Abstract

Carbonate sedimentation occurred over most of eastern Gaspé Peninsula in Early Devonian time. The resulting succession, known as the Upper Gaspé Limestones, is a 500–1800 m thick unit outcropping in the Connecticut Valley – Gaspé Synclinorium. Detailed stratigraphic and sedimentologic work allows recognition of important thickness and lithofacies variations in a north–south-oriented transect in the eastern part of the peninsula. Variations are spatially associated with Acadian (Middle Devonian) dextral strike-slip faults. Three lithotectonic domains are proposed and interpreted; they are, from north to south, (1) a proximal outer shelf, (2) a distal, gently sloping outer shelf, and (3) a slope or slope toe. Field mapping and reinterpretation of seismic profiles from this area have shown that the faults bounding the three domains are reactivated normal listric faults. Early Devonian vertical movement along these faults caused accelerated subsidence of the central and southern segments of the sedimentary basin and is thought to be responsible for the observed Lower Devonian thickness and megafacies variations in eastern Gaspé.

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