DOCSLIB.ORG

Mixed Basalt-Rhyolite Assemblages in Yellowstone National Park: the Petro-Genetic Significance of Magma Mixing

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Mixed Basalt-Rhyolite Assemblages in Yellowstone National Park: the Petro-Genetic Significance of Magma Mixing University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 1978 Mixed basalt-rhyolite assemblages in Yellowstone National Park: The petro-genetic significance of magma mixing Debra Winter Struhsacker The University of Montana Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation Struhsacker, Debra Winter, "Mixed basalt-rhyolite assemblages in Yellowstone National Park: The petro- genetic significance of magma mixing" (1978). Graduate Student Theses, Dissertations, & Professional Papers. 6118. https://scholarworks.umt.edu/etd/6118 This Thesis is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. MIXED BASALT-RHYOLITE ASSEMBLAGES IN YELLOWSTONE NATIOf^L PARK THE PETROGENETIC SIGNIFICANCE OF MAGMA MIXING by Debra Winter Struhsacker B.A., Wellesley College, 1974 Presented in p artial fu lfillm e n t of the requirements fo r the degree of Master of Science UNIVERSITY OF MONTANA 1978 Approved by: > > . , . M Chafnnan, Board of Examiners lean. Graduate Scnool Date UMI Number: EP36919 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMT Pubinhmg UMI EP36919 Published by ProQuest LLC (2013). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProOuesf ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346 MIXED BASALT-RHYOLITE ASSEMBLAGES IN YELLOWSTONE NATIOW\L PARK THE PETROGENETIC SIGNIFICANCE OF MAGMA MIXING by Debra Winter Struhsacker B.A., Wellesley College, 1974 Presented in p a rtia l fu lfillm e n t of the requirements fo r the degree of Master of Science UNIVERSITY OF MONTANA 1978 Approved by A Chairman, Board of Examiners )ean, Graduate Scnool Date ABSTRACT Struhsacker, Debra, M.S., Spring, 1978 Geology Mixed Basalt-Rhyolite Assemblages In Yellowstone National Park: The Petrogenetic S lg n lfl^^e of Magma Mixing Director: David Alt —) ^ The Gardiner River and Geode Creek mixed basalt-rhyol1te assemblages outcrop In the north-central portion of the Quaternary bimodal vol- canlcs In Yellowstone National Park. The Gardiner River lavas Include strikin g "marble-cake" rocks evidently produced as a basaltic magma contaminated a rh y o lltic magma, hybridizing both components. The Geode Creek lavas are a homogeneous, basal tic-looking rock, containing quartz and alkali feldspar grains rimmed by auglte, and resorbed Inclusion-laden crystals of plagloclase with sodic cores and calcic rims. These features Imply contamination of a basaltic magma by a rh y o lltic magma. A survey of these Yellowstone mixed lavas and sim i­ la r mixed assemblages In the Cascades, the San Juan Mountains, Iceland, Scotland, and Ireland suggests that mixing occurs at shallow crustal levels, most commonly In an extenslonal tectonic setting. The Cascade examples, although spatially related to a subduction zone, appear to be shallow magmatic features. Mixing evidently occurs as primary basalt and rhyollte meet. Shallow, extenslonal environments Inhibit mixing because lack of water lim its diffusion and the short distance between the site of mixing and eruption lim its opportunity for mechanical s tirrin g . Deeper magma chambers, such as those In subduction zones, with higher water content and greater opportunity for s tirrin g , produce well-mixed, nearly homogeneous lavas. Thus, In lig h t of this proposed model, magma mixing may play a sig n ifica n t role In the generation of arc andésites which commonly exhibit many disequilibrium features sim ilar to those observed In the Yellowstone mixed lavas. 11 ACKNOWLEDGMENTS I wish to thank David Fountain, George Woodbury and Shirley Pettersen fo r th e ir help with this project. Special thanks go to David Alt for his many helpful discussions of the thesis material and careful editing of this manuscript. I would also like to thank Eric Struhsacker fo r his constant encouragement and geologic insight. This thesis was partially funded by a Grant-in-Aid of Research from Sigma X i, the S cie n tific Research Society of North America. i i i TABLE OF CONTENTS Page ABSTRACT............................................................................................ i l ACKNOWLEDGMENTS.................................................................................. i i i LIST OF TABLES..................................................................................... v ii LIST OF FIGURES .............................................................................. v iii LIST OF PLATES................................................................................. ix CHAPTER I. INTRODUCTION ...................................................................... 1 I I . GEOLOGIC SETTING OF THE YELLOWSTONE REGION ............... 3 Pre-Tertiary Lithologies ............................................ 3 Volcanic History of Yellowstone National Park . 4 Quaternary Volcanism in Yellowstone National P a rk ............................................................... 4 Magma Beneath Yellowstone National Park ............... 7 I I I . REGIONAL TECTONIC SETTING OF THE YELLOWSTONE REGION 10 IV. CHEMISTRY AND TECTONICS OF BIMODAL VOLCANISM IN THE NORTHWEST............................................................... 14 V. MIXED BASALT-RHYOLITE COMPLEXES IN YELLOWSTONE NATIONAL PARK................................................................... 19 The Geode Creek Complex ............................................ 19 The Gardiner River Complex......................................... 20 IV TABLE OF CONTENTS (Continued) CHAPTER Page VI. PETROGRAPHY OF THE GEODE CREEK LAVAS........................... 22 Phenocryst Mineralogy ................................................ 22 Groundmass Mineralogy ................................................ 29 Quartz and A lkali Feldspar Grains .......................... 31 Coarse-Grained Inclusions ......................................... 32 Pétrographie Interpretation ..................................... 32 V II. PETROGRAPHY OF THE GARDINER RIVER LAVAS................... 46 Uncontaminated Basalt ................................................ 46 Contaminated Basalt .................................................... 47 Comparison of the Gardiner River Basalts and the Geode Creek Lavas ......................................... 48 Uncontaminated Rhyollte ............................................ 51 Contaminated Rhyollte ................................................ 51 Comparison of Contaminated Rhyolites and Contaminated Basalts .................................................... 52 Coarse-Grained Inclusions ......................................... 54 V III. SUMMARY OF THE CHARACTERISTICS OF MIXED MAGMAS . 55 Pétrographie Features of Mixed Magmas ................... 55 Thermal Parameters of Magma Mixing .......................... 59 Discussion ...................................................................... 61 IX. CHEMICAL AND ISOTOPIC STUDY OF SOME YELLOWSTONE BASALTS AND RHYOLITES .................................................... 63 The Geode Creek Lavas ................................................ 63 V TABLE OF CONTENTS (Continued) CHAPTER Page The Gardiner River Complex......................................... 69 Age and Composition of the Lower Crust Beneath the Yellowstone Area ................................................ 70 X. OTHER EXAMPLES OF MIXED MAGMAS...................................... 74 Mixed Lavas in the British Isles ................... 74 Mixed Lavas in Ic e la n d .......................................... 78 Tectonic Setting of Iceland and the British Isles 80 Mixed Lavas in the San Juan Vo lc a n ic s .......... 81 Mixed Lavas in the Cascades ........................... 84 Summary .......................................................................... 92 XI. TECTONIC AND PHYSICAL CONTROLS ON MAGMA MIXING . 93 Tectonic Setting of Magma Mixing .............................. 93 Physicochemical Controls on Magma Mixing ............... 95 Bimodal Volcanics as Unmixed Rocks .......................... 99 Bimodal Volcanism and S ilica te Liquid Immiscibility .................................................... 103 X II. SUMMARY AND CONCLUSIONS......................................................105 REFERENCES CITED .............................................................................. 107 vi LIST OF TABLES Table Page 1. Summary of the Minéralogie Variation of the Geode Creek Lavas ............................................ .... 23 2. SlOg, MgO, and Na2 Ü content of the Geode Creek Lavas ............................................................................................. 65 3. Whole-rock Chemical Analysis fo r One Sample of Geode Creek B a s a lt ................................................................... 65 4. Whole-rock
