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The Panafrican and Cadomian Orogenies in North Africa and Western Europe

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The Panafrican and Cadomian Orogenies in North Africa and Western Europe International Meeting July 1st, 2021 (online) THE PANAFRICAN AND CADOMIAN OROGENIES IN NORTH AFRICA AND WESTERN EUROPE J. Javier Álvaro, Martim Chichorro and Gabriel Gutiérrez-Alonso (eds.) 1 (cover photo: panorama of microbial-Cloudina reefs in Villarta de los Montes, Central Iberian Zone) Álvaro, J.J., Chichorro, M. and Gutiérrez-Alonso, G. 2021. The Panafrican and Cadomian orogenies in North Africa and Western Europe. IGEO ed., Madrid. 2 Aims of the meeting The scientific sessions will be focused on the Pan-African and Cadomian Orogenies recorded in North Africa and western Europe across the Ediacaran- Cambrian transition and its bearing in the assembly and demise of Pannotia. Contributions dealing with structural, magmatic, provenance sources, palaeomagnetic, sedimentary, chronostratigraphic and radiometric constraints are particularly welcome. Meeting date July 1st, 2021 (online) Organizing Committee J. Javier Álvaro, Instituto de Geociencias (CSIC-UCM), Spain Martim Chichorro, Universidade Nova de Lisboa, Portugal Gabriel Gutiérrez-Alonso, Universidad de Salamanca, Spain Contributions to IGCP Projects 648 - Supercontinent Cycles and Global Geodynamics 683 - Pre-Atlantic geological connections among northwest Africa, Iberia and eastern North America 3 Table of contents pages 1. List of participants 5 2. Timetable for presentations 6 3. Abstracts of presentations 7 4 1. LIST OF PARTICIPANTS ALVES Paulo Hagendorn - LNEG Estrada da Portela, Bairro Zambujal Ap.7586 Alfragide 2610-999 Amadora, Portugal, [email protected] ÁLVARO J. Javier – Instituto de Geociencias (CSIC-UCM), Dr. Severo Ochoa 7, 28040 Madrid, Spain, [email protected] AMARAL João Lains Instituto Dom Luiz (IDL), Ed. C1, Piso 1, Campo Grande, 1749- 016 Lisboa, Portugal, [email protected] BARR Sandra - Department of Earth & Environmental Science, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada, [email protected] BELKACIM Saïd - Laboratoire de Géologie Appliquée et Géo-Environnement, Université Ibn Zohr, Faculté des Sciences, Département de Géologie, B.P 8106, Cité Dakhla, 80 000 Agadir, Morocco, [email protected] CASAS Josep Maria – Departament de Dinàmica de la Terra i de l’Oceà, Universitat de Barcelona, Martí Franquès s/n, 08028 Barcelona, Spain, [email protected] CHICHORRO Martim - GEOBIOTEC, Departamento de Ciências da Terra, Universidade Nova de Lisboa, Portugal, [email protected] DAMIAN Nance – Department of Geological Sciences, Ohio University, Athens, Ohio 45701, USA, [email protected] GUTIÉRREZ-ALONSO Gabriel - Departamento de Geología, Universidad de Salamanca, Plaza de los Caídos s/n, 37008 Salamanca, Spain, gabi@usal HENRIQUES Susana, Laboratório Nacional de Energia e Geologia, I.P., Estrada da Portela, Bairro do Zambujal – Alfragide, Apartado 7586 - 2610-999 Amador, Portugal, [email protected] JACQUES, Dominique, KU Leuven, Department of Earth and Environmental Sciences, Celestijnenlaan 200E, B-3001 Heverlee, Belgium, [email protected] JOHNSTON Stephen T. - Deptartment of Earth & Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada, [email protected] KUIPER Yvette D., Department of Geology and Geological Engineering, Colorado School of Mines, 1516 Illinois Street, Golden CO 80401, USA, [email protected] LINNEMANN Ulf - Senckenberg Natural History Collections Dresden, Museum of Mineralogy and Geology, Königsbrücker Landstraße 159, D-01109 Dresden, Germany, [email protected] LÓPEZ CARMONA Alicia – Facultad de Ciencias Geológicas, José Antonio Novais 12, 28040 Madrid, [email protected] PADEL Maxime - Bureau de Recherches Géologiques et Minières (BRGM), 23 Avenue Claude Guillemin, 45100 Orléans, France, [email protected] QUESADA Cecilio – Instituto Geológico y Minero de España, Ríos Rosas 23, 28003 Madrid, Spain, [email protected] ROJO Esther – Facultad de Ciencias Geológicas, José Antonio Novais 12, 28040 Madrid, [email protected] SOLÁ Rita - Laboratório de Geologia e Minas, Unidade de Geologia e Cartografia Geológica, Estrada da Portela s/n, Zambujal, Alfragide, 2610-999 Amadora, Portugal, [email protected] STERN Robert, Department of Geosciences, University of Texas, Dallas, USA, [email protected] 5 2. TIMETABLE FOR PRESENTATIONS July 1st, 2021 (GMT + 2, Time in Madrid-Berlin) TALKS (15 + 5 min. for questions) 15.00-15.20 h. Linnemann et al. The Cadomian orogeny: where, when, and how? 15.20-15.40 h. Quesada. The Cadomian Orogen in Iberia 15.40-16.00 h. Chichorro et al. ~ 610 Ma: a critical age for the Iberian consolidation. 