DOCSLIB.ORG

Triassic Rocks of Northeast Arizona and Adjacent Areas Robert B

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Triassic Rocks of Northeast Arizona and Adjacent Areas Robert B New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/24 Triassic rocks of northeast Arizona and adjacent areas Robert B. O'Sullivan and Morris W. Green, 1973, pp. 72-78 in: Monument Valley (Arizona, Utah and New Mexico), James, H. L.; [ed.], New Mexico Geological Society 24th Annual Fall Field Conference Guidebook, 232 p. This is one of many related papers that were included in the 1973 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks. Copyright Information Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States. No material from the NMGS website, or printed and electronic publications, may be reprinted or redistributed without NMGS permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages. TRIASSIC ROCKS OF NORTHEAST ARIZONA AND ADJACENT AREAS * by ROBERT B. O'SULLIVAN and MORRIS W. GREEN U.S. Geological Survey Denver, Colorado INTRODUCTION Arizona. In the field conference area the member has an erratic distribution (fig. 3C). The following description of Triassic rocks is based on work done by the U.S. Geological Survey on behalf of the U.S. Monitor Butte and Mesa Redondo Members Bureau of Indian Affairs in cooperation with the Navajo Tribe. Triassic rocks are extensively exposed in northeastern The Monitor Butte and Mesa Redondo members constitute Arizona (fig. 1) and consist of in ascending order, the Moen- a sequence of continental deposits of reddish-purple to gray- kopi Formation, Chinle Formation and Glen Canyon Group ish-red mudstones and siltstones intermixed with lighter (which is thought to include Jurassic rocks). In the field con- colored sandstones and conglomerates resting conformably on ference area, Triassic rocks are 1,500-2,500 feet thick (fig. the Shinarump Member. The Monitor Butte Member is further 3A), and are bounded at the base and top by regional uncon- characterized by numerous intraformational slumps, folds and formities. The unconformity at the base separates Triassic faults formed before consolidation. The Monitor Butte Member rocks from Lower Permian rocks. The unconformity at the top is as much as 350 feet thick on the Defiance Plateau; only the of the Glen Canyon is marked by chert pebbles in basal beds northern wedge edge of the Mesa Redondo is present in the of the overlying Jurassic rocks. The following description of field conference area (fig. 3C). Triassic rocks is, of necessity, brief with emphasis on new findings, but fuller information may be found in the references Petrified Forest Member cited. The Petrified Forest Member is as much as 900 feet thick along the route of the field conference. The member is com- Moenkopi Formation posed of variegated blue, gray, red, brown and purple fluviatile The Moenkopi Formation pinches out eastward (fig. 3B) in mudstone and siltstone. Montmorillonite of volcanic origin is the Four Corners area and is Triassic(?) and Early and abundant throughout the member. Over a wide area of north- Middle(?) Triassic in age. Along Comb Ridge, where U.S. 163 east Arizona, the Petrified Forest Member is split into upper crosses the outcrop, the Moenkopi is about 250 feet thick and and lower parts by the Sonsela Sandstone Bed (fig. 2 and 3C). consists of interbedded sandstone and siltstone. The reddish- brown siltstone beds are thin and evenly bedded, and the out- Owl Rock Member crops have a finely ruled appearance. The white and brown The Owl Rock Member consists mainly of pink and red sandstone beds are fine to medium-grained and contain abun- shale spotted light greenish gray. The shale is generally silty dant ripple marks. The formation is discussed in detail by and calcareous and forms slopes. Interspersed with the shale McKee (1954), Repenning, Cooley and Akers (1969), and are several ledge-forming beds of cherty limestone, sandstone Stewart, Poole and Wilson (1972b). The petrology of the and siltstone. Between Bluff and Lupton, the Owl Rock Mem- Moenkopi Formation is described by Cadigan (1971). ber ranges in thickness from 166 to 414 feet (fig. 2). Chinle Formation Reddish--orange Siltstone Member and Mule Ear Ledge Along the route of the field conference, the Chinle Forma- Along Comb Ridge, the upper part of the Chinle Formation tion consists of several members and other units of lesser rank locally includes the reddish-orange siltstone member overlain (fig. 2). The Chinle is as much as 1,200 feet thick in northeast by the Mule Ear ledge of local usage. The reddish-orange silt- Arizona and is Late Triassic in age. The fossils and nomen- stone member, composed mainly of coarse, silt-size quartz clature have recently been summarized by Breed and Breed grains, grades southward into the upper part of the Owl Rock (1972). Member (fig. 2). The Mule Ear ledge is a reddish-orange, massive, very fine grained sandstone that is commonly stained Shinarump Member with a black manganese coating. The ledge is thickest (130 feet) near its southern end. The Shinarump Member is very light gray, light tan and The reddish-orange siltstone member, together with the brown, and is composed of fluviatile, coarse-grained sandstone, Mule Ear ledge, is a southward-extending tongue of a thicker conglomerate and minor mudstone beds. The basal contact on unit that is widespread in southeast Utah, and is assigned to underlying rocks is marked by deep scours and channels as the Church Rock Member (Stewart and others, 1972a, p. 42). much as 75 feet deep. The Shinarump Member averages 80 The grain-size distribution, clay mineralogy and regional rela- feet in thickness but is as much as 200 feet thick in northeast tions show that the reddish-orange siltstone member is unlike *Publication authorized by the Director, U.S. Geological Survey. the type Church Rock Member in Arizona (O'Sullivan, 1970). 72 Hite Bed of the Church Rock Member pl. 2). Although two different names are used, there appears to be no dispute about the correlation across Laguna Creek, and The Hite Bed in the uppermost part of the Chinle (Stewart the two members are here discussed together. and others, 1972a, p. 43) is about 50 feet thick and is com- The Church Rock and Rock Point members consist of red- posed mostly of a uniformly pale-red, very fine grained cross- dish-orange and reddish-brown siltstone and very fine grained bedded sandstone. Along Comb Ridge, the Hite Bed is split sandstone that is spotted light greenish gray. Beds in the two into upper and lower parts by an intervening sequence of red- members are as much as 20 feet thick and form a series of dish-orange siltstone that represents the northward-thinning ledges and slopes. The Church Rock Member is about 250 feet wedge of the Church Rock Member (fig. 2). thick and grades northward along Comb Ridge into the Hite Unconformity at the Base of the Hite Bed Bed (fig. 2). The Rock Point Member thins southeastward from 344 feet at Little Round Rock to 100 feet at Fort An extensive unconformity is at the base of the Hite Bed Defiance. South of Fort Defiance the Rock Point Member is throughout wide areas of southeastern Utah and northernmost very poorly exposed and at a locality about 15 miles north of Arizona. At a point in Utah 8 miles south of the San Juan Lupton it appears to be absent and may have been truncated River the unconformity truncates the Mule Ear ledge and the by overlying Jurassic rocks. A line drawn through this locality, Hite Bed overlies the Owl Rock Member. From that point to roughly parallels to lines of truncation of other Glen Canyon the Utah-Arizona state line the unconformity is characterized units, shows a questionable eastern limit to the Rock Point by channels as much as 70 feet deep cut into the Owl Rock Member (fig. 3D). Member and by pebbles of chert and limestone in the base of the Hite Bed. South of the Utah-Arizona state line for 5 miles Lower Contact of Church Rock and Rock Point the unconformity rests on, or cuts into, (or through) a con- Members spicuous hackly-weathering limestone, which contains nodules of black chert. Farther south the unconformity gradually be- O'Sullivan (1970) described a conspicuous unconformity at comes less conspicuous and the contact between the hackly- the base of the Hite Bed along Comb Ridge in Utah.
