DOCSLIB.ORG

Ontogeny of the Early Ordovician Olenid Trilobite Jujuyaspis Keidelikobayashi from Northwestern Argentina

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Ontogeny of the Early Ordovician Olenid Trilobite Jujuyaspis Keidelikobayashi from Northwestern Argentina AMEGHINIANA (Rev. Asoc. Paleontol. Argent.) - 40 (3): 257-275. Buenos Aires, 30-09-2003 ISSN0002-7014 Ontogeny of the Early Ordovician olenid trilobite Jujuyaspis keideliKobayashi from northwestern Argentina M. Franco TORTELLO1and Euan N. K. CLARKSON2 Abstract.The Early Ordovician olenid trilobite Jujuyaspiskeideli Kobayashi is well-preserved in black shale facies of the Santa Rosita Fomation at Purmamarca, northwestern Argentina. Although protaspides are not represented in the collections, isolated tagmata and articulated specimens from the early meraspid stages onwards are available for ontogenetic study. Meraspid Group 1 is characterized by having an hexagonal cephalic outline, three distinct glabellar furrows, and seven marginal spines. In meraspid Group 2 the cephalon has become reniform in outline, the glabellar furrows are less developed, and the fixigenae exhibit a pair of ocular ridges. Meraspid Group 3 is characterized by an adult-like cephalon lacking both ocular ridges and paired marginal spines. At this stage the thorax has very long pleural spines which, contrasting greatly with those of the adult, are laterally splayed out. In meraspid Group 4 the cephalon bears a well- developed occipital spine or a conspicuous occipital node, the glabella possesses two pairs of lateral fur- rows, and the thorax exhibits axial nodes on the anterior segments and shorter, more posteriorly directed lateral spines. Early holaspides retain some of the later meraspid morphological features. The hypostome of the species is documented for the first time. Information on the intraspecific variability of J. keidelien- ables us to discuss its systematic affinities in a new context. A monospecific, age-sorted clustered assem- blage assignable to holaspid Group 1 could represent specimens that aggregated together for synchronized exuviation. Early meraspides of Jujuyaspisare assumed to be pelagic, a fact that must have facilitated the worldwide distribution of the genus, whereas holaspides may have had a nekto-benthic mode of life. Resumen.ONTOGENIADELTRILOBITEOLÉNIDOJUJUYASPISKEIDELIKOBAYASHI(ORDOVÍCICOTEMPRANO) DEL NOROESTEARGENTINO. El trilobite olénido Jujuyaspis keideliKobayashi se encuentra bien preservado en la fa- cies de lutitas negras de la Formación Santa Rosita (Ordovícico Temprano) en Purmamarca, noroeste de Argentina. Aunque la fase protaspis no está representada en las colecciones, éstas contienen tagma aislados y ejemplares completos asignables a estadios meráspidos tempranos y siguientes. El grupo meráspido 1 es- tá caracterizado por su contorno cefálico hexagonal, tres pares de surcos glabelares conspicuos y siete es- pinas marginales. En el grupo meráspido 2 el céfalo adquiere un contorno reniforme, los surcos glabelares están menos desarrollados, y las mejillas fijas exhiben un par de aristas oculares. El grupo meráspido 3 es- tá caracterizado por un céfalo de aspecto similar al del adulto, desprovisto de aristas oculares y espinas marginales pares. En este estadio el tórax presenta espinas pleurales muy largas que, contrastando en gran medida con las del adulto, están expandidas lateralmente. En el grupo meráspido 4 el céfalo posee una es- pina occipital bien desarrollada o un nodo occipital conspicuo, la glabela presenta dos pares de surcos glabelares someros, y el tórax exhibe nodos axiales sobre los primeros segmentos y espinas laterales más cortas que las de estadios anteriores, dirigidas más posteriormente. Los ejemplares holáspidos tempranos