Appalachian Orogen in Canada

Abstract

The Appalachian Orogen is divided into five broad zones based on stratigraphic and structural contrasts between Cambrian–Ordovician and older rocks. From west to east, these are the Humber, Dunnage, Gander, Avalon, and Meguma Zones.The westerly three zones fit present models for the development of the orogen through the generation and destruction of a late Precambrian – Early Paleozoic Iapetus Ocean. Thus, the Humber Zone records the development and destruction on an Atlantic-type continental margin, i.e., the ancient continental margin of Eastern North America that lay to the west of Iapetus; the Dunnage Zone represents vestiges of Iapetus with island arc sequences and mélanges built upon oceanic crust; and the Gander Zone records the development and destruction of a continental margin, at least in places of Andean type, that lay to the east of Iapetus.The Precambrian development of the Avalon Zone relates either to rifting and the initiation of Iapetus or to subduction and a cycle that preceded the opening of Iapetus. During the Cambrian Period, the Avalon Zone was a stable platform or marine shelf.Cambrian–Ordovician rocks of the Meguma Zone represent either a remnant of the continental embankment of ancient Northwest Africa or the marine fill of a graben developed within the Avalon Zone.Silurian and younger rocks of the Appalachian Orogen are mixed marine and terrestrial deposits that are unrelated to the earlier Paleozoic zonation of the system. Silurian and later development of the orogen is viewed as the history of deposition and deformation in successor basins that formed across the already destroyed margins and oceanic tract of Iapetus.

A Review of Proterozoic to Early Paleozoic Lithotectonic Terranes in New Brunswick, Canada and their Tectonic Evolution during Penobscot, Taconic, Salinic and Acadian Orogenesis

“…A significant advance was made in the understanding of the tectonic evolution of the Appalachian orogen with the introduction of four lithotectonic divisions on the island of Newfoundland, those being the Humber, Dunnage, Gander and Avalon zones (Williams et al 1972;Williams 1978Williams , 1979. In this scheme, the Humber Zone in the west and Avalon Zone in the east were interpreted as the Laurentian and Gondwanan platformal margins, respectively, of the Paleozoic Iapetus Ocean.…”

Logan Medallist 2. Geophysics and Geology: An Essential Combination Illustrated by LITHOPROBE Interpretations–Part 1, Lithospheric Examples

“…Figure 8b (a) Correlation of the generalized stratigraphy of the Muskwa assemblage to three synthetic seismic traces calculated for three differing velocity-density relationships for the units in the stratigraphic column (Cook and Siegel 2006 Williams (1979Williams ( , 1995 provided a good summary of the geology as known at those times.…”

Does the Meguma Terrane Extend into SW England?

“…Correlation of the Appalachian Mountains of Atlantic Canada with the Caledonide and Variscan orogens of western and southern Europe dates to Wegener's earliest arguments for Continental Drift (Wegener 1912, translated by von Heune 2002 and, with the formalization of lithotectonic zones (Humber, Dunnage, Gander, Avalon and Meguma) within the northern Appalachian orogen (Williams 1976(Williams , 1978(Williams , 1979 attempts were made to establish their trans-Atlantic linkages (e.g. Schenk 1971;Tozer and Schenk 1978;Wones 1980;Gayer 1985, and references therein).…”

“…Nance et al 2008). However, the Meguma terrane is the only major terrane in the northern Appalachian orogen that has no obvious correlatives elsewhere in the Appalachians (Williams 1978(Williams , 1979 and no confirmed linkages to either the Caledonide or Variscan orogens of Western Europe (see Waldron et al 2009). This is in contrast with its immediate peri-Gondwanan neighbours, Avalonia and Ganderia, both of which show age and isotopic similarities to parts of Carolinia in the southern Appalachians (e.g.…”