Upper Cambrian-Lower Ordovician Notch Peak Formation in Western Utah

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1393

^^ M Upper Cambrian-Lower Ordovician Notch Peak Formation in Western Utah

By LEHI F. HINTZE, Brigham Young University, MICHAEL E. TAYLOR, U.S. Geological Survey, and JAMES F. MILLER, Southwest Missouri State University

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1393

Lithostratigraphy, biostratigraphy, and regional correlations of the Notch Peak Formation and descriptions of three new members

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1988 DEPARTMENT OF THE INTERIOR

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY

Dallas L. Peck, Director

Library of Congress Cataloging-in-Publication Data

Hintze, Lehi F. Upper Cambrian-Lower Ordovician Notch Peak Formation in western Utah. (U.S. Geological Survey professional paper ; 1393) "Lithostratigraphy, biostratigraphy, and regional correlations of the Notch Peak Formation and descriptions of three new members." Bibliography: p. Includes index. Supt. of Docs, no.: I 19.16:1393 1. Geology, Stratigraphic Cambrian. 2. Geology, Stratigraphic Ordovician. 3. Geology Utah. I. Taylor, Michael E. II. Miller, James Frederick, 1943- . III. Title. IV. Series: Geological Survey professional paper ; 1393. QE656.H56 1987 551.7'23 86-600020

For sale by the Books and Open-File Reports Section U.S. Geological Survey Federal Center Box 25425 Denver, CO 80225 CONTENTS

Page Page Abstract ...... 1 Measured sections of the Notch Peak Formation ...... 20 Introduction ...... 1 Type section of the Notch Peak Formation, House Range, Acknowledgments ...... 1 Utah ...... 20 Notch Peak Formation boundaries ...... 2 Reference sections of the Notch Peak Formation ..... 21 Age of the Notch Peak Formation ...... 2 Principal reference section of the Notch Peak Forma­ Members of the Notch Peak Formation ...... 4 tion and the type sections for its Hellnmaria, Red Hellnmaria Member (new) ...... 4 Tops, and Lava Dam Members ...... 21 Red Tops Member (new) ...... 6 Steamboat Pass-Lava Dam section, southern House Lava Dam Member (new) ...... 6 Range, Utah ...... 23 Notch Peak Formation correlatives in Utah and Nevada 7 Lawson Cove section, Wah Wah Mountains, Utah . 26 Biostratigraphy ...... Fish Springs Range section, Utah ...... 28 Conodonts ...... References cited ...... 29 Trilobites ...... 16

ILLUSTRATIONS

PLATE 1. Ranges of conodonts, trilobites, and some other fossils in the Notch Peak Formation and lower part of the House Limestone in the Steamboat Pass-Lava Dam section, southern House Range, Utah ...... In Pocket

Page FIGURE 1. Map showing location of stratigraphic sections discussed in text and shown on figures 2 and 3 ...... 2 2. Chart showing correlation of the Notch Peak Formation with units in adjacent areas ...... 3 3. Columnar sections of the Notch Peak Formation described herein under "Measured Sections" ...... 5 4. Chart showing correlation of conodont and trilobite zones and subzones with the Notch Peak Formation ...... 7 5. Chart showing ranges of conodonts in the principal reference section of the Notch Peak Formation, central House Range, Utah ...... 9 6. Correlation chart of lithostratigraphic and some conodont biostratigraphic units between the Steamboat Pass-Lava Dam section and principal reference section of the Notch Peak Formation ...... 16 7-11. Maps showing: 7. Location of principal reference section of the Notch Peak Formation in the central House Range, Utah . 21 8. Location of the Steamboat Pass-Lava Dam section, southern House Range, Utah ...... 23 9. Geology of area in the vicinity of the principal reference section of the Lava Dam Member of the Notch Peak Formation ...... 24 10. Location of the Lawson Cove section, Wah Wah Mountains, Utah ...... 26 11. Location of the Fish Springs Range section, Utah ...... 28

TABLES

Page TABLE 1. Conodont distribution in the principal reference section of the Notch Peak Formation and lower House Limestone, central House Range, Utah ...... 10 2. Conodont distribution in the Notch Peak Formation in the Steamboat Pass segment of the Steamboat Pass-Lava Dam section, southern House Range, Utah ...... 12 3. Conodont distribution in the Notch Peak Formation and lower House Limestone in the Lava Dam segment of the Steamboat Pass-Lava Dam section, southern House Range, Utah ...... 14 4. Occurrences of trilobites and some other fossils in the Steamboat Pass-Lava Dam section of the Notch Peak and House Formations ...... 18

UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

By LEHI F. HiNTZE, 1 MICHAEL E. TAYLOR,2 and JAMES F. MILLER3

ABSTRACT seems clear, but certain aspects of the definition are am­ biguous enough to have created problems for later Three mappable members in the Notch Peak Formation in western stratigraphers and geologic mappers. First, Walcott Utah are recognized, named, and defined. In ascending order, these did not indicate a stratigraphic top to the formation. are the Hellnmaria, Red Tops, and Lava Dam Members. All members are limestone or dolomite; the Red Tops consists of thin-bedded Second, Walcott did not identify the location of his bioclastic lime grainstone, whereas the other members are more measured section precisely enough to enable it to be massive, finer textured, and include many high-relief hemispherical retraced. Third, the Ordovician age assignment that stromatolites. The formation ranges from a maximum thickness of Walcott made for fossils collected on the summit of 557 meters (m) in the Wah Wah Mountains at the south edge of the area studied to 368 m in the Fish Springs Range at the north edge. Notch Peak is incorrect. Geologic mapping by Hintze Trilobites representing the Taenicephalus and Idahoia Zones of the (1974a-e) has traced the formation in the House and Franconian Stage have been obtained from the Hellnmaria Member. Confusion Ranges and the Wah Wah Mountains in The Red Tops Member contains trilobites of the Trempealeauan western Utah (fig. 1) and has delineated three mappa­ Saukiella junta Subzone of the Saukia Zone; the Lava Dam Member ble members there. This paper defines these members, contains faunas of the Trempealeauan Saukiella serotina andEurekia apopsis Subzones of the Saukia Zone, the Lower Ordovician Missis- describes them in type sections and other reference sec­ quoia depressa and Missisquoia typicalis Subzones of the Missisquoia tions, and documents the biostratigraphic control on Zone and the Symphysurina brevispicata Subzone of the Sym- their ages. physurina Zone. Two conodont zones and seven subzones have been recognized in the Red Tops and Lava Dam Members of the Notch Peak Formation. The Proconodontus muelleri and Eoconodontus notchpeakensis Sub- ACKNOWLEDGMENTS zones of the Proconodontus Zone correspond approximately to the Saukiella junia trilobite Subzone in the Red Tops Member. The Cam- brooistodus minutus Subzone of the Proconodontus Zone correlates This study is an outgrowth of a geologic mapping pro­ approximately to the Saukiella serotina Subzone in the lower part of gram in western Utah conducted by L. F. Hintze under the Lava Dam Member. The Hirsutodontus hirsutus Subzone of the the cooperative auspicies of Brigham Young Universi­ Cordylodus proavus Zone corresponds to the Eurekia apopsis Sub- ty, the Utah Geological and Mineral Survey, and the zone and the overlying Missisquoia depressa Subzone. The Fryx- ellodontus inornatus and Clavohamulus elongatus Subzones of the U.S. Geological Survey. Trilobite studies by M. E. Cordylodus proavus Zone correspond approximately to the range of Taylor were supported by Geological Society of America the Missisquoia typicalis Subzone. The Hirsutodontus simplex and grants 1082-66 and 1221-69 and by the U.S. Geological Clavohamulus hintzei Subzones of the Cordylodus proavus Zone cor­ Survey after 1969. National Science Foundation grants respond to the lower part of the Symphysurina Zone in the uppermost to D. L. Clark supported J. F. Miller's conodont studies part of the Lava Dam Member and the lowermost part of the overly­ ing House Limestone. from 1965-70. Additional grants to J. F. Miller were from the Geological Society of America, Society of Sigma Xi, Research Corporation, University of Utah INTRODUCTION Faculty Research Committee, and Southwest Missouri State University Faculty Research Committee. We ex­ The Notch Peak Formation is the uppermost of sev­ press appreciation to Donald McMillan, former Direc­ eral Cambrian formations named by Walcott (1908a,b) tor of the Utah Geological and Mineral Survey, for his in the House Range. The intent of Walcott's definition interest in and support of the program, and to M. D. Crittenden, Jr., R. K. Hose, H. T. Morris, and G. W.

'Department of Geology, Brigham Young University, Provo, Utah 84602 Walker of the U.S. Geological Survey for their en­ 2U.S. Geological Survey, Box 25046, MS 919, Denver Federal Center, Denver, Colorado couragement and help with various aspects of this 80225 study. J. R. Derby is thanked for allowing us to incor­ 3Geosciences Department, Southwest Missouri State University, Springfield, Missouri 65804-0089 porate into the study some fossils that he collected. l UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

114° 112° 110° was not delineated by Walcott (1908a,b) because his

IDAHO 1 measured section ended with the uppermost beds ex­ posed on the summit of Notch Peak. Hintze (1951, p. 12) defined the top of the Notch Peak Formation in the I ~ 1 WYOMING y ( Great Salt House Range by formally recognizing the Ordovician 1 S M p~ Lafce House Limestone as the stratigraphic unit immediate­ ly overlying the "more massive Notch Peak Lime­ stone." Hintze designated a locality on the south flank ^Aj) Q SALT LAKE CITY of Notch Peak (see Hintze, 1973, for locality map) as ^ Sheeprock the type locality for the House Limestone. The geologic | Deep Creek Mountains contacts shown on the map of the Notch Peak quad­ 40° W 9 Range j 0 Best Tintic Mountains COLOR/' rangle (Hintze, 1974a) are in accordance with Hintze's Dugway Range definition of the Notch Peak-House formational contact. Fish Springs Range It should be noted that Whitebread (1969) did not follow O Hintze's (1951) usage of the Notch Peak-House bound­ O Snake 'Sneakover Pass, House Renge ary but extended the House Limestone down to include Range 9 \ Southern House Range Cambrian beds possibly equivalent to the upper 1 ^j*Lawson Cove members of the Notch Peak Formation as shown on Weh Wah Mountains 1 figure 2. 38° _ UTAH 1 Dashed outline shows fve 15-mmute ' quadrangles where members of the AGE OF THE NOTCH PEAK FORMATION 1 Notch Peak Formation have been 1 1 mapped by Hintze 11974, a-e) 1 Walcott (1908b, p. 173) stated that the summit of ~ ~ ~ ~ ARIZONA 1 Notch Peak "is formed of 285 feet of Ordovician !i I i ! Limestone...containing near the top a distinct fauna: 0 50 100 KILOMETERS I I Obolus (Westonia) notchensis Walcott I 0 50 MILES Eoorthis coloradoensis (Meek) Raphistoma sp. etc." FIGURE 1. Location of stratigraphic sections discussed in text and We have recollected from the uppermost beds on the shown in figures 2 and 3. summit and identified the following taxa: Bayfieldia n. sp. NOTCH PEAK FORMATION BOUNDARIES Bowmania sp. Euptychaspis sp. indet. The base of the Notch Peak Formation was placed by KeithiellaCl) sp. Walcott (1908a,b) at its contact with the Orr Forma­ Prosaukia sp. or Saukiella sp. tion on Orr Ridge. Hintze and Palmer (1976, p. G8) high-spired gastropod, gen. and sp. indet. redescribed the Orr Formation at Walcott's type local­ echinodermal debris ity in the central House Range and noted that the up­ linguloid brachiopod, gen. and sp. undet. permost member of the Orr, the Sneakover Limestone orthoid brachiopod, gen. and sp. undet. Member, was included within the Notch Peak Forma­ This fauna can be assigned to either the Saukiella tion on geologic maps by Powell (1959), Hanks (1962), junta or Saukiella serotina Subzone of the Saukia Zone, and Whitebread (1969). Geologic maps by Hintze Trempealeauan Stage. Thus, the beds on the top of the (1974a-e) place the Orr-Notch Peak contact at the peak are now regarded as Cambrian rather than Ordovi­ horizon originally designated by Walcott. This contact cian as indicated by Walcott. The geologic map (Hint­ can be readily recognized because the Sneakover ze, 1974a) shows that the summit of Notch Peak is made Limestone Member is somewhat silty and medium to up of strata here designated as the Red Tops Member thick bedded and forms ledges, whereas the massive of the Notch Peak Formation. The strata above the Red basal carbonates of the Notch Peak Formation form Tops Member, herein called the Lava Dam Member, cliffs. Also the Sneakover Limestone Member contains were never discussed by Walcott. They are included phosphatic brachiopods and trilobite fragments, within the Notch Peak Formation because of Hintze's whereas the lower Notch Peak carbonates are nearly (1951) defining the top of the Notch Peak Formation barren of shelly fossils. as the beds beneath the House Limestone. Hintze (1951) The stratigraphic top of the Notch Peak Formation thought that the Cambrian-Ordovician boundary was U P PER CAMBRIAN LOWER FRANCONIAN STAGE TREMPEALEAUAN STAGE ORDOVICIAN