Load more

Recommended publications
  • The Moenave Formation: Sedimentologic and Stratigraphic Context of the Triassic–Jurassic Boundary in the Four Corners Area, Southwestern U.S.A
    Palaeogeography, Palaeoclimatology, Palaeoecology 244 (2007) 111–125 www.elsevier.com/locate/palaeo The Moenave Formation: Sedimentologic and stratigraphic context of the Triassic–Jurassic boundary in the Four Corners area, southwestern U.S.A. ⁎ Lawrence H. Tanner a, , Spencer G. Lucas b a Department of Biology, Le Moyne College, 1419 Salt Springs Road, Syracuse, NY 13214, USA b New Mexico Museum of Natural History, 1801 Mountain Road, N.W., Albuquerque, NM 87104, USA Received 20 February 2005; accepted 20 June 2006 Abstract The Moenave Formation was deposited during latest Triassic to earliest Jurassic time in a mosaic of fluvial, lacustrine, and eolian subenvironments. Ephemeral streams that flowed north-northwest (relative to modern geographic position) deposited single- and multi-storeyed trough cross-bedded sands on an open floodplain. Sheet flow deposited mainly silt across broad interchannel flats. Perennial lakes, in which mud, silt and carbonate were deposited, formed on the terminal floodplain; these deposits experienced episodic desiccation. Winds that blew dominantly east to south-southeast formed migrating dunes and sand sheets that were covered by low-amplitude ripples. The facies distribution varies greatly across the outcrop belt. The lacustrine facies of the terminal floodplain are limited to the northern part of the study area. In a southward direction along the outcrop belt (along the Echo Cliffs and Ward Terrace in Arizona), dominantly fluvial–lacustrine and subordinate eolian facies grade mainly to eolian dune and interdune facies. This transition records the encroachment of the Wingate erg. Moenave outcrops expose a north–south lithofacies gradient from distal, (erg margin) to proximal (erg interior). The presence of ephemeral stream and lake deposits, abundant burrowing and vegetative activity, and the general lack of strongly developed aridisols or evaporites suggest a climate that was seasonally arid both before and during deposition of the Moenave and the laterally equivalent Wingate Sandstone.
    [Show full text]
  • The Origin of Comb Ridge
    THE ZEPHYR/ JUNE-JULY 2011 THE ORIGIN OF COMB RIDGE Robert Fillmore, Western State College of Colorado in Gunnison, CO (An excerpt and images from his new book: Geological Evolution of the Colorado Plateau) Comb Ridge is a lofty sinuous spine of red sandstone that stretch- ramp of Comb Ridge. Another notable result of this uplift is the es over 80 miles across northern Arizona and southeast Utah. This ensuing deep incision into the uplift by energized rivers as their monocline, as these structures are called, begins near Kayenta and runoff seeks a path to lower elevations. The deep narrow canyons snakes northward to fade away near the west flank of the Abajo of Cedar Mesa owe their existence to Monument Upwarp. Mountains. Monoclines are a peculiar component of the Colorado Plateau, with their long ridges of steeply tilted strata in a region otherwise known for its miles of flat-lying sedimentary rocks. They Monoclines are a peculiar component are hard to miss. Although not confined to the Colorado Plateau, of the Colorado Plateau, with their long ridges their concentration here is unique. Similar structures make up the of steeply tilted strata in a region San Rafael Swell, Capitol reef, and Colorado National monument otherwise known for its miles of near Grand Junction. All are closely related in origin and timing. flat-lying sedimentary rocks. They are hard to miss. The term monocline refers to a single-limbed fold; in simple geometric terms, a gargantuan ramp. The ramp of steeply tilted strata separates uplifted regions from those that have dropped The monoclines formed at the same time as the jagged Rocky downwards, relatively speaking.
    [Show full text]
  • Tetrapod Biostratigraphy and Biochronology of the Triassic–Jurassic Transition on the Southern Colorado Plateau, USA
    Palaeogeography, Palaeoclimatology, Palaeoecology 244 (2007) 242–256 www.elsevier.com/locate/palaeo Tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau, USA Spencer G. Lucas a,⁎, Lawrence H. Tanner b a New Mexico Museum of Natural History, 1801 Mountain Rd. N.W., Albuquerque, NM 87104-1375, USA b Department of Biology, Le Moyne College, 1419 Salt Springs Road, Syracuse, NY 13214, USA Received 15 March 2006; accepted 20 June 2006 Abstract Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups on the southern Colorado Plateau preserve tetrapod body fossils and footprints that are one of the world's most extensive tetrapod fossil records across the Triassic– Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point and Kayenta) that we assign to the (ascending order) Revueltian, Apachean, Wassonian and Dawan land-vertebrate faunachrons (LVF). In doing so, we redefine the Wassonian and the Dawan LVFs. The Apachean–Wassonian boundary approximates the Triassic–Jurassic boundary. This tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau confirms that crurotarsan extinction closely corresponds to the end of the Triassic, and that a dramatic increase in dinosaur diversity, abundance and body size preceded the end of the Triassic. © 2006 Elsevier B.V. All rights reserved. Keywords: Triassic–Jurassic boundary; Colorado Plateau; Chinle Group; Glen Canyon Group; Tetrapod 1. Introduction 190 Ma. On the southern Colorado Plateau, the Triassic– Jurassic transition was a time of significant changes in the The Four Corners (common boundary of Utah, composition of the terrestrial vertebrate (tetrapod) fauna.
