DOCSLIB.ORG

Aula 4 – Tipos Crustais Tipos Crustais Continentais E Oceânicos

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Aula 4 – Tipos Crustais Tipos Crustais Continentais E Oceânicos 14/09/2020 Aula 4 – Tipos Crustais Introdução Crosta e Litosfera, Astenosfera Crosta Oceânica e Tipos crustais oceânicos Crosta Continental e Tipos crustais continentais Tipos crustais Continentais e Oceânicos A interação divergente é o berço fundamental da litosfera oceânica: não forma cadeias de montanhas, mas forma a cadeia desenhada pela crista meso- oceânica por mais de 60.000km lineares do interior dos oceanos. A interação convergente leva inicialmente à formação dos arcos vulcânicos e magmáticos (que é praticamente o berço da litosfera continental) e posteriormente à colisão (que é praticamente o fechamento do Ciclo de Wilson, o desparecimento da litosfera oceânica). 1 14/09/2020 Curva hipsométrica da terra A área de superfície total da terra (A) é de 510 × 106 km2. Mostra a elevação em função da área cumulativa: 29% da superfície terrestre encontra-se acima do nível do mar; os mais profundos oceanos e montanhas mais altas uma pequena fração da A. A > parte das regiões de plataforma continental coincide com margens passivas, constituídas por crosta continental estirada. Brito Neves, 1995. Tipos crustais circunstâncias geométrico-estruturais da face da Terra (continentais ou oceânicos); Característica: transitoriedade passar do Tempo Geológico e como forma de dissipar o calor do interior da Terra. Todo tipo crustal adveio de um outro ou de dois outros, e será transformado em outro ou outros com o tempo, toda esta dança expressando a perda de calor do interior para o exterior da Terra. Nenhum tipo crustal é eterno; mais "duráveis" (e.g. velhos Crátons de de "ultra-longa duração"); tipos de curta duração, muitas modificações e rápida evolução potencial (como as bacias de antearco). 2 14/09/2020 A crosta e a litosfera granodiorítica. A crosta e a litosfera 3 14/09/2020 A crosta e a litosfera A crosta e a litosfera 4 14/09/2020 Litosfera • Crosta + parte superior do manto (i.e., + fria e mais forte); (parte do manto da litosfera manto litosférico) • limite entre litosfera e a astenosfera subjacente: limite térmico; • limite entre a crosta e o manto superior (que juntos formam a litosfera) é um limite composicional, ou seja, é devido a uma alteração na composição química litosfera Crosta Oceânica E Tipos Crustais Oceânicos 5 14/09/2020 Crosta Oceânica As rochas da crosta oceânica são muito jovens, não mais de 200 Ma, em comparação com as rochas da crosta continental (até 4,3 Ga). Formação nas c.m.o: A descompressão ocorre sob fendas (rifts) na crosta, tais como aquelas encontrados nas cristas meso-oceânicas, e é através dessas fendas que lava é extrudida para a superfície para criar nova crosta oceânica. Crosta Oceânica • 59% da superfície terrestre (A), 21% (V) http://www.indiana.edu/~g 3 105lab/images/gaia_chapt • densidade média 3,3 g/cm er_13/ocean_crust.jpg • idade máxima 200 Ma • composição homogênea, basáltica • espessura média 5 a 10 km • limite inferior – descontinuidade sísmica de Mohorovicic • Subdivisão • camada sup – sed. de fundo oceânico (camada muito delgada) • camada intermediária – basaltos e diques de diabásio (MORB- low K2O (< 0.2%) and low TiO2 (< 2.0%) • camada inferior – gabros e rochas ultrabásicas cumuláticas 6 14/09/2020 Crosta Oceânica oceanic crust, which all forms in the same way at mid-ocean ridges, has the same overall structure everywhere on the planet. • C.O.: Continuamente sendo criada nas c.m.o. por onde o magma sobe no manto superior e crosta, a medida que as placas divergem. • A medida que se afasta da cadeia, a litosfera torna- se mais fria e mais densa. • A litosfera oceânica mais jovem está nas cristas oceânicas e é progressivamente mais velha longe delas. 7 14/09/2020 Crosta oceânica: distintas camadas (ofiolitos + estudos de laboratório de sondagem e estudos de refração sísmica) 1 2a Ofiolitos: fatias de crosta oceânica, colocadas na cr. 2b continental por cavalgamento 3 Sequência típica de Crosta oceânica Sequência ofiolítica. GSA Penrose Conference 1972. 