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m H Ajax Dolomite 1 -n gLimestone Opohonga f 0 3 CD C | If Member Emerald T3 ^. X 3 T3 o CT CD M V) m H S UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH approximately at his Notch Peak-House formational HELLNMARIA MEMBER (NEW) contact. Subsequent work by Miller (1969) and Taylor (1971) suggested that the upper 30 m of the Lava Dam The basal member of the Notch Peak Formation Member of the Notch Peak Formation as used by Hintze derives its name from HelTn Maria Canyon located in (1951; 1974a-e) includes trilobites of the Missisquoia sees. 25, 35, 36, T. 19 S., sees. 3 and 4, T. 20 S., R. 14 Zone and a conodont assemblage that is generally re­ W., about 5 km (kilometers) south of Notch Peak in the garded in North America as lowermost Ordovician House Range and shown on the 1960 edition of the (Taylor and Halley, 1974; Landing and others, 1978; Notch Peak 15-minute topographic quadrangle. The Miller, 1978, 1980; Miller and others, 1982). The Helln- geographic name part of the geologic name has been maria Member has yielded a few trilobites that are condensed to one word (Hintze, 1973, 1974a-d). The assigned to the Franconian Taenicephalus and Idahoia type section is located in the House Range about 10 km Zones. However, the upper part of the member has not southeast of Notch Peak as described in detail under yielded diagnostic fossils so that the position of the "Measured Sections." The Hellnmaria Member is char­ boundary between the Franconian and Trempealeauan acteristically a chert-bearing limestone or dolomite that Stages is unknown. forms massive cliffs and ledges. In its type section in The Red 1bps and Lava Dam Members have yielded the House Range the member is entirely limestone; in an abundance of conodonts and trilobites permitting the Fish Springs Range the same interval is almost en­ rather precise zonation of the upper part of the Notch tirely dolomite (compare columns, fig. 3), and in other Peak Formation. Thus, as indicated on figure 2 and areas it is partly limestone and partly dolomite. discussed in greater detail under the section on "Bio- Whether differences are a result of original depositional stratigraphy," the Notch Peak Formation includes fossils facies differences or post-depositional dolomitization is ranging from upper Franconian, Trempealeauan, to the not known. Lower Ordovician Missisquoia Zone and lowermost The Hellnmaria Member has been subdivided on The Symphysurina Zone. Barn quadrangle geologic map (Hintze, 1974b) into three map units on the basis of locally traceable varia­ tions in lithology, color, and topographic expression; the MEMBERS OF THE lower map unit of The Barn subdivisions can be ex­ NOTCH PEAK FORMATION tended southward into the Wah Wah Summit quad­ rangle (Hintze, 1974e) as well. None of these map units The Notch Peak Formation is entirely limestone and can be recognized to the north in the Notch Peak dolomite and characteristically forms high resistant quadrangle (Hintze, 1974a) or in the Fish Springs Range cliffs that constitute the backbone of several mountain (Hintze, 1980a,b). ranges in western Utah. Within the House Range and Biostratigraphically significant fossils are rare in the northern Wah Wah Mountains, the Notch Peak Forma­ Hellnmaria Member. Miller (1969, p. 415) reported that tion can be divided into three mappable members samples taken from the Steamboat Pass-Lava Dam sec­ (Hintze, 1974a-e) based on the occurrence of a bioclastic tion of the Hellnmaria Member (Miller's members 2, 3, lime grains tone sequence, the Red 1bps Member, near and 4 are equivalent to the Hellnmaria Member) yielded the middle of the formation. This member can be easily only rare, undiagnostic conodonts. Trilobites are also traced in the field and on aerial photographs because rare in the Hellnmaria Member. A fauna assigned to the it is thinly bedded and forms benches, slopes, and low upper Franconian Taenicephalus Zone was collected ledges in contrast to the more resistant cliff-forming (USGS locality D2831-CO) 20 m above the base of the members above and below. In addition, the Red 1bps Hellnmaria Member in the Steamboat Pass-Lava Dam Member weathers light brown in contrast to the typical­ section. Faunas of approximately the same age occur ly drab grays of the other two members of the forma­ in the underlying Sneakover Limestone Member of the tion. Where the Red 1bps Member is absent, as in the Orr Formation (Hintze and Palmer, 1976, p. G10). An Fish Springs Range (fig. 3), the Notch Peak Formation assemblage (USGS locality 8343-CO) assigned to the has not been subdivided. upper Franconian Idahoia Zone was collected from an The principal reference section of the Notch Peak For­ unknown horizon in the Hellnmaria Member near U.S. mation is here established in the House Range in Ts. 19 Highway 50, about 7.8 km east of Skull Rock Pass, cen­ and 20 S., R. 13 W, Notch Peak, Utah quadrangle, as tral House Range. discussed under "Measured Sections." In addition, three The polyplacophoran mollusk Matthevia (Yochelson, reference sections are described in order to show the var­ 1966; Runnegar and others, 1979) is common in the mid­ iations in lithology and fossil content embraced under dle map unit of the Hellnmaria Member in the southern the present definition of the Notch Peak Formation. House Range. There, Matthevia is usually coarsely MEMBERS OF THE NOTCH PEAK FORMATION

Southern House Range, House Range, Wah Wah Mountains, Steamboat Pass to Sneakover Pass Fish Springs Range, Lawson Cove Red Tops to Little Valley Hill 6559 House Eroded EXPLANATION

Limestone

Dolomite

Intraformational conglomerate

Calcarenite

Oolites or pisolites

Stromatolites

Chert

FOSSIL HORIZON SYMBOLS Conodont collection (Miller, 1969} Symphysurina trilobite assemblage Missisquoia trilobite assemblage Eurekia apopsis trilobite assemblage Saukietla serotina trilobite assemblage Saukietla junta trilobite assemblage Mattheuia (mollusc) occurrence Matherella (gastropod) occurrence Idahoia trilobite assemblage Taenicephalus trilobite assemblage Elvinia trilobite assemblage

METERS FEET 100-) 90- -300 80- 70- 60- -200 50- 40- 30 -100 20

SALT LAKE CITY UTAH

House Range j A! Southern House Range l-iWah Wen Mountains

Dashad ouilina shows fiva 15-minuta quadrangles whara mamberi of Notch Peak Formation hava been mapped by Hintza (1974 a-a)

FIGURE 3. Columnar sections of the Notch Peak Formation described herein under "Measured Sections." 6 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH silicified and occurs commonly in association with the groundwater activity during Tertiary or Quaternary gastropod Matherella. The occurrences ofMatthevia are time (Taylor and Glanzman, 1979). strongly facies-controlled and are usually associated The Red Tops Member is found throughout the House with shoal-water carbonate environments that contain Range. Within the Wah Wah Mountains it thins rapid­ abundant high-relief stromatolites (Yochelson and ly to the southwest, diminishing to half its ordinary Taylor, 1974; Runnegar and others, 1979). Where in­ thickness in the House Range. The Red Tops Member dependent biostratigraphic data are available, Mat- does not occur in the Fish Springs Range. Whether it thevia is of early Trempealeauan age. Some occurrences is represented there by dolomite or whether it has been lack associated trilobites and could be as old as late eroded by pre-House Limestone beveling on the flank Franconian (Runnegar and others, 1979). of the Tooele Arch (Hintze, 1973a) is not certain. Stromatolites were recognized as an important part Conodonts from the Red Tops Member were de­ of the Notch Peak Formation by Hose (1961), who il­ scribed by Miller (1969), who identified the Red Tops lustrated some examples. Similar stromatolites have as member five in his measured sections. The Pro- been described by Taylor and Cook (1976) from the conodontus muelleri, Eoconodontus notchpeakensis, Whipple Cave Formation of Kellogg (1963) in eastern and lower part of the Cambrooistodus minutus Sub- Nevada and by Campbell (1976) from the Trempeale­ zones of the Proconodontus Zone, of middle Trempeale­ auan Dotsero Formation in western Colorado. Figure auan age, have been identified in the Red Tops Member 3 shows that stromatolites are common in the upper half (fig. 4 this paper; Miller, 1978). The faunas are discussed of the Hellnmaria Member in the House Range and Wah more thoroughly in the section on "Biostratigraphy" Wah Mountains; they are virtually absent in the Fish and by Miller and others (1982). Springs Range. Stromatolites are useful as indicators Trilobite faunas from the Red Tops Member are of peritidal environments, although they have not been assigned to the Saukiella junta Subzone of the Saukia found to be definitive time markers in the Great Basin; Zone (fig. 4). However, the upper part of the member no occurrence of them in western Utah has been shown has yielded few trilobites and may be as young as the to be laterally extensive enough to serve as a mapping Saukiella serotina Subzone, an interpretation supported horizon except locally. Stromatolites lend a character­ by conodont correlations to areas where faunas of the istic appearance to the Hellnmaria Member, for they S. serotina Subzone are better represented. weather to form massive, smoothly rounded cliffs.

LAVA DAM MEMBER (NEW) RED TOPS MEMBER (NEW) The Lava Dam Member is named for outcrops on both The Red Tops Member derives its name from that north and south sides of the "Lava Dam," a geologic part of the southern House Range shown as Red Tops feature shown by Hintze (1974b) on The Barn 15-minute in sec. 31, T. 22 S., R. 13 W. on the 1960 edition of The quadrangle in sec. 6, T. 23 S., R. 13 W. Location and Barn 15-minute topographic quadrangle. The type sec­ description of the type section near Notch Peak are tion is located in the House Range about 8 km southeast given in the section on "Measured Sections." The of Notch Peak. Description of the type section is given Steamboat Pass-Lava Dam reference section for the in the section on "Measured Sections." The Steamboat Notch Peak Formation in the southern House Range Pass-Lava Dam reference section in the southern House is important to the biostratigraphy because it has Range has been more closely sampled for trilobites and yielded abundant conodont and trilobite collections conodonts than has the type section and is thus impor­ (pl. 1). tant from a biostratigraphic standpoint (Miller and The Lava Dam Member is entirely limestone and in­ others, 1982). The Red Tops Member consists mostly cludes much stromatolitic limestone and cherty lime­ of thin-bedded bioclastic lime grainstone that forms stone in the House Range and Wah Wah Mountains. beds less resistant than the more massive members The member usually forms resistant cliffs and ledges above and below. Its light brown weathered color also that contrast topographically with the low ledges and contrasts with the predominantly gray color of the ad­ rounded slopes of the overlying Pogonip Group. jacent members. Halite and gypsum occur in some out­ Conodonts described by Miller (1969) came mostly crops of the Red Tops Member in the Steamboat from the Lava Dam Member, which he informally called Pass-Lava Dam section, southern House Range (Miller, member six. Most of the relatively thick Cambrooisto­ 1978, p. 24). Preliminary petrographic study suggests dus minutus Subzone of the Proconodontus Zone is that the evaporite minerals in the Red Tops are of within the lower part of the member. The remainder of secondary origin and probably were emplaced by the Lava Dam Member is assigned to various subzones NOTCH PEAK FORMATION CORRELATIVE IN UTAH AND NEVADA of the Cordylodus proavus Zone (fig. 4), which is Trilobite Conodont M o Zone 0 § o> Zone equivalent to Fauna A of Ethington and Clark (1971). w Lrtho- Trilobite Conodont e (0 (0 M stratigraphy Subzone Subzone The uppermost part of the C. proavus Zone is in strata assigned to the House Limestone (fig. 4). * Symphysurina bulbosa THlobite faunas allow relatively detailed zonation of Conodont Fauna B the Lava Dam Member. The lower 17 m of the Lava Dam Member have not yielded trilobites, but conodont cor­ Symphysurina House relations suggest that these beds are equivalent to the Limestone Ctauohamu/us hintzei Symphysun na Saukiella serotina Subzone of the Saukia Zone. Trilobite breuispicata faunas from the Lava Dam Member above 17m are ORDOVICIAN Canadian Hirsutodontus assigned to the S. serotina and Eurekia apopsis Sub- simplex zones of the Saukia Zone; the Missisquoia depressa and Cordylodusproauus Missisquoia typicalis Subzones of the Missisquoia Clauohamulus elongatus Zone; and the lowermost part of the Symphysurina Missisquoia brevispicata Subzone of the Symphysurina Zone (fig. 4). Missisquoia DamMemberLava typicalis Fryxellodontus Following the present North American practice inornatus (Winston and Nicholls, 1967; Taylor and Halley, 1974; Missisquoia Stitt, 1977; Miller and others, 1982), the Cambrian- depressa Hirsutodontus Ordovician boundary is placed at the base of the Missis­ Eurekia apopsis hirsutus quoia Zone. This horizon is 43.3 m above the base of the Lava Dam Member in the Steamboat Pass-Lava Dam Saukiella Cambrooistodus minutus measured section. This biostratigraphic horizon is serotina recognized by the lowest occurrence of the trilobite

Trempealeauan-i Missisquoia depressa Stitt, which is within the Hir- .a Eoconodontus FormationNotchPeak MemberTopsRed Proconodontus notchpeakensis sutodontus hirsutus conodont Subzone in the southern a CO Saukiella House Range (fig. 4, pi. 1). junta Proconodontus Hintze (1982) proposed the term Ibexian to replace muelleri Canadian for the Lower Ordovician series in North * America. The Cambrian-Ordovician Boundary Working Saukiella MattheuiaZonule Proconodontus Group, International Union of Geological Sciences, is pyrene posterocostatus currently in the process of recommending an interna­ * * Proconodontus tional stratotype for the Cambrian-Ordovician bound­ Ef/ipso- tenuiserratus cephaloides ary. We choose to defer formal acceptance of the Ibexian CAMBRIAN Croixan Series until a decision has been made on the system MemberHellnmaria Idahoia boundary. Drumaspis

* NOTCH PEAK FORMATION Idahoia lirae No CORRELATIVES IN UTAH AND NEVADA Franconian Upper Correlative upper Upper Cambrian and Lower Ordovi­ Taenicephalus zonation cian carbonate rocks are known by several names in Utah (fig. 2). Although few fossils have been reported Parabolinoides from these strata, their correlation with the Notch Peak LimestoneSneakover established can be generally established by the widespread occur­ OrrFormation Member rence ofElvinia Zone trilobites in beds below and Sym­ physurina Zone trilobites in overlying strata (fig. 2). Eluinia In the Dugway Range (figs. 1 and 2), Staatz and Carr (1964) described 270 m of mostly dolomites as the Dugway Ridge Dolomite. A thin limestone horizon 33 m

