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

Disparate Paths in the Geologic Evolution of the Northern and Southern Appalachians: A Case for Inherited Contrasting Crustal/Lithospheric Substrates

“…Suwannee also records a ca. 375-345 Ma thermal event (Scholle 1979;Dallmeyer 1991); on the basis of more inboard portions of the orogen and Suwannee sharing this Late Devonian-Early Mississippian thermal event, it has been speculated that the Fammenian event resulted, in part, from the accretion of Suwannee (Hibbard et al 2010;Pollock et al 2012). This interpretation requires that Suwannee was later translated along the southern Appalachian margin to its present position south of the Alabama promontory.…”

U–Pb zircon geochronology of Proterozoic and Paleozoic rocks, North Islesboro, coastal Maine (USA): links to West Africa and Penobscottian orogenesis in southeastern Ganderia?

“…1) has yielded fundamental insights into Earth history, paleogeography, and processes (e.g., Wilson 1966), yet continues to present significant questions. In contrast to the western peri-Laurentian flank of the orogen, which is relatively well understood in terms of Ordovician continent-arc collision (e.g., Karabinos et al 2017), the eastern peri-Gondwanan realm comprises a complex mosaic of pre-Silurian terranes with a much more contentious tectonic evolution (Murphy et al 2004;Fyffe et al 2011;Pollock et al 2012). Ganderia, the most outboard of several peripheral Gondwanan domains, was first to accrete to Laurentia and has proved especially challenging to interpret owing to a protracted history of deformation and magmatism (e.g., Hibbard et al 2007).…”

Does the Meguma Terrane Extend into SW England?

“…By contrast, correlation of the Meguma terrane beyond the offshore Scotian shelf (King and MacLean 1976;Pe-Piper and Jansa 1999) and the southern Grand Banks (Haworth and Lefort 1979;Reid 1988) remains unresolved, although a possible linkage exists with the Suwanee terrane of the Florida subsurface (Hibbard et al 2010;Waldron et al 2011;Pollock et al 2012). …”