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Timing of the deformation events from Late Ordovician to Mid-Devonian in the Gaspé Peninsula

By
Michel Malo
Michel Malo
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Pierre-André Bourque
Pierre-André Bourque
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Published:
January 01, 1993

The Middle Paleozoic rocks deformed by the Acadian orogeny in the Gaspé Peninsula are divided into three major structural zones, from north to south: (1) the Connecticut Valley-Gaspé synclinorium, (2) the Aroostook-Percé anticlinorium, and (3) the Chaleurs Bay synclinorium. These three structural zones were part of a single depositional belt, the Gaspé Belt, located mainly to the south of the Baie Verte-Brompton Line over the Dunnage Zone.

The Gaspé Belt comprises four broad temporal and lithological packages: (1) Upper Ordovician-lowermost Silurian deep water fine-grained siliciclastic and carbonate fades, (2) Silurian-lowermost Devonian shallow to deep shelf fades, (3) Lower Devonian mixed siliciclastic and carbonate fine-grained deep shelf and basin facies, and (4) upper Lower to Upper Devonian nearshore to terrestrial coarse-grained facies. Upper Ordovician to Middle Devonian rocks of the Gaspé Belt are bracketed between the Taconian and the Acadian unconformities, whereas the Salinic unconformity is well recorded in the Gaspé Belt sequence. Three shallowing-upward phases, separated by two transgressive episodes, are recorded by the sequence, the shallowing phases occurring more or less in response to three tectonic pulses: the Middle to Late Ordovician Taconian orogeny, the Late Silurian Salinic disturbance, and the Middle Devonian Acadian orogeny.

The major structural trend of the Late Ordovician to Middle Devonian rocks of the Gaspé Belt is oriented roughly northeast. Major easterly striking dextral strike-slip faults (in the southeastern Aroostook-Percé anticlinorium) and northwesterly striking faults (in the northeastern Connecticut Valley-Gaspé synclinorium) transect this trend, whereas northeasterly striking high-angle reverse faults are present in the western and central regions. Two phases of folding are recorded in the Gaspé Belt. Northwest-southeast-striking F1 folds recognized mainly in the Aroostook-Percé anticlinorium and synsedimentary faulting along the northwesterly trending faults of the northeastern Connecticut Valley-Gaspé synclinorium that affect the Silurian part of the sequence may be related to the Salinic disturbance. The northeast-southwest-striking F2 folds correspond to the major Acadian structural trend of the Gaspé Peninsula. Structural features related to the D2 deformation can be integrated in a model of strike-slip tectonics. Shortening of the cover rocks of the Gaspé Belt and transcurrent motion along the major easterly striking strike-slip faults are related to local transpression in the northeastern part of the Québec Reentrant during the continued continental convergence and accretion of outboard terranes to the North American craton in post-Middle Devonian and pre-Carboniferous time.

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GSA Special Papers

The Acadian Orogeny: Recent Studies in New England, Maritime Canada, and the Autochthonous Foreland

David C. Roy
David C. Roy
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James W. Skehan
James W. Skehan
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Geological Society of America
Volume
275
ISBN print:
9780813722757
Publication date:
January 01, 1993

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