DOCSLIB.ORG

Origins and Evolution of the Antarctic Biota: an Introduction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Origins and Evolution of the Antarctic Biota: an Introduction Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 Origins and evolution of the Antarctic biota: an introduction J. A. CRAME British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK Within the last 25 years there has been a dra- in this volume L. R. M. Cocks provides a brief matic increase in our knowledge of the fossil but succinct review of Antarctica's place within record of Antarctica. Improved access to the Cambrian to Devonian Gondwana. It is perhaps remotest parts of the continent, the advent of not generally appreciated that the greater part offshore drilling and intensive study of early of Antarctica's extensive Early and Middle expedition collections have all led to the ac- Cambrian sedimentary record was laid down cumulation of a vast amount of data that under tropical conditions. The extensive stretches back nearly 600 Ma to the beginning of Shackleton Limestone of the Transantarctic the Cambrian period. No longer can Antarctica Mountains, and its correlatives, contains abun- be dismissed from our view of the history of life dant shelly faunas with Australian and Chinese on earth simply because so little is known about affinities, and part of the margin of what we it; it is fast becoming another crucial reference now know as the Gondwana supercontinent point for global palaeontological syntheses. formed a reef belt that protruded 10~ ~ into If, today we have an image of Antarctica as a the Northern Hemisphere. The most abundant remote, inhospitable continent that supports and characteristic early Palaeozoic fossils of little life, we now know that such a view cannot Antarctica are in fact archaeocyaths and F. be projected back indefinitely through time. Debrenne & P. D. Kruse show how, in con- Abundant plant and animal fossils from a variety junction with certain skeletal cyanobacteria and of periods point to much more benign climates algae, these primitive coral-like organisms were and immediately raise a series of interconnected the primary framework-builders of the reefs. questions: where did such organisms come from, Taxonomic revisions presented by these authors how long did they persist, and precisely when confirm the particularly strong faunal links be- (and how) did they become extinct? Can our tween Antarctica and South Australia in the most southerly continent throw further light on Early Cambrian. the long-term role of climate in driving evol- Amongst the inarticulate brachiopods, tri- utionary trends (e.g. Valentine 1967; Vrba lobites, primitive molluscs and other marine 1985)7 invertebrates that inhabited the Early Cambrian It was with points such as these in mind that a reefs and carbonate platforms, a particularly mixed group of palaeontologists, biologists, ge- important series of monoplacophorans and gas- ologists and geophysicists gathered together tropods has been identified by G. F. Webers & for an international discussion meeting on the E. Yoeheison. These occur in the Late 'Origins and evolution of the Antarctic biota' at Cambrian (Dresbachian) Minaret Formation of the Geological Society, London on 24 and 25 the Ellsworth Mountains and comprise some 20 May 1988. A further workshop day (26 May taxa. The most important of these is the mono- 1988) was held at the British Antarctic Survey, placophoran, Knightoconus antarcticus, which Cambridge and altogether over 100 scientists could well have been a direct ancestor of the from some 15 different countries took part in cephalopods. Its 7cm long, curving, cap-like the discussions. shell bears multiple internal septa along at least Obviously, in such a short space of time, it one-third of its length and these are perforated was not possible to cover all aspects of Antarctic by a rudimentary connecting tube (siphuncle). palaeontology, and some subjects were necess- The stratigraphic position of this species can be arily reviewed in greater detail than others. As demonstrated to be slightly beneath that of Palaeozoic biotas and biogeography were to be Plectronoceras, the first true cephalopod (from the subject of a complementary symposium China). ('Palaeozoic biogeography and palaeogeogra- In his review, Cocks points out that there is a phy'; Oxford, 14-19 August 1988), they were very limited Ordovician and Silurian sedimen- not examined exhaustively here. Nevertheless it tary and palaeontological record in Antarctica; was felt to be important to spend some time it is likely that this was a time of extensive up- considering Antarctica's first macrofossils, and lift and erosion. However, it is apparent that, From Crame, J. A. (ed.), 1989, Origins and Evolution of the Antarctic Biota, Geological Society Special Publication No. 47, pp. 1-8. Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 2 J.A. CRAME during the later part of early Palaeozoic time, phyllolepid placoderms, xenacanth sharks and profound changes were occurring in the dis- bothriolepid antiarchs. tribution of supercontinents and the large Collision of the Gondwana and Baltica/ Gondwana plate slid progressively over the con- Laurentia blocks in the latest Devonian to form temporary south pole. By the early Middle the single supercontinent of Pangea radically Devonian the pole lay under either S. Africa or alters our view of the subsequent evolution of S. America, and Antarctica came to occupy a life in the southern high latitudes. It has tra- mid- to high-latitude position (35~176 de- ditionally been felt that the classic 'Gondwana' pending on the reconstruction used). It has sequences in these regions, comprising Permo- essentially maintained this ever since. Carboniferous non-marine glacial facies Although palynomorphs of probable Early overlain by coal measure facies containing a Devonian age are known from the Beacon Glossopteris flora and Triassic non-marine facies Supergroup of southern Victoria Land (Kyle with a Lystrosauras fauna and Dicroidium flora, 1977), the most characteristic fossils of this were the product of supercontinent isolation. age comprise a series of marine invertebrates However, viewed in terms of the single super- from the Horlick Mountains, Ohio Range, continent model, it would now appear that Transantarctic Mountains. These clearly have these classic sedimentary facies and biotas can Malvinokaffric Province (i.e. cool-water) af- be re-interpreted as austral components of a finities (Doumani et al. 1965) and testify to Pangean super-sequence (Veevers 1988). The the comparatively high-latitude position of basal glacial successions reflect the mid- to high Antarctica in the Early Devonian. Some Lower southern latitudes and succeeding beds contain Devonian fish fossils have been recorded from a provincial biota separated from boreal Pangea both the Horlick and Ellsworth mountain ranges on the east by the Tethyan gulf and on the west and Middle-Late Devonian plant remains are by a tropical land zone (Veevers 1988, fig. 2c). known from the Ruppert Coast of Marie Byrd Although Veevers dates the coalescence of Land (Grindley et al. 1980); however, these are Gondwana and Euramerica slightly later (mid- overshadowed in both stratigraphical and bio- Carboniferous, c. 320 Ma), it is clear from his geographical importance by the Givetian (late reconstruction that the classic Glossopter& flora Middle Devonian) Aztec Siltstone fish fauna now has a distinctly austral aspect. from southern Victoria Land. Dicynodonts, a widespread, morphologically In a comprehensive review, G. C. Young diverse group of mammal-like reptiles prevalent shows that the Aztec fauna comprises not only during the Permian and Triassic, are the subject the oldest but also one of the most diverse fossil of a comprehensive review by S. L. De Fauw. vertebrate assemblages yet found in Antarctica. Essentially composed of herbivores, this group Over 30 taxa have so far been identified and appears to have undergone two significant these belong to four major groups of jawed adaptive radiations: one in the Late Permian fishes -- the placoderms (armoured fishes), (Tatarian) and the other in the early Middle acanthodians (spiney-finned fishes), chon- Triassic (Anisian). Both radiations were un- drichthyans (sharks and their relatives) and doubtedly aided by the development of homo- osteichthyans (boney fish) -- and one group of geneous Gondwana floras (the Glossopteris and agnathans (primitive jawless vertebrates; the Dicroidium floras, respectively), but it is import- thelodontids). The fauna has its strongest bio- ant to emphasize that many genera achieved geographic links with eastern Australia and very widespread distributions in Pangea. The indicates that a distinctive East Gondwana ver- equatorial barrier does not appear to have been tebrate faunal province persisted until at least impenetrable to terrestrial vertebrates (see also the end of the Middle Devonian (Young 1981). Chatterjee 1987), and of the 35 known dicyno- By the latest Devonian the vertebrate faunas of dont genera approximately 11 are known from Euramerica and East Gondwana are much more two or more cratonic regions. Lystrosaurus, the similar, particularly in the composition of their famous dicynodont from the Fremouw For- respective freshwater assemblages. Young links mation of Antarctica, is now known to have this change to major palaeogeographic recon- been particularly widely dispersed. Semi- structions and suggests that this may have been aquatic and probably able to forage for a variety the time when the ocean separating these
