Report N-File 731 32 B SI1 Dsu Qafy 43

Home , Idiognathodus, Kaibab Limestone, Neognathodus, Owenites (ammonite), Serpukhovian, Utah Geological Survey

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114°00' R 19 W R 18 W b b 40°30' R 17 W R 11 W R 10 W 45' R 16 W R 15 W 30' R 14 W R 13 W 15' R 12 W 113°00' Plate 2 UTAH GEOLOGICAL SURVEY Utah Geological Survey Open-File Report 731 a divison of Interim Geologic Map of the Bonneville Salt Flats Utah Department of Natural Resources and East Part of the Wendover 30' x 60' Quadrangles—Year 3

CORRELATION OF QUATERNARY GEOLOGIC UNITS GEOLOGIC SYMBOLS GEOLOGIC UNITS Depositional Environments

Contact Qal—Stream alluvium Til—Latitic intrusion Mass Mixed- Human- Ma Alluvial Spring Eolian Playa Lacustrine and Deltaic Movement Environment Derived Contact, approximately located, between upper and lower units of Qafy—Younger fan alluvium Tsd—Tuffaceous sandstone and tuff Guilmette Formation Qh Qh Qhe Qafo—Older fan alluvium Tid—Dacitic intrusions Channel of Old River Bed delta (map unit Qasd) + Qms Qmtc + + Qal Qafy Qai Qsm Qes Qei Qps Qpl Qel Qeas Qai—Alluvial silt ^t—Thaynes Formation HOLO- CENE Steeply-dipping normal fault – Dashed where approximately located, Qasd ? Qla 0.0117 + ? dotted where concealed; bar and ball on downthrown side Qasd—Alluvial sand of Old River Bed delta Pge Y Qlg Qls Qlf Qlgf Qlk —Gerster Formation ? ? G Normal fault, geophysical, gravity – Located from gravity data, Qsm

Upper —Spring and marsh deposits concealed and very approximately located; bar and ball on Ppy—Plympton Formation 0.129 downthrown side Qes—Eolian sand TERNA R Qafo Pm

OCENE —Murdock Mountain Formation $ $ $ $ $ ! ! $! ! ! ! ! ! Low-angle normal fault – Dashed where approximatley located, dotted CENOZOIC Qleo* Qei—Eolian silt Middle QU A Qlo where concealed; boxes on downthrown side Ppm—Phosphoria Formation, Meade Peak Member 0.774 ? *

PLEIS T Qps ? Fault? with unknown geometry and offset – Dashed where —Playa salt Ppg—Park City Formation, Grandeur Member ? ? approximately located, dotted where concealed; queried where Qlg—Lacustrine gravel Lower existence and location inferred Psd—Permian sandstone, dolomite and limestone 2.58 ? ? Thrust fault – Dashed where approximately located, dotted where Qls—Lacustrine sand Polf *subsurface only concealed; dotted and queried where existence and location inferred; —Oquirrh Group, limestone unit (Finger Ridge thrust sheet) +stacked unit only teeth on hanging wall; bar and ball where later normal movement Qlf—Lacustrine fine-grained deposits P*o?—Oquirrh Group, undivided? (Knolls thrust sheet?) Lineament – From aerial photo interpretation Qlgf—Lacustrine gravel and fine-grained deposits CORRELATION OF TERTIARY, MESOZOIC, AND PALEOZOIC GEOLOGIC UNITS Polk—Oquirrh Group, limestone and sandstone unit (Knolls and South Knolls thrust sheet) G Lineament, geophysical – Located from gravity data, concealed and Qlo Grassy Mountains, Western —Older lacustrine deposits [subsurface only] Silver Island Southern West Finger Ridge, very approximately located Mountains and Newfoundland Clive area East Finger Ridge, Cedar P*os—Oquirrh Group, sandstone and limestone unit (Calcite and Aragonite thrust sheets) Ma Knolls Floating Island Mountains Grayback Hills, Mountains x x x x Igneous dike (unit Tid) Qms—Landslide deposits Lone Mountain *osi—Oquirrh Group, sandstone and siltstone unit (Calcite and Aragonite thrust sheets) 2.58 Axial trace of anticline – Dashed where approximately located, dotted Qmtc—Talus and colluvium unconformity where concealed; arrow shows plunge *ol—Oquirrh Group, limestone unit (Calcite and Aragonite thrust sheets) ? ? ? Qla—Lacustrine and alluvial deposits, undivided Axial trace of overturned anticline − Dashed where approximately PLIOCENE ? *osc—Oquirrh Group, sandstone and siltstone unit (Cedar thrust sheet) 5.33 located, dotted where concealed, dotted and queried where existence Tra(Dg) Tsl Qleo—Older lacustrine and eolian deposits, undivided [subsurface only] and location is inferred *olc

NEOGENE —Oquirrh Group, limestone unit (Cedar thrust sheet) Axial trace of syncline – Dashed where approximately located, dotted Qh—Human disturbance Y ? ? ? Pofc—Oquirrh Group, Freeman Peak Formation and Curry Peak Formation, MIOCEN E where concealed, dotted and queried where existence and location is undivided (footwall of Cedar thrust sheet) TIA R 23.03 inferred Qhw—Waste management facilities Tls P*ps—Pequop Formation, Ferguson Mountain Formation and Strathearn Formation, undivided TE R CENOZOIC Axial trace of overturned syncline − Dotted where concealed Qhe—Evaporation ponds *e—Ely Limestone OLIGOCEN E Minor folds − anticline, overturned syncline Qpl—Playa mud over lacustrine fine-grained over lacustrine 33.9 ? ? 35? 38 and eolian deposits Tsd Tl Til Tid Lake Bonneville shorelines (Currey, 1982; Chen and Maloof, 2017; *Mdc—Diamond Peak Formation and Chainman Shale, undivided ALEOGENE 40 ? Qei/Qlf—Eolian silt over lacustrine fine-grained deposits P ? 40 this study) – Mj—Joana Limestone EOCENE B Bonneville shoreline 5213–5328 feet (1589–1624 m) Qei/Qlg—Eolian silt over lacustrine gravel 56.0 ? DSu—Undivided dolomite and limestone unconformity P Provo shoreline 4856–4925 feet (1480–1501 m) Qei/Qlk—Eolian silt over lacustrine carbonate deposits Dg S Stansbury shoreline ~4446–4500 feet (~1355–1372 m), dashed where —Guilmette Formation approximately located Qei/Qla—Eolian silt over lacustrine and alluvial deposits 247.2 Dsi—Simonson Dolomite Approximate area with no Lake Bonneville deposits in subsurface Qes/Qafy—Eolian sand over younger fan alluvium ^t (see Oviatt and others, 2020) Sl—Laketown Dolomite

Lower Qes/Qlg—Eolian sand over lacustrine gravel TS TRIASSIC MESOZOIC Earthen dike for evaporation ponds Oes—Ely Springs Dolomite 251.9 AU L Qes/Qlf—Eolian sand over lacustrine fine-grained deposits u. unconformity Sedimentary bedding attitude – Oe T —Eureka Quartzite T 20 Qes/Qlgf—Eolian sand over lacustrine gravel and fine-

AU L Inclined _np AU L Pge grained deposits —Notch Peak Formation Inclined, photo interpreted Qes/Qla—Eolian sand over lacustrine and alluvial deposits

middl e Pm _ou—Orr Formation, upper part Vertical Qes/Qafo

PERMIAN —Eolian sand over older alluvial-fan deposits ? Ppm Ppy 50 Overturned Qes/*osc—Eolian sand over Oquirrh Group, Ppg Ppg AND CALCITE THRUST F CEDAR THRUST F CLIVE THRUST F sandstone and siltstone unit (Cedar thrust sheet) ? TS Mine or quarry Qel/*ol AU L Psd —Eolian and lacustrine deposits over Oquirrh Group, lower Psd Psd ? Sand and gravel pit limestone unit (Aragonite thrust sheet) P*ps Pofc Polk Polf P*os ARAGONITE BC1 Qel/*osc 299 Œ Sediment core and label (see table 1) —Eolian and lacustrine deposits over Oquirrh Group, *osi *osc sandstone and siltstone unit (Cedar thrust sheet) šC5-5 Sediment pit/trench and label (see table 1) ? ? Qel/*olc—Eolian and lacustrine deposits over Oquirrh Group, Uppe r unconformity P*o? unconformity? Lozenge unconformity Žsection Sediment natural exposure and label (see table 1) – adjacent map area limestone unit (Cedar thrust sheet) ?

ANIAN Qlg/Tl—Lacustrine gravel over latite lava flows

V tDH1 Hydrocarbon exploration well and label – Dry hole (see table 3) L *ol *olc Qeas/Qpl—Eolian and alluvial sand over playa mud over lacustrine *e 2,C Middle Geochemical and geochronology samples, and label (see tables 4, 5) ’ fine grained over older lacustrine deposits ALEOZOIC AND FINGER RIDGE THRUST F

P ? PENNSY ? ? BW2 ‘ Geochemical sample and label (see table 4) Tsl—Salt Lake Formation ‹ BW14 Fossil sample and label (see table 6) KNOLLS Lower Tra(Dg)—Rock avalanche breccia of Guilmette Formation 323 Qei/Qlf Stacked unit – Indicates thin cover of first unit overlying second unit *Mdc Tls—Tertiary limestone

Upper Tl—Latite lava flows MISS. Mj Lowe r ? See booklet for geologic unit descriptions, 359 Note - Duplicated queried units not included here MDp U.

. acknowledgments, references, figures, and tables. Dg DSu DE V Middle Dsi ? L. unconformity 419 ? Sl Sl SIL. 444 Oes Oes U.

ORD. Oe

O L.+M. 485 _np

upper _ou m. CAMBRIAN _ l.

? . 541 N adjacent map area

Boundary ages from International Chronostratigraphic Chart v2020/01. Informal subdivisions of Permian and Cambrian are used.

LITHOLOGIC COLUMN LITHOLOGIC COLUMN LITHOLOGIC COLUMN LITHOLOGIC COLUMN

Silver Island Mountains and Floating Island Finger Ridge thrust sheet Grassy Mountains, Finger Ridge, Grayback Hills, Lone Mountain Western Cedar Mountains (Aragonite and Calcite thrust sheets) (Cedar thrust sheet) CHRONO- STRATI- GEOLOGIC MAP THICKNESS LITHOLOGY / NOTES CHRONO- CHRONO- UNIT SYMBOL Feet (Meters) GRAPHIC STRATI- GEOLOGIC MAP THICKNESS LITHOLOGY / NOTES CHRONO- STRATI- GEOLOGIC MAP THICKNESS LITHOLOGY / NOTES UNIT GRAPHIC UNIT SYMBOL Feet (Meters) STRATI- GEOLOGIC MAP THICKNESS GRAPHIC UNIT SYMBOL Feet (Meters) LITHOLOGY / NOTES top not exposed UNIT GRAPHIC UNIT SYMBOL Feet (Meters) UNIT UNIT Pequop Aragonite and Calcite? thrust faults

T. Tsl

Formation, Plio? –Mio? Salt Lake Fm. 2550+ limestone 1182+ Schwagerina 20+ (6+) Ferguson Mtn P*ps Polf lower (365+) unit (360+) Streptognathodus lower

PERMIAN Fm, S. tersa PERMIAN

T . Tls

Plio? –Eo? Tert. limestone 20 (6) Strathearn Fm sandstone ? Oquirrh Group and *osc 1400± U. (425±) Unconformity Finger Ridge thrust fault Latite lava Tl 35+ (11+) Upper siltstone unit M . Ely 500+ *e Tuffaceous Limestone (150+) sandstone Tsd 307+ (94+) TERT. base not exposed Eocene and tuff PENN. Unconformity ? Unconformity? L.

not in contact and fault Ammonoids VANIAN Diamond commonly

U. Peak Fm, 200+ *Mdc Conodonts Chainman (60+) structurally Oquirrh Group limestone Shale thinned *olc 1900± Ammonoids PENNSY L unit MISS. LITHOLOGIC COLUMN (580±) L. Joana Ls Mj 0-130 (0-40) fossiliferous Thaynes Middle Knolls and South Knolls thrust sheets ^t 1930+ (590+) Pilot Formation

MDp Lower Shale adjacent map TRIASSIC area Cedar thrust fault

Upper Pofc ~400+ (~120+) CHRONO- PERM. l. O.G. stromatoporoids STRATI- GEOLOGIC MAP THICKNESS Guilmette 2230 LITHOLOGY / NOTES Dg coral and algal heads GRAPHIC UNIT SYMBOL Feet (Meters) Formation (680) UNIT Unconformity Gerster Fm Pge 311+ (95+) DEVONIAN Middle Simonson 1270 Dsi ? Dolomite (390) L. Unconformity Permian sandstone, Psd 1200+ Murdock Laketown dolomite (365+) Mountain Pm 1643 Sl 500+ (150+) middle SIL. Dolomite and Formation (500) Unconformity limestone Ely Springs Oes 200+ (60+) Dolomite Unconformity PRIMARY SOURCES OF GEOLOGIC MAPPING Upper Eureka Qtz Oe 100-200+ (30-60+) Schwagerina wellsensis Phosphoria Fm, 114°0' 113°0' Meade Peak CP Dol, WR Qtz S. frankinensis Member 1. Clark [UGS] and Oviatt [KSU] Ppm 233+ (71+) (2017-18), photogeologic and limited field mapping Lehman Fm e Crater Island Round Round Sally Pilot Peak Crater Island Lucin 4 SW Lucin 4 SE Big Pass Keller Well 2. Clark [UGS] and Oviatt [KSU] SW Mountain SW Mountain Mountain Kanosh Sh adjacent map area (2018-19), photogeologic and limited field mapping

ORDOVICIAN O 3. Clark [UGS] and Oviatt [KSU] Park City Fm, NV UT NEWFOUNDLAND MOUNTAINS 30' x 60' Lower Schwagerina Grandeur Ppg 1000± (300±) 41°0' (2019-20), photogeologic and limited field mapping Lower-Middl Pogonip Pseudofusulina Member YEAR 3 YEAR 1 4. Clark [UGS] and Page [DRI] (2020), mapping of ORB Group Paraschwagerina delta channels Schubertella Miners Silver Island Floating Floating Grassy Graham Knolls 2 NW Knolls 2 Finger Ridge Canyon Pass Island Island NE Mountains Clark [UGS] and Hardwick [UGS] (2020), mapping of Peak NE faults and lineaments from gravity data [Year 1-3 map Notch area] 1640 3,12 3 3,5 3,5 1,5,7,8 1,8 Peak _np (500) BONNEVILLE SALT FLATS 30' x 60' 5. Boden (2016) Formation limestone Polk 3300–5000+ ' lower and ' 6. Bowen and others (2018) (1000–1500+) Leppy Bonneville Floating Floating Grayback

PERMIAN sandstone Schwagerina Tetzlaff Peak Knolls 2 SW Knolls 2 SE Ripple Valley Low 7. Dames & Moore and others (1987) x 60 CS Sh Mbr unit Peak Racetrack Island SW Island SE Hills x 60 ' '

Oquirrh Group S. wellsensis JW Ls Mbr _ou 425+ (130+) Eoparafusulina 8. Doelling (1964) upper upper Permian 3,6,11,12 3,6 3,5 3,5 3,5 1,5,9 1,7,8,13,14 C Sh Mbr fossiliferous Psuedoschwagerina >850 to 3374+ 9. Doelling and others (1994) Schubertella sandstone, Psd PERMIAN Orr Fm Big Horse dolomite (>260 to 1029+) Ls Mbr YEAR 2 10. Maurer (1970) and OOELE 30

