DOCSLIB.ORG

Chapter 18. the Ediacaran Period

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chapter 18. the Ediacaran Period S.H. Xiao and G.M. Narbonne Chapter 18 The Ediacaran Period 600 Ma Ediacaran 1800 Ediacaran CR Scotese, PALEOMAP Project Chapter outline 18.1 Historical background 522 18.3.4 Chemical evolution of Ediacaran oceans 537 18.2 Cap dolostones and the base of the Ediacaran System 525 18.3.5 Radioisotopic dating 543 18.3 The biostratigraphic basis for the Ediacaran System 526 18.4 Toward an Ediacaran chronostratigraphy 544 18.3.1 Ediacaran megafossils and trace fossils 526 Acknowledgments 547 18.3.2 Ediacaran microfossils 535 References 547 18.3.3 Ediacaran glaciations 537 Abstract founded on a holistic approach integrating biostratigraphic, che- The Ediacaran Period (635À538 Ma) has the longest duration mostratigraphic, paleoclimatic and geochronometric data, particu- among all stratigraphically defined geological periods. The basal larly carbon and strontium isotopes, glacial diamictites, boundary of the Ediacaran System is defined by a horizon near acanthomorphic acritarchs, Ediacara-type megafossils, and certain the base of the Nuccaleena Formation overlying the Cryogenian tubular fossils. Our preferred scheme is to divide the Ediacaran diamictite of the Elatina Formation at the Enorama Creek section System into two series separated by the 580 Ma Gaskiers glaciation. Stage-level subdivisions at the bottom and top of the in South Australia. Most Ediacaran fossils represent soft-bodied Ediacaran System, including the definition of the second organisms and their preservation is affected by taphonomic biases. Ediacaran stage (SES) and the terminal Ediacaran stage (TES), are Thus the Phanerozoic approach of defining stratigraphic bound- feasible in the near future. Additional Ediacaran stages between aries using the first appearance datum of widely distributed, rap- the SES and TES can be envisioned, but formal definition of these idly evolving, easily recognizable, and readily preservable species stages are not possible until various stratigraphic markers are thor- would have limited success in the Ediacaran System. The subdivi- oughly tested and calibrated at both regional and global scales. sion and correlation of the Ediacaran System must therefore be Geologic Time Scale 2020. DOI: https://doi.org/10.1016/B978-0-12-824360-2.00018-8 © 2020 Elsevier B.V. All rights reserved. 521 522 PART | III Geologic Periods: Planetary and Precambrian 18.1 Historical background The designation of the Ediacaran Period reflected the gradual solution of a problem that had vexed even The basal boundary of the Ediacaran System was ratified Darwin (1859) in his writing of “The Origin of Species,” in 2004 (Knoll et al., 2004, 2006), with its GSSP (Global the apparently abrupt appearance of diverse groups of Boundary Stratotype Section and Point) defined by a hori- shelly fossils at the base of the Cambrian System without zon near the base of the Nuccaleena Formation overlying any obvious Precambrian ancestors. Darwin attributed this the Cryogenian diamictite of the Elatina Formation at the absence to massive record failure, a view formalized by Enorama Creek section in South Australia (Fig. 18.1). Walcott (1914) in his designation of the “Lipalian Base of the Ediacaran System at Enorama Creek, Flinders Ranges, South Australia N Parachilna Acraman impact ejecta Australia Blinman N GSSP Ediacara siltstone GSSP Mbr Wilpena trough Chace crossbed Hawker Mbr sandstone Rownsley Quartzite Rownsley Bonny sandstone Port Augusta Sandstone diamictite 1000 m 1000 silty Wonoka limestone cap Ediacaran dolostone Bunyeroo AIE Top of cap carbonate ABC 6 5 Adelaide 4 3 Brachina 2 0 100km (A) 1 -3 -2 -1 stratigraphic height (m) 13 o Nuccaleena GSSP δ C /oo Elatina (B) Nuccaleena Cry. Formation 20 cm Teepee-structure, Nuccaleena Formation 0 cm GSSP Elatina Formation (C) (D) FIGURE 18.1 GSSP for base of the Ediacaran at Enorama Creek section, central Flinders Ranges, Adelaide Rift Complex, South Australia. (A) Map showing location of the GSSP. (B) Generalized stratigraphic column showing the GSSP level, which is defined as the sharp base of the cap car- bonate (Nuccaleena Formation) overlying the Marinoan glacial and glaciomarine diamictite deposits (Elatina