Abstract

In the Appalachians of southern Quebec, the contact between Siluro-Devonian rocks of the Connecticut Valley – Gaspé Synclinorium and the Cambro-Ordovician rocks of the Dunnage Zone is marked by an important thrust fault striking northwest, La Guadeloupe fault. This fault separates two stratigraphically distinct domains, but the regional deformations are related to the same orogenic period. In the Sherbrooke and Weedon areas, different structural features show evidence of La Guadeloupe fault and reveal its kinematics. The exposed rocks near the fault exhibit structures that indicate a strong deformation zone. The deformation includes well-developed stretching lineations and shearing zones. The ductile deformation is restricted to the Cambro-Ordovician rocks. Macroscopic and microscopic studies of samples from the shear zones related to La Guadeloupe fault reveal, systematically, a tectonic transport from southwest to northwest. This interpretation is supported by the quartz crystallographic c-axis orientation. In New England, La Guadeloupe fault seems to coincide with the Taconic unconformity, though a bifurcation of the pre-Silurian units exposed on the western side of this unconformity remains possible. In Quebec, the correlation and kinematics of La Guadeloupe fault extension towards the northeast are not completely understood. [Journal Translation]

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