_ T limestone 11. Miller and others (in progress) Lamb Dol Wendover Silsbee Salduro Arinosa Arinosa NE Barro Knolls Aragonite Aragonite Hastings WENDOVER 30 NW Pass 12. Schaeffer (1960) 13. Solomon (1990) lower 3 3,6 3,5,6 3,5 3,5 3,4,5 2,4,5,7,13,14 2,4,5,7,13,14 1,7,10,13,14 14. Solomon (1993)

CAMBRIAN Toano _ adjacent map area Limestone Wendover middle Salduro SW Salduro SE Arinosa SW Arinosa SE Knolls SW Knolls SE Aragonite Aragonite Quincy Schwagerina SE SW SE Spring 3 3 3 3,4 3,4,5 3,4,5 2,4,5,7 2,4,5,7 2,10 40°30' Killian Springs WILDCAT MOUNTAIN 30' x 60' Formation Elephant Elephant Wildcat Wig Wig Gold Hill 1 Gold Hill 1 Wildcat Ferguson Flat Knoll Knoll Mountain Mountain Mountain Tabbys Peak NW NE Mountain NW NE NW NW NE sandstone _ Knolls thrust fault and P*os 1500–9004 lower Prospect limestone (460–2754) Mountain unit Quartzite Mesogondolella Sweetognathodus Psuedoschwagerina ? NEO. LITHOLOGIC COLUMN Clive thrust sheet Triticites

LITHOLOGIC COLUMN Oquirrh Group CHRONO- Southern Newfoundland Mountains STRATI- GEOLOGIC THICKNESS MAP LITHOLOGY / NOTES GRAPHIC UNIT SYMBOL Feet (Meters) sandstone and 1934–2500 UNIT *osi CHRONO- siltstone (590–760) GEOLOGIC MAP THICKNESS LITHOLOGY / NOTES STRATI- Knolls thrust fault unit UNIT SYMBOL Feet (Meters) ? GRAPHIC Triticites UNIT Plympton N. sulcoplicatus Formation Ppy 200+ (60+) Upper

top not exposed VANIAN Guilmette Unconformity Fm Park City Fm, Ppg 850+ (260+) Grandeur Fusulina Member PENNSY L limestone 2300+ unit *ol 1607+ (490+) Simonson DSu

(700+) lower

DEVONIAN Dol PERMIAN

Middle Neognathodus Lone Permian Idiognathodus Mtn sandstone, Aragonite, Calcite and other thrust faults undivided dolomite and limestone Psd 850+ (260+) Dol? Unconformity? dolomite and

SIL. Laketown Sl 850 (260) limestone Dolomite Unconformity Ely Springs U. Oes ~590 (180) base not exposed Clive thrust fault

ORD. Dolomite INTERIM GEOLOGIC MAP OF THE BONNEVILLE SALT FLATS AND EAST PART OF THE WENDOVER 30' X 60' QUADRANGLES,TOOELE COUNTY, UTAH—YEAR 3

Donald L. Clark 1, Charles G. Oviatt 2, Christian L. Hardwick 1, and David Page 3

1 Utah Geological Survey, Salt Lake City, Utah 2 Emeritus, Department of Geology, Kansas State University, Manhattan, Kansas 3 Desert Research Institute, Reno, Nevada

Suggested citation: Clark, D.L., Oviatt, C.G., Hardwick, C.L., and Page, D., 2020, Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3: Utah Geological Survey Open-File Report 731, 30 p., 2 plates, scale 1:62.500, https://doi.org/10.34191/OFR-731.

Disclaimer

This open-file release makes information available to the public during the review and production period necessary for aformalUGS publication. The map may be incomplete, and inconsistencies, errors, and omissions have not been resolved. The map may not conform to UGS policy and editorial standards and it may be premature for an individual or group to take actions based on its contents. Although this product represents the work of professional scientists, the Utah Department of Natural Resources, Utah Geological Survey, makes no warranty, expressed or implied, regarding its suitability for a particular use. The Utah Department of Natural Resources, Utah Geological Survey, shall not be liable under any circumstances for any direct, indirect, special, incidental, or consequential damages with respect to claims by users of this product. Geology intended for use at 1:62,500 scale.

This geologic map was funded by the Utah Geological Survey and the U.S. Geological Survey, National Cooperative Geologic Mapping Program through USGS STATEMAP award numbers G17AC00266 (2017–18), G18AC00202 (2018–2019), and G19AC00228 (2019–20). The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. This map and explanatory information are submitted for publication with the understanding that the U.S. Government is authorized to reproduce and distribute reprints for governmental use.

OPEN-FILE REPORT 731 UTAH GEOLOGICAL SURVEY a division of UTAH DEPARTMENT OF NATURAL RESOURCES 2020 Blank pages are intentional for printing purposes. INTRODUCTION

The Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles extend along the Interstate highway 80 (I-80) cor- ridor in northwestern Tooele County, northwest Utah (figure 1). The map area is in the eastern Basin and Range Province; on the west it includes the city of Wendover, the Leppy Hills, Silver Island Mountains, Floating Island, Pilot Valley, and a small part of the Pilot Range; on the east are the Grassy Mountains, Grassy Ridge, Finger Ridge, Grayback Hills, Thumb Ridge, other low hills, Ripple Valley, Lone Mountain (informal name after Maurer, 1970), and a small part of the western Cedar Mountains; the central part includes the Great Salt Lake Desert and southern tip of the Newfoundland Mountains (figure 1). Part of the desert includes the Bonneville Salt Flats, a salt pan known for vehicular land speed records at the Bonneville Speedway. Most of the map area is public land (Federal and State administered) and restricted-access military land (U.S. Air Force ranges, also known as UTTR—Utah Test and Training Ranges). Smaller areas of private land are used for waste management and potash extraction.

This geologic map is part of an ongoing effort by the Utah Geological Survey (UGS) to map the geology of the state of Utah at an intermediate scale (see Willis, 2017). This map displays three years of work on a multi-year project to map the geology of the Bonneville Salt Flats 30' x 60' quadrangle and the Utah part of the Wendover 30' x 60' quadrangle at 1:62,500 scale (plate 1, figure 1). The map explanation includes a booklet containing geologic unit descriptions, acknowledgments, references, figures and tables, and also includes plate 2 showing primary sources of geologic mapping, geologic units, unit correlations, lithologic columns, and geologic symbols.

Map data were compiled from several prior sources and new mapping has been added (see plate 2, mapping sources). Clark compiled and mapped the bedrock and surficial-deposit (Quaternary) geology with assistance from Oviatt. Hardwick compiled geophysical gravity data and assisted with interpretation (details below). Page provided some of the delta distributary channel mapping data. We extended intermediate-scale geologic mapping from adjacent areas including Dugway Proving Ground and UTTR South (Clark and others, 2016), Rush Valley 30' x 60' quadrangle (Clark and others, 2012, in preparation), Tooele 30' x 60' quadrangle (Clark and others, 2017, in press), and Newfoundland Mountains 30' x 60' quadrangle and adjacent Wells strip in Utah (Miller and others, in press). This map updates prior, less detailed (1:250,000 scale) geologic maps by Stokes (1963) and Moore and Sorensen (1979). Additional revisions to this map could occur in subsequent years of the project. Future work will involve collaboration with U.S. Geological Survey (USGS) geoscientists who mapped the geology of the Silver Island Mountains and adjacent areas in the northwestern part of the map area.

Hardwick compiled gravity data for this map area from the Pan-American Center for Earth and Environmental Studies (PAC- ES) (2012) and from the UGS (collected 2011–2014 with a Scintrex CG-5 autograv gravimeter and high-precision GPS survey units [vertical resolution 0.1 m or better]) (UGS, unpublished data). The computed final data values are Complete Bouguer Gravity Anomaly (CBGA) calculated using a reduction density of 2.76 g/cm3 (average crustal density). Principal gravity values from PACES data were checked against UGS GPS survey data and Shuttle Radar Topography Mission (SRTM) elevations (vertical resolution 3.53 m, horizontal grid size 90 m) for errors. Suspect PACES data were either adjusted for gravity anomaly corrections (Free Air, Bouguer Slab, Zone Terrain) or removed before recomputing CBGA in order to mesh the legacy PACES data with the modern UGS data. The final data were gridded in ArcGIS Pro for both small-cell and large-cell formats using Inverse Distance Weighting (power of 2). CBGA contours of 1 milliGal (mGal) were generated in ARCGIS Pro and “bullseye” contours were removed for closed areas of contours under 4 kilometers (2.5 miles) in circumference and with less than three data points (suspect data excluded). A substantial area of the Utah Test and Training Range (UTTR) South is lacking gravity coverage due to access restrictions while some areas with less dense data exist on the UTTR North. The composite CBGA raster and contour data were used for viewing and interpreting the gravity field data. Clark and Hardwick placed faults at “half max” locations between high and low contours and extended them into areas of less dense data. An east-west-trending gravity lineament was also mapped in the gravity data characterized by a series of saddles and lows. The gravity anomaly data appear to generally fit well with observations of the surface geology and topography, and respective density values. We also consulted reports by Smith and others (2011, 2012). On the UTTR, however, subsurface geologic control is generally poor over much of the map area. Three faults were extended south from the Newfoundland Mountains 30' x 60' quadrangle in an area of sparse gravity data.

Part of a proprietary 2D seismic line for hydrocarbon exploration (E-SOH-NUL81-1D) was present in the map area. The line runs from near the central Bonneville Salt Flats to the northern Stansbury Mountains in an east-southeast direction. R.W. Keach II (UGS) contacted Seismic Exchange Inc. in Denver, Colorado, to view a small portion of the line, which was determined to be of poor quality.

2 Utah Geological Survey

DESCRIPTION OF GEOLOGIC UNITS

QUATERNARY SURFICIAL DEPOSITS

See tables 1 and 2 and Oviatt and others (2020) for sediment and tephrochronology data on surficial deposits in the map area.

Alluvial Deposits

Qal Stream alluvium (Holocene) – Primarily clay, silt, and sand with some gravel lenses deposited by streams in channels, but in mountain valleys (Silver Island, Grassy and western Cedar Mountains) deposits are coarser grained and associated with more colluvium; locally merges with alluvial-fan deposits; locally includes alluvial-fan, colluvial, low-level terrace, lacustrine, and eolian deposits; thickness generally less than about 20 feet (6 m).

Qafy Younger fan alluvium, post-Lake Bonneville (Holocene to uppermost Pleistocene) – Poorly sorted gravel, sand, silt, and clay; deposited by streams, debris flows, and debris floods on alluvial fans and in mountain valleys; includes alluvium and colluvium in mountain valleys; locally grades into unit Qal and also unit Qai in lacustrine lagoons; may include small areas of lacustrine fine-grained deposits below the Bonneville shoreline; includes active and inactive fans younger than Lake Bonneville, but may include older alluvial deposits above the Bonneville shoreline; locally includes eolian silt and sand cover commonly less than 6 feet (2 m) thick; locally, unit Qafy spreads out on lake ter- races and, due to limitations of map scale, is shown to abut Lake Bonneville shorelines even though it is not cut by these shorelines; Qafy also locally drapes over, but does not completely conceal shorelines; thickness variable, up to 50 feet (15 m) or more.

Qafo Older fan alluvium, pre-Lake Bonneville (upper to middle? Pleistocene) – Small area near Silver Island Canyon on northwest map border of poorly sorted gravel, sand, silt, and clay; similar to unit Qafy, but locally consolidated with carbonate and forms higher-level incised deposits located above the high-stand of Lake Bonneville and locally etched by the lake; Qafo fans are incised by younger alluvial deposits; also mapped as stacked unit Qes/Qafo; thickness as much as 100 feet (30 m).

Qai Alluvial silt (Holocene to upper Pleistocene?) – Silt, clay, some sand, and minor gravel deposited by streams and sheet wash in former lagoons related to Lake Bonneville shorelines; locally, bottom of lagoonal basins may include exposed or unexposed, thin, fine-grained lacustrine deposits; thickness less than about 20 feet (6 m).

Qasd Alluvial sand of Old River Bed delta (lower Holocene to uppermost Pleistocene) – Sand and silt, locally with gravel and mud, present in numerous, commonly interweaving, distributary channels that extend northward on mudflats between the Old River Bed and the southern Great Salt Lake Desert (see Madsen and others, 2015; Clark and others, 2016); channels are locally exposed due to deflation of mudflat surfaces; selected channels were mapped to show their geographic distribution, and are depicted solely as green lines on plate 1; unit Qasd is probably related to continued Sevier-basin overflow and to groundwater discharge following the decline of Lake Bonneville; ages of 8800 to 11,400 14C yr B.P. (about 10,000 to 13,000 cal yr B.P.) (Oviatt and others, 2003; Madsen and others, 2015); thickness to about 3 feet (1 m).

Spring Deposits

Qsm Spring and marsh deposits (Holocene) – Clay, silt, and sand that is variably organic-rich, calcareous, or saline; present in ephemerally or perennially saturated (marshy) areas near springs and seeps; form extensive areas mapped near Blue Lake; thickness 0 to about 10 feet (0–3 m).

Eolian Deposits

Qes, Qes?

Eolian sand (Holocene) – Windblown sand, silt and mud pellets in dunes and sheets; bedding is variable from laminated to thin, with abundant cross-bedding; includes well-sorted, fine to very fine grained quartz sand, and also coarse to very fine grained sand of variable composition including gypsum, ooids, carbonate lumps, and shell fragments (gas- tropods and ostracodes); some gypsum compositions are reported to be as much as 60 percent (Jones, 1953; Boden, Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 3

2016); we noted the dune sand composition in several locations was variable and did not map gypsum or quartz dunes separately for this project; Miller and others (in press) mapped sand dunes and sheets composed of mud pellets along the margin of the southern Newfoundland Mountains; a local source of sand for Qes accumulations is the Old River Bed delta channel system (see unit Qasd); several prior reports noted eolian sand dunes of the Great Salt Lake Desert area (Nolan, 1927; Jones, 1953; Eardley, 1962; Doelling, 1964; Stifel, 1964; Dean, 1976, 1978; Doelling and others, 1994; Boden, 2016); grades into unit Qei; Qes locally forms thin cover on map units (see stacked units), only thicker deposits mapped as unit Qes; as much as 90 feet (25 m) thick.

Qei, Qei?

Eolian silt (Holocene) – A few areas of windblown silt with minor clay and fine sand that is locally oolitic;Qei occurs extensively as sheets that typically cover lacustrine and alluvial deposits and some bedrock in stacked units and locally as low dunes; additionally forms thin, unmapped cover on several map units; thickness as much as 10 feet (3 m).

Playa Deposits

Qps Playa salt (Holocene) – The salt crust at Bonneville Salt Flats composed of interbedded halite (36%) and gypsum sand (64%); salt crust is white to light gray brown and is hard to brittle to plastic depending on water content; lateral extent and thickness of salt crust is continually changing due to flooding, evaporation and dessication (FED) cycles (Bowen and others, 2017); mapped extent of salt crust is from September 7, 2016 data (figure 4, Bowen and others, 2018), note the boundary of crystalline salt historically extended onto and adjacent to the potash production facility area south of Salduro (Gwynn, 1996); salt crust is underlain by pre-Lake Bonneville carbonate mud (Bowen and others, 2018; Oviatt and others, 2020; Bernau and Bowen, in prep.); unit Qps thickness from 0 to 5 feet (0–1.5 m) based on five salt crust thickness studies since 1960 (see recent studies by White and Terrazas, 2006 and Bowen and others, 2018).

