Multiple Branching and Attachment Structures in Cloudinomorphs
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A Revised Morphology of Cloudina with Ecological and Phylogenetic Implications Andrew J
A Revised Morphology of Cloudina with Ecological and Phylogenetic Implications Andrew J. Miller Departments of Earth and Planetary Sciences and of History Harvard University, Cambridge, MA 02138 [email protected] Abstract The conventional view of the Ediacaran index fossil Cloudina, as proposed by Grant (1990), depicts the shell structure as a series of nested test tubes. A digital serial-reconstruction of Cloudina and examination of thin sections indicates that only the bottom-most tube has a bottom and that the shell wall structure is not as well defined as previously thought. The conventional ecological reconstruction, as proposed by Seilacher (1999), puts Cloudina in a microbial mat framework. Evidence from fossils in situ and from the shape of Cloudina suggests that this interpretation is incorrect. Rather, I propose that Cloudina lived on seaweeds in the reef environment. I also introduce a new mode of inference in determining shell orientation based on gravitational forces. Given the morphological evidence, Cloudina appears to be more similar to pogonophoran or annelid worms and less similar than previously thought to cnidarian corals. Introduction Life in the Precambrian is seen by many in a Hobbesian view—sessile, benthic, and short. While this may accurately describe the functional behavior of Ediacaran communities, it overlooks the significant metazoan diversity that was present there, for within the Ediacaran period the first metazoans entered the fossil record and diversified. Even though the presence of metazoans in the Ediacaran has been known for over thirty years, relatively little is known about their phylogenic affinities, their structure, and their role in the ecosystem. -
1 Revision 2 1 K-Bentonites
1 Revision 2 2 K-Bentonites: A Review 3 Warren D. Huff 4 Department of Geology, University of Cincinnati, Cincinnati, OH 45221 USA 5 Email: [email protected] 6 Keywords: K-bentonite, bentonite, tephra, explosive volcanism, volcanic ash 7 Abstract 8 Pyroclastic material in the form of altered volcanic ash or tephra has been reported and described 9 from one or more stratigraphic units from the Proterozoic to the Tertiary. This altered tephra, 10 variously called bentonite or K-bentonite or tonstein depending on the degree of alteration and 11 chemical composition, is often linked to large explosive volcanic eruptions that have occurred 12 repeatedly in the past. K-bentonite and bentonite layers are the key components of a larger group of 13 altered tephras that are useful for stratigraphic correlation and for interpreting the geodynamic 14 evolution of our planet. Bentonites generally form by diagenetic or hydrothermal alteration under 15 the influence of fluids with high Mg content and that leach alkali elements. Smectite composition is 16 partly controlled by parent rock chemistry. Studies have shown that K-bentonites often display 17 variations in layer charge and mixed-layer clay ratios and that these correlate with physical 18 properties and diagenetic history. The following is a review of known K-bentonite and related 19 occurrences of altered tephra throughout the time scale from Precambrian to Cenozoic. 20 Introduction 21 Volcanic eruptions are often, although by no means always, associated with a profuse output 22 of fine pyroclastic material, tephra. Tephra is a term used to describe all of the solid material 23 produced from a volcano during an eruption (Thorarinsson, 1944). -
Multiscale Approach Reveals That Cloudina Aggregates Are Detritus
Multiscale approach reveals that Cloudina aggregates PNAS PLUS are detritus and not in situ reef constructions Akshay Mehraa,1 and Adam Maloofa aDepartment of Geosciences, Princeton University, Princeton, NJ 08544 Edited by Donald E. Canfield, Institute of Biology and Nordic Center for Earth Evolution, University of Southern Denmark, Odense M., Denmark, and approved January 19, 2018 (received for review November 14, 2017) The earliest metazoans capable of biomineralization appeared precluding physical separation or the use of traditional computed during the late Ediacaran Period (635–541 Ma) in strata associ- tomography (CT) techniques. The inability to produce in situ ated with shallow water microbial reefs. It has been suggested 3D reconstructions has led researchers to make measurements that some Ediacaran microbial reefs were dominated (and possi- of Cloudina individuals and aggregates on polished slabs, thin bly built) by an abundant and globally distributed tubular organ- sections, and bedding planes (3, 4, 7). Unfortunately, as noted ism known as Cloudina. If true, this interpretation implies that by previous researchers, 3D spatial and size distributions can- metazoan