Formation). Carbonate carbon isotopevalues in the cap carbonate are negative and decrease upsection in the cap dolostone. (C) Field photograph showing the exact location of the GSSP. (D) Enigmatic teepee-like structures, up to 1 m in amplitude, in the Nuccaleena cap dolostone. GSSP, Global Boundary Stratotype Section and Point. (A) Modified from Ogg et al. (2016); (B) Modified from Knoll et al. (2006) and Xiao et al. (2013). (C) Photograph by S. Xiao. (D) Photo courtesy Gabi Ogg. The Ediacaran Period Chapter | 18 523 Interval” of erosion beneath the base of the Cambrian. of an Ediacarian/Ediacaran System as the terminal The concept of a global period of erosion prior to the Neoproterozoic chronostratigraphic interval has evolved, Cambrian was soon contradicted by discovery of thick although Ediacara-type megafossils as a key symbol of successions of largely unmetamorphosed strata concor- this interval have remained the same. What has evolved is dantly beneath the base of the Cambrian in numerous the basal boundary age and the duration of the Ediacaran localities worldwide, most notably the “Sinian” in China System (Fig. 18.2). Jenkins (1981) formally proposed the (Grabau, 1922; Lee, 1924), the “Marinoan” in Australia Ediacaran System and placed its basal boundary at the (Mawson and Sprigg, 1950), and the “Vendian” in Russia base of the Wonoka Formation at Bunyeroo Gorge in (Sokolov, 1952). These names were originally proposed South Australia. The basal boundary of Jenkins’ (1981) as regional lithostratigraphic units that later assumed a Ediacaran System is thus stratigraphically higher than the chronostratigraphic significance, but scarcity of reliable GSSP of the Ediacaran System as currently defined radioisotopic dates and a lack of consistent criteria for (Fig. 18.1) and corresponds to the sequence boundary correlation frustrated early attempts to extend these divi- underlying the oldest unequivocal Ediacara-type fossils in sions globally. Australia. Lacking any robust geochronological data, Subsequent paleontological research confirmed Darwin’s Jenkins (1981) estimated that his Ediacaran System began view that there was abundant life before the beginning or at B640 Ma. Independent of Jenkins (1981), Cloud and the Cambrian but showed that most Precambrian organisms Glaessner (1982) formalized the Ediacarian System, with were soft-bodied and many were also microscopic. Perhaps most distinctive among these organisms were Ediacara-type megafossils, best seen in the Ediacara Hills of South Australia, which gives its name to the Ediacaran Period. 2012 2004 These are centimeter- to meter-scale impressions of soft- 540 Ma Narbonne et al. Robb et al. bodied organisms that typically were preserved as impres- 1982 sions at the bases of event beds of sand or volcanic ash Cloud & Glaessner 550 Ma (Narbonne, 2005; Fedonkin et al., 2007). They were first described in the late 19th century (Billings, 1872)butfew paleontologists at that time were willing to accept the wide- 560 Ma spread occurrence of megascopic Precambrian life, and Jenkins, 1981 even the complex Ediacaran fossils reported from Namibia 570 Ma 1990 Harland et al., 1991 Plumb, and Australia in the 1930s and 1940s were tentatively regarded as “Cambrian” by their discoverers (Gu¨rich, 1930, 580 Ma 1933; Sprigg, 1947). Ford’s (1958) description of the frond Ediacaran Series Charnia from unequivocally Precambrian strata in central 590 Ma 1982 Harland et al., Ediacaran System England led Glaessner (1959) to propose a global “Ediacara Ediacaran System Fauna” of large, soft-bodied animal-like fossils that immedi- System Vendian 600 Ma ately preceded the Cambrian, a concept that exists to the Sinian Erathem present day and has proven instrumental in subsequent rec- Varangian Series Varangian ognition of a terminal Proterozoic System. The discovery of 610 Ma Ediacarian System Ediacaran System Ediacaran abundant and diverse microfossils, particularly acantho- III Neoproterozoic morphic acritarchs, has also significantly enhanced the pro- 620 Ma Ediacaran Series spects for Ediacaran biostratigraphy. This area of research Sinian Erathem was first pioneered by Russian and later Chinese micro- 630 Ma paleontologists (Timofeev, 1966; Yin and Li, 1978; Vendian System Vendian Jankauskas et al., 1989), and some of Ediacaran