Load more

Recommended publications
  • Uplift, Rupture, and Rollback of the Farallon Slab Reflected in Volcanic
    PUBLICATIONS Journal of Geophysical Research: Solid Earth RESEARCH ARTICLE Uplift, rupture, and rollback of the Farallon slab reflected 10.1002/2017JB014517 in volcanic perturbations along the Yellowstone Key Points: adakite hot spot track • Volcanic perturbations in the Cascadia back-arc region are derived from uplift Victor E. Camp1 , Martin E. Ross2, Robert A. Duncan3, and David L. Kimbrough1 and dismemberment of the Farallon slab from ~30 to 20 Ma 1Department of Geological Sciences, San Diego State University, San Diego, California, USA, 2Department of Earth and • Slab uplift and concurrent melting 3 above the Yellowstone plume Environmental Sciences, Northeastern University, Boston, Massachusetts, USA, College of Earth, Ocean, and Atmospheric promoted high-K calc-alkaline Sciences, Oregon State University, Corvallis, Oregon, USA volcanism and adakite generation • Creation of a seismic hole beneath eastern Oregon resulted from thermal Abstract Field, geochemical, and geochronological data show that the southern segment of the ancestral erosion and slab rupture, followed by Cascades arc advanced into the Oregon back-arc region from 30 to 20 Ma. We attribute this event to thermal a period of slab rollback uplift of the Farallon slab by the Yellowstone mantle plume, with heat diffusion, decompression, and the release of volatiles promoting high-K calc-alkaline volcanism throughout the back-arc region. The greatest Supporting Information: • Supporting Information S1 degree of heating is expressed at the surface by a broad ENE-trending zone of adakites and related rocks • Data Set S1 generated by melting of oceanic crust from the Farallon slab. A hiatus in eruptive activity began at ca. • Data Set S2 22–20 Ma but ended abruptly at 16.7 Ma with renewed volcanism from slab rupture occurring in two separate • Data Set S3 regions.
    [Show full text]
  • Geologic Storage Formation Classification: Understanding Its Importance and Impacts on CCS Opportunities in the United States
    BEST PRACTICES for: Geologic Storage Formation Classification: Understanding Its Importance and Impacts on CCS Opportunities in the United States First Edition Disclaimer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed therein do not necessarily state or reflect those of the United States Government or any agency thereof. Cover Photos—Credits for images shown on the cover are noted with the corresponding figures within this document. Geologic Storage Formation Classification: Understanding Its Importance and Impacts on CCS Opportunities in the United States September 2010 National Energy Technology Laboratory www.netl.doe.gov DOE/NETL-2010/1420 Table of Contents Table of Contents 5 Table of Contents Executive Summary ____________________________________________________________________________ 10 1.0 Introduction and Background
    [Show full text]
  • Volcanic Reconstruction of the Archean North Rhyolite, Kidd Creek Mine, Timmins, Ontario, Canada
    January 2004 Issue 80 Volcanic Reconstruction of the Archean North Rhyolite, Kidd Creek Mine, Timmins, Ontario, Canada Michelle DeWolfe Harold L. Gibson Mineral Exploration Research Centre Laurentian University Ramsey Lake Road, Sudbury, Ontario, P3E 6B5, Email: [email protected] David Richardson Falconbridge Limited Kidd Mining Division, PO Box 2002, Hwy 655, Timmins, Ontario, P4N 7K1 John Ayer Ontario Geological Survey Willet Green Miller Centre, Ramsey Lake Road, Sudbury, Ontario, P3E 6B5 Fig. 1. General geology map showing the Abitibi greenstone belt and Introduction the location of the Kidd Creek mine approximately 24 km north of A succession of volcanic rocks collectively known as the Timmins (modified from Bleeker and Hester, 1999). North Rhyolite (NR) is located directly northeast of the giant Kidd Creek Cu-Zn-Ag volcanogenic massive sulfide (VMS) thermal alteration away from the deposit. Understanding the deposit, within the Abitibi greenstone belt of the Superior prov- large-scale volcanic environment, which hosts the NR and the ince (Figs. 1 and 2). The NR has been interpreted as a lateral Kidd Creek orebodies, will allow a better comparison between extension of the Kidd Creek mine stratigraphy (Hannington et the environment in which the Kidd Creek deposit formed and the al., 1999a). However, detailed work on the stratigraphy and environment of formation for other VMS deposits. This may structure of the NR, and its relationship to the mine stratigraphy, also help to create a better understanding of the environments
