A paleogeographical review of the peri-Gondwanan realm of the Appalachian orogen1This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.

Abstract

The eastern edge of the Appalachian orogen is composed of a collection of Neoproterozoic – early Paleozoic domains, Avalonia, Carolinia, Ganderia, Meguma, and Suwannee, which are exotic to North America. Differences in the geological histories of these peri-Gondwanan domains indicate that each separated independently from Gondwana, opening the Rheic Ocean in their wake. Cambrian departure of Ganderia and Carolina was followed by the Ordovician separation of Avalonia and Silurian separation of Meguma. After separation in the early Paleozoic, these domains constituted the borderline between the expanding Rheic Ocean and contracting Iapetus Ocean. They were transferred to Laurentia by early Silurian closure of Iapetus and Devonian–Carboniferous closure of the Rheic Ocean during the assembly of Gondwana and Laurentia into Pangaea. The first domain to arrive at Laurentia was Carolinia, which accreted in the Middle Ordovician during the Cherokee orogeny. Salinic accretion of Ganderia occurred shortly thereafter and was followed by the Acadian accretion of Avalonia. The Acadian orogeny was immediately followed by Middle Devonian – Early Carboniferous accretion of Meguma and possibly Suwannee which led to the Fammenian orogeny. The episodicity of orogeny suggests that the present location of these domains parallels their order of accretion. However, each of these crustal blocks was translated along strike by large-scale Late Devonian – Carboniferous dextral strike–slip motion. The breakup of Pangaea occurred outboard of the Paleozoic collision zones that accreted Carolinia, Ganderia, Avalonia, Meguma, and Suwannee to Laurentia, leaving these terranes appended to North America during the Mesozoic opening of the Atlantic.