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We report a diverse assemblage of trace fossils from the Lower(?) Cambrian High Head member of the Church Point Formation near Yarmouth, Nova Scotia. Based on the presence of sharp-based beds, load casts, and flute casts, along with other sedimentological criteria, the strata are interpreted to have a turbidite origin. Other characteristics, including wrinkle structures and high fidelity of trace-fossil preservation, suggest that the inter-episode biotope was influenced by the presence of biomats. The trace-fossil assemblage includes (in approximate order of abundance) Planolites, Helminthopsis, Oldhamia, Chondrites, Gordia, Cladichnus, Psammichnites gigas, Treptichnus, Phycodes, Lorenzinia, Palaeophycus, and Teichichnus. Trace fossils are increasingly abundant upwards in the section, but they are ultimately mitigated by an increase in (inferred) sedimentation rates. The trace-fossil assemblage, which bears many similarities to other Lower Cambrian locales (e.g., Puncoviscana Formation of northwest Argentina, Chapel Island Formation of southeastern Newfoundland), and the distribution of ichnofossils strongly support an earliest Cambrian age for the studied strata. More importantly, evolutionary trends can be interpreted from the trace-fossil assemblage, namely (1) an increase in size and diversity of animals in deep water; (2) an expansion of motile strategies used to coexist with biomats; and, (3) increasingly complex mining strategies below the sediment-biomat interface. Nous signalons l'existence d'un assemblage varie; d'ichnofossiles dans le membre cambrien infeerieur (?) de High Head de la Formation de Church Point, pres de Yarmouth, en Nouvelle-Ecosse. A la lumiere de la presence de lits dont la base est nettement definie, d'empreintes de charge et de flutes, ainsi que d'autres criteres sedimentologiques, les strates sont interpretees comme etant d'origine turbiditique. D'autres caracteeristiques, dont la presence de rides et le degre eleve de detail preserve des ichnofossiles, suggerent que le biotope inter-episode etait influence par la presence de tapis biologiques. L'assemblage d'ichnofossiles comprend (en ordre approximatif d'abondance) Planolites, Helminthopsis, Oldhamia, Chondrites, Gordia, Cladichnus, Psammichnites gigas, Treptichnus, Phycodes, Lorenzinia, Palaeophycus et Teichichnus. L'abondance des ichnofossiles augmente vers le haut de la section, bien que cette augmentation soit ultimement contrecarree par une augmentation des taux de sedimentation (presumes). L'assemblage, qui ressemble a plusieurs egards aux assemblages d'ichnofossiles d'autres localues du Cambrien inferieur (p. ex. la Formation de Puncoviscana, du nordouest de l'Argentine, la Formation de Chapel Island du sud-est de Terre-Neuve), et la distribution des ichnofossiles appuient fortement la these d'un age du tout debut du Cambrien pour les strates etudieees. Fait encore plus important, l'assemblage d'ichnofossiles permet de deduire diffeerentes tendances evolutionnaires, a savoir : (1) l'augmentation de la taille et de la diversite des animaux en eau profonde, (2) la mise au point de nouvelles strategies motiles permettant de coexister avec les tapis biologiques et (3) l'augmentation de la complexite des strategies de forage sous l'interface sediments- tapis biologique., Introduction Because of the paucity of body fossils in the Lower Cambrian, the biostratigraphic indicator of the start of the Lower Cambrian System is placed at the base of the [...]

ABSTRACT Machias Seal Island in the northern Gulf of Maine consists of fine- to medium-grained weakly foliated quartz monzodiorite. Although previously inferred to be as young as Devonian, the quartz [...]

ABSTRACT Late Neoproterozoic (680 Ma to 560 Ma) Avalonian rocks in the Mira terrane of southeastern Cape Breton Island have been metamorphosed inhomogeneously, at very low grade to low grade, [...]