Load more

Recommended publications
  • University Microfilms, Inc., Ann Arbor, Michigan GEOLOGY of the SCOTT GLACIER and WISCONSIN RANGE AREAS, CENTRAL TRANSANTARCTIC MOUNTAINS, ANTARCTICA
    This dissertation has been /»OOAOO m icrofilm ed exactly as received MINSHEW, Jr., Velon Haywood, 1939- GEOLOGY OF THE SCOTT GLACIER AND WISCONSIN RANGE AREAS, CENTRAL TRANSANTARCTIC MOUNTAINS, ANTARCTICA. The Ohio State University, Ph.D., 1967 Geology University Microfilms, Inc., Ann Arbor, Michigan GEOLOGY OF THE SCOTT GLACIER AND WISCONSIN RANGE AREAS, CENTRAL TRANSANTARCTIC MOUNTAINS, ANTARCTICA DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University by Velon Haywood Minshew, Jr. B.S., M.S, The Ohio State University 1967 Approved by -Adviser Department of Geology ACKNOWLEDGMENTS This report covers two field seasons in the central Trans- antarctic Mountains, During this time, the Mt, Weaver field party consisted of: George Doumani, leader and paleontologist; Larry Lackey, field assistant; Courtney Skinner, field assistant. The Wisconsin Range party was composed of: Gunter Faure, leader and geochronologist; John Mercer, glacial geologist; John Murtaugh, igneous petrclogist; James Teller, field assistant; Courtney Skinner, field assistant; Harry Gair, visiting strati- grapher. The author served as a stratigrapher with both expedi­ tions . Various members of the staff of the Department of Geology, The Ohio State University, as well as some specialists from the outside were consulted in the laboratory studies for the pre­ paration of this report. Dr. George E. Moore supervised the petrographic work and critically reviewed the manuscript. Dr. J. M. Schopf examined the coal and plant fossils, and provided information concerning their age and environmental significance. Drs. Richard P. Goldthwait and Colin B. B. Bull spent time with the author discussing the late Paleozoic glacial deposits, and reviewed portions of the manuscript.
    [Show full text]
  • On the Continuity of Background and Mass Extinction
    Paleobiology, 29(4), 2003, pp. 455±467 On the continuity of background and mass extinction Steve C. Wang Abstract.ÐDo mass extinctions grade continuously into the background extinctions occurring throughout the history of life, or are they a fundamentally distinct phenomenon that cannot be explained by processes responsible for background extinction? Various criteria have been proposed for addressing this question, including approaches based on physical mechanisms, ecological se- lectivity, and statistical characterizations of extinction intensities. Here I propose a framework de®ning three types of continuity of mass and background extinc- tionsÐcontinuity of cause, continuity of effect, and continuity of magnitude. I test the third type of continuity with a statistical method based on kernel density estimation. Previous statistical ap- proaches typically have examined quantitative characteristics of mass extinctions (such as metrics of extinction intensity) and compared them with the distribution of such characteristics associated with background extinctions. If mass extinctions are outliers, or are separated by a gap from back- ground extinctions, the distinctness of mass extinctions is supported. In this paper I apply Silverman's Critical Bandwidth Test to test for the continuity of mass ex- tinctions by applying kernel density estimation and bootstrap modality testing. The method im- proves on existing work based on searching for gaps in histograms, in that it does not depend on arbitrary choices of parameters (such as bin widths for histograms), and provides a direct estimate of the signi®cance of continuities or gaps in observed extinction intensities. I am thus able to test rigorously whether differences between mass extinctions and background extinctions are statisti- cally signi®cant.
