Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association ISSN 2380-7601 Volume 6 2019 © 2019 Utah Geological Association. All rights reserved. For permission to copy and distribute, see the following page or visit the UGA website at www.utahgeology.org for information. Email inquiries to GIW@utahgeology.org. STRATIGRAPHIC SETTING OF FOSSIL LOG SITES IN THE MORRISON FORMATION (UPPER JURASSIC) NEAR DINOSAUR NATIONAL MONUMENT, UINTAH COUNTY, UTAH, USA Douglas A. Sprinkel, Mary Beth Bennis, Dale E. Gray, and Carole T. Gee Theme Issue An Ecosystem We Thought We Knew— The Emerging Complexities of the Morrison Formation SOCIETY OF VERTEBRATE PALEONTOLOGY Annual Meeting, October 26 – 29, 2016 Grand America Hotel Salt Lake City, Utah, USA GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association ISSN 2380-7601 Production Cover Design and Desktop Publishing Douglas A. Sprinkel Cover West view of the Morrison Formation at Rain- bow Draw. The fossil log horizon is in the green- ish-colored siltstone beds near the center of the photograph. The Cretaceous Cedar Mountain through the Frontier Formations are exposed on the distant ridge. See figure 7 for details. Inset photo of a fossil log typically found in Rainbow Draw. i Become a member of the UGA to help support the work of the Association and receive notices for monthly meetings, annual field conferences, and new publi- cations. Annual membership is $20 and annual student membership is only $5. Visit the UGA website at www.utahgeology.org for information and membership application. The UGA board is elected annually by a voting process through UGA members. However, the UGA is a volunteer-driven organization, and we welcome your voluntary service. If you would like to participate please contact the current president or committee member corresponding with the area in which you would like to volunteer. Utah Geological Association formed in 1970 from a merger of the Utah Geological Society, founded in 1946, and the Intermountain Association of Geologists, founded in 1949. Affiliated with the American Association of Petroleum Geologists. Volume 6 2019 This is an open-access article in which the Utah Geological Association permits unrestricted use, distribution, and reproduction of text and figures that are not noted as copyrighted, provided the original author and source are credited. Editors President Peter Nielsen peternielsen@utah.gov 801.537.3359 President-Elect Leslie Heppler lheppler@utah.gov 801.538.5257 Program Chair Gregory Schlenker gcsgeoscience@gmail.com 801.745.0262 Treasurer Dave Garbrecht garbrechtd@yahoo.com 801.916.1911 Secretary George Condrat gcondrat@loughlinwater.com 435.649.4005 Past President Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 UGA Board October 2018 – September 2019 UGA Committees Environmental Affairs Craig Eaton eaton@ihi-env.com 801.633.9396 Geologic Road Sign Terry Massoth twmassoth@hotmail.com 801.541.6258 Historian Paul Anderson paul@pbageo.com 801.364.6613 Outreach Greg Nielson gnielson@weber.edu 801.626.6394 Membership Rick Ford rford@weber.edu 801.626.6942 Public Education Paul Jewell pwjewell@mines.utah.edu 801.581.6636 Matt Affolter gfl247@yahoo.com Publications Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Publicity Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Social/Recreation Roger Bon rogerbon@xmission.com 801.942.0533 AAPG House of Delegates 2017–2020 Term Tom Chidsey tomchidsey@utah.gov 801.537.3364 State Mapping Advisory Committe UGA Representative Jason Blake blake-j@comcast.net 435.658.3423 UGA Newsletter Newsletter Editor Bill Lund uga.newsletter@gmail.com 435.590.1338 UGA Website www.utahgeology.org Webmasters Paul Inkenbrandt paulinkenbrandt@utah.gov 801.537.3361 Earthquake Safety Committe Chair Grant Willis gwillis@utah.gov 801.537.3355 Douglas A. Sprinkel Utah Geological Survey 801.391.1977 GIW@utahgeology.org Bart J. Kowallis Brigham Young University 801.422.2467 bkowallis@gmail.com Thomas C. Chidsey, Jr. Utah Geological Survey 801.537.3364 tomchidsey@utah.gov Steven Schamel GeoX Consulting, Inc. 801.583-1146 geox-slc@comcast.net Society of Vertebrate Paleontology Editors Kelli C. Trujillo — University of Wyoming John Foster — Utah Field House of Natural History State Park Museum Cary Woodruff — University of Toronto Octavio Mateus — Universidade Nova de Lisboa GEOLOGY OF THE INTERMOUNTAIN WEST an open-access journal of the Utah Geological Association Volume 6 2019 61 ABSTRACT The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The discovery of several well-preserved, relatively intact, fossil logs at several locations in Rainbow Draw and one location in Miners Draw, both near Dinosaur National Monument (Utah), has provided an opportunity to study the local paleobotany, stratigraphy, and sedimentology of the Morrison Formation in northeastern Utah. The Morrison Formation in northeastern Utah consists of four members. In ascending chronostratigraphic order, they are the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. The lithology (including the pres- ence of glauconite grains) and fossil assemblage of the lower two members (Windy Hill and Tidwell) indicate a marine to marginal marine (coastal plain) depositional environment, whereas the lithology, fossil flora and fauna assemblage of the upper two members (Salt Wash and Brushy Basin) indicate a fluvial–lacustrine depositional environment. At least 10 fossil log sites in Rainbow Draw have been documented so far, and geologic mapping indicates that the logs and wood all occur in the same stratigraphic interval within the Salt Wash Member, approximately 17 to 27 m above the base of the member. The unit containing the logs and wood is about 11 m thick and consists of very fine to fine-grained sandstone and siltstone with indistinct bedding and no discernible sedimentary fea- tures. The logs are siliceous, some have a coaly exterior, and they range in exposed length from 0.5 to 11 m and reach diameters up to 1.1 m. In the Miners Draw area, a single siliceous log is documented in the upper part of the Salt Wash Member within a silty sandstone unit that is 4 m thick; its exposed length is about 6 m. Although the correlation of the Miners Draw log-bearing interval to the interval in Rainbow Draw is uncertain, both units are lithologically similar and both occur in the upper part of the Salt Wash Member. The logs have been identified as araucariaceous conifers that pertain to the same taxon originally described as Araucarioxylon hoodii Tidwell et Medlyn 1993 from Mt. Ellen in the Henry Mountains of southern Utah. Concurrent systematic work will prompt a nomenclatural transfer of this species to the genus Agathoxylon. Based on the abundance of large fossil logs and wood in the same stratigraphic interval in Rainbow Draw, we hypothesize that the area was covered by stands of moderately large trees of araucariaceous conifers. The sedimen- tological evidence suggests that the trees were not transported far from their original site of growth before they were deposited in a low-energy floodplain environment. Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Douglas A. Sprinkel1, Mary Beth Bennis2, Dale E. Gray2, and Carole T. Gee3 1Utah Geological Survey, PO Box 146100, Salt Lake City, UT 84114, USA; douglassprinkel@utah.gov 2Utah Field House of Natural History State Park Museum, 496 E. Main, Vernal, UT 84078, USA; marybethbennis@utah.gov, daleegr@aim.com 3Institute of Geosciences, Division of Paleontology, University of Bonn, Nussallee 8, 53115 Bonn, Germany; cgee@uni-bonn.de Citation for this article. Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T., 2019, Stratigraphic setting of fossil log sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA: Geology of the Intermountain West, v. 6, p. 61–76. © 2019 Utah Geological Association. All rights reserved. For permission to use, copy, or distribute see the preceeding page or the UGA website, www.utahgeology.org, for information. Email inquiries to GIW@utahgeology.org. 62 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 INTRODUCTION The Upper Jurassic Morrison Formation is a spec- tacular and easily recognizable formation across the Colorado Plateau, and is distinctive because of its ar- ray of rainbow-colored mudstone, siltstone, and sand- stone beds that typically form a “badlands” landscape. In northeastern Utah, it is well-exposed along the south flank of the Uinta Mountains (figure 1) and around Split Mountain and the Yampa and Blue Mountain Plateaus in and around Dinosaur National Monument (figure 2). The Morrison gained its fame from the discovery of well-preserved dinosaur bones on the south flank of Split Mountain in August 1909 by Earl Douglass, a pa- leontologist with the Carnegie Museum of Pittsburgh (Douglass, 2009). Subsequent development of the Carn- egie Quarry (figure 2) produced a rich and diverse dino- saur assemblage (Elder, 1999; Engelmann, 1999; Turner and Peterson, 1999; Chure and others, 2006; Carpenter, 2013). In addition to dinosaurs, the Morrison has pro- duced other vertebrate fossils (e.g., pterosaurs, crocody- lomorphs, and mammals), invertebrate fossils, and fos- sil insects (Engelmann, 1999; Evans and Chure, 1999; Hasiotis, 2004; Chure and others, 2006). Fossil wood is also commonly found in the Morrison Formation, but it is mostly scrappy pieces preserved in channel sandstone Castle Dale Coalville Duchesne Green River Gunnison Heber City Kamas Manila Manti Nephi Salt Lake City Tabiona Vernal Price Provo Jensen Morrison Fm Outcrop Belt Uinta Basin Boundary Dinosaur National Monument WYOMING C O LO R AD O UTAH U TAH 109° 41° 40.5° 40° 39.5° 39° 112° 111° 110° 109° 112° 111° 110° 40° 39.5° 41° 40.5° 39° ´ Study Area UINTA BASIN UI NTA MO UNTAI NS W A S A T C H R A N G E Utah Lake Great Salt Lake Flaming Gorge Reservoir 0 10 20 30 40 50 60 70 80 90 100 Mi 0 30 60 90 120 150 Km Gr ee n Ri ve r Green River Yampa River W hite River Duchesne River Strawberry River " " " " " " " " " " " " " " " " Figure 1 Figure 1. Regional map showing the Morrison Formation study area in the eastern Uinta Mountains of northeastern Utah, USA. Morrison outcrop locations from Hintze and others (2000). 63 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 and conglomeratic depositional units in the Salt Wash and Brushy Basin Members (Engelmann, 1999; Gee and others, 2014). In some places, the Morrison con- tains fossil logs of varying sizes, which occur as solitary logs or in clusters (Gee, unpublished data). Engelmann (1999) surveyed several National Park Service units in Utah and surrounding states and documented 34 sites where log segments a few meters in length were found in the Morrison Formation. He described one site at Di- nosaur National Monument as “…a large area covered by silicified logs of considerable diameter, possibly a log jam”(Engelmann, 1993). Escalante Petrified Forest State Park, near the town of Escalante in south-central Utah, is another location with a concentration of fossil logs in the Morrison Formation. These silicified (ag- atized) logs occur in a conglomerate bed in the upper part of the Brushy Basin Member (Morgan and others, 2012). Many other unpublished sites in Utah had con- centrations of fossil logs in the Morrison, but many of these sites have been picked clean over the years by col- lectors (James Kirkland, Utah Geological Survey, verbal communication, March 2018). A reconnaissance paleontological survey of the Morrison Formation by Mary Beth Bennis and Dale Gray (Utah Field House of Natural History State Park Museum) on Bureau of Land Management lands east of Vernal, Utah, and outside Dinosaur National Monu- ment, identified two areas that have large, relatively in- tact, and well-preserved fossil logs. One area is located south of Blue Mountain Plateau near Miners Draw, and the other area is north of Dinosaur National Monument in Rainbow Draw (figure 2). The Rainbow Draw area is of particular importance because it contains a concen- tration of as many as 11 logs in a relatively small area (240,000 m2 or about 60 acres). The Miners Draw site is located in an unnamed trib- utary of Miners Draw (figure 2) where a single log was found at the base of a Morrison Formation slope (figure 3). The Rainbow Draw area is located northeast of Ver- nal and north of Dinosaur National Monument (figure 2). There, 10 fossil logs were discovered in beds in the area. The logs are concentrated into two groups with- in the 60-acre surveyed area. In each group, the fossil logs were somewhat dispersed, except for one site in the western group with a cluster of three large logs (site 3). It is unclear if this cluster of logs represents three indi- vidual trees or if it represents only one tree trunk that has broken into segments that have moved downslope. All fossil logs in the Miners Draw and Rainbow Draw areas were found in the Salt Wash Member of the Mor- rison Formation, but it was not clear at the time of the survey if the logs were at the same stratigraphic horizon " " " Red Fleet Reservoir Steinaker Reservoir Vernal Naples Jensen Dry Fork A shley Creek Jones Hole Cree k Big Brush Creek Li t t le B ru s h C re ek Clif f C reek Gr een River B r ush C r eek Gree n River D eep C reek Min ers Draw Morrison Fm Outcrop Dinosaur National Monument ´ Split Mountain Yampa Plateau Blue Mountain Rainbow Draw Area M iners Dra w Area Carnegie Quarry 0 4 8 12 16 20 Km 0 2 4 6 8 10 12 Mi U I N TA M O U N T AINS U I N T A B ASIN £¤40 £¤40 £¤191 £¤191 Æ·45 Æ·88 Æ·121 £¤40 Figure 2. Map showing the Morrison Formation outcrop belt (marked in green) in and around Dinosaur Nation- al Monument and the location of the re- nowned Carnegie Quarry. The Miners Draw area is south of the Blue Moun- tain Plateau and Rainbow Draw is due north of Dinosaur National Monument. Both areas are east of the city of Vernal, Utah. Morrison outcrop locations from Hintze and others (2000). 64 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 or if they were merely preserved in strata of similar dep- ositional environments. Subsequent visits to both areas were made to measure the logs, collect hand samples for paleobotanical analysis, and describe and measure Morrison Formation sections. Geologic mapping was conducted in the field on aerial photographs and im- agery to help trace member contacts and key beds. The purpose of this study is to describe the Morrison For- mation strata, especially those related to the fossil logs, and to place the logs within a stratigraphic framework for the interpretation of the depositional environment of the log-bearing intervals at both locations. GEOLOGIC SETTING OF THE FOSSIL LOG SITES The Miners Draw and Rainbow Draw areas are situ- ated along the flanks of highlands—Blue Mountain Pla- teau, Yampa Plateau, and Split Mountain—that formed during the Laramide uplift of the Uinta Mountains (figure 2) (Stone, 1993; Gregson and others, 2010). The highlands rose mostly along high-angle reverse faults, Miners Draw fault to the south and Island Park fault to the north. The formations within the highlands were folded into a series of monoclines and asymmetrical an- ticlines (Hansen and others, 1983; Hansen, 1986; Sprin- kel, 2006, 2007). The bedrock stratigraphy in the Miners Draw and Rainbow Draw areas include (in ascending chronostratigraphic order) the Upper Jurassic Stump and Morrison Formations, the Lower Cretaceous Ce- dar Mountain and Dakota Formations, and the Upper Cretaceous Mowry and Frontier Formations. In the Miners Draw area, the formations wrap around a gen- tly plunging anticlinal nose that is faulted on the north limb (figure 4). Three partial stratigraphic sections were measured to produce a composite section from the top of the Stump Formation to the base of the Cedar Mountain Formation because of the distance between the exposed base and top of the Morrison Formation and stratigraphic position of the fossil logs. Key marker beds were used to offset between the section segments. In Rainbow Draw, the formations generally dip less than 20° southwest, although the Morrison Formation is very gently folded into a broad, low-amplitude syn- cline (figure 5). Jms Fossil log site Jmbu Jmbl Kcb Figure 3. Fossil log site in the Miners Draw area in the upper Salt Wash Member of the Morrison Formation (Jms). The Brushy Basin Member of the Morrison Formation is divided into a lower banded unit (Jmbl) and an upper gray unit (Jmbu). The Buckhorn Conglomerate of the Cedar Mountain Formation (Kcb) caps the Morrison Formation. The yellow dashed line represents the upper part of the Trail Creek measured section. Blue Mountain Plateau is the highland in the distance. View to the northwest. 