8 14/09/2020 9 14/09/2020 Sequência ofiolítica de Chipre Transição na sequência basal de rochas mantélicas ricas em olivina (dunitos, harzburgitos) para gabros e peridotitos com plagioclásio diques Gabro acamadado Diques cortando sequencia de lavas almofadadas, sobre uma brecha/ hialoclastito da lava almofadada. 10 14/09/2020 Ofiolitos no Brasil Queiroga et al. 2012 Pirapora do Bom Jesus-SP ~630 Ma 11 14/09/2020 Tipos crustais oceânicos O assoalho oceânico pode ser dividido em províncias batimétricas distintas, regiões que se encontram dentro de uma gama de determinada profundidade e têm um tipo característico de paisagem submarina: Tipos crustais oceânicos • Crista meso-oceânica • Planície abissal (bacia oceânica) • Montes submarinos • Ilhas vulcânicas • Platôs basálticos • Bacias associadas a zonas de subducção: – Fossa – Ante-arco – Intra-arco – Retro-arco • Fossas oceânicas • Prisma acrescionário 12 14/09/2020 Crista meso-oceânica Mid-ocean ridges cr. oc processo de espalhamento do fundo oceânico Distribuição das dorsais oceânicas 13 14/09/2020 A 10-1000km 2266,0m B Longas cadeias de montanhas submarinas, se elevam a cerca de 2 km acima das planícies abissais. Suas cristas, portanto, geralmente estão a cerca de 2– 3 km de profundidade. C.M.O. simétricas em relação a um eixo central, ao longo do qual vulcanismo submarino ativo ocorre. C.M.O. marcam a presença de um limite de placa divergente espalhamento do fundo oceânico ocorre. Planície abissal (bacia oceânica) Grandes planícies submarinas do oceano, muito planas, que se encontram em profundidades de entre 3 km e 5 km. Elas estão cobertas com camada de sedimentos pelágicos de (profundidade). 14 14/09/2020 Seamounts e Guyots Seamounts e Guyots 15 14/09/2020 Montes submarinos Seamounts e São montes submarinos que não fazem parte de c.m.o. Normalmente em cadeias contínuas ao longo de seu comprimento, com uma cadeia de ilhas oceânicas. A ilha no final da cadeia pode ser um vulcão ativo. Se origina como uma ilha vulcânica de hotspot, formada acima uma pluma do manto. Quando o vulcão ‘deriva’ da pluma, ele torna-se extinto e afunda-se abaixo do nível do mar Montes submarinos Seamounts São vulcões extintos, persistindo subaquáticos. Faixas, agrupados, isolados Ás vezes associados com falhas transformantes e zonas de fraturas Magmatismo similar ao da CMO Há modelos especiais distinto de plumas, por propagação de fraturas 16 14/09/2020 Guyots Guyot • Guyots (tablemount): são montes submarinos achatados. A parte de cima lisa (achatada) pode ter sido formado pela erosão de um monte submarino, a medida que monte submarino ficou submerso, ou pode ser o relicto de um recife de coral que se formou assim que o monte submarino ficou submerso. Their flatness is due to erosion by waves, winds, and atmospheric processes 17 14/09/2020 Atol Um atol exibindo uma franja de recife (fringing reef) em torno de um pico vulcânico erodido processo dinâmico da formação de um atol de coral Os corais (tons de roxo e de castanho-rosa) estabelecem um crescimento em volta do console oceânico, dando forma a um recife. Em circunstâncias favoráveis, o recife expandirá. Eventualmente o console do subsolo completamente abaixo da água, deixa um anel de crescimento do coral com uma lagoa aberta no centro. O processo da formação do atol demora 30 Ma a ocorrer. Seamounts e Guyots. Ex Fernando de Noronha 18 14/09/2020 Posicionamento dentro da cadeia de montanhas oceânicas distribuídas nas zonas de fraturas transformantes de Fernando de Noronha e Romanche e as extensões continentais destes sistemas representando o traço fóssil do hot spot de Fernando de Noronha 1.Azores hotspot 2.Balleny hotspot 3.Bowie hotspot 4.Caroline hotspot 5.Cobb hotspot 6.Darfur hotspot 7.Easter hotspot 8.Eifel hotspot 9.Fernando hotspot 10.Galápagos hotspot 11.Guadalupe hotspot 12.Hawaii hotspot 13.Hoggar hotspot 14.Iceland hotspot 15.Jan Mayen hotspot 16.Juan Fernández hotspot 17.Cameroon hotspot 18.Canary hotspot 19.Cape Verde hotspot 20.Kerguelen hotspot 21.Comoros hotspot 22.Lord Howe hotspot 23.Louisville hotspot 