Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya)
International audience Fromthe Proterozoic to the Quaternary, the evolution of the Earthwas characterised by recurrent periods of glaciation.However, the margins of many ancient ice-sheets are poorly defined on palaeogeographic reconstructions.The extent and outlines of ancient ice sheets can be bet...
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ftunivnantes:oai:HAL:insu-01184739v1 2023-05-15T16:40:26+02:00 Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya) Girard, Flavia Ghienne, Jean-François Du-Bernard, Xavier Rubino, Jean-Loup Géosciences Montpellier Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA) Institut de physique du globe de Strasbourg (IPGS) Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS) Centre scientifique et Technique Jean Feger (CSTJF) TOTAL FINA ELF ANR-12-BS06-0014,SeqStrat-Ice,Les glaciations du passé: leçons pour un modèle de stratigraphie séquentielle dédié aux systèmes glaciaires(2012) 2015 https://hal-insu.archives-ouvertes.fr/insu-01184739 https://doi.org/10.1016/j.earscirev.2015.06.006 en eng HAL CCSD Elsevier info:eu-repo/semantics/altIdentifier/doi/10.1016/j.earscirev.2015.06.006 insu-01184739 https://hal-insu.archives-ouvertes.fr/insu-01184739 doi:10.1016/j.earscirev.2015.06.006 ISSN: 0012-8252 Earth-Science Reviews https://hal-insu.archives-ouvertes.fr/insu-01184739 Earth-Science Reviews, Elsevier, 2015, pp.259-289. ⟨10.1016/j.earscirev.2015.06.006⟩ Murzuq Basin Hirnantian glaciation Ice front Tunnel valleys Glaciotectonic Supercritical flows [SDU]Sciences of the Universe [physics] info:eu-repo/semantics/article Journal articles 2015 ftunivnantes https://doi.org/10.1016/j.earscirev.2015.06.006 2022-10-12T00:03:34Z International audience Fromthe Proterozoic to the Quaternary, the evolution of the Earthwas characterised by recurrent periods of glaciation.However, the margins of many ancient ice-sheets are poorly defined on palaeogeographic reconstructions.The extent and outlines of ancient ice sheets can be better understood through careful documentation ofsediments deposited at the ice-sheet margin. An outstanding example is provided herein based on an end-Ordovician archive in Libya (Tihemboka area, Murzuq Basin). The four sets of structures include: i) subglacialglaciotectonic structures and soft sediment deformations from flowing glacier ice, such as intraformational glacialstriae, intraformational deformation (shear planes, sheath folds), normal microfaults, and large-scaleglaciotectonic folds-and-thrusts; (ii) structures resulting from overpressured subglacial (meltwater) flowssuch as clastic dykes and tunnel valleys; (iii) proglacial depositional structures and facies related to highmagnitudemeltwater floods such as sandstone intraclasts, large-scale bedforms resulting from supercriticalflows, climbing-dune cross-stratification and kettle holes; and (iv) deformation structures resulting from freefloating and nonglacier ice such as ice-keel scours and ice-crystal marks. Such a set of structures points to anice-marginal (essentially continental) depositional setting, and provides an excellent suite of criteria to identifymargins of ancient ice sheets in the stratigraphic record. At a regional scale, a reconstruction through time andspace of the related depositional wedge is proposed. This corresponded to a seismic-scale (N120 m in thickness,40 km in length) ice-marginal wedge in front of an essentially warm-based ice-sheet inducing concomitantlarge-scale glaciotectonic deformation, glacial basin and tunnel valley downcuttings. The related ice-front wasassociated with high-energy meltwater flows feeding a network of deeply incised proglacial channels downstreamand, beyond them, a fluvioglacial deltaic system. Shallow ... Article in Journal/Newspaper Ice Sheet Université de Nantes: HAL-UNIV-NANTES Earth-Science Reviews 148 259 289 |
institution |
Open Polar |
collection |
Université de Nantes: HAL-UNIV-NANTES |
op_collection_id |
ftunivnantes |
language |
English |
topic |
Murzuq Basin Hirnantian glaciation Ice front Tunnel valleys Glaciotectonic Supercritical flows [SDU]Sciences of the Universe [physics] |
spellingShingle |
