Vaalbara Palaeomagnetism
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Large and Robust Lenticular Microorganisms on the Young Earth ⇑ ⇑ Dorothy Z
Precambrian Research 296 (2017) 112–119 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres Large and robust lenticular microorganisms on the young Earth ⇑ ⇑ Dorothy Z. Oehler a, , Maud M. Walsh b, Kenichiro Sugitani c, Ming-Chang Liu d, Christopher H. House e, a Planetary Science Institute, Tucson, AZ 85719, USA b School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, LA 70803-2110, USA c Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan d Department of Earth, Planetary, and Space Sciences, University of California at Los Angeles, Los Angeles, CA 90095-1567, USA e Department of Geosciences, The Pennsylvania State University, University Park, PA 16802, USA article info abstract Article history: In recent years, remarkable organic microfossils have been reported from Archean deposits in the Pilbara Received 18 November 2016 craton of Australia. The structures are set apart from other ancient microfossils by their complex lentic- Revised 29 March 2017 ular morphology combined with their large size and robust, unusually thick walls. Potentially similar Accepted 11 April 2017 forms were reported in 1992 from the 3.4 Ga Kromberg Formation (KF) of the Kaapvaal craton, South Available online 26 April 2017 Africa, but their origin has remained uncertain. Here we report the first determination of in situ carbon isotopic composition (d13C) of the lenticular structures in the KF (obtained with Secondary Ion Mass Keywords: Spectrometry [SIMS]) as well as the first comparison of these structures to those from the Pilbara, using Archean morphological, isotopic, and sedimentological criteria. Spindle Lenticular Our results support interpretations that the KF forms are bona fide, organic Archean microfossils and Microfossil represent some of the oldest morphologically preserved organisms on Earth. -
Gangidine NASA Early Career Collaboration Follow-Up
NASA Astrobiology Early Career Collaboration Award Follow-up Report Andrew Gangidine, Ph.D Candidate, University of Cincinnati Project Title: A Step Back in Time – Ancient Hot Springs and the Search for Life on Mars Collaborator: Dr. Martin Van Kranendonk, UNSW, Australian Center for Astrobiology During Summer 2018 I travel to the Pilbara Craton in Western Australia in search of the earliest known evidence of life on land. Here I met up with Dr. Martin Van Kranendonk, director of the Australian Center for Astrobiology and expert on the Pilbara geology. Over the next two weeks, we traveled to many previously established sites of interest containing stromatolitic textures and evidence of past terrestrial hot spring activity, as well as new sites of interest which provided further evidence supporting the terrestrial hot spring hypothesis. Over the course of these two weeks, I collected samples of ~3.5Ga microbial textures in order to analyze such samples for their biosignature preservation potential. I also was able to spend some time mapping the Pilbara in order to understand the greater regional geologic context of the samples I collected. After this field work, Dr. Van Kranendonk and I returned to Sydney, where I met with Dr. Malcolm Walter at the University of New South Wales. Dr. Walter allowed me to search through the sample archive of the Australian Center for Astrobiology, where I collected younger samples from the mid-Paleozoic from terrestrial hydrothermal deposits. With these samples, I am able to perform a comparison study between modern, older, and ancient hydrothermal deposits in order to characterize what happens to potential biosignatures in these environments throughout geologic time. -
Assembly, Configuration, and Break-Up History of Rodinia