    [Show full text]
  • 1 August 26, 2019 Sent Via E-Planning and Overnight Mail
    August 26, 2019 Sent via e-Planning and overnight mail Director (210) Attention Protest Coordinator, WO-210 P.O. Box 71383 Washington D.C. 20024-1383 Re: Protest of the Bears Ears National Monument Indian Creek and Shash Jáa Units Proposed Monument Management Plans and Final Environmental Impact Statement Please accept this protest of the Bureau of Land Management’s Bears Ears National Monument (BENM) Indian Creek and Shash Jáa Units Proposed Monument Management Plans and Final Environmental Impact Statement (MMP/FEIS), submitted by the Access Fund, Archaeology Southwest, Conservation Lands Foundation, Friends of Cedar Mesa, National Trust for Historic Preservation, Society for Vertebrate Paleontology and Utah Diné Bikéyah (Protesting Parties or Protestors). The Protesting Parties incorporate by reference the points and arguments raised in the protests filed by the Wilderness Society (and their partners), as well as by any tribes or tribally affiliated organizations. INTERESTS AND INVOLVEMENT OF THE PARTIES The Access Fund is a national advocacy organization whose mission keeps climbing areas open and conserves the climbing environment. A 501(c)(3) non-profit supporting and representing over 7 million climbers nationwide in all forms of climbing—rock climbing, ice climbing, mountaineering, and bouldering—the Access Fund is the largest US climbing organization with nearly 20,000 members and 120 affiliates. We currently hold memorandums of understanding1 with the Bureau of Land Management, National Park Service, and Forest Service to work together regarding how climbing is managed on federal land. The Access Fund provides climbing management expertise, stewardship, project specific funding, and educational outreach for climbing areas across the country including the BENM region, and Utah is one of our largest member states.
    [Show full text]
  • Utah Geology: Making Utah's Geology More Accessible. View South-East
    5/28/13 Utah Geology: Geologic Road Guides Utah Geology: Making Utah's geology more accessible. View south-east over St. George, Utah Road Guide Quick Select. Selection Map HW-160, 163 & 191 Tuba City to Kayenta, Bluff & Montecello, Utah (through Monument Valley) 0.0 Junction of U.S. Highways 160 and 89 , HW-160 Road Guide. follows U.S. Highway 160 east toward Tuba city and Kayenta. U.S. Highway 89 leads south toward the entrance to Grand Canyon National Park and Flagstaff. For a route description along U.S. Highway 89 northward from here see HW-89A Road Guide.. The road junction is in the Petrified Forest Member of the Chinle Formation. The member is composed of interbedded stream channel sandstone and varicolored shale and mudstone. This member erodes moderately easily and forms the strike valley to the north and south. From here the route of this guide leads upsection into younger and younger beds of the Chinle Formation. 0.7 Cross Hamblin Wash and rise from the Petrified Forest Member into the pinkish banded Owl Rock Member of the Chinle Formation. The upper member forms pronounced laminated pinkish gray and green badlands, distinctly unlike the rounded Painted Desert-type massive badlands of the underlying member. 1.6 Road rises up through the upper part of the Chinle Formation, a typical wavy to hummocky road. Highway construction is easy across the slope-forming parts of the formation, but holding the road after construction is difficult because the soft volcanic ash-bearing shales heave under load or after wetting and drying.
