DOCSLIB.ORG

U-Pb Zircon Geochronology and Depositional

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
U-Pb Zircon Geochronology and Depositional U-Pb zircon geochronology and depositional age models for the Upper Triassic Chinle Formation (Petrified Forest National Park, Arizona, USA): Implications for Late Triassic paleoecological and paleoenvironmental change Cornelia Rasmussen1,2,3,†, Roland Mundil4, Randall B. Irmis1,2, Dominique Geisler5, George E. Gehrels5, Paul E. Olsen6, Dennis V. Kent6,7, Christopher Lepre6,7, Sean T. Kinney6, John W. Geissman8,9, and William G. Parker10 1 Department of Geology & Geophysics, University of Utah, Salt Lake City, Utah 84112-0102, USA 2 Natural History Museum of Utah, University of Utah, Salt Lake City, Utah 84108-1214, USA 3 Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758, USA 4 Berkeley Geochronology Center, Berkeley, California 94709, USA 5 Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA 6 Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA 7 Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey 08854, USA 8 Department of Geosciences, University of Texas at Dallas, Richardson, Texas 75080, USA 9 Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, 87131-0001, USA 10Division of Science and Resource Management, Petrified Forest National Park, Petrified Forest, Arizona 86028, USA ABSTRACT zircon ages and magnetostratigraphy. (<1 Ma difference) the true time of depo- From 13 horizons of volcanic detritus-rich sition throughout the Sonsela Member. The Upper Triassic Chinle Formation siltstone and sandstone, we screened up to This model suggests a significant decrease is a critical non-marine archive of low- ∼300 zircon crystals per sample using laser in average sediment accumulation rate in paleolatitude biotic and environmental ablation–inductively coupled plasma–mass the mid-Sonsela Member. Hence, the biotic change in southwestern North America. spectrometry and subsequently analyzed turnover preserved in the mid-Sonsela The well-studied and highly fossiliferous up to 19 crystals of the youngest age popu- Member at PFNP is also middle Norian Chinle strata at Petrified Forest National lation using the chemical abrasion–isotope in age, but may, at least partially, be an Park (PFNP), Arizona, preserve a biotic dilution–thermal ionization mass (CA-ID- artifact of a condensed section. Model 2 turnover event recorded by vertebrate and TIMS) spectrometry method. These data following the magnetostratigraphic-based palynomorph fossils, which has been alter- provide new maximum depositional ages age model for the CPCP core 1A suggests natively hypothesized to coincide with tec- for the top of the Moenkopi Formation instead that the ages from the lower and tonically driven climate change or with the (ca. 241 Ma), the lower Blue Mesa Mem- middle Sonsela Member are inherited pop- Manicouagan impact event at ca. 215.5 Ma. ber (ca. 222 Ma), and the lower (ca. 218 to ulations of zircon crystals that are 1–3 Ma Previous outcrop-based geochronologic age 217 Ma) and upper (ca. 213.5 Ma) Sonsela older than the true depositional age of the constraints are difficult to put in an accu- Member. The maximum depositional ages strata. This results in a model in which no rate stratigraphic framework because lat- obtained for the upper Chinle Formation sudden decrease in sediment accumulation eral facies changes and discontinuous out- fall well within previously proposed age rate is necessary and implies that the base crops allow for multiple interpretations. A constraints, whereas the maximum depo- of the Sonsela Member is no older than ca. major goal of the Colorado Plateau Coring sitional ages for the lower Chinle Forma- 216 Ma. Independent of these alternatives, Project (CPCP) was to retrieve a continu- tion are relatively younger than previously both age models agree that none of the pre- ous record in unambiguous superposition proposed ages from outcrop; however, served Chinle Formation in PFNP is Car- designed to remedy this situation. We sam- core to outcrop stratigraphic correlations nian (>227 Ma) in age, and hence the biotic pled the 520-m-long core 1A of the CPCP to remain uncertain. By correlating our new turnover event cannot be correlated to the develop an accurate age model in unques- ages with the magnetostratigraphy of the Carnian–Norian boundary but is rather a tionable superposition by combining U-Pb core, two feasible age model solutions can mid-Norian event. Our age models demon- be proposed. Model 1 assumes that the