Structural evolution of the Laurentian margin revisited (southern Quebec Appalachians): Implications for the Salinian orogeny and successor basins

K–Ar age constraints on the evolution of polydeformed fold–thrust belts: The case of the Northern Appalachians (southern Quebec)

“…The Humber zone is divided into external and internal subzones based on contrasting deformation styles and metamorphic intensities (St-Julien and Hubert, 1975;Williams, 1995;Tremblay and Castonguay, 2002). The southeast boundary between the external (EHZ) and internal (IHZ) Humber zones is defined by a series of faults exhibiting hinterlanddirected transport, collectively known as the Bennett-Brome fault in southern Quebec .…”

“…In southern Quebec, Acadian deformation and metamorphism are reported in the Cambrian-Ordovician oceanic rocks of the Iapetus track (Castonguay et al, 2001c;Tremblay and Castonguay, 2002) and in the metamorphic core of the Laurentian margin (Castonguay et al, 2001a;Tremblay and Castonguay, 2002). Acadian deformation is presumed absent in the southern Quebec allochthons (St-Julien and Hubert, 1975;Lebel and Kirkwood, 1998;Glasmacher et al, 2003), whereas it played a significant role in the construction of its counterpart in Newfoundland (cf., Waldron and Stockmal, 1991).…”

“…417-405 Ma) ages corresponding to eastward-propagating down-to-the-east extension faulting that contributed to the development and exhumation of the metamorphic core (Castonguay et al, 2007); and (3) Middle Devonian (ca. 385-375 Ma), attributed to the Acadian Orogeny and associated with folding of earlier structures (Tremblay et al, 2000;Castonguay et al, 2001c;Tremblay and Castonguay, 2002). The nature, distribution and timing of D 1-2 (Taconic), D 3 (Salinic?)…”

“…Extensive 40 Ar/ 39 Ar dating of amphibole and mica grains yielded three groups of Palaeozoic ages: (1) Middle , associated with the main D 1-2 Taconic compressional event and regional metamorphism (Castonguay et al, 2001c;Tremblay and Castonguay, 2002); (2) , associated with D 3 hinterland-directed structures in the Laurentian margin and wedging of the Grenvillian basement, followed by Late Silurian to Early Devonian (ca. 417-405 Ma) ages corresponding to eastward-propagating down-to-the-east extension faulting that contributed to the development and exhumation of the metamorphic core (Castonguay et al, 2007); and (3) Middle Devonian (ca.…”

Fossil brines preserved in the St-Lawrence Lowlands, Québec, Canada as revealed by their chemistry and noble gas isotopes

“…The St-Lawrence Lowlands is bounded by normal faults creating a half-graben commonly referred to as the St-Lawrence Rift System (Tremblay et al, 2003). Major tectonic events recorded in this region are (1) the opening of the Iapetus Ocean and the formation of the St-Lawrence Rift System around 550 Ma ago (Cawood et al, 2001); (2) the formation of the Appalachians between 470 and 360 Ma (Tremblay and Castonguay, 2002); (3) Middle-Late Jurassic reactivation of the Iapetus faults during the opening of the North Atlantic Ocean (Faure et al, 1996); and (4) a Cretaceous (124 ± 10 Ma; Eby, 1985) magmatic event that produced a series of alkaline intrusions oriented approximately WNW-ESE and referred to as the Monteregian Hills (Fig. 1a).…”