    [Show full text]
  • The First Occurrence of the Enigmatic Archosauriform Crosbysaurus Heckert 2004 from the Chinle Formation of Southern Utah Robert J
    The first occurrence of the enigmatic archosauriform Crosbysaurus Heckert 2004 from the Chinle Formation of southern Utah Robert J. Gay and Isabella St. Aude Science Department, Mission Heights Preparatory High School, Casa Grande, AZ, USA ABSTRACT Originally identified as an ornithischian dinosaur, Crosbysaurus harrisae has been found in New Mexico, Arizona, and its type locality in Texas, as well as in North Carolina. The genus has been reassessed by other workers in light of reinterpretations about the postcrania of another putative Triassic ornithischian, Revueltosaurus. The understanding of Triassic dental faunas has become more complicated by the extreme convergence between pseudosuchian archosaurs and ornithischian dinosaur dental morphologies. We report here on a new specimen of Crosbysaurus (MNA V10666) from the Chinle Formation at Comb Ridge in southeastern Utah. This new specimen is assigned to Crosbysaurus sp. on the basis of the unique compound posterior denticles, labiolingual width, and curvature. While MNA V10666 does not help resolve the aYnities of Crosbysaurus, it does represent the extension of the geographic range of this taxon for approximately 250 kilometers. This is the first record of the genus Crosbysaurus in Utah and as such it represents the northernmost known record of this taxon. This indicates that Crosbysaurus was not limited to the southern area of the Chinle/Dockum deposition but instead was widespread across the Late Triassic paleoriver systems of western Pangea. The reported specimen was found in close association with a typical Late Triassic Chinle fauna, including phytosaurs, metoposaurs, and dinosauromorphs. Submitted 13 November 2014 Accepted 31 March 2015 Subjects Paleontology Published 21 April 2015 Keywords Crosbysaurus, Chinle Formation, Chinle, Utah, Comb Ridge, New occurance, Corresponding author New record, Triassic, Late Triassic, Archosaur Robert J.
    [Show full text]
  • A New Basal Sauropodomorph Dinosaur from the Lower Jurassic Navajo Sandstone of Southern Utah
    A New Basal Sauropodomorph Dinosaur from the Lower Jurassic Navajo Sandstone of Southern Utah Joseph J. W. Sertich1*, Mark A. Loewen2 1 Department of Anatomical Sciences, Stony Brook University, Stony Brook, New York, United States of America, 2 Utah Museum of Natural History, Salt Lake City, Utah, United States of America Abstract Background: Basal sauropodomorphs, or ‘prosauropods,’ are a globally widespread paraphyletic assemblage of terrestrial herbivorous dinosaurs from the Late Triassic and Early Jurassic. In contrast to several other landmasses, the North American record of sauropodomorphs during this time interval remains sparse, limited to Early Jurassic occurrences of a single well- known taxon from eastern North America and several fragmentary specimens from western North America. Methodology/Principal Findings: On the basis of a partial skeleton, we describe here a new basal sauropodomorph dinosaur from the Lower Jurassic Navajo Sandstone of southern Utah, Seitaad ruessi gen. et sp. nov. The partially articulated skeleton of Seitaad was likely buried post-mortem in the base of a collapsed dune foreset. The new taxon is characterized by a plate-like medial process of the scapula, a prominent proximal expansion of the deltopectoral crest of the humerus, a strongly inclined distal articular surface of the radius, and a proximally and laterally hypertrophied proximal metacarpal I. Conclusions/Significance: Phylogenetic analysis recovers Seitaad as a derived basal sauropodomorph closely related to plateosaurid or massospondylid ‘prosauropods’ and its presence in western North America is not unexpected for a member of this highly cosmopolitan clade. This occurrence represents one of the most complete vertebrate body fossil specimens yet recovered from the Navajo Sandstone and one of the few basal sauropodomorph taxa currently known from North America.