strate the powers, but also the challenges, youngest, coherent U-Pb age clusters of of integrating detrital CA-ID-TIMS ages Cornelia Rasmussen http://orcid.org/0000- 0001-9979-8224 each sample are representative of the maxi- with magnetostratigraphic data to properly †[email protected]. mum depositional ages and are close to interpret complex sedimentary sequences. GSA Bulletin; Month/Month 2020; 0; p. 1–20; https://doi.org/10.1130/B35485.1; 5 figures; 1 table; 1 supplemental file. For permission to copy, contact [email protected] 1 © 2020 Geological Society of America Downloaded from https://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/doi/10.1130/B35485.1/5095463/b35485.pdf by Rutgers University Libraries user on 20 July 2020 Rasmussen et al. INTRODUCTION lithostratigraphic correlations even over short events. For example, a biotic turnover in paly- distances (e.g., Parker and Martz, 2010; Irmis nomorph (Reichgelt et al., 2013; Baranyi et al., The Triassic Period represents a critical time et al., 2011; Ramezani et al., 2011; Atchley et al., 2018) and vertebrate taxa (Parker and Martz, in Earth history that experienced major envi- 2013). Exemplifying these difficulties, some 2010) occurs in outcrop in the middle Sonsela ronmental changes, and is embedded between precise U-Pb ages are available for the intensely Member between 213.1 Ma and 218.0 Ma, two mass extinction events (e.g., Payne et al., studied Upper Triassic Chinle Formation and based on outcrop correlation of dated horizons 2004; Mundil et al., 2004; Irmis and Whiteside, its equivalents in western North America (Irmis in Ramezani et al. (2011) and the biostrati- 2010; Preto et al., 2010; Schoene et al., 2010). et al., 2011; Ramezani et al., 2011, 2014; Atch- graphic record (e.g., Parker and Martz, 2010). Key Triassic Earth system events include the ley et al., 2013), yet these outcrop samples are Three main hypotheses have been suggested as onset of the break up and northward drift of spread over hundreds of square kilometers, so the potential cause for the biotic turnover: (1) the supercontinent Pangea (Dietz and Holden, placing them into a single unambiguous superpo- increasing aridification driven by either north- 1970; Robinson, 1973; Olsen, 1997; Olsen and sition remains difficult despite excellent outcrop. ward drift of Pangaea or tectonic changes along Kent, 2000), frequent carbon cycle excursions, To date, the only comprehensive timescale for the western margin of the North American Cor- and major changes in pCO2 levels (e.g., Payne the Late Triassic has been the Newark– Hart- dillera (Atchley et al., 2013; Lindström et al., et al., 2004; Berner, 2006; Whiteside et al., 2010; ford Astrochronostratigraphic Polarity Time 2016); (2) ecosystem disruption caused by Hönisch et al., 2012; Schaller et al., 2015; Foster Scale (N–H APTS) (Kent et al., 2017), which the relatively large (crater diameter ∼100 km) et al., 2017). During the Late Triassic, sudden is calibrated by orbitally paced lacustrine cycles Manicouagan impact event in Quebec, Canada paleoenvironmental events include reoccurring but has direct geochronologic control for only (e.g., Grieve, 2006) at ca. 215.5 Ma (Ramezani flood basalt volcanism such as the Wrangellia a ∼600 k.y. window around the Triassic–Juras- et al., 2005) (Mundil and Irmis, 2008; Olsen Large Igneous Province (Greene et al., 2010, and sic boundary (Blackburn et al., 2013). Though et al., 2010; Parker and Martz, 2010); and (3) references within) and the Central Atlantic Mag- the Astrochronostratigraphic Polarity Time partially an artifact of the stratigraphic record matic Province (Whiteside et al., 2010; Schoene Scale (N–H APTS) has been incorporated into (for example due to one or more hiatuses), mak- et al., 2010; Blackburn et al., 2013), as well as at various time scale compilations (e.g., Ogg, 2012; ing a gradual biotic turnover appear sudden and least three hypervelocity impact events, the larg- Walker et al., 2018), until very recently (Kent coordinated due to a condensed section (Heck- est of which is the Manicouagan impact struc- et al., 2018; Olsen et al., 2019) there has been ert and Lucas, 1996). Similarly, although recent ture in Canada (Ramezani et al., 2005; Grieve, no direct tests of its validity. geochronology suggests the fossil-bearing levels 2006; Schmieder et al., 2010, 2014; Cohen The Chinle Formation exposed at Petrified of the Chinle Formation are wholly Norian in et al., 2017). At the same time, the Late Triassic Forest National Park (PFNP) in northern Ari- age (Irmis et al., 2011; Ramezani et al., 2011, witnessed a number of important evolutionary zona, USA, represents an ideal study area to 2014), some authors maintain that the lower events, such as the origin and early diversifica- resolve these issues for two reasons: first, the sed- Chinle is Carnian in age (e.g., Lucas and Tan- tion of dinosaurs, lizards, mammaliaforms, and imentary strata contain a vast amount of volcanic ner, 2018)