framework reef building—a complex behavior that is not be estimated from 2D cross-sections (12). Furthermore, syn- responsible for some of the largest bioconstructions and most thetic experiments reveal that, in the case of tubular structures diverse environments in modern oceans—emerged much earlier such as Cloudina, it is not possible to correctly infer orienta- than previously thought. Here, we present 3D reconstructions of tion from 2D cross-sections (Fig. 1 A–C), and diameter measure- Cloudina populations, produced using an automated serial grind- ments made on cross-sections through curved and/or elliptical ing and imaging system coupled with a recently developed neural tubes are subject to a large degree of error (as great as 35%; Fig. -
Review of the Mineralogy of Calcifying Sponges
Dickinson College Dickinson Scholar Faculty and Staff Publications By Year Faculty and Staff Publications 12-2013 Not All Sponges Will Thrive in a High-CO2 Ocean: Review of the Mineralogy of Calcifying Sponges Abigail M. Smith Jade Berman Marcus M. Key, Jr. Dickinson College David J. Winter Follow this and additional works at: https://scholar.dickinson.edu/faculty_publications Part of the Paleontology Commons Recommended Citation Smith, Abigail M.; Berman, Jade; Key,, Marcus M. Jr.; and Winter, David J., "Not All Sponges Will Thrive in a High-CO2 Ocean: Review of the Mineralogy of Calcifying Sponges" (2013). Dickinson College Faculty Publications. Paper 338. https://scholar.dickinson.edu/faculty_publications/338 This article is brought to you for free and open access by Dickinson Scholar. It has been accepted for inclusion by an authorized administrator. For more information, please contact [email protected]. © 2013. Licensed under the Creative Commons http://creativecommons.org/licenses/by- nc-nd/4.0/ Elsevier Editorial System(tm) for Palaeogeography, Palaeoclimatology, Palaeoecology Manuscript Draft Manuscript Number: PALAEO7348R1 Title: Not all sponges will thrive in a high-CO2 ocean: Review of the mineralogy of calcifying sponges Article Type: Research Paper Keywords: sponges; Porifera; ocean acidification; calcite; aragonite; skeletal biomineralogy Corresponding Author: Dr. Abigail M Smith, PhD Corresponding Author's Institution: University of Otago First Author: Abigail M Smith, PhD Order of Authors: Abigail M Smith, PhD; Jade Berman, PhD; Marcus M Key Jr, PhD; David J Winter, PhD Abstract: Most marine sponges precipitate silicate skeletal elements, and it has been predicted that they would be among the few "winners" in an acidifying, high-CO2 ocean. -
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. -
Maritime Sediments and Atlantic Geology
Maritime Sediments and Atlantic Geology Vol. 20 APRIL, 1984 No. 1 Systematic ichnology of the Middle Ordovician Trenton Group. St. Lawrence Lowland, eastern Canada D. TjJULLon and R.H. PlcJayiAM De.pcvitmejtt o-fL Qe.o£ogy, llrviveju>-ULy o/ New Bnuru>uxick, T/iejd£JU-d.on, N.B. £38 5A3 Carbonate sediments of the upper Middle Ordovician Trenton Group between Montreal and Quebec City in the St. Lawrence Lowland, eastern Canada, contain a diverse and abundant trace fossil assemblage consisting of Arenicolites sp., ?Calycraterion sp., Chondrites spp., Circulichnis montanus, Clematis- chnia sp., ?Conostichnus sp., Cruziana problematica, Cruziana sp., cf. Diplichnites sp., Furculosus car- pathicus, Helminthopsis hieroglyphica, Helminthopsis sp., Oichnus paraboloides, Palaeophycus tubularis, Palaeophycus sp., ?Plagiogmus sp., Planolites beverleyensis, P. montanus, Planolites sp., ?Rhizocorallium cf. R. irregulare, ?Rosselia sp., Scalarituba misouriensis, Scolicia sp., Skolithos linearis, Skolithos sp., Teichichnus rectus, Teichichnus sp., Trichichnus sp., Trypanites weisei, Vermiforichnus clarkei and Zoo- phycos sp. as well as informally diagnosed loop, oblique and pronged burrows and bryozoan borings. Of these forms, only Chondrites spp., Palaeophycus tubularis, Palaeophycus sp., Planolites spp., Teichichnus spp. and Trypanites weisei are abundant; the remainder are rare to only moderately common. Neverthe- less, in this paper we describe all the trace fossils in detail and in doing so attempt to resolve several current and controversial problems of nomenclature regarding certain ichnogenera. Sediments of the Trenton Group were deposited initially in lagoons followed in turn by offshore "bar", shallow and, finally, deeper offshore shelf environments. The trace fossils do not exhibit significant variation with respect to these broad depositional regimes and, instead, each environment is character- ized by assemblages typical of the Cruziana ichnofacies as recognized in clastic sequences. -
Did Anoxia Terminate Ediacaran Benthic Communities? Evidence from Early T Diagenesis ⁎ Rachel Wooda, , Frederick Bowyera, Amelia Pennya, Simon W