    [Show full text]
  • A Procolophonid (Parareptilia) from the Owl Rock Member, Chinle Formation of Utah, Usa
    Palaeontologia Electronica http://palaeo-electronica.org A PROCOLOPHONID (PARAREPTILIA) FROM THE OWL ROCK MEMBER, CHINLE FORMATION OF UTAH, USA Nicholas C. Fraser, Randall B. Irmis*, and David K. Elliott ABSTRACT An isolated skull of a procolophonid is described from the Owl Rock Member of the Chinle Formation in the Abajo Mountains of southeast Utah. Although poorly pre- served, this specimen exhibits features that demonstrate a phylogenetic relationship with leptopleuronine procolophonids. These include the dentition, the greatly expanded orbitotemporal opening, the prominent quadratojugal spikes, and the shape of the jugal. Nicholas C. Fraser. Virginia Museum of Natural History, Martinsville, Virginia 24112, USA. [email protected] Randall B. Irmis. Department of Geology, Northern Arizona University, Flagstaff, Arizona 86011, USA. *Current Address: University of California Museum of Paleontology, 1101 Valley Life Sciences Building, Berkeley, California 94720-4780. [email protected] David K. Elliott. Department of Geology, Northern Arizona University, Flagstaff, Arizona 86011, USA. [email protected] KEY WORDS: Procolophonidae; Parareptilia; Late Triassic; Chinle Formation PE Article Number: 8.1.13 Copyright: Society of Vertebrate Paleontology. May 2005 Submission: 28 June 2004. Acceptance: 6 March 2005. INTRODUCTION skull has been described in detail (Kemp 1974; Carroll and Lindsay 1985). The first member of the The Procolophonidae are a group of small clade to be named was Leptopleuron from the parareptiles (sensu Laurin and Reisz
    [Show full text]
  • Raplee Ridge Monocline and Thrust Fault Imaged Using Inverse Boundary Element Modeling and ALSM Data
    Journal of Structural Geology 32 (2010) 45–58 Contents lists available at ScienceDirect Journal of Structural Geology journal homepage: www.elsevier.com/locate/jsg Structural geometry of Raplee Ridge monocline and thrust fault imaged using inverse Boundary Element Modeling and ALSM data G.E. Hilley*, I. Mynatt, D.D. Pollard Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA article info abstract Article history: We model the Raplee Ridge monocline in southwest Utah, where Airborne Laser Swath Mapping (ALSM) Received 16 September 2008 topographic data define the geometry of exposed marker layers within this fold. The spatial extent of five Received in revised form surfaces were mapped using the ALSM data, elevations were extracted from the topography, and points 30 April 2009 on these surfaces were used to infer the underlying fault geometry and remote strain conditions. First, Accepted 29 June 2009 we compare elevations extracted from the ALSM data to the publicly available National Elevation Dataset Available online 8 July 2009 10-m DEM (Digital Elevation Model; NED-10) and 30-m DEM (NED-30). While the spatial resolution of the NED datasets was too coarse to locate the surfaces accurately, the elevations extracted at points Keywords: w Monocline spaced 50 m apart from each mapped surface yield similar values to the ALSM data. Next, we used Boundary element model a Boundary Element Model (BEM) to infer the geometry of the underlying fault and the remote strain Airborne laser swath mapping tensor that is most consistent with the deformation recorded by strata exposed within the fold.
    [Show full text]
  • Earliest Jurassic U-Pb Ages from Carbonate Deposits in the Navajo Sandstone, Southeastern Utah, USA Judith Totman Parrish1*, E
    https://doi.org/10.1130/G46338.1 Manuscript received 3 April 2019 Revised manuscript received 10 July 2019 Manuscript accepted 11 August 2019 © 2019 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 4 September 2019 Earliest Jurassic U-Pb ages from carbonate deposits in the Navajo Sandstone, southeastern Utah, USA Judith Totman Parrish1*, E. Troy Rasbury2, Marjorie A. Chan3 and Stephen T. Hasiotis4 1 Department of Geological Sciences, University of Idaho, P.O. Box 443022, Moscow, Idaho 83844, USA 2 Department of Geosciences, Stony Brook University, Stony Brook, New York 11794, USA 3 Department of Geology and Geophysics, University of Utah, 115 S 1460 E, Room 383, Salt Lake City, Utah 84112-0102, USA 4 Department of Geology, University of Kansas, 115 Lindley Hall, 1475 Jayhawk Boulevard, Lawrence, Kansas 66045-7594, USA ABSTRACT with the lower part of the Navajo Sandstone New uranium-lead (U-Pb) analyses of carbonate deposits in the Navajo Sandstone in across a broad region from southwestern Utah southeastern Utah (USA) yielded dates of 200.5 ± 1.5 Ma (earliest Jurassic, Hettangian Age) to northeastern Arizona (Blakey, 1989; Hassan and 195.0 ± 7.7 Ma (Early Jurassic, Sinemurian Age). These radioisotopic ages—the first re- et al., 2018). The Glen Canyon Group is under- ported from the Navajo erg and the oldest ages reported for this formation—are critical for lain by the Upper Triassic Chinle Formation, understanding Colorado Plateau stratigraphy because they demonstrate that initial Navajo which includes the Black Ledge sandstone (e.g., Sandstone deposition began just after the Triassic and that the base of the unit is strongly Blakey, 2008; Fig.
