The Eastport Formation (Lower Devonian) in the northern Passamaquoddy Bay area, southwest New Brunswick

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: Mascarene Basinmentioning

confidence: 82%

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

“…2). In general, it contains a continuous depositional sequence with shallow water Wenlockian to Pridolian rocks at the base overlain by intertidal to subaerial Lochovian units (e.g., Gates 1977;Pickerill et al 1976;Pickerill et al 1978;Fyffe et al 1999). Structurally, the belt is characterized by a single poorto well-developed cleavage that is coplanar to non-coplanar with a broad, gently east-plunging anticlinal and a shallowly north-plunging synclinal folds defined by shallowly dipping units (Ruitenberg 1968;Gates 1977;McLeod and Rast 1988;Van Wagoner et al 1994).…”

Section: G E O L O G I C a L S E T T In G H Is T O R Ic A L P E R Smentioning

confidence: 99%

Mafic intrusions on Campobello Island: implications for New Brunswick - Maine correlations

McLeod

Pickerill

Lux

2001

Late Ordovician through Early Devonian units of the Passamaquoddy Bay area are interpreted to represent sequences that evolved in arc and back-arc environments. The main elements of the arc are exposed on Campobeilo Island and include a predominantly felsic volcanic sequence to the northeast, a sequence of intercalated turbidite and mafic volcanic rocks to the southwest, and mafic dyke swarms throughout. Petrographic, geochemical, and 40Ar/39Ar studies of these rocks record episodic deformation and varying degrees of metamorphism up to lower amphibolite facies, and a protracted history of mafic magma injection from a similar source beginning in the Early Silurian. These features, combined with stratigraphic relationships and overall structural patterns, indicate a rapid transition from felsic-to mafic-dominated magmatism accompanied by radical changes in the depositional regime in the arc with time, and exposure of progressively deeper crustal levels towards the northeast within the arc.Review of the assignment of other units in the Passamaquoddy Bay region to major tectonostratigraphic belts north of Campobeilo Island clarifies regional correlations and provides possible additional links to Neoproterozoic basement in the area.Les unites de TOrdovicien superieur au Devonien inferieur du secteur de la baie Passamaquoddy sont interpretees comme des unites representatives de sequences ayant evolue dans des environnements d'arc et d'arriere-arc. Les principaux elements de Pare affleurent sur Pile Campobeilo et component une sequence principalement volcanofelsique au nord-est, une sequence volcanomafique/turbiditique intercalee au sud-ouest et des groupes de filons mafiques un peu partout. Des etudes petrographiques, geochimiques et 40Ar/39Ar de ces roches reinvent une deformation episodique et des degres divers de metamorphisme jusqu'au facies amphibolique inferieur, ainsi que des antecedents prolongds d'injection de magma mafique d'une source similaire a partir du Silurien inferieur. Ces p articulars, conjuguees aux relations stratigraphiques et aux configurations structurales generates, revelent une transition rapide d'un magmatisme a predominance felsique a un magmatisme a predominance mafique accompagne de changements spectaculaires dans le regime de sedimentation a Pinterieur de Parc avec le temps, ainsi qu'un affleurement de niveaux crustaux progressivement plus profonds vers le nord-est a Pintdrieur de Parc. L'examen de Paffectation des autres unites dans la region de la baie Passamaquoddy aux principals structures teconostratigraphiques au nord de Pile Campobeilo clarifie les correlations regionales et foumit des liens suppldmentaires possibles avec le socle du Proterozoi'que superieur du secteur. In t r o d u c t io nDiabase dykes and gabbroic intrusions comprise a significant portion of most Silurian sections in the Passamaquoddy Bay area of southwestern New Brunswick. Numerous older publications based on work in the 1960s and 1970s (e.g., Cumming 1966Helmstaedt 1968;Ruitenberg 1968;Donohoe 1978;Gates 196...

“…The Ovenhead Zone (after Ruitenberg and McCutcheon, 1982), that crops out to the north, contains a gently folded Lower Silurian to Lower Devonian sequence with a locally developed, northeast trending cleavage non-coplanar to the folds in part. Cumming (1967), Ruitenberg (1968), Pickerill and Pajari (1976), Donohoe (1978), McLeod (1979) and Gates (1981Gates ( , 1984 provided de tailed descriptions of the Lower Silurian to Lower Devonian stratigraphy and several authors proposed regional correlations based mainly on faunal evidence, noting structural and lithologi cal contrasts across zones.…”

Section: Synthesis and Discussionmentioning

confidence: 99%

Correlations and fault systematics in the Passamaquoddy Bay area, Southwestern New Brunswick

McLeod

Rast

1988

Three distinct fault-bounded litho-tectonic units have been recognized on Campobello Island in southern Passamaquoddy Bay. These units are the Upper Silurian Wilsons Beach beds, the Lower Silurian Quoddy Formation and the Upper Precambrian Coldbrook Group. Contact relationships between these units and their correlations in the Passamaquoddy Bay area resolve correlation problems between coastal Maine and New Brunswick, and demonstrate the nature of the junction between the Avalon Platform and the Acadian mobile belt. The Wilsons Beach beds are a remnant of the Acadian belt on northeastern Campobello Island, whereas the Coldbrook Group and the Quoddy Formation represent a fault block of the Avalon Platform. The Coldbrook Group, probably overlain unconformably by the Quoddy Formation, plunges to the southwest beneadi the Quoddy Formation of southeastern Maine. The Siluro-Devonian basins formed in a tensional tectonic regime in response to normal(?) faulting. These faults formed along pre-existing zones of crustal weakness that were generated during the late Precambrian by major strike-slip faulting. The present geological configuration of the area was basically established by episodic reactivation of northeast-trending faults (high-angle reverse movements) during the compressional regime of the Acadian Orogeny, RÉSUMÉ On reconnait trois unités litho-techniques bordérs par des failles sur l'ile de Campobello dans le sud de la baie-de Passamaquoddy. Ce sont les lits de Wilson Beach (Silurien supérieur), la Formation de Quoddy (Silurien inférieur) et le Groupe de Coldbrook (Précambrien supérieur). La corrélation de ces unités et de leurs contacts dans la baie de Passamaquoddy résout les problèmes de corrélation entre la côte du Maine et le Nouveau-Brunswick et démontre la nature de la jonction entie la Plate-Forme d'Avalon et la ceinture mobile acadienne. Les lits de Wilson Beach sont un residu de la ceinture acadienne sur le nord-cst de l'ile de Campobello. Par contre, le Groupe de Coldbrook et la Formation de Quoddy représentent un bloc faillé de la Plate-Forme d'Avalon. Le Groupe de Coldbrook est probablement recouvert avec discordance par la Formation de Quoddy et plonge vers le sud-ouest sous la Formation de Quoddy dans le sud-est du Maine. Les bassins siluro-dévoniens se formèrent dans un régime tectonique de tension en résponse à un mouvement normal(?) de failles. Ces failles se créerent le long de zones de faiblcsse crustale déjà établies et issues d'un important coulissement tardi-précambrien. La configuration géologique actuelle de la région s'établit principalement par réactivation épisodique de failles à tendance nord-est (mouvements inverses à fort pendage) durant le régime compressif de l'orogénèse acadienne, [Traduit par le journal]