Qp Playa mud (Holocene) – Mapped solely as stacked unit Qpl (see description below).

Lacustrine and Deltaic Deposits (Lake Bonneville)

See figure 2 for a simplified hydrograph and chronology of Lake Bonneville. Currey (1982) and Chen and Maloof (2017) provided shoreline elevation data, and Oviatt estimated Stansbury shoreline elevations using Google Earth® (see plate 2). Lake Bonneville was succeeded by a lake during the Gilbert episode (figure 2), but these deposits are localized, generally thin, and difficult to recognize. Other post-Bonneville lakes that were high enough to flood into the Great Salt Lake Desert basin from Great Salt Lake (threshold elevation ~4217 feet [1286 m]) are not dated, did not last long, and did not leave an obvious sedimentary record.

Qlg, Qlg?

Lacustrine gravel (lowermost Holocene to upper Pleistocene) – Sandy gravel to boulders composed of rock fragments deposited in shore zones of Lake Bonneville; clasts are typically well rounded and sorted; locally calcareous tufa-cemented and draped on bedrock (especially at the Provo shoreline, figure 2); includes both transgressive and regressive lake phase gravels; may include small areas of lacustrine sand and fines, eolian and pre-Lake Bonneville deposits; thinner deposits on bedrock are not mapped; thickness variable, up to 100 feet (30 m) or more.

Qls Lacustrine sand (lowermost Holocene to upper Pleistocene) – Lacustrine sand in two areas; one area of carbonate- coated sand, carbonate lumps and few pebbles in barrier below the Stansbury shoreline zone on south Grassy Moun- tains piedmont; a second area in a cove below the Provo shoreline at the eastern Grassy Mountains; may include small areas of lacustrine gravel and finer-grained material, and eolian sand and silt; thickness to 80 feet (25 m) or more.

Qlf Lacustrine fine-grained deposits (lowermost Holocene to upper Pleistocene) – Sand, silt, marl, and calcareous clay; thin to very thick bedded; may include ostracode- and gastropod-rich layers; locally includes small areas of sand or sand and gravel; Doelling (1964) reported diatomaceous marl in Ripple Valley and Puddle Valley and referred to an area as “Diatom Gulch” (sections 17–20, T. 3 N., R. 10 W.); a great variety of diatoms were identified by A.P. Setty from section 29, T. 1 N., R. 10 W., and Doelling (1964) also did microscopic examinations of samples from seven locations; unit Qlf locally includes the white marl of Gilbert (1890); locally can include thin eolian silt and sand deposits at surface; thickness as much as 60 feet (20 m) or more. 4 Utah Geological Survey

Qlgf Lacustrine gravel and fine-grained deposits (lowermost Holocene to upper Pleistocene) – Lake Bonneville deposits with mixed grain sizes; see Qlg, Qls, Qlf unit descriptions above; may include small areas of eolian and pre-Lake Bonneville deposits, as well as bedrock; thickness up to 100 feet (30 m) or more.

Qlk Lacustrine carbonate deposits (lowermost Holocene? to upper Pleistocene?) – Mapped solely as stacked unit Qei/Qlk.

Lacustrine Deposits (Pre-Lake Bonneville)

Qlo Older lacustrine deposits (middle and lower Pleistocene) – Subsurface only and lower part of stacked unit Qpl, also see unit Qleo; white to pale yellowish gray to gray carbonate mud; oolitic sand and mud; uncommon thin layers of gypsiferous sand; Qlo contains lacustrine ostracodes solely of Limnocythere staplini, which are not typical of the ostracode faunal succession reported in Lake Bonneville deposits (see Oviatt, 2017); unit Qlo was observed in the Knolls and Wendover cores, and in cores from the Bonneville Salt Flats area and in other shallow cores and pits examined for this project (table 1; Oviatt and others, 2020; Bernau and Bowen, 2018a, 2018b, in prep.); the entire Wendover core consists of Qlo; most of the Knolls core consists of Qlo, except for the Bonneville marl in the uppermost meter or two (the basal contact of Bonneville marl in the remnants of the Knolls core is not well defined) (Shuey, 1971; Oviatt and Thompson, July 25, 1995, unpublished evaluation of Knolls and Wendover cores; Oviatt, 2017; Oviatt, and others, 2020); Williams (1994) reported three ash beds from the Knolls core ranging in estimated age from about 0.2 Ma (undated ash, but possible age of about 0.2 Ma) to approximately 0.9 Ma, and five ash beds in the Wendover core that range in estimated age from about 0.17 Ma to about 1.15 Ma (table 2); pollen analyses for samples from the Knolls and Wendover cores were published in Martin and Mehringer (1965) and Davis (2002); Shuey (1971) conducted paleomagnetic studies of both the Wendover and Knolls cores; unit Qlo may overlie Pliocene? deposits, Pliocene- Miocene Salt Lake Formation, and other Tertiary rock units (noted in two drill holes near Salduro rail siding; table 3); incomplete thickness is greater than 560 feet (170 m) in the Wendover core, and greater than 495 feet (151 m) in the Knolls core (Oviatt and Thompson, July 25, 1995, unpublished evaluation of Wendover and Knolls cores).

Mass-Movement Deposits

Qms Landslide deposits (Holocene to uppermost Pleistocene?) – Two relatively small deposits in northern Silver Island Mountains and western Grassy Mountains; deposits on steeper slopes with poorly sorted, clay- to boulder-size debris, and displaced bedrock blocks; generally characterized by hummocky topography, main and internal scarps, and chaotic bedding in displaced bedrock; age and stability determinations require detailed geotechnical investigations; thickness highly variable.

Qmtc Talus and colluvium (Holocene to uppermost Pleistocene?) – One area of mixed talus and colluvium on the steep north side of Guilmette exposure near the Bonneville shoreline, Silver Island Mountains; thickness probably less than 15 feet (5 m).

Mixed-Environment Deposits

Qla, Qla?

Lacustrine and alluvial deposits, undivided (Holocene to upper Pleistocene) – Sand, gravel, silt, and clay; consists of alluvial deposits reworked by Lake Bonneville, lacustrine deposits reworked by streams and covered by slopewash and alluvial fans, as well as alluvial and lacustrine deposits that cannot be readily differentiated at map scale; grades into other lacustrine and alluvial deposits; near Lone Mountain unit Qla is sandier than typical gravelly piedmont deposits, probably due to source material; thickness locally exceeds 30 feet (10 m).

Qel Eolian and lacustrine deposits, undivided (Holocene to upper Pleistocene) – Mapped solely as stacked units Qel/*ol, Qel/*osc and Qel/*olc.

Qleo Older lacustrine and eolian deposits, undivided (pre-Lake Bonneville) (Pleistocene) – Subsurface only, also see unit Qlo; lacustrine deposits include white to gray carbonate mud (locally laminated), oolitic sand, sandy mud, and pebbly sand; eolian deposits include fine sand, sandy mud, and paleosols, characterized in part by pale reddish to pale yellowish colors; unit Qleo was observed in the Clive area, and may be present in much of the low-lying areas east of the mudflats, east and west of the Grayback Hills and west of the Grassy Mountains, between Knolls and the Cedar Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 5

Mountains, and north of the Grayback Hills and west of the Grassy Mountains; Qleo was encountered in the Clive landfill pit walls (C5-5, C29-5) and sediment core BC1 (table 1; Oviatt and others, 2020); Qleo has not been dated except in a relative sense—the unit is older than overlying Lake Bonneville deposits; incomplete thickness is greater than 22 feet (6.7 m) in C29-5 and probably greater than 14 feet (4 m) in BC1 (Oviatt and others, 2020).

Qeas Eolian and alluvial sand (Holocene) – Mapped solely as stacked unit Qeas/Qpl.

Human-Derived Deposits

Qh Human disturbance (historical) – Deposits and disturbed areas from human development; includes sand and gravel and borrow pits, quarries, and developed areas on the former and current U.S. Air Force range (UTTR); more extensive waste management areas and evaporation ponds are mapped separately; thickness generally less than about 20 feet (6 m).

Qhw Waste management facilities (historical) – Deposits, disturbed areas, and borrow areas of waste management facilities within the West Desert Hazardous Industry Area (see Black and others, 1999); includes (1) Grassy Mountain landfill, located north of Knolls (hazardous waste, operated by Clean Harbors Environmental), and (2) Clive landfill (low-level radioactive and mixed hazardous and radioactive waste, operated by Energy Solutions) and adjacent U.S. Department of Energy Vitro Tailings disposal site; waste management area thicknesses are variable, but locally to as much as 65 feet (20 m) above ground at the Grassy Mountain facility, and 46 to 85 feet (14–26 m) (both below and above ground) at the Clive facility (Ed Costomiris and Charles Bishop, Utah Department of Environmental Quality, communications to Clark, 2018).

Qhe Evaporation ponds (historical) – Includes three evaporation system areas. First is an inactive pond system formerly operated by Amax (predecessor to Magcorp and US Magnesium) located north of Knolls; in the 1980s excess Great Salt Lake water was pumped via the West Desert pumping station (west of Lakeside) to the Newfoundland evaporation basin and subsequently transferred to the evaporation ponds—a series of diked areas used to concentrate magnesium minerals (salts) through solar evaporation (Jones and others, 2009; Tripp, 2009); second is a former potash production facility (Chloride Products Inc., 1921–1925) located south of the Arinosa rail siding (Gwynn, 1996); third is the active Intrepid Potash facility and historical operations of the Salduro salt marsh located southeast of Wendover; the Intrepid facility (2004 to present) extracts brine from wells and trenches, transports the brine to their solar evaporation pond system, and processes potassium chloride salts largely for agricultural fertilizer (Eric Rogers, Intrepid Potash Wendo- ver, verbal communication, October 11, 2019); prior potash production near Intrepid and farther east near Salduro was by several entities with attempts from about 1907 to the 1930s, but with consistent commercial production from 1939 to 2004 (Gwynn, 1996; Kipnis and Bowen, 2018); thickness is typically less than 6 feet (<2 m).

Stacked-Unit Deposits

Consists of thin surficial deposits covering underlying surficial deposit and bedrock geologic units. See each unit for descriptions. Thin unmapped cover materials may also be present on other geologic units throughout the map area.

Qpl Playa mud (post-Lake Bonneville) over lacustrine fine-grained deposits (Lake Bonneville) over older lacustrine (pre-Bonneville) deposits (Holocene over upper Pleistocene over unknown Pleistocene) – Unit consists of three stacked subunits that generally comprise the extensive mudflats of the Great Salt Lake Desert in the map area, defined through subsurface investigations; for simplicity unit symbol Qpl replaces typical stacked labels; upper playa deposits of silt, mud and calcareous mud (commonly mixed eolian, alluvial, and mudflat environments) covering lacustrine marl and fine-grained deposits of Lake Bonneville (unit Qlf), which collectively overlie pre-Bonneville deposits of lacustrine mud and sand (unit Qlo); playa deposits are locally saline or gypsiferous, grade laterally into thin alluvial mud, silt and sand along playa margins, and locally cover post-Lake Bonneville alluvial channels (unit Qasd); the Lake Bonneville fines Qlf( ) subunit was differentiated by lithologies and ostracode fauna (Oviatt and Thompson, July 25, 1995, unpublished evaluation of Knolls and Wendover cores; Oviatt and others, 2020); the pre-Bonneville subunit (Qlo) was differentiated by lithologies, ostracode fauna, and volcanic ashes (Williams, 1994; Oviatt and Thompson, July 25, 1995, unpublished evaluation of Knolls and Wendover cores; Oviatt and others, 2020); subsurface investigations indicate that Lake Bonneville deposits are absent from an area near the Bonneville Salt Flats (approximate area shown as orange dashed line on plate 1; Oviatt and others, 2020; Bernau and Bowen, 2018a, 2018b; in prep.); unit Qpl was mapped in adjacent areas as eolian and alluvial deposits over lacustrine fines (Clark and others, 2016) and playa 6 Utah Geological Survey

mud with fringing alluvial mud (Miller and others, in press); subunit thicknesses include playa mud from 0 to 2 feet (0-0.6m), Lake Bonneville marl and fines from 0 to 8 feet (0-2.4 m), and incomplete pre-Bonneville deposits exceed 560 feet (170 m) (Oviatt and Thompson, 1995, unpublished data on the Knolls and Wendover cores; Oviatt and others, 2020); unit Qpl thickness locally exceeds 560 feet (170 m).

Qei/Qlf

Eolian silt over lacustrine fine-grained deposits (Holocene over upper Pleistocene) – Eolian silt forming a mantle on fine-grained lacustrine deposits of Lake Bonneville and the Gilbert-episode lake; surface commonly contains distinctive vegetation stripes of uncertain origin (see Oviatt and others, 2003; West and Johnson, 2005); these distinctive stripes were called desert ripples by Ives (1946), and Doelling (1964) apparently named Ripple Valley for these features; may include some areas of eolian sand as thin sheets and low dunes; cover unit thickness is 1 to 4 feet (0.4–1.1 m) at the Clive landfill and near Knolls, and underlying unitQlf is 7 to 10 feet (2.2–3.1 m) at the Clive landfill (Oviatt, 2017; Oviatt and others, 2020).

Qei/Qlg

Eolian silt over lacustrine gravel (Holocene over upper Pleistocene) – Eolian silt forming a mantle on lacustrine gravel in German Valley (Grassy Mountains), near Clive, and near Thumb Ridge; cover unit thickness is highly variable, but possibly as much as 6 feet (2 m).

Qei/Qlk

Eolian silt over lacustrine carbonate deposits (Holocene over lowermost Holocene? to uppermost Pleistocene?) – Eolian silt on lacustrine deposits of carbonate chips in a matrix of silt and sand; poorly exposed, forms low mounds in a band on unit Qei/Qlf west of the Grayback Hills and Clive; unit is possibly related to the highstand of the Gilbert- episode lake, considering an elevation near 4250 to 4260 feet (1296–1299 m) (see Oviatt, 2014; see figure 2); Solomon (1993) and Doelling and others (1994) previously mapped as lacustrine sand; cover unit thickness is less than 3 feet (1 m), and Qlk thickness unknown, but up to 3 feet (1 m) exposed.

Qei/Qla

Eolian silt over lacustrine and alluvial deposits (Holocene over Holocene to upper Pleistocene) – Eolian silt forming a mantle on mixed alluvial and lacustrine deposits along lower margins of piedmont around Ripple Valley; cover unit thickness is highly variable, but possibly as much as 6 feet (2 m).

Qes/Qafy

Eolian sand over younger fan alluvium (Holocene over Holocene to uppermost Pleistocene) – Eolian sand and silt overlying younger fan deposits; mapped in a few areas where the eolian deposits generally obscure the surface texture of fans; cover unit thickness variably, but possibly as much as 6 feet (2 m).

Qes/Qlg

Eolian sand over lacustrine gravel (Holocene over upper Pleistocene) – Eolian sand and silt forming a mantle on lacustrine gravel of Lake Bonneville; cover unit thickness unknown, but possibly as much as 6 feet (2 m).

Qes/Qlf

Eolian sand over lacustrine fine-grained deposits (Holocene over upper Pleistocene) – Eolian sand and silt forming a mantle on lacustrine fines; also present in patchy sheets and dunes on unit Qlf, typically around perimeter of large Qes areas and leeward sides of valleys; cover unit thickness from 0 to as much as 6 feet (2 m).