Author's personal copy Available online at www.sciencedirect.com Precambrian Research 160 (2008) 179–210 Assembly, configuration, and break-up history of Rodinia: A synthesis Z.X. Li a,g,∗, S.V. Bogdanova b, A.S. Collins c, A. Davidson d, B. De Waele a, R.E. Ernst e,f, I.C.W. Fitzsimons g, R.A. Fuck h, D.P. Gladkochub i, J. Jacobs j, K.E. Karlstrom k, S. Lu l, L.M. Natapov m, V. Pease n, S.A. Pisarevsky a, K. Thrane o, V. Vernikovsky p a Tectonics Special Research Centre, School of Earth and Geographical Sciences, The University of Western Australia, Crawley, WA 6009, Australia b Department of Geology, Lund University, Solvegatan 12, 223 62 Lund, Sweden c Continental Evolution Research Group, School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia d Geological Survey of Canada (retired), 601 Booth Street, Ottawa, Canada K1A 0E8 e Ernst Geosciences, 43 Margrave Avenue, Ottawa, Canada K1T 3Y2 f Department of Earth Sciences, Carleton U., Ottawa, Canada K1S 5B6 g Tectonics Special Research Centre, Department of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia h Universidade de Bras´ılia, 70910-000 Bras´ılia, Brazil i Institute of the Earth’s Crust SB RAS, Lermontova Street, 128, 664033 Irkutsk, Russia j Department of Earth Science, University of Bergen, Allegaten 41, N-5007 Bergen, Norway k Department of Earth and Planetary Sciences, Northrop Hall University of New Mexico, Albuquerque, NM 87131, USA l Tianjin Institute of Geology and Mineral Resources, CGS, No. -
Bayesian Analysis of the Astrobiological Implications of Life's
Bayesian analysis of the astrobiological implications of life's early emergence on Earth David S. Spiegel ∗ y, Edwin L. Turner y z ∗Institute for Advanced Study, Princeton, NJ 08540,yDept. of Astrophysical Sciences, Princeton Univ., Princeton, NJ 08544, USA, and zInstitute for the Physics and Mathematics of the Universe, The Univ. of Tokyo, Kashiwa 227-8568, Japan Submitted to Proceedings of the National Academy of Sciences of the United States of America Life arose on Earth sometime in the first few hundred million years Any inferences about the probability of life arising (given after the young planet had cooled to the point that it could support the conditions present on the early Earth) must be informed water-based organisms on its surface. The early emergence of life by how long it took for the first living creatures to evolve. By on Earth has been taken as evidence that the probability of abiogen- definition, improbable events generally happen infrequently. esis is high, if starting from young-Earth-like conditions. We revisit It follows that the duration between events provides a metric this argument quantitatively in a Bayesian statistical framework. By (however imperfect) of the probability or rate of the events. constructing a simple model of the probability of abiogenesis, we calculate a Bayesian estimate of its posterior probability, given the The time-span between when Earth achieved pre-biotic condi- data that life emerged fairly early in Earth's history and that, billions tions suitable for abiogenesis plus generally habitable climatic of years later, curious creatures noted this fact and considered its conditions [5, 6, 7] and when life first arose, therefore, seems implications. -
THE ARCHAEAN and Earllest PROTEROZOIC EVOLUTION and METALLOGENY of Australla
Revista Brasileira de Geociências 12(1-3): 135-148, Mar.-Sel.. 1982 - Silo Paulo THE ARCHAEAN AND EARLlEST PROTEROZOIC EVOLUTION AND METALLOGENY OF AUSTRALlA DA VID I. OROVES' ABSTRACT Proterozoic fold belts in Austrália developed by lhe reworking of Archaean base mcnt. The nature of this basement and the record of Archaean-earliest Proterozoic evolution and metallogeny is best prescrved in the Western Australian Shield. ln the Yilgarn Craton. a poorly-mineralized high-grade gneiss terrain rccords a complex,ca. 1.0 b.y. history back to ca. 3.6b.y. This terrain is probably basement to lhe ca. 2.9~2.7 b.y. granitoid -greenstone terrains to lhe east-Cratonization was essentially complete by ca, 2.6 b.y. Evolution of the granitoid-greenstone terrains ofthe Pilbara Craton occurred between ca. 3.5b.y. ano 2.8 b.y. The Iectonic seuing of ali granitoid-greenstone terrains rcmains equivocaI. Despitc coincidcnt cale -alkalinc volcanism and granitoid emplacemcnt , and broad polarity analogous to modem are and marginal basin systcrns. thcre is no direct evidencc for plate tectonic processes. Important diffcrences in regional continuity of volcanic scqucnccs, lithofacies. regional tectonic pauerns and meta1Jogeny of lhe terrains may relate to the amount of crusta! extension during basin formation. At onc extreme, basins possibly reprcsenting low total cxrensíon (e.g. east Pilbara l are poorly mi ncralizcd with some porphyry-stylc Mo-Cu and small sulphute-rich volcanogenic 01' evaporitic deposits reflecting the resultam subaerial to shaJlow-water environment. ln contrast, basins inter prctcd to have formcd during greater crusta! cxrcnsion (e.g. -