FIGURE 4. Correlation of conodont and trilobite zones and subzones with the Notch Peak Formation. Trilobite zonal nomenclature from Winston and Nicholls (1967), Longacre (1970), Stitt (1971, 1977), and Miller and others (1982). Asterisk indicates unit not recognized in Notch Peak Formation or adjacent formations but present elsewhere in biostratigraphic position shown. 8 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH below the top of the Dugway Ridge Dolomite yielded be regarded as indicative of the Notch Peak Formation. scraps of the trilobite Eurekia(l}. This thin limestone Thus, Whitebread's House Limestone appears to in­ may correlate with at least part of the Red Tops clude beds that we would include with the upper Member. Species of Eurekia are common in the members of the Notch Peak Formation. Whitebread Saukiella junta and Saukiella serotina Subzones of the (1969) did not differentiate an equivalent of the Saukia Zone. Sneakover Limestone Member of the Orr Formation but Cohenour (1959, p. 57) reported that the Ajax Dolo­ extended the Notch Peak downsection to the top of the mite in the Sheeprock Mountains is 310 m thick and Corset Spring Shale. However, the basal 210 ft of Notch devoid of fossils. Morris and Levering (1961, p. 48) Peak strata described by Whitebread (1969, p. 5) include reported that the combined Emerald Member and up­ pinkish-gray and pale-red silty partings that are typical per member of the Ajax Dolomite in the East Tintic of the Sneakover Limestone Member of the Orr. The Mountains are 116m thick; the Ajax bears Eurekia sp. stratigraphic sequence in the southern Snake Range ap­ near its top. More recently, Taylor and Repetski (1985) pears to be similar to that in the House Range but the reported Lower Ordovician conodonts from the upper easily mappable lithologic-topographic breaks occur at member of the Ajax in the type section. slightly different positions in the two areas. The Notch The St. Charles Formation in northern Utah consists Peak Formation has not been used elsewhere in Nevada. of three members, the lowest of which is the Worm In the southern Egan Range of eastern Nevada, Kellogg Creek Quartzite Member. According to Palmer (1971, (1963) mapped coeval Upper Cambrian carbonates as p. 48) the Worm Creek Quartzite Member is the cor­ the Whipple Cave Formation. In southeastern Nevada, relative of the Corset Spring Shale Member of the Orr near Pioche, the name Mendha Formation was applied Formation (fig. 2). The unnamed middle limestone by Merriam (1964) to a thick sequence of carbonate member of the St. Charles Formation bears an abun­ rocks that bear faunas ranging from the Upper Cam­ dant "Ptychaspis fauna" (Lochman and Hu, 1959) that brian Crepicephalus and Elvinia Zones to the Lower Or­ is here assigned to the Idahoia Zone of the Franconian dovician Symphysurina and Kainella Zones. The Stage. The upper member of the St. Charles Formation Mendha Formation occurs in an area of much faulting consists of thick to massively bedded dolomite and con­ and its complete sequence has not been described in tains upper Cordylodus proavus Zone conodonts at least detail, but it includes strata equivalent to the Notch 14m below the top (Landing, 1981; Taylor and Landing, Peak Formation. 1982). The Garden City Formation disconformably overlies the St. Charles in the Bear River Range and contains upper Symphysurina Zone trilobites at its base BIOSTRATIGRAPHY (Ross, 1951; Taylor and Landing, 1982). Thus, the mid­ dle and upper carbonate members of the St. Charles For­ CONODONTS mation are approximately equivalent to the Notch Peak Formation. Conodont samples have been studied from part of the In the Deep Creek Range, Nolan (1935) and Bick Notch Peak principal reference section (table 1, fig. 5, (1966) have mapped the Chokecherry Dolomite. Because pi. 1), from the Steamboat Pass-Lava Dam reference of faulting, secondary dolomitization, and beveling of section (tables 2, 3; pi. 1), and from several additional the Chokecherry on the flank of the Ordovician Tooele sections (not reported here) in the House Range. The Arch, the upper and lower boundaries of the formation systematic relations of these conodonts were described are not clearly defined. The only fossil reported from by Miller (1969, 1980), and the biostratigraphy was the part of the Chokecherry that seems most litholog- discussed by Miller (1976, 1978) and Miller and others ically similar to the Notch Peak Formation is Scae- (1982). The conodont fauna! data (tables 1-3) include vogyraC?), a gastropod of limited value for correlation. 24,030 conodonts from 167 samples of limestone and Whitebread (1969) extended the Notch Peak Forma­ dolomite. The total rock mass processed was 373 kg. tion into the southern Snake Range, Nevada, but he Of the two major sections, the Steamboat Pass-Lava selected different mapping boundaries than were used Dam reference section by far has the more detailed in western Utah. His Notch Peak-House contact was fauna! control. taken at the change from massive cherty limestone, Conodonts are extremely rare in the Hellnmaria below the contact, to thinner bedded but locally massive Member of the Notch Peak Formation. In the lower limestone above. In the stratigraphic section descrip­ map unit of the Hellnmaria Member in the Steamboat tion that accompanies his map he reported Pass-Lava Dam section, only three conodonts have stromatolites from the lower portion of his House been found, although the member was sampled exten­ Limestone. In Utah sections, the stromatolites would sively. At 17.4 m above the base of the member, two (/>

M CAMBRIAN ORDOVICIAN a

House Notch Peak Formation Limestone

Hellnmaria Member Member Red Tops Member Lava Dam Member

Zone Conodont Proconodontus Zone Cordylodus proavus Zone

established zonation No notchpeakensisSubzone 51 Proconodontusmuelleri hirsutusHirsutodontus simp/exHirsutodontus hintzeiC/auo/iamu/us SubzoneConodont Subzone Eoconodontus Subzone M 3 X Subzone e/ongatus C/auo/iamu/us Subzone Cambrooistodus minutus Subzone N& 3§ o^& 000. 3 C O a> M = I

" tS3 tS3 tS3 tS3 N) CO CO CO CO U i* -t» iss £ . O 00 0 to -P- tSJ -t» 03 00 0 tSJ -t» 09 00 0 N) 4* 05 OO O N) .p" O3 CO C3 N9 c 0 O C O O O OO O O O O O O O O 00000 O O O O O O C3 O 1 1 1 III 1 1 1 1 1 1 1 1 1 III 1 1 1 1 1 i 1 ! 1 1 1 1 1 1 BIOSTRATIGRAPHY e N9 -t» O N9 Ji 09 00 O O O O 0 0 0 N9 5. o O s Prooneotodus gallatini (Muller) Prooneotodus rotundatus (Druce and Jones) Proconodontus? primitiuus (Muller) Proconodontus muelleri Miller Eoconodontus notchpeakensis (Miller), rounded element Eoconodontus notchpeakensis (Miller), compressed element Cambrooistodus cambricus (Miller), compressed element 31 Cambrooistodus minutus (Miller), compressed element D) Cordylodus proavus Muller, rounded element Cordylodus proavus Muller, rounded element M Hirsutodontus hirsutus Miller O^ Teridontus nakamurai (Nogami) O o Fryxellodontus inornatus Miller o a Fryxellodontus lineatus Miller o Hirsutodontus rarus Miller (/)o Semiacontiodus nogamii Miller, asymmetrical element Semiacontiodus nogamii Miller, symmetrical element 2. CD Clavohamulus e/ongatus Miller M Utahconus utahensis (Miller) Monocostodus sevierensis (Miller)

Hirsutodontus simplex (Druce and Jones) 1 Cordylodus intermedius Furnish, compressed element Drepanodus? sp. Albiconus postcostatus Miller Utahconus tennis Miller, bicostate element

FIGURE 5. Ranges of conodonts in the principal reference section of the Notch Peak Formation, central House Range, Utah. 10 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

TABLE 1. Conodont distribution in the principal reference section of the Notch Peak [Sample numbers identify stratigraphic unit (RT, Red Tops Member; LD, Lava Dam Member; H, House Limestone), followed by the measured distance in feet above the base of the numbers of specimens per sample are given.

Notch Peak Formation

Rad Tops Member (42.7 m) Lave Dam Member (110.9 m)

f~» O CO CM » 00 « f"» r- O ^-OCT) OCT) O)O)O)O)O> OO>O«~ CM CM CO CO CO CNCO^-tOCO CO CM CM o cioddd «-O*-CN

or- co co co «- t- t-CNCNCMCO CO't't o co to « t « « CMCNCOCO

oo in ^ o o ocNcom «-«-cooo «-co^ cot-coco^ cor-cooi- «- «- «- o*~ oico^mco r COCT>T 1 1 1 1 1 | 1 | 1 1 | 1 1 O D O O O O O OOOO

Conodonts: 7 ,,. _ 5 6 - -> 10 T 17 1 1 ^ 2 Prooneotodus rotundatus (Druce and Jones)

29 3 27 46 5 11 11 74 10 8 2 32 j _ . , i i ^ 4 Eocanodontus notchpeakensis (Miller), 2 * 2 ~ 2 1 2 2 3! 2 Eoconodontus notchpeakensis (Miller),

Cambrooistodus cambricus (Miller), ...... 1 ... 1 Cambrooistodus minutus (Miller), ...... 1 2 1 1 Cordylodus proavus Muller, rounded

Cordylodus proavus Muller, compressed

Semiacontiodus nogamii Miller,

Semiacontiodus nogamii Miller,

i Hirsutodontus simplex (Druce and Jones)- - Cordj/Jodus intermedius Furnish,

Utahconus tenuis MiBer, bicostate element- ],.. ... ^ ...... ,i£ »,...... -__ . ... .« .... ._ ^ __, sf,, :i « i : M .._ 42 3 73 82 19 99 22 166 15 16 2 67 4 33 23 2547

Prooneotodus gallatini (Muller) were found, and at 28 isolated sample (USGS loc. 8343-CO) from the Helln­ m above the base, a single Westergaardodina maria Member approximately 5 km south of the type bicuspidata Muller was found. These species are not section. A list of taxa found at that locality is given in diagnostic of age, but are consistent with the presence the section on "Trilobites." of Taenicephalus Zone trilobites in this part of the Additional conodont faunas, possibly from the Helln­ Hellnmaria Member. The type section of the Hellnmaria maria Member, are known from the Chalk Knolls area, Member has not been sampled for conodonts. However, between the House and Confusion Ranges. The strati- a systematic search in the member 6.5 km to the west graphic relations there are unclear because of facies (NP section of Miller, 1969) produced no conodonts. A changes between limestones of the Notch Peak principal few long-ranging species of conodonts were found in an reference section and dolomites of the sections to the BIOSTRATIGRAPHY 11

Formation and lower part of the House Limestone, central House Range, Utah member. Renumbering begins at base of Lava Dam Member and continues into the House Limestone. Numbers of identified specimens of each species in each sample, and total A range chart is given in figure 5.]

House Notch Peak Formation Limestone

Leve Dam Member (110.9 m)

CM CM co r» en ^ enentoencM in m «- co o oo co ^ o ^ o r^ «- «- tn coooco*-co CM «- CM o ^ CM *- CM CO «- CO in «- T- CM «- «- CM «- CO CM TfCMCOCMO OCMCMCMCM

CM en oo co en CM in «- in r-» r-» in ^ to co in T co oo O en o « co CM CM en o ^ >".- * 06 do CM en * in O CM to Tt in cocoooeno «- to Tt r~ en Tt CN co CM en Tt * O O O «- «- «- «- CM co r~ r~ oo oo

r~ ^ CM r~ O CM CM * * * oo en *- co in r~ en CO CO 00 CM fx ^ «7 CM CM CM CM CM CO CO CO CO CO co co co en o o o o o o o o o 66 66666

23 _ _ --- _s ______... ~- ...... '.-- ii, 5_ - -*.

4 65 5 6 6 10 23 J 2 9 21 464 2 30 7 14 3 2 15 4 24 31 11 9 45 1 31 8 1

... 32 2 2 2 12 1 2 14 158 2 85 12 4 2 73 20 23 4 6 24 2 1

7 ......

...... 6 36 8 56 6 43 473 105 21 17 6 27 7 43 52 8 8 42 41 121 22 18

...... 2 10 8 2 10 46 30 491 55 13 28 3 5 7 34 2 9 42 10 _= ...... ,, 3 ... 3 ...... 3 2 192 30 1 735115 12 37 12 101 110 103 130 22 3 1

__ - __ _. , _ ~i.i _ -=- i.i i» -.... ,_ ft 0 , -I .

69 4 ......

1 ......