Qes/Qlgf

Eolian sand over lacustrine gravel to fine-grained deposits (Holocene over upper Pleistocene) – Eolian sand and silt forming a mantle on Lake Bonneville lacustrine gravel to fines; cover unit thickness unknown, but possibly as much as 6 feet (2 m). Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 7

Qes/Qla, Qes/Qla?

Eolian sand over lacustrine and alluvial deposits (Holocene over upper Pleistocene) – Eolian sand forming a mantle on mixed lacustrine and alluvial deposits locally along the piedmont west of the Cedar Mountains, at the Knolls, and southern Newfoundland Mountains; cover unit thickness is highly variable, but possibly as much as 6 feet (2 m).

Qes/Qafo

Eolian sand over older alluvial-fan deposits (Holocene over upper to middle? Pleistocene) – Eolian sand forming a mantle on older alluvial-fan deposits along the piedmont west of the Cedar Mountains; cover unit thickness is highly variable, but possibly as much as 6 feet (2 m).

Qes/*osc

Eolian sand over Oquirrh Group, sandstone and siltstone unit (Cedar thrust sheet) (Holocene over Upper to Middle? Pennsylvanian) – One area of eolian sand and silt overlying bedrock unit on southeast margin of map area; cover unit thickness is variable, but possibly as much as 10 feet (3 m).

Qel/*ol

Eolian and lacustrine deposits over Oquirrh Group, limestone unit (Aragonite thrust sheet) (Holocene to upper Pleistocene over Upper Pennsylvanian) – One area of eolian sand and silt and Lake Bonneville lacustrine gravel and sand overlying bedrock unit near southeast corner of map area; cover unit thickness is variable, but possibly as much as 10 feet (3 m).

Qel/*osc

Eolian and lacustrine deposits over Oquirrh Group, sandstone and siltstone unit (Cedar thrust sheet) (Holocene to upper Pleistocene over Upper Pennsylvanian) – Eolian sand and silt and Lake Bonneville lacustrine gravel and sand overlying bedrock unit on southeast margin of map area; cover unit thickness is variable, but possibly as much as 10 feet (3 m).

Qel/*olc

Eolian and lacustrine deposits over Oquirrh Group, limestone unit (Cedar thrust sheet) (Holocene to upper Pleis- tocene over Middle Pennsylvanian?) – Eolian sand and silt and Lake Bonneville lacustrine gravel and sand overlying bedrock unit at southeast margin of map area; cover unit thickness is variable, but possibly as much as 10 feet (3 m).

Qlg/Tl Lacustrine gravel over latite lava flows (lowermost Holocene to upper Pleistocene over Eocene) – Mapped in one area south of Clive exit on I-80; Lake Bonneville lacustrine gravel forming a mantle on bedrock; typically includes an eolian silt veneer; cover unit thickness is variable, but possibly as much as 3 to 6 feet (1–2 m).

Qeas/Qpl

Eolian and alluvial sand over playa mud over lacustrine fine-grained over older lacustrine deposits (Holocene over lowermost Holocene to upper Pleistocene over Pleistocene) – Thin sheets of sand and silt deposited by wind, streams and sheet floods along the playa margin; includes areas of coppice dunes; locally present along the margins of the Silver Island Mountains and Floating Island; cover unit thickness uncertain, probably less than 3 feet (1 m).

TERTIARY (NEOGENE-PALEOGENE) ROCK UNITS See table 3 for data on subsurface rock units from hydrocarbon exploration wells.

Tsl, Tsl?

Salt Lake Formation (Pliocene to upper Miocene) – Two very small exposures of light-brownish-gray, tuffaceous sandstone (glassy) that is locally pebbly and conglomeratic; thin bedded; forms slopes in eastern and central Grassy Mountains; queried in small outcrop in higher Grassy Mountains; unit Tsl probably underlies pre-Lake Bonneville deposits (units Qlo and Qleo), and possibly younger Pliocene deposits, as a thick section in the subsurface of val- 8 Utah Geological Survey

leys as suggested by two exploration wells near Salduro siding (table 3); unit Tsl is locally exposed in the Silver Island Mountains (Miller and others, in progress); no direct age data in map area, regionally age of Salt Lake For- mation is Pliocene to upper Miocene (Oaks and others, 1999; Miller and others, 2020); incomplete thickness as much as 20 feet (6 m).

Tra(Dg)

Rock avalanche breccia of Guilmette Formation (Pliocene to upper Miocene) – Two areas of brecciated bedrock in the northern Silver Island Mountains interpreted as rock avalanche breccia from extensional tectonics; dark gray and brown breccia with locally distinguishable strata of Devonian Guilmette Formation; forms massive breccia sheets (locally pulverized rock) interlayered with nearly intact rock slabs exhibiting jigsaw fractures; Miller and others (in progress) noted rock avalanche breccia exposures in the Silver Island Mountains interbedded with Salt Lake Forma- tion conglomerate and tuff; thickness is variable, likely less than 200 feet (60 m).

Tls Tertiary limestone (Pliocene? to Eocene?) – Three small exposures of light grayish-brown lacustrine limestone; locally cherty or silicified; poorly bedded; present in Grassy Ridge overlying unit Psd near the Provo shoreline; Clark (this study) reevaluated exposures just south of the map area and found another exposure of unit Tls previously mapped as lacustrine tufa (see Clark and others, 2016); no direct age data, could be part of Salt Lake Formation, older Tertiary rocks, or Sevier “collapse” basin rocks (see Constenius, 1996; Hintze and Davis, 2003); thickness as much as 20 feet (6 m).

Volcanic Rocks of the Grayback Hills and Grassy Mountains Rock names are based on the geochemical classification of Le Bas and others (1986). See table 4 for geochemical data and table 5 for radiometric age data.

Tl Latite lava flows (Eocene) – Black, gray, grayish-brown, and grayish-red latite and latite porphyry lava flows; locally vesicular and flow banded; phenocrysts (10–15%) include (decreasing) calcic plagioclase, pyroxene, olivine, idding- site, and iron oxides; form extensive exposures in the Grayback Hills that have been modified by Lake Bonneville; geochemical data from Hogg (1972), Doelling and others (1994), and this study (table 4); Doelling and others (1994) called flows/unit trachyandesite; yielded K-Ar ages of 38.5 ± 0.6 Ma, whole rock (M. Best, Brigham Young Univer- sity, in Davies [1980]) and 39.1 ± 1.0 Ma on groundmass (Doelling and others, 1994; UGS and Krueger Enterprises, 2018) (table 5); thickness as much as 35 feet (11 m) (Doelling and others, 1994).

Til Latitic intrusion (Eocene) – A single neck or plug in the northwest Grayback Hills of latite that is medium to dark gray, weathering to reddish brown; flow banded; forms resistant exposure near outcrops of units Tsd and Tl; geochemical data from Doelling and others (1994) and this study (table 4); no direct age data, but likely of similar age to unit Tl; probable source vent of unit Tl; Doelling and others (1994) called unit trachyandesite and included it with the lava flows; width is about 250 feet (75 m).

Tsd Tuffaceous sandstone and tuff (Eocene) – Tuffaceous conglomeratic sandstone (80%) and interbedded dacitic airfall tuff (20%) in the northern Grayback Hills; light-gray tuffaceous sandstone is conglomeratic with clasts up to cobble size of limestone, siltstone, sandstone and chert; locally cross-bedded and contains channel bed forms; bedding is thin to medium; grayish-pink and yellowish-gray dacitic tuff is poorly bedded and interlayered with thin bands of reworked tuff; tuff is composed of clayey, mostly devitrified glass shards, quartz, mica, and subordinate feldspar and mafic minerals; few exposures near northern end of volcanic outcrops; geochemical data on dacite tuff from Doelling and others (1994) in table 4; K-Ar age of 38.6 ± 1.0 Ma on sanidine (Doelling and others, 1994; UGS and Krueger Enterprises, 2018), and 40Ar/39Ar total fusion on several plagioclase grains gave a much younger weighted mean age of about 35.5 Ma (M. Pringle, USGS, in Doelling and others, 1994) (table 5); unit Tsd appears to be interlayered with and underlies unit Tl, but unit Tl lacks the sanidine phenocrysts of unit Tsd; incomplete measured thickness is 307 feet (94 m) (Doelling and others, 1994).

Tid Dacitic intrusions (Eocene?) – Several dark-gray to black (weathers to reddish brown) porphyritic dacite to andesite dikes and pods in the western Grassy Mountains; phenocrysts (10–20%) include (decreasing abundance) plagioclase, pyroxene and iron oxides; form discontinuous outcrops trending north to northwest; new geochemical data in table 4; no direct age data, but possibly of similar age to unit Til; Doelling (1964) called these basalt porphyry dikes; width is 15 to 50 feet (5–15 m) (Doelling, 1964). Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 9

TRIASSIC TO PERMIAN ROCK UNITS

Triassic and Permian (Post-Oquirrh Group) Strata of the Calcite, Aragonite, Clive, Knolls and South Knolls Thrust Sheets See table 6 for selected fossil age data.

^t Thaynes Formation (Lower Triassic, Spathian-Smithian) – Upper part (southwest Grayback Hills) is yellowish- brown silty limestone and limestone (measured sections 1, 2, 3, 3A, 3B of Davies [1980]); middle part (northern Grayback Hills) is gray, finely crystalline limestone and some brown sandstone (measured section 4 of Davies [1980]); lower part (Thumb Ridge) is pale red, brown and gray, interbedded sandstone, limestone, shale, and siltstone (Thaynes unit and units 7 through 4 of Dinwoody Formation measured section of Doelling and others, 1994); thinly laminated to medium bedded; forms ledges, slopes, and cliffs; numerous fossils include ammonoids, conodonts, crinoids, echinoids, microgastropods, pelecypods, brachiopods, scaphopods?, and fragments of fish and sharks (Davies, 1980; Doelling and others, 1994); ammonoids and conodonts reported in table 6 indicate the upper part is upper Spathian substage, the middle part is lower Spathian, and the lower part is Smithian; lower contact was adjusted based on ammonoids, but no bed with Meekoceras was found to define the base (K. Bylund, independent researcher, email to Clark, Feb. 16, 2018; table 6); unconformably overlies the Gerster Formation at Thumb Ridge, but a tiny unmapped patch of intervening red beds (unit 2, Dinwoody measured section in Doelling and others, 1994) could possibly be tongue of Woodside Formation; incomplete thickness is about 1930 feet (590 m) (Davies, 1980; Doelling and others, 1994; this study), upper and lower contacts are not exposed.

Pge Gerster Formation (middle Permian) – Medium- to light-gray cherty limestone and chert; tan, light-gray, and light- blue-gray chert occurs as beds, nodules, blebs and stringers, some with brown weathering rinds; medium to very thick bedded; forms ledges on Thumb Ridge and east side of Finger Ridge; fossils include productid and spiriferid brachiopods, crinoid columnals, and shell fragments (Doelling, 1964; Doelling and others, 1994) that are not age diagnostic; regional age is Guadalupian (Wordian, global chronostratigraphy) (see Hintze and Kowallis, 2009; Wardlaw, 2015) [note for Permian units the chronostratigraphic scale has changed over time]; previously mapped as Gerster Limestone and part of Park City Group, undifferentiated by Doelling (1964); unit is also known as the Gerster Limestone (U.S. Geological Survey, 2019); incomplete measured thickness is 263 to 311 feet (80–95 m) (Doelling, 1964; Doelling and others, 1994), upper contact is not exposed; complete thickness is 1600 feet (485 m) in Terrace Mountain (McCarthy and Miller, 2002), 50 miles (80 km) to the northwest.

Pm, Pm?

Murdock Mountain Formation (middle Permian) – Light-gray cherty dolomite and limestone, and light-gray, blue-gray, gray-tan, and brown weathering bedded and nodular chert; bedding is typically medium; forms rubbly ledges that have commonly been modified by Lake Bonneville; locally contains poorly preserved brachiopods (Doelling, 1964; Doelling and others, 1994); regional age is Guadalupian (Wordian and Roadian, global chronostratigraphy) (see Hintze and Kowallis, 2009; Wardlaw, 2015); the Murdock Mountain Formation is a lateral cor- relative of the Plympton Formation and most of the Rex Chert (Wardlaw, 2015); previously mapped as Rex Chert and part of Park City Group, undifferentiated by Doelling (1964); complete thickness is 1643 feet (500 m) at Finger Ridge (Doelling, 1964); incomplete thickness is about 500 feet (150 m) at Thumb Ridge and northern Grayback Hills (Doelling and others, 1994).

Ppy, Ppy?

Plympton Formation (middle to lower Permian) – Light-olive-gray to yellowish-gray fossiliferous limestone and limestone that is locally cherty with medium to dark-gray and brown chert nodules; locally some minor bedded chert; fossil brachiopods typically abundant; lower part of formation (20 to 30 feet, 6–10 m) is dark grayish brown bedded and nodular chert with lesser medium dark brown dolomitic limestone; bedding is thin to thick, forming ledges and some cliffs; present in Clive thrust sheet where it overlies the Grandeur Formation with no intervening Meade Peak Member strata; the Plympton is Guadalupian (Wordian and Roadian, global chronostratigraphy) (see Hintze and Kow- allis, 2009; Wardlaw, 2015), but here extends into the lower Permian based on sample BW30 (table 6) from lower part of limestone which yielded conodont fossil Neostreptognathodus sulcoplicatus indicating a late to middle Leonardian (Kungurian to Late Artinskian, global chronostratigraphy) age (S.M. Ritter, Brigham Young Univ., email to Clark, Dec. 7, 2018); top of unit Ppy is eroded; incomplete thickness is about 200 feet (60 m). 10 Utah Geological Survey

Ppm, Ppm?

Phosphoria Formation, Meade Peak Member (middle and lower Permian) – Light-brown, pale-red, black and gray cherty dolomite, cherty siltstone, phosphatic dolomitic limestone, and chert; bedding is laminated to medium; forms rough ledges and slopes at Finger Ridge and Grassy Ridge, and not exposed in Grayback Hills- Thumb Ridge area but assumed present in subsurface (Doelling and others, 1994); regional age is Guadalupian and Leonardian (Roadian and Kungurian, global chronostratigraphy) (see Hintze and Kowallis, 2009; Wardlaw, 2015); Doelling (1964) called unit Meade Peak(?) Limestone of Park City Group, and part of Park City Group, undifferentiated; unit is also known as the Meade Peak Phosphatic Shale Member and Tongue (U.S. Geological Survey geologic lexicon, 2019); incomplete measured thickness is 233 feet (71 m) at Finger Ridge (Doelling, 1964), where upper part is not exposed.

Ppg, Ppg?

Park City Formation, Grandeur Member (lower Permian) – Light-gray-weathering dolomite, dolomitic limestone, and sandy limestone; light-gray to white chert is common as nodules, blebs, and sporadic thin beds; forms cliffy outcrops at Finger Ridge, Grassy Ridge, Lone Mountain, and queried in isolated knolls west of Thumb Ridge and in Ripple Valley; regional age is Leonardian (Kungurian, global chronostratigraphy) (see Hintze and Kowallis, 2009; Wardlaw, 2015); Doelling (1964) included as Grandeur Limestone in Park City Group, undifferentiated at Grassy Ridge; Clark uses terminology of Park City Formation rather than Group of some prior studies; UGS does not use Kaibab Limestone nomenclature in northwest Utah; incomplete thicknesses are estimated at 500 to over 1000 feet (150–300+ m) at the Grassy Mountains-Thumb Ridge area (Doelling, 1964; Doelling and others, 1994), 700 feet (215 m) at Lone Mountain (this study), and as much as 850 feet (260 m) in Clive thrust sheet (this study); elsewhere, complete thicknesses are 419 feet (128 m) in Cedar Mountains (Maurer, 1970) and 1838 feet (560 m) in Hogup Mountains (Stifel, 1964; Miller and others, in press).

