Graptolites from the Benton area of west-central New Brunswick and their regional significance

The Lower to Middle Ordovician volcanic suite of the Tetagouche Group from the southwestern part of the Miramichi Terrane in the Woodstock-Meductic area in southwestern New Brunswick is composed of a bimodal basalt-rhyolite association. The basalts have calc-alkalic characteristics and were emplaced on the continental crust in a volcanic arc or back-arc environment. The rhyolites were probably derived by melting of an amphibolite-facies crust. The basalts differ from those of the Tetagouche Group from the Bathurst area which include within-plate basalts and MORB. However, they both may be part of a single Ordovician arc-back-arc system.Le cortege volcanique du Groupe de Tetagouche (Ordovicien median a inferieur) dans la portion sud-ouest de la Laniere de Miramichi (region de Woodstock-Meductic, sud-ouest du Nouveau-Brunswick) se compose d'une association bimodale de basalte et rhyolite. Les basaltes presentent des caracteres calco-alcalins et ils se sont mis en place sur la croute continentale dans un milieu d 'arc insulaire ou de retro-arc. Les rhyolites proviennent probablement de la fonte d 'une croute de facies a amphibolites. Les basaltes different de ceux du Groupe de Tetagouche dans la region de Bathurst, qui comprennent des basaltes intra-plaques et des MORB, quoique tous deux puissent faire partie d 'un systeme arc:retro-arc ordovicien unique.[Traduit par le journal]

Section: Geological Settingmentioning

confidence: 99%

“…1. Generalized map of tectonostratigraphic zones of New Brun swick (modified from Fyffe et at., 1983).…”

Section: Introductionmentioning

confidence: 99%

Geochemistry of Ordovician volcanic rocks of the Tetagouche Group of southwestern New Brunswick

Dostál

1989

“…5) is divided into felsic volcanic flows and tuffs of the Porten Road Formation; intermediate tuffs and volcaniclastic rocks of the Eel River Formation; mafic volcanic flows and tuffs of the Oak Mountain Formation; and disconformably overlying feldspathic sandstone and shale of the Belle Lake Formation. Graptolites from the Belle Lake Formation are indicative of a Late Ordovician (Sandbian) age (Fyffe et al 1983). Conodonts from strata that are possibly correlative with the Belle Lake Formation east of Woodstock gave a slightly older Middle Ordovician (Darriwilian) age (Venugopal 1979;Nowlan 1981).…”

Section: Miramichi Terranementioning

confidence: 99%

“…The formation cannot be older than Early Cambrian, according to the 525 ± 6 Ma date on its youngest contained zircon population ). Graptolites recovered from the overlying Bright Eye Brook black shale are Early Ordovician (Tremadocian to Floian) in age (Fyffe et al 1983).…”

Section: Miramichi 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

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)

“…To the northeast of the Casco Bay Terrane, late Tremadocian to Arenigian (Early Ordovician) black pelites, succeeding a coarser sandstone sequence, are known throughout the Miramichi Terrane of central New Brun swick (Fyffe et al, 1983). The pelites immediately underlie a thick, bimodal Middle Ordovician (Llanvimian to early Caradocian) volcanic sequence thaLwas generated during extension of continental crust (van Staal, 1987).…”

Section: Discussionmentioning

confidence: 99%

Tectonic significance of black pelites and basalts in the St. Croix Terrane, coastal Maine and New Brunswick

Fyffe

Stewart

Ludman

1988

Self Cite

The St. Croix Terrane of coastal Maine and adjacent New Brunswick is characterized by Ordovician carbonaceous pelites in the upper part of the stratigraphic section. These pelites are locally interbedded with mafic volcanic rocks. Metamorphism in the terrane varies from the albite-epidote-homfels facies along the New Brunswick-Maine border to greenschist and lower amphibolite facies in southwestern Maine.The mafic volcanic rocks are evolved basalts that have trace-element abundances similar to intraplate tholeiites. Their La/ Nb ratios of 1.3 to 1.9 and absolute REE concentrations of 30 times chondrite in the more evolved basalts are features common to many continental flood basalts. Enrichment in high field-strength elements relative to MORB distinguishes them from volcanic-arc tholeiites.Depositionof carbonaceous pelites coincided with the widespread development of oceanic crust in the early Paleozoic. The trace-element and REE patterns of the associated basalts suggest eruption through rifted continental crust marginal to an expanding ocean basin.La presence de pelites riches en carbonc dans la partie superieure de sa section stratigraphique caracterise la Laniere de St. Croix qui se rencontre au littoral du Maine et dans les regions du Nouveau-Brunswick avoisinantes. Ces pelites s'interlitent localement avec des volcanites mafiques. Le metamorphisme de la laniere va du facies des comeennes a albite et epidote le long de la frontiere entre le Nouveau-Brunswick et le Maine jusqu'au facies inferieur des amphibolites dans le sud-ouest du Maine.Les volcanites mafiques sont des basaltes evolues presentant des abondances d 'elements en traces semblables a celles des tholeiites intraplaques. Leurs rapports La/Nbde 1.3 a 1.9, ainsi que leurs concentrations absolues enT.R. egales a 30 fois celles des chondrites au sein des basaltes plus evolues, sont communes a plusieurs nappes d 'inondation basaltique continentales. On les distingue des tholeiites d ' arc insulaire par leur enrichissement en elements a intensite de champ elevee par rapport aux MORB.Le depot de pelites riches en carbone co'incida avec le developpement largement repandu de croute oceanique au debut du Paleozoi'que. Les spectres de T.R. et d 'elements en traces des basaltes qui leur sont associes suggerent une eruption a travers une croute continentale a la derive en bordure d'un bassin oceanique en expansion.