24.Macdonald hotspot 25.Marion hotspot 26.Marquesas hotspot 27.Shona hotspot (aka Meteor) 28.New England hotspot 29.Afar hotspot 30.East Australia hotspot 31.Pitcairn hotspot 32.Jemez Lineament (Raton hotspot trail) 33.Réunion hotspot 34.St. Helena hotspot 35.Samoa hotspot 36.San Felix hotspot 37.Socorro hotspot 38.Society hotspot (Tahiti hotspot) 39.Tasmantid hotspot 40.Tibesti hotspot 41.Trindade hotspot 42.Tristan hotspot 43.Vema hotspot 44.Yellowstone hotspot 45.Anahim hotspot 19 14/09/2020 Superswells African superswell South Pacific superswell Large area of anomalously high topography and shallow ocean regions39 . Platôs submarinos Tetreault et al 2014 20 14/09/2020 Platôs submarinos grandes regiões onde o oceano é anormalmente raso. Submarine plateaus Provavelmente se formam acima de grandes hot-spots. The Mascarene Plateau is a submarine plateau in the Indian The Naturaliste Plateau is one of several large Ocean, north and east of Madagascar. The plateau extends submarine plateaus extending from Western Australia approximately 2000 km, from the Seychelles in the north to into the Indian Ocean. It is a rectilinear plateau that Réunion in the south. The plateau covers an area of over covers an area of 90,000 km2. Its width is about 400 km 115,000 km² of shallow water, with depths ranging from 8 – east-west and 250 km north-south. The water depths 150 m, plunging to 4000 m to the abyssal plain at its edges. are from 1500 to 5000 m. It lies to the NE of the It is the largest undersea plateau in the Indian Ocean. Diamantina Fracture Zone. 21 14/09/2020 • Bacias associadas a zonas de subducção: – Ante-arco – Intra-arco Se você fizer um perfil da Planície – Retro-arco Abissal de uma bacia oceânica através de um limite de placa • Fossas oceânicas convergente, encontrará várias • Prisma acrescionário feições tectônicas distintas: 22 14/09/2020 Oceanic trenches • Fossas Oceânicas: Porções profundas submarinas lineares, em que a profundidade da água varia de 6 a 11 km.
Load more

Recommended publications
  • Volcanic Ash Over Europe During the Eruption of Eyjafjallajökull on Iceland, April–May 2010 In: Atmospheric Environment (2011) Elsevier
    Final Draft of the original manuscript: Langmann, B.; Folch, A.; Hensch, M.; Matthias, V.: Volcanic ash over Europe during the eruption of Eyjafjallajökull on Iceland, April–May 2010 In: Atmospheric Environment (2011) Elsevier DOI: 10.1016/j.atmosenv.2011.03.054 1 Volcanic ash over Europe during the eruption of Eyjafjallajökull on Iceland, 2 April-May 2010 3 4 Baerbel Langmann1), Arnau Folch2), Martin Hensch3) and Volker Matthias4) 5 6 1) Institute of Geophysics, University of Hamburg, KlimaCampus, Hamburg, Germany, 7 e-mail: [email protected] 8 2) Barcelona Supercomputing Center - Centro Nacional de Supercomputación, Barcelona, 9 Spain, e-mail: [email protected] 10 3) Nordic Volcanological Center, University of Iceland, Reykjavik, Iceland, e-mail: 11 [email protected] 12 4) Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany, 13 e-mail: [email protected] 14 15 Abstract 16 During the eruption of Eyjafjallajökull on Iceland in April/May 2010, air traffic over Europe 17 was repeatedly interrupted because of volcanic ash in the atmosphere. This completely 18 unusual situation in Europe leads to the demand of improved crisis management, e.g. 19 European wide regulations of volcanic ash thresholds and improved forecasts of theses 20 thresholds. However, the quality of the forecast of fine volcanic ash concentrations in the 21 atmosphere depends to a great extent on a realistic description of the erupted mass flux of fine 22 ash particles, which is rather uncertain. Numerous aerosol measurements (ground based and 23 satellite remote sensing, and in situ measurements) all over Europe have tracked the volcanic 24 ash clouds during the eruption of Eyjafjallajökull offering the possibility for an 25 interdisciplinary effort between volcanologists and aerosol researchers to analyse the release 26 and dispersion of fine volcanic ash in order to better understand the needs for realistic 27 volcanic ash forecasts.