retienen estos últimos caracteres. Se documenta por primera vez el hipostoma de la especie. Información sobre la variabilidad intraespecífica de J. keidelipermite discutir sus afinidades sistemáticas en un nuevo contexto. Una asociación mono-específica compuesta por numerosos ejemplares asignables al grupo holáspido 1 podría representar individuos reunidos para mudar en forma sincronizada. Los meráspidos tempranos de Jujuyaspisson considerados formas pelágicas, hábito que debe haber facilitado la amplia dis- tribución del género, mientras que los holáspidos podrían haber tenido un modo de vida necto-bentónico. Key words.Jujuyaspis. Trilobita. Olenidae. Early Ordovician. Argentina. Ontogeny. Ecdysis. Paleoecology. Palabras clave.Jujuyaspis. Trilobita. Olenidae. Ordovícico Temprano. Argentina. Ontogenia. Ecdisis. Paleoecología. Introduction Cambrian and earliest Ordovician age are widely distributed in the Eastern Cordillera of Argentina The Santa Rosita Formation (lower part), and southern Bolivia (e.g. Harrington inHarrington Iscayachi Formation and equivalents of latest and Leanza, 1957; Turner, 1960; Branisa, 1965; Aceño- 1Departamento Científico Paleontología Invertebrados, Museo de laza, 1968; Suárez Soruco, 1976). Lithologically, they Ciencias Naturales, Paseo del Bosque s/nº, 1900 La Plata, Argentina. are characterized by greenish and black shales and [email protected] sandstones, with rare interspersed marl and lime- 2Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, United Kingdom. stone layers, representing both shallow marine set- [email protected] tings affected by storms and waves and outer shelf ©Asociación Paleontológica Argentina AMGHB2-0002-7014/03$00.00+.50 258 M.F. Tortello and E.N.K. Clarkson environments below storm-wave base. These units together with the olenids Parabolinella argentinensis lie on Cambrian quartzites of the Meson and Kobayashi, Angelina hyeronimi(Kayser), Bienvilliasp. Tucumilla groups in Argentina and Bolivia respec- and Plicatolinasp., and the agnostoids Micragnostus tively (Turner, 1960; Schlatter and Nederloff, 1966). In sp., Anglagnostussp. and Gymnagnostussp. (Koba- addition, the Upper Cambrian-lowest Ordovician is yashi, 1936; Harrington, 1938; Harrington and locally represented in the Famatina Range (La Rioja Leanza, 1943, 1952, 1957; Aceñolaza and Aceñolaza, Province, Argentina), where the lower member of the 1992; Aceñolaza, 1996; Mángano et al., 1996; Tortello Volcancito Formation is mainly composed of outer and Aceñolaza, 1999; Aceñolaza et al., 2001). The de- shelf marls and shales and inner shelf sandstones positional environment of the Purmamarca Shales, and mudstones, resting unconformably upon the dominated by quiet, low-oxygen-water bottom con- metamorphosed Cambrian rocks of the Negro ditions, resulted in the accumulation of many articu- Peinado Formation (Harrington inHarrington and lated specimens with a good state of preservation. Leanza, 1957; Esteban, 1999). Although the genus Jujuyaspishas been described Fossils are abundant in these formations. from different lithology in numerous localities in the Trilobites and brachiopods are especially rich, as well world, references to material assignable to early on- as graptolites, conodonts, gastropods and echino- togenetic stages are scarce. Dense clusters of well- derms. As is usual in other parts of the world, olenid preserved individuals of J. keideli, and numerous and agnostoid trilobites are better represented in specimens assignable to early meraspid stages on- dark and black shale facies, often occurring in a good wards have been recently found in the Alta Creek state of preservation. After early studies by Kayser (Purmamarca area) (figure 1). In order to emend the (1876, 1897), Kobayashi (1936, 1937) and Harrington