    [Show full text]
  • Appendix 3.Pdf
    A Geoconservation perspective on the trace fossil record associated with the end – Ordovician mass extinction and glaciation in the Welsh Basin Item Type Thesis or dissertation Authors Nicholls, Keith H. Citation Nicholls, K. (2019). A Geoconservation perspective on the trace fossil record associated with the end – Ordovician mass extinction and glaciation in the Welsh Basin. (Doctoral dissertation). University of Chester, United Kingdom. Publisher University of Chester Rights Attribution-NonCommercial-NoDerivatives 4.0 International Download date 26/09/2021 02:37:15 Item License http://creativecommons.org/licenses/by-nc-nd/4.0/ Link to Item http://hdl.handle.net/10034/622234 International Chronostratigraphic Chart v2013/01 Erathem / Era System / Period Quaternary Neogene C e n o z o i c Paleogene Cretaceous M e s o z o i c Jurassic M e s o z o i c Jurassic Triassic Permian Carboniferous P a l Devonian e o z o i c P a l Devonian e o z o i c Silurian Ordovician s a n u a F y r Cambrian a n o i t u l o v E s ' i k s w o Ichnogeneric Diversity k p e 0 10 20 30 40 50 60 70 S 1 3 5 7 9 11 13 15 17 19 21 n 23 r e 25 d 27 o 29 M 31 33 35 37 39 T 41 43 i 45 47 m 49 e 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 Number of Ichnogenera (Treatise Part W) Ichnogeneric Diversity 0 10 20 30 40 50 60 70 1 3 5 7 9 11 13 15 17 19 21 n 23 r e 25 d 27 o 29 M 31 33 35 37 39 T 41 43 i 45 47 m 49 e 51 53 55 57 59 61 c i o 63 z 65 o e 67 a l 69 a 71 P 73 75 77 79 81 83 n 85 a i r 87 b 89 m 91 a 93 C Number of Ichnogenera (Treatise Part W)
    [Show full text]
  • Western North Greenland (Laurentia)
    BULLETIN OF THE GEOLOGICAL SOCIETY OF DENMARK · VOL. 69 · 2021 Trilobite fauna of the Telt Bugt Formation (Cambrian Series 2–Miaolingian Series), western North Greenland (Laurentia) JOHN S. PEEL Peel, J.S. 2021. Trilobite fauna of the Telt Bugt Formation (Cambrian Series 2–Mi- aolingian Series), western North Greenland (Laurentia). Bulletin of the Geological Society of Denmark, Vol. 69, pp. 1–33. ISSN 2245-7070. https://doi.org/10.37570/bgsd-2021-69-01 Trilobites dominantly of middle Cambrian (Miaolingian Series, Wuliuan Stage) Geological Society of Denmark age are described from the Telt Bugt Formation of Daugaard-Jensen Land, western https://2dgf.dk North Greenland (Laurentia), which is a correlative of the Cape Wood Formation of Inglefield Land and Ellesmere Island, Nunavut. Four biozones are recognised in Received 6 July 2020 Daugaard-Jensen Land, representing the Delamaran and Topazan regional stages Accepted in revised form of the western USA. The basal Plagiura–Poliella Biozone, with Mexicella cf. robusta, 16 December 2020 Kochiella, Fieldaspis? and Plagiura?, straddles the Cambrian Series 2–Miaolingian Series Published online 20 January 2021 boundary. It is overlain by the Mexicella mexicana Biozone, recognised for the first time in Greenland, with rare specimens of Caborcella arrojosensis. The Glossopleura walcotti © 2021 the authors. Re-use of material is Biozone, with Glossopleura, Clavaspidella and Polypleuraspis, dominates the succes- permitted, provided this work is cited. sion in eastern Daugaard-Jensen Land but is seemingly not represented in the type Creative Commons License CC BY: section in western outcrops, likely reflecting the drastic thinning of the formation https://creativecommons.org/licenses/by/4.0/ towards the north-west.
