous outer slope to basinal siliceous facies (western assemblage) of the Vinini Formation on the upper plate of the Roberts Mountains Thrust. Kay and Crawford (1964) mapped, named, and described three stratigraphic sequences separated by thrusts within the window: the June Canyon, Mill Canyon, and August Canyon sequences (see fig. 36). Each sequence embraces Ordovician through Devonian strata. The allochthonous sequences were tectonically imbricated during the Antler Orogeny (Kay, 1960; Kay and Crawford, 1964; McKee, 1976; Matti and McKee, 1977). The Diana Limestone, diagnosed and described by Kay and Crawford (1964), occurs only in the Mill Canyon Sequence, in which it is sandwiched between the Antelope Valley Limestone and the overlying Roberts Mountains Formation (= Masket Shale of Kay and Crawford) (see fig. 37). In this study, the lithostratigraphic concept of Diana is equated with that of the "unnamed limestone" of McKee (1976). Although the age of the Diana can easily be bracketed by the underlying Whiterockian Antelope Valley Limestone and the overlying Middle Silurian to Lower Devonian Roberts Mountains Formation, its exact chronostratigraphic position has been uncertain. Although the sequence appears conformable, evidence suggests that a prominent paraconformity separates the Diana from the underlying Antelope Valley Limestone (Harris and others, 1979; McKee, 1976; Kay and Crawford, 1964; Matti and McKee, 1977; Berry and Boucot, 1970; Ross, 1970; Ross and others, 1980). The magnitude of the hiatus varies with the correlation. Chronostratigraphic assignment of the Diana vacillates between Silurian (Kay and Crawford, 1964; Matti and McKee, 1977; J.T. Dutro Jr. (written communication reported in McKee, 1976)) and late Middle to Late Ordovician (Berry and Boucot, 1970; Ross, 1970; McKee, 1976; Harris and others, 1979). The Diana Limestone/Roberts Mountains formational contact also appears conformable, but its chronstratigraphic interpretation relies heavily on the correlation of the Diana. The concepts discussed in this report stem from study of the Diana Limestone and its entombed conodont fauna in the Ikes Canyon area. New conodont evidence verifies Kay and Crawford’s (1964) original Silurian correlation and suggests that the Diana probably includes Vfhiterockian through Early Silurian carbonate slope deposits that were emplaced no later than the Late Llandovery or Early Wenlock. Petrologic and stratigraphic evidence preclude interpretation of the Antelope Valley/Diana Limestone contact as the product of subaerial exposure. Deposition appears to be related to Silurian downdropping of the continental margin In central Nevada (Johnson and Potter, 1975; Hurst, Sheehan, and Pandolfi, 1985; Hurst and Sheehan, 1985). The data present an alternative explanation for Ordovician-Silurian continental margin 146 hiatuses in central Nevada (Murphy and others, 1979), which have been used as evidence for the presence of a Toiyabe Ridge, a linear topographic high rimming the edge of the continental margin in central Nevada (Kay, 1960; Kay and Crawford, 1964; Stewart and Poole, 1974; McKee, 1976; Matti and McKee, 1977; Berry, 1977; Johnson and Murphy, 1984). LITH0STRAT1GRAPHY; A NAME FOR THE "UNNAMED" As part of his regional study of the northern Toquima Range, McKee (1976) referred all limestones sandwiched between the Antelope Valley Limestone and the Roberts Mountains Formation to an unnamed formation. Although McKee (1976) admitted that it is locally difficult to distinguish the "unnamed limestone" from the subjacent Antelope Valley, he designated a thin, lenticular, phosphatic grainstone as a "key marker" between the two formations and suggested that Kay and Crawford's (1964) Diana i3 a discontinuous facies of the "unnamed limestone". All stratigraphic studies of the Antelope Valley/Roberts Mountains succession in the Mill Canyon Sequence (Kay and Crawford, 1964; Lowell, 1958; McKee, 1976) attest to the lateral variation of limestones separating those formations. In their original diagnosis of the Diana, Kay and Crawford (1964) documented the lateral variation from massive calcarenite to well-bedded limestone in several sections (see fig. 38) and stated that both lithologies characterize the formation. The lithologic variability of limestones separating the Antelope Valley/Roberts Mountains is highly pronounced in the Ikes Canyon area (see fig. 38). Three distinct lithofacies are apparent along the outcrop belt mapped by McKee (1976): 1) the Carbonate Rudstone/Breccia Facies; 2) the Bedded Limestone Facies; and 3) the Massive, Laminated and/or Bioturbated Facies. Quartz silt and minor phosphate grains are disseminated throughout. 1) Carbonate Rudstone/Breccia Facies: Boulders of limestone dominate, with maximium diameters approaching 60 cm. The boulders range in shape from angular prolate to rounded subequant (see fig. 39a). The silty, pink- to yellow-gray matrix contains detrital carbonates and quartz, and abraded dolomite rhombs. The rudstone is typically polymictic, containing wacke- to bioclastic pack- and grainstone boulders and cobbles commonly enriched in pelmatozoan and brachiopod debri3. Clasts of carbonate rudstones are also present (see fig. 39b), Breccias included in this facies are typically monomictic, with a high degree of fitting (Richter and Fiichtbauer, 1981; Fiichtbauer and Richter, 1983), and may grade both laterally and vertically into either rudstones or the Bedded Limestone Facies. ' 2) Bedded Limestone Facies: Thin- to medium-bedded wacke- to grainstones commonly intercalated with yellowish, clay-rich micrite are the most common lithologies encountered along the outcrop belt, despite the fact that they are intergradational with the Carbonate 148 Rudstone/Breccia Facies (see fig. 40a). The Bedded Limestone Facies is typically the lowermost facies of the Diana (see fig. 40b). Pronounced lithologic similarity between this facies and the subjacent Antelope Valley Limestone makes it difficult to separate the two at several localities. Individual beds vary in thickness and can not be traced over large distances. Intraformational truncation surfaces, described by Davies (1977), are common features of the bedded lithofacies (see fig. 41a). Stratabound, syndepositional folds (see fig. 41b and 42a) are also associated with this lithofacies. Many beds exhibit Bouma sequences and tool marks, and grooves typically characterize bed bases. 3) Massive, Laminated and/or Bioturbated Facies: This facies is partially synonomous with Kay and Crawford’s (1964) calcarenitic facies, although lithologies range from pack- to micstones. Laminations are generally not evident on outcrop, but can be faintly distinguished on polished slabs (see fig. 42b). These laminations appear to be planar. The facies is also somewhat mottled in places and generally lacks macrofossils, although Kay and Crawford (1964) report an occurrence of Favosite3 sp. in lithologies of this type on the ridge crest south of June Canyon. The Diana mapped by Kay and Crawford (1964) separates all exposures of the Antelope Valley from the Roberts Mountains Formation south of 149 June Canyon and on Copper Mountain. Kay and Crawford did not identify the Diana in the outcrop belt of the Mill Canyon Sequence between Ikes Canyon and June Canyon (see fig. 36). McKee's "unnamed limestone" includes not only the Diana, but also lithologies ascribed by Kay and Crawford (1964) to the top of the Antelope Valley between Ikes and June canyons. On the north slope of April Canyon, beds ascribed to the uppermost Antelope Valley by Kay and Crawford (1964), but included in the "unnamed limestone" by McKee (1976), are "... a breccia of siliceous calcitite with blocks up to 2 feet in length in a silty matrix..." (Kay and Crawford, 1964, pg. 432). Those beds are indicative of the Carbonate Rudstone/Breccia Facies. Although outcrops of the Diana on Kay and Crawford's (1964) map are incorrectly labeled as the Silurian Gatecliff Formation (McKee, 1976), inspection of the legend confirms that the correct symbol for the Diana is depicted. McKee's (1976) insinuation that those map errors have obscured both the stratigraphic position and location of Kay and Crawford's (1964) Diana appears unfounded. The Gatecliff, known only in the August Canyon Sequence, is correctly labeled and depicted on Kay and Crawford's (1964) map. Furthermore, excluding the absence of mapped Diana between Ikes and June canyons on the 1964 map, the outcrop patterns for the formation on both McKee's (1976) and Kay and Crawford's (1964) maps are very similar. Because lithostratigraphic concepts of Kay and Crawford's (1964) Diana Limestone are not easily separable from Ross' (1970) and McKee's 150 (1976) concepts of the "unnamed limestone", priority suggests that the "unnamed" actually has a name: the Diana Limestone. Where the lithologic break between the Antelope Valley and Diana is not easily recognized because the phosphatic grainstone marking the top of the Antelope Valley is not ubiquitously distributed (McKee, 1976), syndepositional structures (e.g. stratabound folds and intraformational truncation surfaces) can be used to distinguish the Diana from the Antelope Valley. The platy limestones of the overlying Roberts Mountains Formation are easily distinguished from Diana lithologies. CONODONT FAUNA Conodonts have been previously reported from the Diana Limestone (McKee, 1976; Harris and others, 1979). All reported faunas were collected from Copper Mt. Samples collected from a measured section on the south wall of Ikes Canyon produced conodont faunas comparable with those from Copper Mt, (Harris and others, 1979; McKee, 1976). Stratigraphic admixtures of Whiterockian through Early Silurian species occur throughout (see fig. 43a and table 10). Silurian species have not been previously documented. Most samples are dominated by elements of Ordovician species, although the relative abundance of Silurian forms increases in fine-grained carbonate turbidites and laminated limestones (see fig. 43b). Conodont elements are also most numerous in samples that contain abundant Silurian forms. 151 Color alteration indices of Diana conodont specimens range from about 3 to 4. Some of the smaller* more fragile specimens are remarkably well preserved. Such excellent preservation of a biostratigraphically mixed fauna, as well as the lack of abraded conodont fragments, may indicate that the conodonts were transported in clasts, rather than as isolated specimens. Several of the larger platformed elements have hematitic basal fillings. Microfossils associated with the conodont elements include, among others, mazuelloids, hexactinellid sponge spicules, phosphatlzed bivalves, phosphatic spheroidal problematica (see Ethington, 1981), and agglutinated foraminifera. PALEOBIOGEOGRAPHIC AMP PALEOECOLOGIC AFFINITY The mixed conodont association is dominated by Ordovician species typical of "cold water" faunas (Sweet and Bergstrom, 1984), and notably lacks coeval "warm-water" species common in eastern Great Basin platform carbonates. Elements of Pleotodina, Phragmodus, Aphelognathus, Belodina, Pseudobelodina, Culumbodina, Rhipidognathus, and Erismodus, common in Mohawkian and Cincinnatian "warm-water" cratonal conodont faunas (Bergstrom and Carnes, 1976; Sweet and Bergstrom, 1984), and late Whiterockian Leptochirognathus do not occur in any samples of the Diana Limestone. Possible representatives of the "warm-water" fauna in the Diana Limestone include specimens assigned to Meomultioistodus, Oulodus sp., and Panderodus sp. Elements of Heomultioistodu3 are typical "fibrous" forms, characteristic of shallow, cratonic environments. Oulodus is not known from Ordovician "cold-water" faunas but was common in Mohawkian through Cinncinnatian cratonic settings of North America. Although Panderodus is present in the cold-water conodont realm (Sweet and Bergstrom, 1984), elements of the species comprise over 40 percent of the Cincinnatian conodont fauna of the Red River Province (Sweet, 1979; Sweet and Bergstrom, 1984; Leatham, 1984). Panderodus is extremely abundant in the Upper Ordovician of the eastern Great Basin (Leatham, chapter 2). However, only one specimen of Panderodus is present in all studied samples of the Diana (see plate ii.6). Oulodus and Panderodus are known from Middle and Upper Ordovician, and Silurian strata. Although Early Silurian conodonts appear to have been fairly cosmopolitan following breakdown of provincial boundaries associated with the latest Ordovician extinction, data suggest that Oulodus and Panderodus retained essentially the same provincial distribution in the Silurian (Leatham, unpublished data). Several species substantiate ties with the Ordovician cold-water conodont realm (Sweet and BergstrSm, 1984). Nordiodu3 italicus Serpagli (plate ii.135 is characteristic of the polar-subpolar, Mediterranean Province (Sweet and Bergstrom, 1984), and samples from Copper Mt. (A. Harris, unpublished collections) yield the only documented extra- European specimens. 153 Specimens of Nolxodontus (see plate ii.17-22) were first reported from the Ordovician Grafenthaler Schichten of Germany and subsequently documented in the Cape, Noix, and Keel limestones of Missouri (McCracken and Barnes, 1982; Knupfer, 1967; Satterfield, 1971; Amsden and Barrick, 1986). Collections from the subsurface of Libya (Bergstrom and Massa, 1979, in press), northwestern France (Paris and others, 1982), and Spain (Carls, 1975) include specimens assignable to Hoixodontus. Bergstrom (in Sweet and Bergstrom, 1984; Bergstrom and Massa, in press) assigns those Meditteranean elements to Sagittodontina. Regardless of the generic designation, the elements belong to the same phylogenetic lineage. Their dominance in faunas of the subpolar, Ashgillian, Mediterranean Province further substantiates biogeographic ties between the Diana conodont faunas and the Ordovician cold-water conodont realm. Ordovician conodonts identified from the Diana Limestone that occur in both "warm-water" and "cold-water” conodont faunas, although more abundant in facies containing ”cold-water” species, include: Amorphognathus spp. (Sweet and Bergstrom, 1984; Bergstrom, 1971; Sweet and others, 1971), Dapsilodus spp. (Sweet and Bergstrom, 1984), Eoplacognathus spp., Gamachignathu3 spp. (includes Blrksfeldia of Orchard, 1981), Icriodella spp., Periodon spp., Protopanderodus spp., Pygodus spp., and Walliserodus spp. Excluding specimens assigned to Silurian species, for which provincial distribution is poorly understood, overall relative abundance of the aforementioned conodonts in Diana samples strengthens the Diana "cold-water" faunal connection. 