    [Show full text]
  • Iceland Is Cool: an Origin for the Iceland Volcanic Province in the Remelting of Subducted Iapetus Slabs at Normal Mantle Temperatures
    Iceland is cool: An origin for the Iceland volcanic province in the remelting of subducted Iapetus slabs at normal mantle temperatures G. R. Foulger§1 & Don L. Anderson¶ §Department of Geological Sciences, University of Durham, Science Laboratories, South Rd., Durham, DH1 3LE, U.K. ¶California Institute of Technology, Seismological Laboratory, MC 252-21, Pasadena, CA 91125, U. S. A. Abstract The time-progressive volcanic track, high temperatures, and lower-mantle seismic anomaly predicted by the plume hypothesis are not observed in the Iceland region. A model that fits the observations better attributes the enhanced magmatism there to the extraction of melt from a region of upper mantle that is at relatively normal temperature but more fertile than average. The source of this fertility is subducted Iapetus oceanic crust trapped in the Caledonian suture where it is crossed by the mid-Atlantic ridge. The extraction of enhanced volumes of melt at this locality on the spreading ridge has built a zone of unusually thick crust that traverses the whole north Atlantic. Trace amounts of partial melt throughout the upper mantle are a consequence of the more fusible petrology and can explain the seismic anomaly beneath Iceland and the north Atlantic without the need to appeal to very high temperatures. The Iceland region has persistently been characterised by complex jigsaw tectonics involving migrating spreading ridges, microplates, oblique spreading and local variations in the spreading direction. This may result from residual structural complexities in the region, inherited from the Caledonian suture, coupled with the influence of the very thick crust that must rift in order to accommodate spreading-ridge extension.
    [Show full text]
  • Cenozoic Changes in Pacific Absolute Plate Motion A
    CENOZOIC CHANGES IN PACIFIC ABSOLUTE PLATE MOTION A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI`I IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN GEOLOGY AND GEOPHYSICS DECEMBER 2003 By Nile Akel Kevis Sterling Thesis Committee: Paul Wessel, Chairperson Loren Kroenke Fred Duennebier We certify that we have read this thesis and that, in our opinion, it is satisfactory in scope and quality as a thesis for the degree of Master of Science in Geology and Geophysics. THESIS COMMITTEE Chairperson ii Abstract Using the polygonal finite rotation method (PFRM) in conjunction with the hotspot- ting technique, a model of Pacific absolute plate motion (APM) from 65 Ma to the present has been created. This model is based primarily on the Hawaiian-Emperor and Louisville hotspot trails but also incorporates the Cobb, Bowie, Kodiak, Foundation, Caroline, Mar- quesas and Pitcairn hotspot trails. Using this model, distinct changes in Pacific APM have been identified at 48, 27, 23, 18, 12 and 6 Ma. These changes are reflected as kinks in the linear trends of Pacific hotspot trails. The sense of motion and timing of a number of circum-Pacific tectonic events appear to be correlated with these changes in Pacific APM. With the model and discussion presented here it is suggested that Pacific hotpots are fixed with respect to one another and with respect to the mantle. If they are moving as some paleomagnetic results suggest, they must be moving coherently in response to large-scale mantle flow. iii List of Tables 4.1 Initial hotspot locations .
