Magmatic History of the Avalon Terrane of Southern New Brunswick, Canada, Based on U-Pb (Zircon) Geochronology

Geological relationships preserved in the New Brunswick segment of the Appalachian orogen are key to deciphering the complex tectonic events that occurred during the closing of the Paleozoic Iapetus Ocean. These events can be explained in terms of geodynamic interactions between eight lithotectonic terranes. The first, the Caledonia terrane, comprises Neoproterozoic volcanic arc sequences and comagmatic plutons considered to form part of the microcontinent of Avalonia. The seven other terranes are associated with the microcontinent of Ganderia and consist of (1) Brookville terrane-Mesoproterozoic to Neoproterozoic platformal carbonates and Neoproterozoic to Early Cambrian plutonic rocks, (2) New River terrane-Neoproterozoic volcanic arc sequences and comagmatic plutons overlain by a Cambrian Penobscot volcanic arc sequence, In New Brunswick, closure of the Iapetus Ocean is attributed to four major tectonic episodes: (1) the Penobscot orogeny, which accreted the Miramichi, Annidale, and St. Croix terranes to the New River terrane on the trailing edge of Ganderia by closing a Penobscot backarc basin in the Early Ordovician, (2) the Taconic orogeny, which accreted the Popelogan terrane on the leading edge of Ganderia to the Laurentian margin in the Late Ordovician and effectively closed the main tract of the Iapetus Ocean, (3) the Salinic orogeny, which accreted the Elmtree and Miramichi terranes to the Laurentian margin by closing the Tetagouche backarc basin in the Silurian, and (4) the Acadian orogeny, which accreted the Caledonia terrane (Avalonia) to the Brookville and New River terranes on the trailing edge of Ganderia in the latest Silurian to earliest Devonian and in the process closed the last remaining oceanic tract in the northeastern Appalachians. RÉSUMÉLes corrélations géologiques préservées dans la partie du Nouveau-Brunswick de l'orogène des Appalaches sont essentielles pour bien comprendre le déroulement des événements tectoniques complexes survenus au moment de la fermeture de l'océan Iapetus, pendant le Paléozoïque. Il est possible d'expliquer ces événements par des interactions géodynamiques entre huit terranes lithotectoniques. Le premier, soit le terrane calédonien, comprend des séquences d'arc volcanique et des plutons comagmatiques du Néoprotérozoïque dont on estime qu'ils faisaient partie du microcontinent Avalonia. Les sept autres terranes sont associés au microcontinent Ganderia et comprenaient les terranes que voici : (1)

Section: Caledonia Terranementioning

confidence: 99%

Section: Caledonia Terranementioning

confidence: 99%

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

Fyffe

Johnson²,

Staal

2012

“…Although not comprehensively characterized geochemically, available data indicate that these units in the Long Reach area formed in an extensional tectonic setting (Greenough et al 1985). This package in the northeastern part of the New River Belt is essentially coeval, and to some extent lithologically similar to units of rhyolite, rhyolitic tuff, basaltic tuff and fl ows, and red beds in the upper part of the Coldbrook Group in the Caledonia Belt, which also formed in an extensional tectonic setting as described by Barr et al (1994) and . Further, as is common in the Caledonia Belt, the bimodal sequence in the Long Reach area is overlain concordantly by the Saint John Group.…”

Section: Discussionmentioning

confidence: 84%

Archived U-Pb (zircon) dates from southern New Brunswick

McLeod¹,

Johnson²,

Krogh

2003

U-Pb (zircon) ages for eight samples from southern New Brunswick were determined during the early 1990's as part of a regional mapping and correlation program. Although most of the dates have been subsequently quoted in the literature through personal communications, and some preliminary isochron diagrams have been incorporated in papers, the results have not been published in their entirety. The units sampled and best estimates for their ages are the Lobster Brook Formation

“…2). In Cape Breton the contact between the Avalon and Gander zones is not yet firmly established; for example, com pare the conflicting interpretations in Rast (1989), Barr andRaeside (1989), andMarillier et al (1989). Likewise, the Gan der/Avalon boundary is not yet resolved in New Brunswick (St. Peter and Fyffe, 1990).…”

Section: B a S E M E N T T E R R A N E Smentioning

confidence: 99%

“…The size, shape, and orientation of the basement fault blocks in southern New Brunswick are comparable to those elsewhere in the northern Appalachians and can be assessed from regional maps (Potter et al, 1979;Ruitenberg et al, 1979;Chandra, 1982;McCutcheon and Ruitenberg, 1987;Barr, 1988;Currie, 1989;Barr andWhite, 1989,1991b;McLeod et al, 1994). The blocks range in width from less than 1 km to greater than 25 km and in length from less than 10 km to greater than 150 km.…”

Section: T E C T O N Ic S E T T In Gmentioning

confidence: 99%

Maritimes Basin evolution: key geologic and seismic evidence from the Moncton Subbasin of New Brunswick

Peter

1993

The Maritimes Basin is a composite large (148,000 km^), post-Acadian internal successor basin. It comprises several early northeast-to east-trending, relatively deep, isolated subbasins which are covered by mainly regionally derived and widely distributed fluviatile sequences. The early basin fill in the Moncton Subbasin of southeastern New Brunswick is seen from stratigraphic and seismic reflection evidence to comprise two depositional sequences (allocycles) which are separated by a basin-wide unconformity. The basal cycle, the Horton Group, is a 3 to 5 km thick coarse-fine-coarse (alluvial-lacustrinealluvial) cycle. The medial lacustrine interval implies a period of rapid subsidence. The unconformably overlying allocycle, recorded by the Windsor and Hopewell groups, is a coarse-fine-coarse (alluvial-marine-alluvial) cycle. The marine part of the Windsor Group indicates a medial period of tectonic subsidence or eustatic sea level rise.The depositional history of the Moncton Subbasin sensu stricto ended following Hopewell time when the subbasin was inverted by late Namurian deformation. The Hopewell and older basin fill is unconformably overlain by quartzose fluviatile sandstones with associated inter-channel mudstones and paludal deposits of the regionally distributed late Namurian/ Westphalian Cumberland Group. Cumberland rocks are succeeded by meandering(?) fluviatile strata of the late Westphalian/ Permian Pictou Group. An angular discordance between Cumberland and Pictou strata implies a period of uplift or regional tilting.The tectonism that initiated and terminated the early allocycles and which is recorded by unconformities following Horton and Hopewell deposition is seen from structural data and scismic reflection profiles to have resulted from dextral transpression. Evidence includes a network of basin-parallel northeast-trending anastomosing faults (many with shallowly pitching slickensides), associated en echelon folds, and geologically and seismically identified positive flower structures. An interpretation of early Maritimes Basin evolution in a wrench setting is consistent with the many northeast-trending steeply dipping terrane boundary faults in the underlying basement and with most recently published evidence of Variscan (Alleghenian) orogenesis as resulting from dextral oblique collision of Laurentia and Gondwana.Le bassin des Maritimes est un bassin successeur interne d'age post-acadien, composite et de grandes dimensions (148 000 km^). 11 comprend plusieurs sous-bassins primitifs isoles, de direction nord-est a est, et relativement profonds, qui sont recouverts par des sequences fluviatiles largement reparties et de sources generalement regionales. On peut considerer que le remplissage initial du sous-bassin de Moncton au sud-est du Nouveau-Brunswick, d'apres les donnees statigraphique et de sismique reflexion, comprend deux sequences de deposition (allocycles) separees par une discordance sur toute l'etendue du bassin. Le cycle de base, le Groupe d'Horton, est un cycle grossier-fin-grossier...