Revisiting the Appalachian structural front and offshore Anticosti Basin (northern Gulf of St. Lawrence, Canada) by integrating old and new geophysical datasets

The Anticosti Basin is a large, predominantly marine sedimentary basin centered within the northern Gulf of St. Lawrence. Poor-quality vintage seismic reflection data collected more than 25 years ago in the offshore part of the basin failed to depict its geometry. However, recently acquired multibeam bathymetry and magnetic data can be used in combination with high-resolution seismic lines to map the Paleozoic succession within the Honguedo Strait. The upper part of the offshore sedimentary succession consists of approximately 1140 m of sediments younger than those exposed on Anticosti Island. The offshore part of the basin includes a 40 km wide fold and fault belt sub-parallel to the coastline of the Gaspé Peninsula. The structural style is characterized by broad open synclines, narrow anticlines and NW-striking faults with dextral strike separations, which bears similarities to that of the Gaspé belt that formed mainly during the Middle Devonian Acadian Orogeny. This study indicates that the Appalachian deformation front is located to the north of its classically inferred location. Moreover, it suggests that the curvature of the early Paleozoic assemblages in the Gulf of St. Lawrence is partly a late (Devonian) feature. An improved understanding of the offshore architecture of the basin may help to develop new paleogeographic reconstructions and hydrocarbon exploration models in this under-explored frontier basin.

► The Anticosti Basin includes an ∼40 km wide fold and fault belt.
► The fold and fault belt probably formed during the Middle Devonian Acadian Orogeny.
► The contact between the Anticosti Basin and the Appalachians is displaced by NW-trending faults.
► The Honguedo Strait sedimentary succession includes ∼1140 m of sediments overlying the youngest unit preserved onshore.