We report single-grain ages for detrital muscovite separated from sandstone samples from five localities in southern New Brunswick and southeastern Cape Breton Island, Nova Scotia, and from two quartzite clasts from a quartzitepebble conglomerate that underlies the sampled sandstone units in New Brunswick. The oldest detrital grains were found in one of the quartzite clasts; their age range, ca. 650-630 Ma, is defined not only by the single-grain analyses but also by spot dating (using a UV laser) within a single large grain, suggesting that these grains came from a single source. The second quartzite clast has a blastomylonitic fabric with muscovite 'fish,' and most of the muscovite ages have been partially reset (at ca. 550 Ma) from the original ca. 650-630 Ma ages. The age distribution plots obtained for the sandstone samples suggest the presence of muscovite that still retains the original source age, but most of the grains have been partially reset by the same ca. 550 Ma event that reset muscovite ages in the second quartzite clast. We suggest that the quartzite source that produced the two clasts was also the source of muscovite in the Avalonian Cambrian rocks of Maritime Canada. The original source rock was likely a metamorphic or perhaps granitic rock unit situated relatively proximal to the site of deposition of the quartzite protolith, but the actual source is not known, and locally, no potential candidates are exposed. The resetting event at ca. 550 Ma may be linked to initial stages of regional transtension associated with rifting of Avalonia from Gondwana. Nous rapportons des ages determines sur des grains uniques de muscovite detritique provenant d'echantillons de gres de cinq localites du sud du Nouveau-Brunswick et du sud-est de l'ile du Cap Breton, en Nouvelle-E cosse, ainsi que de deux clastes de quartzite d'un conglomerat de galets-quartzite qui se retrouve sous les unites de gres echantillonnees au Nouveau-Brunswick. Les plus anciens grains detritiques ont ete retrouves dans l'un des clastes de quartzite; leur plage d'age, d'environ 650-630 Ma, est definie non seulement par des analyses sur grains uniques mais aussi par une datation ponctuelle (au moyen d'un laser UV) a l'interieur d'un seul gros grain, suggerant que ces grains proviennent d'une seule source. Le second claste de quartzite avait une texture blastomylonitique avec des grains lenticulaires << mica fish >> et la plupart des ages pour la muscovite avaient ete partialement reinitialises a ~550 Ma a partir des ages originaux ~650-630 Ma. Les courbes de distribution de l'age, obtenues pour les echantillons de gres, suggerent la presence de muscovite ayant conserve l'age original de la source; cependant, la plupart des grains ont ete reinitialises par le meme evenement survenu a ~550 Ma qui a reinitialise les ages de la muscovite dans le second claste de quartzite. Selon nous, la source de quartzite qui a produit les deux clastes serait aussi la source de la muscovite dans les roches avaloniennes, datant du Cambrien, des provinces maritimes canadiennes. La roche source originale etait probablement une unite de roche granitique ou metamorphique situee relativement pres du site de deposition du quartzite protolithe, mais la source reelle est inconnue et aucun << candidat >> potentiel n'affleure localement. L'evenement de reinitialisation survenu il y a ~550 Ma pourrait etre relie aux stades initiaux de transtension regionale associee a la creation du rift entre l'Avalonie et le Gondwana. [Traduit par la Redaction], Introduction For many years, U-Pb ages of detrital zircon grains have been used to infer the provenance of sedimentary units. More recently, Haines et al. (2004), among others, also have [...]

ABSTRACT Detrital zircon ages were determined for conglomerate and sandstone samples from six fault-bounded belts in New Brunswick and coastal Maine. Formations sampled included the Martinon (Brookville belt), Flagg Cove [...]

Detrital zircon ages from the lower part of the Late Proterozoic(?) to Middle Cambrian Goldenville Group in the Meguma terrane of Nova Scotia suggest derivation from local sources in the Avalonian and Pan-African orogens on the margins of Early Cambrian Gondwana. Samples from near the top of the group show a broader distribution, including ages back to Archean. The [ζ.sub.Nd] data show a corresponding trend, from slightly positive in the lower Goldenville Group to highly negative in the upper Goldenville Group and overlying Upper Cambrian to Lower Ordovician Halifax Group. The trends are consistent with deposition of the lower part of the Meguma succession in a rift, in which uplifted rift-flanks were the main source of the early basin fill, whereas subsequent thermal subsidence of rift margins allowed for more widespread sediment sourcing in younger units. The rift was possibly located between Gondwana and Avalonia, and may have been the locus for separation of Avalonia from Gondwana to form part of the Rheic Ocean. Les ages des zircons detritiques du Groupe de Goldenville (Proterozoique tardif(?) a Cambrien moyen) dans le terrane de Meguma de la Nouvelle-Ecosse suggerent une provenance de sources locales dans les orogenes avalonien et pan-africain sur les bordures du continent de Gondwana au Cambrien precoce. Des echantillons preleves pres du sommet du groupe montrent une distribution plus vaste, incluant des ages archeens. Les donnees [ζ.sub.Nd] montrent une tendance correspondante, de legerement positive dans le Groupe de Goldenville inferieur a hautement negative dans le Groupe de Goldenville superieur et dans le Groupe de Halifax sus-jacent (Cambrien superieur a Ordovicien inferieur). Les tendances concordent avec la deposition de la partie inferieure de la succession de Meguma dans une fosse d'effondrement; les flancs souleves de cette fosse auraient constitue la source principale de materiel de remplissage du bassin primitif alors qu'une subsidence thermique subsequente des bordures de la fosse aurait conduit a une source de sediments plus etendue pour les unites plus jeunes. La fosse d'effondrement etait possiblement situee entre le Gondwana et l'Avalonie et elle constitue possiblement le lieu de la separation de l'Avalonie du Gondwana pour la formation d'une partie de l'ocean Rheique. [Traduit par la Redaction], Introduction Meguma, the most outboard terrane of the Canadian Appalachians (Fig. 1a), has no clear correlative elsewhere in the Appalachian-Caledonide orogen. Although generally regarded as a peri-Gondwanan terrane, Meguma shows [...]

