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Advance and Retreat of Cordilleran Ice Sheets in Washington, U.S.A

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Advance and Retreat of Cordilleran Ice Sheets in Washington, U.S.A Document généré le 4 oct. 2021 19:12 Géographie physique et Quaternaire Advance and Retreat of Cordilleran Ice Sheets in Washington, U.S.A. Avancée et recul des inlandsis de la Cordillère dans l’État de Washington (É.-U.) Vorstoß und Rückzug der Kordilleren-Eisdecke in Washington State. U.S.A. Don J. Easterbrook Volume 46, numéro 1, 1992 Résumé de l'article Dans la Cordillère, les glaciations se sont produites selon des modes URI : https://id.erudit.org/iderudit/032888ar caractéristiques d'avancée et de recul : 1) dépôts fluvioglaciaires d'avancée; 2) DOI : https://doi.org/10.7202/032888ar poli glaciaire; 3) till; 4) dépôts fluvio-glaciaires de retrait au sud de Seattle, dans le sud des basses-terres de Puget, dépôts glacio-marins dans les basses-terres Aller au sommaire du numéro du nord, et eskers, terrasses fluvioglaciaires et petites moraines sur le plateau de Columbia. La datation au radiocarbone indique que les lobes de Puget et de Juan de Fuca ont avancé et reculé synchroniquement. Parmi les preuves qui Éditeur(s) nous contraignent à rejeter l'hypothèse selon laquelle un front en fusion, qui vêlait, serait à l'origine des dépôts glacio-marins, citons : 1) les nombreuses Les Presses de l'Université de Montréal datations au radiocarbone qui révèlent la mise en place simultanée de dépôts glacio-marins sur tout le territoire; 2) les dépôts issus de la fusion de la glace ISSN stagnante, intimement associés aux dépôts glacio-marins; 3) les preuves irréfutables d'une origine autre que marine des sables de Deming qui révèlent 0705-7199 (imprimé) que la Cordillère était libre de glace immédiatement avant la mise en place des 1492-143X (numérique) dépôts glacio-marins. Dans le nord des basses-terres de Puget le déroulement des événements comprend les étapes suivantes : 1) au cours du maximum de Découvrir la revue Vashon, charge glaciaire sous 1800 m de glace; 2) 12-13 ka BP, amincissement rapide du glacier et dérive de la glace contribuant à la mise en place des dépôts glacio-marins de Kulshan; 3) vers 11 500 ans BP, emersion et dépôt des sables Citer cet article de Deming d'origine fluviale; 4) nouvelle submersion et mise en place des dépôts glacio-marins de Bellingham jusqu'à une hauteur d'environ 200 m, bien Easterbrook, D. J. (1992). Advance and Retreat of Cordilleran Ice Sheets in supérieure à l'élévation eustatique du niveau de la mer; 5) vers 10 500-11 500 Washington, U.S.A. Géographie physique et Quaternaire, 46(1), 51–68. ans BP, emersion et mise en place des dépôts fluvio-glaciaires de Sumas sur les https://doi.org/10.7202/032888ar dépôts glacio-marins de Bellingham; 6) à l'Holocène, élévation eustatique du niveau de la mer au même rythme que le relèvement isostatique. Tous droits réservés © Les Presses de l'Université de Montréal, 1992 Ce document est protégé par la loi sur le droit d’auteur. L’utilisation des services d’Érudit (y compris la reproduction) est assujettie à sa politique d’utilisation que vous pouvez consulter en ligne. https://apropos.erudit.org/fr/usagers/politique-dutilisation/ Cet article est diffusé et préservé par Érudit. Érudit est un consortium interuniversitaire sans but lucratif composé de l’Université de Montréal, l’Université Laval et l’Université du Québec à Montréal. Il a pour mission la promotion et la valorisation de la recherche. https://www.erudit.org/fr/ Géographie physique et Quaternaire, 1992, vol. 46, n° 1, p. 51-68, 22 fig., 1 tabl. ADVANCE AND RETREAT OF CORDILLERAN ICE SHEETS IN WASHINGTON, U.S.A.* Don J. EASTERBROOK, Department of Geology, Western Washington University, Bellingham, Washington 98225, U.S.A. ABSTRACT Cordilleran Ice Sheet glacia­ RÉSUMÉ Avancée et recul des inlandsis de ZUSAMMENFASSUNG VorstoB und tions show characteristic patterns of advance la Cordillère dans l'État de Washington (É.-U). Rùckzug der Kordilleren-Eisdecke in and retreat, consisting of (1) advance out- Dans la Cordillère, les glaciations se sont pro­ Washington State. U.S.A. Die Vereisung der wash, (2) glacial scouring, (3) deposition of till, duites selon des modes caractéristiques Kordilleren-Eisdecke zeigt charakteristische (4) deposition of recessional outwash south of d'avancée et de recul: 1) dépôts fluvio­ VorstoB- und Rùckzugsmuster, bestehend Seattle in the southern Puget Lowland, glacio­ glaciaires d'avancée; 2) poli glaciaire; 3) till; aus (1) glazialem SchwemmvorstoB, (2) gla- marine drift in the northern lowland, and 4) dépôts fluvio-glaciaires de retrait au sud de zialem Scheuern, (3) Ablagerung der eskers, kames, and small moraines on the Seattle, dans le sud des basses-terres de Grundmoràne, (4) Ablagerung von Rùck- Columbia Plateau. Radiocarbon dates show Puget, dépôts glacio-marins dans les basses- zugsschwemm-Material sùdlich von Seattle that the Puget and Juan de Fuca lobes terres