Load more

Recommended publications
  • X-Ray Computed Tomographic Reconstruction and Bone
    X-RAY COMPUTED TOMOGRAPHIC RECONSTRUCTION AND BONE HISTOLOGY OF THE AETOSAUR COAHOMASUCHUS CHATHAMENSIS (ARCHOSAURIA: STAGONOLEPIDIDAE) FROM THE UPPER TRIASSIC PEKIN FORMATION, DEEP RIVER BASIN, NORTH CAROLINA AND A RE-ANALYSIS OF ITS PHYLOGENETIC RELATIONSHIPS by Devin Kane Fodor Hoffman Honors Thesis Appalachian State University Submitted to the Department of Geology and The Honors College in partial fulfillment of the requirements for the degree of Bachelor of Science May, 2017 Approved by: ______________________________________________________ Andrew B. Heckert, Ph.D., Thesis Director ______________________________________________________ Michael S. Osbourn, Ph.D., Second Reader ______________________________________________________ Gabriele M. Casale, Ph.D., Departmental Honors Director ______________________________________________________ Ted Zerucha, Ph.D., Interim Director, The Honors College 2 ABSTRACT Aetosauria is a clade of heavily armored, quadrupedal archosaurian omnivores to herbivores known from Upper Triassic units from across what was the supercontinent of Pangea. Their relative abundance in many deposits, as well as the sparsity of other Triassic herbivores, indicates they were key components of Late Triassic ecosystems. However, there remains debate about the relationships within the clade, the structure of their internal skeletal anatomy, and their patterns of growth. To contribute answers to these questions I reexamined and reanalyzed a recently described species of Coahomasuchus from the Sanford sub-basin of North Carolina, C. chathamensis. My phylogenetic analysis, with updated character scorings for Coahomasuchus and several other aetosaurs, recovers Coahomasuchus in a polytomy with Aetosaurus and the Typothoracinae, in contrast with a recent analysis that recovered Coahomasuchus as highly labile. In an attempt to better understand the interior skeleton of an aetosaur, I undertook the first CT reconstruction of the skeleton under the armor of an articulated specimen.
    [Show full text]
  • (GIS) Study of Triassic Vertebrate Biochronology
    Geol. Mag. 142 (4), 2005, pp. 327–354. c 2005 Cambridge University Press 327 doi:10.1017/S001675680500083X Printed in the United Kingdom A Geographical Information System (GIS) study of Triassic vertebrate biochronology ∗ E. J. RAYFIELD ,P.M.BARRETT†,R.A.MCDONNELL‡ & K. J. WILLIS‡ ∗Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK †Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK ‡School of Geography and the Environment, University of Oxford, Mansfield Road, Oxford OX1 3TB, UK (Received 17 June 2004; accepted 10 February 2005) Abstract – Geographical Information Systems (GIS) have been applied extensively to analyse spatial data relating to varied environmental issues, but have not so far been used to address biostratigraphical or macroevolutionary questions over extended spatial and temporal scales. Here, we use GIS techniques to test the stability, validity and utility of proposed Middle and Late Triassic ‘Land Vertebrate Faunachrons’ (LVFs), a global biostratigraphical framework based upon terrestrial/freshwater tetrapod occurrences. A database of tetrapod and megafloral localities was constructed for North America and Western Europe that also incorporated information on relevant palaeoenvironmental variables. This database was subjected to various spatial analysis techniques. Our GIS analysis found support at a global level for Eocyclotosaurus as an Anisian index taxon and probably Aetosaurus as a Norian indicator. Other tetrapod taxa are useful biostratigraphical/biochronological markers on a regional basis, such as Longosuchus and Doswellia for Late Carnian time. Other potential index fossils are hampered, however, by taxonomic instability (Mastodonsaurus, Metoposaurus, Typothorax, Paleorhinus, Pseudopalatus, Redondasaurus, Redondasuchus) and/or are not clearly restricted in temporal distribution (Paleorhinus, Angistorhinus, Stagonolepis, Metoposaurus and Rutiodon).