Precambrian Research 313 (2018) 134–147 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres Did anoxia terminate Ediacaran benthic communities? Evidence from early T diagenesis ⁎ Rachel Wooda, , Frederick Bowyera, Amelia Pennya, Simon W. Poultonb a School of GeoSciences, University of Edinburgh, James Hutton Road, Edinburgh EH9 3FE, UK b School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK ARTICLE INFO ABSTRACT Keywords: The Ediacaran oceanic redox landscape was heterogeneous, where many basins had a shallow and highly dy- Ediacaran namic chemocline above anoxic (ferruginous or euxinic) or low oxygen (manganous) waters. Seawater mMg/Ca Redox ratio was also high, promoting early diagenetic dolomitisation. How the benthos responded to these conditions is Reefs fundamental to understanding their ecological dynamics. Here we utilise redox sensitive elements in early Early marine cements marine carbonate cements to investigate possible water column redox controls on the distribution and growth of Dolomite the oldest metazoan communities. Skeletal communities in the Zaris Sub-Basin of the Nama Group, Namibia (∼550–547 Ma), grew in shallow waters where fine-grained carbonate sediment often shows evidence of early dolomitisation. Mid-ramp Cloudina reefs are composed of open, highly porous structures that formed multiple, successive assemblages. Each as- semblage is terminated by thin (< 1 mm), layers of dolomicrite sediment and dolomite cement. All dolomitic lithologies in the Nama Group analysed via Fe speciation suggest precipitation under anoxic ferruginous water column conditions. Reef cements show a paragenetic sequence from synsedimentary to early marine cement and final burial, which we infer were precipitated under dynamic redox conditions. -
Ediacaran Metazoan Reefs from the Nama Group, Namibia
Edinburgh Research Explorer Ediacaran metazoan reefs from the Nama Group, Namibia Citation for published version: Penny, AM, Wood, R, Curtis, A, Bowyer, F, Tostevin, R & Hoffman, KH 2014, 'Ediacaran metazoan reefs from the Nama Group, Namibia', Science, vol. 344, no. 6191, pp. 1504-1506. https://doi.org/10.1126/science.1253393 Digital Object Identifier (DOI): 10.1126/science.1253393 Link: Link to publication record in Edinburgh Research Explorer Document Version: Peer reviewed version Published In: Science General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 28. Sep. 2021 Ediacaran metazoan reefs from the Nama Group, Namibia Author list Penny, A. M.1, Wood, R.1, Curtis, A.1, Bowyer, F.1, Tostevin, R.2 and Hoffman, K.- H.3 Affiliations 1 School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK 2University College London, Department of Earth Sciences, Gower Street, London WC1E 6BT, UK 3Geological Survey of Namibia, Private Bag 13297, Windhoek, Namibia Abstract Reef-building in metazoans represents an important ecological innovation, whereby individuals collectively enhance feeding efficiency and gain protection from competitors and predation. -
Back Matter (PDF)
Index Acraman impact ejecta layer 53–4, 117, 123, 126–9, Aspidella 130–2, 425–7 controversy 300, 301–3, 305 acritarchs ecology 303 Amadeus and Officer Basins 119 synonyms 302 biostratigraphy 115–25, 130–2 Australia Australian correlations 130–2 Acraman impact ejecta layer 53–4, 117, 123, 126–9, composite zonation scheme 119, 131, 132 130–2, 425–7 India 318–20 carbon isotope chemostratigraphy 126–9 Ireland 289 correlations of Ediacaran System and Period 18, Spain 232 115–35 sphaeromorphid 324 Marinoan glaciation 53–4, 126 Adelaide, Hallett Cove 68 Australia, Ediacaran System and Period Adelaide Rift Complex 115–22, 425 Bunyeroo–Wonoka Formation transition correlations with Officer Basin 127 137–9, 426 dating (Sr–Rb) 140 Centralian Superbasin 118, 125 generalized time–space diagram, correlations composite zonation scheme 131 between tectonic units 120 correlation methods and results 125–32 location maps 116, 118 time–space diagram 120 SE sector cumulative strata thickness 139 Vendian climatic indicators 17 stratigraphic correlation with Officer Basin 127 See also Adelaide Rift Complex; Flinders Ranges Stuart Shelf drill holes, correlations 117 Avalonian assemblages, Newfoundland 237–57, Sturtian (Umberatana) Group 116, 138 303–7, 427 Umberatana Group 116, 138 Africa backarc spreading, Altenfeld Formation 44–5, 47–8 Vendian climatic indicators 17 Baliana–Krol Group, NW Himalaya 319 see also Namibia Barut Formation, Iran 434 Aldanellidae 418 Bayesian analysis algal metaphyta, White Sea Region 271–4 eumetazoans 357–9 algal microfossils, White -
Biomineralization and Evolutionary History Andrew H