    [Show full text]
  • S41467-020-18361-4.Pdf
    ARTICLE https://doi.org/10.1038/s41467-020-18361-4 OPEN Seafloor evidence for pre-shield volcanism above the Tristan da Cunha mantle plume ✉ Wolfram H. Geissler 1 , Paul Wintersteller 2,3, Marcia Maia4, Anne Strack3, Janina Kammann5, Graeme Eagles 1, Marion Jegen6, Antje Schloemer1,7 & Wilfried Jokat 1,2 Tristan da Cunha is assumed to be the youngest subaerial expression of the Walvis Ridge hot spot. Based on new hydroacoustic data, we propose that the most recent hot spot volcanic 1234567890():,; activity occurs west of the island. We surveyed relatively young intraplate volcanic fields and scattered, probably monogenetic, submarine volcanoes with multibeam echosounders and sub-bottom profilers. Structural and zonal GIS analysis of bathymetric and backscatter results, based on habitat mapping algorithms to discriminate seafloor features, revealed numerous previously-unknown volcanic structures. South of Tristan da Cunha, we discovered two large seamounts. One of them, Isolde Seamount, is most likely the source of a 2004 submarine eruption known from a pumice stranding event and seismological analysis. An oceanic core complex, identified at the intersection of the Tristan da Cunha Transform and Fracture Zone System with the Mid-Atlantic Ridge, might indicate reduced magma supply and, therefore, weak plume-ridge interaction at present times. 1 Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, 27568 Bremerhaven, Germany. 2 Faculty of Geosciences, University of Bremen, Klagenfurter Str. 4, 28359 Bremen, Germany. 3 MARUM—Center of Marine Environmental Sciences, University of Bremen, Leobener Str. 8, 28359 Bremen, Germany. 4 CNRS-UBO Laboratoire Domaines Océaniques, Institut Universitaire Européen de la Mer, 29280 Plouzané, France.
    [Show full text]
  • Ancient Helium and Tungsten Isotopic Signatures Preserved in Mantle Domains Least Modified by Crustal Recycling
    Ancient helium and tungsten isotopic signatures preserved in mantle domains least modified by crustal recycling Matthew G. Jacksona,1, Janne Blichert-Toftb,2, Saemundur A. Halldórssonc,2, Andrea Mundl-Petermeierd, Michael Bizimise, Mark D. Kurzf, Allison A. Pricea, Sunna Harðardóttirc, Lori N. Willhitea,g, Kresten Breddamh, Thorsten W. Beckeri,j, and Rebecca A. Fischerk aDepartment of Earth Science, University of California, Santa Barbara, CA 93106-9630; bLaboratoire de Géologie de Lyon, Ecole Normale Supérieure de Lyon, CNRS, and Université de Lyon, 69007 Lyon, France; cNordVulk, Institute of Earth Sciences, University of Iceland, 102 Reykjavík, Iceland; dDepartment of Lithospheric Research, University of Vienna, 1090 Vienna, Austria; eSchool of the Earth, Ocean and Environment, University of South Carolina, Columbia, SC 29208; fDepartment of Marine Chemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543; gDepartment of Geology, University of Maryland, College Park, MD 20742; hRadiation Protection, Danish Health Authority, 2300 Copenhagen, Denmark; iInstitute for Geophysics, The Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713; jDepartment of Geological Sciences, The Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713; and kDepartment of Earth & Planetary Sciences, Harvard University, Cambridge, MA 02138 Edited by Albrecht W. Hofmann, Max Planck Institute for Chemistry, Mainz, Germany, and approved October 22, 2020 (received for review May 14, 2020) Rare high-3He/4He signatures in ocean island basalts (OIB) erupted Sr-Nd-Pb isotopic space, these four geochemical endmembers can at volcanic hotspots derive from deep-seated domains preserved in be used to define the apices of a tetrahedron (8) (Fig.