Murzuq Basin Hirnantian glaciation Ice front Tunnel valleys Glaciotectonic Supercritical flows [SDU]Sciences of the Universe [physics] Girard, Flavia Ghienne, Jean-François Du-Bernard, Xavier Rubino, Jean-Loup Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya) |
topic_facet |
Murzuq Basin Hirnantian glaciation Ice front Tunnel valleys Glaciotectonic Supercritical flows [SDU]Sciences of the Universe [physics] |
description |
International audience Fromthe Proterozoic to the Quaternary, the evolution of the Earthwas characterised by recurrent periods of glaciation.However, the margins of many ancient ice-sheets are poorly defined on palaeogeographic reconstructions.The extent and outlines of ancient ice sheets can be better understood through careful documentation ofsediments deposited at the ice-sheet margin. An outstanding example is provided herein based on an end-Ordovician archive in Libya (Tihemboka area, Murzuq Basin). The four sets of structures include: i) subglacialglaciotectonic structures and soft sediment deformations from flowing glacier ice, such as intraformational glacialstriae, intraformational deformation (shear planes, sheath folds), normal microfaults, and large-scaleglaciotectonic folds-and-thrusts; (ii) structures resulting from overpressured subglacial (meltwater) flowssuch as clastic dykes and tunnel valleys; (iii) proglacial depositional structures and facies related to highmagnitudemeltwater floods such as sandstone intraclasts, large-scale bedforms resulting from supercriticalflows, climbing-dune cross-stratification and kettle holes; and (iv) deformation structures resulting from freefloating and nonglacier ice such as ice-keel scours and ice-crystal marks. Such a set of structures points to anice-marginal (essentially continental) depositional setting, and provides an excellent suite of criteria to identifymargins of ancient ice sheets in the stratigraphic record. At a regional scale, a reconstruction through time andspace of the related depositional wedge is proposed. This corresponded to a seismic-scale (N120 m in thickness,40 km in length) ice-marginal wedge in front of an essentially warm-based ice-sheet inducing concomitantlarge-scale glaciotectonic deformation, glacial basin and tunnel valley downcuttings. The related ice-front wasassociated with high-energy meltwater flows feeding a network of deeply incised proglacial channels downstreamand, beyond them, a fluvioglacial deltaic system. Shallow ... |
author2 |
Géosciences Montpellier Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA) Institut de physique du globe de Strasbourg (IPGS) Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS) Centre scientifique et Technique Jean Feger (CSTJF) TOTAL FINA ELF ANR-12-BS06-0014,SeqStrat-Ice,Les glaciations du passé: leçons pour un modèle de stratigraphie séquentielle dédié aux systèmes glaciaires(2012) |
format |
Article in Journal/Newspaper |
author |
Girard, Flavia Ghienne, Jean-François Du-Bernard, Xavier Rubino, Jean-Loup |
author_facet |
Girard, Flavia Ghienne, Jean-François Du-Bernard, Xavier Rubino, Jean-Loup |
author_sort |
Girard, Flavia |
title |
Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya) |
title_short |
Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya) |
title_full |
Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya) |
title_fullStr |
Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya) |
title_full_unstemmed |
Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya) |
title_sort |
sedimentary imprints of former ice-sheet margins: insights from an end-ordovician archive (sw libya) |
publisher |
HAL CCSD |
publishDate |
2015 |
url |
https://hal-insu.archives-ouvertes.fr/insu-01184739 https://doi.org/10.1016/j.earscirev.2015.06.006 |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_source |
ISSN: 0012-8252 Earth-Science Reviews https://hal-insu.archives-ouvertes.fr/insu-01184739 Earth-Science Reviews, Elsevier, 2015, pp.259-289. ⟨10.1016/j.earscirev.2015.06.006⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.earscirev.2015.06.006 insu-01184739 https://hal-insu.archives-ouvertes.fr/insu-01184739 doi:10.1016/j.earscirev.2015.06.006 |
op_doi |
https://doi.org/10.1016/j.earscirev.2015.06.006 |
container_title |
Earth-Science Reviews |
container_volume |
148 |
container_start_page |
259 |
op_container_end_page |
289 |
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1766030825815539712 |