    [Show full text]
  • An Unusual Archosauromorph Archosauriform Tooth Increases
    An unusual archosauromorph archosauriform tooth increases known tetrapod diversity in the lower portion of the Chinle Formation (Late Triassic) of southeastern Utah, USA Lopez, Andres; St. Aude, Isabella; Alderete, David; Alvarez, David; Aultman, Hannah; Busch, Dominique; Bustamante, Rogelio; Cirks, Leah; Lopez, Martin; Moncada, Adriana; Ortega, Elizabeth; Verdugo, Carlos; Gay, Robert J *. Mission Heights Preparatory High School, 1376 E. Cottonwood Ln., Casa Grande, Arizona 85122 *[email protected] 520-836-9383 Abstract: An unusual tetrapod tooth was discovered in the Late Upper Triassic Chinle Formation of southeastern Utah. The tooth was originally thought hypothesized to belong pertain to Revueltosaurus, but further investigations have rejected that hypothesis. In this paper, we Comment [Anon1]: This is unnecessary unless it was published somewhere else? compare MNA V10668 to other known fossil teeth tooth crowns found infrom the Chinle Formation and identify assign the tooth to the least inclusive clade it may belongs tocurrently available, Archosauriformes, based on the presence of mesial and distal serrations, a distal keel, and a conical mesiodistal profile. Using data found in other publications and pictures of other teeth, we compare this specimen to other Triassic dental taxa. MNA V10668 shares some similarities with Crosbysaurus, Tecovasaurus, and several other named taxa, including a teardrop-shaped labiolingual profile, but possesses a unique combination of characteristics not found in other diapsid archosauromorph teeth. We conclude that it is most likely an archosauromorph and probably an archosauriform. This increases the known diversity of tetrapods archosauromorphs from the Chinle Formation and represents the first tooth of this morphotype completely unique toto be found from Utah in the Late Triassic Period.
    [Show full text]
  • Canyon Country
    CANYONLANDS TRAVEL REGION ANYONANYON OUNTRYOUNTRY CCA Land Of EnchantmentCC his vast rock desert in southeastern Utah showcases deep, colorful T canyons, majestic natural monuments pictured in western movies, a fantasy land of towering pinnacles and slot canyons, rock arches and ANYONANYON OUNTRYOUNTRY bridges, and breathtaking vistas atop mesas. Much can be seen by car, and more of this endlessly intriguing country is accessible by foot, mountain Explanation CC CC bike, four-wheel-drive vehicle, or watercraft. Collapsed salt anticline You do not have to be a geologist to enjoy or interpret the scenery, for the Arches rocks easily divulge their stories of forming in seas or on land, in deserts or in deltas, in rivers or along beaches. What a fascinating heritage: dinosaurs Bridges once sauntered through lush lowlands leaving huge footprints in mud that Petroglyphs has now turned to rock, vast sand dunes that drifted across the area are Dinosaur tracks preserved as large sweeping lines in sandstone walls, and oceans that once Indian ruins covered this region left fossilized corals and seashells embedded in lime- Paradox basin salt boundary stone. Parks, monuments, recreation areas This guide introduces you to the rocks’ stories, to enhance your travels and Indian reservations your appreciation of the region. Along designated scenic byways, which are portrayed at the end of this pamphlet, look for the specific features Scenic byways described here and learn what their journey has been as you make yours. During your visit, tread lightly on this delicate land so that the pristine and 0 10 20 miles unique landscape remains unchanged.
    [Show full text]