    [Show full text]
  • Hydrogeologic Applications for Historical Records and Images from Rock Samples Collected at the Nevada National Security Site An
    A. 1,461 ft 1,600 ft 2,004.5 ft Lithology interpreted by Richard G. Warren, Comprehensive Volcanic Petrographics, LLC 2,204 ft Figure 3. Representation of rock column derived from lithologic records (A) compared with core samples and thin sections thin-section images (B–E) from the UE-19p borehole. B. Adularia (AA) – Orthoclase (a K-spar polymorph typical of granite), that has formed under hydrothermal rather than magmatic conditions. Image from 2,204 ft at 30 degrees polarization. Acmite (AC) – A Na- and Fe3-rich pyroxene typically found as a Allanite (AL) – An epidote-group mineral containing high contents groundmass phase within devitrified peralkaline rock. Image from of rare-earth elements, found in alkali-calcic volcanic rocks. Image 2,004.5 ft at 90 degrees polarization. from 1,600 ft at 30 degrees polarization. C. Biotite (BT) – A hydrated mafic mineral typical of evolved volcanic rocks. Generally lacking in peralkaline units. Image from 1,461 ft at 90 degrees polarization. Glass (GL) – Typically Ca- and Fe-poor, compositionally at the “granite eutectic” within rhyolitic rocks such as those dominant within the Southwestern Nevada Volcanic Field (SWNVF). Unpolarized image from 1,461 ft. Clinopyroxene (CX) – A Ca-rich pyroxene and anhydrous mafic mineral found in a wide variety of volcanic rocks. Image from 1,461 ft at 30 degrees polarization. D. K-feldspar (KF) – A felsic phenocryst ubiquitous as sanidine within the SWNVF, except absent within the wahmonie Formation. Image from 2,004.5 ft at 30 degrees polarization. Lithic (LI) – A rock fragment incorporated into tuff during eruption, Perrierite/Chevkinite (PE) – A pseudobrookite-group mineral usually from the vent.
    [Show full text]
  • Mass-Independent Isotopic Signatures of Volcanic Sulfate from Three Supereruption Ash Deposits in Lake Tecopa, California
    Earth and Planetary Science Letters 282 (2009) 102–114 Contents lists available at ScienceDirect Earth and Planetary Science Letters journal homepage: www.elsevier.com/locate/epsl Mass-independent isotopic signatures of volcanic sulfate from three supereruption ash deposits in Lake Tecopa, California Erwan Martin ⁎, Ilya Bindeman Department of Geological Sciences, 1272 University of Oregon, Eugene OR 97403, USA article info abstract Article history: Hundreds to thousands of megatons of sulfur dioxide released by supereruptions can change chemical and Received 10 October 2008 physical properties of the atmosphere and thus induce climate perturbations. We present oxygen and sulfur Received in revised form 24 February 2009 isotope analyses of sulfate in 48 volcanic ash samples, and 26 sediment samples from dry lake beds in the Accepted 2 March 2009 Tecopa basin, California, USA. These ash layers represent three supereruptions, including the 0.64 Ma Lava Available online 10 April 2009 Creek Tuff, 2.04 Ma Huckleberry Ridge Tuff and 0.76 Ma Bishop Tuff. 17 Editor: R.W. Carlson Mass-independent oxygen signatures (Δ O up to 2.26‰) that are present in these ash units, and not in associated sediments, indicate oxidation of volcanic SO2 by mass-independent ozone and its products. In this Keywords: study, we consider the formation, deposition, preservation and dilution of mass-independent volcanic sulfate oxygen and sulfur isotopes (MIVS). Using the isotopic compositions of the sulfates, we construct a mixing model that demonstrates that isotopic mass-independence the main source of sulfate in Lake Tecopa is mass-dependent sediment-derived sulfate (MDSDS, >77%). sulfate However, ash beds still preserve up to 23% of MIVS that initially had undiluted Δ17O value around 8‰, and aerosols Δ33S as low as −0.35‰, and Δ36S up to 1.08‰.