    [Show full text]
  • Lee-Riding-2018.Pdf
    Earth-Science Reviews 181 (2018) 98–121 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Marine oxygenation, lithistid sponges, and the early history of Paleozoic T skeletal reefs ⁎ Jeong-Hyun Leea, , Robert Ridingb a Department of Geology and Earth Environmental Sciences, Chungnam National University, Daejeon 34134, Republic of Korea b Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA ARTICLE INFO ABSTRACT Keywords: Microbial carbonates were major components of early Paleozoic reefs until coral-stromatoporoid-bryozoan reefs Cambrian appeared in the mid-Ordovician. Microbial reefs were augmented by archaeocyath sponges for ~15 Myr in the Reef gap early Cambrian, by lithistid sponges for the remaining ~25 Myr of the Cambrian, and then by lithistid, calathiid Dysoxia and pulchrilaminid sponges for the first ~25 Myr of the Ordovician. The factors responsible for mid–late Hypoxia Cambrian microbial-lithistid sponge reef dominance remain unclear. Although oxygen increase appears to have Lithistid sponge-microbial reef significantly contributed to the early Cambrian ‘Explosion’ of marine animal life, it was followed by a prolonged period dominated by ‘greenhouse’ conditions, as sea-level rose and CO2 increased. The mid–late Cambrian was unusually warm, and these elevated temperatures can be expected to have lowered oxygen solubility, and to have promoted widespread thermal stratification resulting in marine dysoxia and hypoxia. Greenhouse condi- tions would also have stimulated carbonate platform development, locally further limiting shallow-water cir- culation. Low marine oxygenation has been linked to episodic extinctions of phytoplankton, trilobites and other metazoans during the mid–late Cambrian.
    [Show full text]
  • Early and Middle Cambrian Trilobites from Antarctica
    Early and Middle Cambrian Trilobites From Antarctica GEOLOGICAL SURVEY PROFESSIONAL PAPER 456-D Early and Middle Cambrian Trilobites From Antarctica By ALLISON R. PALMER and COLIN G. GATEHOUSE CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA GEOLOGICAL SURVEY PROFESSIONAL PAPER 456-D Bio stratigraphy and regional significance of nine trilobite faunules from Antarctic outcrops and moraines; 28 species representing 21 genera are described UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 73-190734 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 70 cents (paper cover) Stock Number 2401-2071 CONTENTS Page Page Abstract_ _ ________________________ Dl Physical stratigraphy______________________________ D6 I&troduction. _______________________ 1 Regional correlation within Antarctica ________________ 7 Biostratigraphy _____________________ 3 Systematic paleontology._____-_______-____-_-_-----_ 9 Early Cambrian faunules.________ 4 Summary of classification of Antarctic Early and Australaspis magnus faunule_ 4 Chorbusulina wilkesi faunule _ _ 5 Middle Cambrian trilobites. ___________________ 9 Chorbusulina subdita faunule _ _ 5 Agnostida__ _ _________-____-_--____-----__---_ 9 Early Middle Cambrian f aunules __ 5 Redlichiida. __-_--------------------------_---- 12 Xystridura mutilinia faunule- _ 5 Corynexochida._________--________-_-_---_----_
    [Show full text]
  • Late Dresbachian (Late Cambrian) Biostratigraphy of North America
    CHRISTINA LOCHMAN-BALK Department of Geosdence, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801 Late Dresbachian (Late Cambrian) Biostratigraphy of North America ABSTRACT bachian Aphelaspis Zone (Howell and Dresbachian time in the central Texas others, 1944) into an older Aphelaspis Zone section, with only a very short hiatus? before An examination of the taxonomic com- and a younger post-Aphelaspis Zone. the appearance of the Elvinia Zone fauna. position of the North American late Trilobites and brachiopods assigned by The short hiatus? refers to the well-defined Dresbachian faunules described to date Palmer to the Aphelaspis Zone are listed in faunal break and disconformity between the indicates that there is an Aphelaspis Zone Table 1. In the basal beds of the zone, Palmer Lion Mountain Sandstone Member of the faunal assemblage characteristic of the early Riley Formation and the Welge Sandstone half of the late Dresbachian Stage and a Member of the Wilberns Formation (Loch- TABLE 1. TRILOBITES ÄND BRACHIOPODS ASSIGNED TO Dunderbergia Zone faunal assemblage APHELASPIS ZONE, RILEY FORMATION, TEXAS, man, 1938; Freeman, 1969). characteristic of the later half. The diagnos- BY PALMER (1955) From 1951, Palmer was engaged in the tic elements of each of the assemblages are Aphelaspis walcotti study of the Late Cambrian faunas of the listed, and the biozones of the common Labiostria (now Aphelaspis) conveximavginata Great Basin and published late Dresbachian Labiostria (now Aphelaspis) platifrons trilobite genera are noted so that correct Dunderbergia variagranula faunal lists in Nolan and others (1956) and Eaaschella (now Glaphyraspis) omata intracontinental correlations may be made.