original description of J. keideliand to discuss its (1938), Harrington and Leanza (1957) described in affinities and possible mode of life, the ontogeny, in- great detail numerous species of trilobites and pro- traspecific variability, and moulting of the species are vided a biostratigraphic scheme which, with slight herein described. New morphological and biostrati- modification, is still standing. The Parabolina(Neopa- graphic data enable us to debate the ecological role of rabolina) frequensargentinaZone, originally wholly as- this taxon in the olenid communities of the lowest signed to the lower Tremadoc, provides a unique op- Ordovician of Argentina. portunity to evaluate the Cambrian-Ordovician tran- sition in South America. A varied agnostoid fauna, The genus Jujuyaspis: occurrence which occurs along with some olenid species, char- and importance acterizes the lower part of this biozone, indicating a latest Cambrian age (Tortello and Esteban, 1999, JujuyaspisKobayashi, 1936, is a cosmopolitan 2003; Tortello, 2003). On the other hand, the upper olenid that has been recorded in both shales and part of the unit is dominated by the lower Tremadoc limestones close to the Cambro-Ordovician bound- olenid Jujuyaspis keideliKobayashi. ary. In the absence of graptolites and conodonts, the Jujuyaspis keideliis one of the most abundant taxa genus has proved to have great biostratigraphic va- in northwestern Argentina (Harrington and Leanza, lue as an international guide for the lowermost 1957). It has been described from both thick strati- Tremadoc (see Aceñolaza and Aceñolaza, 1992; graphic sections, in which the sequences are well rep- Cooper et al., 2001). resented (Tortello and Esteban, 1999; Tortello et al., In North China and Korea, the species Jujuyaspis 1999), and smaller, isolated exposures. The type area sinensisZhou was documented from the Yosimuraspis ofJujuyaspis keidelibelongs to the later category. It is Zone (Early Ordovician) (e.g. Chen et al., 1980; Zhou at Purmamarca, in the Quebrada de Humahuaca and Zhang, 1985; Kim and Choi, 2000), and J. kelleri (Jujuy Province) (Kobayashi, 1936), where a series of (Balashova) was described from similar stratigraphic west
Load more

Recommended publications
  • Cambrian Phytoplankton of the Brunovistulicum – Taxonomy and Biostratigraphy
    MONIKA JACHOWICZ-ZDANOWSKA Cambrian phytoplankton of the Brunovistulicum – taxonomy and biostratigraphy Polish Geological Institute Special Papers,28 WARSZAWA 2013 CONTENTS Introduction...........................................................6 Geological setting and lithostratigraphy.............................................8 Summary of Cambrian chronostratigraphy and acritarch biostratigraphy ...........................13 Review of previous palynological studies ...........................................17 Applied techniques and material studied............................................18 Biostratigraphy ........................................................23 BAMA I – Pulvinosphaeridium antiquum–Pseudotasmanites Assemblage Zone ....................25 BAMA II – Asteridium tornatum–Comasphaeridium velvetum Assemblage Zone ...................27 BAMA III – Ichnosphaera flexuosa–Comasphaeridium molliculum Assemblage Zone – Acme Zone .........30 BAMA IV – Skiagia–Eklundia campanula Assemblage Zone ..............................39 BAMA V – Skiagia–Eklundia varia Assemblage Zone .................................39 BAMA VI – Volkovia dentifera–Liepaina plana Assemblage Zone (Moczyd³owska, 1991) ..............40 BAMA VII – Ammonidium bellulum–Ammonidium notatum Assemblage Zone ....................40 BAMA VIII – Turrisphaeridium semireticulatum Assemblage Zone – Acme Zone...................41 BAMA IX – Adara alea–Multiplicisphaeridium llynense Assemblage Zone – Acme Zone...............42 Regional significance of the biostratigraphic