65 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 MORRISON FORMATION STRATIGRAPHY The Morrison Formation in northeastern Utah con- sists of four members. In ascending chronostratigraph- ic order, they are the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. The Windy Hill Member is composed of siltstone, mudstone, and thin-bedded rippled limestone that ranges from 4 to 20 m thick (figures 6A and 6B), and the invertebrate fossil assem- blage and glauconite grains indicate marine deposition (Turner and Peterson, 1999). The Tidwell Member is composed of cross-bedded and rippled siltstone and sandstone, and thin shale beds (figure 6C). Marine E ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! E ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! J ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! JE E ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! E J J #* Qae Kcu Kmr Kd Qac Kcu KcuQaf Qac Kcb Kd QafQac Kcb Qac Jms Kf Qmt Kmr Jmb Qms QacKd Qac Kcu Jmb Kcb Qmt Qc Jms Jms Jmtw Js Qc Qms (Jmb) Qc Js Qac Kcu Qac Kd Qc Qc Jms Js Qc Qac Jmtw Js Qms Qac Kcu Kcb Jmb Jms Jmtw Js Qac Js R. 25 E. ´ Explanation #* Fossil log site o p Measured Sections Bedding, inclined, field measured Bedding, inclined, calculated Map area Contact ! ! ! ! ! !ENormal fault, concealed ENormal fault, approximately located ! ! ! ! ! ! ! ! Fold, anticline, upright, concealed Fold, anticline, upright, well located Qac - Mixed alluvium and collovium Qae - Mixed alluvium amd eolian Qaf - Alluvial fan Qc - Colluvium Qmt - Talus Qms - Landslide Qms (Jmb) - Landslide (Brushy Basin Member) Qms (Jms) - Landslide (Salt Wash Member) Kf - Frontier Formation Kmr - Mowry Shale Kd - Dakota Formation Kcu - Upper member of Cedar Mountain Formation Kcb - Buckhorn Conglomerate Member of Cedar Mountain Formation Jmb - Brushy Basin Member of Morrison Formation Jms - Salt Wash Member of Morrison Formation Jmtw - Tidwell-Windy Hill Members of Morrison Formation Js - Stump Formation 3 6 S. T. 1:10,000 1 cm = 100 mScale Contour Interval = 20 feet Qms (Jmb) o o o p o o p p p 7 17 25 15 7 6 14 12 13 9 p 0 1,000 2,000500 Feet 0 140 280 420 560 Meters Figure 4. Geologic map of the Miners Draw area fossil log site. The Morrison Formation overlies the Stump Formation and underlies the Buckhorn Conglomerate Member of the Cedar Mountain Formation. The Morrison includes the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. We further divided the Brushy Basin Member into a lower banded unit and an upper gray unit. We measured the members of the Morrison in three sections at Blue Mountain; the Windy Hill to the lower banded member is in the northeast part of the map area, whereas the top of the Salt Wash Member, the lower banded and upper gray unit of the Brushy Basin are in an offset section in the southwest part of the map area because of folding, faulting, and landslides. The fossil log site occurs in the upper part of the Salt Wash Member, about 17 m below the Brushy Basin Member, along the southwest offset measured section. 66 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 Figure 5. (A) Geologic map and (B) cross section of the Rainbow Draw area fossil log sites. The Morrison Formation overlies the Stump Formation and underlies the Cedar Mountain Formation in Rainbow Draw. In the mapped area, the Morrison in- cludes the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. The fossil log sites are concentrated in two groups on separate ridges. Both groups of logs occur in light-colored, fine-grained sandstone and siltstone below a mostly reddish-col- ored siltstone that was used as a marker bed (blue dashed line). ´ E E E E! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! E E ! ! ! ! ! ! ! E! ! ! ! ! ! ! ! ! ! ! ! ! E E E " o o o o p p p o p p p #* #* #*#*#* #*#* #* #* #* #* Site 1 Site 2 Sites 3a–3c Site 4 Site 5 Site 6 Site 7 Site 8 Site 9 5 11 10 7 14 19 7 10 8 14 9 Qc Qc Jms Jmb Qc Jms Jms Qms Qac Jms Jmb Kcu Qap Qc Qc Jmtw Qc Jms Js Qc Jmtw Jms Jms Qc Jmb Jmb Jms Jms Qac Jms Qc Qc Jms Qc Js Qc Qap R. 24 E. 2423 A A' Explanation #* Fossil log site o Bedding, inclined, field measured p Bedding, inclined, calculated Cross section A-A' Measured section Map boundary Contact ENormal fault, well located Normal fault, approximately located ! ! ! ! ! Normal fault, concealed Syncline Marker bed Formations Qap - Piedmont gravel Qac - Mixed alluvium and colluvium Qc - Colluvium Qms - Landslide Kcu - Upper member of Cedar Mountain Formation Jmb - Brushy Basin Member of Morrison Formation Jms - Salt Wash Member of Morrison Formation Jmtw - Tidwell-Windy Hill Members of Morrison Formation Js - Stump Formation 3 T. S. 1 cm = 55.5 m1:5550Scale Contour Interval = 40 feet A 0 1,000 2,000 Feet 0 125 250 375 500 Meters 67 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 fossil dinoflagellate tests were recovered from the Tid- well Member near Dinosaur National Monument, and some glauconitic sandstone occurs as well (Turner and Peterson, 1999). The Tidwell also contains abundant pinkish-colored botryoidal chert (figure 6D) (also re- ferred to as “welded chert”) near or at the base of the member, which has been recognized throughout the region (King and Merriam, 1969; Peterson, 1980). A marginal marine to coastal plain (supralittoral) depo- sitional environment is indicated for the Tidwell Mem- ber in northeastern Utah (Turner and Peterson, 1999), but it may be somewhat fluvial near the top as indicated by the bioturbated and mottled beds (appendix). The Tidwell Member in northeastern Utah ranges from 9 to 17 m thick. The Salt Wash Member is composed of interbedded sandstone, siltstone, and mudstone with some beds of channel-form pebble sandstone, as well as conglomerate that ranges from 75 to 80 m thick (figure 7A). The Salt Wash was deposited in a fluvial system (Peterson, 1980; Turner and Peterson, 1999, 2004). The capping Brushy Basin Member is composed of a lower banded unit of siltstone, silty sandstone, and clay-rich mudstone (about 12 to 16 m thick) as well as an upper gray unit of predominately popcorn-weathering mud- stone (about 70 to 88 m thick) and ranges from 82 to 104 m thick (figures 3 and 7B). The Brushy Basin Mem- Jmw Js Jmt Jmt Jms A B C D Figure 6. Photographs of lower members of the Morrison Formation and contacts within the study area. (A) The Windy Hill Member of the Morrison Formation (Jmw) overlies the Stump Formation (Js) and underlies the Tidwell Member on the north flank of Split Mountain. The Windy Hill is composed of siltstone, mudstone, and thin-bedded rip- pled limestone. (B) Rippled limestone in the Windy Hill Member on the north flank of Split Mountain. (C) Contact between the Tidwell and Salt Wash Members of the Morrison Formation near the measured section in Rainbow Draw. (D) Example of the botryoidal chert commonly found near the base of the Tidwell Member. Specimen collected south of the Green River between Split Mountain and Blue Mountain Plateau. 68 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 ber was deposited in a fluvial–lacustrine environment (Turner and Peterson, 1999, 2004) with significant in- put of volcanic ash (Turner and Fishman, 1991; Chris- tiansen and others, 2015). The Morrison Formation overlies the Stump Forma- tion throughout northeastern Utah. The nature of the contact between the Stump and Morrison is complex, however. Conventional thinking is that the contact in northeastern Utah is unconformable (the J-5 unconfor- mity of Pipiringos and O’Sullivan [1978]), similar to ex- A B Jms Jmbu Jmbl Figure 7. Photographs of the Salt Wash and Brushy Basin Members of the Morrison Formation. (A) Salt Wash Member near the measured section at Miners Draw showing varicolored siltstone beds and the brownish-gray channel sandstone beds; view to the northeast. (B) View of the Salt Wash and Brushy Basin Members from near the top of the measured sec- tion at Rainbow Draw; view to the west. The yellow arrow points to the fossil log-bearing interval, which is overlain by the reddish-colored marker bed. The Brushy Basin is divided into a lower banded unit and an upper gray unit. The Cretaceous Cedar Mountain through the Frontier Formations are exposed on the distant ridge. 