16.00-16.20 h. Gutiérrez-Alonso et al. Why is there not a Cadomian "true" basement in western Europe? (or where is it?) 16.20-16.40 h. Amaral. Inspecting zircon populations of the Iberian Pyrite Belt: tracking the Cadomian record of the South Portuguese Zone 16.40-17.00. Henriques et al. Evolution of a Neoproterozoic suture in the Iberian Massif, Central Portugal: igneous and metamorphic events at the Ossa Morena Zone/Central Iberian Zone boundary 17.00-17.20 h. Coffee/tea break 17.20-17.40 h. Álvaro. Late Ediacaran tectono-sedimentary evolution of the Cadomian retro-arc basin preserved in the Central Iberian Zone, Iberian Massif 17.40-18.00 h. Casas et al. Cadomian metabasites of the Pyrenees revisited: new geochemical and geochronological data 18.00-18.20 h. Jacques et al. Redefining the Central Iberian Zone (Iberian Massif): a tectonic subdivision traced by the Alcudian unconformity 18.20-18.40 h. Rojo-Pérez et al. Geochemical and isotopic (Nd) correlation between SW Iberian and N Bohemian Late Ediacaran siliciclastic series. 18.40-19.00 h. López Carmona et al. The Panafrican basement in Morocco: age and P-T evolution of the Zenaga inlier 19.00-19.20 h. Padel et al. Shifts in the Cadomian detrital zircon populations of the Cantabrian-Occitan-Pyrenean-Sardinian margin fringing West Gondwana 19.20-20.00 h. Choral discussion about: lack of Mesoproterozoic outcrops in Iberia, so many suture segments (which is a real ophiolite?), and future topics 6 3. ABSTRACTS OF PRESENTATIONS Late Ediacaran tectono-sedimentary evolution of the Cadomian retro-arc basin preserved in the Central Iberian Zone, Iberian Massif J. Javier Álvaro Instituto de Geociencias (CSIC-UCM), Madrid, Spain, [email protected] Retroarc foreland basins, which form behind continental margin arc systems, are mainly filled with terrigenous sediments derived from the neighbouring fold-thrust belt behind the arc. A key element in this kind of basin infill is the syntectonic character of the sediments and the fact that the proximal basin margin currently becomes involved with the propagating fold-thrust belt. Pro- gressive unroofing in the fold-thrust belt is accompanied by “cannibalistic” resedimentation of marine slope-related deposits. In some cases, recycling of uplifted non-marine sediments can led to their virtual disappearance, which contrasts with the preservation of distal marine sedi- ments disconnected from proximal alluvial-fan and fluvial sediments. The latest Ediacaran metasedimentary rocks in the Central-Iberian Zone of the Iberian mas- sif were deposited in a retro-arc setting, following ophiolite obduction, uplift and erosion. Marine slope-related conditions were established in the basin, which accommodated a thick succession of variously coarse-grained conglomeratic to shaly sediments, locally burrowed and lithostrati- graphically recognized as the Cíjara Formation. By including all the observed facies associa- tions, a depositional model that do not require a eustasy-driven sequence-stratigraphic model for explanation can be invoked, lacking any preservation of coeval non-marine sediments as a result of active fold-thrust propagation. The episodic occurrence of carbonate clasts provides evidence for intervals of carbonate production fringing the basin margin and far from the Ca- domian source of debris. Contemporaneous episodes of microbial and shelly carbonate produc- tivity are represented by the Villarta Formation (Ibor Group), characterized by pulses of car- bonate nucleation on an assemblage of uplifted platform-blocks. The Cloudina-microbial build- ups of the lower Villarta Member have yielded, after acid etching, specimens of Cloudina, Sino- tubulites and Protolagena, whereas vendotaenids are relatively common in the shale interbeds of the same member, and sabelliditids are abundant in the shale interbeds of the second mem- ber. The end of the orogen is related to the onset of a pre-rift unconformity, sealing an inherited palaeorelief of folded and tilted sedimentary packages, and representing the intra-Terreneuvian Cadomian orogenic collapse in this margin of Gondwana. 7 Inspecting zircon populations of the Iberian Pyrite Belt: tracking the Cadomian record of the South Portuguese Zone João Lains Amaral1,2, Ana Rita Solá2, Telmo M. Bento dos Santos1 1Instituto Dom Luiz (IDL), Ed. C1, Piso 1, Campo Grande, 1749-016 Lisboa, Portugal. 2Laboratório Nacional de Energia e Geologia (LNEG), Bairro do Zambujal, Apartado 7586, Alfragide, 2610- 999 Amadora, Portugal. The palaeogeographic location of the southernmost zone of the Iberian Massif, the South Portuguese Zone (SPZ), prior to the amalgamation of Pangaea is still a matter of debate. In this work, we attempt to track its palaeogeographic setting during the final stages of the Cadomian Cycle. This is a challenging task as rocks older than middle Devonian have not yet been found. A compilation of published U-Pb geochronological data of the SPZ shows a strong Cadomian signature (25-50%) in both Devonian and Carboniferous
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