...... 30 o Z

;.. ' '!= . * ' ' "' "" 24 7

~.i -~~ ' * - - 1

4 2 ...... -j 4 130 15 58 21 12 108 2 4 25 90 1364 4 220 15 60 37 19 118 25 112 186 66 316 394 369 913 106 40 5

south and north (fig. 3). Proconodontus tenuiserratus Trempealeauan age. Therefore, strata of this age are Miller and P. posterocostatus Miller occur together present in the Notch Peak Formation in the study area, beneath faunas assigned to the P. muelleri Subzone of although the member to which these strata should be the Proconodontus Zone. These occurrences are in the assigned is unclear. These data suggest that the same homotaxial position as strata assigned to the Pro­ Hellnmaria Member (or its equivalents) may represent conodontus posterocostatus Subzone of the Pro­ continuous deposition without major hiatus. conodontus Zone in the Wilberns Formation of Texas Conodonts are present throughout the Red Tops and and in the Fort Sill Limestone of Oklahoma (Miller and Lava Dam Members of the Notch Peak Formation others, 1982). Trilobites found with this association of (tables 1-3). The conodont biostratigraphy of these conodont species in Texas and Oklahoma are of earliest strata was discussed by Miller (1978), Miller in Taylor 12 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

TABLE 2. Conodont distribution in the Notch Peak Formation in the Steamboat Pass [Sample numbers identify lithostratigraphic unit (RT, Red Tops Member; LD, Lava Dam Member), followed by the measured distance in feet above the base of the member Numbers

Notch Peak Formation

Member - - __ - ______Red Tops Member (40 m)

00 CD CD 00 00 r^ CD CD CD CD CM O CD CD 00 CD r- 06600 66666 0600666 66

r~inr- ooroooooro ooo inqcp^ "? ^ 6 CN 06 in 06 o> ^ CN inoo

Oino ifl o in «- ifl CM CM in o in moo O in T- «- CM CM co co ^ ^ in CD up r^ r^ op o> h-KKKK KKKKK KKKKK HK tr.tr.cr.cr.tr. cr.tr.tr.tr.tr. crcrcr.cr.cr. tree Conodonts: ... 1 -. 7 6 3 ~ 2 *-- 2 ~ 6 1 H-^ £- .- -- - , - *-i. >; - ,. - - -.-. -i - - 4 1 1 1 1 Prooneotodus galiatini (Miiller) - -- »-. . ».». . »

Cordylodus proauus Miiller, compressed element ------

,: ,,,,

_ * _ _wi _i_ i. ^ _ -^ ~«i --

and Miller (1981), and Miller and others (1982). The Red assigned to the Cambrooistodus minutus Subzone, the Tops and lower part of the Lava Dam Members are uppermost subzone of the Proconodontus Zone. assigned to the Proconodontus Zone. The upper part of The Cordylodus proavus Zone is divided into five sub- the Lava Dam Member and the lower part of the overly­ zones, four of which are represented in the Lava Dam ing House Limestone are assigned to the Cordylodus Member; the uppermost subzone is found in the lower proavus Zone (fig. 4). Conodonts of the Proconodontus part of the House Limestone. The Hirsutodontus hir- Zone are modest in abundance and diversity compared sutus Subzone is the lowest and thinnest subzone and with those of the C. proavus Zone. Tables 1 and 2 show is present near the middle of the Lava Dam Member. that occasional barren samples, though usually of small As discussed below, the Cambrian-Ordovician boundary size, were found in the lower zone, whereas all samples falls within this subzone (pi. 1). The overlying Fryx- in the upper zone were productive, and some samples ellodontus inornatus and Clavohamulus elongatus Sub- yielded abundant faunas. zones are recognized in both sections studied and occur The Proconodontus Zone is divided into four subzones in the upper part of the Lava Dam Member. The up­ (Miller and others, 1982), although the lowermost sub- permost beds of the Lava Dam Member are assigned zone is not recognized in any of the sections discussed to the lower part of the Hirsutodontus simplex Subzone; in this report. The base of the Proconodontus muelleri most of this subzone is represented in the lower part Subzone nearly corresponds with the base of the Red of the House Limestone. The highest strata of the Tops Member, which represents a major environmental Steamboat Pass-Lava Dam section are assigned to the and lithologic change from the Hellnmaria Member House Limestone, although Miller (1969) earlier as­ below (fig. 3, pi. 1). The lower part of the Red Tops signed these beds to member six of the Notch Peak For­ Member in the type section and in the Steamboat Pass- mation in his LDS (Lava Dam South) measured section, Lava Dam section is assigned to the P. muelleri Sub- located a few hundred meters south of the Lava Dam zone. The middle to upper part of the Red Tops Member segment of the Steamboat Pass-Lava Dam section is assigned to the Eoconodontus notchpeakensis Sub- reported here. The uppermost beds of the Steamboat zone. The uppermost beds of the Red Tops Member and Pass-Lava Dam section contain the diagnostic fauna of about the lower half of the Lava Dam Member are the Clavohamulus hintzei Subzone. Utahconus tenuis BIOSTRATIGRAPHY 13 segment of the Steamboat Pass-Lava Dam section, southern House Range, Utah of identified specimens of each species by sample and total number of specimens per sample are shown. A composite range chart of data from tables 2, 3, and 4 is given in plate 1 ]

Notch Peak Formation

Red Tops Member (40 m) Lava Dem Member (82.6 m)

00 oo r» in oo oo oo in m r^ 00 oo co r^r^r^Ooo ojor^or^ cn cn r^ in m co O CO O O «- CO O O O CM CM OOOO OOO«-O OOO«-O O O CO ^t CM CO CO CM ocom o CD ^- >- co in co CM o oococo^cn ^ O co en oo ^ oo co cncno CM CM *t m co r» enrv.com ^^^.(000 en-cM-*in r^ en co co oo en CM CM co co co co co co co OCM^tin r~oo«-^^ .-CMCNCMCM CM CM ^ ^ t ^> in in

o in r~ co in o co CM ^- O CM O CO inr^o o o «- «- CM CM ^ oo ^-oooococn mO'tom o in ^- in co co 6666 66666 66666 D D D D D Q 6 6 DC OC OC CCCCCCCCCC DC

1 C OO OC 1*3O 5 : - . . m 4 >-A 4 t 2 -- I*K "- 1 C *3"? *l C *t 1 C O S - :=:------.,* "7 O O Jl fl ^\ *> *3 3 fi 1Q 1fl* A *^R 23B 7 ...... , ,_, .« , __ 4 . ^^ -| 4 -.. *^i 1 7 °. . - "i1 62 3 ii. i-ii R 1 * 1 A ., 1 1 - - 1 1 A ' - : ,: i:,, ,.. 1 ;: ;: on o 1 ...... 2

1 ...... 2 ...... TO 1 2 CO -1 OQ 3 1 9 -.-. *i-i -~- .-a-- 9~ i'R

3 -1 _^ ... ,,- ...... ,-: ^. ^, -~- ^ .~.'. i- ^ w_ -__ -,- ^ =* T- -- ~, ST;-?! 7r; , -~ ^-- ^h si 1 *? 19THR1Q9R QRA RR

Miller was found in the highest sample collected from in the Steamboat Pass-Lava Dam section than in the the lower beds of the House Limestone at the principal principal reference section. This relationship suggests reference section of the Notch Peak Formation (pi. 1). that the base of the Red Tops Member may be younger Because this species is known only from the middle and in the principal reference section than in the Steamboat upper part of the Clavohamulus hintzei Subzone in Pass-Lava Dam section. Using similar reasoning regard­ Utah, Texas, and Oklahoma (Miller and others, 1982), ing the relative proximity of the Red Tops-Lava Dam the base of the C. hintzei Subzone probably is somewhat contact to the base of the Cambrooistodus minutus Sub- below the horizon from which this highest sample was zone, it can be inferred that this stratigraphic contact collected. may also be younger in the principal reference section The top of the Cordylodus proavus Zone has not been than in the Steamboat Pass-Lava Dam Section. recognized in either of the two sections reported here. The Proconodontus mueueri and Eoconodontus notch­ Samples collected 1.6 km north of the Steamboat Pass- peakensis Subzones are thicker in the Steamboat Pass- Lava Dam section [LDN (Lava Dam North) section of Lava Dam section compared with the principal Miller, 1969] indicate that only the top few feet of the reference section. This relationship is reversed for most C. proavus Zone are missing from the Steamboat Pass- of the younger biostratigraphic units in these sections Lava Dam section. The overlying strata at the LDN sec­ (compare columns on fig. 6), and the Cambrooistodus tion contain conodont Fauna B of Ethington and Clark minutus through Clavohamulus elongatus Subzones are (1971) (Miller, 1978; Miller and others, 1982). all thicker in the principal reference section. The greater Upon comparing conodont biostratigraphic units be­ thickness of the Fryxellodontus inornatus and tween the principal reference section and the Steamboat Clavohamulus elongatus Subzones in the principal Pass-Lava Dam section (fig. 6), several important con­ reference section may be related to relatively rapid ac­ clusions are evident. In the Red Tops Member, the cumulation of the algal stromatolite sediment in the up­ relative position of both the Proconodontus muelleri- per part of the Lava Dam Member (compare columns Eoconodontus notchpeakensis Subzone boundary and 2 and 3 on fig. 3). The base of the Hirsutodontus simplex the Eoconodontus notchpeakensis-Cambrooistodus Subzone is only slightly below the Notch Peak minutus Subzone boundary are stratigraphically higher Formation-House Limestone contact in both sections. 14 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

TABLE 3. Conodont distribution in the Notch Peak Formation and lower House Limestone in [Sample numbers identify lithostratigraphic unit (RT. Red Tops Member; LD, Lava Dam Member; H, House Limestone), followed by the measured distance in feet above the base and total number of specimens per sample are shown. A composite

Notch Peak Formation

Mamb r Red Tops Member (20.1 m) Lava Dam Member (77.4 m)

T-»frmincocoiO'"; oooip ; CO f^rOinco O r^iococo cs cs CDC5,-,- co co'tirir^ 06 CD* T « « T T T CN O r-CO^(Ov « CNCNJ CO

Sampla mass (kilograms) procassed- . intocsl CN IDOOCOI^ 00 cn«^oo ^cn CMOOO^CO ^-csitDOco csimin

(0 "? o CM in m ID r~ oco^cn* i^ in T to omO(O in^co o h-Hh-HH HHh-h-H h-HHHh- Hh-HH-QQQQQC) QQQ Q tr tr tr cc cc tr tr tr tr cc Conodonts: Proconbdontus m.we/teff Miller -- -' 42 258 15 >4 4 58 3 2 4j ,25 5.1 4 ,27' ^58 -* - 23 14 it 8 2S \9. slvl ; 15 - ^* 86"* 5 '28 17 "85 Eocimodontus notchpeakensts (Miller), \ roufided*e1ement-- --_^- ?-~_,i- 4O 35 20 4 j? :|4 39 3 :; *^- 5 5S :; 40 ,38 05'IIS^ 411^1833 5 --35:1115! 4; 132521 1* Eoconodontus notehpecfcensis (Miller), ; 17 13 3! 13; 3s =7 4 - ^ 10 iS ;6 26 12 2 IB 6 a 17 1 .4. 12 ?9 6 1 8; 16; W

Proo weotoclus r.otundatas: 23 1^ 4' 35 1 1 :~ _ _ 2* ^^, ^ n^ jn m * ^-sw^r-tttodaaaHBBBIS

Proconodontus? primitiuus (Muller) ...... 4 ... 1 .- ! 3 ...... 1 ...... 3 O Cambrooi'stodtis cambricus (Miller), T ...... 11 2 1 2

Cdmferopfstodtis m/nutus (Miller); 3 . ... * . ^ *l *i :- -^^^^^^1 Procofiodofrtus, serrati/s Mitlerf-rij*---- \ 1 - U«- -i^ i"4 =-- ' i.** W*- i-J^i -i.^ Ui-i. Cordylodus. pfoavus Muller, ; \. rpurtdedtejement' ,^u.~~^~~~^- ' ' *;! -^ >-, - .... .,. ,, __ w COrdyfodussprpafus MOItef; '. ' compressedf «jerneni-~"-«*^-- ---', Mrsutodohfus hirsutus Miller-- - ~~ '

' 3* " i X :=* a»- ^- ^ a a ^^ ^ « 9

$emtacontiodus nogamii Miller, . ; asymmetrical element-"-^- --'--- ...... ^ ^_ .-- ,4. ^ ^ .* ^ ^ H.. __ __ ^ ______^ __ ^ ,. w __ ., ,, ^- SerniacoritSdduA noganiii Milter;! ; 1 symmetrical element- *--- -« I Afpflpeostoifuii sevterensis (Miller)--; ?- ^s ^ ^ ,. ,... ^ ^ ^ «. . s __ - - .- - -w-^- - -w*, **. -.-.....% -..,. tj^.^ Hirsutodontus simplex

Semiacontiodus lavadamensis (Miller),

Cordy/odus intermedius Furnish,

. -compressed element- : -- , ..-- -:: ;._^ .,, -,,. ,T, S . ,__ . . - ______i CtaoohatnuiUs bintzei Millet--"^ -- - *' rTr¥l?E^r£"-»":Y^ Utaficonvs tertuis, Miller, 1 ......