Proterozoic East Gondwana: Supercontinent Assembly and Breakup Geological Society Special Publications Society Book Editors R
Proterozoic East Gondwana: Supercontinent Assembly and Breakup Geological Society Special Publications Society Book Editors R. J. PANKHURST (CHIEF EDITOR) P. DOYLE E J. GREGORY J. S. GRIFFITHS A. J. HARTLEY R. E. HOLDSWORTH A. C. MORTON N. S. ROBINS M. S. STOKER J. P. TURNER Special Publication reviewing procedures The Society makes every effort to ensure that the scientific and production quality of its books matches that of its journals. Since 1997, all book proposals have been refereed by specialist reviewers as well as by the Society's Books Editorial Committee. If the referees identify weaknesses in the proposal, these must be addressed before the proposal is accepted. Once the book is accepted, the Society has a team of Book Editors (listed above) who ensure that the volume editors follow strict guidelines on refereeing and quality control. We insist that individual papers can only be accepted after satis- factory review by two independent referees. The questions on the review forms are similar to those for Journal of the Geological Society. The referees' forms and comments must be available to the Society's Book Editors on request. Although many of the books result from meetings, the editors are expected to commission papers that were not pre- sented at the meeting to ensure that the book provides a balanced coverage of the subject. Being accepted for presentation at the meeting does not guarantee inclusion in the book. Geological Society Special Publications are included in the ISI Science Citation Index, but they do not have an impact factor, the latter being applicable only to journals. -
Pilbara Conservation Strategy Main Karijini National Park
Pilbara Conservation Strategy Main Karijini National Park. Foreword Photo – Judy Dunlop Over the past eight years, the Liberal National The Pilbara Conservation Strategy is a strategic It is one of only 15 national biodiversity hotspots. these projects will be an important means of funding Government has delivered greater protection for the landscape-scale approach to enhance the region’s The region has many endemic species, including the strategic landscape-scale approach for managing environment than any other government in the history high biodiversity and landscape values across property one of the richest reptile assemblages in the world, fire, feral animals and weeds and meeting the key of this State. boundaries. This initiative by the Liberal National more than 125 species of acacia and more than 1000 outcomes listed in the strategy. Government provides a vision for conservation species of aquatic invertebrates. It is an international This includes the most comprehensive biodiversity in the region. It involves partnerships with local hotspot for subterranean fauna. I invite you to join the Liberal National Government conservation laws seen in Western Australia and land managers, traditional owners, pastoralists, as a partner in this ground-breaking initiative to the implementation of the $103.6 million Kimberley conservation groups, the wider community, industry, The region has a rich and living Aboriginal culture deliver a new level of conservation management for Science and Conservation Strategy — the biggest government and non-government organisations. with traditional owners retaining strong links to the Pilbara. conservation project ever undertaken in WA, which Together, we will deliver improved on-ground country and playing a key role in protecting cultural has implemented a range of measures to retain and management of the key threats to the region’s and natural heritage. -
Evidence from the Yilgarn and Pilbara Cratons 1 1 2 K.F