    [Show full text]
  • Relationship Between the Early Kerguelen Plume and Continental £Ood Basalts of the Paleo-Eastern Gondwanan Margins
    Earth and Planetary Science Letters 197 (2002) 35^50 www.elsevier.com/locate/epsl Relationship between the early Kerguelen plume and continental £ood basalts of the paleo-Eastern Gondwanan margins Stephanie Ingle a;Ã, Dominique Weis a;1, James S. Scoates a, Frederick A. Frey b a De¤partement des Sciences de la Terre et de l’Environnement, Universite¤ Libre de Bruxelles, P.O. Box 160/02, Ave. F.D. Roosevelt 50, B-1050 Brussels, Belgium b Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Building 54-1226, Cambridge, MA 02139, USA Received 4 June 2001; received in revised form 10 December 2001; accepted 10 January 2002 Abstract Cretaceous basalts recovered during Ocean Drilling Program Leg 183 at Site 1137 on the Kerguelen Plateau show remarkable geochemical similarities to Cretaceous continental tholeiites located on the continental margins of eastern India (Rajmahal Traps) and southwestern Australia (Bunbury basalt). Major and trace element and Sr^Nd^Pb isotopic compositions of the Site 1137 basalts are consistent with assimilation of Gondwanan continental crust (from 5 to 7%) by Kerguelen plume-derived magmas. In light of the requirement for crustal contamination of the Kerguelen Plateau basalts, we re-examine the early tectonic environment of the initial Kerguelen plume head. Although a causal role of the Kerguelen plume in the breakup of Eastern Gondwana cannot be ascertained, we demonstrate the need for the presence of the Kerguelen plume early during continental rifting. Activity resulting from interactions by the newly formed Indian and Australian continental margins and the Kerguelen plume may have resulted in stranded fragments of continental crust, isolated at shallow levels in the Indian Ocean lithosphere.
    [Show full text]
  • C"""- Signature of Author, Joint Program in Oceanography Massachusetts Institute of Technology/ Woods Hole Oceanographic Institution
    GLOBAL ISOTOPIC SIGNATURES OF OCEANIC ISLAND BASALTS by LYNN A. OSCHMANN A.B. BRYN MAWR COLLEGE (1989) SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN OCEANOGRAPHY at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY and the WOODS HOLE OCEANOGRAPHIC INSTITUTION August 1991 @Lynn A. Oschmann 1991 The author hereby grants to MIT, WHOI, and the U.S. Government permission to reproduce and distribute copies of this thesis in whole or in part. %/7_ ) C"""- Signature of Author, Joint Program in Oceanography Massachusetts Institute of Technology/ Woods Hole Oceanographic Institution Certified by - 1% Dr. Stanley R. Hart Senior Scientist, Woods Hole Oceanographic Institution Thesis Supervisor Accepted by Dr. G. Pat Lohman Chairman, Joint Committee for Geology and Geophysics, Massachusetts Institute of Technology/ Woods Hole Oceanographic Institution MVIr 2 GLOBAL ISOTOPIC SIGNATURES OF OCEANIC ISLAND BASALTS by LYNN A. OSCHMANN Submitted to the Department of Earth, Atmospheric and Planetary Sciences Massachusetts Institute of Technology and the Department of Geology and Geophysics Woods Hole Oceanographic Institution August 9, 1991 in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN OCEANOGRAPHY ABSTRACT Sr, Nd and Pb isotopic analyses of 477 samples representing 30 islands or island groups, 3 seamounts or seamount chains, 2 oceanic ridges and 1 oceanic plateau [for a total of 36 geographic features] are compiled to form a comprehensive oceanic island basalt [OIB] data set. These samples are supplemented by 90 selected mid-ocean ridge basalt [MORB] samples to give adequate representation to MORB as an oceanic basalt end-member. This comprehensive data set is used to infer information about the Earth's mantle.