CdrdyftSdussdrocei Miller; ':

i rotindfed i element--- -! » -? ----- : ,^,______. ^ ...______,,., _^_- ^^^ ^ ____ ; _^ ^v ^^^ ^i. wt> -: ^V^- fw._^ __^-. '-V,.-. 5^_- ^,______^, ^^._ ____ Total specimens per sample 1 50 1 1 3 46 68 1 7 11510 2 9 113 77 51 150242 6 119 32 50 87 16 24 75 23 35 13 27 71 50 34 BIOSTRATIGRAPHY 15

the Lava Dam segment of the Steamboat Pass-Lava Dam section, southern House Range, Utah of the unit. Renumbering begins at the base of the Lava Dam Member and continues into the House Limestone. Numbers of identified specimens of each species by sample range chart of data from tables 2, 3, and 4 is given in plate 1]

Notch Peak Formation House Limestone

Lava Dem Member (77.4 m)

CD in in CD coinococo co co ^J- r^ co in co O5 CM «- CO «- CD 00 ^f CM r~ CM *- CM r^ O in O in ^ C> CD co Ocococo ^f^fin inco r- o ! » in r^ oo O - CM ^f CD r~ O) ^ 0 «- CO CD r^ O) 0 O O CO O) O) O) O)

CO in - in o - oo in ^J- oo co 00 CO >- ^f ^ r~ CD CD CM CO in in CM in CD 00 O) O) O * ^ O) CM ^ «- CO ^d" ,_ CO CM CO CM CO CO CM CO CO CM CO .- .- O «- O 0 0 0 0 0 O CO <- >- - CM ^f «- co O in O O co T- CM co in r^ co OCM CD in O * O * O in CO ^f CM co «- CM csi co CO CO * in in 0 CD CD - in O in o in O CO CO «y CM CM CM CM CM CM CM CM m CD r^ en O O - CM CM CO CO CM CM CM CO CO CO CO CO CO CO CO co 6 Q QQQO QOQ QQ Q Q Q Q 6 Q Q Q 6 Q ° ? i i i i i i i i i i i i

S3

739? 7JJ 71 4 43

196 26: 4f 23: ;63 24 - -5 !2 s;

1 1L_ 3L 1

;4 31 48 251103 102 22 45 68 S 44 21

21 1 27 s9 9 10 521 ill 52 7*1 j iBQ, |48 128J 45 46 9 29 2O 1 8; 1C ;& 6 14: 17 6 22 21. 20 B ------1 ------~^i * :::: ------* < Vo 'irv - '£& A a "*? e*~ ^ 2 -** - J " :-*"* ~-*~ f, \ i-' **.*. Kiii« ::_-_^ :. - ^i^. ^ \^ ^V *"" " - O *t' IJ O ~ = ' **"* £. tj"- "~"'' ...... 202 6 13 2 2 '-'.." { ... 7 1' " "3 " 2 146 "--'-"" ...... 29 6 1 1 33 1 7 9 58 190 57 45 43 35 97170476 185 71 157101340 246 52 174127 26 51 340 58 ...... ?i 2 15 2 2 55 6 6 3 10 5 13 - - ...... 3 1 ... 2 1 14 5221 ...... 6 18 15104 24123 __ ':- . ., .-,- .,.. ,-. ... ,-,.- __ __ .._ ..,; . 5; :s vt 52. 27 rr-*"^-^'- !2 -r- l-; 1 K "t -rr5"^ 4 ! a % "^.aw-J1^--^.-*

;5 1O 41 3 27S J2; 34 5i ;24

'1 ! 1 H !6 17 -^ i-* 2; 10 3- -^ --.- ;~ 14 40 89 76

5 15 3 3 4 17 93 89 8 1 23 ...... 2

1 8 10 %!:-- 3¥SSSf-~" ~~

1 3 10 4s 2 18: 7 8 ! 2 ' 4 ,4-. 47 tO

2 1 ;53 12

_ ,4 7; J1 7 11671591581080 9256702108241 35657810161011494 373257517547663521206382309803 682169551497485 155171834219 16 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

Siteamboat Passs- Typ e section of the A similar relationship occurs in other nearby sections Lava Dam Lava Dam, Red T ops, not reported here, suggesting that this stratigraphic section and Hellnmaria Members d) boundary may be nearly isochronous in the study area.

Base of Clavohamulus / CO f 3 £ hintzei Subzone>. / £i_i Hit sutodontus / TRILOBITES simplex Subzone ^/ /. NlO.6 m 363ft Notch Peak Formation has yielded trilobites from the

Q) House Range area that are as old as the late Franco- 94.5 m nian Taenicephalus Zone and as young as the Early Or- 3 W \7/ 310 ft O 0> I E dovician (early Canadian age) Symphysurina Zone. Some Li

CO Orygmaspis and Taenicephalus, and absence of CO Parabolinoides. The upper part of the Sneakover minutus Limestone Member of the Orr Formation, which im­ 40.0 m mediately underlies the Hellnmaria Member of the 131 ftv 0- 42.7 m Notch Peak Formation, has yielded Parabolinoides sp. 36.6 m ~" _ __ 140 ft. - 0 in the Lawson Cove section (7668-CO), Wah Wah Moun­ 120ft JQ N. Subzone E Q) tains; in the Steamboat Pass-Lava Dam section, ^\ Eoconodontus Member"ops southern House Range; and in Big Horse Canyon ^^ notchpeakensis 21.3 m \^ Subzone (7669-CO), Candland Canyon-Little Valley section 01 70 ft Q. (8243-CO), central House Range (fig. 3). One sample O (D2831-CO) from 20.4 m above the base of the 18.6 m Hellnmaria Member (pi. 1) contains Taenicephalus sp. 61 ft and Billingsella sp. These data show that the contact o Proconodontus ^x.

FIGURE 6. Correlation of lithostratigraphic and some conodont biostratigraphic units between the Steamboat Pass-Lava Dam section and principal reference section of the Notch Peak Formation. Numbers indicate feet and meters above base of units for various boundaries shown. BIOSTRATIGRAPHY 17 about 150 m north of U.S. Highway 50 in an unsurveyed the Signal Mountain Limestone in Oklahoma show that area 7.8 km east of the road intersection on the east side the base of the Cambrooistodus minutus Subzone of the of Skull Rock Pass, Notch Peak quadrangle, Utah. The Proconodontus Zone occurs near the base of the sample contains the following taxa: Saukiella serotina Subzone in those areas. In the Steam­ Trilobites: boat Pass-Lava Dam section, the base of the Cam­ Drumaspis cf. D. walcotti Resser brooistodus minutus Subzone is at 3.4 m below the top Idahoia sp. of the Red Tops Member, which is approximately Pseudagnostus sp. 20.1 m below the lowest recognized trilobite assem­ Taenicephalina(l) sp. blages assigned to the Saukiella serotina Subzone. For cf. Wilbemia sp. this reason the stratigraphic interval between highest Conodonts: definite S. junia trilobite assemblages and lowest Prooneotodus gallatini (Miiller) definite S. serotina Subzone assemblages is assigned P. rotundatus (Druce and Jones) with question to the «S. serotina Subzone (see pi. 1). Phakelodus tenuis (Miiller) The Saukiella serotina Subzone is recognized in the Brachiopods: Steamboat Pass-Lava Dam section by the occurrence Billingsella(!) sp. of Euptychaspis kirki Kobayashi, Macronoda sp., Angulotreta vescula Grant Heterocaryon tuberculatum Rasetti, and Leiocoryphe Linguloid, gen. and sp. undet. platycephala Kobayashi. The base of the zone is at least The sample is assigned to the Drumaspis Subzone of as low as 16.8 m above the base of the Lava Dam the Idahoia Zone, upper Franconian Stage. Member, but may occur as low as 7.6 m below the top The uppermost Franconian Ellipsocephaloides Zone of the Red Tops Member (see further discussion under of Longacre (1970), here considered a subzone of the "Saukiella junia Subzone"). The top of the

Orr House Formation Notch Peak Formation Limestone

Sneekover He||nmer|e Limestone Membflr O Red Tops Member (40 m) Lava Dam Member (77.4 m) Member (3Q4 (46.6 m)

N) N) M NJ N> M M M *. M M M M M M GO CO GO ->N)N)N)GO GO .&,.&. .p. .&, ^.^.^.^.^ ^.^.«j%j>J Meters ebove base of member ~ Ol O> O 00 CO O COO-»N)GO OICOONJOO O>N)GOvlO COOOOO _»_«-» CO ^ OIOI*- 1^ 1^ OOO) GO Ul * GO 00 Ol -»'*.cocobi bb)boGo-> bocobo^bo b)bibibibi bibibocobo ^j co t. co *. co co ^J B DO D ODD DODO ODD D DO OO O OOO OOOOO N) N) N) Ol Ol Ol OIOIIOMN) Ol M M M M M M M 00 M M M 00 M M M 00 M M M M M M M M D2812-CO W 00 00 00 &> 00 00 *-*-OOvlOO OI-JOO-JOO OOOOOOOOO OOOOOOOOO OOOOOOOOO 0000000000 D2825-CO D2827-CO S3 N) 00 GO CO *. -» COCO-»CO-» OCO-»CO-« OO-«COO -^OCOOO -.COO-"-1 NJOIOION) CO CD -» >J *. GO 00 CO GO ^1 *. O 00 Ol CO O) O M ^1 CO GO 00 *. (jl O5 Ol CO O) ^1 O -" O CO M *. GO O 66 6666 66666 66666 66666 66666 66666 66666 S3 o o o o o o ooooo ooooo ooooo ooooo ooooo ooooo O o Trilobites:

.,.,,,, , , ...... ,. .,.,, .,.,.,. .... ,, ,,,.,., ,. ,

f

... ,,,, ,,, ,, * ...... , , , , , , , ,,', . .... '" "" Monocheifus sp«-" ~ -~ ;---- .,.., ...... '" '" :""" :""" '"""" """"" ...... ' " "'""" "" '" '" "" ' ...

______w __ __ r f ______

Bayfieldia simata :.,,.."".; ,,..,, .,. ,,: ::,,:' , " r " " " '" " ...., , .,,, . , ,, ----- ::

,$

,,,, ..,,,,.,,,,,. ... *...... < ...... ,, ----- BttyfieldiO Sp,r r-,,, . , - rSBS*rrss ; Stertopi/us bacca Resser- -w x Acldaspls u/ricty Bassler - *«-- . x Heterocoryon tubercu/atum Rasetti X X Rasettia wichitaensis (Resser) - Idiomesus intermedius Rasetti X X Stenopilus latus Ulrich -- - cf. Leiocoryphe platycephala Kobayashi- Stenopilus sp. Eurekia apopsis (Winston and Nichblis) --" - * cf ? x x x cf x Acheilops masonensis Winston and Triartftropsfs sp. Larifugula leonensis (Winston and TVlarthrdpsfe nitida Ulrich ~r-r Triarthropsis prtncetonensis Kobayashi- - - - cf Plethometopus armatus (Billings) Missisquoia depressa Stitt Missisquoi'a typicalis Shaw cf x x Highgatella cordilleri (Lochman)- HysfricUrus sp, i-~p* --?> ~r;"-"" cf. h-(w $ymphysurino breuisplcatci Hitttze-**?- o Missisq uoia inflata Wiristbniand Nichdlls .*- * z

Syrnphysuiina bubops ;; Wjnston and Kljcholls X' i Symphysurtna sp. X ? Cf Apatokephaloid, undet.

Brachiopods: Billingsetta Orthoids, gen. and sp. undet. X XX X X Inarticulates, gen. and sp. undet.

Mollusks:

Gastropod, low-spired dextral X X XX X X Gastropod, high-spired dextral-- Gastropod, high-spired sinistral- Nautiloid cephalopod? -

Other: Echinodermal cblumnals--- Ech'modermal frSrhe piatesTr!s;s Hy pjithoids - -T.-^ ----- T- Sponge spicules ---^r-? 20 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH exclude the lower range of Symphysurina, which had As so defined, the Symphysurina brevispicata Subzone been included in the zone by the original definition of the Symphysurina Zone can be recognized in the (Winston and Nicholls, 1967). Steamboat Pass-Lava Dam section beginning 74.4 m Based on meticulously detailed collecting in the above the base of the Lava Dam Member (equals 3.0m Signal Mountain Limestone in Oklahoma, Stitt (1977, below top of Notch Peak Formation). pi. 7) refined and divided the zone into a lower Missis- Hintze's Ibex section B (Hintze, 1951, p. 33-37; 1952, quota depressa Subzone and an upper Missisquoia p. 25, 26) was measured about 2.4 km north of the Lava typicalis Subzone. Both subzones can be recognized in Dam segment of the Steamboat Pass-Lava Dam section the Notch Peak Formation. The M. depressa Subzone reported here. He reported a trilobite fauna from 2.1m is recognized at one horizon (D2810-CO) 43.3 m above above the base of the House Limestone that contains the base of the Lava Dam Member in the Steamboat Hystricurus millardensis, Symphysurina brevispicata, Pass-Lava Dam section (pi. 1). The sample contains Symphysurina cf. S. cleora (Walcott), and some non- Missisquoia depressa Stitt, Plethometopus armatus trilobite fossils. This assemblage shows affinity with the (Billings), and a single indeterminate olenid free cheek. S. brevispicata Subzone as defined by Stitt (1977) and, The Missisquoia typicalis Subzone is recognized in together with new trilobite data reported here (table 4, the Steamboat Pass-Lava Dam section by the occur­ pi. 1), suggests that the S. brevispicata Subzone spans rence of Missisquoia typicalis Shaw. The subzone ex­ the boundary between the Notch Peak and House tends between 44.8 m and 74.4 m above the base of the Formations. Lava Dam Member (pi. 1). The top of the zone is defined The position of the top of the Symphysurina brevispi­ by the lowest occurrence of Symphysurina brevispicata. cata Subzone is uncertain in the House Range-Ibex area, Symphysurina Zone. Lower Ordovician rocks in the but probably is no higher than 33.5 m above the base western United States were initially divided by Ross of the House Limestone in Ibex section B (Hintze, 1951, (1949, 1951) into a scheme of trilobite assemblage zones p. 36; 1952, p. 26) where Bellefontia sp. occurs. Bellefon­ designated by the letters A to M in the Garden City tia is typical of the upper part of the Symphysurina and Swan Peak Formations of southeastern Idaho and Zone that is approximately equal to Zone B of Ross northeastern Utah. Hintze (1951, 1952) applied the Ross (1951). zonal scheme, with some emendations, to the Pogonip Group in the House Range-Ibex area of western Utah, the area of the present study. Hintze (1952, p. 5) did MEASURED SECTIONS OF THE not recognize Zone A of Ross; instead he assigned his NOTCH PEAK FORMATION lowest Ordovician trilobite assemblage to Zone B which he called the Symphysurina Zone. Hintze's (1952, p. 7) TYPE SECTION OF THE Symphysurina Zone consists of a lower part character­ NOTCH PEAK FORMATION, HOUSE RANGE, UTAH ized by Hystricurus millardensis Hintze and Sym­ physurina brevispicata Hintze, and an upper part that The type locality of the Notch Peak Formation was contains different species of Hystricurus and Sym­ designated by Walcott (1908a, p. 9) as the "upper por­ physurina in association with species of Clelandia, tion of the main mass of Notch Peak," and his described Xenostegium, and Bellefontia. Taylor and Landing section was measured (Walcott, 1908b, p. 173) "on the (1982) showed that trilobite Zone B of Hintze (1951) cor­ east and southeast slopes and ridges of Notch Peak." relates with trilobite Zones A and B of Ross (1949) and Walcott did not designate a stratigraphic boundary at some older beds assigned to lower parts of the Sym­ the top of the formation, apparently taking the upper­ physurina Zone that are missing from the Bear River most beds on Notch Peak as the highest unit he meas­ Range section because of a disconformity between the ured. Hintze (1951, 1973) defined the top of the Notch St. Charles and Garden City Formations. Peak Formation by identifying its stratigraphic contact Stitt (1977) studied trilobite collections from the with the base of the overlying House Limestone in the Signal Mountain Limestone of the Wichita Mountains, type section for that formation 8 km south of Notch Oklahoma, and divided the Symphysurina Zone into a Peak. The base of the Notch Peak Formation was lower Symphysurina brevispicata Subzone and an up­ designated by Walcott at its contact with the Orr For­ per Symphysurina bulbosa Subzone. Stitt (1977, mation, which was redescribed by Hintze and Palmer p. 32-36, pi. 7) defined the base of the Symphysurina (1976). brevispicata Subzone on the lowest occurrence of Sym­ The geologic map of the Notch Peak quadrangle physurina brevispicata Hintze and Highgatella cor- (Hintze, 1974a) shows the contacts of the Notch Peak dilleri (Lochman). The overlying S. bulbosa Subzone is Formation with the Orr Formation and House Lime­ defined by the lowest occurrence of S. bulbosa Lochman. stone in accordance with the present definitions. The MEASURED SECTIONS OF THE NOTCH PEAK FORMATION 21 113°20f map shows that strata on Notch Peak itself have been recrystallized by contact metamorphism associated with a granitic intrusion a few kilometers north of the peak. Because of the uncertainty of the exact location of Walcott's original measured section and because of the metamorphism on the peak itself, designation of a principal reference section for the Notch Peak Forma­ tion is warranted. Because of faulting, the formation cannot be traversed in a single unbroken section. The segments were selected on the basis of completeness of exposure and ease of accessibility. They are located (fig. 7) on the ridges southeast of Notch Peak and thus fall within the locale originally designated by Walcott.

