An ancient landslide along the Saguenay River, Quebec

LaSalle, Peggy; Chagnon, Jean-Yves

doi:10.1139/e68-049

Cited by 34 publications

(8 citation statements)

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“…Fransham et al, 1976). The ages of some individual and groups of failures are reported in the literature (e.g., Eden, 1967;Lasalle and Chagnon, 1968;Karrow, 1972;Desjardins, 1980;Rissman et al, 1985;Quilliam and Allard, 1989;Filion et al, 1991;Dionne, 1998;Aylsworth et al, 2000;Dionne et al, 2004;Cauchon-Voyer et al, 2011;Locat, 2011), but the majority of the landslides are of unknown age. Determining the age of prehistoric sensitive clay landslides can provide insights into triggering events (e.g., Aylsworth et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

A massive sensitive clay landslide, Quyon Valley, southwestern Quebec, Canada, and evidence for a paleoearthquake triggering mechanism

Brooks

2013

Quat. res.

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A landslide debris field covering ~ 31 km2, the presence of large sediment blocks up to hundreds of meters long, and the exposure of deposits of a single landslide along the incised course of the Quyon River are evidence of a massive failure of sensitive Champlain Sea glaciomarine sediments along the lower Quyon Valley, southwestern Quebec, Canada. Seventeen radiocarbon ages indicate that the failure occurred between 980 and 1060 cal yr BP. Twenty-four additional radiocarbon ages reveal that nine landslides within a 65-km belt in the Quyon"Ottawa area also occurred at approximately this time. In combination, the contemporaneous occurrence of ten landslides between 980 and 1060 cal yr BP, the setting or morphology of five of the other failures, and the close proximity of two of the failures to the Quyon Valley landslide provide circumstantial evidence of a paleoearthquake-triggering mechanism. The paleoearthquake is estimated to be Mw ~ 6.1 or larger, with the epicenter within the West Quebec Seismic Zone. A common earthquake-triggering mechanism for the three largest landslides in eastern Canada suggests a close link between massive failures of sensitive glaciomarine sediments and the regional seismicity.

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Section: Introductionmentioning

confidence: 99%

A massive sensitive clay landslide, Quyon Valley, southwestern Quebec, Canada, and evidence for a paleoearthquake triggering mechanism

Brooks

2013

Quat. res.

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“…1. Glacial clay and landslides distribution in the Province of Quebec (Chagnon 1968) 1908 (Ells 1908), or by the material damage as the slide of Nicolet in 1955 which destroyed the Archbishop's Palace, the Academy, a few residential houses and damaged the historic church to such an extent that it had to be demolished; in all, the damage in Nicolet was estimated at $5 000 000 and three lives were lost (BCland 1955, Hurtubise andRochette 1956). The largest landslide known to have occurred in the Champlain clay took place some 400 to 500 years ago in Saint-JeanVianney, on the north shore of the Rivikre Saguenay ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Regional geology and landslides in the marine clay deposits of eastern Canada

Rochelle¹,

Chagnon²,

Lefèbvre³

1970

Can. Geotech. J.

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A detailed inventory of the numerous landslides which have taken place in the Province of Quebec has shown that they are concentrated in given areas. Extensive studies carried out in three different areas have revealed a coincidence between the concentration of landslides and the existence of valleys in the bedrock underlying the clay deposits.Piezometric levels measured on the field have consistently shown the prevalence of a downward gradient in the upper part of the slope and an upward gradient with artesian pressure at the toe. These flow conditions which can be imputed in part to the presence of the valley in the bedrock produce the leaching of the salt in the pore water of the clay resulting in a decrease of the shear strength and an increase of sensitivity of the clay.Un inventaire detail16 des nombreux glissements de terrains qui se sont produits dans la Province de QuCbec a dCmontrC que ces glissements sont concentrCs dans des rCgions donnCes. Des Ctudes gkotechniques dCtaillCes exCcutCes dans trois de ces regions ont rCvClC une coincidence remarquable entre la concentration des glissements et l'existence de vallCes dans le lit rocheux sous-jacent aux dCpBts d'argile.Les niveaux piCzomCtriques mesurCs sur le terrain ont dtmontrt que, dans les trois cas CtudiCs, il existe un gradient d'Ccoulement vers le bas dans la partie supCrieure des talus et un gradient vers le haut avec pression artCsienne h la base de la pente. Ces conditions d'Ccoulement qui peuvent &tre expliquCes en partie par la prCsence d'une vallCe dans le lit rocheux produisent un lessivage du sel dans l'eau interstitielle, ce qui rCsulte en une diminution de la rtsistance au cisaillement et une augmentation de la sensibilitk de l'argile.