    [Show full text]
  • Identification of Erosional Terraces on Seamounts
    ORIGINAL RESEARCH published: 03 July 2018 doi: 10.3389/feart.2018.00088 Identification of Erosional Terraces on Seamounts: Implications for Interisland Connectivity and Subsidence in the Galápagos Archipelago Darin M. Schwartz 1*, S. Adam Soule 2, V. Dorsey Wanless 1 and Meghan R. Jones 2 1 Department of Geosciences, Boise State University, Boise, ID, United States, 2 Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United States Shallow seamounts at ocean island hotspots and in other settings may record emergence histories in the form of submarine erosional terraces. Exposure histories are valuable for constraining paleo-elevations and sea levels in the absence of more traditional Edited by: markers, such as drowned coral reefs. However, similar features can also be produced Ricardo S. Ramalho, Universidade de Lisboa, Portugal through primary volcanic processes, which complicate the use of terraced seamounts Reviewed by: as an indicator of paleo-shorelines. In the western Galápagos Archipelago, we utilize Neil Mitchell, newly collected bathymetry along with seafloor observations from human-occupied University of Manchester, submersibles to document the location and depth of erosional terraces on seamounts United Kingdom Daneiele Casalbore, near the islands of Santiago, Santa Cruz, Floreana, Isabela, and Fernandina. We directly Sapienza Università di Roma, Italy observed erosional features on 22 seamounts with terraces. We use these observations Rui Quartau, Instituto Hidrográfico, Portugal and bathymetric analysis to develop a framework to identify terrace-like morphologic *Correspondence: features and classify them as either erosional or volcanic in origin. From this framework Darin M. Schwartz we identify 79 erosional terraces on 30 seamounts that are presently found at depths [email protected] of 30 to 300 m.
    [Show full text]
  • Three Hotspot Reference Frames – Shallow and Lithospherically Controlled – Reflect “Mesoplates”, a Plate Tectonics Heuristic
    Three Hotspot Reference Frames – Shallow and Lithospherically Controlled – Reflect “Mesoplates”, a Plate Tectonics Heuristic Submitted to: Penrose Conference- Plume IV: Beyond the Plume Hypothesis, Iceland, 2003 May 1, 2003 (Not to be circulated beyond the organizing committee) Rex H. Pilger, Jr. Landmark Graphics Corporation 1805 Shea Center Drive Suite 400 Highlands Ranch, Colorado 80129 United States of America Extended Abstract The hotspot reference frames of the Atlantic-Indian Ocean and the Pacific Ocean are kinematically distinct. Relative motion of the two reference frames in the Late Cretaceous and Early Tertiary corresponds with motion of the American plates in the Atlantic-Indian Ocean frame, suggesting a lithospheric control on the reference frames. A third reference frame, beneath Iceland and Eurasia, cannot be satisfactorily quantified at this time, but the inability to fit Iceland in either of the two other reference frames implies its existence. The two hotspot reference frames can be shown to be relatively shallow. Hotspot traces, cross- grain oceanic gravity lineations of the Pacific Ocean reflect a shallow hotspot reference frame. Intracontinental stress fields of North America correspond with the Atlantic-Indian Ocean reference frame, also reflecting a shallow reference frame. Pacific evidence: Minor hotspot island-seamount chains of the Pacific plate (Figure 1) are controlled by lithospheric structure. Almost every such trace appears to originate on the south side of a fracture zone separating older lithosphere on the north from younger lithosphere on the south. Assuming that older plate is thicker than younger plate, passage of a fracture zone separating lithosphere of contrasting age and thickness over the asthenosphere and deeper mesosphere would result in isostatic rise of affected portions of both layers.
    [Show full text]
  • Integrated 2D Geophysical Modeling Over the Juan De Fuca Plate Asif
    Integrated 2D geophysical modeling over the Juan de Fuca plate Asif Ashraf*, Irina Filina University of Nebraska-Lincoln Out of three oceanic plates subducting beneath North America along the Cascadia Subduction Zone, the Juan de Fuca (JdF) plate is the most intriguing one as it has an unusual seismicity pattern. The two other plates – the Explorer to the north and the Gorda to the south – are associated with a large number of earthquakes along the subduction zone. In contrast, JdF is seismically quiescent, so the inevitable and potentially devastating megathrust earthquake is expected in that region. To understand the tectonic complexity of the JdF subduction, it is important to understand the overall crustal architecture of the margin as well as to know physical properties (densities and magnetic susceptibilities) of the rocks of both oceanic and continental domains. Hence, we performed 2D integrated geophysical modeling along a published seismic reflection profile spanning from the Juan de Fuca spreading ridge to the High Cascades onshore. In our analysis, we have integrated multiple geophysical data from public sources, namely gravity and magnetic fields with seismic reflections and refractions. Our constructed 2D geophysical model starts from the Axial segment of the JdF spreading ridge. On the western side of the profile, gravity model requires lower densities of the mantle rocks associated with the Cobb hotspot. There are also two bathymetric seamounts near the oceanic ridge that have both gravity and magnetic signatures. Our profile crosses the pseudofault zones that require lower crustal densities with respect to adjacent oceanic crusts. We interpret this as evidence of extensive faulting in that region making the pseudofaults zones of weakness within the JdF plate.