    [Show full text]
  • Early Crocodylomorph Increases Top Tier Predator Diversity During Rise Of
    OPEN Early crocodylomorph increases top tier SUBJECT AREAS: predator diversity during rise of PHYLOGENETICS PALAEONTOLOGY dinosaurs Lindsay E. Zanno1,2*, Susan Drymala1,2*, Sterling J. Nesbitt3 & Vincent P. Schneider1 Received 28 October 2014 1Research & Collections, North Carolina Museum of Natural Sciences, Raleigh, NC 27601, USA, 2Department of Biological Accepted Sciences, North Carolina State University, Raleigh, NC 27607, USA, 3Department of Geosciences, Virginia Polytechnic Institute 16 February 2015 and State University, Blacksburg, VA 24061, USA. Published 19 March 2015 Triassic predatory guild evolution reflects a period of ecological flux spurred by the catastrophic end-Permian mass extinction and terminating with the global ecological dominance of dinosaurs in the early Jurassic. In responding to this dynamic ecospace, terrestrial predator diversity attained new levels, prompting unique trophic webs with a seeming overabundance of carnivorous taxa and the evolution of Correspondence and entirely new predatory clades. Key among these was Crocodylomorpha, the largest living reptiles and only requests for materials one of two archosaurian lineages that survive to the present day. In contrast to their existing role as top, should be addressed to semi-aquatic predators, the earliest crocodylomorphs were generally small-bodied, terrestrial faunivores, L.E.Z. (lindsay.zanno@ occupying subsidiary (meso) predator roles. Here we describe Carnufex carolinensis a new, unexpectedly large-bodied taxon with a slender and ornamented skull from the Carnian Pekin Formation (,231 Ma), naturalsciences.org) representing one of the oldest and earliest diverging crocodylomorphs described to date. Carnufex bridges a problematic gap in the early evolution of pseudosuchians by spanning key transitions in bauplan evolution and body mass near the origin of Crocodylomorpha.
    [Show full text]
  • From the Upper Triassic Dockum Group of Howard County, Texas, with Revisions to the Genera Lasalichthys and Synorichthys
    Journal of Vertebrate Paleontology ISSN: 0272-4634 (Print) 1937-2809 (Online) Journal homepage: http://www.tandfonline.com/loi/ujvp20 A new species of Lasalichthys (Actinopterygii, Redfieldiiformes) from the Upper Triassic Dockum Group of Howard County, Texas, with revisions to the genera Lasalichthys and Synorichthys Sarah Z. Gibson To cite this article: Sarah Z. Gibson (2018): A new species of Lasalichthys (Actinopterygii, Redfieldiiformes) from the Upper Triassic Dockum Group of Howard County, Texas, with revisions to the genera Lasalichthys and Synorichthys, Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2018.1513009 To link to this article: https://doi.org/10.1080/02724634.2018.1513009 Published online: 29 Nov 2018. Submit your article to this journal View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ujvp20 Journal of Vertebrate Paleontology e1513009 (17 pages) # by the Society of Vertebrate Paleontology DOI: 10.1080/02724634.2018.1513009 ARTICLE A NEW SPECIES OF LASALICHTHYS (ACTINOPTERYGII, REDFIELDIIFORMES) FROM THE UPPER TRIASSIC DOCKUM GROUP OF HOWARD COUNTY, TEXAS, WITH REVISIONS TO THE GENERA LASALICHTHYS AND SYNORICHTHYS SARAH Z. GIBSON Department of Geology and Biodiversity Institute, University of Kansas, Lawrence, Kansas 66045, U.S.A., [email protected] ABSTRACT—A new species of redfieldiiform fishes, Lasalichthys otischalkensis, sp. nov., is described based on new, three- dimensionally preserved specimens from the Upper Triassic Dockum Group of Howard County, western Texas. Lasalichthys otischalkensis is diagnosed by a combination of unique traits found in the skull, including shape of maxilla, shape of preopercu- lum and associated cheek bones, pattern and articulation of bones in the snout, and patterns of sensory line canals in the der- mal skull bones.