    [Show full text]
  • A New Middle Cambrian Trilobite with a Specialized Cephalon from Shandong Province, North China
    Editors' choice A new middle Cambrian trilobite with a specialized cephalon from Shandong Province, North China ZHIXIN SUN, HAN ZENG, and FANGCHEN ZHAO Sun, Z., Zeng, H., and Zhao, F. 2020. A new middle Cambrian trilobite with a specialized cephalon from Shandong Province, North China. Acta Palaeontologica Polonica 65 (4): 709–718. Trilobites achieved their maximum generic diversity in the Cambrian, but the peak of morphological disparity of their cranidia occurred in the Middle to Late Ordovician. Early to middle Cambrian trilobites with a specialized cephalon are rare, especially among the ptychoparioids, a group of libristomates featuring the so-called “generalized” bauplan. Here we describe an unusual ptychopariid trilobite Phantaspis auritus gen. et sp. nov. from the middle Cambrian (Miaolingian, Wuliuan) Mantou Formation in the Shandong Province, North China. This new taxon is characterized by a cephalon with an extended anterior area of double-lobate shape resembling a pair of rabbit ears in later ontogenetic stages; a unique type of cephalic specialization that has not been reported from other trilobites. Such a peculiar cephalon as in Phantaspis provides new insights into the variations of cephalic morphology in middle Cambrian trilobites, and may represent a heuristic example of ecological specialization to predation or an improved discoidal enrollment. Key words: Trilobita, Ptychopariida, ontogeny, specialization, Miaolingian, Paleozoic, Longgang, Asia. Zhixin Sun [[email protected]], Han Zeng [[email protected]], and Fangchen Zhao [[email protected]] (cor­ responding author), State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palae­ ontology and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
    [Show full text]
  • Available Generic Names for Trilobites
    AVAILABLE GENERIC NAMES FOR TRILOBITES P.A. JELL AND J.M. ADRAIN Jell, P.A. & Adrain, J.M. 30 8 2002: Available generic names for trilobites. Memoirs of the Queensland Museum 48(2): 331-553. Brisbane. ISSN0079-8835. Aconsolidated list of available generic names introduced since the beginning of the binomial nomenclature system for trilobites is presented for the first time. Each entry is accompanied by the author and date of availability, by the name of the type species, by a lithostratigraphic or biostratigraphic and geographic reference for the type species, by a family assignment and by an age indication of the type species at the Period level (e.g. MCAM, LDEV). A second listing of these names is taxonomically arranged in families with the families listed alphabetically, higher level classification being outside the scope of this work. We also provide a list of names that have apparently been applied to trilobites but which remain nomina nuda within the ICZN definition. Peter A. Jell, Queensland Museum, PO Box 3300, South Brisbane, Queensland 4101, Australia; Jonathan M. Adrain, Department of Geoscience, 121 Trowbridge Hall, Univ- ersity of Iowa, Iowa City, Iowa 52242, USA; 1 August 2002. p Trilobites, generic names, checklist. Trilobite fossils attracted the attention of could find. This list was copied on an early spirit humans in different parts of the world from the stencil machine to some 20 or more trilobite very beginning, probably even prehistoric times. workers around the world, principally those who In the 1700s various European natural historians would author the 1959 Treatise edition. Weller began systematic study of living and fossil also drew on this compilation for his Presidential organisms including trilobites.