Distinct [sup.18]O depletion is characteristic of a large majority of the 620-550 Ma felsic igneous rocks of Avalonia in the northern Appalachian orogen. Neoproterozoic rocks in the Boston Avalon terrane have the lowest δ[sup.18][O.sub.WR] values (≥-3.1‰), followed by the Mira terrane in Cape Breton Island and the Caledonia terrane in New Brunswick (≥-1.2‰), the Avalon terrane in Newfoundland (≥+2.8‰), and the Antigonish Highlands in Nova Scotia (≥+5.3‰). In contrast, this depletion of [sup.18]O is observed in very few of the Paleozoic felsic igneous rocks from these Avalonian terranes, and also in very few of the Neoproterozoic and Paleozoic felsic igneous rocks from the inboard Ganderian terranes. The low-[sup.18]O character of the Neoproterozoic igneous rocks is related to regional pervasive, post-magmatic alteration by predominantly meteoric-hydrothermal fluids (δ[.sup.18][O.sub.H2O] ~ -6‰ to -4‰) at 200-450 °C. The alteration likely occurred during late Neoproterozoic transtensional extension of Avalonia. Large-scale fluid infiltration and circulation within the Avalonian crust accompanied this extension with development of pull-apart sedimentary basins and extension-related magmatism that were the prelude to Cambrian submergence of Avalonia. This regional [sup.18]O depletion provides a geochemical fingerprint by which Avalonia can be distinguished from other peri-Gondwanan terranes. These data suggest that Avalonia existed as a composite terrane on the Gondwanan margin in the Neoproterozoic, separate from Ganderia. Un appauvrissement en [sup.18]O est caracteristique d'une grande partie des roches ignees felsiques, 620-550 Ma, de l'Avalonia dans le nord de l'orogene appalachien. Les roches neoproterozoiques du terrane Boston Avalon ont les valeurs δ[sup.18][O.sub.WR] les plus faibles (≥-3,1 ‰), suivies du terrane Mira dans l'Ele du Cap Breton et le terrane Caledonia au Nouveau-Brunswick (≥-1,2 ‰), du terrane Avalon a Terre-Neuve (≥+2,8 ‰) et dans les terres hautes de l'Antigonish en Nouvelle-Ecosse (≥+5,3 ‰). Par contre, cet appauvrissement en [sup.18]O est observe dans tres peu de roches ignees felsiques paleozoiques de ces terranes d'Avalon et aussi dans tres peu de roches felsiques ignees neoproterozoiques et paleozoiques des terranes interieurs de Gander. La faible teneur en [sup.18]O des roches ignees neoproterozoiques est liee a une alteration postmagmatique regionale penetrante par des fluides hydrothermaux principalement meteoriques (δ[.sup.18][O.sub.H2O] ~ -6 a -4 ‰) a 200-450 °C. L'alteration est probablement survenue au cours de l'extension de tension transverse d'Avalonia au cours du Neoproterozoique tardif. Une infiltration et une circulation de fluides a grande echelle a l'interieur de la croite avalonienne a accompagne cette extension avec le developpement de bassins sedimentaires d'etirement et d'un magmatisme relie a l'extension qui forment le prelude a la submersion d'Avalonia au Cambrien. Cet appauvrissement regional en [sup.18]O fournit une signature geochimique par laquelle le terrane d'Avalonia peut etre distingue d'autres terranes peri-Gondwana. Selon ces donnees, Avalonia aurait existe en tant que terrane composite sur la bordure gondwanienne au Neoproterozoique, separe de Ganderia., [Traduit par la Redaction] Introduction The comparative tectonostratigraphic histories and relationships among the peri-Gondwanan composite terranes comprising Avalonia and Ganderia in the northern Appalachian orogen have been the subject of [...]