    [Show full text]
  • The Origin and Early Radiation of Dinosaurs
    Earth-Science Reviews 101 (2010) 68–100 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev The origin and early radiation of dinosaurs Stephen L. Brusatte a,b,⁎, Sterling J. Nesbitt a,b,c, Randall B. Irmis d, Richard J. Butler e, Michael J. Benton f, Mark A. Norell a,b a Division of Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA b Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA c Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, USA d Utah Museum of Natural History and Department of Geology & Geophysics, University of Utah, Salt Lake City, UT 84112, USA e Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Str. 10, 80333 Munich, Germany f Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK article info abstract Article history: Dinosaurs were remarkably successful during the Mesozoic and one subgroup, birds, remain an important Received 1 May 2009 component of modern ecosystems. Although the extinction of non-avian dinosaurs at the end of the Accepted 20 April 2010 Cretaceous has been the subject of intense debate, comparatively little attention has been given to the origin Available online 4 May 2010 and early evolution of dinosaurs during the Late Triassic and Early Jurassic, one of the most important evolutionary radiations in earth history. Our understanding of this keystone event has dramatically changed Keywords: over the past 25 years, thanks to an influx of new fossil discoveries, reinterpretations of long-ignored dinosaurs diversification specimens, and quantitative macroevolutionary analyses that synthesize anatomical and geological data.
    [Show full text]
  • Diverse New Microvertebrate Assemblage from the Upper Triassic Cumnock Formation, Sanford Subbasin, North Carolina, Usa
    Journal of Paleontology, 86(2), 2012, p. 368–390 Copyright ’ 2012, The Paleontological Society 0022-3360/12/0086-0368$03.00 DIVERSE NEW MICROVERTEBRATE ASSEMBLAGE FROM THE UPPER TRIASSIC CUMNOCK FORMATION, SANFORD SUBBASIN, NORTH CAROLINA, USA ANDREW B. HECKERT,1 JONATHAN S. MITCHELL,1,2 VINCENT P. SCHNEIDER,3 AND PAUL E. OLSEN4 1Department of Geology, Appalachian State University, ASU Box 32067, Boone, NC 28608-2067, USA, [email protected] ; 2Committee on Evolutionary Biology, University of Chicago, 1025 E 57th St, Chicago, IL 60637, USA, [email protected] ; 3North Carolina Museum of Natural Sciences, 11 West Jones Street, Raleigh, NC 27601-1079, USA, [email protected] ; and 4Lamont Doherty Earth Observatory, 61 Rt. 9W Palisades, NY 10964-1000, USA, [email protected] ABSTRACT—The Moncure microvertebrate locality in the Cumnock Formation, Sanford sub-basin, North Carolina, dramatically increases the known Late Triassic age vertebrate assemblage from the Deep River Basin. The ,50,000 recovered microvertebrate fossils include osteichthyans, amphibians, and numerous lepidosauromorph, archosauri- form, and synapsid amniotes. Actinopterygian fossils consist of thousands of scales, teeth, skull, and lower jaw fragments, principally of redfieldiids and semionotids. Non-tetrapod sarcopterygians include the dipnoan Arganodus sp., the first record of lungfish in the Newark Supergroup. Temnospondyls are comparatively rare but the preserved centra, teeth, and skull fragments probably represent small (juvenile) metoposaurids. Two fragmentary teeth are assigned to the unusual reptile Colognathus obscurus (Case). Poorly preserved but intriguing records include acrodont and pleurodont jaw fragments tentatively assigned to lepidosaurs. Among the archosauriform teeth is a taxon distinct from R. callenderi that we assign to Revueltosaurus olseni new combination, a morphotype best assigned to cf.