acantho- 640 Ma Sinian Erathem morphs have been shown to have restricted time ranges Sturtian System and a global distribution (Zang and Walter, 1992; Mortensnes Epoch 650 Ma Moczydłowska et al., 1993; Zhang et al., 1998; Grey, 2005; Vorob’eva et al., 2009b; Moczydłowska and 660 Ma Cryogenian System Cryogenian System Nagovitsin, 2012; Liu et al., 2014f; Xiao et al., 2014b). Series Varangian A year after Glaessner’s recognition of a global 670 Ma Epoch Smalfjord Ediacaran macrofossil assemblage below the Cambrian, Sturtian Termier and Termier (1960) proposed the “Ediacarien” as System Cryogenian System Precambrian chronostratigraphic interval characterized by FIGURE 18.2 Evolution of the concept of Ediacaran/Ediacarian this distinctive fossil assemblage. Since then, the concept System or Series. 524 PART | III Geologic Periods: Planetary and Precambrian its lower boundary defined at the base of the Nuccaleena Working Group (later Subcommission) on the Terminal Formation in the Bunyeroo Gorge in South Australia, and Proterozoic Period at the IGC in Washington,
Load more

Recommended publications
  • Ediacaran Developmental Biology
    Dunn, F., Liu, A., & Donoghue, P. (2017). Ediacaran developmental biology. Biological Reviews. https://doi.org/10.1111/brv.12379 Publisher's PDF, also known as Version of record License (if available): CC BY Link to published version (if available): 10.1111/brv.12379 Link to publication record in Explore Bristol Research PDF-document University of Bristol - Explore Bristol Research General rights This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/red/research-policy/pure/user-guides/ebr-terms/ Biol. Rev. (2017), pp. 000–000. 1 doi: 10.1111/brv.12379 Ediacaran developmental biology Frances S. Dunn1,2,∗, Alexander G. Liu1,† and Philip C. J. Donoghue1 1School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, U.K. 2British Geological Survey, Nicker Hill, Keyworth, Nottingham, NG12 5GG, U.K. ABSTRACT Rocks of the Ediacaran System (635–541 Ma) preserve fossil evidence of some of the earliest complex macroscopic organisms, many of which have been interpreted as animals. However, the unusual morphologies of some of these organisms have made it difficult to resolve their biological relationships to modern metazoan groups. Alternative competing phylogenetic interpretations have been proposed for Ediacaran taxa, including algae, fungi, lichens, rhizoid protists, and even an extinct higher-order group (Vendobionta). If a metazoan affinity can be demonstrated for these organisms, as advocated by many researchers, they could prove informative in debates concerning the evolution of the metazoan body axis, the making and breaking of axial symmetries, and the appearance of a metameric body plan.
    [Show full text]
  • The Ediacaran Frondose Fossil Arborea from the Shibantan Limestone of South China
    Journal of Paleontology, 94(6), 2020, p. 1034–1050 Copyright © 2020, The Paleontological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/ licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. 0022-3360/20/1937-2337 doi: 10.1017/jpa.2020.43 The Ediacaran frondose fossil Arborea from the Shibantan limestone of South China Xiaopeng Wang,1,3 Ke Pang,1,4* Zhe Chen,1,4* Bin Wan,1,4 Shuhai Xiao,2 Chuanming Zhou,1,4 and Xunlai Yuan1,4,5 1State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, China <[email protected]><[email protected]> <[email protected]><[email protected]><[email protected]><[email protected]> 2Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA <[email protected]> 3University of Science and Technology of China, Hefei 230026, China 4University of Chinese Academy of Sciences, Beijing 100049, China 5Center for Research and Education on Biological Evolution and Environment, Nanjing University, Nanjing 210023, China Abstract.—Bituminous limestone of the Ediacaran Shibantan Member of the Dengying Formation (551–539 Ma) in the Yangtze Gorges area contains a rare carbonate-hosted Ediacara-type macrofossil assemblage. This assemblage is domi- nated by the tubular fossil Wutubus Chen et al., 2014 and discoidal fossils, e.g., Hiemalora Fedonkin, 1982 and Aspidella Billings, 1872, but frondose organisms such as Charnia Ford, 1958, Rangea Gürich, 1929, and Arborea Glaessner and Wade, 1966 are also present.
