Stratigraphy and geochemistry of the McGerrigle granite trains of Gaspésie, Quebec

David, Peter P.; Bédard, Pierre; Charbonneau, Rémi

doi:10.4095/122435

Cited by 3 publications

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“…The till rests over fractured (Fig. 2) or weathered bedrock (Bedard & David 1991) and, in turn, is covered by colluvium on the slopes (David et al 1988;Veillette & Cloutier 1993).…”

Section: Unconsolidated Depositsmentioning

confidence: 99%

“…2) results from slight deformation of fractured bedrock. In turn, the emplacement of the compact, massive and matrix-supported diamict which has been classified as basal till in central Gaspesie (David et al 1988) occurs after the cessation of an intense episode of shearing and homogenization of the subglacial debris by clast diffusion. Englacial debris is subsequently deposited in situ by basal melt-out process to form a fissile, matrix-supported diamict with lenses and layers of sorted material (Shaw 1982;Dreimanis 1988).…”

Section: Till Sedimentationmentioning

confidence: 99%

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A shear‐diffusion model of till genesis based on the dispersal pattern of indicator rocks in the Grand‐Volume Till of central Gaspésie, Québec, Canada

Charbonneau¹,

David²

1995

Boreas

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Dispersal patterns of indicator rocks in central Gaspésie reveal that glacial debris is entrained in a basal debris‐rich zone of shearing where clast diffusion takes place. The Grand‐Volume Till forms a thin till sheet over the high plateaus of Gaspésie Peninsula and resulted from a succession of two Wisconsinan ice flows of distinct orientations (SSE and NE). The lithological composition of this till determined by pebble counts and the three‐dimensional dispersal patterns of indicator rocks in it suggest that debris transport occurred principally by simple shear deformation of glacial debris. In addition, the intermixing of clasts at the intersection of two lithologically distinct dispersal trains of SSE and NE orientations, respectively, suggests that extensive mixing takes place during shearing. Physical interactions among the clasts lead to both upward and downward movements which cause the clasts to diffuse across the zone of shearing. This process of shear‐diffusion results in continuous incorporation and mixing of the newly encountered rock types during glacial transport.

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“…The till rests over fractured (Fig. 2) or weathered bedrock (Bedard & David 1991) and, in turn, is covered by colluvium on the slopes (David et al 1988;Veillette & Cloutier 1993).…”

Section: Unconsolidated Depositsmentioning

confidence: 99%

Section: Till Sedimentationmentioning

confidence: 99%

A shear‐diffusion model of till genesis based on the dispersal pattern of indicator rocks in the Grand‐Volume Till of central Gaspésie, Québec, Canada

Charbonneau¹,

David²

1995

Boreas

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“…In 1977, he published an important work that still constitutes the essential reference on eolian deposits in Canada (David, 1977a). Peter's research subsequently extended to dunes in upper St. Lawrence River regions of Québec (David, 1988), and to the Cree Lake and Athabasca regions of northern Sasketchewan (David, 1981a, b). From these latter studies, Peter interpreted the direction of katabatic air flow off the ice sheets at the end of the Late Wisconsinan glaciation (David, 1981a).…”

mentioning

confidence: 99%

Dedication

Bouchard¹,

Wolfe²

2002

Géographie physique et Quaternaire

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La météorisation sur les hauts plateaux de la Gaspésie (Québec) : quelques aspects

Bédard¹,

David²

2007

gpq

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Vingt-six nouveaux sites d'altérites, souvent appelées saprolites, ont été découverts sous les dépôts meubles des hauts plateaux de la Gaspésie. Ces altérites, qui appartiennent à une ancienne surface de météorisation tronquée, ont une composition minéralogique et géochimique distinctes à la fois de la roche en place et des dépôts sus-jacents. L'âge de ces altérites est probablement tertiaire. La préservation préférentielle des altérites sur les versants NNO et SSE des montagnes, c'est-à-dire en amont et en aval par rapport à l'écoulement glaciaire régional, est interprétée comme un nouvel indicateur de glaciation continentale en Gaspésie. Trois autres surfaces de météorisation stratigraphiquement plus jeunes ont été reconnues dans les dépôts sus-jacents. Ces surfaces sont: 1) la surface actuelle, 2) une surface interstadiaire et 3) une surface interglaciaire. L'âge relatif de ces surfaces de météorisation a été estimé par comparaison des caractères morphologiques, minéralogiques, géochimiques et stratigraphiques des matériaux qui leurs sont associés. 1) Les colluvions de surface, qui représentent la plus jeune surface de météorisation, n'ont été exposées qu'aux processus de météorisation postglaciaire; leurs fractions argileuses montrent un lessivage en Mn, Co1 Cu, Pb, Zn, As et U, et un enrichissement en Cr et Fe par rapport aux sédiments glaciaires sous-jacents. 2) Les dépôts de pente intertill présentent la période de météorisation précédente; ces dépôts sont formés de géli-fracts qui ne montrent aucun indice d'altération géochimique. Ils se sont formés sous un climat périglaciaire, durant un interstadiaire. 3) Les colluvions oxydées en position stratigraphique infratill représentent une troisième période de météorisation; leur degré d'altération se compare à celui des colluvions de surface exposées aux conditions climatiques actuelles et leur âge serait donc interglaciaire.Twenty-six deeply weathered bedrock occurrences, formally described as saprolites, were discovered underlying the unconsolidated sediments in the plateaux regions of Gaspésie. These occurrences, which are erosional remnants of an old weathering surface, are preferentially preserved on slopes oriented to NNW and SSE. The weathered bed rock is distinct both mineralogically and geochemically from the solid bed rock and from the overlying deposits. The age of weathering is probably Tertiary. The preservation of these occurrences on slopes oriented in upglacial and downglacial directions is a new evidence for the invasion of Gaspésie by the continental Ice Sheet. Three younger weathering surfaces were identified in the sediments overlying the weathered bed rock. They are the present-day surface, an interstadial surface and an interglacial surface. The relative age of these surfaces is based on a comparison of the morphological, mineralogical, geochemical and stratigraphie attributes of the corresponding underlying sediments. 1) The surficial colluvium which underlies the postglacial weathering surface has been partially leached of Mn, Co, Ni1 C...

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Stratigraphy and geochemistry of the McGerrigle granite trains of Gaspésie, Quebec

Cited by 3 publications

References 0 publications

A shear‐diffusion model of till genesis based on the dispersal pattern of indicator rocks in the Grand‐Volume Till of central Gaspésie, Québec, Canada

A shear‐diffusion model of till genesis based on the dispersal pattern of indicator rocks in the Grand‐Volume Till of central Gaspésie, Québec, Canada

Dedication

La météorisation sur les hauts plateaux de la Gaspésie (Québec) : quelques aspects

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