    [Show full text]
  • Pekin Formation, Deep River Basin, North Carolina, Usa)
    SOUTHEASTERN GEOLOGY V. 38, No. 2, December 1998. p. 77-90 THE OLDEST LATE TRIASSIC FOOTPRINT ASSEMBLAGE FROM NORTH AMERICA (PEKIN FORMATION, DEEP RIVER BASIN, NORTH CAROLINA, USA) PAUL E. OLSEN Lamont-Doherty Earth Observatory of Columbia University Rt. 9 W, Palisades, NY 10964 PHILLIP HUBER Virginia Museum of Natural History 1001 Douglas Avenue, Martinsville, Virginia 24112 ABSTRACT INTRODUCTION An assemblage of reptile footprints from Footprints comprise by far the most common the abandoned Pomona Terra-cotta and the evidence of tetrapods in the Newark Super­ active Boren quarries in the middle Pekin group of eastern North America. They have Formation of the Sanford subbasin of the been the subject of fairly continuous research Deep River basin is the oldest track faunule since the first dinosaur footprint was described recognized to date in strata of Late Triassic by Edward Hitchcock in 1836 (Hitchcock, age in Eastern North America. The most com­ 1836; Olsen and others, 1997), and they provide mon taxon is a possibly new genus of penta­ a rich source of biostratigraphic, paleoecologi­ dactyl ichnite similar to, but distinct from, cal, behavioral, and physiological information Brachychirotherium. It may lack manus im­ (e.g., Olsen and Gatton, 1977; Olsen, 1988; pressions, has a strong tendency to be func­ Lockley, 1991; Farlow, 1981; Farlow and Chap­ tionally tridactyl, and has an extremely man, 1997). Despite the over 160 years of study shallow digit V impression. At least one track devoted to Newark Supergroup tetrapod foot­ is over 30 cm in length. Also present is the prints, the assemblages from the Early Jurassic quadrupedal, probably phytosaurian ichnite age strata have received most of the attention, Apatopus lineatus, based on a trackway, and with antecedent 30 million years of Newark several small ( <15 cm) bipedal and tridactyl track assemblages receiving relatively short forms that are probably dinosaurian.
    [Show full text]
  • STRATIGRAPHY of the UPPER TRIASSIC CHINLE Group, FOUR CORNERS REGION
    New Mexico Geological Society Guidebook, 48th Field Conference, Mesozoic Geology and Paleontology of the Four Corners Region, 1997 81 STRATIGRAPHY OF THE UPPER TRIASSIC CHINLE GROUp, FOUR CORNERS REGION 2 SPENCER G. LUCASl, ANDREW B. HECKERT , JOHN W. ESTEpl, and ORIN J. ANDERSON3 I New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, NM 87104; 2 Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131; 3 New Mexico Bureau of Mines and Mineral Resources, Socorro, NM 87801 Abstract-Upper Triassic strata exposed in the Four Corners region belong to the Chinle Group of late Carnian-Rhaetian age. Chinle Group strata can be divided into eight lithostratigraphic intervals: (1) mottled stratalTemple Mountain Formation-as much as 31 m of mostly color mottled, deeply pedoturbated siltstone, sandstone and conglomerate; (2) Shinarump Formation-up to 76 m of trough-crossbedded sandstone and siliceous extrabasinal conglomerate; (3) Monitor Butte/Cameron/Bluewater Creek Forma­ tions-up to 84 m of varied lithofacies ranging from green bentonitic mudstones (Monitor Butte) to sandstones (Cameron) to red-bed mudstones (Bluewater Creek); (4) Blue Mesa Member of Petrified Forest Formation-up to 100 m of blue, gray, purple and red variegated bentonitic mudstone; (5) Moss Back Formation/Sonsela Member of Petrified Forest Formation-up to 50 m of trough-cross bedded sandstone and intrabasinal conglomerate; (6) Painted Desert Member of Petrified Forest Formation-up to 150 m of mostly red-bed bentonitic mudstone and siltstone; (7) Owl Rock Formation-up to 150 m of pale red and orange siltstone interbedded with ledges of pedogenic calcrete limestone; (8) Rock Point Formation-up to 300 m of reddish brown, cyclically-bedded sandstone and non-bentonitic siltstone.