    [Show full text]
  • 001-012 Primeras Páginas
    PUBLICACIONES DEL INSTITUTO GEOLÓGICO Y MINERO DE ESPAÑA Serie: CUADERNOS DEL MUSEO GEOMINERO. Nº 9 ADVANCES IN TRILOBITE RESEARCH ADVANCES IN TRILOBITE RESEARCH IN ADVANCES ADVANCES IN TRILOBITE RESEARCH IN ADVANCES planeta tierra Editors: I. Rábano, R. Gozalo and Ciencias de la Tierra para la Sociedad D. García-Bellido 9 788478 407590 MINISTERIO MINISTERIO DE CIENCIA DE CIENCIA E INNOVACIÓN E INNOVACIÓN ADVANCES IN TRILOBITE RESEARCH Editors: I. Rábano, R. Gozalo and D. García-Bellido Instituto Geológico y Minero de España Madrid, 2008 Serie: CUADERNOS DEL MUSEO GEOMINERO, Nº 9 INTERNATIONAL TRILOBITE CONFERENCE (4. 2008. Toledo) Advances in trilobite research: Fourth International Trilobite Conference, Toledo, June,16-24, 2008 / I. Rábano, R. Gozalo and D. García-Bellido, eds.- Madrid: Instituto Geológico y Minero de España, 2008. 448 pgs; ils; 24 cm .- (Cuadernos del Museo Geominero; 9) ISBN 978-84-7840-759-0 1. Fauna trilobites. 2. Congreso. I. Instituto Geológico y Minero de España, ed. II. Rábano,I., ed. III Gozalo, R., ed. IV. García-Bellido, D., ed. 562 All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system now known or to be invented, without permission in writing from the publisher. References to this volume: It is suggested that either of the following alternatives should be used for future bibliographic references to the whole or part of this volume: Rábano, I., Gozalo, R. and García-Bellido, D. (eds.) 2008. Advances in trilobite research. Cuadernos del Museo Geominero, 9.
    [Show full text]
  • Palynology of the Iscayachi Formation (Cambro-Ordovician) from the Cordillera Oriental of Southern Bolivia: New Data from the Western Margin of Gondwana
    Geologica Acta, Vol.11, Nº 2, June 2013, 167-176 DOI: 10.1344/105.000001707 Available online at www.geologica-acta.com Palynology of the Iscayachi Formation (Cambro-Ordovician) from the Cordillera Oriental of Southern Bolivia: New data from the western margin of Gondwana M.M. VERGEL G.F. ACEÑOLAZA L. ARÁOZ INSUGEO - CONICET/Universidad Nacional de Tucumán, Facultad de Ciencias Naturales e I.M.L. Miguel Lillo 205. 4000 Tucumán. Argentina. Vergel E-mail: [email protected] ABS TRACT The first late-Cambrian aged palynomorph assemblage of Bolivia is presented. The sampled material comes from the Cambro-Ordovician Iscayachi Formation cropping out in the Antenna of the Sierra de Sama, Tarija department, southern Bolivia. The palynomorph assemblage occurs in levels correlated to the Parabolina (Neoparabolina) frequens argentina trilobite biozone. It is comprised of Acanthodiacrodium spp., Cristallinium cambriense, Cy- matiogalea cf. C. aspergillum, C. velifera, C. virgulta, Dasydiacrodium spp., Eliasum llaniscum, Impluviculus multiangularis, Ladogella rommelaerei, Ladogella sp., Leiofusa sp., Leiosphaeridia sp., Lophosphaeridium sp., Lusatia? sp., Micrhystridium sp., Poikilofusa squama, Poikilofusa sp., Polygonium dentatum, Retisphaeridium brayense, Saharidia fragilis, Solisphaeridium akrochordum, S. lucidum, Timofeevia phosphoritica, Timofeevia microretis, Vulcanisphaera africana and V. turbata. The assemblage provides elements of comparison with pre- viously reported palynofloras in northern Argentina, eastern Newfoundland, southwestern
    [Show full text]
  • Paleozoic Stratigraphy and Petroleum Systems of the Western and Southwestern Deserts of Iraq
    GeoArabia, Vol. 3, No. 2, 1998 Paleozoic Stratigraphy and Petroleum Systems, Iraq Gulf PetroLink, Bahrain Paleozoic Stratigraphy and Petroleum Systems of the Western and Southwestern Deserts of Iraq Adnan A.M. Aqrawi Smedvig Technologies ABSTRACT A stratigraphic scheme for the Paleozoic of the Southwestern Desert of Iraq is proposed based upon the review of recently published data from several deep wells in the western part of the country and from outcrops in other regions in Iraq. The main formations are described in terms of facies distribution, probable age, regional thickness, and correlations with the well-reported Paleozoic successions of the adjacent countries (e.g. Jordan and Saudi Arabia), as well as with the Thrust Zone of North Iraq. The Paleozoic depositional and tectonic evolution of the Western and Southwestern Deserts of Iraq, particularly during Cambrian, Ordovician and Silurian, shows marked similarity to those of eastern Jordan and northern Saudi Arabia. However, local lithological variations, which are due to Late Paleozoic Hercynian tectonics, characterize the Upper Paleozoic sequences. The Lower Silurian marine “hot” shale, 65 meters thick in the Akkas-1 well in the Western Desert, is believed to be the main Paleozoic source rock in the Western and Southwestern Deserts. Additional potential source rocks in this region could be the black shales of the Ordovician Khabour Formation, the Upper Devonian to Lower Carboniferous Ora Shale Formation, and the lower shaly beds of the Upper Permian Chia Zairi Formation. The main target reservoirs are of Ordovician, Silurian, Carboniferous and Permian ages. Similar reservoirs have recently been reported for the Western Desert of Iraq, eastern Jordan and northern Saudi Arabia.