1 MILE

REFERENCE SECTIONS OF THE NOTCH PEAK FORMATION FIGURE 7. Principal reference section of the Notch Peak Formation in the central House Range, Utah, as located on the Notch Peak 15-minute quadrangle. Last letter of the geologic symbol identifies Principal reference section for the Notch Peak Formation and the type the type section of each member: Gnh, Hellnmaria Member; Gnr, sections for its Hellnmaria, Red Tops, and Lava Dam Members, Cen­ Red Tops Member; OGnl, Lava Dam Member. tral House Range, Utah

Type section for the basal part of the Hellnmaria Member is located Notch Peak Formation Continued in SE1/4 sec. 35, T. 19 S., R. 13 W. The type for the remainder of the Lava Dam Member Continued Hellnmaria Member was measured in two segments in sec. 2, T. 20 S., Thickness R. 13 W., as shown in figure 7. The type section for the Red Tops Unit (Meters) (Feet) and Lava Dam Members were measured in sec. 5, T. 20 S., R. 13 W. 30. Stromatolitic limestone Continued as shown on figure 7. a few thin beds of lime mudstone and The Notch Peak Formation in its type area conformably overlies minor chert. Forms massive rounded the Orr Formation and conformably underlies the House Limestone. cliff ...... 58.4 192 Massive basal limestones and dolomites of the Notch Peak form nearly 29. Lime mudstone, medium-dark-gray, vertical cliffs above the ledges of the upper part of the Orr Forma­ cherty; forms ledge ...... 4.0 13 tion. Similarly, bold cliffs of the Lava Dam Member stand in contrast 28. Covered ...... 1.2 4 with the topographic expression of the stairstep ledges of the overly­ 27. Lime mudstone, light- to dark-gray; forms ing House Limestone. ledges ...... 2.2 Detailed faunal data are given in figure 5 and table 1. Conodonts 26. Oolitic lime grainstone. Fault with about listed in the section were identified by J. F. Miller; Cambrian trilobites 7 m vertical offset repeats oolite along were identified by M. E. Taylor, Ordovician trilobites by L. F. Hintze section traverse ...... 0.6 and M. E. Taylor; Lava Dam and Red Tops Members were described 25. Lime mudstone, medium-gray, cherty; by J. F. Miller; the Hellnmaria Member was described by L. F. Hintze. forms ledges more prominent than unit below. Upper 2 m poorly exposed . . 18.2 60 House Limestone 24. Lime mudstone, medium-dark-gray, thin- to medium-bedded, includes 5 percent Thickness Unit (Meters) (Feet) chert as small irregularly bedded 31. Lime mudstone, medium-gray, thin- to masses in the middle one-third of the thick-bedded, includes 10-30 percent unit. Forms ledges mostly less than 1 brown chert in irregularly bedded m high, but includes basal ledges as masses; forms ledges above cliffs at top much as 3 m high and ledges near the of Notch Peak Formation. Symphy- middle and top as much as 6 m high. surina was identified from bioclastic Occasional thin beds of lime grainstone lens at the base of the unit, and from are present. The contact between Red scattered disarticulated silicified frag­ Tops and Lava Dam Members is placed ments at the top of the unit ...... 15.1 50 at the change from brown-weathering Notch Peak Formation (principal reference section) grainstone of the Red Tops to gray lime Lava Dam Member (type section) mudstone of the Lava Dam. Topo­ 30. Stromatolitic limestone, medium-gray, graphic contrast accompanies the lith- massive. Algal stromatolites range ologic change. The Red Tops Member from 15 to 30 cm across and 60 to 100 forms a bench or slope, and the Lava cm in height. Unit mostly composed of Dam Member forms ledges and cliffs 26.3 86 hemispherical stromatolites with lime Total thickness of Lava Dam grainstone filling interstices. Includes Member ...... 110.9 364 22 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

Notch Peak Formation Continued Notch Peak Formation Continued Red Tops Member (type section) Hellnmaria Member Continued Thickness Thickness Unit (Meters) (Feet) Unit {Meters) (Feet) 23. Lime grains tone and intraformational 13. Stromatolitic limestone Continued conglomerate, medium-brownish-gray; small nodules. Measured section offsets weathers shades of reddish brown; from base of this unit across fault- forms slopes and low ledges less than controlled saddle along ridge crest to 2 m high. Uppermost ledge is 2 m below triangulation station Easy . .... 21.4 70 top of unit and is gray lime mudstone 12. Stromatolitic limestone, medium-dark- similar in lithology to overlying Lava gray; algal heads 15-60 cm across and Dam Member ...... 13.1 43 as much as 150 cm high; forms rounded 22. Intraformational conglomerate and lime knobs and ledges; inter-stromatolitic grainstone, brown to gray, thin-bedded, fillings are partly mottled olive gray, poorly exposed; forms slope except for dolomitic, and include 1 percent chert 25.9 85 a low ledge 2 m above base ...... 11.9 39 11. Interbedded Stromatolitic limestone and 21. Lime grainstone and intraformational medium-crystalline limestone. Stro­ conglomerate with few thin interbeds matolitic limestone forms 60 percent of of lime mudstone, medium-brownish- unit in beds as much as 3 m thick; gray, weathers reddish brown, thin- to medium- to thick-bedded medium- crystalline, medium-dark-gray lime­ medium-bedded; forms slopes and low stone with 5 percent chert makes up re­ ledges as much as 1 m high. Fragmen- mainder. Base of this unit is elevation tal trilobites at 1 and 6 m above base 7.6 25 5960 northeast of Easy hilltop. Offset 20. Lime mudstone, medium-gray, inter- across saddle to top of next small hill bedded with coarse lime grainstone that in order to continue section . 33.5 110 weathers reddish brown and includes 10. Interbedded lime grainstone and thin cherty stringers. A 15-cm oolitic Stromatolitic limestone. Medium- to grainstone bed is 1.3 m below the top. coarsely crystalline, medium- to thick- Silicified trilobites and black linguloid bedded, medium-dark-gray lime brachiopods at 1 m above base. Unit grainstone makes up 60 percent of unit. forms prominent ledge ...... 4.0 ]3 Algal stromatolites make up 40 percent 19. Intraformational conglomerate, gray to including basal 2 m. Poorly preserved brown ...... 0.3 1 Matthevia 21 m above base 44.2 145 18. Covered ...... 2.1 7 9. Lime mudstone, medium-dark-gray, with 17. Lime grainstone with sparry calcite, 5 percent chert as dark-brown bedded brownish-gray, with 3 percent chert as nodules. Silicified Matthevia 2 m above stringers as much as 1 cm thick; 30-cm base. Thin bed of oncolites 8 m above oolitic bed 3 m above base. Trilobites base ...... 12.2 40 3.3 m above base. Unit forms ledge at Lime grainstone, medium-dark-gray, base of Red Tops Member. Contact medium- to coarsely crystalline, thick- with Hellnmaria Member placed at bedded to massive, forms smooth slope; lithologic change from b'me grainstone contains small irregular markings that above to algal stromatolite below 3.7 12 suggest fossil traces but nothing is Total thickness of Red Tops identifiable; includes 5 percent chert 29.0 95 Member ...... 42.7 140 7. Lime grainstone, medium-gray, medium- to coarsely crystalline, medium- to Hellnmaria Member (type section) thick-bedded, with 5 percent chert; 16. Stromatolitic limestone, medium-gray; forms level terrain along traverse. hemispherical stromatolites range from Fragmental trilobites in coarsely 15 to 60 cm across and 30 to 75 cm crystalline limestone bed 8 m above high; forms massive ledge .... 2.4 base ...... 13.7 45 15. Interbedded lime mudstone and lime 6. Limestone, medium-gray, fine- to grainstone, medium-dark-gray to medium-crystalline, massive, contains mottled gray and brownish-gray, thin- 1 percent chert, unfossiliferous; forms bedded; mottled beds are partly dolo- ledge ...... 15.3 50 mitic; a few beds show mud cracks; 5. Limestone, medium-dark-gray, finely forms slope ...... 9.1 30 crystalline, with 6 percent chert as 14. Lime mudstone, medium-dark-gray; beds irregularly bedded masses, unfossil­ are 60-120 cm thick, form low ledges 4.6 15 iferous, forms ledges. Section offsets 13. Stromatolitic limestone, medium-dark- northward 400 m across fault and dip gray; algal heads 15-60 cm across slope to continue on north end of hill and as much as 130 cm high; forms 5843 ...... 12.1 40 massive ledges and cliffs; includes 1 4. Limestone, medium- to medium-dark- percent chert in thin stringers and gray, medium- to finely crystalline, MEASURED SECTIONS OF THE NOTCH PEAK FORMATION 23

North Peak Formation Continued 113°20' Hellnmaria Member Continued Thickness Unit (Meters) (Feet} 4. Limestone Continued massive, contains 2-5 percent dark- brown chert as discontinuous irregular bedded masses as much as 5 cm thick and 15 cm long. Bedding in unit is marked by slight color changes and by chert masses. One 15-cm bed of oolites and pisolites occurs in middle of unit. No skeletal fossils found. Forms cliffs and ledges ...... 109.7 360 3. Limestone, medium- to medium-dark- gray, finely crystalline, uneven bed­ ding, contains 2-5 percent chert as discontinuous irregular dark-brown masses on some bedding surfaces, un- fossiliferous, forms cliff. Contact with underlying Orr Formation is confor­ mable and is marked by transition from ledge-slope to cliff topographic expres­ sion ...... 33.5 110 Total thickness of Hellnmaria Member ...... 366.7 1203 Total thickness of Notch Peak Formation ...... 520.3 1707

Contact conformable R 14 W R 13 W Orr Formation 1 2 KILOMETERS J______1 Sneakover Limestone Member T 2. Limestone, medium-dark-gray, medium- 0 1 MILE to finely crystalline, forms ledges 0.6-1.2 m high, distinctive pink silty FIGURE 8. Steamboat Pass-Lava Dam reference section of the Notch material on irregular bedding surface; Peak Formation, southern House Range, as located on The Barn phosphatic brachiopods common in up­ 15-minute quadrangle, Utah. Last letter of the geologic symbol iden­ per third along with 5 percent dark- tifies the member or map unit: Gnhl, lower map unit of the Helln­ brown chert as thin irregularly bedded maria Member; Gnhm, middle map unit of the Hellnmaria Member; masses. Silicified Eoorthis rare 3 m Gnhu, upper map unit of the Hellnmaria Member; Gnr, Red Tops above base ...... 28.3 96 Member; OGnl, Lava Dam Member; Oh, House Limestone. 1. Limestone, medium-light-gray, coarse to medium-crystalline, forms ledges 0.6-1.5 m high, some beds with House Limestone (upper part eroded) fragmental trilobites. Base of measured Thickness section is where limestones are covered Unit (Meters) (Feet) by alluvium ...... 18.9 62 41. Lime mudstone, medium-gray, with 20 percent bedded chert. Chert darker and more evenly bedded than unit below. Steamboat Pass-Lava Dam section, southern House Range, Utah Unit forms steplike ledges to top of hill 18.3 60 40. Arenaceous limestone and skeletal lime Because of faulting (see Hintze, 1974b), the section was traversed grainstone, medium-gray and brownish- in segments selected for optimum exposure. Base of section is in the gray, some silty beds. Admixed quartz NW1/4 sec. 19, T. 23 S., R. 13 W., as shown on The Barn 15-minute sand, fine grained. 30 percent bedded quadrangle (fig. 8). The middle and upper parts of the Hellnmaria chert, light- to dark-brownish-gray, Member and the Red Tops Member were measured in sec. 18 as shown some nodular chert. Unit forms upper on figure 8. The Lava Dam Member was measured in the south half part of cliff ...... 7.9 26 of sec. 6 and the north half of sec. 7, T. 23 S., R. 13 W. (fig. 8). A Exposed thickness of House geologic map of the Lava Dam area and general position of the Lava Limestone 26.2 86 Dam segment of the traverse is given in figure 9. Detailed faunal data Notch Peak Formation are given in tables 2, 3, and 4, and plate 1. Conodonts were identified Lava Dam Member by J. F. Miller, trilobites were identified by M. E. Taylor, and mollusks 39. Lime mudstone, medium-gray, forming were identified by M. E. Taylor and E. L. Yochelson. The section was massive main cliff in upper part of measured and described by J. F. Miller and L. F. Hintze with emen­ member. 5-10 percent nodular bedded dations by M. E. Taylor. chert and chert stringers. Prominent 24 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