    [Show full text]
  • Download Download
    Dorjnamjaa et al. Mongolian Geoscientist 49 (2019) 41-49 https://doi.org/10.5564/mgs.v0i49.1226 Mongolian Geoscientist Review paper New scientific direction of the bacterial paleontology in Mongolia: an essence of investigation * Dorj Dorjnamjaa , Gundsambuu Altanshagai, Batkhuyag Enkhbaatar Department of Paleontology, Institute of Paleontology, Mongolian Academy of Sciences, Ulaanbaatar 15160, Mongolia *Corresponding author. Email: [email protected] ARTICLE INFO ABSTRACT Article history: We review the initial development of Bacterial Paleontology in Mongolia and Received 10 September 2019 present some electron microscopic images of fossil bacteria in different stages of Accepted 9 October 2019 preservation in sedimentary rocks. Indeed bacterial paleontology is one the youngest branches of paleontology. It has began in the end of 20th century and has developed rapidly in recent years. The main tasks of bacterial paleontology are detailed investigation of fossil microorganisms, in particular their morphology and sizes, conditions of burial and products of habitation that are reflected in lithological and geochemical features of rocks. Bacterial paleontology deals with fossil materials and is useful in analysis of the genesis of sedimentary rocks, and sedimentary mineral resources including oil and gas. The traditional paleontology is especially significant for evolution theory, biostratigraphy, biogeography and paleoecology; however bacterial paleontology is an essential first of all for sedimentology and for theories sedimentary ore genesis or biometallogeny Keywords: microfossils, phosphorite, sedimentary rocks, lagerstatten, biometallogeny INTRODUCTION all the microorganisms had lived and propagated Bacteria or microbes preserved well as fossils in without breakdowns. Bacterial paleontological various rocks, especially in sedimentary rocks data accompanied by the data on the first origin alike natural substances.
    [Show full text]
  • Palaeobiology of the Early Ediacaran Shuurgat Formation, Zavkhan Terrane, South-Western Mongolia
    Journal of Systematic Palaeontology ISSN: 1477-2019 (Print) 1478-0941 (Online) Journal homepage: http://www.tandfonline.com/loi/tjsp20 Palaeobiology of the early Ediacaran Shuurgat Formation, Zavkhan Terrane, south-western Mongolia Ross P. Anderson, Sean McMahon, Uyanga Bold, Francis A. Macdonald & Derek E. G. Briggs To cite this article: Ross P. Anderson, Sean McMahon, Uyanga Bold, Francis A. Macdonald & Derek E. G. Briggs (2016): Palaeobiology of the early Ediacaran Shuurgat Formation, Zavkhan Terrane, south-western Mongolia, Journal of Systematic Palaeontology, DOI: 10.1080/14772019.2016.1259272 To link to this article: http://dx.doi.org/10.1080/14772019.2016.1259272 Published online: 20 Dec 2016. Submit your article to this journal Article views: 48 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tjsp20 Download by: [Harvard Library] Date: 31 January 2017, At: 11:48 Journal of Systematic Palaeontology, 2016 http://dx.doi.org/10.1080/14772019.2016.1259272 Palaeobiology of the early Ediacaran Shuurgat Formation, Zavkhan Terrane, south-western Mongolia Ross P. Anderson a*,SeanMcMahona,UyangaBoldb, Francis A. Macdonaldc and Derek E. G. Briggsa,d aDepartment of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, Connecticut, 06511, USA; bDepartment of Earth Science and Astronomy, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902, Japan; cDepartment of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts, 02138, USA; dPeabody Museum of Natural History, Yale University, 170 Whitney Avenue, New Haven, Connecticut, 06511, USA (Received 4 June 2016; accepted 27 September 2016) Early diagenetic chert nodules and small phosphatic clasts in carbonates from the early Ediacaran Shuurgat Formation on the Zavkhan Terrane of south-western Mongolia preserve diverse microfossil communities.