    [Show full text]
  • On the Causes of Mass Extinctions
    ÔØ ÅÒÙ×Ö ÔØ On the causes of mass extinctions David P.G. Bond, Stephen E. Grasby PII: S0031-0182(16)30691-5 DOI: doi: 10.1016/j.palaeo.2016.11.005 Reference: PALAEO 8040 To appear in: Palaeogeography, Palaeoclimatology, Palaeoecology Received date: 16 August 2016 Revised date: 2 November 2016 Accepted date: 5 November 2016 Please cite this article as: Bond, David P.G., Grasby, Stephen E., On the causes of mass extinctions, Palaeogeography, Palaeoclimatology, Palaeoecology (2016), doi: 10.1016/j.palaeo.2016.11.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT On the causes of mass extinctions David P.G. Bond1* and Stephen E. Grasby2, 3 1School of Environmental Sciences, University of Hull, Hull, HU6 7RX, United Kingdom 2Geological Survey of Canada, 3303 33rd St. N.W. Calgary AB Canada, T2L 2A7. 3Department of Geoscience, University of Calgary, Calgary AB Canada. *Corresponding author. E-mail: [email protected] (D. Bond). ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT ABSTRACT The temporal link between large igneous province (LIP) eruptions and at least half of the major extinctions of the Phanerozoic implies that large scale volcanism is the main driver of mass extinction.
    [Show full text]
  • Geology of Michigan and the Great Lakes
    35133_Geo_Michigan_Cover.qxd 11/13/07 10:26 AM Page 1 “The Geology of Michigan and the Great Lakes” is written to augment any introductory earth science, environmental geology, geologic, or geographic course offering, and is designed to introduce students in Michigan and the Great Lakes to important regional geologic concepts and events. Although Michigan’s geologic past spans the Precambrian through the Holocene, much of the rock record, Pennsylvanian through Pliocene, is miss- ing. Glacial events during the Pleistocene removed these rocks. However, these same glacial events left behind a rich legacy of surficial deposits, various landscape features, lakes, and rivers. Michigan is one of the most scenic states in the nation, providing numerous recre- ational opportunities to inhabitants and visitors alike. Geology of the region has also played an important, and often controlling, role in the pattern of settlement and ongoing economic development of the state. Vital resources such as iron ore, copper, gypsum, salt, oil, and gas have greatly contributed to Michigan’s growth and industrial might. Ample supplies of high-quality water support a vibrant population and strong industrial base throughout the Great Lakes region. These water supplies are now becoming increasingly important in light of modern economic growth and population demands. This text introduces the student to the geology of Michigan and the Great Lakes region. It begins with the Precambrian basement terrains as they relate to plate tectonic events. It describes Paleozoic clastic and carbonate rocks, restricted basin salts, and Niagaran pinnacle reefs. Quaternary glacial events and the development of today’s modern landscapes are also discussed.
    [Show full text]
  • Depositional History of Pre-Devonian Strata and Timing of Ross Orogenic Tectonism in the Central Transantarctic Mountains, Antarctica
    Depositional history of pre-Devonian strata and timing of Ross orogenic tectonism in the central Transantarctic Mountains, Antarctica Paul M. Myrow* Department of Geology, Colorado College, Colorado Springs, Colorado 80903, USA Michael C. Pope Department of Geology, Washington State University, Pullman, Washington 99164, USA John W. Goodge Department of Geological Sciences, Southern Methodist University, Dallas, Texas 75275, USA Woodward Fischer Department of Geology, Colorado College, Colorado Springs, Colorado 80903, USA Alison R. Palmer Institute for Cambrian Studies, 445 North Cedarbrook Road, Boulder, Colorado 80304-0417, USA ABSTRACT small fraction of its previous extent. The into trilobite- and hyolithid-bearing calcar- basal unit of the Byrd GroupÐthe predom- eous siltstone of the Starshot Formation A combination of ®eld mapping, detailed inantly carbonate ramp deposits of the and alluvial-fan deposits of the Douglas sedimentology, carbon isotope chemostra- Shackleton LimestoneÐrest with presumed Conglomerate. Trilobite fauna from the tigraphy, and new paleontological ®nds unconformity on the restricted Goldie For- lowermost siltstone deposits of the Starshot provides a signi®cantly improved under- mation. Paleontological data and carbon Formation date the onset of this transition standing of the depositional and tectonic isotope stratigraphy indicate that the Low- as being late Botomian. history of uppermost Neoproterozoic and er Cambrian Shackleton Limestone ranges The abrupt transition from the Shackle- lower Paleozoic strata of the central Trans- from lower Atdabanian through upper ton Limestone to a large-scale, upward- antarctic Mountains. On the basis of these Botomian. coarsening siliciclastic succession records data, we suggest revision of the existing This study presents the ®rst description deepening of the outer platform and then stratigraphy, including introduction of new of a depositional contact between the deposition of an eastward-prograding mo- formations, as follows.