113°22' 113°2V Notch Peak Formation Continued Lava Dam Member Continued Thickness Unit (Meters) (Feet) 36. Lime mudstone, medium- to dark-gray, some ledges cherty. Unit forms promi­ nent ledges, thicker than ledges in 16.8 m thick unit below. Prominent ledge 29.0-30.5 m, top forms large flat bench. At 30.8 m partly silicified Eup- tychaspis fauna in several 7-cm thick, very dense lime mudstone beds. Thin- bedded, very argillaceous and highly burrowed lime mudstone 30.8-31.1 m. Four prominent ledges in upper part of unit, top three ledges cherty. Covered slope 39.6-40.2 m. Lime mudstone bed at 40.2-40.5 m ...... 11.6 38 35. Lime mudstone, medium- to dark-gray, some weathering brown; cherty, forms low ledges 2-7 cm thick with thinly covered slopes. Ledges thinner than in unit below. Between 19.8 m and 21.3 m cross small fault and repeat 0.9 m of section ...... 15.8 52 34. Lime mudstone, medium-gray, minor 1 MILE chert, forms four prominent ledges. Cherty ledge 10.7-12.2 m, covered FIGURE 9. Geologic map of area in the vicinity of the Steamboat 8.8-10.7 m; ledge with argillaceous Pass-Lava Dam reference section of the Notch Peak Formation, partings 7.9- 8.8 m covered 6.7-7.9 m. Utah. V's show the path of the measured section. Qac, Quaternary Prominent cherty ledge 2.7-6.7 m, alluvium and colluvium; TV, Tertiary volcanic rocks; Oh, Ordovi- covered 2.1-2.7 m. Basal 2-m thick cian House Limestone; OGnl, Lava Dam Member of the Notch Peak ledge cherty with abundant burrows at Formation; Gnr, Red Tops Member of the Notch Peak Formation; 1 m; fossil debris and minor flat pebble Gnh, Hellnmaria Member of the Notch Peak Formation. Geology conglomerate at 2.1 m ...... 12.2 40 modified from Hintze (1974b). Total thickness Lava Dam Notch Peak Formation Continued Member 77.4 254 Lava Dam Member Continued Thickness Red Tops Member Unit (Meters) (Feet) 33. Lime grainstone with thin beds of intra- 39. Lime mudstone Continued formational conglomerate, medium- break in slope at top of unit. Traverse brownish-gray, partly covered slope 3.0 10 offset 12 m to east across fault at base 32. Lime mudstone, medium-gray, minor of unit ...... 28.7 94 chert, forms ledge similar to those in 38. Lime mudstone, medium- to light-gray, Lava Dam Member ...... 1.2 mottled brown to pink, slightly cherty, 31. Limestone, interbedded grainstone, oncolitic, burrowed Ledge at 46-47.9 m, wackestone and intraformational con­ covered from 47.9-48.8 m ...... 2.7 glomerate, gray to brown, with less 37. Lime grainstone, pebbly, oolitic, light-gray, than 2 percent chert; forms low ledges with minor chert, interbedded with and slopes, upper part poorly exposed. cherty and noncherty, dense lime mud- Grainstones include abundant trilobite stone and lime wackestone. Oolite from debris, especially near base ...... 5.5 18 40.5- 42.1 m, lime mudstone and wacke­ 30. Stromatolitic limestone, medium-gray, in­ stone 42.1-43.3 m. Prominent ledge dividual algal heads as much as 20 cm 40.5- 43.3 m. At 43.6 m oolitic lime across. Forms a bioherm 3-5 m across grainstone bed with granules and fine surrounded by lime grainstone and pebbles. Covered 43.6-43.9 m. Cherty wackestone. Other similar mounds near- lime mudstone and wackestone by ...... 1.8 43.9-45.7 m, 45.1-45.7 m possibly poor­ 29. Limestone, light-brown to gray, grain- ly laminated, high-relief stromatolites. stone and wackestone, mostly trilobite White chert bed 5-15 cm thick forms debris, thin-bedded, with silty partings, marker bed at 45.1 m. Oolitic and peb­ some twiggy bodies and minor chert 4.0 13 bly lime grainstone 45.9-46.0 m con­ 28. Limestone, medium-gray to brownish-gray, taining abundant orthoid brachiopods weathers to reddish- and yellowish-gray, and trilobites ...... 5.5 18 mostly grainstone and wackestone, MEASURED SECTIONS OF THE NOTCH PEAK FORMATION 25

Notch Peak Formation Continued Notch Peak Formation Continued Red 1bps Member Continued Hellnmaria Member middle map unit Continued Thickness Unit (Meters) (Feet) Thickness 28. Limestone Con tin ued Unit (Meters) (Feet) including much trilobite debris, thin- to 20. Dolomite, light-gray, large algal masses, as medium-bedded; forms low ledges. Thin much as 60 cm in diameter, silicified Mat- oolitic horizons at 3, 4, and 5 m above thevia common ...... 9.8 32 base and a thicker oolitic zone from 7 19. Dolomite, dark-gray, sugary texture, dolo- to 10 m above base. A few beds include mitized shelly fossils and dark-colored intraformational conglomerate and oncolites about 2 cm in diameter give the some contain minor chert nodules. Well- unit a mottled appearanca Collection preserved trilobites at base and 2 m 60 cm above the base of the unit contains below top ...... 11.0 36 silicified Matthevia sp...... 2.7 9 27. Limestone, medium- to dark-gray, medium- 18. Dolomite, light-gray, weathers light bedded. Interbedded medium-grained brownish gray, sugary texture, forms lime mudstone, lime wackestone, and prominent light band on hill, un- skeletal grainstone with minor chert as fossiliferous ...... 5.5 18 stringers and nodules. Pinkish- and 17. Dolomite, medium- to dark-gray; banded; yellowish-brown silt marks mottled part­ silicified fossils common; samples ings. Pisolites are included in beds near 5497-CO from 1 m above base of unit the top and 6 m above the base and near and 5844-CO from 3 m above base con­ base of unit. Forms low ledges, makes a tain Matherella sp., and Matthevia sp. 7.0 23 conspicuous dark-gray band between the 16. Dolomite, dark-gray, alternating mottled brown-weathering units above and the and laminated, sugary texture, with 2 lighter gray upper Hellnmaria beds percent chert as nodules; forms ledges 4.9 16 below. Well-preserved trilobites about 15. Dolomite, light-gray, composed entirely of 10 m above base. Contact with Helln­ high-relief stromatolites averaging 20-cm maria Member is conformable and diameter, these structures resemble large marked by changes from light-gray, mud crack polygons on weathered bed­ massive stromatolitic limestone below to ding surfaces ...... 4.9 16 darker gray thinner bedded clastic lime­ 14. Dolomite, light-gray, weathers light brown­ stones above. Contact is undulatory but ish gray, several chert bands 2-3 cm thick sharp ...... 13.4 _44 at top of unit; relict high-relief stromato­ Total thickness of Red Tops lites common ...... 3.0 10 Member ...... 39.9 131 13. Dolomite, dark-gray, weathers same, in- terbedded laminated and mottled; poor­ Hellnmaria Member upper map unit ly preserved fossil debris; 1 percent chert (Hintze, 1974b) as bedded stringers ...... 9.1 30 26. Stromatolitic limestone, light-gray; com­ 12. Dolomite, light-gray, sugary, weathers light posed mostly of algal heads 15-30 cm in brownish gray ...... 1.5 5 diameter with fine-grained lime mudstone 11. Dolomite, dark-gray, with lighter colored between, forms rounded cliffs and relict fossil fragments; forms ledges . . 10.7 35 smooth slopes ...... 22.9 75 10. Dolomite, light-gray, weathers light brown­ 25. Dolomite, alternating light- and dark-gray ish gray; forms lowest prominent light beds, some relict algal stromatolite struc­ band in darker dolomites; forms ledges 2.7 9 tures, forms slopes ...... 10.7 35 9. Dolomite, dark-gray, weathers brownish 24 Stromatolitic dolomite, light-gray, forms low gray, thin- to thick-bedded; forms ledges, ledges ...... 2.7 __9 some beds mottled, others thinly lami­ Total thickness of upper map nated and cross-laminated. From 8 to unit 36.3 119 10 m above the base of the unit is an in­ termittent black and white zebra-fabric Hellnmaria Member middle map unit dolomite along strike, passing laterally in­ (Hintze, 1974b) to dark dolomite Silicified gastropods, 23. Dolomite, alternating medium- and dark- Matherella sp., in upper two-thirds of this gray, poorly preserved algal heads com­ unit ...... 47.6 156 prise about 50 percent of unit. Top of this 8. Dolomite, dark-gray, weathers dark unit is top of ledge- and cliff-forming cen­ brownish gray; 5 percent bedded chert as tral part of the Notch Peak Formation in elongated nodules about 2 cm thick; some the Black Hills area ...... 11.3 37 dolomite beds banded, others with fossil 22. Dolomite, light-gray, composed mostly of debris ...... 6.1 20 high-relief stromatolites about 30 cm in 7. Dolomite, dark-brownish-gray, with in- diameter ...... 2.7 9 terbedded white and grayish-black zebra- 21. Dolomite, dark-gray; poorly preserved fabric dolomite in beds 60-120 cm thick. silicified gastropod shells are common 1.8 6 These lowest beds of the middle map unit 26 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH

Notch Peak Formation Con tinned Hellnmaria Member middle map unit Continued Thickness Unit (Meters) (Feet) 7. Dolomite Con tinned form step ledges above the more massive but rounded cliffs of the lower map unit of the Hellnmaria Member. An algal-head bed about 60 cm thick oc­ curs 10m above the base of this unit 22.9 75 Total thickness of middle map unit 154.2 506 Hellnmaria Member lower map unit (Hmtze, 1974b) 6. Limestone, fine-grained lime mudstone, dark-bluish-gray, thick-bedded, 5 per­ cent bedded chert; forms rounded cliff top. Sharp contact with overlying R 15 W R 14 W 0 1 2 KILOMETERS dolomites ...... 19.5 64 5. Limestone, medium-grained lime I 0 1 MILE mudstone, medium-gray, thick-bedded, with 10 percent bedded chert ...... 25.9 85 FIGURE 10. Lawson Cove reference section of the Notch Peak For­ 4. Limestone, fine-grained lime mudstone, mation, Wah Wah Mountains, Utah, as located on the Wah Wah medium-gray, medium-bedded; forms Summit and Frisco Peak 15-minute quadrangles. Last letter of the break in cliff ...... 6.1 20 geologic symbol identifies the members: Gnh, Hellnmaria Member; 3. Limestone, fine-grained lime mudstone, Cnr, Red Tops Member; OCnl, Lava Dam Member. medium-gray, thick-bedded, with 10 percent bedded chert, weathers light- persists into the northeastern edge of the Wah Wah Mountains but brownish-gray; forms cliffs 41.2 135 thins rapidly to the southwest within the range. Base of the measured 2. Limestone, fine- to medium-grained, section is in SW1/4 sec. 30, T. 24 S., R. 14 W. as shown on figure 10. medium-dark-gray, thick-bedded, with The Red Tops and Lava Dam Members were measured in the east uneven "chicken-wire" bedding etched half of sec. 4, T. 25 S., R. 15 W. The geology of the latter area is shown on weathered surfaces, stylolites com­ on the map by Hintze (1974e). The section was measured and described mon; forms cliffs. Contact taken at base by L. F. Hintze. of prominent cliffs above step ledges of Orr Formation ...... 21.3 70 House Limestone Total thickness of lower map Thickness unit ...... 114.0 374 Unit iMeters) (Feet) Total thickness of Hellnmaria 27. Limestone, medium-gray, weathers Member ...... 304.5 999 medium bluish gray, mostly siliceous calcisiltite, thin- to medium-bedded; Total thickness of Notch Peak forms low ledges capping hilltop and Formation ...... 454.7 1492 extending down back slope, includes Contact conformable less than 5 percent chert as dark-brown Orr Formation bedded nodules. Symphysurina coquina Sneakover Limestone Member in thin horizon near base, beds mostly 1. Lime mudstone, medium-dark-gray, unfossiliferous, nonstromatolitic 137.2 450 medium-grained, thin-bedded; forms Total thickness of House ledges 60-120 cm high; silty partings Limestone .... . 137.2 450 weather pinkish and orangish gray. Contact conformable Base of member covered by alluvium 21.3 70 Notch Peak Formation Lava Dam Member 26. Stromatolitic limestone, medium-gray, Lawson Cove Section, Wah Wah Mountains, Utah. algal heads 15-30 cm in diameter; forms massive ledge ...... 1.5 This reference section is established to show the variation in 25. Limestone, medium-gray, mostly fine- to thickness and lithology of members of the Notch Peak Formation as medium-grained lime mudstone, it is followed along the strike 20 km southward from the House Range medium- to thick-bedded; forms ledges sections. The lower map unit of the Hellnmaria Member can be and cliffs, includes 10-30 percent chert recognized in the Wah Wah Mountains but the middle and upper map as light-brown to black bedded nodules 41.1 135 units (Hintze, 1974b), whose differentiation is based on stromatolite 24. Stromatolitic limestone, medium-gray, beds, cannot be traced into the Wah Wah Mountains probably because algal heads as much as 30 cm in the stromatolite mounds were not areally extensive at any one time diameter, 60 cm high; forms massive during Hellnmaria deposition. The bioclastic Red Tops Member rounded cliff ...... 25.9 85 MEASURED SECTIONS OF THE NOTCH PEAK FORMATION 27