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“…Il semble que le mouvement de terrain aurait affecté seulement la partie externe de la terrasse Mitis, et que l'érosion littorale aurait, par la suite, effacé les traces du glissement de terrain au droit de la basse terrasse. Chagnon, 1968 ;Legget et LaSalle, 1978), de la rivière Sainte-Marguerite (Dionne, 1972b), de Saint-Joseph-de-la-Rive (Quilliam et Allard, 1989) et de Betsiamites (Bernatchez, 2003). L'âge des plus vieux échantillons est attribué à des troncs déjà morts et à de l'humus forestier à la surface du terrain affecté.…”

Section: A Lithostratigraphic Section Into the Mitis Terrace At The Eunclassified

La terrasse Mitis à la pointe de Mille-Vaches (péninsule de Portneuf), rive nord de l’estuaire maritime du Saint-Laurent : nature des dépôts et évolution du niveau marin relatif à l’holocène

Dionne

Dubois

Bernatchez

2006

gpq

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La basse terrasse à l’extrémité sud-ouest de la péninsule de Portneuf, sur la Haute Côte-Nord du Saint-Laurent, correspond à la terrasse Mitis présente dans quelques autres localités de la rive nord de l’estuaire. Entièrement composée de matériaux meubles détritiques, elle comprend plusieurs unités, la plupart sableuses, d’une épaisseur supérieure à 3 m. Mises en place en milieu littoral et intertidal, ces unités reposent sur un dépôt de sable fin gris, infratidal, lui-même susjacent au substrat limono-argileux déposé dans la Mer de Goldthwait, il y a >9,5 ka. Un dépôt de limon sableux, gris, laminé, contenant des débris de plantes en place correspondant à un faciès de schorre inférieur, coiffe la séquence sableuse. Par endroits, ce dépôt est lui-même recouvert d’une couche de tourbe de 25‑30 cm d’épaisseur. L’unité à la base de la falaise active a été mise en place entre 1990 ± 60 et 2740 ± 70 BP. Les unités sableuses au-dessus datent de 1570 ± 60 à 1880 ± 90 BP, alors que l’unité limoneuse à faciès de schorre inférieur a donné un âge au 14C allant de 1570 ± 50 à 1970 ± 70 BP. L’âge médian de la terrasse Mitis est de 1880 ± 90 BP, alors que si on prend en compte uniquement les dates pour l’unité limoneuse à faciès de schorre inférieur, il est de 1830 ± 60 BP. L’édification de la terrasse Mitis à la pointe de Mille-Vaches est donc contemporaine de la plupart des sites des deux rives de l’estuaire. Le substrat argileux de la vaste batture en face de la terrasse, qui se prolonge sous celle-ci, a été érodé lors d’un bas niveau marin pendant l’Holocène moyen qui fut suivi d’une remontée du niveau de quelques mètres. Un glissement de terrain historique, survenu vraisemblablement lors du séisme de 1663, caractérise la partie supérieure de l’estran en face de la falaise active.The low terrace at the SW extremity of the Portneuf Peninsula, on the north shore of the Lower St. Lawrence estuary, is an equivalent of the Mitis terrace occurring at a few other localities. The terrace is entirely made of detritic sediments. The various units, mostly fine to coarse sand deposited in the shore zone, are over 3 m in thickness. These sediments appear to unconformably overlie a subtidal dark grey fine sand resting on a surface eroded into a Goldthwait Sea clay deposit older than 9.5 ka. At the surface of the terrace, there is a grey, laminated sandy silt deposit with plant remains in situ (a lower marsh facies), locally covered by a thin (25‑30 cm) layer of peat. The sand unit at the base of the studied exposure has been dated 1990 ± 60 to 2740 ± 70 BP. The overlying sandy units are dated 1570 ± 60 to 1880 ± 90 BP, whereas the silt unit at the surface is dated 1570 ± 50 to 1970 ± 70 BP. The median age of the terrace is 1880 ± 90 BP, whereas if we use only the 14C dates for the silt unit, it is 1830 ± 60 BP. At Pointe de Mille-Vaches, the Mitis terrace is thus contemporaneous with most localities on both shores of the estuary. The substrate of the wide tidal flat in front of the Mitis terrace (an erosion surface underlying the terrac...

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An ancient landslide along the Saguenay River, Quebec

Abstract: The largest landslide (8 square miles) yet reported in eastern Canada is described and two 14C dates (560 ± 90 years B.P. 420 ± 90 years B.P.) believed to be related to the time of its occurrence are presented

Cited by 34 publications

References 0 publications

A massive sensitive clay landslide, Quyon Valley, southwestern Quebec, Canada, and evidence for a paleoearthquake triggering mechanism

A massive sensitive clay landslide, Quyon Valley, southwestern Quebec, Canada, and evidence for a paleoearthquake triggering mechanism

Regional geology and landslides in the marine clay deposits of eastern Canada

La terrasse Mitis à la pointe de Mille-Vaches (péninsule de Portneuf), rive nord de l’estuaire maritime du Saint-Laurent : nature des dépôts et évolution du niveau marin relatif à l’holocène

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