    [Show full text]
  • Geoforensics Laurance Donnelly and Alastair Ruffell on the Group’S First Decade
    SVOLUMECIENTIS 26 NO 11 ◆ DEC 16/JAN 17 ◆ WWW.GEOLSOC.ORG.UK/GEOSCIENTISTT GEThe Fellowship Magazine of theO Geological Society of London UK / Overseas where sold to individuals: £3.95 Geoforensics Laurance Donnelly and Alastair Ruffell on the Group’s first decade SOCIETY ON FACEBOOK [WWW.FACEBOOK.COM/GEOLSOC ] MENTE ET MALLEO? AFTER ABERFAN ONLINE CONFERENCING The Sedgwick’s collection You respond to our coverage Arjan Reesink weighs up the of geological hammers of the 50th anniversary new trend’s pros and cons GEOSCIENTIST CONTENTS 16 20 10 27 FEATURESFEATURES IN THIS ISSUE... 16 IF I HAD A HAMMER Douglas Palmer describes a new exhibition of the Sedgwick’s collection of famous geologists’ mighty tools. (See also Books & Arts, p22.) REGULARS 05 Welcome Ted Nield urges Trustees not to overlook an Executive Secretary’s most important duty 06 Society News What your Society is doing at home and abroad, in London and the regions 09 Soapbox Arjan Reesink sees pluses and some minuses in online conferencing 21 Letters You respond to our coverage of the Aberfan Disaster, 50 years ago ON THE COVER: 22 Books and arts Six reviews by Ted Nield, Matt Loader, Andrew 10 What lies beneath Robinson, David Edwards, Mike Bowman and Richard Wrigley Laurance Donnelly describes the 24 People Geoscientists in the news and on the move first 10 years of the Society’s 26 Calendar Society activities this month Forensic Geoscience Group 28 Obituary Norman John D’Cruz 1924-2016 29 Crossword Win a Special Publication of your choice WWW.GEOLSOC.ORG.UK/GEOSCIENTIST
    [Show full text]
  • Th TRILO the Back to the Past Museum Guide to TRILO BITES
    With regard to human interest in fossils, trilobites may rank second only to dinosaurs. Having studied trilobites most of my life, the English version of The Back to the Past Museum Guide to TRILOBITES by Enrico Bonino and Carlo Kier is a pleasant treat. I am captivated by the abundant color images of more than 600 diverse species of trilobites, mostly from the authors’ own collections. Carlo Kier The Back to the Past Museum Guide to Specimens amply represent famous trilobite localities around the world and typify forms from most of the Enrico Bonino Enrico 250-million-year history of trilobites. Numerous specimens are masterpieces of modern professional preparation. Richard A. Robison Professor Emeritus University of Kansas TRILOBITES Enrico Bonino was born in the Province of Bergamo in 1966 and received his degree in Geology from the Depart- ment of Earth Sciences at the University of Genoa. He currently lives in Belgium where he works as a cartographer specialized in the use of satellite imaging and geographic information systems (GIS). His proficiency in the use of digital-image processing, a healthy dose of artistic talent, and a good knowledge of desktop publishing software have provided him with the skills he needed to create graphics, including dozens of posters and illustrations, for all of the displays at the Back to the Past Museum in Cancún. In addition to his passion for trilobites, Enrico is particularly inter- TRILOBITES ested in the life forms that developed during the Precambrian. Carlo Kier was born in Milan in 1961. He holds a degree in law and is currently the director of the Azul Hotel chain.