Psd, Psd?

Permian sandstone, dolomite, and limestone (lower Permian, Leonardian) – Interbedded sandstone, dolomite, dolomitic limestone, and limestone; sandstone is orange-tan and light tan, fine grained, and locally cross-bedded; carbonate rocks are medium to dark gray and commonly cherty; medium to very thick bedded; forms ledges, cliffs and slopes in the Grassy Mountains, Lone Mountain, and hills southwest and south of Clive; fossils include Plagioglypta canna (mollusk, renamed Dentalium) and an unidentified pelecypod (Doelling, 1964); the Leonardian age is from bracketing strata and fusulinids (Parafusulina sp.) in the Cedar Mountains (sample D-77, Clark and others, 2016; Utah Geological Survey and Wells, 2017); Doelling (1964) reported the upper contact is gradational and difficult to separate from the Grandeur; previously mapped as “Unnamed” formation by Doelling (1964) and Maurer (1970); unit may correlate with the Pequop Formation and Loray? Formation and/or Arcturus Formation to the west and Diamond Creek Sandstone and Kirkman Formation to the east (Hintze and Kowal- lis, 2009; Clark and others, in press; Miller and others, in press; figure 3); incomplete measured thicknesses are 1463 and 3374 feet (446 and 1029 m) in Grassy Mountains (Doelling, 1964), and the unit is incomplete at Lone Mountain and as much as 900 feet (275 m) thick, up to 850 feet (260 m) in Clive thrust sheet, and about 1200 feet (365 m) thick at Knolls (this study); complete thickness is 3953 feet (1205 m) in the Cedar Mountains (Maurer, 1970); also likely present in the Hogup Mountains where thickness is uncertain (Stifel, 1964; Miller and others, in press).

PERMIAN TO PENNSYLVANIAN ROCK UNITS See figure 3 for a correlation diagram of Oquirrh Group/Formation and adjacent rock units.

Oquirrh Group Strata of the Finger Ridge Thrust Sheet

Polf Oquirrh Group, limestone unit (lower Permian, upper Wolfcampian) – Dark-gray limestone and dolomitic limestone and minor light-brown sandstone; limestone is locally cherty and fossiliferous; thick to very thick bedded; present in the hanging wall of the thrust fault at western Finger Ridge; Doelling (1964) reported these rocks contain fusulinid Schwagerina sp. that Bruce Lambson (Shell Oil paleontologist) stated is late early Wolfcampian in age (table 6); our sample BW21 yielded Schwagerina of late Wolfcampian (Lenoxian) age (table 6); incomplete measured thickness is 1182 feet (360 m) at western Finger Ridge (Doelling, 1964) with neither top nor bottom exposed. Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 11

Oquirrh Group Strata of the Knolls and South Knolls Thrust Sheets

P*o? Oquirrh Group, undivided? (lower Permian? to Middle Pennsylvanian?) – Possible Oquirrh Group rocks of Kittycat Mountain and adjacent area (see Stokes, 1963; Moore and Sorenson, 1979; Clark and others, 2016). Connection to Knolls and South Knolls thrust sheets uncertain. No access to this part of UTTR South for the current mapping project.

Polk Oquirrh Group, limestone and sandstone unit (lower Permian, Wolfcampian) – Consists of four parts; upper part is dark-gray coarse-grained limestone that is locally cherty, sandy and fossiliferous, and typically thick to very thick bedded; local interbeds of calcareous sandstone and thinner-bedded limestone; underlying part is medium to dark- gray sandy limestone with brown case hardening patches and interbeds of calcareous sandstone; black chert present in lenses; typically thin bedded; thin-bedded part not present in South Knolls thrust sheet; underlying part is dark-gray weathering to light and dark-brown calcareous sandstone and siltstone, lesser interbeds of medium-gray limestone and cherty limestone; laminated to medium bedded; lowermost part is medium to dark-gray limestone and sandy limestone with lesser interbeds of dark-gray weathering to light-brown calcareous sandstone; limestone is locally bioclastic; medium to very thick bedded; unit forms cliffs, ledges and slopes; three new fusulinid fossil samples (BW23, BW24, BW27) yielded a Wolfcampian age (table 6), but no biostratigraphic control from the lower part of the unit; base and locally top of unit Polk not exposed, incomplete thickness from 3300 to 5000 feet (1000–1500 m).

Oquirrh Group Strata of Grassy Mountains and Lone Mountain (Calcite and Aragonite Thrust Sheets) Modified from Doelling (1964) and Jordan (1979b) (see figure 3).

P*os, P*os?

Oquirrh Group, sandstone and limestone unit (lower Permian, Leonardian?-Wolfcampian to Upper Pennsylvanian, uppermost Virgilian) – Light- to dark-brown sandstone, gray calcareous sandstone that weathers to light and dark brown, and light- to dark-gray limestone and fossiliferous limestone that is locally siliceous; local intraformational conglomerate beds; medium to thick bedded, forms slopes and ledges; fossil fusulinids and conodonts (table 6) were reported to indicate an early Leonardian through early Wolfcampian age (Doelling, 1964; Jordan, 1979a, 1979b; this study); G.P. Wahlman (independent biostratigrapher, written communication to Clark, May 13, 2019) reevaluated the fusulinid data in Doelling (1964) and reported some issues including Triticites ranging too high in the section suggesting probable juvenaria of Wolfcampian Pseudoschwagerina, and the fusulinids listed as indicating lower Leonardian strata are ques- tionable; Wahlman also reported that the former early Wolfcampian interval (lower part of Doelling’s unit 3 and upper part of unit 2) is now transferred to the latest Virgilian “Bursumian/Newwellian” (see, for example, Wahlman, 2013; table 6); Clark (this study) reevaluated exposures just south of the map area on the Aragonite thrust sheet and found that fossil sample D-74 with Parafusulina (Leonardian) (Clark and others, 2016; Utah Geological Survey and Wells, 2017) appears to be from upper Oquirrh Group beds rather than from the overlying map unit; Doelling (1964) reported other fossils include crinoids, brachiopods, pelecypods, sponges, trilobites, and bryozoans; unit is queried in area northwest of Calcite thrust fault and probable backthrust where brecciated; unit P*os corresponds to Oquirrh Formation units 6, 5, 4, 3 and upper part of unit 2 of Doelling (1964); complete thickness is 7620 to 9004 feet (2323–2745 m) in Grassy Mountains (Doelling, 1964), but only 1500 feet (460 m) in Lone Mountain (this study) on a different thrust sheet.

*osi, *osi?

Oquirrh Group, sandstone and siltstone unit (Upper Pennsylvanian, Virgilian) – Light-brown, light-gray, and pale- red sandstone, calcareous sandstone and siltstone, and minor silty and sandy limestone; local intraformational conglomerate beds; south of Lone Mountain locally appears to contain a limestone interval 100 to 200 feet (30–60 m) thick; thin to medium bedded; forms slopes and few ledges; fossil fusulinids from lower part were reported to be of Virgilian age (Doelling, 1964; Jordan, 1979a, 1979b) (table 6); corresponds to Doelling’s (1964) Oquirrh Formation unit 2, excluding the upper part (272 feet, 83 m) of limestone that is here placed in unit P*os; unconformably overlies unit *ol (fossils indicate Missourian missing); queried near Puddle Valley where separation from unit P*os is difficult (see Doelling, 1964); complete thickness is 1934 feet (590 m) in Grassy Mountains (Doelling, 1964), and 2500 feet (760 m) in Lone Mountain (this study).

*ol, *ol?

Oquirrh Group, limestone unit (Middle and Lower? Pennsylvanian, Desmoinesian-Atokan?-Morrowan?) – Medium- gray limestone and cherty limestone with minor interbedded light-brown sandstone and calcareous sandstone; typi- 12 Utah Geological Survey

cally thick bedded, forming cliffs and ledges; fossil fusulinids and conodonts from the unit indicate a Desmoinesian to late Atokan? age (table 6), and Doelling (1964) noted that it is uncertain if the lower part of the unit might contain Atokan- or Morrowan-age strata; other fossils include brachiopods, corals, trilobites, and bryozoans (Doelling, 1964); corresponds to Oquirrh Formation, unit 1 of Doelling (1964); incomplete thickness is 1607 feet (490 m) in Grassy Mountains (Doelling, 1964), base is faulted; unknown thickness in Lone Mountain due to folding.

Oquirrh Group Strata of Western Cedar Mountains (Cedar Thrust Sheet)

*osc, *osc?

Oquirrh Group, sandstone and siltstone unit (Upper Pennsylvanian) – Medium- to dark-gray, weathering to yellowish-gray, calcareous sandstone, light-brown to pale-red to dark-gray, calcareous siltstone, minor medium- to dark- gray limestone, and light-brown to light-gray resistant quartzite at base; calcareous sandstone and siltstone contain worm trails; laminated to medium bedded; forms slopes and a few ledges; upper unit of Cedar thrust sheet overlies unit *olc, and unit *osc is overlain on the west by the Aragonite thrust sheet; fossil conodonts from upper part of unit indicate a Virgilian age (table 6); Maurer (1970) mapped as Oquirrh Formation unit 4 based on lithologies; probably unconformable with unit *olc below; incomplete thickness is roughly 1400 feet (425 m).

*olc Oquirrh Group, limestone unit (Middle Pennsylvanian?) – Medium- to dark-gray limestone and cherty limestone and lesser medium to dark-gray, weathering to yellowish-gray, calcareous sandstone and siltstone; medium to thick bedded; forms cliffs and ledges; lower unit of the Cedar thrust sheet; no useful fossil data yet for biostratigraphic control; Maurer (1970) mapped as Oquirrh Formation unit 3 based on lithologies; incomplete thickness is roughly 1900 feet (580 m).

Oquirrh Group Strata of Western Cedar Mountains (Footwall of Cedar Thrust Sheet)

Pofc Oquirrh Group, Freeman Peak Formation and Curry Peak Formation, undivided (lower Permian, Wolfcam- pian) – Combined unit in the northern Cedar Mountains; medium- to dark-gray, weathering to yellowish-gray, calcareous, fine-grained sandstone and siltstone with lesser interbedded very pale orange, medium-gray and pale-red quartz sandstone and orthoquartzite (particularly in upper part) and uncommon gray sandy limestone that is locally fossiliferous; laminated to thick-bedded unit typically breaks into chips and plates forming rounded hills and slopes with local ledges; worm trail markings common on bedding planes in lower part of unit; Wolfcampian fusulinids reported by Maurer (1970) and Clark and others (2016); appears to be conformable with underlying Bingham Mine Formation; incomplete thickness is estimated at 300 to 400 feet (90–120 m), Clark and others (2016) reported unit is 3500 feet (1065 m) at the Cedar Mountains.

PERMIAN TO CAMBRIAN ROCKS OF THE SILVER ISLAND MOUNTAINS, FLOATING ISLAND, AND SOUTHERN NEWFOUNDLAND MOUNTAINS

P*ps Pequop Formation, Ferguson Mountain Formation, and Strathearn Formation, undivided (lower Permian to Upper Pennsylvanian?) – Combined unit consisting of a thick, monotonous interval of interbedded limestone and calcareous siltstone and sandstone overlying relatively thin basal limestone and pebble-conglomerate at Floating Is- land (current map area) and the adjacent Silver Island Mountains and Leppy Hills. Pequop Formation is medium- to dark-gray, silty bioclastic limestone, lesser yellow and gray siltstone and sandstone, light-gray dolomite, and limestone with chert pebbles; bedding is thin to thick, typically forming slopes with some ledges and cliffs; fusulinid and crinoid columnal fossils and white calcite blebs are diagnostic; incomplete thickness about 2330 feet (710 m) (see Steele, 1959, 1960; Schaeffer and Anderson, 1960; Bissell, 1964; Schneyer, 1990); underlying Ferguson Mountain Formation (after Hodgkinson, 1961; Bissell, 1962; Schneyer, 1990) consists of gray bioclastic and argillaceous limestone and dolomite with chert nodules near base and top; bedding is thin to thick forming slopes and ledges; less than 100 to 180 feet (<30–55 m) thick in the Leppy Hills and Silver Island Mountains (also see Schaeffer and Ander- son, 1960; Steele, 1960); however, Schaeffer and Anderson (1960) and Miller and others (in progress) indicate this interval changes dramatically from north to south and is difficult to separate from the Pequop Formation; different nomenclature was previously used for the Ferguson Mountain (Schaeffer and Anderson, 1960; Steele, 1960); basal Strathearn Formation locally includes an upper part of gray limestone and dolomitic limestone, red and yellowish- brown sandstone and siltstone, and lower part of distinctive brownish-gray pebble conglomerate with chert and limestone clasts in a pink silty limestone matrix; in several areas of the Silver Island Mountains formation is a single Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 13

bed of conglomerate; bedding is thin to medium forming ledges and slopes; Strathearn thickness is variable from 0.3 to 150 feet (0.1–45 m) (Schaeffer and Anderson, 1960; Miller and others, in progress; this study); fusulinid fossils from the Pequop and Ferguson Mountain Formations at the Leppy Hills and Silver Island Mountains were originally reported to range from early Guadalupian to Leonardian to Wolfcampian in age (Steele, 1959, 1960; Steele and others in Schaeffer and Anderson, 1960), but the two formations are considered Leonardian, Wolfcampian and Upper Virgilian at Ferguson Mountain, Nevada (Berge, 1960; Slade, 1961; Bissell, 1962, 1964), and conodont fossils from the nearby Pequop Mountains are Leonardian to late Wolfcampian age (Behnken, 1975); the Ferguson Mountain Formation is considered Wolfcampian from fusulinids at the Leppy Hills (Hodgkinson, 1961; Bissell, 1962); the Strathearn is not well dated with fusulinid fossils in the Silver Island Mountains and Leppy Hills, but is considered lower Wolfcampian to Upper Pennsylvanian (Steele, 1959; Schaeffer and Anderson, 1960; Hodgkinson, 1961; Bis- sell, 1964; Schneyer, 1990); Schaeffer and Anderson (1960) also reported brachiopod, gastropod and bryozoan fossils from the combined unit; Bissell (1964) used Arcturas Group nomenclature for the Loray, Pequop and Ferguson Mountain Formations; the Strathearn unconformably overlies the Ely Limestone with a local angular unconformity (Schaeffer and Anderson, 1960; Schneyer, 1990; Miller and others, in progress); north of map area in the Newfound- land Mountains the Pequop and Strathearn unconformably overlie the Pilot Shale (Allmendinger and Jordan, 1984; Miller and others, in press); unit P*ps thickness is as much as 2550 feet (>780 m) but incomplete in the Silver Island Mountains and Leppy Hills (Schaeffer and Anderson, 1960; Schneyer, 1990), a similar incomplete thickness exists at Floating Island (this study).

*e, *e?