154 Conodonts from debris flows of the Late Ordovician Grog Brook Group of northwestern New Brunswick, Canada (Nowlan, 1983), show distributional patterns similar to those in the Diana Limestone. Although representatives of warm-water faunas are present in both collections, species characteristic of cold-water faunas dominate both. Nowlan (1983) suggested that the mixed biogeographic affinities of Grog Brook conodont faunas were produced by downslope transport of warm-water species, which then were mixed in deeper water with the indigenous cold- water fauna. Faunas of mixed affinity also occur in the Ordovician Woods Hollow and Maravillas formations of western Texas (Bergstrom, 1978), which are interpreted as a series of slope deposits. Such mixed faunas consistently occur in offshore, slope facies. Conodont and benthic macrofaunal distribution encircling the Uhiterockian North American plate are strikingly similar (Bergstrom, 1979). Ross and Ingham (1970) assigned those macrofaunal elements to the Toqulma-Table Head Realm. The macrofauna of the Antelope Valley Limestone in Ikes Canyon is remarkably unlike faunas of coeval deposits to the east (Ross,1970), a distributional pattern reminiscent of the conodont faunas from Ordovician-Silurian deposits. Bergstrom (1979) noted the similarity of high-paleolatitude Baltoscandic Whiterockian conodonts to those from the low-paleolatitude Antelope Valley Limestone (an important constituent of Diana faunas) of the Toquima Range and suggested that faunal distribution was most likely 155 controlled by factors that vary with, but are not restricted by, latitude such as water temperature. Biogeographic affinities of post- Whiterockian conodonts from the Diana support that conclusion and suggest that provenance of the Diana mixed-conodont association was limited to faunas that characteristically inhabited "colder water", although "warm water" cratonal species are abundant to the east on the westernmost Late Ordovician carbonate platform (e.g. Lone Mt., Leatham chapter 2). Such cold-water faunas are amphicratonically distributed, parallel to the North American platform or shelf margin and typically occur in offshore depositional environments (Sweet and Bergstrom, 1984; Bergstrom and Carnes, 1976; Barnes and others, 1976). The near absence of Ordovician warm-water conodont species in the upper Antelope Valley and Diana limestones suggests that depositional environments varied little from offshore, cold-water niches inhabited by cold-water conodont faunas. CORRELATION OF THE DIANA— MACROFAUNA In the original diagnosis of the formation, Kay and Crawford (1964) interpreted the Diana as Silurian, presumably based on correlation of the "massive" disconformity at the base with regional stratigraphic reconstruction, and on collections of two tabulate corals, Halysites and Favosites, from the formation. McKee (1976), Berry and Boucot (1970), and Ross (1970) question that age assignment on the basis of graptolite, trilobite, and anthozoan data and consider the Diana to be Ordovician. Brachiopods collected near Diana Peak, identified by J. T. Dutro, Jr. 156 (1970), and reported by McKee (1976) may be either Late Ordovician or Early Silurian. COHODOMT BIOSTRATIGRAPHY Conodont faunas of the Diana can be divided into three major biostratigraphic categories (see table 6): 1) Species common to the underlying Antelope Valley Limestone in the Ikes Canyon Sequence (Harris and others, 1979); 2) Ordovician species younger than those from the Antelope Valley that represent strata not present in the Ikes Canyon Sequence; 3) Species of Silurian affinity. Whiterockian conodonts from the uppermost Antelope Valley limestone were well documented by Harris and others (1979)» who also noted their occurrence throughout the Diana. Representatives of Ordovician conodont faunas 6 through 13 (Sweet and others, 1971; McCracken and Barnes, 1981) occur in the mixed association, suggesting that Upper Whiterockian through Gamachian strata were probably present near the depositional site of the Diana Limestone in the Ike3 Canyon sequence (see table 6). The known ranges of Ordovician speci'es identified in the mixed association also suggest quasicontinuous carbonate accumulation of those Ordovician strata. Although specimens that represent conodont species of Whiterockian through Wenlockian age occur as stratigraphic admixtures throughout the Diana, the Silurian species, previously unrecognized in Diana collections, establish a much younger age for the formation than previously suggested by conodont studies (Ross, 1970; McKee, 1976; Harris and others, 1979). Collections from both sides of Ikes Canyon yield specimens of Ozarkodina hassi (see plate IV.3, 6, 7, 10, 13, 16, 18, 21). 0. hassi is no younger than mid- to late Aeronian, and is common in Llandoverian faunas below the Distomodus staurognathoides appearance datum of Cooper (1980). Several specimens of hadra have been recovered from Diana samples from the north-facing wall of Ikes Canyon and characterize the Pterospathodus celloni and P. amorphognathoides zones, which span the Llandoverian-Wenlockian boundary (i.e. Telychian-Sheinwoodian stages). Specimens of long-ranging (i.e. Telychian-early Devonian) Ozarkodina excavata are abundantly represented in the uppermost, massive, laminated carbonates exposed on the north- facing wall. Doubly-tipped coniform elements of Pseudooneotodus bicornis, also present in the Massive, Laminated and/or Bioturbated Lithofacies, occur only in strata no older than Telychian and reiterate biostratigraphic ties between the Diana and late Llandoverian-early Wenlockian conodont faunas. Pb elements assignable to either Ptero3pathodus celloni or £. amorphognathoides recovered from the Diana further substantiate the late Llandoverian-early Wenlockian correlation. Mannik's (1983) illustration of a Pb element that he placed in an unnamed species of Ozarkodina (i.e. his sp. A) from the late Llandoverian-early Wenlockian of Svernaya Zemlya (northernmost central USSR) is virtually identical to a Pb element obtained from the south wall of Xke3 Canyon. A Pa element with a denticulate bifurcate lateral process (see plate IV. 12, 13) is most probably assignable to Pterospathodus and is similar to, but not identical to, Aeronian posteritenuls. Pterospathodus is restricted to Llandoverian and early Wenlockian strata. As much as 20 percent of the Silurian conodont elements in several Ike3 Canyon samples represent Papsllodu3 obliquicostatus, which is elsewhere common in Llandoverian offshore environments (Aldridge and Jeppsson, 1984). Similar late Llandoverian- early Wenlockian conodont faunas occur in the overlying platy limestones of the Roberts Mountains Formation. Conodont evidence suggests that the Diana is no younger than late Llandoverian/early Wenlockian, and suggests quasicontinuous deposition of slope carbonates from the Whiterockian through late Llandoverian- early Wenlockian. GENESIS OF THE DIANA AND ITS PALEOGEOGRAPHIC SIGNIFICANCE Synergistically, the described evidence favors subaqueous, slope derivation and emplacement of Diana carbonates. Sediment gravity flows appear to have been the most common emplacement process, although slumps and slides, indicated by 3tratabound folds and intraformational truncation surfaces, were commonplace. Carbonate rudstones, monomictic carbonate breccias with a high degree of "fitting", and large, bedded 159 limestone clasts are common lithic characteristics of sediment gravity deposits (Cook and Taylor, 1977; Cook and Mullins, 1983; Richter and Fuchtbauer, 1981; Fuchtbauer and Richter, 1983; Cook, 1983). Furthermore, accompanying stratabound folds, intraformational truncation surfaces, Bouma sequences, scours and both vertical and lateral discontinuity of Diana lithofacies suggest subaqeuous downslope transport of carbonate material. Although conodont data suggest that no major biostratigraphic hiatuses were present near the depositional site of the Diana, abrupt appearance of the mixed Whiterockian through Late Llandoverian/Early Wenlockian conodont fauna at the base of the Diana, associated with sediment gravity deposits and other synsedimentary features characteristic of subaqueous downslope transport, implies development of unstable slope conditions no later than Late Llandoverian/Early Wenlockian. There is little or no evidence to support subaerial exposure at the Diana/Antelope Valley contact. The uppermost Antelope Valley is lithologically similar to the Bedded Limestone Facies of the Diana. Many thin- to medium-bedded limestones are graded, contain flame structures and exhibit partial Bouma sequences (see figs. 44a, 44b). Neither lithofacies nor sedimentary structures below or above the contact suggest shallow-water deposition or subaerial exposure. It might be argued that Late Llandoverian/Early Wenlockian subaerial exposure removed such evidence, although neither Diana lithologies nor 160 platy, graptolite-bearing limestones of the overlying Roberts Mountains are suggestive of obligatory transgression required by such a model. Slope depositional environments, represented by rocks of the Mill Canyon Sequence, were pervasive from the Ordovician through the Silurian (see fig. 45). Murphy and others (1979) document existence of a Late Llandoverian/Early Wenlockian hiatus at several localities to the north and east of the Toquima Range. That hiatus is correlated with regional foundering of the Early Silurian continental margin (Johnson and Potter, 1975; Hurst and Sheehan, 1985; Hurst, Sheehan and Pandolfi, 1985), which resulted in widespread deposition of deeper-water facies of the Roberts Mountains Formation. Internal breccias, associated with flexure of carbonate-shelf margins (Richter and Fuchtbauer, 1981; Fuchtbauer and Richter, 1983)* have been described from Lone Mountain, Nevada (Sheehan, 1986), approximately 60 km northeast of Ikes Canyon. Lone Mountain represents the westernmost extent of Ordovician carbonate platform development in central Nevada. The breccias occur in Llandoverian strata that have been previously assigned to the top of the Hanson Creek Formation (Dunham, 1977). However, the bed3 are lithologically most similar to the extensively silicifled lowermost Roberts Mountains Formation and appear to represent part of that depositional episode. 161 Flexure of the shelf margin not only fractures and brecciates carbonates at the hinge, but effects general slope instability. Such instability generates extensive downslope transport and deformation of carbonate material. Debris flows are common downslope from internal breccias, which serve as the source of carbonate debris (Fuchtbauer and Richter, 1983; Fuchtbauer, Richter and Wachter, 1984). The Carbonate Rudstone/Breccia Facies and deformation associated with emplacement (e.g. intraformational truncation surfaces and stratabound folds) of Diana carbonates are not common features of either the underlying Antelope Valley Limestone or the overlying Roberts Mountains Formation in the Mill Canyon Sequence. The Diana carbonates and associated deformation appear to be related to some general change in slope stability in the early to middle Silurian (see fig. 45). Conodonts from the brecciated beds at Lone Mountain (Leatham, unpublished data) include specimens of Icriodina irregularis, Oulodus? kentuckyen3is, Carniodus carnulus, Walliserodus curvatus, Ozarkodina protexcavata, Ozarkodina pirata, Icriodella sp., Pseudooneotodus beckmanni, Decoriconus sp., Dapsilodus obliquicostatus, Oulodus sp.cf. 0. detorta, Ozarkodina? fluegeli, and Panderodus spp. The underlying beds contain a meager fauna of Panderodus spp. and Walliserodus sp., and are probably latest Ordovician (Gamachian) (Leatham, chapter I). Those data imply chronologic equivalence of slope instability, marginal flexure, and emplacement of Diana carbonates. 162 All previous correlations suggest that a substantial portion of the Ordovician-Silurian rock record is missing in central Nevada (Kay and Crawford, 1964; McKee, 1976,; Matti and McKee, 1977; Johnson and Murphy, 1984; Berry, 1977). Palinspastic reconstruction of the June, Mill, and August Canyon sequences suggests that the magnitude of the hiatus increases towards the west (Matti and McKee, 1977; Kay and Crawford, 1964; Johnson and Murphy, 1984). Kay (1960), Kay and Crawford (1964), and subsequent workers (McKee, 1976; Matti and McKee, 1977; Stewart and Poole, 1974; Johnson and Murphy, 1984) have used those correlations and reconstructions as the basis for recognizing a Toiyabe Ridge, postulated to have been a north-trending, linear topographic high that rimmed the outer continental margin in central Nevada, However, lack of evidence for subaerial exposure and onlapping sequences in the Mill Canyon Sequence precludes derivation of Ordovician-Silurian hiatuses by sea- level changes on the eastern flank of a postulated Toiyabe Ridge. The unconformity in the Mill Canyon Sequence was probably produced by slope processes (e.g. slumping and sliding, sediment transport, homogenization, and deposition by gravity flows) attributable to regional, massive slope failure in the Early Silurian. This interpretation probably applies to other Ordovician-Silurian/Devonian unconformities recognized west of the shelf-break in central Nevada. Following flexure of the continental margin in central Nevada, carbonate platform facies ea3t of the shelfbreak prograded westward over basinal to slope facies of the Roberts Mountains Formation (see fig. 45)(Johnson and others, 1978; Murphy and Johnson, 1984; Hurst and 163 Sheehan, 1985; Hurst, Sheehan and Pandolfi, 1985). Deposition of the Roberts Mountains platy limestones terminated in the Lochkovian (McKee, Merriam and Berry, 1972) with the overlying McMonnigal Limestone. The McMonnigal Limestone is lithologically similar to, and correlable with, the shelfal Lone Mountain Dolomite. The McMonnigal-Roberts Mountains contact is gradational. Isolated olistoliths of McMonnigal lithology (i.e. brachiopod-coral rich grainstones and packstones) become more abundant near the top of the Roberts Mountains Formation and indicate encroachment of the Silurian prograding carbonate platform. CONCLUSIONS 1) The Diana Limestone of Kay and Crawford (1964) is a synonym of the "unnamed" limestone of McKee (1976) and Ross (1970). 2) Lithofacies, syndepositional structures and stratigraphic relationships suggest that Diana carbonates represent the emplacement of slope carbonates. 3) Conodont biostratigraphy suggests that the Diana Limestone is no younger than Late Landoverian-Early Wenlockian. 4) Conodonts representing all major Whlterockian-Early Wenlockian faunas are present in Diana collections and suggest quasicontinous deposition near the depositional site of the Diana. 164 5) Diana conodonts are typical of "colder water", more offshore faunas. 6) Emplacement of Diana carbonates is probably associated with Llandoverian flexure of the continental margin (downdropping) near the shelf-break in central Nevada. 7) Subaqueous interpretation of Diana depositional history suggests similar derivation of other Ordovician-Silurian/Devonian unconformities and lithologies west of the shelf-break in central Nevada. 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Conodonts of the Middle Ordovician Table Head Formation, western Newfoundland. Fossils and Strata, 16:1-145. Sweet, W.C. 1979. Late Ordovician conodonts and biostratigraphy of the western Midcontinent Province. Brigham Young University Geology Studies, 26(3):45-85. Sweet, W.C., and S.M. Bergstrom. 