    [Show full text]
  • Program and Abstracts
    The Atlantic Geoscience Society (AGS) La Société Géoscientifique de l’Atlantique 45th Colloquium and Annual Meeting Special Sessions: • Special Session: In Memory of Dr. Trevor MacHattie (1974 - 2018) • Paleontology and Sedimentology in Atlantic Canada: In Memory of Dr. Ron Pickerill (1947 – 2018) • Current Research in Carboniferous Geology in the Atlantic Provinces • Minerals, metals, melts, and fluids associated with granitoid rocks: new insights from fundamental studies into the genesis, melt fertility, and ore-forming processes • Earth Science Outreach in the Maritime Provinces • Geohazards: Recent and Historical General Sessions: Current Research in the Atlantic Provinces February 7-9, 2019 Fredericton Inn, Fredericton, New Brunswick PROGRAM WITH ABSTRACTS We gratefully acknowledge sponsorship from the following companies and organizations: Department of Energy and Resource Development Geological Surveys Branch Department of Energy and Mines Department of Energy and Mines Geological Surveys Division Petroleum Resources Division Welcome to the 45th Colloquium and Annual Meeting of the Atlantic Geoscience Society in Fredericton, New Brunswick. This is a familiar place for AGS, having been a host several times over the years. We hope you will find something to interest you and generate discussion with old friends and new. AGS members are clearly pushing the boundaries of geoscience in all its branches! Be sure to take in the science on the posters and the displays from sponsors, and don’t miss the after-banquet jam and open mike on Saturday night. For social media types, please consider sharing updates on Facebook and Twitter (details in the program). We hope you will be able to use the weekend to renew old acquaintances, make new ones, and further the aims of your Atlantic Geoscience Society.
    [Show full text]
  • Upper Mantle Flow Beneath and Around the Hangay Dome, Central Mongolia Guilhem Barruol, Anne Deschamps, Jacques Déverchère, Valentina V
    Upper mantle flow beneath and around the Hangay Dome, central Mongolia Guilhem Barruol, Anne Deschamps, Jacques Déverchère, Valentina V. Mordvinova, Ulziibat Munkhuu, Julie Perrot, A. Artemiev, T. Dugarmaa, Götz H.R. Bokelmann To cite this version: Guilhem Barruol, Anne Deschamps, Jacques Déverchère, Valentina V. Mordvinova, Ulziibat Munkhuu, et al.. Upper mantle flow beneath and around the Hangay Dome, central Mongolia. Earth and Planetary Science Letters, Elsevier, 2008, 274 (1-2), pp.221-233. 10.1016/j.epsl.2008.07.027. hal- 00407853 HAL Id: hal-00407853 https://hal.archives-ouvertes.fr/hal-00407853 Submitted on 24 Oct 2016 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Upper mantle flow beneath and around the Hangay dome, Central Mongolia Guilhem Barruol a,⁎, Anne Deschamps b, Jacques Déverchère c,d, Valentina V. Mordvinova e, Munkhuu Ulziibat f, Julie Perrot c,d, Alexandre A. Artemiev e, Tundev Dugarmaa f, Götz H.R. Bokelmann a a Université Montpellier II, CNRS, Géosciences Montpellier, F-34095 Montpellier cedex 5, France b Université Nice Sophia Antipolis, CNRS, Observatoire de la Côte d'Azur, Géosciences Azur, 250, Rue Albert Einstein, F-06560 Valbonne, France c Université Européenne de Bretagne, France d Université de Brest; CNRS, UMR 6538 Domaines Océaniques; Institut Universitaire Européen de la Mer, Place Copernic, 29280 Plouzané, France e Institute of the Earth's Crust SB RAS, Lermontov st.
    [Show full text]