    [Show full text]
  • Tetrapod Biostratigraphy and Biochronology of the Triassic–Jurassic Transition on the Southern Colorado Plateau, USA
    Palaeogeography, Palaeoclimatology, Palaeoecology 244 (2007) 242–256 www.elsevier.com/locate/palaeo Tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau, USA Spencer G. Lucas a,⁎, Lawrence H. Tanner b a New Mexico Museum of Natural History, 1801 Mountain Rd. N.W., Albuquerque, NM 87104-1375, USA b Department of Biology, Le Moyne College, 1419 Salt Springs Road, Syracuse, NY 13214, USA Received 15 March 2006; accepted 20 June 2006 Abstract Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups on the southern Colorado Plateau preserve tetrapod body fossils and footprints that are one of the world's most extensive tetrapod fossil records across the Triassic– Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point and Kayenta) that we assign to the (ascending order) Revueltian, Apachean, Wassonian and Dawan land-vertebrate faunachrons (LVF). In doing so, we redefine the Wassonian and the Dawan LVFs. The Apachean–Wassonian boundary approximates the Triassic–Jurassic boundary. This tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau confirms that crurotarsan extinction closely corresponds to the end of the Triassic, and that a dramatic increase in dinosaur diversity, abundance and body size preceded the end of the Triassic. © 2006 Elsevier B.V. All rights reserved. Keywords: Triassic–Jurassic boundary; Colorado Plateau; Chinle Group; Glen Canyon Group; Tetrapod 1. Introduction 190 Ma. On the southern Colorado Plateau, the Triassic– Jurassic transition was a time of significant changes in the The Four Corners (common boundary of Utah, composition of the terrestrial vertebrate (tetrapod) fauna.
    [Show full text]
  • Lessons from the Fossil Record: the Ediacaran Radiation, the Cambrian Radiation, and the End-Permian Mass Extinction
    OUP CORRECTED PROOF – FINAL, 06/21/12, SPi CHAPTER 5 Lessons from the fossil record: the Ediacaran radiation, the Cambrian radiation, and the end-Permian mass extinction S tephen Q . D ornbos, M atthew E . C lapham, M argaret L . F raiser, and M arc L afl amme 5.1 Introduction and altering substrate consistency ( Thayer 1979 ; Seilacher and Pfl üger 1994 ). In addition, burrowing Ecologists studying modern communities and eco- organisms play a crucial role in modifying decom- systems are well aware of the relationship between position and enhancing nutrient cycling ( Solan et al. biodiversity and aspects of ecosystem functioning 2008 ). such as productivity (e.g. Tilman 1982 ; Rosenzweig Increased species richness often enhances ecosys- and Abramsky 1993 ; Mittelbach et al. 2001 ; Chase tem functioning, but a simple increase in diversity and Leibold 2002 ; Worm et al. 2002 ), but the pre- may not be the actual underlying driving mecha- dominant directionality of that relationship, nism; instead an increase in functional diversity, the whether biodiversity is a consequence of productiv- number of ecological roles present in a community, ity or vice versa, is a matter of debate ( Aarssen 1997 ; may be the proximal cause of enhanced functioning Tilman et al. 1997 ; Worm and Duffy 2003 ; van ( Tilman et al. 1997 ; Naeem 2002 ; Petchey and Gaston, Ruijven and Berendse 2005 ). Increased species rich- 2002 ). The relationship between species richness ness could result in increased productivity through (diversity) and functional diversity has important 1) interspecies facilitation and complementary implications for ecosystem functioning during resource use, 2) sampling effects such as a greater times of diversity loss, such as mass extinctions, chance of including a highly productive species in a because species with overlapping ecological roles diverse assemblage, or 3) a combination of biologi- can provide functional redundancy to maintain cal and stochastic factors ( Tilman et al.
