Late Paleozoic strike-slip faults in Maritime Canada and their role in the reconfiguration of the northern Appalachian orogen

Abstract

Major late Paleozoic faults, many with documented strike-slip motion, have dissected the Ordovician-Devonian Appalachian orogen in the Maritime Provinces of Atlantic Canada. Activity alternated between east-west faults (Minas trend) and NE-SW faults (Appalachian trend). NW-SE faults (Canso trend) were probably conjugate to Minas-trend faults. Major dextral movement, on faults with Appalachian trend, in total between 200 and 300 km, began in the Late Devonian. This movement initiated the Maritimes Basin in a transtensional environment at a releasing bend formed around a promontory in the Laurentian margin and thinned the crust, accounting for the major subsidence of the basin. Appalachian-trend strike slip continued in the Mississippian but was accompanied by major movement on E-W Minas-trend faults culminating around the Mississippian-Pennsylvanian boundary, juxtaposing the Meguma and Avalon terranes of the Appalachians close to their present-day configuration. However, strike slip continued during the Pennsylvanian-Permian interval resulting in transpressional deformation that reactivated and inverted earlier extensional faults. A final major episode of transtension, mainly sinistral, occurred during the Mesozoic opening of the Atlantic Ocean. Restoration of movements on these faults, amounting to several hundred kilometers of slip, explains anomalies in the present-day distribution of terranes amalgamated during early Paleozoic Appalachian tectonism. In the restored geometry, the Nashoba and Ellsworth terranes of Ganderia are adjacent to one another, and the Meguma terrane lies clearly outboard of Avalonia. A restored post-Acadian paleogeography, not the present-day geometry of the orogen, should be used as a basis for reconstructions of its earlier Paleozoic history.

Anticosti foreland basin offshore of western Newfoundland: Concealed record of northern Appalachian orogen development

“…A distinct Neo-Acadian event was defined by Robinson, Tucker, Bradley, Berry, and Osberg (1998) to encompass strong Late Devonian to Early Carboniferous (366-350 Ma) magmatism, deformation and granulite facies metamorphism (Hibbard, van Staal, & Rankin, 2010), typically attributed to collision of the Meguma Terrane ( Figure 1a) with Laurentia ( . However, these events overlap in time with the opening of the Maritimes Basin, interpreted by Waldron, Barr, Park, White, and Hibbard (2015) as recording dextral transtension focussed at an offset in the Laurentian margin (Hibbard et al, 2010;van Staal et al, 2009;Waldron et al, 2015). In Newfoundland, Waldron et al (2015) interpreted that as much as 250 km of right-lateral motion was carried on the Cabot fault zone (CFZ on Figure 1a).…”

“…However, these events overlap in time with the opening of the Maritimes Basin, interpreted by Waldron, Barr, Park, White, and Hibbard (2015) as recording dextral transtension focussed at an offset in the Laurentian margin (Hibbard et al, 2010;van Staal et al, 2009;Waldron et al, 2015). In Newfoundland, Waldron et al (2015) interpreted that as much as 250 km of right-lateral motion was carried on the Cabot fault zone (CFZ on Figure 1a). An important implication of this deformation is that all older Laurentian and Gondwanan fragments SE of the fault were accreted ca.…”

“…These along-strike variations therefore most likely indicate greater loading in northern portions of the Newfoundland Appalachians. A palinspastic reconstruction by Waldron et al (2015) places the present-day Dashwoods block ca. To understand the source of this load it is important to note that internal parts of the orogen were strongly affected by late Paleozoic strike-slip faults.…”

The Litchfield Pluton in South-Central Maine: Carboniferous Alkalic Magmatism in northern New England, USA

“…The early Pennsylvanian age of the Lithchfield pluton corresponds to a time in the northern Appalachians that was dominated by transcurrent tectonics (Bradley 1982;Ludman and West 1999;Murphy et al 2011;Waldron et al 2015). Although the stratified and igneous rock record of this activity is largely lacking in Maine, the adjacent regions of Atlantic Canada (Maritimes Basin) and coastal southern New England (Narragansett Basin) contain thick successions of largely non-marine Carboniferous strata that were deposited in large transtensional pull-apart basins.…”

Influence of deformation and fluids on Ar retention in white mica: Dating the Dover Fault, Newfoundland Appalachians

“…Brittle slip along the broadly collinear Hermitage Bay Fault persisted into the Mississippian, likely part of a regional network of reactivated Appalachian-trend (NE-SW oriented) structures interpreted to have produced the transtensional Maritimes Basin (Waldron et al, 2015). Tables Table 1. Sample locations, methods applied Table 2.…”