Biostratigraphie et paléobiogéographie du Siluro-Dévonien de la zone de Meguma (Nouvelle-Écosse, Canada)

Abstract

Studies of fossils collected from the Nictaux–Torbrook and Bear River synclines (Nova Scotia) allow a reexamination of the Siluro-Devonian stratigraphy of the Meguma terrane. The location of this terrane relative to the main paleocontinents of the circumatlantic domain during this period is discussed. Wenlockian, Ludlovian, and Pridolian biostratigraphic horizons have been dated. The benthic fauna of the Torbrook Formation are assigned here to the Lochkovian, Pragian, and Lower Emsian. The Pridolian fauna shows northern European affinities. Thus, the Meguma terrane probably belonged to the North Atlantic domain, as for the Avalon terrane, and occupied a southern position in the "Euramerica" plate during this period. The Devonian fauna belongs to the "old world realm" and shows north Gondwanian and Rhenish affinities. As early as the Lochkovian, species known from both the Rhenish and north Gondwanian domains are recognized in Meguma, as well as others reported so far only from northwestern Africa, Iberian Peninsula, and (or) Armorican Massif. The presence of Rhenish fauna confirms the postulated location for the Meguma terrane during the Upper Silurian since this fauna is representative of southern Baltica marginal areas in Europe. On the other hand, the presence of north Gondwanian fauna implies close relationships with western European margin of Gondwana. The lack of a wide oceanic gap separating north Gondwana and Euramerica can explain the faunal exchanges during Lower Devonian times between western Europe and easternmost Appalachian province despite the presence of a physical barrier.

Stratigraphy of the Lower Paleozoic Goldenville and Halifax groups in the western part of southern Nova Scotia

“…West of the Chebogue Point shear zone (termed the northwestern area in the present study) the Halifax Group is disconformably overlain by rift-related, shallow marine volcanic and sedimentary rocks of the Silurian White Rock Formation and equivalent units and the Early Devonian Torbrook Formation (Jensen 1975;Lane 1975Lane , 1981Bouyx et al 1997). These younger formations are not present southeast of the shear zone.…”

“…2), the Halifax Group is disconformably overlain by mainly Silurian, shallow marine sedimentary rocks of the White Rock Formation and equivalent units (Lane 1975(Lane , 1981Bouyx et al 1997;White in press). Rift-related volcanic rocks occur throughout the White Rock Formation (Schenk 1997;Keppie and Krogh 1999;MacDonald et al 2002;White in press) and may have formed during extension linked to the separation of Meguma from Gondwana (van Staal et al 1998;White and Barr 2004;van Staal 2007).…”

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.

“…Lochovian brachiopods (Schizophoria runegatensis, leptostrophia and index meristella renaudae), and trilobites (digonus acuminatus) from the Torbrook Formation demonstrate strong linkages with coeval sequences from both the Rhenish and north Gondwanan domains (Boucot 1960;Bouyx et al 1997). Although most Emsian taxa are typically Rhenish and Gondwanan forms, minor shelly fossils appear to have Laurentian affinities as they are similar to those found in the eastern United States and Canada.…”

“…The latter scenario implies an earlier interaction between Suwannee and the Laurentian margin than previously thought, and is supported by Late Devonian to Mississippian tectonothermal events in Suwannee and the southern Appalachians that are coeval with Fammenian orogenesis (375-340 Ma) in the northern Appalachians . Comparable faunal assemblages (Bouyx et al 1997) and similarities in detrital mineral compositions (Mueller et al 1994;Waldron et al 2009) between Suwannee and Meguma suggest that both crustal blocks were situated relatively close to the margin of West Africa where they constituted the leading interface of Gondwana that generated an orogen-wide Famennian event.…”

A new species of Neopaulinella (Brachiopoda, Terebratulida) from the Eastern Iberian Chains, Spain (Lower Devonian)

“…(Giebel, 1858) proves that the Erbslochgrauwacke is part of the northern Gondwana terranes and presents a block that probably slipped northward (Jansen 2001, Schemm-Gregory 2008c. The Lower Devonian of Western Europe can also be correlated with the Meguma Zone (Nova Scotia) with the presence of Vandercammenina Boucot, 1975 andOvetensispirifer Schemm-Gregory, 2008b in both regions, however, Neopaulinella has not yet been reported from Nova Scotia (Bouyx et al 1992;Boucot 1960Boucot , 1975Schemm-Gregory 2008b). Neopaulinella appears in Siegenian and Emsian strata.…”