69 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 posures in east-central Utah where the Tidwell Member of the Morrison unconformably overlies the Summer- ville and older formations (Peterson, 1988). However, Turner and Peterson (1999) noted that the J-5 surface is unconformable in some areas and conformable in others. Other workers in northeastern Utah showed the boundary as conformable in the eastern Uinta Moun- tains and Uinta Basin (e.g., Currie, 1998; Bilbey and others, 2005). Our examination of the contact in the Miners Draw and Rainbow Draw areas indicates that it appears to be gradational and conformable. The Upper Jurassic Morrison Formation is uncon- formably overlain by the Lower Cretaceous Cedar Mountain Formation. Picking the contact between the two formations can be difficult, despite being an un- conformity (K-1), because their similar lithologies are easily weathered to clay flats or clay-covered slopes. Lithostratigraphic, biostratigraphic, and chemostrati- graphic criteria are emerging that will help identify the contact (see Cifelli and others, 1997; Kirkland and others, 1999, 2003, 2011, 2016; Ludvigson and others, 2003, 2015; Greenhalgh and Britt, 2007; Kirkland, 2007; Kirkland and Madsen, 2007; Sprinkel and others, 2012). For example, the basal unit of the Cedar Mountain For- mation can include the Buckhorn Conglomerate Mem- ber, a cobble and boulder conglomerate that varies in thickness and typically forms a resistant cliff above the Morrison Formation (Stokes, 1952; Kirkland and oth- ers, 2016), as it does in the Miners Draw area (figure 8A). Where the Buckhorn Conglomerate is missing, the basal bed of the Cedar Mountain Formation is typically mottled, yellowish-orange, chert-pebble-bearing mud- stone that underlies the first Cedar Mountain calcrete bed (Sprinkel and others, 2012; Kirkland and others, 2016), as it is in the Rainbow Draw area (figure 8B). STRATIGRAPHY OF THE FOSSIL LOG SITES Sections of the Morrison Formation were measured at the Miners Draw and Rainbow Draw areas to de- scribe beds and place the fossil log sites in stratigraphic and sedimentological context. At the Miners Draw area, several sections were measured to capture the entire Morrison Formation (Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members) and the stratigraphic hori- zon of the fossil log site because distance between base and top of the Morrison is large and complicated by be- ing exposed on the nose of a southwest-plunging anti- cline (figure 4). The contact between the lower band- ed and upper gray units of the Brushy Basin Member was used to trace around the Miners Draw area to the fossil log site. The section measured at Rainbow Draw included the Windy Hill, Tidwell, and part of the Salt Wash Members; the Salt Wash Member was measured only through the fossil log-bearing unit to a light green- ish- to reddish-colored siltstone marker unit, which was overlain by a light-gray sandstone unit that capped the ridge. This distinctive marker unit was mapped and used to correlate between the two groups of fossil logs sites within the Rainbow Draw area. Salt Wash Member at the Miners Draw Area The Salt Wash Member at Miners Draw consists of fine- to coarse-grained, cross-bedded sandstone with some conglomeratic sandstone and conglomer- ate beds, silty sandstone, and siltstone (figure 9). The coarse-grained sandstone, conglomeratic sandstone, and conglomerate beds are mostly shades of brown- ish gray. The fine-grained and silty sandstone beds are light brownish-gray to greenish gray and medium red- dish-brown. The siltstone beds are greenish gray to dark reddish-brown, somewhat clayey, and have a pseudo popcorn-weathering appearance. Black and orange-col- ored accessory grains are common in the sandstone beds. The coarser grained beds typically form resistant ledges and may include fossil wood and bone frag- ments, whereas the finer grained beds tend to be slope forming (appendix). The fossil log-bearing interval at Miners Draw is light greenish-gray to brownish-gray, silty to very fine grained sandstone that is slightly clay rich with indistinct bedding and no discernable sedi- mentary features. The interval is weakly cemented and poorly exposed but the log weathers out in relief. The interval is 4.3 m thick and the fossil log occurs 3.0 m above the base of the unit and 7.8 m below the top of the Salt Wash Member (figure 3). The fossil log is about 6 m long and its long axis is oriented east–west (see Gee and others, 2019, for additional log dimensions). 70 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 Salt Wash Member in the Rainbow Draw Area The Salt Wash Member in Rainbow Draw consists of very fine to fine-grained sandstone, some medium- to coarse-grained sandstone, siltstone, and mudstone (figure 9; appendix). The sandstone beds are very light gray and light to medium greenish-gray and are medi- um to thin bedded and tabular with small-scale planar Figure 8. The Lower Cretaceous Cedar Mountain Formation unconformably overlies the Brushy Basin Member of the Mor- rison Formation. (A) In the Miners Draw area, the Buckhorn Conglomerate Member of the Cedar Mountain (conglomerate boulder in the foreground) makes it easy to locate the contact between the two formations; view to the northeast. (B) In many places, the contact between the Morrison and Cedar Mountain Formations is difficult to locate where the Buckhorn Con- glomerate Member is missing. Here the contact (white line) is placed at a chert-pebble, mottled, yellowish-orange mudstone that underlies the first Cedar Mountain calcrete bed. Photograph taken south of U.S. Highway 40 between Steinaker and Red Fleet Reservoirs; view to the northeast. 71 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 m ud st on e si lts to ne si lty s an ds to ne sa nd st on e co ng lo m er at ic s an ds to ne cr os s- be dd ed s an ds to ne co ng lo m er at e ca lc re te pi nk a m yg da lo id al c he rt si lts to ne a nd s an ds to ne sa nd y lim es to ne fo ss il lo g si te fo ss il lo g si te 1 fo ss il lo g si te 1 w oo d- bo ne fr ag m en ts m ud si lt sa nd gr av el f m c m ud si lt sa nd gr av el f m c m ud si lt sa nd gr av el f m c 10 0 18 0 15 0 50 10 0 18 0 15 0 50 10 0 18 0 15 0 50 m ud si lt sa nd gr av el f m c M et er m ud si lt sa nd gr av el f m c M et er m ud si lt sa nd gr av el f m c M et er 1 12 3- 4 6- 7 8- 11 5 23456789101112 13 15 17 up pe r g ra y pa rt no t m ea su re d he re 14 16 123456789 3- 45 2 16- 7891011 co ve re d co ve re d co ve re d an d no t m ea su re d Br us hy B as in M em be r Bu ck ho rn C on gl om er at e M em be r o f Ce da r M ou nt ai n Fo rm at io n Ce da r M ou nt ai n Fo rm at io n Sa lt W as h M em be r St um p Fo rm at io n Morrison Formation M in er s D ra w S ec tio n (N or th ea st -M id dl e O �s et ) N W 1/ 4 N E1 /4 s ec tio n 3, T . 6 S ., R. 2 5 E. M in er s D ra w S ec tio n (S ou th w es t O �s et ) SE 1/ 4 SW 1/ 4 se ct io n 3, T . 6 S ., R. 2 5 E. Ra in bo w D ra w S ec tio n N W 1/ 4 N W 1/ 4 se ct io n 24 , T . 3 S ., R. 2 4 E. Bu ck ho rn C on gl om er at e M em be r is n ot p re se nt a t R ai nb ow D ra w estimated thickness of unmeasured Salt Wash and Brushy Basin Members from Turner and Peterson (1999) J- 5 un co nf or m ity (? ) SO U TH N O RT H co lo rs in s ec tio ns a pp ro xi m at es ou tc ro p co lo rs Ti dw el l M em be r W in dy H ill M em be r Ex pl an at io n Fi gu re 9 Fi gu re 9 . S tr at ig ra ph ic se ct io ns m ea su re d in th e M in er s D ra w an d Ra in bo w D ra w ar ea s s ho w in g th e f os sil lo g- be ar in g in te rv al s. La be l n um be rs r ef er to m ea su re d se ct io n un its in ap pe nd ix . 