    [Show full text]
  • Appendix a Conceptual Geologic Model
    Newberry Geothermal Energy Establishment of the Frontier Observatory for Research in Geothermal Energy (FORGE) at Newberry Volcano, Oregon Appendix A Conceptual Geologic Model April 27, 2016 Contents A.1 Summary ........................................................................................................................................... A.1 A.2 Geological and Geophysical Context of the Western Flank of Newberry Volcano ......................... A.2 A.2.1 Data Sources ...................................................................................................................... A.2 A.2.2 Geography .......................................................................................................................... A.3 A.2.3 Regional Setting ................................................................................................................. A.4 A.2.4 Regional Stress Orientation .............................................................................................. A.10 A.2.5 Faulting Expressions ........................................................................................................ A.11 A.2.6 Geomorphology ............................................................................................................... A.12 A.2.7 Regional Hydrology ......................................................................................................... A.20 A.2.8 Natural Seismicity ...........................................................................................................
    [Show full text]
  • The Mineralogy and Chemistry of the Anorogenic Tertiary Silicic Volcanics
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 86, NO. Bll, PAGES 10242-10256, NOVEMBER 10, 1981 The Mineralogyand Chemistryof the AnorogenicTertiary SilicicVolcanics of S.E. Queenslandand N.E. New South Wales, Australia A. EWART Departmentof Geology& Mineralogy,University of Queensland,St. Lucia,Brisbane, Queensland 4067 The Late Oligocene-EarlyMiocene volcanismof this regionis chemicallystrongly bimodal; the mafic lavas(volmetrically dominant) comprise basalts, hawaiites, and tholeiiticandesites, while the silicic eruptivesare mainly comendites,potassic trachytes, and potassic,high-silica rhyolites.The comendites and rhyoliteshave distinctivetrace element abundancepatterns, notably the extreme depletionsof Sr, Ba, Mg, Mn, P, Cr, V, and Eu, and the variable em'ichraentof suchelements as Rb, Zr, Pb, Nb, Zn, U, and Th. The trachytesexhibit thesecharacteristics to lesserdegrees. The comenditesare distinguished from the rhyolitesby their overall relative enrichmentof the more highly chargedcations (e.g., LREE, Nb, Y, and especiallyZr) and Zn. The phenocrystmineralogy of the trachytesand rhyolitescomprises various combinationsof the following phases:sodic plagioclase(albite-andesine), calcic anorthoclase, sanidine, quartz, ferroaugite-ferrohedenbergite,ferrohypersthene, fayalitic olivine, ilmenite, titano- magnetite,and rarely biotite (near annite) and Fe-hastingsiticamphibole. Accessories include apatite, zircon, chevkinite (ferrohedenbergite-bearingrhyolites only), and allanite (amphibole and botite rhyo- lites only). The comenditesgenerally contain
    [Show full text]
  • Mineralogy and Petrology of the Santo Tomas-Black Mountain Basalt Field, Potrillo Volcanics, South-Central New Mexico