    [Show full text]
  • X-Ray Computed Tomographic Reconstruction of The
    Under the armor: X-ray computed tomographic reconstruction of the internal skeleton of Coahomasuchus chathamensis (Archosauria: Aetosauria) from the Upper Triassic of North Carolina, USA, and a phylogenetic analysis of Aetosauria Devin K. Hoffman1, Andrew B. Heckert2 and Lindsay E. Zanno3,4 1 Department of Geosciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, United States of America 2 Department of Geological and Environmental Sciences, Appalachian State University, Boone, NC, United States of America 3 Department of Biological Sciences, North Carolina State University, Raleigh, NC, United States of America 4 Division of Paleontology, North Carolina Museum of Natural Sciences, Raleigh, NC, United States of America ABSTRACT Aetosauria is a clade of heavily armored, quadrupedal omnivorous to herbivorous archosaurs known from the Late Triassic across what was the supercontinent of Pangea. Their abundance in many deposits relative to the paucity of other Triassic herbivores indicates that they were key components of Late Triassic ecosystems. However, their evolutionary relationships remain contentious due, in large part, to their extensive dermal armor, which often obstructs observation of internal skeletal anatomy and limits access to potentially informative characters. In an attempt to address this problem we reanalyzed the holotype of a recently described species of Submitted 4 October 2017 Coahomasuchus, C. chathamensis, from the Sanford sub-basin of North Carolina using Accepted 24 January 2018 computed tomography (CT). CT scans of the holotype specimen clarify preservation Published 13 February 2018 of the skeleton, revealing several articulated vertebrae and ribs, an isolated vertebra, Corresponding author left ulna, left scapula, and the right humerus, though none of the material resulted in Devin K.
    [Show full text]
  • Paleontology and Paleoecology of the Newark Supergroup (Early Mesozoic, Eastern N0,Rth America)
    Chapter 8 Paleontology and paleoecology of the Newark Supergroup (early Mesozoic, eastern N0,rth America) PAUL E. OLSEN ABSTRACT The diverse depositional environments and rich fossil assemblages of the early Mesozoic Newark Supergroup of eastern North America can be subdivided into six broad environmental categories ranging from fault-scarp breccias in synsedimentary grabens developed directly along master boundary fault zones to deep-water zones of lakes. Each environmental category is characterized by its own range of taxa and modes of preservation. Environmental zones, except those directly caused by faulting, shifted laterally as lake levels rose and fell. Overt analogy between the lower trophic levels of aquatic ecosystems of modern lakes and those of the early Mesozoic is not appropriate. Diatoms were absent from the phytoplankton and large (0.3 - 1.0 cm) clam-shrimp comprised most of the zooplankton in Newark lakes, despite the abundant planktivorous fish. Like their modern counterparts, however, early Mesozoic ecosystems responded to a hierarchy of extrinsic en- vironmental perturbations. Longer-term perturbations which left marked records in Newark Supergroup records in- clude cyclical climate change controlled by orbital variations and perhaps the consequences of an asteroid impact. These perturbations affected the evolution and extinction of organisms and the metabolism of ecosystems in ways that differ both in magnitude and kind. The evolution of fish species-flocks and mass extinction at the Triassic - Jurassic boundary are but two examples at distant ends of the spectrum. Introduction The Newark Supergroup of eastern North America (Fig. 8-1) consists of the remnants of the fill of rift basins formed during the 45 million years of crustal thinning and stretching which led up to the Middle Jurassic breakup of Laurasia and the formation of the earliest oceanic crust.