1984. Conodont provinces and biofacies of the Late Ordovician. Geological Society of America Special Paper, 196:69-87. Sweet, W.C., R.L. Ethington, and C.R. Barnes. 1971. North American Middle and Upper Ordovician conodont faunas, in W.C. Sweet, and S.M. Bergstrom (eds.), Conodont biostratigraphy. Geological Society of America Memoir 127:163-193. Uyeno, T.T., and C.R. Barnes. 1983. Conodonts of the Jupiter and Chicotte Formations (Lower Silurian), Anticosti Island, Quebec. Geological Survey of Canada Bulletin, 355:1-49. Walliser, O.H. 1964. Conodonten des Silurs. Abhandlungen des Hessischen Landesamtes fur Bodenforschung, Band 41:1-106, Plate II.— Scanning electron photomicrographs of representative Whiterockian and lower middle Ordovician conodont elements. Although representatives of illustrated conodont specimens occur throughout the Diana Limestone, figured specimens of Histiodella and Gen. et sp. indet. are from the uppermost beds of the Antelope Valley Limestone. Specimens are coated with gold-palladium and are reposited in the Orton Geological Museum at The Ohio State University. (1-3) Pteracontiodus cryptodens; 1) inner lateral view of Sc element, sample LD-135, 130X, OSU 41228; 2) posterior view of acontiodlform element, sample LD-150W, 130X, OSU 41229; 3) lateral view of scandodiform element, sample LD-135, 150X, OSU 41230. (4) Bryantodina? 3p., lateral view of Pa element, sample LD- 120C, 280X, OSU 41231. (5) Polyplacognathus ramosus, oblique upper view of broken Pa element, sample LD-105, 60X, OSU 41232. (6-7) Histiodella sp., posterior views of Sa elements, sample LD-095 (top of Antelope Valley Limestone}, 220X and 320X respectively, OSU 41233 and 41234. (8) Histiodella n.sp. 2 of Harris, Bergstrom, Ethington, and Ross, lateral view of P element, sample LD-095 {top of Antelope Valley Limestone}, 140X, OSU 41235. (9) Neomultioistodus clypeus, posterior view of acontiodiform element, sample LD-135, 150X, OSU 41236. (10) Drepanoi3todus angulensis, lateral view of homocurvatiform element, sample LD-135, 200X, OSU 41237. (11-13) Ansella jemtlandica; 11) lateral view of anselliform element, sample LD-135, 240X, OSU 41238; 12) inner lateral view of acodlform element, sample LD-135, 220X, OSU 41239; 13) lateral view of oistodiform element, sample LD-CMt, 300X, OSU 41240. (14) Genus et species indet., inner lateral view of oistodiform element, sample LD-090, 300X, OSU 41241. (15) Oistodus sp. cf. 0. tablepointensis, lateral view of prioniodiform element, sample LD-155, 190X, OSU 41242. (.16) Coleodus? sp. of Barnes and Poplaw3ki (1972), lateral view, sample LD-135, 150X, OSU 41243. (17) Pygodus anserinus, upper view of pygodiform element, sample LD-150C, 140X, OSU 41235. 172 173 PLATE II Plate III.— Scanning electron photomicrographs of representative Middle and Late Ordovician conodont elements of the Diana Limestone. Specimens are coated with gold-palladium. Hypotypes with OSU numbers (OSU #////##) are reposited in the Orton Geological Museum at The Ohio State University. Hypotypes with USNM numbers (USNM are reposited at the United State National Museum and are from Anita Harris* USGS collections. (1-4) Amorphognathus sp.; 1) oblique upper view of ambalodiform element, sample LD-105, 180X, OSU 41236; 2) upper view of amorphognathiform element, sample LD-105, 100X, OSU 41237; 3) posterior view of hibbardelliform element, sample LD-105, 200X, OSU 41238; 4) lateral view of eoligonodiniform element, sample LD-105, 300X, OSU 41239. (5) Amorphognathus ordovicicu3, lateral view of holodontiform element, sample LD-12QC, 200X, OSU 41240. (6) Panderodus sp., outer lateral view of arcuatiform element, sample LD-150W, 200X, OSU 41241. (7-9) Periodon grandis; 7) lateral view of Sc element, sample LD-155, 130X, OSU 41242; 8) lateral view of M element, sample LD-150C, 100X, OSU 41243; 9) lateral view of Pb element, sample LD-CMt, 200X, OSU 41244. (10) Pravognathus sp., lateral view, sample LD-CMt, 240X, OSU 41245. (11) DapsilodU3 mutatus, lateral view, sample LD-120C, 170X, OSU 41246. (12) Protopanderodus insculptus, lateral view, sample LD-105* 120X, OSU 41247. (13) Nordiodlus italicus, lateral view, sample from Harris collection (5-13-78K), 25 ft above base on Copper Mt., 260X, USNM 419124. (14) "Oistodus1* venustus, lateral view, sample LD-150C, 200X, OSU 41248. (15) Pseudooneotodus sp. aff. £. mitratu3, upper view, sample LD-135, 200X, OSU 41249. (16) Indet. Sc element, LD-120C, 160X, OSU 41250 (17-22) Noixodontus girardeauen3ls; 17) lateral view of Pb element, sample USGS 8369-CO, 41 ft above base on Copper Mt., 170X, USNM 419125; 18) lateral view of Pa element, sample LD-120C, 240X, OSU 41251; 19) lateral view of Pa element, sample USGS 8369-CO, 41 ft above base on Copper Mt., 170X, USNM 419126; 20) inner lateral view of Sc element, sample USGS 8369-CO, 41 ft above base on Copper Mt., 170X, USNM 419127; 21) posterior view of Sa element, sample LD-150W, 240X, OSU 41252; 22) oblique posterior view of Sa element, sample LD-150C, 220X, OSU 41253. 174 175 PLATE III Plate IV.— Scanning electron photomicrographs of representative Silurian conodont specimens from the Diana Limestone. All specimens are coated with gold-palladium. Hypotypes with OSU numbers (OSU #####) are reposited in the Orton Geological Museum at The Ohio State University. Hypotypes with USNM numbers (USNM I H H H H H t ) are reposited at the United State National Museum and are from Anita Harris1 USGS collections. (1) Pseudooneotodus bicornis, upper view, sample 83LD-160, 300X, OSU 41254. (2) Ozarkodina hadra, lateral view of broken Pa element, sample 83LD- 155, 150X, OSU 41255. (3,6,7,10,13,16,18,21) Ozarkodina hassi; 3,6,21) lateral view of Pa elements from Harris collection (5-13-78P), sample from Copper Mt., 130X, USNM 419128, 419129, 419130, respectively; 7) lateral view of Pb element, sample 83LD-CMt, 200X, OSU 41256; 10) lateral view of Pa element, sample 83LD-150C, 140X, OSU 41257i 13) lateral view of M element from Harris collection (5-13-78P), sample from Copper Mt., 140X, USNM 419131; 16) lateral view of M element, sample 83LD-CMt, OSU 41258; 18) lateral view of Sc element, sample 83LD-150C, 200X, OSU 41259. (4) Ozarkodina sp. A of Mannik (1983), lateral view of Pb element, sample 83LD-150W, 200X, OSU 41259. (5,9) Pterospathodus 3p.; 5) lateral view of Pb element, sample 83LD-155, 140X, OSU 41260; 9) lateral view of broken Pb element, sample 83LD-135, 240X, OSU 41261. (8,11,14,17,19) Ozarkodina excavata, all specimens from sample 83LD-160; 8) lateral view of Pa element, 110X, OSU 41262; 11) lateral view of M element, 130X, OSU 41263; 14) posterior view of Sa element, 130X OSU 41264; 17) posterior view of Sb element, 120X, OSU 41265; 19) inner lateral view of Sc element, 130X OSU 41266. (12,15) Pterospathodus sp. cf. £. posteritenuis, upper and lateral views of Pa element from sample 83LD-CMt, 200X, OSU 41267. (20) Pap3ilodus obliquicostatus, lateral view, 83LD-155, 220X, OSU 41268. 176 PLATE IV FIGURE 36.— Outcrop belt of the Diana Limestone in the Ikes Canyon Window, Toquima Range, Nevada. The outcrops of the Diana are represented by the stippled pattern, and only occur In the Hill Canyon Sequence. A.C.S. = August Canyon Sequence, M.C.S. = Mill Canyon Sequence, J.C.S. = June Canyon Sequence. Major thrusts separating the three sequences are depicted with large "sawteeth" to distinguish them from minor thrusts that occur within sequences. Map is modified from Kay and Crawford (1964) and McKee (1976). 178 Nevada n ^ I K E S . CANYON APRIL CANYON ROBERTS J MOUNTAINS CANYON THRUST^ ^ JUNE CANYON "• WOLF CANYON »>/( JULY CANYON AUGUST CANYON km MILL CANYON FIGURE 36 FIGURE 37 •— Schematic stratigraphic section of the Diana on the south wall of Ikes Canyon. Similar facies patterns are present throughout the outcrop area, although the stratigraphic sequence may vary. Sedimentary structures (i.e. synsedimentary folds) are vertically exaggerated. Phosphatic grainstones that characterize the base of the Diana at several localities are not present on the south wall of Ikes Canyon, but the base coincides with the abrupt appearance of the biostratigraphically mixed conodont fauna, disappearance of minor chert in the upper Antelope Valley, and occurrence of syndepositional deformation structures. Conodont samples from this locality are indicated by dots to the right of the column which correspond to samples 83LD-090 through 83LD-165 listed in Table 10. 180 ORDOVIC. SILURIAN WHITEROCK. LLANDOVERIAN/WENLOCKIAN ANTELOPE DIANA LIMESTONE ROBERTS VALLEY LS. MTS. FM. FIGURE 38.— Schematic representation of Kay and Crawford’s (1964) original concept of the Diana in the Mill Canyon Sequence. Except for inclusion of their "calcitite breccias" in the upper Antelope Valley, the random patterns of their massive calcarenite and well-bedded, somewhat "mottled" limestones indicate the inherent lateral variability in the original diagnosis. Facies thickness at each locality is approximate and is derived from the diagnosis (Kay and Crawford, 1964, pg. 437). 182 183 Kay & Crawford's (1964) original concept of the Diana RIDGE CREST NORTHWEST NORTH SLOPE HORTH SLOPE SOUTH OF OF DIANA OF APRIL OF IKE'S CANVON JUNE CANVON PEAK CAHVON 5 -9 a 12 h .v.v; ANTELOPE VALLEV DIANA NASKET LIMESTONE LIMESTONE SHALE WELL-BEDOED SWi WELL-BEDOED, FACIES ■■■" SOMEWHAT MOTTLED CALCITITE BRECCIA MASSIVE CALCARENITE FIGURE 38 FIGURE 39-— a) Carbonate Rudstone Facies on the south wall of Ikes Canyon. Note mixture of tabular and rounded subequant clasts, b) Contact print from acetate peel of polished slab with carbonate rudstone clast from Carbonate Rudstone/Breccia Facies. 184 185 FIGURE 39 FIGURE *10.— a) Polymictic carbonate rudstones below "magic marker" grade vertically into monomictic internal breccias (above marker) which also grade into the Well-bedded Limestone Facies at top of illustration. Marker is 12 cm long, b) Lithologic sequence of the Diana on the south flank of Copper Mt. Well-bedded limestones near the base of the formation are scoured and overlain by carbonate debris flows. 186 FIGURE 1*0 FIGURE 41.— a) Intraformational truncation surfaces in the Well-bedded Limestone Facies exposed on the south wall of Ikes Canyon, b) Slumps and syndepositional folding developed in exposures of the Diana on the southeast side of Copper Mt. 188 189 FIGURE 41 FIGURE U2.— a) Syndepositional folding in slump/slide with internal "core" (underlying sledge at center of photo) of carbonate rudstone/breccia. Exposure on southeast side of Copper Mt. b) Contact print from acetate peel of polished slab of Massive Laminated Facies from south wall of Ikes Canyon. Laminations are not recognizable on the outcrop. 190 191 FIGURE 42 TABLE 6.— Mixed conodont faunal assemblages of the Diana Limestone. 192 TABLE6-MIXED CONODONT FAUNAL ASSEMBLAGES OF THE DIANA DIANA SPECIES DERIVED FROM THE UNDERLYING ANTELOPE VALLEY FORMATION SILURIAN SPECIES Amelia jcmllandica (Lofgrcn 197S) M Dapsihdiis obh'qnicostam (Brnoson &. Mchl 1933) ColcodusJ 5p. of Barnes A: Poplawski, 1973 * Ozarkodina hedra (Micoll Sl Rexroad 1969) Dr«7»u/joaloiUf flnjTifmjij (Harris 1962) Ozarkodina hasti (Pollock, Rcxroad »t Nicoll 197U) PtervctmtioditS sp. * Ozarkodina enravota (Branson & Melil 1933) Genus ct sp. indcl A Ozarkodina sp. A of Mannik (1983) Wxiiadflta n jp . 2 of Harris ct el., 1979 * Ozarkodina sp. HisriodtUa sp. ftrudooncofttius btcomir Dryganl 1974 Juanognathus serpaglii Slougc 1985 •** Piervspzihodtts sp.aff. P. postfritenuit Uyeno & Barnes 1931 Ncomuliicaiodiu sp, * Purospathodat sp.cf, P. eelloni or P. amorphogiathoidcs WalUser 1964 Ntomultioistodus c/>pnu (M ound 1965) Qcp&codus sp. NONDIAGNOSTIC ORDOVICIAN.SILURIAM SPECIES 'Prioniodu? n jp . * PteracontioduS cryptodem (Mound 1965) Icriodcllp sp? Scandodus sinuasus Mound 1965 indcl. phlfotm processes Culodiu sp. OHOOVICIAN SPECIES YOUNGER THAN THOSE FROM THE UNDERLYING Pandervdui sp. ANTELOPE VALLEY lYuIliscrodiis sp. Am&pJiogrttttftus prdwlclcus (Branson & Mchl 1933) * NONDlfttaNOSTlC ORDOVICIAN SPECIES Am & phofftathta tvaerensis (Bergstrom 1962) * *Bryanlodinam sp. Dnpancistadus sp. Cahabopyathiti in « r i (Bcrgsirflm 1971) * indcl. neudiform cletncnis Papsitodus muianis (Branson & Mehl, 1933) * indcl. oiitodontiforin elements E&pfaccffiathtu dongaim (OcigsUum 1962) * P il^d u s sp. Gamtichignatiuix ctnifer McCracken, Nowlati & H antes 1987 **** * Protopamlcrodiu sp. Hoixadotmis girardetMCMit McCracken & Barnes 1931 Nordiodus Ualitus Scrpaglt 1967 Oatodtis sp.cf. O. tabtepobitensit Stouge 1985 'Otjiotoduj* vcniutM Stauffer 1935 ftriodan tup. aff. P, grandis (Elhmgton 1959) • * R cpm lcd in Harris ct aL (1979) Polypiacogwthiu mniasm Stauffer 1935 * •• Synonymous with A. ncvadensis reported in Harris cl al, (1979) Pravognaihus sp. ■'* Synonymous with /. spjfF. /. wriabilU reported in Harris et al. (1979) friwiodut gerdae Bergstrom 1971 * Synonymous with N.gen. nsp. X reported in Harris et al. (1979) Praiopmderodus hxeutpms (Branson & Mchl 3933) * * ***** Synonymous with Ozcskcdina a^p. reported ia Harris et a£ (1979) Prolopanderodus sp. Protopandtmiits liripipus Kennedy, Barnes & Uycno 1979 fsatdooncModtu jp ^ ff. P. mitratui (Moskalenko 1973) fygodus anscrinus Lamor.t & Lindtfrom 1957 * FIGURE 43.— a) Relative percentages of all biostratigraphically significant conodont elements in samples collected from the Diana Limestone in Ikes Canyon. tO Percentage of biostratigraphically significant conodont elements plotted by sample. Several samples of clasts (e.g. 83LD-120c and 83LD-150c) and ’’whole rock" (clasts and matrix in samples 83LD-120w and 83LD-150w) were collected from the Carbonate Rudstone/Breccia Facies. The biostratigraphic composition of conodont faunas of those samples doe3 not differ significantly, possibly because clast3 are difficult to separate from matrix during sampling. 194 IUE 43 FIGURE CUMULATIVE PERCENTAGE B X 0 0 1 AL APE, ETA COLLECTION) LEATHAM SAMPLES, (ALL V Fm. AV 2 0 X • X 0 2 - X 0 4 BOX BOX 2 )— X (2 ( 55 ty— - ) X 3 2 ( o o t ct ct in o APE (ETA COLLECTION) (LEATHAM SAMPLES IN LIMESTONE DIANA n IN LIMESTONE, DIANA in Lmestone Lim Diana t-(40X) n a i i a in — in i m — a 0 1 in m S o 27*) ^ r £ K K Y N K \ \ s \ \ \ \ \ \ \ \ \ t3") — * u ** to 2 KS CANYON IKES <0 N in \ Y I \ \ \ \ \ \ \ \ \ \ \ \ M Fm. RM SILURIAN X Q ^ X UOHAWKIAN TO CINCINNATIAN CINCINNATIAN TO UOHAWKIAN X ^ ODANSI ORDOVICIAN NONDIAGNOSTIC X ^ X X X MOHAWKIAN TO ClNCINNATtAN ClNCINNATtAN TO MOHAWKIAN X X X X SILURIAN SILURIAN X NEOE VALLEY ANTELOPE X ) P (N WHITEROCK1AN X X X LATE ORDOVICIAN ORDOVICIAN LATE X ORDOVICIAN—SILURIAN LATE ORDOVICIAN ORDOVICIAN LATE HTRCIN NP) P (N WHfTEROCKIAN VALLEY ANTELOPE ORDOVICIAN—SILURIAN FIGURE — a) Contact print from acetate peel. Flame structure developed in the upper Antelope Valley Limestone on south wall of Ikes Canyon, b) Bouma A-C sequence in thin-bedded limestones of the upper Antelope Valley Formation on the south wall of Ikes Canyon. 196 FIGURE 45.