Gaspé Belt subsurface geometry in the northern Québec Appalachians as revealed by an integrated geophysical and geological study: 2 — Seismic interpretation and potential field modelling results

Abstract

Geological information, seismic reflection profiles and potential field data are used to study the geometry of the Middle Paleozoic Gaspé Belt (eastern Canada) that has been interpreted in various ways in the past. On the western edge of the Gaspé Belt, in the Matapédia area, growth strata are imaged on seismic profiles and testify of normal (or transtensional) motion during the period spanning the Silurian (and possibly Late Ordovician) to earliest Devonian along several faults, including the Shickshock–Sud Fault. In this area, Acadian deformation during the Middle to Late Devonian is associated with relatively modest shortening (less than 20%) accommodated by broad open folds, steeply-dipping neo-formed faults and inversion of previously formed faults. Neo-formed faults cut the entire Middle Paleozoic succession and offset the Ordovician Taconian unconformity suggesting that no sedimentary interval acted as an efficient décollement level. Toward the SE, the Sainte–Florence Fault divides rock assemblages with different paleogeographic settings and structural styles. Increase in tectonic complexity and amount of shortening to the south of the fault is interpreted as resulting of a vise effect between two basement blocks.