Transpressional structures on a Late Palaeozoic intracontinental transform fault, Canadian Appalachians

Abstract

The east-west Minas fault zone, separating the Early Palaeozoic Meguma and Avalon terranes of the Appalachians, experienced dextral strike-slip motion during the Carboniferous. Abundant oblique contractional structures indicate localized dextral transpression, immediately south of the zone, probably associated with a restraining bend. Subsurface data indicate that the deformed Horton Group clastic rocks are thrust above younger Windsor Group evaporites.Excellent exposures on wave-cut platforms of the Bay of Fundy show structures developed in transpression, including NE-trending upright and inclined folds; south-verging thrust and reverse faults; and NW-striking normal faults. Northwest-trending boudins, which are perpendicular and slightly rotated in a clockwise sense relative to fold hinges, provide a field indicator for dextral transpression. The earliest folds (F 1 ) are curvilinear and may have formed by deformation of wet sediment. F 2 tectonic folds show weak axial-planar cleavage. Locally, these have been rotated into reclined orientations; spectacular downward-facing folds are probably due to refolding by more east-west F 3 folds. The structures observed are consistent with pure-shear-dominated transpression, with the local angle of convergence a increasing over time. This strain history is compatible with progressive strain partitioning, probably associated with the spreading of topography developed at the restraining bend. Regional geological settingSouth of the Minas fault zone, the Meguma terrane is characterized by a thick (.10 km) succession of Cambrian -Ordovician metasedimentary rocks, the Meguma Group, overlain by a Late Ordovician to

Evaporite tectonics and the late Paleozoic stratigraphic development of the Cumberland basin, Appalachians of Atlantic Canada

“…Despite these arguments, McCutcheon and Robinson (1987) favored a rift model for the Maritimes Basin as a whole, whereas Martel (1987) favored a strike-slip origin for the Sackville basin, the depocenter immediately north of the Cumberland basin. Subsequent authors (e.g., Hyde et al, 1988;MacInnes and White, 2004;Waldron, 2004;Waldron et al, 2007;Murphy et al, 2011) have documented signifi cant strike-slip motion during deposition of various parts of the Maritimes Basin fi ll. Recently, Gibling et al (2008) compared the tectonic development of the Maritimes Basin with that of the eastern Mediterranean, and Hibbard and Waldron (2009) have suggested that subsidence in the Maritimes Basin was related to substantial (~250 km) dextral strike-slip motion throughout the Appalachians, which reactivated a promontory-reentrant system in the early Paleozoic Laurentian continental margin (Thomas, 1977(Thomas, , 1991 Lawrence, Grand Banks, and Cabot Strait (e.g., Durling and Marillier, 1993;Langdon and Hall, 1993;Brown, 1998;Pascucci et al, 1999).…”

Lode-gold mineralization in convergent wrench structures: Examples from South Eastern Desert, Egypt

“…thrust segments at the base of the ophiolitic blocks and steeplydipping, left lateral NNW-SSE ductile shear zones and major faults deformed most of the exposed lithologies and overprinted the preexisting lithologic/tectonic contacts. Second-order, sinistral shear zones form a positive flower structure (e.g., Clendenin, 1993;Waldron et al, 2007). The steeply dipping strike-slip fault segments bifurcate into reverse faults and then flatten into moderately dipping NNW-trending thrust zones.…”

Miocene-to-recent structure and basinal architecture along the Central Range strike-slip fault zone, eastern offshore Trinidad

“…16, inset). While the amount of convergence increases in transpression as predicted and discussed by many authors for the CRFZ, the size of the extensional sector associated with shearing gets smaller but never entirely disappears (Waldron et al, 2007) A component of right-lateral strike-slip motion cannot be ruled out for this family of linear, east-west trending faults that includes the NDRFZ. Some of these secondary faults, in conjunction with the main CRFZ, define or bound localized and elevated blocks of highly deformed pre-middle Miocene rocks (Fig.…”

“…9, 11, and 13 are oriented according to the direction of either predicted synthetic strike-slip faults or normal faults. Waldron et al (2007) has noted that extension in strike-slip and transpressional basinal settings can be a large component of the deformation and is often overlooked in outcrop settings where exposures are commonly discontinuous.…”