Origin of Archean late potassic granites: evidence from the Yilgarn and Pilbara Cratons 1 1 2 K.F. CASSIDY , D.C. CHAMPION AND R.H. SMITHIES 1 Geoscience Australia, Canberra, ACT, kevin.cassidy@doir. wa.gov.au, [email protected] 2 Geological Survey of Western Australia, East Perth, WA, [email protected] Late potassic granites are a characteristic feature of many Archean cratons, including the Yilgarn and Pilbara Cratons in Western Australia. In the Yilgarn Craton, these ‘low Ca’ granites comprise over 20 percent by area of the exposed craton, are distributed throughout the entire craton and intruded at c. 2655–2620 Ma, with no evidence for significant diachroneity at the craton scale. In the Pilbara Craton, similar granites are concentrated in the East Pilbara Terrane, have ages of c. 2890–2850 Ma and truncate domain boundaries. Late potassic granites are dominantly biotite granites but include two mica granites. They are ‘crustally derived’ with high K2O/Na2O, high LILE, LREE, U, Th, variable Y and low CaO, Sr contents. They likely represent dehydration melting of older LILE-rich tonalitic rocks at low to moderate pressures. High HFSE contents suggest high temperature melting, consistent with a water-poor source. Models for their genesis must take into account that: 1. the timing of late potassic granites shows no relationship with earlier transitional-TTG plutonism; 2. there is no relationship to crustal age, with emplacement ranging from c. 100 m.y. (eastern Yilgarn) to c. 800 m.y. (eastern Pilbara) after initial crust formation; 3. the emplacement of late granites reflects a change in tectonic environment, from melting of thickened crust and/or slab for earlier TTG magmatism to melting at higher crustal levels; 4. -
The Making and Unmaking of a Supercontinent: Rodinia Revisited
Tectonophysics 375 (2003) 261–288 www.elsevier.com/locate/tecto The making and unmaking of a supercontinent: Rodinia revisited Joseph G. Meerta,*, Trond H. Torsvikb a Department of Geological Sciences, University of Florida, 241 Williamson Hall, PO Box 11210 Gainesville, FL 32611, USA b Academy of Sciences (VISTA), c/o Geodynamics Center, Geological Survey of Norway, Leif Eirikssons vei 39, Trondheim 7491, Norway Received 11 April 2002; received in revised form 7 January 2003; accepted 5 June 2003 Abstract During the Neoproterozoic, a supercontinent commonly referred to as Rodinia, supposedly formed at ca. 1100 Ma and broke apart at around 800–700 Ma. However, continental fits (e.g., Laurentia vs. Australia–Antarctica, Greater India vs. Australia– Antarctica, Amazonian craton [AC] vs. Laurentia, etc.) and the timing of break-up as postulated in a number of influential papers in the early–mid-1990s are at odds with palaeomagnetic data. The new data necessitate an entirely different fit of East Gondwana elements and western Gondwana and call into question the validity of SWEAT, AUSWUS models and other variants. At the same time, the geologic record indicates that Neoproterozoic and early Paleozoic rift margins surrounded Laurentia, while similar-aged collisional belts dissected Gondwana. Collectively, these geologic observations indicate the breakup of one supercontinent followed rapidly by the assembly of another smaller supercontinent (Gondwana). At issue, and what we outline in this paper, is the difficulty in determining the exact geometry of the earlier supercontinent. We discuss the various models that have been proposed and highlight key areas of contention. These include the relationships between the various ‘external’ Rodinian cratons to Laurentia (e.g., Baltica, Siberia and Amazonia), the notion of true polar wander (TPW), the lack of reliable paleomagnetic data and the enigmatic interpretations of the geologic data. -
VAALBARA and TECTONIC EFFECTS of a MEGA IMPACT in the EARLY ARCHEAN 3470 Ma
Large Meteorite Impacts (2003) 4038.pdf VAALBARA AND TECTONIC EFFECTS OF A MEGA IMPACT IN THE EARLY ARCHEAN 3470 Ma T.E. Zegers and A. Ocampo European Space Agency, ESTEC, SCI-SB, Keplerlaan 1, 2201 AZ Noordwijk, [email protected] Abstract The oldest impact related layer recognized on Earth occur in greenstone sequences of the Kaapvaal (South Africa) and Pilbara (Australia) Craton, and have been dated at ca. 3470 Ma (Byerly et al., 2002). The simultaneous occurrence of impact layers now geographically widely separated have been taken to indicate that this was a worldwide phenomena, suggesting a very large impact: 10 to 100 times more massive than the Cretaceous-Tertiary event. However, the remarkable lithostratigraphic and chronostratigraphic similarities between the Pilbara and Kaapvaal