72 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 cross-beds and some ripple laminations. The siltstone beds are light to medium greenish-gray and mottled reddish-brown, whereas the mudstone beds are dark greenish-gray, somewhat clayey, slightly micaceous, and fissile. The fossil logs are concentrated in two groups. The measured section of the Salt Wash Member began at the eastern group of logs along a small drainage that con- tains the top of the Stump Formation to the top of a ridge where the fossil log-bearing interval and the over- lying marker bed are exposed (figure 5A). The fossil log-bearing interval along the measured section is light to medium greenish-gray, very fine to fine-grained, fri- able sandstone and siltstone with indistinct bedding and no discernable sedimentary structures. The inter- val is generally slope forming and has fossil wood frag- ments scattered on the slope. The fossil log along the measured section at site 1 is 11 m in length, moderately well exposed, and fairly intact (figure 10). The log-bear- ing interval is 10.8 m thick, and the fossil log occurs 1.9 m below the base of the overlying marker bed and 29.7 m above the base of the Salt Wash Member (figure 9). A short fossil log is located a short distance along strike of the measured section. That log occurs about 2 m above the base of the Salt Wash Member. Other fossil log sites of the eastern group are along the ridge within the log-bearing interval. These sites were also in the light to medium greenish-gray, very fine to fine-grained, friable sandstone and siltstone at slightly varying stratigraphic levels within the interval, except the logs at site 9 (see figure 5A). The log at site 9 is about 10 to 12 m lower than the other logs on the ridge. The only other fossil log measured in the eastern group is at site 7 (see fig- ure 5A) where it is partially exposed in the hillside, is slightly more than 0.5 m in length, and has a convoluted wood grain on its surface. The western group of logs is located along a low ridge about 500 m northwest of the eastern group. No sections were measured through the western group, but detailed geologic mapping and comparison of the stra- tigraphy indicates that the log-bearing interval in the western group occurs in the same stratigraphic interval as the eastern group (figure 5). As in the eastern group, the log-bearing interval in the western group is light to medium greenish-gray, very fine to fine-grained, fria- ble sandstone and siltstone with indistinct bedding and no discernable sedimentary structures. The measured lengths of the fossil logs range from about 1.3 to 2.3 m, with diameters ranging from 0.5 to 1.1 m. All sites within each group contain a single log, with the exception of site 1 (eastern group), which has two closely spaced logs, and site 3 (western group), which has multiple closely spaced log segments. The log seg- ments at site 3 may represent multiple logs or a single log that has moved downslope because of erosion and broken apart. The measured azimuths of the long axis of the fossil logs in Rainbow Draw area indicate that they are randomly oriented. GENERAL DESCRIPTION OF THE FOSSIL WOOD Only a basic description of the fossil logs is present- ed here because a detailed description is being made by Gee and others (2019). The fossil logs in both the Min- ers Draw and Rainbow Draw areas are shades of light to medium brown in color and siliceous, and some have a Figure 10. Fossil log at site 1 in Rainbow Draw (see figure 5A). This fossil log occurs along the measured section in the Salt Wash Member of the Morrison Formation. The fossil log-bearing interval is a light to medium greenish-gray, very fine to fine-grained, friable sandstone and siltstone with in- distinct bedding and no discernable sedimentary structures. The log is 11 m in length and is oriented east–west; view is to the east. 73 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 coaly exterior (figure 11). The logs are large, mostly in- tact and have exposed lengths that range from 0.5 to 11 m and diameters up to 1.1 m. The fossil logs have been compressed somewhat due to compaction or have been unevenly abraded so that they have a long and short di- ameter (figure 12). The logs are well preserved and can be identified to species level from thin sections made from hand samples collected from both areas. The fossil logs have been identified as conifers that pertain to the same taxon originally described as Araucarioxylon hoo- dii Tidwell et Medlyn 1993 in the family Araucariace- ae from Mt. Ellen in the Henry Mountains of southern Utah (Gee and others, 2019). Concurrent systematic work will prompt a nomenclatural transfer of this spe- cies to the genus Agathoxylon (Gee and others, 2019). DISCUSSION The fossil logs in both the Miners Draw and Rain- bow Draw areas occur in the Salt Wash Member of the Morrison Formation. The single fossil log at Miners Draw is found in a silty to very fine grained, slightly clay-rich sandstone, which is 4.3 m thick and located 17 m below the base of the Brushy Basin Member. Un- fortunately, the base of the Salt Wash Member is not exposed at the fossil log site, but the Salt Wash is 78 m thick in the section measured to the northeast. Similar- ly, we have mapped all the fossil log sites in the Rainbow Draw area to a single log-bearing interval, a very fine to fine-grained sandstone and siltstone having indistinct bedding and no discernable sedimentary features (lith- ologically like the Miners Draw interval) that is 10.8 m thick. Most fossil logs are found in the upper part of the log-bearing interval, but logs are near the base of the interval as well, indicating that the entire interval may contain logs. We did not measure the entire Salt Wash Member at Rainbow Draw, but Turner and Peterson (1999) indicated that this member in Rainbow Draw is about 80 m thick. Our measured thickness to the top of the log-bearing interval is 31.5 m, and we calculate the thickness of the remaining Salt Wash, from the top of the log-bearing interval to the base of the Brushy Basin, to be about 40 m thick. Thus, the measured and calcu- lated thickness of the Salt Wash is about 72 m, which would place the log-bearing interval just below the middle of the Salt Wash Member. Though we may be inclined to correlate the log-bearing intervals at Min- ers Draw and Rainbow Draw as the same stratigraphic horizon because the strata of all sites are lithologically very similar, the log-bearing interval at Miners Draw seems to be stratigraphically higher in the section and probably does not correlate to the interval at Rainbow Draw. The Salt Wash Member was deposited in a large flu- Figure 11. The fossil logs in both the Miners Draw and Rain- bow Draw areas are shades of light to medium brown and mostly siliceous; some have a coaly preservation. (A) Typical log in the Rainbow Draw area; view to the north. (B) Ex- ample of wood with a coaly material; note the black organic matter. 74 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 vial floodplain system of mostly meandering and braid- ed channels, migrating bar sand, and fine-grained over- bank deposits (Peterson and Roylance, 1982; Turner and Peterson, 2004; Kjemperud and others, 2008). Both high- and low-energy deposition is indicated by the range in grain sizes. Much of the fossil wood found in the Salt Wash Member occurs in channel sandstone and conglomeratic sandstone beds, but the fossil logs in the Miners Draw and Rainbow Draw areas are in an inter- val of very fine to fine-grained sandstone and siltstone beds that lack any discernable sedimentary structures. We interpret the log-bearing intervals as overbank deposits in the floodplain depositional environment. In addition, we speculate that the fossils logs may not have been transported far from their growth locations because of the fine-grained and structureless strata in which they are preserved. We are uncertain if the logs were transported by low-energy currents during a pe- riod of flooding or if the trees were toppled by a high- wind event. The concentration of fossil logs into two groups in Rainbow Draw suggests that there may have been at least two stands of conifers in this area, if not a larger forest of moderately tall trees. SUMMARY Although scraps of fossil wood are commonly found in the Morrison Formation, large fossil logs oc- cur in both the Salt Wash and Brushy Basin Members in northeastern Utah near Dinosaur National Monument. In Rainbow Draw, the fossil logs occur in the middle of the Salt Wash Member based on its measured and calculated thickness. The log-bearing interval is a very fine to fine-grained sandstone and siltstone that lacks sedimentary features, suggesting the logs are preserved in