Ely Limestone (Middle and Lower Pennsylvanian) – Upper part is generally brown and gray-colored sandy limestone with lesser interbeds of brown sandstone and siltstone whereas the lower part is limestone that is generally medium to dark gray, some chert as nodules and beds, and thicker bedded; bedding is typically medium to very thick, forming cliffs and ledges; queried at southeastern Floating Island where contact with overlying unit P*ps is uncertain as the Strathearn may be absent or cover obscures structural complications; fusulinid fossils from the Leppy Hills and Ferguson Mountain, Nevada indicate age range from Desmoinesian to Morrowan (Steele, 1959, 1960; Steele and others in Schaeffer and Anderson, 1960; Slade, 1961; Bissell, 1964); sample BW34 from the upper Ely at Floating Island yielded Idiognathodus and Neognathodus conodont fossils of middle to early Desmoinesian (Moscovian) age (S.M. Ritter, BYU, email to Clark, June 16, 2020); upper part includes Hogan Formation of Hodgkinson (1961) and Bissell (1964), and Bissell (1964) used Ely Group nomenclature; incomplete thickness at Floating Island is about 500 feet (150 m) (this study), and thickness is 1640 feet (500 m) at the Leppy Hills (Schneyer, 1990) and about 1740 feet (530 m) at Rishel Peak of Silver Island Mountains (Schaeffer and Anderson, 1960), but the formation thins northward (Schaeffer and Anderson, 1960; Miller and others, in progress).

*Mdc

Diamond Peak Formation and Chainman Shale, undivided (Lower Pennsylvanian to Upper and Lower Missis- sippian) – Brown sandstone, tan calcareous sandstone, dark-brown heterolithic conglomerate, black shale, and black coarse-grained limestone; typically laminated to medium bedded forming slopes and ledges; fossils include a diverse gastropod and brachiopod fauna (Yochelson and Dutro in Schaeffer and Anderson, 1960), and Poole and Sandberg (1991) report Chesterian conodont fossils; age is Late Mississippian probably ranging into the Early Pennsylvanian (Schaeffer and Anderson, 1960); thickness varies considerably along strike, apparently as a result of structural thin- ning (attenuation) in many locations; thickness is incomplete in the current map area at about 200 feet (60 m), but in the Silver Island Mountains is as much as 1150 feet (350 m) at Donner Canyon and other exposures are faulted (Schaeffer and Anderson, 1960; Miller and others, in progress; this study).

Mj Joanna Limestone (Lower Mississippian) – Black, cherty limestone with abundant fossil brachiopods and corals (Schaeffer and Anderson, 1960); bedding is thin to very thick forming cliffs; Poole and Sandberg (1991) called the unit Joana equivalent strata with Osagean and Kinderhookian conodont fossils in the Silver Island Mountains; C.A. Sandberg (verbal communication to Clark, June 21, 2018) called the unit Lodgepole Limestone in the northern Silver Island Mountains; Joanna is locally in contact with the Guilmette Formation where the Pilot Shale is absent likely due to low-angle faulting and attenuation; thickness is from 0 to 130 feet (0–40 m) (thin to absent south of Graham Peak where grouped with unit *Mdc, and maximum thickness in the north) (Miller and others, in progress).

DSu Undivided dolomite and limestone (Devonian and Silurian) – Undivided rocks in the southern Newfoundland Moun- tains on the UTTR-North area (not field checked), shown on adjacent maps as corresponding to the Pilot Shale, Guil- 14 Utah Geological Survey

mette Formation, Simonson Dolomite, and Lone Mountain Dolomite? (Allmendinger and Jordan, 1989; Miller and others, in press); in the map area, top part is not exposed with about 2300 feet (700 m) present (this study), and to the north total unit thickness of about 3600 feet (1100 m).

MDp Pilot Shale (Lower Mississippian to Upper and Middle? Devonian) – Formation is not exposed in the current map area, but is locally present in the adjacent Graham Peak 7.5' quadrangle and southward in the Silver Island Mountains; southern Newfoundland Mountains area was not accessed; thickness is 0 to about 200 feet (60 m) in the Silver Island Moun- tains and 425 feet (130 m) in the nearby Leppy Hills (Schaeffer and Anderson, 1960; Miller and others, in progress).

Dg, Dg?

Guilmette Formation (Upper and Middle Devonian) – Light- to dark-gray and black limestone that is cliff-forming and prominent in the Silver Island Mountains. Mapped as undivided formation in this map but subdivided into three informal units by Miller and others (in progress) in the Graham Peak area. Upper unit, about 885 feet (270 m) thick, is cliffy, fossiliferous, medium-gray to black limestone, with lenses of sand and “rip-up” beds in upper 300 feet (100 m) in some places, and some minor intervals of platey brown sandstone and siltstone; middle unit is a slope-cliff- slope interval about 367 feet (112 m) thick consisting of argillaceous limestone for slopes and a cliff of fossiliferous dark-gray limestone in the center of the interval that is about 165 feet (50 m) high; cliffy unit locally has quartz sand and “rip-up” clasts, as well as turbidite beds; lower unit is alternating shaly and non-shaly, dark-gray limestone that forms cliffs in its upper part, fossiliferous with abundant brachiopods, and about 985 feet (300 m) thick; bedding is typically medium to very thick; on this map upper unit is locally separated from middle and lower units (see dashed line on plate 1); base of formation placed at change from cliffy finely crystalline black limestone sequence (Guilmette) to top of interbedded dolomite and limestone interval (Simonson) (Schaeffer and Anderson, 1960; Miller and others, in progress); fossil stromatoporoids are present, as well as coral and algal heads; age is considered Late and Middle Devonian (Schaeffer and Anderson, 1960; Sandberg and Poole, 1977); Guilmette thickness is about 2230 feet (680 m) in the Silver Island Mountains (Schaeffer and Anderson, 1960; Miller and others, in progress).

Dsi Simonson Dolomite (Middle and Lower? Devonian) – Gray interbedded limestone and dolomite in upper part (650 feet [200 m]), with limestone similar to the overlying Guillmette; lower part of dark- and light-colored, ledge-forming, laminated dolomite; base placed at bottom of lowest dark-gray to black dolomite bed with prominent laminations; bedding is thin to very thick forming ledges, cliffs and slopes; fossils include brachiopods, corals and stromatoporoids and formation is considered Middle Devonian (Schaeffer and Anderson, 1960); Simonson may be unconformable on the Laketown as the Sevy Dolomite is not present (see Hintze and Kowallis, 2009); thickness is about 1270 feet (390 m) (Schaeffer and Anderson, 1960; Miller and others, in progress).

Sl Laketown Dolomite (Silurian) – Thick section of dolomite forming prominent light- and dark-colored cliffs in Gra- ham Peak area of Silver Island Mountains, Miller and others (in progress) identified three units. Upper unit is light- gray dolomite, locally poorly bedded; middle unit is black, dark-gray, and medium-gray dolomite, much of it cherty and mottled, sandy dolomite and rare quartz sandstone beds with base marked by 15 to 30 feet (5–10 m) of bedded chert; lower unit is white to pale-buff, laminated dolomite underlain by dark-gray and black, mottled and laminated, dolomite; fossils include corals, stromatoporoids and brachiopods (Schaeffer and Anderson, 1960); age from Schaef- fer and Anderson (1960) and Hintze and Davis (2003); Sheehan (1979) assigned the upper 850 feet (260 m) of Schaef- fer’s Laketown to the Roberts Mountain Formation; Laketown is unconformable on the Ely Springs (Hintze and Kowallis, 2009); incomplete thickness in the Floating Island quadrangle is about 500 feet (150 m); thickness is 1070 feet (325 m) in Silver Island Mountains (Miller and others, in progress) and about 850 feet (260 m) at the southern Newfoundland Mountains (Miller and others, in press).

Oes Ely Springs Dolomite (Upper Ordovician) – Gray dolomite in tripartite section that generally forms steep cliffs; upper part is a cliff of light-gray dolomite, correlated with the Floride Member of Budge and Sheehan (1980), locally contains a central dark-gray dolomite interval, upper part is 65 feet (20 m) thick; middle part is silty, platy dolomite and sandstone that forms benches, about 130 feet (39 m) thick; lower part (most of unit) composed of mottled, cherty, black dolomite that is cliffy and about 380 feet (115 m) thick; Waite in Schaeffer and Anderson (1960) reported fossil corals and brachiopods of Late Ordovician age; Ely Springs is unconformable on the Eureka (Hintze and Kowallis, 2009); previously called Fish Haven Dolomite (Schaeffer and Anderson, 1960; Allmendinger and Jordan, 1989); only incomplete exposures in current map area about 200 feet (60 m) thick, but formation is about 575 feet (175 m) at the Silver Island Mountains (Miller and others, in progress), and about 590 feet (180 m) at the Newfoundland Mountains (Allmendinger and Jordan, 1989; Miller and others, in press). Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 15

Oe Eureka Quartzite (Upper Ordovician) – White to blue-gray orthoquartzite, weathers to orange and reddish brown colors; commonly fractured and poorly bedded, forming steep rubble-covered slopes and cliffs; incomplete thickness about 100 to 200 feet (30–60 m) in current map area, complete thickness is 370 feet (115 m) at the Silver Island Moun- tains (Schaeffer and Anderson, 1960), and north of map area is about 500 feet (150 m) in the Newfoundland Mountains (Allmendinger and Jordan, 1989).

O Ordovician units (Middle and Lower Ordovician) – Several Ordovician rock units of the Silver Island Mountains are not exposed in the current map area; these units include (descending) the Crystal Peak Dolomite, Watson Ranch Quartzite, Lehman Formation, Kanosh Shale, and lower Pognip Group (Juab Limestone, Wah Wah Limestone, Fill- more Formation) (Miller and others, in progress).

_np Notch Peak Formation (lowermost Ordovician to upper Cambrian) – Medium- to dark-gray and black, cherty limestone and light-gray to light-brown and black dolomite; upper one-third of formation is mostly dolomite; thick bedded, forming cliffs; algal buildups, “rip-up” clasts, and ooid beds common; age is based on fossil trilobite fauna (Robison in Schaeffer and Anderson, 1960; Robison and Palmer, 1968); thickness is about 1640 feet (500 m) in Silver Island Mountains (McCollum and Miller, 1991; Miller and others, in progress).

_ou Orr Formation, upper part (upper Cambrian) – Combined unit in Silver Island Mountains that includes (descending) the Corset Spring Shale, Johns Wash Limestone, and Candland Shale Members (modified from Miller and others, in progress); follows McCollum and Miller (1991) but with their formations as members of the Orr Forma- tion after Hintze and Palmer (1976); unit was previously mapped with different nomenclature by Schaeffer and Anderson (1960), also see Robison and Palmer (1968); unit _ou is incomplete at 425 feet (130 m) thick in current map area, but complete thickness is 605 feet (185 m) (McCollum and Miller, 1991; Miller and others, in progress). Corset Spring Shale Member consists of yellowish-green shale and silty limestone forming slopes and benches; 65 feet (20 m) thick; Johns Wash Limestone Member is limestone that is generally silty; forms cliffs with prominent white streak in center part; upper and lower parts are dark gray and thin bedded, central part is marbleized and white; brown interbeds near the base consist of siltier limestone than elsewhere; 260 feet (80 m) thick; Candland Shale Member is brown, calcareous siltstone and silty limestone, highly fossiliferous with trilobites (see Robison and Palmer, 1968), and forms steep slopes; incomplete exposure in current map area about 100 feet (30 m) thick, but complete thickness is 280 feet (85 m).

_ Cambrian units (upper to lower Cambrian and Neoproterozoic?) – Several Cambrian rock units of the Silver Island Mountains are not exposed in the current map area; these units include (descending) the Orr Formation-Big Horse Limestone Member, Lamb Dolomite, and parts of the underlying Toano Limestone, Killian Springs Formation, and Prospect Mountain Quartzite (McCollum and Miller, 1991; Miller and others, in progress).

ACKNOWLEDGMENTS

We thank numerous individuals and entities for assistance in completion of this project. Clean Harbors Environmental, Energy Solutions and Neptune and Company, the Utah Department of Environmental Quality (Ed Costomiris and Charles Bishop), and Hill Air Force Base and UTTR (Russ Lawrence, Michael Byrk, Michael Shane), and Intrepid Potash (Eric Rogers and Craig Peterson) helped provide access and/or technical data. Brenda Bowen and Jeremiah Bernau (Univer- sity of Utah) collaborated on subsurface studies of the Bonneville Salt Flats area. Geochemical laboratory work was by ALS Global. Scott Ritter (Brigham Young University) and Greg Wahlman (Independent) identified microfossils for biostratigraphic control. Kevin Bylund and Jim Jenks (independent researchers) shared fossil data. Hellmut Doelling (UGS, retired) provided a revised and colored version of his dissertation map and a revised digital text (Doelling, unpublished, 2003). Taylor Boden (UGS) shared his gypsum dune mapping data. Peter Nielsen and Tom Dempster (Utah Core Re- search Center) gave access to available cores and cuttings and assisted with fossil preparation and sediment cores. David Miller (U.S. Geological Survey, Emeritus) shared preliminary mapping data for the Silver Island Mountains. UGS staff, including Jon King, Grant Willis, Stephanie Carney, and Michael Hylland, reviewed and improved this map. Martha Jen- sen and Lori Steadman helped prepare the explanatory materials; Basia Matyjasik organized the GIS data and addressed cartographic issues. 16 Utah Geological Survey

REFERENCES

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MISSOURIAN Jordan Ls Mbrs Ls Mbr

limestone Oquirrh Group

unit Oquirrh Formation Butterfield Bear DESMOINESIAN Peaks Canyon Middle ? Formation MOSCOVIAN Member PENNSYLVANIAN ATOKAN

CARBONIFEROUS ? Bridal Veil West Canyon Limestone

Lower Limestone Member BASHKIRIAN ? ? MORROWAN

Manning Canyon Manning Canyon Formation Shale Upper MISS. CHESTERIAN SERPUKHOVIAN

Figure 3. Comparison of Permian-Pennsylvanian nomenclature of the Oquirrh Group/Formation and other units used in this map and adjacentFigure areas. 3. Comparison Grassy Mountains of Permian-Pennsylvanian modified from Doelling nomenclature(1964) and Jordan of the(1979a, Oquirrh 1979b). Group/Formation See Clark and others and (2017) other for units Oquirrh, Stansbury,used in thisand Cedarmap and Mountains. adjacent See areas. Constenius Grassy and othersMountains (2011) modifiedfor Wasatch from Range. Doelling (1964) and Jordan (1979a, 1979b). See Clark and others (2017) for Oquirrh, Stansbury, and Cedar Mountains. See Constenius and others (2011) for Wasatch Range. 24 Utah Geological Survey

Table 1. Summary of UGS shallow pits and cores and other selected sediment data sites from the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Utah.