— Schematic representation of Ordovician-Silurian development and depositional processes of the outer continental margin profile in central Nevada (not to scale). Westernmost exposures of platform carbonates and sandstones occur at Lone Mountain and are incorporated into a generalized east-west trending transect through the Ikes Canyon Window 60 km to the northwest. Evolution of the margin occurred in three structural stages. STAGE 1— Offshore carbonates accumulated along a ramp extending west from the platform margin near Lone Mountain. Conodonts ranging from Ordovician Faunas 6 through 13, present in sediment gravity deposits of the Diana, suggest that accumulation of carbonate along the ramp was quasicontinuous. STAGE 2— Llandoverian subsidence of the ramp induced downward flexure of the margin near the shelf-break, as evidenced at Lone Mt. Resultant ramp-steepening, coupled with flexure-induced seismic waves, effected general slope failure of the quasistable ramp. Emplacement of Diana carbonates by subaqueous slides, slumps, and sediment gravity flows occurred during this stage. Subaqueous removal of section along inter- and intraformational truncation surfaces was commonplace in carbonates west of the flexure. STAGE 3— The carbonate platform east of the shelf-break near Lone Mt. prograded westward over sediment gravity deposits of the continental slope (Roberts Mountains Formation) after Llandoverian marginal flexure. This aggradational/progradational cycle terminated in the Lochkovian. T.R = Toquima Range; L.R. = Lone Mountain. 198 STAGE Lt. Llandoverian-Ludlovian SLOPE RIMMED SHELF E DEPOSmoit OF ROBERTS MTS. FM. SHELF PROGRADATTON DEBRIS FLOWS TURBIDITES T.fl. STAGE 2 E. L!andoverian-E. 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Locomotor diversity within past and present guilds of large predatory mammals. Paleobiology, 11(4):406-428. Walliser, O.H. 1964. Conodonten des Silurs. Abhandlungen des Hessischen Landesamtes fur Bodenforschung, Band 41:1-106. Webb, G.W. 1956. Middle Ordovician stratigraphy in eastern Nevada and western Utah. American Association of Petroleum Geologists Bulletin, 42(10):2335-2377. APPENDICES 214 APPENDIX A Llthologlc descriptions Appendix A includes detailed lithologie descriptions for six Upper Ordovician sections (83LA, 83LB, 83LC, 83LE, 83LF, and 85LT). Locality information is documented in Table 2. The descriptions provide a more- than-adequate stratigraphic field guide to the Upper Ordovician of the eastern Great Basin. Color is reported with Munsell notation. Unless otherwise stated, colors are for weathered surfaces. UT/CT = Unit thickness in feet / cumulative thickness in feet above base of section. Units are numbered consecutively from the base of each section and correspond to the schematic stratigraphic divisions illustrated in chapter I. Descriptions of the upper Middle Ordovician sandstones and lowermost Silurian dolostones are also included for reference. 214 215 83LA Lake3lde Hta.. Utah UNIT DESCRIPTION UT/CT Laketown Dolostone nm Tony Grove Lake Member 529/1030 46 Medium light gray (N6) to light olive gray (5Y6/1) 013/539 medium- to coarse-grained dolostone. Interbedded, discontinuous lithoclastlc and bioturbated beds 0.5 to several ft thick. Bioclasts notably absent. Small-scale, bidirectional planar cross stratification developed in coarse-grained dolomitic sand at the base. Fresh surfaces are medium light gray (N6). 45 Medium gray (N5) to medium olive gray (5Y5/1), 012/526 massive, cliff-forming, medium- to coarse-grained dolostone. Stromatoporoids, tabulate fragments, and solitary rugose corals are common, but not as abundant as in underlying unit. Bioclasts decrease in abundance upwards. Fresh surfaces are medium gray (N5). 44 Medium dark gray (N4) to medium olive gray (5Y5/1), 013/514 massive, recessive, medium- to coarse-grained dolostone. Stromatoporoids (many are overturned and fragmentary) and solitary rugose corals are abundant. Tabulates and brachiopods are common. Basal contact with underlying Fish Haven is disconformable, with 1 to 2 ft of relief. Fresh surfaces are also medium dark gray (N4). Fish Haven Dolostone Total thickness = 501 feet. Bloomington Lake Member 43 Light gray (N7), fine-grained, slightly bioturbated 007/501 dolostone. Several discontinuous intra- and lithoclastlc horizons up to 0.3 ft thick. Notable absence of bioclasts. Basal contact with underlying unit somewhat gradational: irregular light gray intraclasts included in basal 0.3 ft of underlying lithology. Fresh surfaces are medium dark gray (N4). 216 42 Medium gray (N5)» fine-grained, bioturbated 020/494 dolostone. Burrows are filled with medium light gray (N6) to light gray CN7), fine-grained, peloidal dolostone. Concentric bands at burrow edges suggest early diagenetic origin for light- colored burrow-fills, instead of infiltration of open burrow system with light-colored carbonate muds. Sparse macrofaunal elements scattered throughout include small tabulate corals, small orthoconic nautilolds, and a few gastropods. Fresh surfaces are medium dark gray (N4). 41 Medium light gray (N6) to light gray (N7), fine 011/474 grained, poorly exposed dolostone. Spar-filled vugs 1 to 2 cm dia. Peloid-like objects apparent on weathered surfaces near base. Notable absence of biocla3ts. Basal contact styololitic. Fresh surfaces are medium gray (N5). 40 Medium gray (N5), fine-grained, highly bioturbated 012/463 dolostone. A 2 ft horizon of silicified Thalassinoides sp. and small (0.5 cm dia) dolomitized, cylindrical burrows (?Chondrites sp.) occurs about 7 ft above the base. Fresh surfaces are medium dark gray (N4). 39 Medium light gray (N6) to light gray (N7), fine 002/451 grained dolostone. Beds are 0.5 to 1.5 ft thick. Tabular, light gray (N7), imbricated intraclasts up to 5 cm long occur in the central bed. Lowermost bed finely laminated. Fresh surfaces are medium gray (N5) to medium dark gray (N4). 38 Medium gray (N5), thickly laminated, fine- grained 001/449 dolostone. Notable absence of bioclasts. Fresh surfaces are also medium gray (N5). 37 Light gray (N7) to medium light gray (N6), fine 002/448 grained, laminated dolostone. Notable absence of bioclasts. Fresh surfaces are medium dark gray (N4). 36 Interbedded dark [medium light gray (N6) to medium 005/446 gray (N5)] and light [light gray (N7)l, fine grained, laminated dolostone. Undulatory laminations, possibly algal in origin. Upper contact is undulatory (up to 0.5 ft relief) and brecciated, possibly representing unconformity. Possible teepee structures. LLH stromatolites up to 0.5 ft high immediately overlie an undulatory bedding plane 2 ft above the basal contact. Basal 217 contact is also undulatory. Fresh surfaces are medium dark gray (N4) to light gray (N7). 35 Medium light gray (N6), fine-grained dolostone 007/441 bioturbated with light gray (N7) burrow-fills. Fresh surfaces are medium dark gray (N4). 34 Interbedded light gray (N7) to medium dark gray 037/434 (N4), fenestral, fine-grained, laminated, intraclastic, and bioturbated dolostones. Scours, cut & fill structures, and trough cross stratification are common. Intraclasts are commonly imbricated. Several horizons are algal laminites. Notable absence of bioclasts. Beds are 0.1 to 4 ft. thick. Fresh surfaces are medium dark gray (N4) to light gray (N7). 33 COVERED INTERVAL. (Lake Bonneville terrace deposits 014/397 and caliche) 32 Medium dark gray (N4), fine-grained, bioturbated 015/383 dolostone. Burrow-fills are medium gray (N5), fine-grained dolostone, and are assignable to Thalassinoides sp. and Chondrites sp. Fresh surfaces are also medium dark gray (N4). 31 Light gray (N7), fine-grained, irregularly 006/379 laminated dolostone, Undulatory bedding is 0.7 ft thick. Fresh surfaces are light gray (N7). 30 Light gray (N7), fine-grained, bioturbated 005/373 dolostone. Burrows filled with peloids. Silicified Thalassinoides sp. occur in lower 2 ft. Lower contact somewhat undulatory. Fresh surfaces are medium gray (N5). 29 Medium dark gray (N4), fine- to medium-grained, 013/368 massive, bioturbated dolostone. Silicified Thalassinoides sp. are very abundant in the upper third of the unit, and less common in the lower 2/3rds. Pelmatozoan ossicles sparsely scattered throughout. Fresh surfaces are dark gray (N3). 28 Light gray (N7)» fine-grained, thinly laminated 005/355 dolostones. Dark [medium gray (N5)], undulatory laminations occur in the uppermost 0.5 ft. White chert horizons 0.3 to 0.5 ft. thick characterize the lowermost 2 ft. Fresh surfaces are medium gray (N5). 218 27 Medium light gray (N6), fine- to medium-grained, 010/350 somewhat bioturbated dolostone. Lenses of indeterminate bioclastic debris 0.1 to 0.2 ft. thick scattered throughout. Peloids 1 mm dia are concentrated in the burrows. Numerous calcitic- spar-filled vugs 1 to 2 mm dia. Fresh surfaces are also medium light gray (N6). 26 Medium light gray (N6), massive, fine-grained, 013/340 bioturbated dolostone intercalated with 0.1 ft thick horizons of pelmatozoan debris and bioclastic "hash11. Abundant silicified Thalassinoides sp. Some horizons cross-stratified. Fresh surfaces are also medium light gray (N6). 25 Medium light gray (N6), medium- to coarse- grained, 011/327 bioclastic and lithoclastlc dolostone. Bioclasts include abundant pelmatozoan ossicles, brachiopod fragments, and a few gastropods. Oncoids 1-3 cm dia scattered throughout: some have gastropod nuclei. Small, rounded 0.5 to 2 cm dia fine grained, dolomitic lithoclasts are scattered throughout. Pelmatozoan-rich 0.2 ft horizons in the basal foot are crossbedded. Fresh surfaces are medium dark gray (N4). 24 Medium light gray (N6), fine- to medium-grained, 017/316 bioturbated dolostone. Silicified Thalassinoides sp. present throughout. Bioclastic debris (pelmatozoan ossicles and gastropods) most abundant in lower 4 ft. Basal 2 ft are thinly bedded: beds are 0.3 to 0.5 ft thick. Calcite- and quartz- filled vugs scattered throughout. Fresh surfaces are medium dark gray (N4). 23 Light gray (N7), medium-grained, bioturbated 006/299 dolostone. Bioclasts common, and include pelmatozoan ossicles and fragmentary small rugosa. Large, silicified Thala3sinolde3 sp. occur in the basal 2 feet. Fresh surfaces are medium light gray (N6). 22 Light gray (N7)» massive, fine- to medium- grained 004/293 dolostone. Small oxidized pyrite frambolds scatterd throughout. Fresh surfaces are medium light gray (N6). 21 Medium light gray (N6), fine-grained, somewhat 005/289 bioturbated dolostone. Beds are 1.5 ft thick. Dolomitized, erect ?bryozoans (colonies up to 6 cm dia) common. Minor pelmatozoan debris and 219 bioclastic "hash". Burrow systems include Chondrites sp. and Thalassinoides 3p. Basal contact undulatory, with 0.5 ft relief. -Fresh surfaces are medium dark gray (N4). 20 Medium dark gray (N4), fine- to coarse-grained, bioturbated, bioclastic dolostone. Bioclasts 7.5/284 include pelmatozoan ossicles, solitary rugosa, and tabulate corals. Silicified Thalassinoides sp. abundant. Somewhat stylolltized. Small spar- filled vugs. Fresh surfaces are also medium dark gray (N4). 19 Medium dark gray (N4) to medium gray (N5), fine-to medium-grained, stromatolitic and intraclastic 2.5/276.5 dolostone. LLH stromatolites up to 0.4 cm high are partially silicified. Crevice3 between stromatolite heads filled with indeterminate bioclastic debris. Thin intraclastic horizon at base, overlying an undulatory lower contact. Fresh surfaces are medium dark gray (N4). Deep Lakes Member 18 Light gray (N7)» fine grained, algally laminated dolostone. Beds are 0.7 to 0.8 ft thick in the 014/274 upper 2/3rds, and 0.1 to 0.2 ft thick in the basal third. A 1 ft bed of medium gray (N5) dolostone occurs 5 ft above the base. Possible rippled horizon about 1 ft below the upper contact. Fresh surfaces are medium dark gray (N4). 17 Light gray (N7), fine-grained, slightly bioturbated dolostone. Burrows are 0.2 to 0.5 cm dia. Beds 008/260 are 0.2 to 0.3 ft thick. A 1 ft bed of medium gray (N5), fine-grained, bioturbated dolostone with sutured upper and lower contacts occurs 2.5 ft above the base. Polished slabs of that bed reveal Chondrites sp.-style burrowing. Burrows are also filled with peloidal or pelletaly materials. Stylolitic above the dark bed. Fresh surfaces are medium gray (N5). 16 Medium gray (N5), fine-grained, laminated dolo3tone. Beds are 0.1 to 0.3 ft thick. Fresh 004/252 3urface3 are also medium gray (N5). 15 Medium light gray (N6), fine-grained dolostone. Beds are 0.1 to 0.3 ft. thick. A few scattered 005/248 chert nodules occur in the upper and basal foot. Bioclasts include pelmatozoan ossicles, orthid brachiopod valves and tabulate fragments. Many 220 of the bioclasts are silicified. The basal contact is undulatory. Fresh surfaces are medium dark gray CM). 14 Very light gray (N8), cryptocrystalline, thinly 004/243 laminated dolostone with a few fenestral calcite- filled vugs. Uppermost foot darkly laminated immediately overlying a thin intraclastic unit. Fresh surfaces are medium dark gray (N4). 13 COVERED INTERVAL. 035/239 12 Interbedded dark [medium dark gray (N4)] and light 013/204 [light gray (N7) weathered, medium gray (N5) fresh], fine-grained dolostone. Beds are 1.5 to 2 ft thick. Chert beds up to 0.5 ft thick containing large gastropods intercalated with thin-bedded, fine-grained, laminated, pelletal or peloidal, fenestral dolostones occur in the basal 3 ft. The chert is laminated, and the uppermost horizon has been intensely brecciated. Paris Peak Member 11 Medium dark gray (N4), fine-grained, bioturbated, fossiliferous dolostone. Macrofaunal elements 010/191 include abundant solitary rugosa and Catenipora sp., other fragmentary tabulates, stromatoporoids, and rare nautiloids. Abundant silicified Thalassinoides sp. Basal contact undulatory. Fresh surfaces are dark gray (N3). 10 Light gray (N7)» fine- to coarse-grained, bioturbated, laminated dolostone. Burrows filled with coarser carbonates, and rounded sand-sized 008/181 chert grains. Minor indeterminate bioclastic debris. Fresh surfaces are medium light gray (N6). 09 Medium dark gray (N4), fine- to coarse-grained, massive, bioturbated, fossiliferous dolostone. Abundant silicified Thalassinoides sp. scattered throughout. Several of the Thalassinoides sp. 032/173 horizons are also mottled with Chondrites sp. Macrofaunal elements include pelmatozoan ossicles, , solitary rugosa, Catenipora sp., other tabulate corals, stromatoporoids, and minor bryozoans. Several of the larger tabulates are overturned. Fresh surfaces are also medium dark gray (N4). 221 08 Medium dark gray (N4), fine- to coarse-grained, 006/141 bioturbated dolostone. Burrow-fills are medium gray (N5) to medium light gray (N6). Macrofaunal elements include solitary rugosa, Catenipora sp., other large tabulate corals, stromatoporoids, gastropods and minor bryozoans. Basal contact stylolitic. Fresh surfaces are also medium dark gray (N4). 07 Light gray (N7), fine-grained, unfossiliferous 018/135 dolostone interbedded with coarse-grained, vugg bioclastic horizons. Bioclastic horizons become more dominant near the top of the unit, and are dominated by pelmatozoan debris. The basal foot is marked by fossiliferous horizon rich in gastropods, solitary rugose fragments, and indeterminate bioclastic materials. Fresh surfaces are medium light gray (N6). 