floodplain overbank deposits. The fossil log at Min- ers Draw is preserved in similar strata in the upper part of the Salt Wash Member and is thought to be depos- ited in the same depositional environment as the logs in Rainbow Draw. The log-bearing intervals at Miners Draw and Rainbow Draw seem to be at two different stratigraphic horizons and do not correlate with one another. The nature of the sediments in which they are encased suggests that the logs did not travel far from their growth locations, but we are uncertain if the fos- sil logs were transported by low-energy currents or by some other mechanism. Paleobotanical study of sam- ples collected from both sites indicate the logs pertain to conifers of the family Araucariaceae. ACKNOWLEDGMENTS We would like to thank the Utah Geological Sur- vey for their support during this project. We also thank Steve Sroka (Utah Field House of Natural History State Park Museum) for his assistance in measuring the fossil logs in Rainbow Draw. Thanks also go to the reviewers, John Foster (Museum of Moab), Grant Willis and Steph- anie Carney (both Utah Geological Survey), for their constructive comments and suggestions to improve the manuscript and figures. Finally, we are grateful to ReBecca Hunt-Foster (Utah Bureau of Land Manage- ment, Canyonlands District) for permission to collect the hand samples of fossil wood for analysis, and Lisa Baldwin (Dinosaur National Monument) for providing the internal paleontological resources report. Figure 12. The fossil logs are large and mostly intact, range in exposed length from 0.5 to 11 m, and reach diameters of as much as 1.1 m. The fossil logs have been abraded so that they have a longer and a shorter diameter. The logs are well preserved and can be identified to the species level from thin sections made from hand samples (see Gee and others, 2019) collected from the Rainbow Draw and Miners Draw areas (under permit from Bureau of Land Management). 75 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 REFERENCES Bilbey, S.A., Mickelson, D.L., Hall, E.J., Kirkland, J.I., Madsen, S.K., Blackshear, B., and Todd, C., 2005, Vertebrate ichnofos- sils from the Upper Jurassic Stump to Morrison transition— Flaming Gorge Reservoir, Utah, in Dehler, C.M., Pederson, J.L., Sprinkel, D.A., and Kowallis, B.J., editors, Uinta Moun- tain geology: Utah Geological Association Publication 33, p. 111–123. 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Peterson, L.M., and Roylance, M.M., 1982, Stratigraphy and dep- ositional history of the Upper Jurassic Morrison Formation near Capitol Reef National Park: Brigham Young University Geology Studies, v. 29, no. 2, p. 1–12. Pipiringos, G.N., and O’Sullivan, R.B., 1978, Principal unconfor- mities in Triassic and Jurassic rocks, western interior United States—a preliminary survey: U.S. Geological Survey Profes- sional Paper 1035-A, 29 p., 1 plate. Sprinkel, D.A., 2006, Interim geologic map of the Dutch John 30' x 60' quadrangle, Daggett and Uintah Counties, Utah, Moffat County, Colorado, and Sweetwater County, Wyoming: Utah Geological Survey Open-File Report 491DM, compact disc, GIS data, 3 plates, scale 1:100,000. Sprinkel, D.A., 2007, Interim geologic map of the Vernal 30' x 60' quadrangle, Uintah and Duchesne Counties, Utah, Moffat and Rio Blanco Counties, Colorado: Utah Geological Survey Open-File Report 506DM, compact disc, GIS data, 3 plates, scale 1:100,000. Sprinkel, D.A., Madsen, S.K., Kirkland, J.I., Waanders, G., and Hunt, G.J., 2012, Cedar Mountain and Dakota Formations around Dinosaur National Monument—evidence of the first incursion of the Cretaceous Western Interior Seaway into Utah: Utah Geological Survey Special Study 143, 20 p., 7 ap- pendices. Stokes, W.L., 1952, Lower Cretaceous in Colorado Plateau: Ameri- can Association of Petroleum Geologists Bulletin, v. 36, no. 9, p. 1766–1776. Stone, D.S., 1993, Tectonic evolution of the Uinta Mountains—pa- linspastic restoration of a structural cross section along lon- gitude 109o15', Utah: Utah Geological Survey Miscellaneous Publication 93-8, 19 p. Tidwell, W.D., and Medlyn, D.A., 1993, Conifer wood from the Upper Jurassic of Utah, USA-Part II—Araucarioxylon hoodii sp. nov.: The Palaeobotanist, v. 42, no. 1, p. 70–77. Turner, C.E., and Fishman, N.S., 1991, Jurassic Lake T'oo'dichi-a large alkaline, saline lake, Morrison Formation, Colorado Pla- teau: Geological Society of America Bulletin, v. 103, no. 4, p. 538–558. Turner, C.E., and Peterson, F., 1999, Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation of the Western Interi- or, U.S.A., in Gillette, D.D., editor, Vertebrate paleontology in Utah: Utah Geological Survey Miscellaneous Publication 99-1, p. 77–114. Turner, C.E., and Peterson, F., 2004, Reconstruction of Upper Ju- rassic Morrison Formation extinct ecosystem—a synthesis: Sedimentary Geology, v. 167, p. 309–355. A-1 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 APPENDIX MINERS DRAW SECTION (SOUTHWEST OFFSET) General area of the Camptosaurus Site Along the K Ranch Road along an unnamed tributary of Miners Draw, south of Blue Mountain Plateau SE1/4 SW1/4 section 3, T. 6 S., R 25 E., Uintah County, Utah Vernal 1:100,000, Snake John Reef 1:24,000 Section measured by Douglas A. Sprinkel, Mary Beth Bennis, and Dale E. Gray; October 22, 2013 N40°19.603', W109°5.350' (NAD83/WGS84, UTM 12: 662333 easting, 4465775 northing); offset southward along top of lower banded subunit (unit 17 of north section); elevation 1718 m; dip direction 328°, dip 7° DESCRIPTION THICKNESS (METERS) Interval Total BUCKHORN CONGLOMERATE MEMBER OF CEDAR MOUNTAIN FORMATION 10. conglomerate, light brownish-gray, poorly sorted, planar bedding, black chert pebbles to cobbles, massive weathering, forms a resistant cap on Morrison Formation .......................................................... NM MORRISON FORMATION BRUSHY BASIN MEMBER Upper gray part 9. Covered with abundant Buckhorn Conglomerate debris, measured to base of first conglomerate bed.............................................................................................................................................. 14.9 86.6 8. Sandstone, light-gray (unweathered) that weathers to light brownish-gray, fine-grained with coarse-grained beds, moderately well sorted, calcareous, mud rip-ups at the base of coarse- grained beds, slightly cross-bedded .................................................................................................................. 2.9 71.7 7. Claystone, mudstone, and siltstone interval, medium-gray (unweathered) and weathers light- gray, popcorn weathering, calcite veins weathering out on slope ............................................................. 52.3 68.8 Total upper gray unit ....................................................................................................................................... 70.1 Lower banded unit 6. Siltstone to silty sandstone, alternating greenish-gray and reddish-brown, contains thin resistant fine-grained sandstone, resistant sandstone 5 to 10 cm thick, unit is slope-forming, scattered manganese and carbonate nodules on slope .................................................................................. 9.0 16.5 5. Silty sandstone, light brownish-gray, very fine grained, forms slope, poorly exposed ............................. 7.5 7.5 Total lower banded unit ................................................................................................................................... 16.5 Total Brushy Basin Member ............................................................................................................................ 86.6 SALT WASH MEMBER (incomplete; base of member is covered); dip direction 190°, dip 17° 4. Sandstone, brownish-gray, coarse-grained, poorly to moderately sorted, subangular to subrounded, 1% accessory grains of orange and black, highly cross-bedded ............................................ 7.5 22.3 3. Covered ................................................................................................................................................................ 