    [Show full text]
  • Geobiological Events in the Ediacaran Period
    Geobiological Events in the Ediacaran Period Shuhai Xiao Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA NSF; NASA; PRF; NSFC; Virginia Tech Geobiology Group; CAS; UNLV; UCR; ASU; UMD; Amherst; Subcommission of Neoproterozoic Stratigraphy; 1 Goals To review biological (e.g., acanthomorphic acritarchs; animals; rangeomorphs; biomineralizing animals), chemical (e.g., carbon and sulfur isotopes, oxygenation of deep oceans), and climatic (e.g., glaciations) events in the Ediacaran Period; To discuss integration and future directions in Ediacaran geobiology; 2 Knoll and Walter, 1992 • Acanthomorphic acritarchs in early and Ediacara fauna in late Ediacaran Period; • Strong carbon isotope variations; • Varanger-Laplandian glaciation; • What has happened since 1992? 3 Age Constraints: South China (538.2±1.5 Ma) 541 Ma Cambrian Dengying Ediacaran Sinian 551.1±0.7 Ma Doushantuo 632.5±0.5 Ma 635 Ma 635.2±0.6 Ma Nantuo (Tillite) 636 ± 5Ma Cryogenian Nanhuan 654 ± 4Ma Datangpo 663±4 Ma Neoproterozoic Neoproterozoic Jiangkou Group Banxi Group 725±10 Ma Tonian Qingbaikouan 1000 Ma • South China radiometric ages: Condon et al., 2005; Hoffmann et al., 2004; Zhou et al., 2004; Bowring et al., 2007; S. Zhang et al., 2008; Q. Zhang et al., 2008; • Additional ages from Nama Group (Namibia), Conception Group (Newfoundland), and Vendian (White Sea); 4 The Ediacaran Period Ediacara fossils Cambrian 545 Ma Nama assemblage 555 Ma White Sea assemblage 565 Ma Avalon assemblage 575 Ma 585 Ma Doushantuo biota 595 Ma 605 Ma Ediacaran Period 615 Ma
    [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]
  • The Ediacaran–Cambrian Transition: the Emerging Record from Small Carbonaceous Fossils (Scfs)
    38 The Ediacaran–Cambrian transition: the emerging record from Small Carbonaceous Fossils (SCFs) Ben J. Slater1, Thomas H.P. Harvey2, Romain Guilbaud3, Sebastian Willman1, Graham E. Budd1, Nicholas J. Butterfield4. 1Department of Earth Sciences (Palaeobiology), Uppsala University, Villavägen 16, SE-75236 Uppsala, Sweden ([email protected]) 2School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK 3Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK. 4Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK Abstract.––The most profound change in the fossil record is centered on the Ediacaran–Cambrian transition. Sediments deposited near to this boundary record the first complex trace fossils, the first animal biomineralizers and the earliest fossils of the major animal groups that came to define the subsequent Phanerozoic fossil record. Here we discuss how the emerging record of small carbonaceous fossils (SCFs) is shedding new light on unmineralized aspects of the biota from this critical evolutionary transition. The new SCFs record complements currently established records from trace fossils and biomineralized shelly-remains in reconstructing the broader scale macroevolutionary patterns of this transition, but via an entirely different taphonomic window. SCFs extend the record of multiple major animal groups, improve our picture of protistan diversity from this interval, and reveal new data on elements of the biota that span the Ediacaran–Cambrian boundary. Key words: small carbonaceous fossils; bilateria; Burgess Shale-type preservation; Ediacaran; Terreneuvian. The dramatic changes in the fossil record across subsequent Cambrian radiation (Butterfield, the Ediacaran–Cambrian transition seemingly 2003; Slater et al., 2018a).