06 Medium light gray (N6), massive, fine-grained, 022/117 vuggy dolostone. Vugs filled with dolomitic spar. Sparse gastropod fauna. Lowermost 5 ft are bioturbated. Basal contact stylolitic. Fresh surfaces are medium gray (N5). 05 Light gray (N7), finely laminated, fine-grained 002/095 dolostone. Stylolitic basal contact. Fresh surfaces are medium light gray (N6). Oil Medium dark gray (Nil), fine-grained, bioturbated 003/093 dolostone. Burrow-fills are medium- to coarse grained. Basal contact undulatory and stylolitic. Fresh surfaces are also medium dark gray (N4). 03 Light gray (N7), fine-grained, fenestral dolostone. Beds are 0.3 to 0.7 ft thick. Several horizons are 016/090 laminated. A 1 ft thick bed of bioturbated, fine grained, medium dark gray (N4) bioturbated dolostone occurs 4 ft above the base of the unit. Notable absence of bioclasts. Basal contact is undulatory, with 0.5 ft of relief. Fresh surfaces are medium dark gray (N4). 02 Dark gray (N3) to medium dark gray (N4), fine- to medium-grained bioturbated, dolostone. Faunal elements include Paleophyllum sp., large domal 031/074 stromatoporoids, tabulate corals, pelmatozoan debris, fragmentary solitary rugosa, minor indeterminate brachiopods, and possible bryozoans. Silicified Thalassinoides sp. are scattered throughout. Siliceous stylolites occur in several horizons. Fresh surfaces are medium dark gray (N4). 01 COVERED INTERVAL. Lake Bonneville terrace an talus 043/043 slope. Large scree (up to 4 m dia) of medium dark gray (N4), fine-grained, dolostone with large in situ stromatoporoids. Contact with underlying Swan Peak Quartzite not exposed for approximately 2 miles along strike, and coincides with a large, unmapped normal fault and with Lake Bonneville terrace deposits and caliche. Contact chosen at highest occurrence of Swan Peak float in terrace deposits. SWAN PEAK QUARTZITE Covered and faulted in the area studied. Talus unknown suggests beds are 0.3 to 0.8 ft thick, well sorted quartzose sandstones, bioturbated, and rippled. 223 83LB Silver l3land Range UNIT DESCRIPTION UT/CT Roberts Mountains Formation Alternating medium dark gray (N4) and medium light nm gray (N6), medium- to coarse-grained dolostone. Beds are 0.3 to 0.7 ft. thick. Lithologies include coarsely laminated dolostones, intraformational dolomititic conglomerates and breccias, and bioclastic dolostones. Slump structures, thin horizons of chertj neptunian dikes, and carbonate mass-flow deposits scattered throughout. Dolomititic clasts in mass flow deposits up to 5 ft dia., and are predominantly medium light gray (N6). Quartz silt scattered throughout. Macrofaunal elements include rare Paleophyllum sp. and pelmatozoan ossicles. Clasts of underlying Ely Springs Dolostone included in basal intraformational conglomerates at several localities. Basal contact undulatory, with several feet of relief. ELT SPRINGS DOLOSTONE Total thickness about 490 ft. Floride Member 22 Medium light gray (N6), fine- to medium-grained, 054/490 bioturbated dolostone. A discontinuous 3 ft thick horizon of breccia (clasts are tabular and slightly lighter in color) occurs just below the irregular upper contact. Predominantly unfossiliferous, although several bioclastic horizons are present. Bioclasts in those horizons include pelmatozoan debris, fragmentary solitary rugosa, and indeterminate articulate brachiopods. Several horizons exhibit moldic porosity. A few, disseminated quartz silt grains occur about 10 below the upper contact. Beds range from 0.3 to 0.7 ft thick. Lake Bonneville tufa (up to 1 ft thick) coats much of this unit. Fresh surfaces are medium gray (N5). 21 Medium light gray (N6), massive, fine to medium- 016/436 grained, highly bioturbated dolostone. Pelmatozoan ossicles and indeterminate bioclastic debris scattered throughout. Fresh surfaces are medium gray (N5). 20 COVERED INTERVAL. Unit i3 recessive. No exposures 075/420 in this outcrop belt. Lo3t Canyon Member 19 Medium dark gray (N4), fine- to medium-grained, 019/345 bioturbated dolostone. Beds are about 1 ft thick. Abundant silicified Thalassinoides sp. Bioclasts include abundant pelmatozoan debris and fragmentary solitary rugosa. Stringers of partially silicified bioclasts common as burrow infillings. A few scattered oncoids (1 cm dia). Fresh surfaces are also medium dark gray (N4). 18 Medium dark gray (N4), fine- to medium-grained, 011/326 bioturbated dolostone. Beds are about 1 ft. thick. Bioclasts (partially silicified) include pelmatozoan debris and indeterminate "hash". Fresh surfaces are also medium dark gray (N4). 17 Medium dark gray (N4), fine- to medium-grained 035/315 dolostone characterized by interbedded oncolitic and bioclastic horizons rich in pelmatozoan debris. Beds are about 1 ft. thick. Oncoids are about 1 cm dia. Bioclastic horizons somewhat bioturbated, and contain a few fragments of solitary rugosa. Fresh surfaces are medium dark gray (N4). 16 Medium dark gray (N4), fine- to medium-grained, 023/280 bioturbated, bioclastic dolostone. Beds are 0.5 to 1.5 ft thick. Thalassinoides sp. common, some of which are selectively silicified. Macrofaunal elements include abundant pelmatozoan debris, silicified Catenipora sp., solitary rugosa, bryozoans, and indeterminate articulate brachiopod3. Basal contact is slightly undulatory, and marked by sparse, discontinuous chert nodules. Fresh surfaces are also medium dark gray (N4). 15 Interbedded dark [grayish black (N2)] and light 015/257 [medium light gray (N6)], fine-grained, somewhat laminated dolostone. Beds are 1 to 2 ft thick. Beds are undulatory and interfingered: several lenses, and possible flame structures are present. Notable lack of bioclasts and burrows. Fresh surfaces of dark dolostones and light dolostones are dark gray (N3) and medium gray (N3) respectively. 14 Dark gray (N3)» fine-grained dolostone. Beds are somewhat undulatory, and 0.5 to 1 ft thick. Notable absence of bioclasts. Several 027/242 horizons of small burrows (?Chondrites sp.) present. Fresh surfaces are medium dark gray (N4). 13 Interbedded dark [grayish black (N2)] and light [medium gray (N5)3, fine-grained, coarsely laminated, somewhat bioturbated dolostones. Beds 013/215 range from 1 to 2 ft thick. Minor chert nodules occur just below upper contact. Bioclasts are notably absent. Fresh dark and light surfaces are grayish black (N2) and medium gray (N5) respectively. Butterfield Springs Member 12 Dark gray (N3), fine-grained, bioturbated 022/202 dolostone. Beds are 1.5 to 2 ft thick. Pelmatozoan and indeterminate bioclastic debris disseminated throughout. Spar-filled vugs up to 0.5 cm dia scattered throughout. Irregular basal contact. Fresh surfaces are medium dark gray (N4). 11 Medium gray (N5) to light olive gray (5Y6/1), fine 015/180 grained, coarsely laminated dolostone. Pelmatozoan debris scattered throughout. Fresh surfaces are medium gray (N5). 10 Medium gray (N5) to light olive gray (5Y6/1), fine 015/165 grained, bioturbated dolostone. Macrofaunal elements include pelmatozoan debris, minor solitary rugosa, and rare, large Catenipora sp. Fresh surfaces are also medium gray (N5). 09 Medium gray (N5), massive, fine-to medium-grained, 025/150 bioturbated dolostone. Abundant silicified Thalassinoides sp. Catenipora sp. common. Other bioclasts include minor solitary rugosa, pelmatozoan debris, and indeterminate l,hash,t. Basal contact is irregular. Fresh surfaces are also medium gray (N5). 08 Medium dark gray (N4) to dark gray (N3), fine 020/125 grained, massive, bioturbated dolostone. Bioclasts include minor solitary rugosa and pelmatozoan ossicles. Stylolites scattered throughout. Fresh surfaces are medium dark gray (N4) to medium gray CN5). 226 07 Medium gray (N5), fine-grained, massive, 036/105 bioturbated dolostone. Macrofaunal elements include pelmatozoan ossicles, solitary rugosa, and stromatoporoids. Stromatoporoids are most abundant near the top and bottom of the unit. Minor silicified Thala33inoides sp, occur at several horizons, and are common in the uppermost 2 ft. Fresh surfaces are medium gray (N5). Ibex Member 06 Medium gray (N5), fine- to medium-grained, massive, 010/069 bioturbated, quartz-sand-bearing dolostone. Quartz-sand content minimal (i.e. <555). Macrofaunal elements include solitary rugosa, orthid brachiopods, and pelmatozoan ossicles. Basal contact somewhat gradational. Fresh surfaces are medium gray (N5). 05 Medium gray (N5), fine- to medium-grained, massive, 009/059 bioturbated, quartz-sand-bearing dolostone. dolostone. Quartz sand abundant, well rounded, and well sorted. Sand is concentrated in burrows. Macrofaunal elements notably absent. Irregular basal contact. Fresh surfaces are medium gray (N5). 04 Medium gray (N5), fine-grained, massive dolostone 015/050 cut by several vertical dikes filled with breccia (2-3 cm dia) from overlying unit. Quartz sand not visible in outcrop. Purplish chert nodules decrease towards top of unit. Minor, scattered pelmatozoan debris. Fresh surfaces are medium dark gray (N4). 03 Medium gray (N5), fine- to medium-grained 020/035 dolostone. Beds are 0.3 to 0.7 ft thick and undulatory. Black (N1) chert nodules (with purplish weathering rind) abundant. Lenses, 0.2 to 0.5 ft thick, of abundant pelmatozoan ossicles, orthid brachiopods (Platy3trophia sp. and indeterminate dalmanellids), and indeterminate bioclastic debris occur throughout. Fresh surfaces are medium dark gray (N4). 02 COVERED INTERVAL. 012/015 01 Medium dark gray (N4), fine- to coarse-grained, 003/003 quartz sand-bearing dolostone. Quartz sand grains are extremely abundant, well rounded, and well sorted. An abundant, silicified macrofauna of brachiopods (dalmanellids, rhynchonellids, and Platy3trophia sp.)t solitary rugosa, bryozoa, pelmatozoan ossicles, and small (about 0.5 cm dia), indeterminate barrel-shaped fossils i3 present. Burrows, 1 to 2 cm dia, are filled with quartz sand. Basal contact is sharp. The uppermost bedding plane is well exposed. Fresh surfaces are medium dark gray (N4). EUREKA QUARTZITE Very light gray (N8) to pinkish gray (5YR8/1), quartzose sandstone. Grains are well rounded and well sorted. Uppermost 3 ft are bioturbated and friable. 228 83LC Lone Mountain Section UNIT DESCRIPTION UT/CT Roberts Mountains Formation Total formation not measured 20 Light gray (N7) medium- to coarse-grained nm irregularly laminated dolostone and discontinous light gray to grayish red purple (N7-5RP4/2) chert stringers. 19 Light olive gray to medium brownish gray (5Y6/1- 047/292 5YR5/1) medium- to fine-grained peloidal and laminated dolostones regularly interstratified every 3 to 8 cm by bands of coalesced medium gray (N5) chert stringers. The chert is a diagenetic replacement of the dolostone. Vugs (up to 4 cm diameter) filled with dolostone spar and coarse quartz silt are scattered throughout. The vugs are probably synsedimentary, and formed prior to lithification, as evidenced by drapes of laminated dolostones overlying the vugs. Several beds near the base of the unit exhibit small, almost recumbent folds up to 1 m in amplitude. The lower contact of the unit is regular and sharp. 18 Light olive gray to light gray (5Y6/1-N7) medium- 018/245 grained, predominantly peloidal, laminated and bioturbated dolostones. Bioclasts are limited to a few disseminated pelmatozoan ossicles. The upper half of the unit is characterized by irregular grayish orange pink (5YR7/2) dolostone bands associated with disseminated quartz silt. The general lithology and appearance of the unit is more similar to the depositlonal package traditionally referred to the Roberts Mountains Formation, although previous workers have lumped it with the Hanson Creek Formation because it lacks the prominent chert bands. The lower contact is irregular, and basally contains dark clasts derived from the underlying unit. 17 Dark brownish gray (5YR3/1) medium- to fine 014/227 grained dolostone. Numerous LLH and discontinuous stromatolites are often capped by doloraitic spar- filled vugs similar to those described in unit 19. Irregularly shaped intraclasts averaging 2-6 cm dia are disseminated throughout. Minor pelmatozoan 229 debris. Both upper and lower contacts are highly irregular and probably represent erosional surfaces. Upper contact displays about 0.5 ft of relief. Base of unit contains a few clasts lithologically similar to the underlying unit. ELY SPRINGS FORMATION Total thickness =213 feet. Floride Member 16 Light brownish gray to medium olive gray (5YR6/1- 018/213 5Y5/1) medium-grained dolostone. Minor pelmatozoan debris. Unit is highly bioturbated and massive. Irregular upper contact. Irregular fissures filled with dark dolostone from overlying unit. 15 Light olive gray to pale red (5Y6/1-5R6/2) fine 020/195 grained ?structureless dolostone with disseminated grains of coarse quartz silt. Beds average 8 to 10 inches thick. Notably unfossiliferous. Cobre? Member 14 Light brownish gray to medium brownish gray 12.5/175 (5YR6/1-5YR5/1) (weathered) fine-grained dolostone. Fresh surfaces dusky yellowish brown to dusky brown (10YR2/2 to 5YR2/2). Beds average 8 to 10 inches thick. 13 Light olive gray (5Y6/1) medium- to fine-grained 10.5/162.5 somewhat bioclastic dolostone. Bioclasts include solitary rugose corals and brachiopods (including sillcified sowerbyellids). Unit is bioturbated and massive. 12 Light olive gray (5Y6/1) fine-grained dolostone 005/152 faintly stained with hematite. Sparse chert nodules 1 to 3 cm dia present. Unit is somewhat bioturbated with beds about 0.5 to 1 ft thick. Fresh surfaces are brownish gray to very dusky red (5YR4/1-10R2/2). 11 Light olive gray (5Y6/1) fine- to medium grained, 022/147 slope-forming dolostone. Fresh surfaces brownish gray to medium dusky red (5YR4/1-10R3/2). 10 Light brownish gray (5YR6/1) brecciated medium- 005/125 grained bioclastic (pelmatozoan) dolostone. 09 Light brownish gray (5YR6/1) medium-grained 025/120 peloidal dolostone with deformed, grayish red (10R4/2), very fine-grained, laminated intraclasts and subround to round lithoclasts of similar lithology. Clasts range from <1 cm to several cm in diameter. Irregular doloraite-spar-filled vugs. Poorly exposed and slope-forming. Butterfield Springs Member 08 Light brownish gray (5YR6/1) (both weathered and 020/095 fresh) medium- to coarse-grained bioclastic dolostone. Bioclasts include pelmatozoan and brachiopod fragments. 07 Light brownish gray (5YR6/1) medium- to coarse 008/075 grained bioclastic dolostone, Pelmatozoan debris disseminated throughout. Solitary rugose corals, most abundant in upper part of unit. 06 Brownish gray (5YR4/1) (both weathered and fresh) 032/067 medium- to coarse-grained bioclastic dolostone. Fossils include pelmatozoan debris, solitary rugose corals, Paleophyllum sp., cateniform corals, and possible dasycladaceans. Brecciated horizons present at several horizons; veinlets filled with dolomititic spar. Beds are massive, and unit appears bioturbated. 