    JERRY M. HOFFER Department of Geological Sciences, The University of Texas at El Paso, El Paso, Texas 79900 Mineralogy and Petrology of the Santo Tomas-Black Mountain Basalt Field, Potrillo Volcanics, South-Central New Mexico ABSTRACT called the Santo Tomas-Black Mountain basalt field (Hoffer, 1969c). The Santo Tomas-Black Mountain basalts The Santo Tomas-Black Mountain basalt were erupted during the Quaternary from field includes four major centers, each with four centers. Six lava flows are present at one or more cones and associated flows Black Mountain, three at Santo Tomas, and (Hoffer, 1969a). From north to south, the one each at Little Black Mountain and San four volcanic centers are Santo Tomas, San Miguel. The basalts are grouped into three Miguel, Little Black Mountain, and Black major types of phenocryst mineralogy: (l) Mountain. The largest volume of lava has plagioclase abundant, (2) olivine abundant, been extruded from the Black Mountain and and (3) both olivine and plagioclase abundant. Santo Tomas centers where six and three All three types are alkali-olivine basalts, individual flows, respectively, have been showing high alkali-silica ratios and total mapped (Hoffer, 1969a). Each of the two alkali content increasing with silica. intervening centers, Little Black Mountain Seven periods of basaltic extrusion among and San Miguel, shows only a single flow. the centers have been established on the No flow from a given center coalesces with basis of field evidence, phenocryst mineralogy, those from neighboring centers, but all ap- and pyroxene-olivine ratios. K-Ar dates show pear to be closely related in time (Kottlowski, the basalts to be less than 0.3 X 106 m.y.
    [Show full text]
  • Cascades Volcano Observatory Monitoring Cascade Volcanoes
    Cascades Volcano Observatory Monitoring Cascade Volcanoes http://volcanoes.usgs.gov/observatories/cvo/cvo_monitoring.html About CVO Monitoring Cascade Volcanoes Volcano Updates Volcano eruption forecasting relies on several disciplines of volcanology. Hazards Active volcanoes are complex natural systems, Monitoring and understanding a volcano's behaviors requires the attention of specialists from many science Seismicity disciplines. It demands a combination of current Deformation knowledge about magma systems, tectonic plate motion, volcano deformation, earthquakes, gases, Volcanic Gas chemistry, volcano histories, processes, and Lahar Detection hazards. Hydrothermal No single tool or technique can adequately monitor or predict volcanic behaviors. Therefore, Innovative Techniques volcanologists rely on an assortment of instruments and techniques to monitor volcanic unrest. This CVO Education requires placement of monitoring instruments both Prepare close to and far away from the primary source of eruptive activity (e.g. in a crater, on the crater rim, Multimedia and on the volcano's flanks). By placing sensitive monitoring instruments at hazardous volcanoes in Regional Volcanism Helicopter dropping off monitoring equipment at Mount St. advance of the unrest, the USGS CVO helps to Helens, Washington. ensure that communities at risk can be forewarned with sufficient time to prepare and implement response plans and mitigation measures. Recommendations for the numbers and types of ground-based sensors were made by an interdisciplinary team of scientists as part of planning for the National Volcano Early Warning System. CVO uses these recommendations to plan monitoring improvements throughout the Cascades. You can watch interviews with volcano scientists (Web Shorts) about their research and monitoring efforts and videos about volcano monitoring techniques in the Multimedia section of this website.