du nord, et eskers, terrasses fluvio­ im sûdlichen Puget-Lowland, glaziomarines advanced and retreated synchronously. The glaciaires et petites moraines sur le plateau Material im nôrdlichen Tiefland und Esker, Puget lobe backwasted to Seattle by de Columbia. La datation au radiocarbone Kames und kleine Morànen auf dem 13.4-14 kayrs BP, where the thinning ice indique que les lobes de Puget et de Juan de Columbia-Plateau. Radiokarbondaten zeigen, floated in seawater northward to Canada by Fuca ont avancé et reculé synchroniquement. daf3 die Puget — und Juan de Fuca-Loben 13 kayrs BP depositing glaciomarine drift Parmi les preuves qui nous contraignent à gleichzeitig vorstieBen und sich zurûckzogen. contemporaneously over 18,000 km2. Com­ rejeter l'hypothèse selon laquelle un front en Gegen das rùcklàufige, kalbende Terminus- pelling evidence against the backwasting, fusion, qui vêlait, serait à l'origine des dépôts Modell fur den Ursprung des glaziomarinen calving, terminus model for the origin of the glacio-marins, citons: 1) les nombreuses data­ Materials sprechen die folgenden Tatsachen glaciomarine drift includes: 1) abundant 14C tions au radiocarbone qui révèlent la mise en in zwingender Weise: 1) zahlreiche '"C-Daten dates demonstrate simultaneous deposition of place simultanée de dépôts glacio-marins sur beweisen die gleichzeitige Ablagerung von glaciomarine drift over the entire area; tout le territoire; 2) les dépôts issus de la glaziomarinem Material ùber das gesamte 2) stagnant-ice deposits closely related to gla­ fusion de la glace stagnante, intimement asso­ Gebiet; 2) Ablagerungen von stagnierendem ciomarine drift are not consistent with an ciés aux dépôts glacio-marins; 3) les preuves Eis, die in enger Verbindung zu glaziomari­ actively-calving, backwasting terminus; irréfutables d'une origine autre que marine des nem Material stehen, stimmen nicht mit einem 3) irrefutable evidence for the nonmarine ori­ sables de Deming qui révèlent que la aktiv kalbenden rùcklàufigen Terminus gin of Deming sand shows that Cordilleran ice Cordillère était libre de glace immédiatement ùberein; 3) unwiderlegbares Beweismaterial was absent immediately prior to deposition of avant la mise en place des dépôts glacio- fur den nichtmarinen Ursprung des Sands von the overlying glaciomarine drift. The pattern marins. Dans le nord des basses-terres de Deming zeigt, daB es kein Kordilleren-Eis gab of events in the northern Puget Lowland Puget le déroulement des événements com­ unmittelbar vor der Ablagerung darùberliegen- includes: 1) glacial loading under 1800 m of prend les étapes suivantes: 1) au cours du den glaziomarinen Materials. Die Abfolge der ice during the Vashon maximum; 2) rapid gla­ maximum de Vashon, charge glaciaire sous Ereignisse im nôrdlichen Puget Lowland bein- cial thinning and floating of the ice deposited 1800 m de glace; 2) 12-13 ka BP, amincisse­ haltet: 1)glaziale Fracht unter 1800 m Eis Kulshan glaciomarine drift 12-13 ka yrs BP; ment rapide du glacier et dérive de la glace wàhrend des Vashon Maximums; 2) schnelles 3) emergence and deposition of fluvial contribuant à la mise en place des dépôts glaziales Ausdùnnen und treibendes Eis Deming sand -11.5 ka yrs BP; 4) resubmer- glacio-marins de Kulshan; 3) vers 11 500 ans lagerte 12-13 ka Jahre v.u.Z. das glazioma- gence and deposition of Bellingham glacioma­ BP, emersion et dépôt des sables de Deming rine Material von Kulshan ab; 3) Auftauchen rine drift up to -200 m, well beyond global d'origine fluviale; 4) nouvelle submersion et und Ablagerung von Deming-FluBsand eustatic sea level rise; 5) emergence mise en place des dépôts glacio-marins de -11.5ka Jahre v.u.Z.; 4) Wieder- -10.5-11.5 ka yrs BP and deposition of Bellingham jusqu'à une hauteur d'environ untertauchen und Ablagerung von glazioma­ Sumas outwash on Bellingham glaciomarine 200 m, bien supérieure à l'élévation eusta- rinem Belligham-Material bis zu - 200 m, weit drift; 6) Holocene eustatic sea level rise kept tique du niveau de la mer; 5) vers 10 500- ùber die globale eustatische Meeresan- pace with isostatic rebound, thus, post-Sumas 11 500 ans BP, emersion et mise en place hebung hinaus; 5) Auftauchen - 10.5-11.5 ka marine terraces are absent. des dépôts fluvio-glaciaires de Sumas sur les Jahre v.u.Z. und Ablagerung von Sumas- dépôts glacio-marins de Bellingham; 6) à l'Ho- Schwemm-Material auf dem glaziomarinen locène, élévation eustatique du niveau de la Bellingham-Material; 6) die eustatische mer au même rythme que le relèvement Anhebung des Meeresspiegels im Holozàn isostatique. hielt Schritt mit dem isostatischen Ruckprall. * The present article is a follow up to the special issue dedicated to the Cordilleran Ice Sheet (Vol. 45, No. 3) / Cet article constitue la suite du numéro spécial consacré à l'Inlandsis de la Cordillère (vol. 45, n° 3). Manuscrit reçu le 11 mars 1991; manuscrit révisé accepté le 22 octobre 1991 52 D. J. EASTERBROOK INTRODUCTION in accord with one another.
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