Ground Total Total Samples for Collection Latitude (°N) Longitude (°W) UTM easting UTM northing Summary of Map ID/Site ID Type 7.5' Quadrangle Elevation Depth Depth Ostracode Collector/Reference Year WGS84 WGS84 NAD83-12 NAD83-12 Deposits Encountered (ft) (m) (ft) Evaluation post-Bonneville, Lake Bonneville, C29-5 landfill pit wall N 2014 Aragonite 40.70608 113.11609 321240 4508283 4283 10 33 Oviatt, 2017 pre-Bonneville post-Bonneville, Lake Bonneville, C5-5 landfill pit wall S 2014 Aragonite 40.67403 113.12063 320771 4504734 4272 3.5 12 Oviatt, 2017 pre-Bonneville CH1 pit 2017 Grayback Hills 40.76902 113.23968 310977 4515529 4226 0.55 1.8 post-Bonneville, Lake Bonneville Oviatt and Clark; this study CH2 wall of excavation 2017 Grayback Hills 40.82862 113.20423 314135 4522072 4240 1.5 4.9 post-Bonneville Oviatt and Clark; this study post-Bonneville, Lake Bonneville, Kn1 pit 2017 Knolls 40.72439 113.35040 301499 4510819 4220 1.15 3.8 yes Oviatt and Clark; this study pre-Bonneville NUTTR1 pit 2018 Knolls 2 SE 40.86745 113.26466 309151 4526511 4223 0.32 1.1 post-Bonneville, Lake Bonneville Oviatt and Clark; this study NUTTR2 pit 2018 Knolls 2 NE 40.90242 113.28255 307745 4530432 4217 0.55 1.8 post-Bonneville Oviatt and Clark; this study FI1 pit 2018 Floating Island SE 40.79875 113.59486 281096 4519656 4216 1.15 3.8 yes post-Bonneville, Lake Bonneville Oviatt and Clark; this study SI1 pit 2019 Floating Island 40.99435 113.72300 270944 4541701 4234 0.07 0.23 yes Lake Bonneville Clark; this study post-Bonneville, pre- or post-Bonneville (?), BC1 core 2019 Aragonite NW 40.72753 113.23363 311371 4510910 4247 6 20 yes Oviatt and Clark; this study pre-Bonneville BC2 core 2019 Tetzlaff Peak 40.76275 113.95078 250932 4516610 4218 6 20 yes pre-Bonneville Oviatt and Clark; this study BC3 core 2019 Salduro 40.73342 113.75719 267172 4512821 4220 6 20 yes pre-Bonneville Oviatt and Clark; this study post-Bonneville?, Lake Bonneville, BC4 core 2019 Knolls 40.72598 113.41927 295687 4511153 4220 0.55 1.8 yes Oviatt and Clark; this study pre-Bonneville? BC5 core 2019 Arinosa NE 40.73829 113.57438 282627 4512893 4218 0.63 2.1 yes post-Bonneville?, Lake Bonneville Oviatt and Clark; this study post-Bonneville?, Lake Bonneville, BC6 core 2019 Floating Island SE 40.86785 113.61382 279725 4527375 4216 0.61 2 yes Oviatt and Clark; this study pre-Bonneville BC7 core 2019 Graham Peak 40.88566 113.78649 265235 4529802 4218 0.49 1.6 yes pre-Bonneville Oviatt and Clark; this study BC8 core 2019 Arinosa 40.73190 113.67546 274069 4512439 4215 1.03 3.4 yes post-Bonneville, pre-Bonneville Oviatt and Clark; this study BC9 core 2019 Barro 40.66622 113.40869 296399 4504494 4217 0.51 1.7 yes post-Bonneville Oviatt and Clark; this study USOL (BSF Solstice core) core 2017 Bonneville Racetrack 40.76316 113.89519 255626 4516499 ~4212 3.20 10.5 post-Bonneville, pre-Bonneville Bernau and others, unpublished UWS2 (BSF Weather Station 2 core) core 2019 Bonneville Racetrack 40.78451 113.82990 261214 4518689 ~4212 3.48 11.4 post-Bonneville, pre-Bonneville Bernau and others, unpublished USC (BSF Short Course 1 core) core 2019 Bonneville Racetrack 40.81252 113.77194 266204 4521643 ~4212 3.90 12.8 post-Bonneville, pre-Bonneville Bernau and others, unpublished post-Bonneville, Lake Bonneville, JBT (Juke Box trench, section 1) trench 1986, 2009 Leppy Peak 40.75491 114.01021 245885 4515909 4254 3 9.8 Oviatt and others, 2018 pre-Bonneville Green, unpublished; LS (Lozenge section) outcrop NA Graham Peak 40.89261 113.79781 264306 4530604 4245 4 13 Lake Bonneville, pre-Bonneville Munroe and others, 2015 post-Bonneville, Gilbert-episode, BLC (Blue Lake core, BL04-4) core 2004 Ferguson Flat 40.49997 114.03614 242717 4487681 4257 8.58 28.1 Benson and others, 2011 Lake Bonneville, pre-Bonneville WC (Wendover core) core 1960 Salduro 40.73712 113.87185 257501 4513544 4217 171 560 Williams, 1994 KC (Knolls core) core 1960 Knolls 40.72685 113.30903 305000 4511000 4234 152 500 Williams, 1994

Notes: Map ID corresponds to plate 1. Sites in gray highlight are not in current map area. See Oviatt and others, 2020 for details on sediment pit, core and other data. Landfill pit walls (for sections C29-5 and C5-5) were at the Energy Solutions landfill at Clive, Utah; CH2 was a pit-wall exposure in an excavation at Clean Harbors Grassy Mountain landfill. Shallow pits were dug using a shovel. Cores BC1, BC2, BC3 were collected by Push Drilling, LLC. Remaining sediment cores were collected by hand-driving a PVC pipe into the mud. Ground elevation determined from 7.5' topographic maps. The Wendover and Knolls cores were taken by A.J. Eardley (Univ. of Utah), core locations are approximate; detailed logs of the cores have never been published. These cores are archived at the Utah Core Research Center (Salt Lake City, Utah). No reevaluation of the Wendover and Knolls cores was conducted for this study. "Green, unpublished": Sue Green was a graduate student of D.R. Currey (University of Utah) in the 1980s; this "lozenge" section was part of her Master's thesis, which was not completed. It is anticipated that the 2017-2019 cores will be archived at the Utah Core Research Center. Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 25

Table 2. Summary of tephrochronology data from the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles.

Map Core 7.5' Latitude (°N) Longitude (°W) Tephra Depth Depth Correlation Reference ID Name Quadrangle NAD83 NAD83 Name (ft.in) (m) Age (Ma) KC Knolls Knolls 40.72685 113.30903 KNL-142.0 142.0 43.3 nd Williams, 1994 Williams, 1994; KC Knolls Knolls 40.72685 113.30903 Lava Creek B 346.0, 350.6 105.5, 106.9 0.639 ± 0.002 Lanphere and others, 2002 Williams, 1994; KC Knolls Knolls 40.72685 113.30903 Glass Mtn D? 486.10 148.2 <0.88 ± 0.07 Sarna-Wojcicki and others, 2005 WC Wendover Salduro 40.73712 113.87185 Paoha Island 88.6 27.0 0.17* Williams, 1994 Williams, 1994; WC Wendover Salduro 40.73712 113.87185 Lava Creek B 271.8, 272.8 82.8, 83.13 0.639 ± 0.002 Lanphere and others, 2002 Williams, 1994; WC Wendover Salduro 40.73712 113.87185 Bishop 323.0 98.5 0.759 ± 0.002 Sarna-Wojcicki and others, 2005 Williams, 1994; WC Wendover Salduro 40.73712 113.87185 Glass Mtn D? 372.7 113.6 <0.88 ± 0.07 Sarna-Wojcicki and others, 2005 WC Wendover Salduro 40.73712 113.87185 Bailey 497.4 151.6 1.15* Williams, 1994

Notes: Map ID corresponds to plate 1. Knolls and Wendover core locations are approximate. Correlation age is based on geochemical correlation of glass composition to the database of analyses/stratigraphic data/age dates for late Cenozoic vitric tephra layers in the Western U.S. assembled at the University of Utah, Dept. of Geology and Geophysics. Geochemical analysis was by electron microprobe and x-ray fluroescence. Refer toWilliams (1994) for methods and sources of radiometric ages on various ash beds. Updated ages are used for the Lava Creek B and Glass Mtn D tephras. * Estimated ages in Wendover core (Williams, 1994, figure 6). nd is no data.

26 Utah Geological Survey

Table 3. Data and formation tops for hydrocarbon exploration wells in the Bonneville Salt Flats and east part of Wendover 30' x 60' quadrangles.

7.5' Latitude Longitude Ground Elevation Top Thickness Elevation Map ID API Number Operator Well Name Year Status Type Cadastral Location Unit/Formation Notes Quadrangle NAD83 (°N) NAD83 (°W) (ft) (ft) (ft) (ft) C, SE1/4, NW1/4, cuttings and core at DH1 4304511076 Shell Salduro 1 1956 Plugged & abandoned Dry hole Silsbee 40.68416 113.89716 4216 alluvium 0 1375 4216 s. 4, T. 2 S., R. 18 W. UCRC Tertiary 1375 225 3991 volcanic breccia 1600 192 3799 volcanic tuff 1792 48 3751 volcanic sandstone 1840 20 3731 breccia 1860 780 2951 andesite 2640 100 2851 basalt 2740 210 2641 TD 2950 1266 NE1/4, NW1/4, DH2 4304530001 Alpha Minerals Alpha Govt 1 1975 Plugged & abandoned Dry hole Salduro 40.70155 113.76509 4225 not reported 0 500 4225 no cuttings or core s. 34, T. 1 S., R. 17 W. Tertiary volcanics 500 628 3597 Tertiary shale 1128 1852 1745 Paleozoic limestone 2980 1280 465 and dolomite TD 4260 -35

Notes: Data from Utah Division of Oil, Gas and Mining online database and well files. TD is total depth. UCRC is Utah Core Research Center. UCRC has samples from Phillips Petroleum Co. Grassy Mountain Sec. (October 1949) from T. 2 N., R. 11 W. probably from a surface section, rather than a drill hole. There are no known Phillips drill holes from this area.

Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 27

Table 4. Major- and trace-element whole-rock geochemical analyses from the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles. ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- OA- ME- ME- ME- ME- ME- ME- ME- XRF06 XRF06 XRF06 XRF06 XRF06 XRF06 XRF06 XRF06 XRF06 XRF06 XRF06 XRF06 XRF06 GRA06 XRF06 4ACD81 4ACD81 4ACD81 4ACD81 4ACD81 4ACD81 % % % % % % % % % % % % % % % ppm ppm ppm ppm ppm ppm Location Data Location Data Map Sample Map Rock Name 7.5' Quad Latitude (°N) Longitude (°W) Source SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O Cr2O3 TiO2 MnO P2O5 SrO BaO LOI Total Ag As Cd Co Cu Li ID ID Unit WGS84 WGS84 BW1 BW1 Tl Latite Aragonite NW 40.74466 113.14455 This study 58.94 17.27 6.96 5.33 2.21 3.22 3.9 <0.01 0.72 0.12 0.312 0.06 0.13 1.02 100.2 <0.5 5 <0.5 18 14 20 BW2 BW2 Til Latite Grayback Hills 40.80745 113.16499 This study 58.38 17.05 6.57 5.02 2.52 3.13 4.03 <0.01 0.71 0.08 0.307 0.05 0.12 1.81 99.78 <0.5 <5 0.5 17 14 30 BW5 BW5 Tl Latite Grayback Hills 40.80001 113.16483 This study 57.25 16.96 6.93 5.83 2.58 3.11 3.61 0.01 0.71 0.11 0.313 0.06 0.13 1.76 99.36 <0.5 <5 0.8 16 17 30 BW7 BW7 Tid Dacite Grassy Mountains 40.90357 113.09988 This study 63.12 16.32 5.26 4.57 1.83 3.44 3.18 0.01 0.73 0.08 0.184 0.04 0.12 1.28 100.15 <0.5 <5 <0.5 11 15 10 BW8 BW8 Tid Andesite Grassy Mountains 40.94005 113.11605 This study 61.27 16.88 4.99 5.08 1.62 3.45 3.23 0.01 0.99 0.09 0.298 0.05 0.15 1.61 99.72 <0.5 <5 <0.5 14 36 10

Location Data Location Data UTM83-12 E UTM83-12 N 1 1 Til Trachyandesite Grayback Hills 317373 4519662 Doelling and others, 1994, 2018 58.83 16.25 6.53 5.04 2.37 3.09 3.71 0.07 0.08 0.29 2.02 98.91 2 2 Tl Andesite Grayback Hills 318247 4515096 Doelling and others, 1994, 2018 60.97 16.03 5.70 4.78 1.45 3.43 3.21 0.98 0.08 0.28 2.04 98.95 3 3 Tl Trachyandesite Grayback Hills 319277 4520243 Doelling and others, 1994, 2018 58.50 16.57 6.53 5.25 2.40 3.08 3.60 0.71 0.10 0.25 2.06 99.05 4 4 Tl Trachyandesite Grayback Hills 318393 4517621 Doelling and others, 1994, 2018 58.30 16.62 6.97 5.60 2.52 3.26 3.69 0.75 0.11 0.36 1.98 100.16 5 5 Tl Trachyandesite Grayback Hills 317820 4519418 Doelling and others, 1994, 2018 58.32 16.50 6.52 5.63 2.44 3.09 3.60 0.69 0.10 0.27 2.04 99.02 ˗˗ 6 Tl Banakite nd nd nd Hogg, 1972, table B-4, p. 180 57.93 16.65 7.22 5.93 2.44 3.13 4.46 0.87 0.09 0.35 nd 99.07 7 7 Tsd Dacite Grayback Hills 317387 4519725 Doelling and others, 1994, 2018 63.96 15.12 4.75 4.15 1.90 3.02 nd 0.60 0.06 0.20 1.95 98.80 8 8 Tsd Dacite Grayback Hills 318274 4520355 Doelling and others, 1994, 2018 63.30 17.82 3.28 0.88 5.02 3.79 nd 0.36 0.04 0.16 1.75 98.78

Table 4. Continued. ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- 4ACD81 4ACD81 4ACD81 4ACD81 4ACD81 4ACD81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm Location Data Location Data Map Sample Map Rock Name 7.5' Quad Latitude (°N) Longitude (°W) Source Mo Ni Pb Sc Tl Zn Ba Ce Cr Cs Dy Er Eu Ga Gd Hf Ho La Lu Nb Nd Pr Rb ID ID Unit WGS84 WGS84 BW1 BW1 Tl Latite Aragonite NW 40.74466 113.14455 This study 2 5 21 11 <10 89 1140 77.5 20 2.56 4.25 2.15 1.42 21 5.42 5.1 0.89 43.7 0.33 13.5 32.2 8.85 138 BW2 BW2 Til Latite Grayback Hills 40.80745 113.16499 This study 2 5 24 11 <10 92 1095 74.9 20 3.31 4.18 2.19 1.35 20.9 5.14 4.8 0.81 42.2 0.33 13.3 31.5 8.52 156.5 BW5 BW5 Tl Latite Grayback Hills 40.80001 113.16483 This study 2 5 20 11 <10 89 1170 77.8 20 3.12 3.95 2.14 1.39 23.9 5.22 5.1 0.86 43 0.33 13.7 32.3 8.71 138.5 BW7 BW7 Tid Dacite Grassy Mountains 40.90357 113.09988 This study 3 4 26 11 <10 77 1075 108 20 2.44 6.94 4.02 1.62 22.5 7.78 8.7 1.5 60.7 0.58 22.3 44.2 12.2 117 BW8 BW8 Tid Andesite Grassy Mountains 40.94005 113.11605 This study 3 7 28 12 <10 88 1310 135 20 3.18 7.68 4.38 1.96 23.4 8.28 10.1 1.59 75.6 0.62 23.5 54.8 15.05 104

Table 4. Continued. ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- ME- MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 MS81 ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm Location Data Location Data Map Sample Map Rock Name 7.5' Quad Latitude (°N) Longitude (°W) Source Sm Sn Sr Ta Tb Th Tm U V W Y Yb Zr ID ID Unit WGS84 WGS84 BW1 BW1 Tl Latite Aragonite NW 40.74466 113.14455 This study 6.09 2 444 0.8 0.73 14.2 0.37 3.5 123 2 21.6 1.92 196 BW2 BW2 Til Latite Grayback Hills 40.80745 113.16499 This study 5.97 2 422 0.7 0.66 13.8 0.32 3.62 119 1 21 2.24 190 BW5 BW5 Tl Latite Grayback Hills 40.80001 113.16483 This study 6.43 2 470 0.7 0.74 14.5 0.36 3.52 120 1 22.1 2.14 197 BW7 BW7 Tid Dacite Grassy Mountains 40.90357 113.09988 This study 8.31 3 262 1.4 1.14 21.5 0.64 5.14 102 1 38.4 3.87 332 BW8 BW8 Tid Andesite Grassy Mountains 40.94005 113.11605 This study 10.3 3 389 1.3 1.29 22.8 0.63 4.93 126 2 40.2 4.23 389

Notes: Map ID and map unit correspond to plate 1. Rock names for this study from total alkali-silica diagram of Le Bas and others (1986). Other rock names are from sources cited. Analyses for this study performed by ALS Global. Analytical Procedures: ME-XRF06 (whole-rock package by XRF; major oxides), OA-GRA06 (LOI for ME-XRF06 by WST-SIM), ME-4ACD81 (base metals 4-acid digestion by ICP-AES, elemental), and ME-MS81 (lithium borate fusion by ICP-MS, trace elemental). Major oxides reported in weight percent (%); < indicates value below detection limit. LOI is loss on ignition. Minor and trace elements reported in parts per million (ppm); < indicates value below detection limit. nd is no data. Analytical lab for samples from Doelling and others (1994) not given. Hogg (1972) sample collected from southern Grayback Hills. Analytical lab for Hogg (1972) sample not given, probably Brigham Young University. Total Fe reported as FeO (Hogg, 1972). 28 Utah Geological Survey

Table 5. Summary of radiometric age analyses of Tertiary rocks from the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles and adjacent areas.