    [Show full text]
  • What Came Before the Cambrian Explosion
    What Came Before the Cambrian? Advanced Reading The Cambrian Explosion was an era of significant evolution of animal life. What came before the Cambrian era that, in a sense, opened the door for the new body forms to evolve? The geologic era before the Cambrian was called the Ediacran, lasting from about 635 to 542 million years ago. Scientists often characterize this era as an “experimental” phase in the evolution of animals. By this time unicellular life had been around for millions of years and a mat of microbes covered parts of the seafloor. The first multicellular animals that evolved could have grazed on those microbes. The fossils from the Ediacran mostly show soft-bodied organisms. Some of these fossils look like fronds, discs and blobs, and aren’t easy to identify. Others seem to be related to Cnidarians or to be soft-bodied relatives of arthropods or perhaps Echinoderms. In addition, there are trace fossils, probably made by worm-like creatures. Many of the fossil animals remain mysterious and may represent lines of animals that no longer exist. But fossils are not the only evidence of animal life in the Ediacran. In fact the first evidence of sponges is not a body fossil but rather a biochemical fossil. When an animal dies, some of its molecules break down into a stable form that can last in rocks for millions of years just like body fossils. These are biochemical fossils. Scientists have found an Ediacran biochemical fossil of a fat molecule found today only in sponges. The name Ediacran comes from the Ediacra Hills of South Australia, the most famous location of these fossils.
    [Show full text]
  • E:\Published Issues\Episodes\20
    540 by Shuhai Xiao1, Guy M. Narbonne2, Chuanming Zhou3, Marc Laflamme4, Dmitriy V. Grazhdankin5, Malgorzata Moczydlowska-Vidal6, Huan Cui7 Towards an Ediacaran Time Scale: Problems, Protocols, and Prospects 1 Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA. E-mail: [email protected] 2 Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario K7L 3N6, Canada 3 Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China 4 University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, Ontario L5L 1C6, Canada 5 Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, prospekt Akademika Koptyuga 3, Novosibirsk 630090, Russia 6 Department of Earth Sciences, Uppsala University, Villavägen 16, SE 752 36 Uppsala, Sweden 7 Department of Geoscience and NASA Astrobiology Institute, University of Wisconsin, Madison, Wisconsin 53706, USA (Received: 23/12/2015; Accepted: 4/9/2016) DOI:10.18814/epiiugs/2016/v39i4/103886 The Ediacaran Period follows the Cryogenian data to constrain the age, duration, and global extent of Period in the wake of a snowball Earth glaciation and the Shuram negative δ13C excursion, to calibrate and precedes the Cambrian Period with its rising tide of correlate Ediacaran acanthomorph biozones, and to animal radiation. It is also the longest among all determine the temporal relationship among the Shuram stratigraphically
    [Show full text]
  • The Ediacaran Frondose Fossil Arborea from the Shibantan Limestone of South China
    Journal of Paleontology, 94(6), 2020, p. 1034–1050 Copyright © 2020, The Paleontological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/ licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. 0022-3360/20/1937-2337 doi: 10.1017/jpa.2020.43 The Ediacaran frondose fossil Arborea from the Shibantan limestone of South China Xiaopeng Wang,1,3 Ke Pang,1,4* Zhe Chen,1,4* Bin Wan,1,4 Shuhai Xiao,2 Chuanming Zhou,1,4 and Xunlai Yuan1,4,5 1State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing 210008, China <[email protected]><[email protected]> <[email protected]><[email protected]><[email protected]><[email protected]> 2Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA <[email protected]> 3University of Science and Technology of China, Hefei 230026, China 4University of Chinese Academy of Sciences, Beijing 100049, China 5Center for Research and Education on Biological Evolution and Environment, Nanjing University, Nanjing 210023, China Abstract.—Bituminous limestone of the Ediacaran Shibantan Member of the Dengying Formation (551–539 Ma) in the Yangtze Gorges area contains a rare carbonate-hosted Ediacara-type macrofossil assemblage. This assemblage is domi- nated by the tubular fossil Wutubus Chen et al., 2014 and discoidal fossils, e.g., Hiemalora Fedonkin, 1982 and Aspidella Billings, 1872, but frondose organisms such as Charnia Ford, 1958, Rangea Gürich, 1929, and Arborea Glaessner and Wade, 1966 are also present.
    [Show full text]