1 111 Biomineralization and Evolutionary History Andrew H. Knoll Department of Organismic and Evolutionary Biology Harvard University Cambridge, Massachusetts, 02138 U.S.A. INTRODUCTION The Dutch ethologist Niko Tinbergen famously distinguished between proximal and ultimate explanations in biology. Proximally, biologists seek a mechanistic understanding of how organisms function; most of this volume addresses the molecular and physiological bases of biomineralization. But while much of biology might be viewed as a particularly interesting form of chemistry, it is more than that. Biology is chemistry with a history, requiring that proximal explanations be grounded in ultimate, or evolutionary, understanding. The physiological pathways by which organisms precipitate skeletal minerals and the forms and functions of the skeletons they fashion have been shaped by natural selection through geologic time, and all have constrained continuing evolution in skeleton-forming clades. In this chapter, I outline some major patterns of skeletal evolution inferred from phylogeny and fossils (Figure 1), highlighting ways that our improving mechanistic knowledge of biomineralization can help us to understand this evolutionary record (see Leadbetter and Riding 1986; Lowenstam and Weiner 1989; Carter 1990; and Simkiss and Wilbur 1989 for earlier reviews). Figure 1. A geologic time scale for the past 1000 million years, showing the principal time divisions used in Earth science and the timing of major evolutionary events discussed in this chapter. Earlier intervals of time—the Mesoproterozoic (1600–1000 million years ago) and Paleoproterozoic (2500– 1600 million years ago) eras of the Proterozoic Eon and the Archean Eon (> 2500 million years ago)— are not shown. Time scale after Remane (2000). -
Department of the Interior Us Geological Survey
DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Annotated Bibliography of Tectonostratigraphic and Organic Geochemical Characteristics of Upper Precambrian Rocks Related to Their Petroleum Potential By Gregory Ulmishek Open-File Report 90-63 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature, U.S. Geological Survey, Box 25046, Denver Federal Center, Denver, CO 80225 1989 CONTENTS Page Scope of the bibliography............................................ 1 General problems..................................................... 2 North America........................................................ 7 South America........................................................ 11 China and India...................................................... 12 Australia............................................................ 14 Africa and Arabia.................................................... 19 Russian craton....................................................... 23 Siberia.............................................................. 28 ANNOTATED BIBLIOGRAPHY OF TECTONOSTRATIGRAPHIC AND ORGANIC GEOCHEMICAL CHARACTERISTICS OF UPPER PRECAMBRIAN ROCKS RELATED TO THEIR PETROLEUM POTENTIAL By Gregory F. Ulmishek Scope of the Bibliography This report is a bibliography of tectonics, stratigraphy, and organic geochemistry of upper Precambrian (principally Upper Proterozoic but also some Middle Proterozoic) rocks of the world. Only those publications that are -
The Fossil Record of the Cambrian “Explosion”: Resolving the Tree of Life Critics As Posing Challenges to Evolution
Article The Fossil Record of the Cambrian “Explosion”: 1 Resolving the Tree of Life Keith B. Miller Keith B. Miller The Cambrian “explosion” has been the focus of extensive scientifi c study, discussion, and debate for decades. It has also received considerable attention by evolution critics as posing challenges to evolution. In the last number of years, fossil discoveries from around the world, and particularly in China, have enabled the reconstruction of many of the deep branches within the invertebrate animal tree of life. Fossils representing “sister groups” and “stem groups” for living phyla have been recognized within the latest Precambrian (Neoproterozoic) and Cambrian. Important transitional steps between living phyla and their common ancestors are preserved. These include the rise of mollusks from their common ancestor with the annelids, the evolution of arthropods from lobopods and priapulid worms, the likely evolution of brachiopods from tommotiids, and the rise of chordates and echinoderms from early deuterostomes. With continued new discoveries, the early evolutionary record of the animal phyla is becoming ever better resolved. The tree of life as a model for the diversifi cation of life over time remains robust, and strongly supported by the Neoproterozoic and Cambrian fossil record. he most fundamental claim of bio- (such as snails, crabs, or sea urchins) as it logical evolution is that all living does to the fi rst appearance and diversi- T organisms represent the outer tips fi cation of dinosaurs, birds, or mammals. of a diversifying, upward- branching tree This early diversifi cation of invertebrates of life. The “Tree of Life” is an extreme- apparently occurred around the time of ly powerful metaphor that captures the the Precambrian/Cambrian boundary over essence of evolution.