    [Show full text]
  • Olenid Trilobites: the Oldest Known Chemoautotrophic Symbionts?
    Olenid trilobites: The oldest known chemoautotrophic symbionts? Richard Fortey* Department of Paleontology, Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom Communicated by Lynn Margulis, University of Massachusetts, Amherst, MA, April 3, 2000 (received for review March 1, 2000) Late Cambrian to early Ordovician trilobites, the family Olenidae, Given the widespread occurrence and taxonomic spread of were tolerant of oxygen-poor, sulfur-rich sea floor conditions, and chemoautotrophic symbiosis, it is likely to have been an ancient a case is made that they were chemoautotrophic symbionts. adaptation. Because direct evidence of the fossil bacteria seldom Olenids were uniquely adapted to this habitat in the Lower preserves, evidence of such habits tends to be inferred from Paleozoic, which was widespread in the Late Cambrian over Scan- taxonomic and͞or morphological data, which is not always dinavia. This life habit explains distinctive aspects of olenid mor- reliable (11). The long-ranging solemyid and lucinid bivalves (10) phology: wide thoraces and large numbers of thoracic segments, indicate that by the Silurian (ca. 420 million years), this life mode thin cuticle and, in some species, degenerate hypostome, and the already had been adopted by some groups with living descen- occasional development of brood pouches. Geochemical and field dants. Ancient vent associations have been recognized from at evidence is consistent with this interpretation. Olenids occupied least the Devonian (12). their specialized habitat for 60 million years until their extinction I show in this paper that even by the late Cambrian period (505 at the end of the Ordovician. million years ago) certain extinct arthropods, trilobites belonging to the family Olenidae, evolved features best understood as evidence olorless sulfur bacteria, a heterogeneous category of bacte- of sulfur chemoautotrophic mode of metabolism.
    [Show full text]
  • Cambrian Stratigraphy and Depositional Dynamics Based on the Tomten-1 Drill Core, Falbygden, Västergötland, Sweden
    Cambrian stratigraphy and depositional dynamics based on the Tomten-1 drill core, Falbygden, Västergötland, Sweden Frans Lundberg Dissertations in Geology at Lund University, Master’s thesis, no 462 (45 hp/ECTS credits) Department of Geology Lund University 2016 Cambrian stratigraphy and depositional dynamics based on the Tomten-1 drill core, Falbygden, Västergötland, Sweden Master’s thesis Frans Lundberg Department of Geology Lund University 2016 Contents 1 Introduction ........................................................................................................................................................ 7 2 Location and general remarks .......................................................................................................................... 7 3 Material and methods ........................................................................................................................................ 8 3.1 Lithology and facies 8 3.2 Fossil content and biostratigraphy 8 3.3 Acid resistant microfossils 10 3.4 Chemostratigraphy 10 4 Lithostratigraphy ............................................................................................................................................. 11 3.1 Lingulid Sandstone Member, File Haidar Formation (29.85−26.43 m) 11 4.2 Kvarntorp Member, Borgholm Formation (26.43−25.70 m) 11 4.3 Alum Shale Formation (25.70−1.55 m) 12 4.3.1 Alum Shale 12 4.3.2 Limestone 13 4.4 Bjørkåsholmen Formation (1.55−1.53 m) 15 4.5 Latorp Limestone (1.53−1.10 m) 15 4.6 Lanna Limestone (1.10−0