    [Show full text]
  • Middle Eocene CO and Climate Reconstructed from the Sediment Fill
    Middle Eocene CO2 and climate reconstructed from the sediment fill of a subarctic kimberlite maar Alexander P. Wolfe1, Alberto V. Reyes2*, Dana L. Royer3, David R. Greenwood4, Gabriela Doria3,5, Mary H. Gagen6, Peter A. Siver7, and John A. Westgate8 1Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada 2Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada 3Department of Earth and Environmental Sciences, Wesleyan University, Middletown, Connecticut 06459, USA 4Department of Biology, Brandon University, Brandon, Manitoba R7A 6A9, Canada 5Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK 6Department of Geography, Swansea University, Singleton Park, Swansea SA2 8PP, UK 7Department of Botany, Connecticut College, New London, Connecticut 06320, USA 8Department of Earth Sciences, University of Toronto, Toronto, Ontario M5S 3B1, Canada ABSTRACT mismatch and frustrates efforts to understand the sensitivity of past equi- Eocene paleoclimate reconstructions are rarely accompanied librium climate response to greenhouse gas forcing. by parallel estimates of CO2 from the same locality, complicating Our objective is to assess climate and greenhouse-gas forcing for assessment of the equilibrium climate response to elevated CO2. We Northern Hemisphere subarctic latitudes during the latest middle Eocene reconstruct temperature, precipitation, and CO2 from latest middle by exploiting a remarkable terrestrial sedimentary archive. The Giraffe Eocene (ca. 38 Ma) terrestrial sediments in the posteruptive sediment kimberlite locality (paleolatitude ~63°N) comprises the posteruptive sedi- fill of the Giraffe kimberlite in subarctic Canada. Mutual climatic mentary fill of a maar formed when kimberlite intruded Precambrian cra- range and oxygen isotope analyses of botanical fossils reveal a humid- tonic rocks of the Slave Province at 47.8 ± 1.4 Ma (Creaser et al., 2004).
    [Show full text]
  • The Science Behind Volcanoes
    The Science Behind Volcanoes A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber below the surface. Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust in the interiors of plates, e.g., in the East African Rift, the Wells Gray-Clearwater volcanic field and the Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "Plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so- called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth. Erupting volcanoes can pose many hazards, not only in the immediate vicinity of the eruption. Volcanic ash can be a threat to aircraft, in particular those with jet engines where ash particles can be melted by the high operating temperature. Large eruptions can affect temperature as ash and droplets of sulfuric acid obscure the sun and cool the Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere.
    [Show full text]
  • Related Magmatism in the Upper Wind River Basin, Wyoming (USA), GEOSPHERE; V
    Research Paper THEMED ISSUE: Cenozoic Tectonics, Magmatism, and Stratigraphy of the Snake River Plain–Yellowstone Region and Adjacent Areas GEOSPHERE The leading wisps of Yellowstone: Post–ca. 5 Ma extension- related magmatism in the upper Wind River Basin, Wyoming (USA), GEOSPHERE; v. 14, no. 1 associated with the Yellowstone hotspot tectonic parabola doi:10.1130/GES01553.1 Matthew E. Brueseke1, Anna C. Downey1, Zachary C. Dodd1, William K. Hart2, Dave C. Adams3, and Jeff A. Benowitz4 12 figures; 2 tables; 1 supplemental file 1Department of Geology, Kansas State University, 108 Thompson Hall, Manhattan, Kansas 66506, USA 2Department of Geology and Environmental Earth Science, Miami University, 118C Shideler Hall, Oxford, Ohio 45056, USA 3Box 155, Teton Village, Wyoming 83025, USA CORRESPONDENCE: brueseke@ ksu .edu 4Geophysical Institute and Geochronology Laboratory, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA CITATION: Brueseke, M.E., Downey, A.C., Dodd, Z.C., Hart, W.K., Adams, D.C., and Benowitz, J.A., 2018, The leading wisps of Yellowstone: Post–ca. 5 Ma ABSTRACT the issue of linking volcanic events to a specific driving mechanism (Fouch, extension-related magmatism in the upper Wind River 2012; Kuehn et al., 2015). Complicating matters, magmatism often continues Basin, Wyoming (USA), associated with the Yellow- The upper Wind River Basin in northwest Wyoming (USA) is located ~80– long after (e.g., millions of years) the upper plate has been translated away stone hotspot tectonic parabola: Geosphere, v. 14, no. 1, p. 74–94, doi:10.1130/GES01553.1. 100 km southeast of the Yellowstone Plateau volcanic field. While the upper from an upwelling plume (Bercovici and Mahoney, 1994; Sleep, 2003; Shervais Wind River Basin is a manifestation of primarily Cretaceous to Eocene Lara- and Hanan, 2008; Jean et al., 2014).
    [Show full text]