Abstract Metamorphic and plutonic basement rocks and cover sequences of the Eastern Sierras Pampeanas, Argentina, have undergone multiple episodes of fault reactivation. Faults take advantage of mid- to late Cambrian, NW-SE-striking, steeply east-dipping foliations in Vendian-aged accretionary prism metasedimentary rocks. Foliations in peraluminous schists, paragneisses and migmatites are deflected into late Cambrian amphibolite-grade high-strain zones. Greenschist-grade mylonite zones and thick retrogressed ultramylonite zones with mainly NNW strikes, easterly dips, and east-over-west movement, affect the metasedimentary rocks and Ordovician-aged intrusive rocks and are presumably related to early Devonian accretion of terranes to the west of Gondwana. pseudotachylyte veins occur in nearly all mylonite zones. Brittle deformation during Carboniferous to Triassic time produced major pull-apart basins located above terrane boundaries. Outcrop patterns of Triassic to Cretaceous sedimentary rocks are consistent with transtensional pull-apart basins followed by Andean transpressional deformation. The theoretical basis for fault reactivation and production of ‘short cuts’ is examined in the context of Tertiary to Recent basin inversion faults. The inversion faults follow the Palaeozoic trends and produce the present-day NNW-oriented, deep sedimentary basins and intervening ranges of basement rocks.

Upper Proterozoic rocks of the Avalon zone constitute much of the eastern basement of the New England Appalachians and have played a major role in its evolution. Avalonian rocks in southeastern New England are a composite of at least two distinct assemblages definable as terranes, the Esmond–Dedham and the Hope Valley. These terranes appear to have had differing interactions with rocks derived from the North American continent, with major tectonic modifications and/or transport occurring in late Paleozoic time. The Esmond–Dedham terrane lacks any clear previous relationships to other rocks in the region and probably was newly accreted during late Paleozoic time. The Hope Valley terrane is composed predominantly of basement gneisses and is exposed beneath extensive metasedimentary sequences of varying ages. Together with possibly related rocks elsewhere in New England (the Willimantic, Pelham, and Massabesic gneisses), the Hope Valley gneisses show evidence of late Paleozoic deformation and metamorphism. Although these rocks have been thought to share much of their history with overlying metasedimentary sequences (the Kearsarge–Central Maine synclinorium, Merrimack trough, and Putnam–Nashoba zone), several lines of evidence suggest that their contacts are tectonic and of late Paleozoic age. Each of these major rock assemblages potentially is a terrane, but with poor definition of the time when their present positions were attained. A late Paleozoic age for final assembly is possible, although all the rocks were not necessarily “exotic” relative to North America throughout the Paleozoic Era.