    [Show full text]
  • Redalyc.Early Cambrian Archaeocyathan Limestone Blocks In
    Geologica Acta: an international earth science journal ISSN: 1695-6133 [email protected] Universitat de Barcelona España GONZÁLEZ, P.D.; TORTELLO, M.F.; DAMBORENEA, S.E. Early Cambrian archaeocyathan limestone blocks in low-grade meta-conglomerate from El Jagüelito Formation (Sierra Grande, Río Negro, Argentina) Geologica Acta: an international earth science journal, vol. 9, núm. 2, junio, 2011, pp. 159-173 Universitat de Barcelona Barcelona, España Available in: http://www.redalyc.org/articulo.oa?id=50521609003 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Geologica Acta, Vol.9, Nº 2, June 2011, 159-173 DOI: 10.1344/105.000001650 Available online at www.geologica-acta.com Early Cambrian archaeocyathan limestone blocks in low-grade meta-conglomerate from El Jagüelito Formation (Sierra Grande, Río Negro, Argentina) 1 2 2 P.D. GONZÁLEZ M.F. TORTELLO S.E. DAMBORENEA 1 Centro de Investigaciones Geológicas, (UNLP - CONICET) 1 Nº 644, B1900TAC, La Plata (Buenos Aires), Argentina. E-mail: [email protected]; Fax: +54-221-4827560 2 CONICET – División Paleozoología Invertebrados, Museo de Ciencias Naturales Paseo del Bosque s/n, 1900 La Plata (Buenos Aires), Argentina. Tortello E-mail: [email protected] Damborenea E-mail: [email protected] ABSTRACT Massive grey limestone blocks containing a fairly diverse but poorly preserved archaeocyath fauna were recovered from a meta-conglomerate bed in the El Jagüelito Formation (Sierra Grande area, Eastern North Patagonian Massif, Río Negro, Argentina).
    [Show full text]
  • Precambrian to Earliest Mississippian Stratigraphy, Geologic History, and Paleogeography of Northwestern Colorado and West-Central Colorado
    Precambrian to Earliest Mississippian Stratigraphy, Geologic History, and Paleogeography of Northwestern Colorado and West-Central Colorado Prepared in cooperation with the Colorado Geological Survey U.S. GEOLOGICAL SURVEY BULLETIN 1 787-U AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with the last offerings, are given in the current-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publications released prior to the current year are listed in the most recent annual "Price and Availability List." Publications that are listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" are no longer available. Prices of reports released to the open files are given in the listing "U.S. Geological Survey Open-File Reports," updated monthly, which is for sale in microfiche from the U.S. Geological Survey Books and Open-File Reports Sales, Box 25286, Denver, CO 80225. Order U.S. Geological Survey publications by mail or over the counter from the offices given below. BY MAIL OVER THE COUNTER Books Books Professional Papers, Bulletins, Water-Supply Papers, Tech­ Books of the U.S. Geological Survey are available over the niques of Water-Resources Investigations, Circulars, publications counter at the following U.S. Geological Survey offices, all of of general interest (such as leaflets, pamphlets, booklets), single which are authorized agents of the Superintendent of Documents. copies of periodicals (Earthquakes & Volcanoes, Preliminary De­ termination of Epicenters), and some miscellaneous reports, includ­ ANCHORAGE, Alaska-4230 University Dr., Rm.
    [Show full text]