Craton have been noted previously for the period between 3.5 and 2.7 Ga (Cheney et al., 1988). Paleomagnetic data from two ultramafic complexes in the Pilbara and Kaapvaal Craton showed that at 2.87 Ga the two cratons could have been part of one larger supercontinent called Vaalbara. New Paleomagnetic results from the older greenstone sequences (3.5 to 3.2 Ga) in the Pilbara and Kaapvaal Craton will be presented. The constructed apparent polar wander path for the two cratons shows remarkable similarities and overlap to a large extent. This suggests that the two cratons were joined for a considerable time during the Archean. Therefore, the coeval impact layers in the two cratons at 3.47 Ga do not necessarily suggest a worldwide phenomena on the present scale of separation of the two cratons. -
Trading Partners: Tectonic Ancestry of Southern Africa and Western Australia, In
Precambrian Research 224 (2013) 11–22 Contents lists available at SciVerse ScienceDirect Precambrian Research journa l homepage: www.elsevier.com/locate/precamres Trading partners: Tectonic ancestry of southern Africa and western Australia, in Archean supercratons Vaalbara and Zimgarn a,b,∗ c d,e f g Aleksey V. Smirnov , David A.D. Evans , Richard E. Ernst , Ulf Söderlund , Zheng-Xiang Li a Department of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, MI 49931, USA b Department of Physics, Michigan Technological University, Houghton, MI 49931, USA c Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA d Ernst Geosciences, Ottawa K1T 3Y2, Canada e Carleton University, Ottawa K1S 5B6, Canada f Department of Earth and Ecosystem Sciences, Division of Geology, Lund University, SE 223 62 Lund, Sweden g Center of Excellence for Core to Crust Fluid Systems, Department of Applied Geology, Curtin University, Perth, WA 6845, Australia a r t i c l e i n f o a b s t r a c t Article history: Original connections among the world’s extant Archean cratons are becoming tractable by the use of Received 26 April 2012 integrated paleomagnetic and geochronologic studies on Paleoproterozoic mafic dyke swarms. Here we Received in revised form ∼ report new high-quality paleomagnetic data from the 2.41 Ga Widgiemooltha dyke swarm of the Yil- 19 September 2012 garn craton in western Australia, confirming earlier results from that unit, in which the primary origin Accepted 21 September 2012 of characteristic remanent magnetization is now confirmed by baked-contact tests. The correspond- Available online xxx ◦ ◦ ◦ ing paleomagnetic pole (10.2 S, 159.2 E, A95 = 7.5 ), in combination with newly available ages on dykes from Zimbabwe, allow for a direct connection between the Zimbabwe and Yilgarn cratons at 2.41 Ga, Keywords: Paleomagnetism with implied connections as early as their cratonization intervals at 2.7–2.6 Ga. -
GSA TODAY North-Central, P
Vol. 9, No. 10 October 1999 INSIDE • 1999 Honorary Fellows, p. 16 • Awards Nominations, p. 18, 20 • 2000 Section Meetings GSA TODAY North-Central, p. 27 A Publication of the Geological Society of America Rocky Mountain, p. 28 Cordilleran, p. 30 Refining Rodinia: Geologic Evidence for the Australia–Western U.S. connection in the Proterozoic Karl E. Karlstrom, [email protected], Stephen S. Harlan*, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 Michael L. Williams, Department of Geosciences, University of Massachusetts, Amherst, MA, 01003-5820, [email protected] James McLelland, Department of Geology, Colgate University, Hamilton, NY 13346, [email protected] John W. Geissman, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, [email protected] Karl-Inge Åhäll, Earth Sciences Centre, Göteborg University, Box 460, SE-405 30 Göteborg, Sweden, [email protected] ABSTRACT BALTICA Prior to the Grenvillian continent- continent collision at about 1.0 Ga, the southern margin of Laurentia was a long-lived convergent margin that SWEAT TRANSSCANDINAVIAN extended from Greenland to southern W. GOTHIAM California. The truncation of these 1.8–1.0 Ga orogenic belts in southwest- ern and northeastern Laurentia suggests KETILIDEAN that they once extended farther. We propose that Australia contains the con- tinuation of these belts to the southwest LABRADORIAN and that Baltica was the continuation to the northeast. The combined orogenic LAURENTIA system was comparable in