05 Light brownish gray (5YR6/1) medium- to coarse 003/035 grained bioclastic dolostone. Bioclast3 include pelmatozoan debris and fragmentary solitary rugose coral fragments. 04 Light brownish gray (5YR6/1) fine-grained dolostone 001/032 with undulose laminations and oncolds. Fresh surfaces medium gray (N5). 03 Brownish gray (5YR4/1) medium- to fine-grained, 015/031 massively bedded, bioclastic dolostone. Biogenic materials include pelmatozoan debris, solitary rugose corals, and Paleophyllum sp. Oncoids and and possible lithoclasts present at several horizons. Abundant calcite-filled fissures present. Fresh surfaces medium gray (N5). Ibex Member 02 Light brownish gray (5YR6/1) medium-grained 013/016 dolostone. Sparse quartz sand and phosphatic debris disseminated throughout. Pelmatozoan debris 231 present. Beds are 1 to 3 ft thick, and are characterized by undulose bedding planes. 01 Light brownish gray (5YR6/1) coarse-grained, 003/003 soraewhat-bioturbated dolostone with abundant quartz sand and phosphatic debris. Pelmatozoan debris present. The unit contains oncoids and angular clasts of sandy dolostone or dolomitic sandstone. Fresh surfaces medium dark gray (N4). Base of unit contains small (0.5 cm dia) burrows. Contact with underlying Eureka characterized by an irregular bedding plane that separates dolomitic sandstone from sandy dolostone. EUREKA QUARTZITE Uppermost Eureka characterized by medium-grained nm subround to round quartz sand with little to no organic carbon. Angular gray clasts of quartz- sand dolostone directly underly contact with overlying Ely Springs. 232 83LE South Egan Range UNIT DESCRIPTION UT/CT Laketown Dolostone Tony Grove Lake Member 32 Light brownish gray (5YR6/1) fine- to medium- nra grained, somewhat bioclastic dolostone. Bioclasts include stromatoporoids, solitary rugose corals, pentamerid brachiopods, and minor pelmatozoan debris. Small <<0.5 cm dia) burrows are observable on polished slabs of the fine-grained dolostone. 31 Brownish gray to medium brownish gray (5YR4/1- 009/481 5YR5/1), fine- to medium-grained, slightly laminated dolostone intercalated at about 0.5 ft intervals with 1 cm thick chert horizons. Dolostone is mottled with a few Thala33inoides sp., some of which are silicified. A 0.5 ft. thick, flat-pebble intraclastic horizon, with light brownish gray (5YR6/1) clasts of fine-grained dolostone up to 5 cm long and 2-3 cm thick, is present 4 ft above base of the unit. Ely Springs Dolostone Total thickness = 472 feet. Floride Member 30 Light brownish gray <5YR6/1) to light gray (N7) 001/472 dolomitized oolitic grainstone. Unit consists of two, 0.5 ft beds. Lower bed characterized by abundant, rounded, quartz sand grains, which are sparsely disseminated in the upper bed. Peloids and fine-grained dolomitic lithoclasts are abundant in both beds. Lower bed somewhat stylolitized. Reddish tinge of beds due to inclusions of leached pyrite. Color of freshly broken surfaces i3 grayish red (5R4/2). 29 Light gray 28 Light gray (N7) fine-grained dolostone. Poorly 017/462 preserved minor bioclasts include pelmatozoan ossicles, brachiopod and solitary rugosan fragments. Beds are 3-5 ft thick. Burrow-like vugs filled with white dolomitic spar present near base of unit. 27 COVERED INTERVAL. 015/445 26 Very light brownish gray (5YR7/1)* massive, 002/430 dolomitized micstone. Bioturbated with small (0.5 cm dia) burrows. Outcrop notably unfossiliferous. A few chert nodules and stringers (possibly silicified Thalassinoides sp?) are present. 25 Very light brownish gray (5YR7/1) fine-grained 013/428 dolostone with stringers of dolomitized pelmatozoan/brachiopod grainstone. Some of the stringers are silicified and are associated with chert nodules. Beds range from 0.3 to 1 ft thick. 24 Very light brownish gray (5YR7/1) dolomitized 12.5/415 mudstone characterized by undulatory bedding, 0.2 to 0.3 ft thick. Silicified and unsilicified Chondrites sp? (burrows 1 cm dia) concentrated along bedding planes. Unit notably' unfossiliferous. A brecciated zone 2 to 15 cm thick containing angular clasts of brownish gray (5YR4/1) dolostone that range in size from several mm to 6 cm in a light olive gray (5Y6/1) matrix of micrite separates occurs at the base of the unit. The zone is partially silicified. 23 Very light brownish gray (5YR7/1) to light brownish 15.5/402.5 gray (5YR6/1), fine-grained, bioturbated dolostone. Solitary rugosa, indet brachiopods, and pelmatozoan ossicles, are present but not common. Fresh surfaces are dark brownish gray (5YR3/1) to brownish gray (5YR4/1). Beds are 1 to 3 ft thick. 22 Light brownish gray (5YR6/1), fine- to medium- 010/387 grained dolostone (predominantly dolomitized packstone characterized by an abundant benthic macrofauna. The fauna includes (in approx. order of abundance): solitary rugosa, brachiopods, pelmatozoan ossicles, tabulate corals, and one (1 ft dia) saucer-shaped, silicified chaetid sponge. The tabulate corals are most abundant in the upper 2 feet of the unit. Beds range from 1-3 ft. Minor chert nodules and light gray (N7) dolostone-filled burrows occur in the upper 4 ft. A few 234 orthid brachiopods are included in some of the chert nodules. The basal contact is undulatory with a 0.5-1 era reddish orange, clay-rich parting. 21 Light olive gray (5Y6/1), very fine-grained 027/377 argillaceous dolostone. Beds are thin and undulatory, ranging from 3 to 5 era thick. Coarsely silicified dalraanellid/oniellid orthid brachiopods are common in some beds, and pelmatozoan ossicles (including some pentagonal varieties) are sparsely disseminated throughout. Small, predominantly horizontal, subcylindrical burrows 0.5 cm dia are common at a few horizons. Fresh surfaces are olive gray (5Y4/1). 20 COVERED INTERVAL. 006/350 Butterfield Springs Member 19 Light brownish gray (5YR6/1) fine-grained 003/344 bioturbated dolostone. Pelmatozoan debris scattered throughout. Small patches of medium- grained dolostone occur throughout. 18 Light brownish gray (5YR6/1) medium- to coarse 026/341 grained dolostone with abundant solitary rugosa, crinoidal debris, and brachiopod fragments. Many of the fossils are silicified. Large orthoconic nautiloids are also present, but uncommon. Beds are generally over 1 ft thick. Somewhat bioturbated. 17 Light brownish gray (5YR6/1) medium- to coarse 020/315 grained bioclastic dolostone. The macrofauna consists mainly of solitary rugosa and pelmatozoan debris. Somewhat bioturbated. Lenses of silicified sand-sized bioclasts associated with chert nodules occur in the upper 5 ft of the unit. A 0.5 ft bed of 1 cm dia oncoids and rounded dolostone lithoclasts occurs about 12 ft above the base. Beds range from 1 to 3 ft thick. 16 Light brownish gray (5YR6/1) medium- to coarse 010/295 grained dolostone intercalated at about 1.5 ft intervals with chert nodules and stringers. Some of the chert represents 3ilicified Thalaslnoides sp. Beds range from 0.3 to 1 ft thick. The raacrofauna is predominantly fragmented and includes solitary rugosans and pelmatozoans. Peloids are also present, and are best observed on polished slabs. 235 15 Light brownish gray (5YR6/1) fine-grained dolostone 027/285 with abundant chert nodules and stringers. Bioturbated. Lenses of silicified bioclastic (predominantly pelmatozoan) debris occur throughout. Several horizons include alternating laminae of coarse- and fine-grained dolostones. 14 Light brownish gray (5YR6/1), massive, bioturbated, 028/258 fine-grained dolostone with solitary rugosa, pelmatozoan debris, small dalmanellid orthid brachiopods, gastropods and a few chert nodules scattered throughout. A 2 ft horizon of abundant silicified Thalassinoides sp. marks the first occurence of chert in the unit about 8 ft above the base of the unit. 13 Light brownish gray (5YR6/1), fine-grained, 013/230 massive, bioturbated dolostone. Small dalmanellid brachiopods and scattered pelmatozoan ossicles are dispersed throughout. No solitary rugosa. A few sparse chert nodules occur in lower half of unit. 12 Light olive gray (5Y6/1), fine- to medium-grained 18.5/217 dolostone. Beds in the lower 2/3rds of unit range from 1 to 3 ft thick, and are notably thinner in the upper third (i.e. 0.3 to 1 ft thick). The abundant benthic macrofauna includes solitary rugosa, dalmanellid brachiopods, and pelmatozoan ossicles. Slightly bioturbated. Small dolomitic spar-filled vugs and veinlets scattered throughout, 11 Light olive gray (5Y6/1), fine-grained, unmottled 16.5/198.5 dolostone intercalated with highly burrow-mottled dolostone. Beds range from 0.3 to 1 ft thick. A 2 ft horizon containing an abundant benthic macrofauna dominated by cateniporoid corals, large solitary rugosa, and Paleophyllum sp. occurs about 10 ft above the base of the unit. Abundant solitary rugosa, dalmanellid brachiopods, and pelmatozoan ossicles are scattered throughout. Dolomitic spar-filled vugs and veinlets present. 10 Light olive gray (5Y6/1), fine-grained, thick- 016/182 bedded 0 2 ft.), cliff-forming dolostone disseminated with silicified dalmanellid brachiopods and pelmatozoan debris. White dolomitic spar-filled veinlets present. Fresh surfaces are medium dark gray (N4). 236 09 Medium light gray (N6), light brownish gray 012/166 (5YR6/1), and very light brownish gray (5YR6/1), color-mottled, fine-grained dolostone. Bioturbated, with beds 0.2 to 1 ft thick. Macrofossils included abundant solitary rugosa, pelmatozoan ossicles, and dalmanellid brachiopods, and rare large orthoconic nautiloids (about 2 ft long). Many of the fossils are silicified. Fresh surfaces medium dark gray (N4). 08 Light gray (N7), nodular, very fine-grained 5.5/154 dolostone. Beds 1 to 3 inches thick. Possibly bioturbated. Moderate red to moderate reddish brown (5R4/6 to 10R4/6) clay-rich partings < 0.5 cm thick occur between beds and as wisps in possible bioturbated horizons. No bioclasts observed in outcrop. Fresh surfaces medium dark gray (N4) to olive gray (5Y4/1). Basal foot of unit is brecciated, with clasts ranging from 3 mm to 3 cm in length. 07 Light olive gray (5Y6/1), fine-grained dolostone 11.5/148.5 mottled with very light olive gray (5Y7/1) burrows. Beds 0.7 to 1 ft thick. Bioclasts disseminated throughout unit include pelmatozoan ossicles, dalmanellid brachiopods, possible gastropods, and rare solitary rugosa. Fresh surfaces medium dark gray (N4). Patches stained moderate reddish brown (10R4/6) near top of unit. Basal third gradationally interbedded with lithology of underlying unit. 06 Medium light gray (N6), light brownish gray 013/137 (5YR6/1), and very light brownish gray (5YR7/1)* color-mottled, fine-grained dolostone. Bioturbated, with beds 0.3 to 0.7 ft thick. Bioclasts disseminated throughout unit include pelmatozoan ossicles, dalmanellid brachiopods, possible echinoid spines, and rare gastropods. Irregular, dolomitic spar-filled vugs are also present. Fresh surfaces are medium dark gray (N4). 05 Light brownish gray (5YR6/1), slightly bioturbated, 024/124 fine-grained dolostone. Undulatory beds range from 0.2 to 0.5 ft thick. Sparse bioclasts include pelmatozoan ossicles, dalmanellid brachiopods, and very rare solitary rugosa. Irregular dolomitic 3par-filled vugs and veins 1-2 cm dia present throughout. Fresh surfaces are dark gray (N3). 04 Light brownish gray (5YR6/1), medium- to coarse 0 2 0 /1 0 0 grained, slightly bioturbated dolostone. Hummocky stratification, beds are 0.3 to 1 ft thick. Bioclasts (pelmatozoan ossicles, minor brachiopods, and indet. "hash") concentrated in lenses. Calcitic spar-filled vugs 1-2 cm dia occur in upper 4 ft of unit. Fresh surfaces are medium gray (N5). 03 Light brownish gray (5YR6/1), medium- to coarse 035/080 grained, slightly bioturbated dolostone. Beds range from 1 to 2 ft thick. Minor chert nodules and possible silicified Thalassinoides sp. (2-3 cm dia). Bioclasts include common silicified dalmanellid brachiopods and abundant pelmatozoan debris. A 3 ft "spaghetti" horizon of Chondrites sp. (3 mm dia) occurs about 15 ft above the base of the unit. Fresh surfaces medium dark gray (N4). 02 Light brownish gray (5YR6/1), slope-forming,fine- 030/045 to medium-grained, slightly bioturbated dolostone. Minor chert nodules. Bioclasts include abundant pelmatozoan ossicles. Beds are about 1 ft thick. Fresh surfaces medium gray (N5). Ibex Member 01 Medium gray (N5), bioturbated dolostone with well 015/015 rounded, well sorted quartz sand and abundant pelmatozoan debris disseminated throughout. Beds are 1-2 ft thick. Stylolites and chert nodules present in lower third of unit. Basal contact is distinct and regular, representing change from dolomitic sandstone to medium gray, sandy dolostone. EUREKA QUARTZITE Uppermost Eureka characterized by very light gray nm (N8), bioturbated, dolomitic sandstone with well rounded, well sorted quartz sand. 238 83LF Barn Hills, Utah UNIT DESCRIPTION UT/CT Laketown Dolostone Tony Grove Lake Member Medium yellowish brown (10YR 5/2), medium- to nm coarse-grained bioclastic dolostone. Bioclasts include stromatoporoids, pelmatozoan debris, fragmentary solitary rugosa, and small tabulate corals. Many of the stromatoporoid mat3 are overturned. The lowermost Tony Grove Lake Member is somewhat variable in lithology; beds are one to three feet thick, some are mottled with lighter (N6) dolostone, and others display faint laminations. Fresh surfaces are medium dark gray (N4). Ely Springs Dolostone Total thickness = 528.5 feet. Floride Member 35 Light brownish gray (5YR 6/1) to medium light gray 18.5/528.5 (N6), fine-grained, interbedded laminated and mottled dolostone. Beds are 3 to 4 feet thick. No observed bioclasts. Upper 0.5 ft. of unit is slightly stylolitized and contains small pods of disseminated fine-grained quartz sand, and a few fenestral vugs of possible bioclastic origin. Fresh surfaces are brownish gray (5YR 4/1) to olive gray (5Y 4/1). 34 Light brownish gray (5YR 6/1) to medium light gray 005/510 (N6), fine-grained dolostone mottled with slightly lighter dolostone. Chert nodules and silicified Thalassinoides sp. scattered throughout. Fresh surfaces are medium dark gray (N4). 33 COVERED INTERVAL. Exposed talus resembles 010/505 underlying unit, except that beds appear to be 1 ft thick. 32 Light olive gray (5Y 6/1), fine-grained, fenestral 019/495 dolostone. Beds are 3 to 4 ft thick in the upper third of the unit, and 1 to 3 ft thick in the lower 2/3rds. A horizon of thin, tabular intraclasts (0.5 to 1 cm thick) occurs about 9 ft above the base of the unit. Although allochems are not 239 readily observed in outcrop, polished slabs from the basal third of the unit display a beautiful ooid-lithoclast-peloid packstone or grainstone. Orthochem-type is obscured by dolomitization. The allochems are rounded and elliptical to spherical in shape, and many are encompassed by micrite envelopes. Stylolites scattered throughout. Fresh surfaces are medium light gray (N6). 31 Light olive gray (5Y6/1) to brownish gray (5YR4/1), 014/476 somewhat bioturbated, fine-grained dolostone. Beds are 1 to 3 ft thick. Beds coarsely laminated, alternating light olive gray (5Y6/1) with brownish gray (5YR4/1). Small, fenestral vugs filled with dolostone spar. Minor indeterminate bioclasts. Fresh surfaces are medium dark gray (N4). 