9.0 14.8 2. Silty sandstone, light greenish-gray to brownish-gray, very fine grained and slightly clay rich, no discernable sedimentary features, weakly cemented, mostly slope covered, and poorly exposed, contains large fossil log that weathers out in relief, azimuth of log direction is 255°, log is 3.0 m above the base of unit 2 ................................................................................................................. 4.3 5.8 1. Sandstone, light-gray, fine- to medium-grained, subrounded, moderately well sorted, planar cross-bedding, forms low ledge; paleocurrent measurement 220°, 130°, 170°, 230°, 240°, 220°, and 290° ................................................................................................................................................................ 1.5 1.5 Base of Salt Wash Member is covered Total Salt Wash Member (incomplete) ........................................................................................................... 22.3 A-2 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 APPENDIX MINERS DRAW CREEK SECTION (MIDDLE OFFSET) Along the K Ranch Road along an unnamed tributary of Miners Draw, south of Blue Mountain Plateau NW1/4 NE1/4 section 3, T. 6 S., R 25 E., Uintah County, Utah Vernal 1:100,000, Snake John Reef 1:24,000 Section measured by Douglas A. Sprinkel, Mary Beth Bennis, and Dale E. Gray; October 22, 2013 N 40°20.086', W109°5.034' (NAD83/WGS84, UTM 12: 662761 easting, 4466677 northing) with offset southwest along top of lower banded part (unit 17) that underlies upper gray part of Brushy Basin Member; see section and coordinates below; elevation 1755 ft; dip direction 328°, dip 7° DESCRIPTION THICKNESS (METERS) Interval Total MORRISON FORMATION BRUSHY BASIN MEMBER (incomplete) Upper gray unit 18. Claystone, mudstone, and siltstone interval, medium-gray (unweathered) and weathers light- gray, popcorn weathering, calcite veins weathering out on slope ..................................................................... NM Lower banded part 17. Siltstone, reddish-gray, interbedded thin resistant (but subdued) sandstone beds, approximately 5 to 10 cm thick ...................................................................................................................... 14.1 17.0 16. Mudstone, claystone, and silty mudstone, dark greenish-gray with alternating reddish-gray, forms slope, popcorn weathering, intervals of calcium carbonated nodules weathering out on slope, iron manganese zone............................................................................................................................... 0.3 2.9 15. Iron manganese zone ......................................................................................................................................... 0.3 2.6 14. Siltstone to silty mudstone, medium greenish-gray, slightly fissile, calcareous, forms slope .................. 2.0 2.3 13. Calcrete, calcium carbonate densely cemented with rounded coarse sand grains .................................... 0.3 0.3 Total Brushy Basin Member (lower banded unit) .......................................................................................... 17.0 SALT WASH MEMBER 12. Siltstone, greenish-gray to dark reddish-gray, mottled, slightly clayey, slightly slope-forming, pseudo popcorn weathering .............................................................................................................................. 2.6 78.3 11. Sandstone, light-gray (unweathered) and weathers medium-brown, very fine grained, subangular to subrounded, scattered dark grains, well-sorted, laminated (bedding parallel laminations), cross-bedded, calcareous, forms subdued resistant ledge..................................................... 0.7 75.7 10. Sandstone, brownish-gray (like unit 8), fine-grained, slope covered, contains a 0.8 m thick iron manganese limonitic zone that is about 2.3 m from base of unit ...................................................... 10.0 75.0 9. Sandstone, similar to unit 4, resistant and ledge-forming, scrappy wood, slopes below bare scrappy bone and wood ..................................................................................................................................... 3.6 65.0 8. Sandstone, brownish-gray, coarse-grained, moderately to poorly sorted, cross- laminated, calcareous, resistant ledge-forming .................................................................................................................. 9.4 61.4 7. Sandstone, same as unit 4, but forms slope ..................................................................................................... 4.5 52.0 6. Sandstone, brownish-gray, poorly sorted, coarse-grained, graded, fining up, cross-bedded like unit 4, resistant ledge-forming .................................................................................................................. 0.9 47.5 5. Sandstone, same as unit 4 but more slope forming ....................................................................................... 5.2 46.6 4. Sandstone, light brownish-gray, coarse-grained, poorly sorted, clasts are subangular to subrounded, graded, fining up, cross-bedded, calcareous, abundant reddish-colored chert, limestone clasts, resistant ledge-forming ........................................................................................................ 2.6 41.4 3. Sandstone, greenish-gray, very fine grained, subrounded, well-sorted, calcareous, slope- forming, more resistant in the top 0.8 m ......................................................................................................... 2.3 38.8 2. Silty sandstone, medium reddish-gray, very fine grained, subrounded, some clay, calcareous, weathers to smooth slopes ................................................................................................................................. 9.6 36.5 A-3 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 APPENDIX 1. Sandstone, light-gray, fine-grained, well-sorted, subrounded, scattered black- and orange- colored accessory grains (~1% total; dark grains are more abundant) calcareous, moderate- scale planar cross-bedding, massive weathering, ......................................................................................... 26.9 26.9 Total Salt Wash Member .................................................................................................................................. 78.3 MINERS DRAW SECTION (NORTHEAST OFFSET) — Tidwell and Windy Hill Members Along the K Ranch Road along an unnamed tributary of Miners Draw, south of Blue Mountain Plateau NW1/4 NE1/4 section 3, T. 6 S., R 25 E., Uintah County, Utah Vernal 1:100,000, Snake John Reef 1:24,000 Section measured by Douglas A. Sprinkel, Mary Beth Bennis, and Dale E. Gray; June 12, 2017 N 40°20.07342', W109°05.00.312' (NAD83/WGS84, UTM 12: 662894.01 easting, 4466657.27 northing); elevation 1755 m; dip direction 325°, dip 6° DESCRIPTION THICKNESS (METER) Interval Total MORRISON FORMATION SALT WASH MEMBER (measured in middle offset section) 12. Sandstone, light brownish-gray to very light gray, fine-grained, abundant large-scale planar and trough cross-beds, very thickly bedded ................................................................................................................. NM TIDWELL MEMBER 11. Siltstone as in unit 9; lumpy siltstone and sandstone as unit 10 but bioturbated ...................................... 0.5 0.5 10. Sandstone, light brownish-gray to light greenish-gray, fine-grained, well-sorted, parallel bedded .................................................................................................................................................................. 0.4 0.9 9. Siltstone, reddish-brown with light greenish-gray mottling, ripple laminated with some soft- sediment deformation, some mud rip-up clasts ............................................................................................. 0.6 1.5 8. Sandstone, light greenish-gray, fine-grained, lumpy, bioturbated .............................................................. 0.5 2.0 7. Sandstone as unit 6 but forms ledges; interbedded shale as in unit 5 ......................................................... 7.4 9.4 6. Sandstone, very light yellowish-brown, fine-grained, friable, forms slope ................................................ 