A prominent system of long and generally straight faults extends from southeastern New England through western and north-central Newfoundland. A wrench-fault history is implied by the continuity, the prominent shear zones, and the crosscutting of major rock units by the faults. Subsidiary structures and, in places, demonstrable or implied offset of rock bodies and contacts indicate that the dominant late-phase slippage was dextral along the NE-striking faults of New Brunswick and Newfoundland and along the east-striking Cobequid fault of Nova Scotia. An exception is the Harvey-Hopewell fault of New Brunswick, on which sinistral slip followed a greater interpreted dextral slip. Wrench faults in Canada cut the Devonian Acadian igneous-metamorphic basement complex and the Lo er Carboniferous cover strata. The faults north of the Caledonia arch in New Brunswick are overlapped by an essentially undeformed Upper Carboniferous cover, thus dating the dextral movement there as Early or middle Carboniferous. The Harvey-Hopewell sinistral slip occurred during Late Carboniferous time coincident with salt tectonism. The Cobequid fault appears to have had major dextral slip in Late Carboniferous time. In western Newfoundland, dextral slip cuts the much deformed Lower Carboniferous, but younger Carboniferous rocks are less affected; the Lukes Arm and other east-splaying faults may be slightly older.

As much as 125 mi of Carboniferous dextral displacement can be estimated for faults cutting across southern New Brunswick, to which an additional 130 mi on the Cobequid fault seems indicated in the Fundy Bay area. From 65 to perhaps 100+ mi of dextral slip is interpreted for the Carboniferous faults of western Newfoundland; two values are used in the palinspastic reconstructions. The Caledonia and Cobequid arches on the mainland can be reconstructed to show that they were a single arch before strike-slip offset. Several faults in eastern Newfoundland appear to be wrench faults but are of uncertain age.

Structural patterns in scattered localities suggest an earlier phase of sinistral wrenching, possibly of very large magnitude, on the NE-trending faults. Such slip, if it occurred, may have been a late stage of the Acadian orogeny.