    [Show full text]
  • Ordovician Stratigraphy and Benthic Community Replacements in the Eastern Anti-Atlas, Morocco J
    Ordovician stratigraphy and benthic community replacements in the eastern Anti-Atlas, Morocco J. Javier Alvaro, Mohammed Benharref, Jacques Destombes, Juan Carlos Gutiérrez-Marco, Aaron Hunter, Bertrand Lefebvre, Peter van Roy, Samuel Zamora To cite this version: J. Javier Alvaro, Mohammed Benharref, Jacques Destombes, Juan Carlos Gutiérrez-Marco, Aaron Hunter, et al.. Ordovician stratigraphy and benthic community replacements in the eastern Anti- Atlas, Morocco. The Great Ordovician Biodiversification Event: Insights from the Tafilalt Biota, Morocco, 485, The Geological Society of London, pp.SP485.20, In press, Geological Society, London, Special Publication, 10.1144/SP485.20. hal-02405970 HAL Id: hal-02405970 https://hal.archives-ouvertes.fr/hal-02405970 Submitted on 13 Nov 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. The Geological Society Special Publications Ordovician stratigraphy and benthic community replacements in the eastern Anti-Atlas, Morocco --Manuscript Draft-- Manuscript Number: GSLSpecPub2019-17R1 Article Type: Research article Full Title: Ordovician stratigraphy and benthic community replacements in the eastern Anti-Atlas, Morocco Short Title: Ordovician stratigraphy of the Anti-Atlas Corresponding Author: Javier Alvaro Instituto de Geociencias SPAIN Corresponding Author E-Mail: [email protected] Other Authors: MOHAMMED BENHARREF JACQUES DESTOMBES JUAN CARLOS GUTIÉRREZ-MARCO AARON W.
    [Show full text]
  • The Upper Ordovician Glaciation in Sw Libya – a Subsurface Perspective
    J.C. Gutiérrez-Marco, I. Rábano and D. García-Bellido (eds.), Ordovician of the World. Cuadernos del Museo Geominero, 14. Instituto Geológico y Minero de España, Madrid. ISBN 978-84-7840-857-3 © Instituto Geológico y Minero de España 2011 ICE IN THE SAHARA: THE UPPER ORDOVICIAN GLACIATION IN SW LIBYA – A SUBSURFACE PERSPECTIVE N.D. McDougall1 and R. Gruenwald2 1 Repsol Exploración, Paseo de la Castellana 280, 28046 Madrid, Spain. [email protected] 2 REMSA, Dhat El-Imad Complex, Tower 3, Floor 9, Tripoli, Libya. Keywords: Ordovician, Libya, glaciation, Mamuniyat, Melaz Shugran, Hirnantian. INTRODUCTION An Upper Ordovician glacial episode is widely recognized as a significant event in the geological history of the Lower Paleozoic. This is especially so in the case of the Saharan Platform where Upper Ordovician sediments are well developed and represent a major target for hydrocarbon exploration. This paper is a brief summary of the results of fieldwork, in outcrops across SW Libya, together with the analysis of cores, hundreds of well logs (including many high quality image logs) and seismic lines focused on the uppermost Ordovician of the Murzuq Basin. STRATIGRAPHIC FRAMEWORK The uppermost Ordovician section is the youngest of three major sequences recognized widely across the entire Saharan Platform: Sequence CO1: Unconformably overlies the Precambrian or Infracambrian basement. It comprises the possible Upper Cambrian to Lowermost Ordovician Hassaouna Formation. Sequence CO2: Truncates CO1 along a low angle, Type II unconformity. It comprises the laterally extensive and distinctive Lower Ordovician (Tremadocian-Floian?) Achebayat Formation overlain, along a probable transgressive surface of erosion, by interbedded burrowed sandstones, cross-bedded channel-fill sandstones and mudstones of Middle Ordovician age (Dapingian-Sandbian), known as the Hawaz Formation, and interpreted as shallow-marine sediments deposited within a megaestuary or gulf.
    [Show full text]