2.0 11.4 5. Shale, dark-gray, fissile, forms slope ................................................................................................................ 1.9 13.3 4. Sandstone, light yellowish-brown, very fine grained, forms slope .............................................................. 1.4 14.7 3. Siltstone, light-gray, thinly bedded, forms slope ............................................................................................ 0.8 15.5 2. Chert, pink, botryoidal, replaced calcite or gypsum forms base of Tidwell Member ............................... 1.1 16.6 Total Tidwell Member ...................................................................................................................................... 16.6 WINDY HILL MEMBER 1. Siltstone and sandstone–interbedded; siltstone, light-gray, thin-bedded, small-scale ripples; sandstone, light-gray to light greenish-gray, fine-grained, well-sorted, abundant glauconite with some black accessory grains, thin-bedded, rippled ............................................................................. 16.1 16.1 Total Windy Hill Member ................................................................................................................................ 16.1 STUMP FORMATION (REDWATER MEMBER) Limestone, light-gray to greenish-gray, finely crystalline (sparite), sandy, glauconitic, rippled........................... NM NM = not measured Total Brushy Basin Member (south offset section) ........................................................................................ 86.6 Total Salt Wash Member (north section) ........................................................................................................ 78.3 Total Tidwell Member ...................................................................................................................................... 16.6 Total Windy Hill Member ................................................................................................................................ 16.1 TOTAL MORRISON FORMATION (COMPOSITE SECTION) .................................................................. 197.6 A-4 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 APPENDIX RAINBOW DRAW SECTION Measured west of Wagon Bench road along east side of Rainbow Draw NW1/4NW1/4 section 24, T. 3 S., R 24 E., Uintah County, Utah Dutch John 1:100,000, Island Park 1:24,000 Salt Wash Member section measured by Douglas A. Sprinkel, Mary Beth Bennis, Dale Gray, and Larry R. Edwards; October 23, 2013 N 40°33.065, W109°10.850 (NAD83/WGS84, UTM 12: 654032 easting, 4490515 northing); elevation 1707 m Tidwell and Windy Hill Members section measured by Douglas A. Sprinkel, Mary Beth Bennis, and Dale Gray; November 20, 2014 N 40°33.136, W109°10.813 (NAD83/WGS84, UTM 12: 654081 easting, 4490648 northing); elevation 1724 m; dip direction 263°, dip 5° DESCRIPTION THICKNESS (METER) Interval Total MORRISON FORMATION (INCOMPLETE) SALT WASH MEMBER (incomplete) 11. Sandstone, light-gray, medium- to coarse-grained, subangular to subrounded, moderately well sorted, approximately 30% accessory grains (equal black, orange and yellow), forms resistant ledges through slope, thick- to medium-bedded, cross-bedded ................................................ NM 10. Siltstone, light-gray to light greenish-gray becoming mostly reddish-brown at top, forms slope, channel sandstone within unit not along the line of section; channel sandstone is 9 m long and maximum 1.5 m thick, channel sandstone, light-gray, very fine to fine-grained, subrounded to subangular, well sorted, contains 5% accessory grains, mostly black with some orange ................................................................................................................................................................. 10.5 42.06 9. Sandstone and siltstone, light to medium greenish-gray, fine- to very fine grained, well- sorted, subrounded, less than 1% orange and dark accessory grains, poorly cemented, friable, forms slope, scattered fossil wood weathering out on slope; fossil log segment possibly in place along section at 8.8 m from base of unit 10 (2 m above base of unit 9 and 22.76 m above the base of the Salt Wash Member); fossil log site 1 is 1.9 m below base of unit 10 (8.9 m above base of unit 9 and 29.66 m above base of the Salt Wash Member) ............................................................ 10.8 31.56 8. Siltstone, mottled reddish-gray to greenish-gray, fine-grained, well-sorted, bedding indistinct, forms slope ........................................................................................................................................ 1.5 20.76 7. Sandstone, same as unit 4 but well cemented ............................................................................................... 0.06 19.26 6. Sandstone, medium greenish-gray, well-sorted, fine-grained, subrounded, calcareous .......................... 2.7 19.2 5. Mudstone, dark greenish-gray, silty, slightly clayey, slightly micaceous, fissile, calcareous .................... 1.3 16.5 4. Sandstone, same as Unit 1 but poorly exposed, forms slope ...................................................................... 13.7 15.2 3. Sandstone, very light gray, very fine grained, well-sorted, less than 1% dark accessory grains, calcareous, medium- to thin-bedded, tabular-bedded, small planar cross-bedding, some ripple laminations ............................................................................................................................................... 1.5 1.5 Total Salt Wash Member .................................................................................................................................. 42.06 TIDWELL MEMBER; dip direction 233°, dip 6° 2. Siltstone and sandstone (poorly exposed); siltstone light brownish-gray, forms slope; sandstone, light-gray, fine-grained, well-sorted, abundant pink botryoidal chert and sparsely glauconitic, calcareous, medium to thin bedded, tabular-bedded, small-scale cross-bedding, symmetrical ripples; forms resistant ledges .................................................................................................. 17.1 17.1 Total Tidwell Member ...................................................................................................................................... 17.1 A-5 Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA Sprinkel, D.A., Bennis, M., Gray, D.E., and Gee, C.T. Geology of the Intermountain West 2019 Volume 6 APPENDIX WINDY HILL MEMBER; dip direction 233°, dip 6° 1. Siltstone, mudstone, and limestone (calcarenite) mostly covered; siltstone and mudstone, greenish-gray, forms slope; limestone, sandy, light greenish-gray, fine-grained, well-sorted, sparsely glauconitic, calcareous, thin-bedded, tabular-bedded, small-scale cross-bedding, ripples; forms resistant ledges ......................................................................................................................... 20.4 20.4 Total Windy Hill Member ................................................................................................................................ 20.4 TOTAL MORRISON FORMATION (INCOMPLETE) .................................................................................. 79.56 REDWATER SHALE MEMBER OF STUMP FORMATION: Limestone (calcarenite), light brownish-gray to greenish-gray, fine-grained, scattered ooids to oolitic, pelecypod shell hash .................. NM NM=not measured Total Brushy Basin Member (south offset section) ........................................................................................ NM Total Salt Wash Member (incomplete) ........................................................................................................... 42.06 Total Tidwell Member ...................................................................................................................................... 17.1 Total Windy Hill Member ................................................................................................................................ 20.4 TOTAL MORRISON FORMATION (INCOMPLETE SECTION) ................................................................ 79.56