30 Light gray (N7)» fine-grained dolostone. Beds are 009/462 3 to 4 ft thick and coarsely laminated. Sparse dolomitic spar-filled vugs and a few stylolites scattered throughout. Fresh surfaces are medium dark gray (N4). Bioclasts notably absent. 29 COVERED INTERVAL. 005/453 28 Light olive gray (5Y6/1), very fine-grained, 006/448 "lithographic,, dolostone. Beds 0.2 to 0.5 ft thick. Fresh surfaces are medium light gray (N6) to light gray (N7). 27 Dark yellowish brown (10YR4/2), 1 ft beds of fine 004/442 grained dolostone. Thin, irregular lenses (8 cm long by 1 cm thick) of very fine-grained, pale yellowish brown (10YR6/2) dolostone scattered throughout. Peloids up to 1 mm dia are also disseminated through the unit. Fresh surfaces are medium dark gray (N4). 26 Poorly exposed, medium light gray (N6), fine 028/438 grained, slope-forming, somewhat argillaceous dolostone. Beds range from 0.1 to 0.6 ft thick. Although a few beds are highly bioturbated, most are thinly laminated. Unit is capped by an irregular, 0.3 ft bed with abundant dalmanellid brachiopods. A few horizons are intercalated with 0.5 cm thick chert beds. Minor silicified Thalass- inoides 3p. occur in the lower 4 ft of the unit. Fresh surfaces are medium light gray (N6) to medium gray (N5). Ostracodes, peloids, and brachiopods are visible in thin-sections. 240 Lost Canyon Member 25 Medium brownish gray (5YR5/1) to light olive gray 035/410 (5Y6/1), massive, cliff-forming, fine- to medium- grained, moderately bioturbated, fossiliferous dolostone. The abundant macrofauna includes: Catenlpora sp., Paleophyllum sp., large tabulate corals (many of which are overturned), solitary rugose corals, stromatoporoids (most abundant near base of unit), pelmatozoan ossicles, bryozoans, and large orthoconic nautiloids. Minor silicified Thalassinoides sp. Fresh surfaces are medium gray (N5). 24 Medium brownish gray (5YR5/1) to light olive gray 040/375 (5Y6/1), massive, cliff-forming, fine- to medium- grained, highly bioturbated dolostone characterized by abundant silicified Thalassinoides sp. Pelmatozoan debris disseminated throughout. Stromatoporoids occur in the basal 5 ft, Catenlpora sp. in the middle, and solitary rugosa in the upper half of the unit. Fresh surfaces are medium gray (N5). 23 Medium brownish gray (5YR5/1) to light olive gray 015/335 (5Y6/1), massive, cliff-forming, fine- to medium- grained, bioturbated dolostone. Minor silicified Thalassinoides sp. Pelmatozoan debris disseminated throughout. Macrofaunal elements include solitary rugosa, tabulata, Catenlpora sp., and rare, large orthoconic nautiloids. Fresh surfaces are medium gray (N5). 22 Medium brownish gray (5YR5/1) to light olive gray 025/320 (5Y6/1), bedded, fine- to medium-grained, bioturbated dolostone. Beds range from 1 to 3 ft thick. Silicified Thalassinoides sp. abundant, and minor pelmatozoan debris scattered throughout. Notable absence of corals. Fresh surfaces are medium gray (N5). 21 Medium brownish gray (5YR5/1) to light olive gray 028/295 (5Y6/1), fine- to medium-grained, bioturbated dolostone. Beds range from 2 to 4 ft thick. Abundant macrofaunal elements include: Paleophyllum sp., Catenlpora sp., solitary rugose corals, tabulate corals, stromatoporoids, large biconvex orthid brachiopods (Platystrophia 3p.), bryozoan3, orthoconic nautiloids, and pelmatozoan ossicles. Indeterminate bioclastic "hash" concentrated in lenses. Solitary rugosa notably absent in upper 241 6 ft of unit. Long axes of both nautiloids and solitary rugosa trend N 60 W. Fresh surfaces are medium dark gray (N4). Barn H1113 Member 20 Light gray (N7), cliff-forming, fine-grained 012/267 dolostone. Upper 7 ft are massive, thickly laminated, and overlie a 2 ft bioturbated bed of light brownish gray (5YR6/1) dolostone mottled with light gray (N7) burrow fills. Lowermost 3 ft are thin-bedded: beds are 0.1 to 0.2 ft thick. Notable absence of bioclasts. Fresh surfaces are light gray (N7). 19 Dark yellowish brown (10YR4/2), fine-grained, 045/255 algally laminated dolostones characterized by undulatory, discontinous laminations, and fenestral vugs. Beds are 0.5 to 1 ft thick. Notable absence of bioclast3. Several horizons are somewhat mottled with lighter dolostone. Small, LLH stromatolites occur basally, and are overlain by algal laminites and several horizons of silicified Thalassinoides 3p. Fresh surfaces are dark gray (N3) to medium dark gray (N4). 18 Light gray (N7), slope-forming, finely laminated, 019/210 fine-grained dolostone. Beds range from 0.3 to 1 ft thick. Notable absence of bioclasts. Fresh surfaces are medium gray (N5). 17 Medium brownish gray C5YR5/1), algally laminated, 004/191 fine-grained dolostone. Beds are 0.5 to 1 ft thick. Fresh surfaces are medium gray (N5). 16 Light gray (N7)» finely laminated, fine-grained 002/187 dolostone. Beds are 0.2 ft thick. Fresh surfaces are medium gray (N5). 15 Medium olive gray (5Y5/1) to medium brownish gray 004/185 (5YR5/1), algally laminated, fine-grained dolostone. Beds are 0.3 to 0.6 ft thick. Lenses of indeterminate bioclastic debris scattered throughout. Fresh surfaces are medium dark gray (N4). 14 Dark yellowish brown (10YR4/2) to light olive gray 011/181 (5Y6/1), massive, finely laminated, fine- to medium-grained dolostone. Fresh surfaces are medium dark gray (N4). The basal 8 ft are highly bioturbated, and are characterized by silicified Thalassinoides sp. and black, bedded chert. The 242 uppermost ohert horizon is 0.5 ft thick and contains external molds of high-spired gastropods. The basal contact is marked by two, 3 cm thick chert bed3. Fresh surfaces are dark gray (N3) to medium gray (N5). 13 Interbedded dark [dark yellowish brown (10YR4/2)] 020/1 7 0 and light [light olive gray (5Y6/1) to light gray (N7)]» cryptocrystalline, fenestral, laminated dolostones. Beds are 0.5 to 2 ft thick. Darker beds somewhat bioturbated. Notable absence of fossils, except for solitary occurence of high- spired gastropod and pellets in dark dolostone at base of unit. Fresh surfaces are dark gray (N3) to medium gray (N5). 12 Light gray (N7), slope-forming, cryptocrystalline, 040/150 laminated dolostone. Beds are 0.5 to 2 ft thick.. Notable absence of bioclasts. Stylolitic near base. Fresh surfaces are medium gray (N5). 11 Dark yellowish brown (10YR4/2), fine-grained, 013/110 bioturbated, bioclastic dolostone. Beds are 1 to 1.5 ft thick. Upper 5 ft highly bioturbated (possibly Chondrites sp.). Macrofauna dominated by abundant low-spired gastropods. Pelmatozoan ossicles and rare orthoconic nautiloids scattered throughout. Fasiculate bryozoa are abundant in uppermost foot of unit. A traceable black chert horizon 0.5 ft thick occurs about 6 ft above the base. Fresh surfaces are dark gray (N3)* 10 Medium yellowish brown (10YR5/2), fine-grained, 005/097 algally laminated dolostone. Sparse chert nodules occur in the uppermost 2 ft. Beds are 0.5 to 0.6 ft thick. Slighty bioturbated. Notable absence of bioclasts. Fresh surfaces are medium dark gray (N4) to medium gray (N5). 09 Dark yellowish brown (10YR4/2), fine-grained, 0 0 8 /0 9 2 dolostone. Beds range from 0.5 to 1 ft thick. Lenses of bioclastic "hash" (pelmatozoan ossicles, brachiopod fragments, and indeterminate bioclast3) and silicified Thala33inolde3 sp. occur in the lower 3 ft. Twig-like bryozoan zooaria (3 mm dia) occur in the uppermost 5 ft. Slightly bioturbated. Fresh surfaces are dark gray (N3) to medium gray (N5). 08 Medium yellowish brown (10YR5/2), fine-grained, 004/084 algally laminated dolostone. Laminations are 1 to 4 cm thick. Minor chert nodules. Notable absence of bioclasts. Fresh surfaces are medium dark gray (N4). 07 Interbedded dark [dark yellowish brown (10YR4/2) to 029/080 medium yellowish brown (10YR5/2)] and light [light olive gray (5Y6/1) to light gray (N7)], fine grained, fenestral, laminated dolostones. Beds are 0.5 to 2 ft thick. Dark beds somewhat bioturbated. Notable absence of fossils in light bed3, although a few dark beds contain sparse pelmatozoan ossicles. 06 Dark yellowish brown (10YR4/2) to grayish black 013/051 (N2) fine-grained dolostone. Undulatory beds range from 0.1 to 1.5 ft thick. Bioclasts include dalmanellid brachiopod fragments, pelmatozoan ossicles, and rare low-spired gastropods. A few horizons contain small burrows (1 mm dia). Fresh surfaces are dark gray (N3). 05 Black (N1), fine-grained dolostone. Beds are 0.2 001/038 to 0.5 ft thick. Fresh surfaces are medium gray (N5). 04 COVERED INTERVAL. 002/037 Ibex Member 03 Light olive gray (5Y6/1), fine- to medium-grained, 007/035 thickly laminated and cross-bedded dolostone. Beds are about 1 ft thick. Fine quartz sand is concentrated in several, planar and trough cross bedded lenses up to 2 ft thick. Rounded and abraded, fine-grained dolomitic lithoclasts and chert occur at the base of the sand lenses. Sparse chert nodules scattered throughout unit. Fresh surfaces are medium dark gray (N4). 02 Medium olive gray C5Y5/1), fine- to medium- 012/028 grained, bioturbated dolostone. Beds are 1 to 3 ft thick. Sparse quartz sand disseminated throughout, but is concentrated in burrow fills. Silicified Thalassinoides sp. are abundant. Bioclasts include fragmentary and disarticulated brachiopods, pelmatozoan ossicles, and possibel dasycladacean thalli. Fresh surfaces are medium dark gray (N4). 01 Light gray (N7), fine- to medium grained, highly bioturbated to cross-bedded, sandy dolostone. Bioturbation and quartz sand content decrease towards the top of the unit. Quartz sand is a common burrow fill in the uppermost 4 ft, whereas light gray (N7) dolostone fills burrows in the lowermost 5 ft. Intense bioturbation is associated with massive, cliff-forming, middle third of unit. The basal contact occurs below first bedded sandy dolomitic sandstones. Beds In the basal third of unit are 0.3 to 0.5 ft thick. Fre3h surfaces are medium gray (N5) to medium light gray (N6). EUREKA QUARTZITE Light gray (N7) to yellowish gray (5Y8/1) friable quartzose sandtone. Grains are well sorted and well rounded. Uppermost Eureka slightly dolomitic and bioturbated. 85LT Toano Range UNIT DESCRIPTION UT/CT Roberts Mountains Formation Medium to medium dark gray (N5-N4), fine-grained, nm laminated dolostone. Some laminae are folded. Spotty accumulations of medium light gray (N6) dolostone cla3ts and lenses of well-sorted quartz sand present near base. Scattered silicified bioclastic debris. Chert beds or stringers become common about 10-15 feet above base of formation. Formational contact irregular with underlying Ely Springs. Ely Springs Dolostone Total thickness about 530 feet. Floride Member 30 Light gray (N7), medium- to coarse-grained, massive 037/530 dolostone with abundant, poorly preserved, silicified megafossils that include orthoconic nautiloids, gastropods, brachiopods-, ?bivalves, etc. Seams of drusy quartz crystals pervade the unit. Irregular upper and lower contacts. Relief on upper contact with Roberts Mountain Formation ranges from 5 to 15 feet. Clasts of unit 29 . lithology occur in base of unit. Clast3 of darker, Roberts Mountain Formation occur near top of unit. 29 Medium light gray (N6) to light gray (N7), massive, 052/493 medium- to very fine-grained (lithographic) dolostone. Minor silicified bioclastic debris rare in lower two/thirds of unit, but increases upward. Bioclasts include rare dasycladacean thalli, oncolites, high-spired gastropods, and indeterminate debris. Irregular upper contact. 28 Massive, Thala3sinoides-mottled dolostone. Beds 044/441 about 10 ft. thick (3 m). Matrix near base of unit is a medium gray (N5) '•wackedolostone" with abundant pelmatozoan and indet. bioclastic debris. Burrows are light gray (N7)» fine-grained dolostone with considerably less bioclastic material. Unit is lighter towards top, and burrows are more difficult to recognize. Burrows at top of unit are cored with silicifed stringers. 27 Covered interval. Probably recessive light- 045/397 colored, fine-grained dolostone similar to unit 25. No outcrops along entire strike-valley. 26 Echinodermal, medium light gray (N6) dolomitized 004/352 grainstone. A few discontinuous chert horizons. Medium gray (N5) on fresh surfaces. Unit best exposed on drainage divide, where my can of blue spray paint exploded and I was drenched by miserable rain. 25 Light olive gray (5Y6/1) dolomicrite float. Very 003/348 recessive unit. No fossils observed. Fresh surfaces are medium light gray (N6). Lost Canyon Member 24 Medium light gray (N6) to medium gray (N5) 097/345 dolomitized wackestone. Bioclasts include pelmatozoan debris, ?Verticellipora [1-2 cm dia.], solitary rugose corals, rare high-spired gastropods about 10 cm high, and oncolites. Frequency of oncolitic horizons increases towards top of unit. Dolostone also darkens towards top of unit. Toano Member 23 Mas3 flow deposits of predominantly dark [i.e. dark 036/248 gray (N3) to grayish black (N2)], fine-grained dolostones interlayered with lighter [i.e. medium dark gray (N4) to medium gray (N5)] dolostones. Flame structures of the lighter lithologies present at base of darker deposits. Some of the darker beds are finely laminated. Isolated patches of pelmatozoan debris are also present. A few of the darker horizons are topped by 3-5 cm long by 0.5 to 0.75 cm dia vertically oriented burrows. The vertical burrows are filled with medium gray (N5) fine-grained dolostone a few darker clasts. The burrows are also truncated on their upper surfaces, and may represent either escape burrows or perhaps hardground borings. A few beds exhibit sparse, meandering traces along bedding surfaces. 22 Same llthology as unit 20, but lacks 006/212 Thalassinoides. 21 Same lithology as unit 19* but not bedded (appears 003/206 to be highly bioturbated). 247 20 Same lithology as unit 18, but lack3 recognizable 003/203 clasts. Top of unit mottled with medium gray 19 Dark gray (N3) to medium dark gray (N4) 006.5/200 fine-grained dolostone probably representing turbidite. Undulatory lower contact. 18 Medium light gray (N6) to light gray (N7) dolomitic 006/193.5 carbonate flow deposits with medium gray (N5) tabular clasts near base of flow and dark gray (N3) angular clasts near top of flow. Upper contact undulatory with 1-2 ft of relief. 17 Dark gray (N3) fine-grained dolostone with a few 012/187.5 isolated chert nodules and pods of silicified pelmatozoan debris. Small (0.3 to 1 cm dia), round to oval medium dark gray (N4) objects with a slightly lighter core may represent either burrowing mottling or oncolitic horizons. 16 Dark gray (N3), fine-grained dolostone with a few 007.5/175.5 tabular medium gray (N5) clasts at base. Upper two feet faintly mottled with light gray (N7) Thalassinoides and contains a few, isolated chert nodules in a dolomitized bioclastic wacke3tone matrix. 15 One to two ft thick dark gray (N3), fine-grained 003/168 dolostone with flat-pebble medium gray (N5) clasts overlain by one to two feet of dark gray (N3) bioclastic dolostone (including solitary rugosa, nautiloids, and pelmatozoan debris) with light gray (N7) "wisps" of fine-grained dolostone. 