Location Data Location Data Material Analysis Type Map ID Sample ID Map Unit Rock Name 7.5' Quadrangle Location Age (Ma) Laboratory Comments References UTM83-12 E UTM83-12 N Dated (Year) 40Ar/39Ar total fusion ages, A A Tsd dacite tuff Grayback Hills Grayback Hills 317387 4519725 35.52 ± 0.38 plagioclase USGS Doelling and others, 1994, 2018 (1992?) weighted age Doelling and others, 1994, 2018; UGS and B B Tsd dacite tuff Grayback Hills Grayback Hills 317387 4519725 38.6 ± 1.0 sanidine KE K-Ar (1992) Krueger Enterprises, 2018 Doelling and others, 1994, 2018; UGS and C C Tl latite lava flow Grayback Hills Grayback Hills 318247 4515096 39.1 ± 1.0 groundmass KE K-Ar (1992) Krueger Enterprises, 2018 ˗˗ nd Tl latite lava flow nd Grayback Hills nd nd 38.5 ± 0.6 whole rock BYU K-Ar (1977) Davies, 1980; Doelling and others, 1994

Notes: Map ID and map unit correspond to plate 1. Laboratory: USGS is U.S. Geological Survey Lab; KE is Krueger Enterprises, Cambridge, MA; BYU is Brigham Young University Lab. nd is no data.

Interim geologic map of the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles, Tooele County, Utah—year 3 29

Table 6. Selected fossil identifications and ages from the Bonneville Salt Flats and east part of the Wendover 30' x 60' quadrangles.

Map ID Sample ID Map Unit 7.5' Quadrangle Location Data Location Data Fossil Type Fauna Age Paleontologist

Data from map area (this study) Latitude (°N) WGS84 Longitude (°W) WGS84 BW30 BW30 Ppy Aragonite SW 40.62267 113.13719 conodont Neostreptognathodus sulcoplicatus middle to late Leonardian S.M. Ritter BW21 BW21 Polf Finger Ridge 40.91021 113.16137 fusulinid Schwagerina cf. lineanoda, Schwagerina tersa late Wolfcampian (Lenoxian) G.P.Wahlman BW23 BW23 Polk Knolls 40.70362 113.28771 fusulinid Schwagerina wellsensis, Schwagerina franklinensis late Wolfcampian (Lenoxian) G.P.Wahlman Wolfcampian, probably Early BW27 BW27 Polk Knolls 40.67122 113.28897 fusulinid Psuedofusulina aff. P. loringi, Paraschwagerina? sp., Schwagerina spp., Schubertella sp. G.P.Wahlman Wolfcampian (Nealian) Eoparafusulina cf. E. linearis, Schwagerina wellsensis, Pseudoschwagerina aff. P. convexa, Schwagerina cf. S. modica, Wolfcampian, most likely middle to BW24 BW24 Polk Knolls 40.67147 113.28205 fusulinid G.P.Wahlman Schwagerina cf. S. eolata, Schubertella spp. early late Wolfcampian (early Lenoxian) BW14 BW14 P*os Aragonite 40.67721 113.05872 conodont Mesogondolella bisselli, Sweetognathus whitei late Wolfcampian S.M. Ritter BW14 BW14 P*os Aragonite 40.67721 113.05872 fusulinid Pseudoschwagerina sp. late Wolfcampian S.M. Ritter BW12 BW12 *osc Aragonite 40.63655 113.02796 conodont Streptognathodus pawkuskaensis, Streptognathodus virgilicus early Virgilian S.M. Ritter BW13 BW13 *ol Ripple Valley 40.77859 113.05003 conodont Neognathodus sp. Desmoinesian or perhaps late Atokan S.M. Ritter BW9 BW9 *ol Aragonite 40.66021 113.03593 conodont Neognathodus sp., Idiognathodus sp., Adetognathus lautus Desmoinesian S.M. Ritter BW34 BW34 *e Floating Island 40.92284 113.64429 conodont Neognathodus, Idiognathodus early to middle Desmoniesian S.M. Ritter

Data from Thumb Ridge (Bylund, unpublished data) Latitude (N) WGS84 Longitude (W) WGS84 FB1 nd ^t Grayback Hills 40° 50.885' 113° 11.322' ammonoid Anasibirites sp. late Smithian K. Bylund FB2 nd ^t Grayback Hills 40° 50.827' 113° 11.266' ammonoid Owenites? sp. middle Smithian K. Bylund

Selected Data from Grayback Hills (Davies, 1980) Cadastral Bed Unit in Measured Section FD1 nd ^t Aragonite NW W1/2 SE1/4 s. 12, T1S, R12W unit 25 ammonoid Prohungarites sp. late Spathian B. Kummel FD1 nd ^t Aragonite NW W1/2 SE1/4 s. 12, T1S, R12W units 15, 11, 9, 5, 1 ammonoid Prohungarites sp., Prohungarites? sp., Keyserlingites bearlakensis, Keyserlingites bearlakensis? late Spathian B. Kummel FD1 nd ^t Aragonite NW W1/2 SE1/4 s. 12, T1S, R12W units 9, 5, 1 ammonoid Keyserlingites bearriverensis? late Spathian B. Kummel FD4 nd ^t Grayback Hills N1/2 SW1/4 SW1/4 s. 13, T1N, R12W unit 11 conodont Platyvillosus asperatus early Spathian David L. Clark FD4 nd ^t Grayback Hills N1/2 SW1/4 SW1/4 s. 13, T1N, R12W unit 11 conodont Neospathodus? triangularis early Spathian David L. Clark

Data from Grassy Mountains (Jordan, 1979a) Cadastral FJ10 f14051 P*os Grassy Mountains NW1/4 NE1/4 s. 33, T3N, R11W fusulinid Schwagerina sp. early Leonardian R.C. Douglass FJ9 f14050 P*os Grassy Mountains SW1/4 NE1/4 s. 10, T2N, R11W fusulinid Schwagerina sp. Wolfcampian R.C. Douglass FJ8 f14049 P*os Grassy Mountains NW1/4 SW1/4 s. 11, T2N, R11W fusulinid Pseudofusulina sp., Schwagerina sp., Pseudoschwagerina sp. Wolfcampian R.C. Douglass FJ7 GM15 P*os Grassy Mountains NW1/4 SW1/4 s. 11, T2N, R11W fusulinid Schwagerina sp., Pseudoschwagerina aff. convexa, Eoparafusulina sp. early late Wolfcampian C.H. Stevens FJ6 f14048 P*os Grassy Mountains NE1/4 SW1/4 s. 11, T2N, R11W fusulinid Triticites sp., Pseudofusulina sp., Schwagerina sp., Pseudoschwagerina sp. Wolfcampian R.C. Douglass FJ5 f14047 P*os Grassy Mountains SE1/4 SE1/4 s. 2, T2N, R11W fusulinid Schwagerina sp. Wolfcampian R.C. Douglass FJ4 f14046 P*os Grassy Mountains NW1/4 NW1/4 s. 12, T2N, R11W fusulinid Triticites sp., Pseudofusulina sp. Wolfcampian R.C. Douglass FJ3 f14045 P*os Grassy Mountains near center SW1/4 s. 12, T2N, R11W fusulinid Pseudofusulinella sp., Triticites sp., Pseudofusulina sp. Wolfcampian R.C. Douglass FJ2 f14044 *osi Grassy Mountains SE1/4 SE1/4 s. 1, T2N, R11W fusulinid Pseudofusulinella sp., Triticites sp. Virgilian R.C. Douglass FJ1 f14043 *osi Grassy Mountains SW1/4 SE1/4 s. 12, T2N, R11W fusulinid Bartramella?, Pseudofusulinella sp., Triticites sp. Virgilian R.C. Douglass 30 Utah Geological Survey

Table 6. Continued.

Map ID Sample ID Map Unit 7.5' Quadrangle Location Data Location Data Fossil Type Fauna Age Paleontologist

Data from Grassy Mountains (Doelling, 1964) Cadastral Bed Unit in Measured Section nd Polf Finger Ridge nd (Finger Ridge) Oquirrh Fm fusulinid Schwagerina sp. late early Wolfcampian B. Lambson nd P*os Grassy Mountains S1/2 s. 3, T2N, R11W Oquirrh Fm Unit 6, 21 fusulinid Schwagerina cf. communis, Schwagerina cf. japonica subsp. cincta early Leonardian B. Lambson nd P*os Grassy Mountains S1/2 s. 3, T2N, R11W Oquirrh Fm Unit 6, 5 fusulinid Schwagerina sp. (partially replaced) early Leonardian B. Lambson nd P*os Grassy Mountains S1/2 s. 3, T2N, R11W Oquirrh Fm Unit 6, 3 fusulinid Schwagerina cf. modica early Leonardian B. Lambson Early Permian (perhaps early nd P*os Grassy Mountains nd Oquirrh Fm Unit 5 fusulinid Pseudofusulinella sp., Triticites sp., ?Pseudofusulina sp., Bradyina sp., Schwagerina sp., Pseudoschwagerina sp. R.C. Douglass Leonardian to late Wolfcampian) nd P*os Grassy Mountains nd Oquirrh Fm Unit 5 (upper part) fusulinid Parafusulina shaksgamensis var. crassimarginata early Leonardian B. Lambson nd P*os Grassy Mountains nd Oquirrh Fm Unit 4 fusulinid Bradyina sp., Pseudofusulinella sp., Triticites sp., Schubertella aff. S. kingi, Pseudofusulina sp. (rare) Early Permian R.C Douglass nd P*os Grassy Mountains s. 2, T2N, R11W Oquirrh Fm Unit 4, 12 fusulinid Schwagerina sp. (partially replaced) middle to late Wolfcampian B. Lambson nd P*os Grassy Mountains s. 2, T2N, R11W Oquirrh Fm Unit 4, 1 fusulinid Schwagerina aff. providens, Schwagerina aff. wellsensis, Triticites sp. middle to late Wolfcampian B. Lambson nd P*os Grassy Mountains nd Oquirrh Fm Unit 3 fusulinid Pseudofusulinella?, Pseudofusulina, Triticites sp. (advanced form), Pseudofusulina sp. Early Permian? R.C. Douglass nd P*os Grassy Mountains NW1/4 s. 1, T2N, R11W Oquirrh Fm Unit 3, 9 fusulinid Triticites cellamagnus, Schwagerina aculeata middle to late Wolfcampian B. Lambson nd P*os Grassy Mountains NW1/4 s. 1, T2N, R11W Oquirrh Fm Unit 3, 8 fusulinid Triticites aff. providens middle to late Wolfcampian B. Lambson nd P*os Grassy Mountains NW1/4 s. 1, T2N, R11W Oquirrh Fm Unit 3, 3 fusulinid Triticites cf. rockensis, Schwagerina sp.? early Wolfcampian* B. Lambson nd P*os Grassy Mountains NW1/4 s. 1, T2N, R11W Oquirrh Fm Unit 3, 1 fusulinid Triticites cf. rockensis, Pseudofusulinella sp. early Wolfcampian* B. Lambson nd P*os Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 27 fusulinid Triticites creekensis, Pseudofusulinella sp. Wolfcampian* B. Lambson nd P*os Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 25 fusulinid Triticites meeki, Pseudofusulinella utahensis Wolfcampian* B. Lambson nd P*os Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 23 fusulinid Triticites rockensis, Triticites creekensis, Pseudofusulinella sp. Wolfcampian* B. Lambson nd P*os Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 22 fusulinid Triticites cf. creekensis, Pseudofusulinella utahensis, Bartramella heglarensis Wolfcampian* B. Lambson nd P*os Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 18 fusulinid Triticites notus, Psedofusulinella cf. utahensis Wolfcampian* B. Lambson nd *osi Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 17 fusulinid Triticites hobblensis Virgilian B. Lambson nd *osi Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 16 fusulinid Triticites cf. rhodesi Virgilian B. Lambson nd *osi Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 14 fusulinid Triticites sp. Virgilian B. Lambson nd *osi Grassy Mountains s. 12, T2N, R11W Oquirrh Fm Unit 2, 3 fusulinid Triticites gallowayi, Pseudofusulinella sp. Virgilian B. Lambson nd *osi Grassy Mountains nd Oquirrh Fm Unit 2 (lower part) fusulinid Triticites app. (2 species) Virgilian R.C. Douglass nd *osi Grassy Mountains nd Oquirrh Fm Unit 2 (lower part) fusulinid Schubertella sp. aff. S. kingi Virgilian R.C. Douglass nd *ol Grassy Mountains NE1/4 s. 12, T2N, R11W Oquirrh Fm Unit 1, 29 fusulinid Fusulina cf. haworthi Desmoinesian B. Lambson nd *ol Grassy Mountains NE1/4 s. 12, T2N, R11W Oquirrh Fm Unit 1, 21 fusulinid Fusulina sp. (partial replacement) Desmoinesian B. Lambson

Notes: Map ID and map unit correspond to plate 1. Sample locations for Doelling (1964), Davies (1980), and Jordan (1979a) are approximate. nd is no data. Samples from Doelling (1964) are not included on the map. Davies (1980) small measured sections are indicated by fossil symbols. FD2, FD3, FD3AB are other section locations of Davies (1980) that contain fossils. Ages from paleontologists listed. * Age reevaluated by G.P. Wahlman to be latest Virgilian "Bursumian/Newwellian." Triticites hobblensis is lower Virgilian (Thompson and others, 1950). Triticites rockensis may be the juvenile, since was described as starved fauna by Thompson (1954). Paleontologist Affiliation: S.M. Ritter (Brigham Young Univ.), K. Bylund (independent researcher), B. Kummel (Harvard Univ.), David L. Clark (Univ. of Wisconsin, Madison), B. Lambson (Shell Oil Co.), R.C. Douglass (USGS), C.H. Stevens (San Jose State Univ.), G.P. Wahlman (independent).