Late Palaeozoic formation and development of the St Marys Basin, mainland Nova Scotia, Canada: a prolonged record of intracontinental strike-slip deformation during the assembly of Pangaea
J. B. Murphy, 2003. "Late Palaeozoic formation and development of the St Marys Basin, mainland Nova Scotia, Canada: a prolonged record of intracontinental strike-slip deformation during the assembly of Pangaea", Intraplate Strike-Slip Deformation Belts, F. Storti, R. E. Holdsworth, F. Salvini
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The Late Palaeozoic evolution of the St Marys Basin, mainland Nova Scotia, preserves evidence of protracted dextral shear along an intracontinental fault zone during collisional orogenesis and the assembly of Pangaea. The St Marys Basin formed within the E-W-trending Minas Fault Zone (MFZ) along the boundary between the Avalon and Meguma terranes and contains latest Devonian-Tournaisian continental clastic rocks that are 3000–4000 m in thickness.
The origin and evolution of the basin is attributed to either discrete or progressive dextral strike-slip tectonics along the MFZ between the Late Devonian and Late Carboniferous. Evidence for the Late Devonian origin of the basin is recorded along its southern flank by the fabrics of the deformed c. 370 Ma granites, the overall sedimentary facies distribution, and some syndepositional features within the clastic rocks. The most intense deformation within the basin is concentrated in a relatively narrow ENE-trending zone, in which predominantly fine-grained clastic rocks are deformed into periclinal folds and related reverse faults. The orientation of this zone relative to the MFZ is consistent with dextral shear. At least some of this deformation occurred after the deposition of the overlying Visean Windsor Group. The style of deformation along the present northern margin of the basin (the Chedabucto Fault) is also consistent with regional dextral shear.
The St Marys Basin is an example of basin development and evolution adjacent to an intracontinental fault zone associated with oblique convergence during orogenesis. Its evolution provides constraints on the potential relationship between the termination of the mid-Palaeozoic Acadian orogeny, subsequent basin development, and the ongoing interactions between the Avalon and Meguma terranes, and between Laurentia and Gondwana during the assembly of Pangaea. More generally, because the relationship between fabric development and motion along intracontinental strike-slip faults in continental zones is difficult to interpret, the sedimentology and structural geology in basins developed along these fault zones may preserve a less ambiguous record of the main tectonic events.
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Intraplate Strike-Slip Deformation Belts
Intraplate strike-slip deformation belts are common tectonic features, particularly at convergent plate boundaries, where they are produced by both oblique convergence and continental indentation. These lithosphere-scale structures, which also occur in other geodynamic environments such as passive margins, are characterized by complex structural architectures, by the occurrence of large earthquakes, and by the fast uplift and/or subsidence of localized crustal sectors.
Intraplate strike-slip belts can also control the ascent and emplacement of deeply sourced magmas. In some cases, intraplate strike-slip belts link with oceanic fracture zones and transform faults, transferring transform shear from the ridges to the interior of the plates. This evidence has an important impact of the classical concept of transform faulting.
This volume contains 13 papers from an international field of contributors. Studies of intraplate strike-slip deformation belts from Africa, Antarctica, Eurasia, North America and South America are included.