14 Medium light gray (N6), medium-grained, well-bedded 006/165 (4 cm to about 25 cm) dolostone similar to unit 12. 13 Dark gray (N3) bioclastic wackestone with isolated 007.5/159 solitary rugosa and silicified bioclastic horizons. 12 Light gray (N7) medium-grained unfossiliferous 004.5/151.5 dolostone with a few medium gray (N5) to medium dark gray (N4) 1 to 4 cm thick dolomitic interbeds. Darker beds, lithologically similar to unit 10, contain lighter gray intra- or lithoclasts, and vary somewhat in thickness due to low amplitude undulations. Butterfield Springs Member 11 Medium dark gray (N4) dolostone with isolated chert 010/147 nodules up to 1 ft dia. Lithologically similar to top of unit 10. 10 Dark gray (N3) to medium dark gray (N4) dolostone 022/137 with rare, isolated stromatoporoid mat3 about 6" diameter. Small cateniform corals, fragmentary solitary rugosa, and gastropods are fairly common. Pelmatozoan debris abundant. MWisp3,f of medium light gray (N6) dolostone present. Poorly defined bedding, highly bioturbated. A few small, tabulate coral fragments are also present. Bioclastic content decreases towards top of unit. Cateniform corals also become larger towards top of unit. 09 Medium dark gray (N4) dolostone with large, medium 005/115 light gray (N6) stromatoporoid mats 6" to 1' diameter. Some mats are overturned and all are fragmentary. Unit is gradational with overlying lithologies. Isolated chert nodules at top of unit. 08 Dark gray (N3) to medium dark gray (N4) dolostone 010/110 with chert nodules. Abundant pelmatozoan debris. Wackestone-like fabric. Solitary rugosa and oncolites present. "Wisps*1 of medium light gray (N6) dolostone. No observable beds or laminations. Large cateniform coral observed near top of unit. 07 Dark gray (N3) to medium dark gray (N4) bioclastic 034/090 dolostone. Lower foot of unit characterized by stringers of chert. Lack of distinct bedding. Large (3-6 cm) solitary rugosa dominate the macrobiota. "Wisps" of medium light gray (N6) dolostone and oncolites increase in abundance from unit 06. 06 Dark gray (N3) to medium dark gray (N4) massive 009/056 dolostone. Oncolites present and regularly dispersed in some horizons. Bioclasts arranged in a wackestone-like fabric of medium-grained dolostone, and include indeterminate fragments and pelmatozoan ossicles. 05 Dark gray (N3) to medium dark gray (N4) bioclastic 009/047 dolostone. Massive. Possible ?stromatoporoids (N7 dolostone replacements). Cateniform tabulates present in float. 04 Dark gray (N3) to medium dark gray (N4) bioclastic 009/038 dolostone. Silicified Thalassinoides?. Bioclastic materials (i.e. pelmatozoan debris, small solitary rugosa, and a few isolated indeterminate brachiopod fragments) increase in abundance through the unit. Medium gray (N5) to medium light-gray (N6) ,,wisps,, of dolostone. Cateniform tabulate in float. 03 Dark gray (N3) to medium dark gray (N4) 012/027 medium-grained dolostone. Massive. Possible quartz sand. Bioclasts include pelmatozoan ossicles and indeterminate "hash". 02 COVERED INTERVAL (probably lithologically similar 007/015 to units 1 or 3). 01 Medium light gray (N6) fine-grained dolostone. 008/008 Quartz sand and silt disseminated throughout, but tend to be concentrated in "limonite,,-stained bands about 1 cm thick. Planar cross-stratification. Exposures are highly fractured and coated with calcrete. EUREKA QUARTZITE Exposures of quartzite-pebble conglomerate cemented with 3ilica are present near the top of the formation. Upper 5-10 ft includes medium gray (N5), well-sorted quartz arenites that form a dipslope. 250 APPENDIX B Distribution and frequency of conodont3 Appendix B contains sample by sample elemental frequency of conodont species from the 3even localities listed in Figure 2. Sample numbers are located across the top of each table. Each sample number includes the locality designation (e.g. 83LA, 85LT, PHC) and, except for PHC, the stratigraphic distance in feet above the base of the section. Sample numbers for PHC include Anita Harris' (USGS) locality information (i.e. 8-9-75A, 8-9-75B, etc.) and the computed distance in meters from the base of the section. 250 TABLE 7.— Elemental frequency of conodont species from 83LA. Q3Lfl Lakasid* Kts. 83LB 03LA S3LB B3Lfl B3LR BSLfl 63LA 8XA 63LR B3L0 B3LF) B3Lfl S3Lft 83Lfl B3Lfl 03LH 83LR BSLfl Q3LH B3LR B3LD &3LR B3Lfl 03LO 63LR S3U) 83U» 03LR 03Lfl SPECIES 45 60 73 7S 90 IDS 120 135 150 165 180 195 243 253 270 285 300 315 330 345 360 375 405 420 435 450 465 400 495 T0TOL Rphalo^vilKis divargarts 50 r 50 Pphalogrutlus Flowari 122 c 24 13 2 161 Hphalog’tathus she tzar i 2 27 29 Rphalngnathia? sp. oF Suttt (1979) 2 2 flfhalognethu* *pp. 3 3 2 1 12 6 3 2 1 1 2 40 Balodins celclproainens 1 2 2 I 6 Balodine canfluens 5 4 9 Balodine sp. 1 1 1 3 Cwluabodlne occidentalis 5 5 Orapanoistodus subvrsctus 14 7 I 3 15 4 5 3 Icriodalla sp. 1 2 1 17 74 New Gems n.sp. f) of Laathe* (1994) 1 1 Oulodus ulrichi S 2 1 2 1 3 to 7 1 12 44 Pandtrodus frulneri sansu Sweet (1979) 18 26 IS 9 10 3 3 4 3 1 10 25 66 7 47 lie £ 2 4 3 1 17 26 432 Pandrrodus pander-i 1 2 2 2 1 16 6 31 Panderodus spp. IS e G 6 1 - 3 6 2 14 1 to 1 1 74 PlecIodine eculaetoidas 1 PI acted in* Florida 8 Plectodine sp. 8 PlecIodine tenuis 14 2 Plegagnathitf dartoni 62 83 Plegegnattss nelson! 2 Pristo^uthus? rohrwri 8 PseudobeIodine edentate 5 Pscudobelodtne dispense 10 Pseudobvlodina Icirki B Pseudobelodine quadrate 5 Psvudob* Iodine vulgaris utttsa 42 Fsaudob*Iodine vulgaris vulgaris 13 tthipidognethus sywetricus 50 74 SbeuFferalle brevispinabe 1 Halliserodus aaplissiaus 4 indet. alat—nts 2 indet. platfora c-lonant* 6 TOTPLS " 92 68 31 19 26 1 159 72 217 U 55 243 16 21 12 47 57 1199 uiro TABLE 8.— Elemental frequency of conodont species from 83LB. OXU Silwr Ultnd nil. <» B3LB aXD B3LB 8X0 6X0 BXB B3LQ BXB BXB 8X6 8X3 BXB 8XB B3A 8X0 QXB BXB 6X0 6X0 0X0 6X6 BXB BXB 8X0 8X9 0XB BXQ QXB 8XB 6XB Torn. SPECIES 0 IS 30 45 GO 75 90 105 120 135 ISO 165 100 195 210 225 240 270 295 300 315 330 345 420 435 450 460 465 470 475 l>*pfwlo9ruthM9 diw f'grn* 6 35 9 10 42 icrj riD «4m S 4 2 I 1 13 TOTfXS S3 23 40 400 935 235 23 51 33 5 1 20 29 44 41 26 99 13 12 11 31 B 10 26 111 1 1 2290 TABLE 9.— Elemental frequency of conodont species from 83LC. B3LC Lone Hountain B3LC B3LC 83LC 83LC 83LC 83LC 83LC 83LC 83LC 83LC B3LC 83LC B3LC 83LC 83LC B3LC B3LC 03LCTOTRL SPECIES 0 IS 30 45 60 75 90 105 120 135 150 160 165 170 180 190 195 200 I Raorphognathus ordovicicus 1 13 8 2 2 Belodina conFluens 6 4 1 11 Belodina sp. 1 1 Belodina stonei 2 9 3 4 3 6 Culumbodina occidental is 7 7 Culumbodina penna 6 6 Orepano istodus suberectus 14 19 13 3 4 4 4 3 5 36 1 2 ? 133 I Gaoachignathus ensifer 12 12 I Icriodella sp. 1 1 I *0istodus* venustus 2 1 3 1 7 I Gulodus sp. 1 1 | Oulodus ulrichi 2 6 10 I 37 J Panderodus feulneri sensu Sweet (1979) 165 192 78 46 130 6 2 121 9 6 5 0 17 4 74 14 6 8 I 1 1065 Panderodus spp. 6 0 3 0 4 13 18 11 14 19 17 14 ' 29 2 3 7 Phragmodus undatus 5 3 1 2 I 12 Plectodina florida 1 3 1 2 7 Plectodina sp. 3 3 Plectodina tenuis 3 4 0 43 Pristognathus? rohneri 12 2 14 Pro to panderodus insculptus 3 6 14 11 16 11 5 5 1 7 2 Pseudobelodina dispansa 4 5 2 1 2 14 1 Pseudobelodina inelinata 4 4 [ Pseudobelodina kirki 8 1 9 J Pseudobelodina vulgaris vulgaris 1 1 2 1 Pseudooneotodus nitratus 1 3 2 3 3 1 1 14 | Pseudooneotodus sp.aff. P. nitratus 1 1 Pseudooneotodus becknami 1 1 1 3 Scabbardella altipes 4 0 11 7 7 8 14 18 10 1 116 StauFFerella sp. a 3 1 1 13 H alliserodus amplissimus 2 5 179 B3 3 2 0 441 193 334 108 3 9 9 5 3 1 1821 indet. elements 2 1 3 TOTRL 3 3 8 5 0 3 2 1 6 4 0 6 6 2 2 2 9 4 4 9 5 2 5 5 149 1 8 2 6 155 81 14 8 2 1 3 7 2 7 253 TABLE 10.— Elemental frequency of conodont species from 83LD. 93LD liars Canyon (Antelope U«1 lry Liarstone Gi ana Limestone Ruber ts fits. Fa. 83LQ- B3LD- 63L0- 83LD- 8X0- Q3LD- B3LD- B3L0- B3.0- 03LO- B3L0- 03LO- DinHR SPECIES 090 095 105 120C 12QM 135 150C 150W 155 160 Qlt 165 TOTRLS neorphognathua ordovicicus 1 t Rear ptagna thus sp. 19 6 1 5 1 5 37 Bnw] h jemtlandica 22 5 2 2 9 *Bryantodina* sp. 1 I Coleodus? sp. 1 I 1 Oapsilodus mubatus 1 1 1 3 Oapsilodus obliquieosbatu* 15 7 1 22 Orepanoistodus angulensis 9 12 2 2 2 6 Orrpaooistodu* sp. 1 1 GenachignatKis sp? 1 1 Histiodello n.sp. 2 oF Karris at el. <1979) 62 127 6 3 9 Histiodella sp. 2 0 Icriodella sp? 1 1 Juanognathus serpeglii I 2 0 Naonulbioistedus ctypeu* 1 1 HeoMjlfeioistodus sp. 2 5 a Hoixodontu* girardeauensis 2 1 1 4 Oepikodus sp. 3 3 0 •flislotodus" venustus 1 3 4 Oistodus sinuosu? 3 0 Oistodus sp.cF. 0. tab lepo in teres is 1 1 Oistodus sp. R 5 t 1 1 Oulodus sp. II 1 Ozarkodina exeevata 44 at 16 125 Ozarkodina hadra 7 7 Ozarkodina has? i 3 7 10 Ozarkodina sp. A of ttamik (1983) 1 1 Ozarkodina sp. 3 3 Panderodus sp. 1 1 Perioden sp.cf. P. grandis 4 1 1 3 9 Folyplaeognathus remoaus 3 3 Pravognathus sp. * 1 8 1 Protopanderodu* inseulptus 0 I G Protopanderodus liripipu* 2 S 2 Probopanderodus sp. 1 II 1 Pseudooneotodus bicomis 4 6 0 10 Pseudooneotodus sp.aFf. P. mitratus 1 1 1 Pteeaeontiodus crypbodens 1? 66 11 1 1 12 Ptecoapathodus sp.aFF. P. posteeobenuis 1 t 1 Pierospetbodos sp. 1 1 5 1 7 Pygodus enseeinus 1 I 1 Pygodus sp. 1 fi 1 Seandodus sinuosus 4 Ualliserodus sp. 2 j)i °2 Genus et sp. indet 0 2 0 indeb. actxliForm element ' 1 1 indet. conifora elements 1 1 indet. oistodontifora elements 2 G I 1 indet. platform processes 1 9 1 11 TOTALS 121 251 44 11 2 25 21 20 74 100 27 10 324 TABLE 11.— Elemental frequency of conodont species from 83LE. B3L£ S m th Cgw SPECIES 0 15 30 45 75 90 ICS 135 150 165 100 195 210 225 240 255 270 2SS 300 315 330 344 360 375 390 405 420 430 450 465 470 471 fWrp>M/u th « orttovicieu* 2 RphalognatHrt divargms SO RphaloguDvs *K*txvri 13 Belodina conFloan* is 36 27 12 93 Balodin* sp. 1 2 Belodina atonei 9 Coalocarodontua Lriganiua 6 3 9 4 2 9 5 50 Culuatadina ocdidenLalis 8 3 7 11 29 Culkabadina p im 9 5 14 Qrepanoiitadus subersetus 51 89 48 05 92 50 10 11 3 25 40 19 24 30 44 27 11 9 9 4 2 11 29 7B« HtM Cerus ru sp . fl eF L rathan <1904) 1 1 "Qietodua* verustus 2 4 1 1 2 10 Oulodus ulrtehi 60 40 1 14 17 B 2 1 2 3 4 I 25 6 5 10 3 6 36 260 Panderodus Fetilneri srrrtu Suaet <1979) 302 203 205 349 320 308 105 47 8 122 36 so 22 50 44 27 56 24 16 25 16 11 12 B 2467 Panderodus pander i 19 11 4 6 2 6 6 4 4 3 4 1 I I 4 76 Paraferodus spp. tco Bfi 13 59 33 65 41 21 37 17 25 4 4 6 1 2 5 4 *1 I 1 544 Parabetodina denfcicutata 1 1 Riragaodu* undatus 20 3 546 SO 25 2 17 56 719 Plectodina scuUatoidrs 2 14 Plectodina Florida IB 20 4 12 15 15 6 10 9 9 4 IS 7 13 9 175 Plectodina sp, 4 Plectodina tiruli S t 132 35 too 43 56 15 53 107 70 21 66 21 25 21 15 919 Piegegruthux dartoni 3 PlegagnjUxr* nelaani 1 2 1 10 Pristog%athus big^w rw eis I 1 Prirtogulhjt? rohrsrt so Pro top* dwudus Insculptus 27 18 6 52 P*euicbe Iodine dispense 20 34 12 19 115 PscuJabe Iodine incUrvite 19 16 14 90 Psaudobelodina kirkj 31 22 89 Pseudobelodina torta 2 7 16 Pseudobelodina vulqari# ultiM 1 Pseufabetodine vulgaris vulgaris 21 Pseudooneotodus back*ami 20 Pseudooneotodus aitratu* 45 Pseudooneotodus sp.aFF. P. becknami 2 DiipidogruUvj* sgaaetrieus 27 5cabbariiella altipas 44 13 22 13 25 26 3 11 I 159 5tauFFer«lla brevispirwta •I 11 Stauffers He 1 trdstroeai. 20 19 1 9 6 55 StauFFaralla tp. 5 Uallisarodus aaplisiiaus 10 13 7 3 4 17 1 It 16 95 indet. plstFora eleaenta TOTALS 723 771 403 761 595 1217 325 221 41 307 279 194 Q7 101 140 122 132 13 11 48 49 49 88 48 16 63 75 Z2 255 TABLE 12.-—Elemental frequency of conodont species from 83LF. B3LF Hills SPECIES c 15 30 43 CO T i 90 105 ISO 125 150 163 100 195 210 223 240 255 270 2BS 300 315 330 345 X O 375 3 W 405 42? 435 440 465 40Q 495 SIQ 323 S29 d i *»< y w 49 13 21 100 At^wle^wtKa riduvri 24 60 fahslogrutfus s*ut4*rai 1 3 6 10 P p+wla^utHjs sp. 13 6 42 Bslodin* ston«l 1 2 3 Op«p«n0iit(dn iub»ftctut 79 30 4 2 3 1 16 1 2 5 6 162 *0lllodu|* VTIVslut 1 1 OuloAjs wlrichi 05 33 27 2 3 3 * 19 2 1 170 P^sto-wt* fvulrwri m w S m L <1979) 69 37 16 1 14 17 11 2 7 2 2 7 4 15 2 2 2 3 277 Pvdsrafc** spp. to 3 5 2 II 7 2 t 3 11 99 Pl*Ct«din« SCuUltmd** 6 5 11 P|#etodin* s p . 21 2 23 P|«locJJri* to'vif 2B 23 52 Pl^tf^U vt n*lfcni 1 I 4 Pwudet»lttdin» sd*rtt*ta 9 Pw uU slidlni birfri 4 4 PssuMwlodins 5 P|* B5LT Toano Hang* BSLT S 3.T 8SLT 8SLT Q5LT B5LT BSLT B5LT BSLT 8SLT 85LT 0SLT 85LT QSLT B5LT SSl T QSLT 05LT BSLT 85LT 85LT e a r 6SLT BSLT 85LT BSLT 8 9 .T 65L.T 8SLT BSLT 6SLT TQTFL SPECIES 0 IB 30 47 60 75 SO 105 120 135 150 IBS 195 210 225 240 2SS 270 300 315 325 330 345 4OS 421) 435 45U 465 400 495 510 PphslogrutSj* di»try n s 116 Pptwlogruthus sp. 1 Bslodiru canFlum* 31 S3 Bslodin* sp* 5 B+lodift* stonsi 3 Costacsrodantizs trigonius 1 CuliMbadins occidffitslis 32 Cutuibodin* p*nn# 14 Orcfunoistodus subartctus 4 57 50 52 16 3 3 6 S 16 3 I t 263 11 20 6 1 1 • 1 2 1 1 6— chi y n thus •rtsifsr 5 24 2 1 32 Oulodus ulrichi 4 35 17 29 17 11 3 1 6 t 126 Psndf odus Feu 1 net* i ssnsu 5u*tt <1979) S 240 116 1S9 30 3S 66 9 4 e 35 37 0 12 11 9 3 4 4 2 2 619 RjraJerodu* pandsri 6 9 6 3 1 t 1 4 1 32 POTd«rod*s spp* 37 19 42 2 4 6 2 i 6 1 4 3 2 4 3 1 137 Plfdodiru K ultitoidn 2 8 35 31 94 Plfctodins flor*id* 4 IS 21 21 IS 19 2 97 Plrctodiiu sp. 14 3 3 2 1 1 1 25 Plsctodirv* trrulf 3 9 17 10 31 6 103 Plv^uU ius rwlsoni 2 Pltgayvilhus sp* 1 Priftognlhus? rohneri 7 Protcpandvrodus sp. 4 4 Pseudobslcdins adaittaLa 1 Psmdobslodins dj spans* 7 2 19 34 Ptaudobvlodina inctinsLa 3 Psaudobslodina kirfci 12 4 14 42 pMudobelodin* to rtl 2 Pssudobslodirw vulgjris ultimo 1 Psaudobslodlna vulgari* vulgarjs 1 4 4 ID Paaudoanaotodus *itr*tui S 2 7 Phipidogrtattu* syeestricus 15 5cjbhird»H< a lt i p v * 2 5taufF*r*lla brrvi*pirv»t* 5 StsufF«r*41s sp, 1 7 Ujlljssroditt «*plisslsu* IB IB ind*U •!» nts TOTAL 60 501 278 414 104 96 136 2 147 46 12 23 33 12 23 56 2119 7 5 2 TABLE 14.— Elemental frequency of conodont species from PHC. PMC (B-9-75) Pete Hanson Creek R 0 C D E F G H TOTRL SPECIES 0 9 2 2 3 9 5 7 7 3 91 1 1 0 Rmorphognathus ordovicicus 1 1 2 Belodina conFluens 7 1 • 8 Belodina sp. 1 1 Belodina stonei 6 6 Coelocerodontus trigonius 1 4 3 0 Culumbodina occidental is 1 S 6 Culumbodina penna 1 1 Culumbodina sp. 16 1 17 dapsilodiForm elements 10 2 5 4 3 Dapsilodus m utatus 4 4 Orepanoistodus suberectus 6 6 2 4 31 2 6 5 16 4 1 5 4 "Qistodus" venustus 0 1 9 Oulodus ulrichi 4 1 3 1 7 Ozarkodina sp. 4 4 Panderodus feulneri sensu Sueet <1979) 2 0 2 2 6 9 2 5 2 4 5 2 0 Panderodus panderi 7 1 3 1 1 2 2 4 Panderodus spp. 3 4 1 1 8 6 4 0 2 2 2 6 5 4 3 Phragmodus undatus 3 3 Plectodina florida 6 6 Plectodina sp. 2 4 1 7 Plectodina tenuis 7 8 1 0 2 5 Plegagnathus nelsoni 1 1 Pristognathus? rohneri 7 1 2 1 2 3 1 Protopanderodus insculptus 4 4 Protopanderodus liripipus B 8 Pseudobelodina dispansa 8 6 2 3 1 3 8 Pseudobelodina inclinata 7 16 2 3 Pseudobelodina kirki 0 Pseudooneotodus beckmanni 2 . 1 3 Pseudooneotodus m itratus 7 8 1 5 Scabbardella altipes 24 4 0 1 6 5 StauFFerella sp. 2 2 4 Halliserodus amplissimus 25 1 6 2 3 5 5 1 TOTRL 7 3 6 6 2 9 7 9 4 1 3 14 9B 7 0 16 5 1 258