    [Show full text]
  • Diverse New Microvertebrate Assemblage from the Upper Triassic Cumnock Formation, Sanford Subbasin, North Carolina, USA
    Archived version from NCDOCKS Institutional Repository http://libres.uncg.edu/ir/asu/ Diverse New Microvertebrate Assemblage from the Upper Triassic Cumnock Formation, Sanford Subbasin, North Carolina, USA By: Andrew B. Heckert, Jonathan S. Mitchell, Vincent P. Schneider, and Paul E. Olsen Abstract The Moncure microvertebrate locality in the Cumnock Formation, Sanford sub-basin, North Carolina, dramatically increases the known Late Triassic age vertebrate assemblage from the Deep River Basin. The 50,000 recovered microvertebrate fossils include osteichthyans, amphibians, and numerous lepidosauromorph, archosauri-form, and synapsid amniotes. Actinopterygian fossils consist of thousands of scales, teeth, skull, and lower jaw fragments, principally of redfieldiids and semionotids. Non-tetrapod sarcopterygians include the dipnoan Arganodus sp., the first record of lungfish in the Newark Supergroup. Temnospondyls are comparatively rare but the preserved centra, teeth, and skull fragments probably represent small (juvenile) metoposaurids. Two fragmentary teeth are assigned to the unusual reptile Colognathus obscurus (Case). Poorly preserved but intriguing records include acrodont and pleurodont jaw fragments tentatively assigned to lepidosaurs. Among the archosauriform teeth is a taxon distinct from R. callenderi that we assign to Revueltosaurus olseni new combination, a morphotype best assigned to cf. Galtonia, the first Newark Supergroup record of Crosbysaurus sp., and several other archosauriform tooth morphotypes, as well as grooved teeth assigned to the recently named species Uatchitodon schneideri. Synapsids represented by molariform teeth include both ‘‘traversodontids’’ assigned to aff. Boreogomphodon and the ‘‘dromatheriid’’ Microconodon. These records are biogeographically important, with many new records for the Cumnock Formation and/or the Newark Supergroup. In particular, Colognathus, Crosbysaurus, and Uatchitodon are known from basins of Adamanian age in the southwestern U.S.A.
    [Show full text]
  • Studies on Continental Late Triassic Tetrapod Biochronology. II. the Ischigualastian and a Carnian Global Correlation
    Journal of South American Earth Sciences 19 (2005) 219–239 www.elsevier.com/locate/jsames Studies on continental Late Triassic tetrapod biochronology. II. The Ischigualastian and a Carnian global correlation Max Cardoso Langer* Departamento de Biologia, FFCLRP, Universidade de Sa˜o Paulo (USP), Av. Bandeirantes 3900, 14040-901 Ribeira˜o Preto, SP, Brazil Received 1 December 2003; accepted 1 December 2004 Abstract The Ischigualastian represents a key land vertebrate faunachron for the correlation of Late Triassic terrestrial deposits worldwide, based on the abundant and diverse tetrapod fauna of the Ischigualasto Formation, NW Argentina. The first appearance data of the rhynchosaur Hyperodapedon and the dicynodont Jachaleria define its lower and upper limits, respectively. Fossil taxa that characterize the Ischigualastian include Hyperodapedon, the cynodont Exaeretodon, the aetosaur Aetosauroides, and herrerasaurid dinosaurs. On the basis of faunal similarities, the Ischigualastian can be traced throughout south Pangea to encompass the fossil assemblages of the Hyperodapedon assemblage zone, Santa Maria Formation, south Brazil; the Pebbly Arkose Formation, Zimbabwe; and the Lower Maleri Formation, India. This correlation contradicts tetrapod-based Late Triassic biochronologies that divide the Carnian epoch into two land vertebrate faunachrons, Otischalkian and Adamanian, on the basis of the succession of faunas in some North American continental sequences. However, the extension of these biochronologic units into south Pangea is based mainly on dubious records of index fossils, the taxonomic status of which are not clearly understood. By reassessing the taxonomic status and distribution of tetrapod taxa, this article defines an updated correlation basis for the Late Triassic of Pangea. q 2005 Elsevier Ltd. All rights reserved.
    [Show full text]