Notch Peak Formation Continued Notch Peak Formation Continued Lava Dam Member Continued Hellnmaria Member Continued Thickness Thickness Unit (Meters) (Feet) Unit (Meters) (Feed 23. Lime mudstone, medium-gray, with 10 12. Dolomite, light-brownish-gray, dolomitized percent chert, medium-bedded; forms high-relief stromatolites, massive; forms weak zone near base of cliffs ...... 3.1 10 ledges ...... 16.7 55 22. Stromatolitic limestone, medium-gray; 11. Dolomite, medium-gray to medium-brown, forms massive bed at base of prominent medium- to coarse-crystalline, with some cliffs near the top of the member 3.7 12 white zebra-fabric zones of replacement 21. Lime mudstone, medium-gray, medium- dolomite, thick-bedded. Silicified Mat- bedded, with 10 percent chert; forms thevia common. Includes 5 percent chert ledges averaging 120 cm high ..... 21.3 70 as brown nodules; forms ledges ..... 24.4 80 20. Lime grainstone, medium-dark-gray, 10. Stromatolitic limestone, medium-gray, mas­ medium- to coarse-grained, thin- to sive, with occasional silicified Matthevia 10.7 35 medium-bedded; forms low ledges. Con­ 9. Lime mudstone, medium-gray, includes 5 tains fragments of partly silicified percent chert; thin nodular bedding; trilobites including Euptychaspis . 16.8 55 forms slope ...... 4.6 15 19. Lime grainstone, medium-dark-gray, 8. Stromatolitic limestone, medium-gray, mostly medium-grained, includes 2 per­ massive; forms rounded ledge ...... 4.6 15 cent black chert as thin-bedded bands; Dolomite, medium-brownish-gray, medium- forms ledges averaging 1.3 m ..... 9.1 30 crystalline, thick-bedded, silicified Mat­ thevia abundant ...... 4.6 15 18. Lime mudstone, medium-dark-gray, 6. Stromatolitic dolomite, medium-brownish- medium-grained, includes 5 percent gray, massive ...... 6.1 20 chert; forms ledges 60-120 cm high 10.7 35 5. Dolomite, mostly dark-brownish-gray, some Total thickness of Lava Dam bands light-brownish-gray, thick-bedded, Member ...... 133.2 437 with 5 percent chert as brown nodules; Red 1bps Member forms ledges ...... 22.8 75 17. Lime grainstone, medium-gray to brownish- Dolomite, light-brownish-gray, medium- to gray, weathers yellowish brown, mostly coarse-crystalline, thick-bedded; forms coarse-grained, with abundant trilobite ledges. Shows as a conspicuous light debris, thin-bedded, slope-forming, with band on aerial photographs ...... 39.6 130 thin interbeds of silty lime mudstona Dolomite, dark-brownish-gray, coarse- This unit is approximately 30 m thick crystalline, with a 2-m-thick band of at the top of Hellnmaria measured zebra-fabric replacement dolomite at the section in sec. 30, but thins to half base and two similar zones higher in the that thickness where measured 7 km to unit. Includes 5 percent chert. Forms the west in sec. 4, apparently because prominent dark-brownish-gray cliff . . 67.0 220 the lime grainstone at the top of the Lime mudstone, medium-gray, fine- to med­ member passes westward into lime ium grained, thick-bedded to massive In­ mudstones included in the basal Lava cludes 5 percent chert as dark-brown thin Dam Member ...... 15.2 50 stringers and bedded nodules and 2 per­ Total thickness of Red 1bps cent argillaceous fillings of small vertical tubes 0.5 cm in diameter and 10 cm high. Member ...... 15.2 50 Forms uniform medium-gray smooth cliff Hellnmaria Member probably equivalent to the "lower map 16. Stromatolitic limestone, medium-gray, unit" of the Hellnmaria Member in the massive; forms rounded ledges. Becomes southern House Range (Hintze, 1974b) 134.1 440 dolomitic along strike ...... 10.7 35 Total thickness of Hellnmaria 15. Dolomite, medium-gray, medium- to coarse- Member ...... 408.4 1340 crystalline, medium- to thick-bedded; Tbtal thickness of Notch Peak forms ledges and back slope of hogback Formation ...... 556.8 1827 ridge near top of section ...... 15.2 50 14. Dolomite, medium-gray, with dark-gray Contact conformable bands and some thinly striped zones of Orr Formation white replacement dolomite, medium- Sneakover Limestone Member crystalline. Forms outcrops from saddle 1. Lime mudstone, light to dark-gray, medium- to crest of small hogback ridge at top of to thick-bedded, fine- to medium-grained, section ...... 36.6 120 with pinkish silty partings on beddings 13. Dolomite, alternating light and dark- surfaces. Phosphatic brachiopods common brownish-gray, in thin bands, medium- in dark layers. Forms ledges at base of crystalline, medium-bedded. Forms Notch Peak cliff ...... 25.9 85 ledges near the top of the lower of two A complete description of the Orr Forma­ hogback ridges near the top of the tion at this locality is given in Hintze and section ...... 10.7 35 Palmer (1976). 28 UPPER CAMBRIAN-LOWER ORDOVICIAN NOTCH PEAK FORMATION IN WESTERN UTAH 113°25' Fish Springs Range section, Utah.

This reference section is described to show that the member sub­ divisions recognized in the House Range cannot be traced north of the House Range apparently because the bioclastic grainstones that define the Red Tops Member in the House Range are not present in the Notch Peak Formation in the Fish Springs Range. Geologic maps by Hintze (1980a,b) of the Fish Springs Range show that although the Notch Peak Formation is exposed for 25 km along the crest of the range from Fish Springs headquarters southward, it is cut by numerous faults and brecciated in many places. The exposure selected for section measurement was chosen because it is almost unfaulted and can be traversed without special climbing equipment. The measured section is located in sec. 3, T. 13 S., T. 14 W. as shown on figure 11. The section was measured and described by L. F. Hintze.

House Limestone Thickness Unit {Meters) (Feet) R 14 17. Limestone, medium-gray, weathers medium 1 KILOMETER bluish gray, siliceous, silty, with 1 percent J______I chert as nodules in lower half increasing 1 MILE to 5 percent above, mostly medium- to thick-bedded. Forms step-ledges except for 10-m interval in middle which forms FIGURE 11. Fish Springs Range reference section of the Notch Peak a cliff. Symphysurina in basal beds . 36.6 120 Formation, as located on the Sand Pass NW 7.5-minute quadrangle, Total thickness of House Utah. Member divisions of the Notch Peak Formation (OGn) have Limestone .... 36.6 120 not been recognized in the Fish Springs Range. Contact conformable Notch Peak Formation 16. Dolomite, very light gray, weathers light- brownish gray, coarsely crystalline, thick- bedded to massive; forms ledges and cliffs 13.7 45 Notch Peak Formation Continued 15. Dolomite, dark-gray, weathers brownish gray, Thickness medium-crystalline, thick-bedded; forms Unit (Meters) {Feet) ledges ...... 34.4 113 7. Dolomite, medium-gray, weathers alter­ 14. Lime mudstone, medium-gray, silty, very nating light and dark brownish gray in thin bedded; forms reentrant ..... 0.9 3 broad bands, coarsely crystalline. Mat- 13. Dolomite, medium-dark-gray, weathers thevia poorly preserved in dark brownish gray, thick-bedded, with 1 per­ dolomite at base ... 6.7 22 cent chert; forms ledges ...... 17.7 58 6. Dolomite, medium-dark-gray, weathers 12. Dolomite, medium-gray, weathers light- brownish gray, with thin bands of brownish-gray, medium-crystalline, thick- lighter and darker shades, fine- to bedded. Forms upper prominent light- medium-crystalline, a few beds show brownish-gray band on Notch Peak cliff cross-bedding, and a few thin zones of face when viewed from a distance .... 36.0 118 banded white vuggy secondary 11. Dolomite, dark-gray, weathers brownish gray, dolomite. Includes 1 percent chert as medium- to coarsely crystalline, includes bedded nodules. Some horizons show at base a 2-m-thick pisolite marker bed, thin irregular small white markings and a few mottled horizons. Forms top of that suggest presence of fossils, but dark sequence in Notch Peak cliff face 9.5 31 nothing identifiable. Forms cliffs . . . 114.0 374 10. Dolomite, medium-gray, weathers light- 5. Dolomite, dark-gray, weathers brownish brownish-gray, medium-crystalline, thick- gray, mostly fine-crystalline, some bedded to massive; forms cliffs . . 28.7 94 medium-crystalline, contains 1 percent 9. Dolomite, dark-gray, weathers to brownish- chert as thin stringers and small gray and light-brownish-gray bands, nodules. Few layers with vuggy white- medium-crystalline, includes 5 percent striped beds of replacement dolomite, chert as prominent light-brown nodules. replacement beds laminated light Zebra fabric in white and dark gray dolo­ brown to dark brown, massive. Forms mite alteration zone 16 m above base ledges ...... 32.0 105 Forms cliffs ...... 55.2 181 4. Limestone, medium-dark-gray, thin- 8. Dolomite, light-gray, weathers light- bedded with wavy partings of silty brownish-gray, very coarsely crystalline, material on bedding surfaces. Forms massive; forms cliffs ...... 8.5 28 ledges ...... 2.1 REFERENCES CITED 29

Notch Peak Formation Continued Hintze, L. F., 1951, Lower Ordovician detailed stratigraphic sections Thickness for western Utah: Utah Geological and Mineralogical Survey Unit (Meters) (Feet) Bulletin 39, 99 p. 3. Dolomite, dark-gray, weathers brownish ___1952 [1953], Lower Ordovician trilobites from western Utah and gray, thin-bedded, wavy partings. eastern Nevada: Utah Geological and Mineralogical Survey Resembles upper beds of Sneakover but Bulletin 48, 249 p. is dolomitic. Includes 1 percent chert. ___1973a, Geologic History of Utah: Brigham Young University Upper 2 m is coarse-crystalline, re­ Geology Studies, v. 20, pt. 3, 181 p. mainder medium-crystalline. Basal con­ ___1973b, Lower and Middle Ordovician stratigraphic sections in tact with Sneakover is marked by sharp the Ibex area, Millard County, Utah: Brigham Young Universi­ change from limestone to dolomite . __8.5 __28 ty Geology Studies, v. 20, pt. 4, p. 3-36. Total thickness of Notch Peak _____1974a [1975], Preliminary geologic map of the Notch Peak quad­ Formation ...... 367.9 1207 rangle, Millard County, Utah: U.S. Geological Survey Miscella­ Contact conformable neous Field Studies Map MF-636. Orr Formation ___1974b [1975], Preliminary geologic map of The Barn quadrangle, Sneakover Limestone Member Millard County, Utah: U.S. Geological Survey Miscellaneous 2. Limestone, medium-gray to medium-dark- Field Studies Map MF-633. gray, thin-bedded, silty, with wavy par­ ___1974c [1975], Preliminary geologic map of the Conger Moun­ tings; forms ledges and slopes. Para- tain quadrangle, Millard County, Utah: U.S. Geological Survey bolinoides common in thin beds 16 m Miscellaneous Field Studies Map MF-634. below top ...... 23.8 78 ___1974d [1975], Preliminary geologic map of the Crystal Peak 1. Limestone, light- to medium-dark-gray, quadrangle, Millard County, Utah: U.S. Geological Survey coarse-crystalline in basal 4 m, fine- Miscellaneous Field Studies Map MF-635. crystalline above. Weathers to form ___1974e [1975], Preliminary geologic map of the Wah Wah Sum­ marker horizon of light-gray ledges made mit quadrangle, Millard and Beaver Counties, Utah: U.S. of large rectangular blocks. Contains Geological Survey Miscellaneous Field Studies Map MF-637. Elvinia identified by A. R. Palmer 15.2 50 ___1980a, Preliminary geologic map of the Fish Springs NW and Total thickness of Sneakover Fish Springs SW quadrangles, Juab and Tooele Counties, Utah: Limestone Member ...... 39.0 128 U.S. Geological Survey Miscellaneous Field Studies Map MF-1148. ___1980b, Preliminary geologic map of the Sand Pass NW REFERENCES CITED quadrangle, Juab County, Utah: U.S. Geological Survey Miscel­ laneous Field Studies Map MF-1149. ___1982, Ibexian Series (Lower Ordovician) type section, western Barnes, V. E., and Bell, W. C. 1977, The Moore Hollow Group of cen­ Utah, U.S.A., p. 7-10. In Ross, R. J., Jr., and Bergstrom, S. M., tral Texas: Bureau of Economic Geology, University of Texas, eds., The Ordovician System in the United States: International Report of Investigations 88, 169 p., 9 pis. Union of Geological Sciences Publication No. 12, Ottawa, Ontario, Bell, W. C., and Ellinwood, H. L., 1962, Upper Franconian and lower Canada. Trempealeauan Cambrian trilobites and brachipods, Wilberns Hintze, L. F., and Palmer, A. R., 1976, Upper Cambrian Orr Formation, central Texas: Journal of Paleontology, v. 36, no. 3, Formation Its subdivisions and correlatives in western Utah: p. 385-423. U.S. Geological Survey Bulletin 1405-G, 25 p. Bick, K. F., 1966, Geology of the Deep Creek Mountains, Tooele and Hose, R. K., 1961, Physical characteristics of Upper Cambrian Juab Counties, Utah: Utah Geological and Mineralogical Survey Bulletin 77, 120 p. stromatolites in western Utah: U.S. Geological Survey Profes­ sional Paper 424-D, p. D245-D248. Campbell, J. A., 1976, Upper Cambrian stromatolitic biostrome, Clinetop Member of the Dotsero Formation, western Colorado: Kellogg, H. E., 1963, Paleozoic stratigraphy of the southern Egan Geological Society of America Bulletin, v. 87, p. 1331-1335. Range, Nevada: Geological Society of America Bulletin, v. 74, Cohenour, R. 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