ABSTRACT A major ductile high-strain zone up to 5 km in width can be traced for at least 70 km diagonally across the Avalonian Caledonia terrane of southern New Brunswick. [...]

ABSTRACT The Mechanic Settlement Pluton, southern New Brunswick, is a high-level mafic-ultramafic pluton of Late Neoproterozoic age (ca. 557 Ma). Based on surface-outcrop and drill-core samples, the pluton includes six [...]

Abstract: A prominent positive magnetic anomaly spans the 100 km distance between Prince Edward Island and Cape Breton Island in the southern Gulf of St. Lawrence. The anomaly occurs in [...]

Abstract: The Seal Island Pluton outcrops only on small islands located on the continental shelf 45 km south of Nova Scotia, although geophysical data indicate that the pluton is part [...]

ABSTRACT The Lower Coverdale intrusion near Moncton, New Brunswick, has been intersected in drill holes at depths of 100-200 m below unconformably overlying Carboniferous sandstone, conglomerate and, locally, limestone of [...]

ABSTRACT The northeastern part of Kaipokok Bay is located in the Makkovik Province of Labrador, in the boundary zone between the Kaipokok and Aillik domains. The Kaipokok domain is characterized [...]

ABSTRACT The islands known as The Wolves are located in the Bay of Fundy, approximately 10 km offshore from mainland southwestern New Brunswick. They are underlain by monzodiorite, gradational to [...]

The Chiang Kahong volcanic suite forms the northeastern part of the Tak-Chiang Khong volcanic belt in the Sukhothai terrane of northern Thailand. It consists mainly of subaerial andesitic to rhyolitic tuffaceous rocks. A rhyolitic tuff yielded a Middle Triassic U-Pb (zircon) age of 232.9 [+ or -] 0.4 Ma. The suite displays calc-alkalic chemical trends and Nb, P, and Ti depletion characteristic of subduction-related magmatism. Based on petrological similarities, the suite is correlated with the c. 240 Ma Lampang volcanic rocks located farther to the SW in the Tak Chiang Khong belt, and with volcanic rocks of similar age in the Lincang--Jinghong belt in Yunnan, in the western part of the Simao block. These correlations support the placement of the Palaeo-Tethyan suture to the west of the Sukhothai terrane.

ABSTRACT Anomalously thick and coarse clastic sedimentary successions, including over 5000 m of conglomerate, are exposed on Isle Madame off the southern coast of Cape Breton Island. Two steeply to [...]

Abstract: Fossiliferous clasts occur in Carboniferous conglomerate in the Horton Group on western Isle Madame and in the Mabou Group on eastern Isle Madame. Most of the clasts (21 of [...]

SUMMARY Geoscience is a global discipline, and geoscientists are typically world travellers who recognize the need for effective international collaboration. Canadian geoscientists, in particular, have a long history of active [...]

ABSTRACT The Lochaber-Mulgrave area of northern mainland Nova Scotia is underlain by rocks of the Late Devonian- Early Carboniferous Horton Group, in faulted contact with older Devonian and Silurian rocks [...]

ABSTRACT A new U-Pb (zircon) age of 357 ± 1 Ma for the Wedgeport pluton in the Meguma terrane of southwestern Nova Scotia confirms that it is younger than other [...]

ABSTRACT Late Proterozoic to Early Cambrian igneous rocks are major components of the fault-bounded Caledonia, Brookville, and New River terranes of southern New Brunswick. As previously demonstrated, ca. 620 Ma [...]

The fault-bounded Kingston terrane of southern New Brunswick consists of felsic and less abundant mafic volcaniclastic rocks and flows and minor interbedded sedimentary rocks of the Kingston Group intruded by mainly granitic plutons and abundant younger mafic sheets. The granitic plutons form about half of the terrane and are characterized by fine grain size and typically granophyric and porphyritic textures, indicative of high-level emplacement. Mafic sheets were emplaced in the granitic plutons and parallel to primary layering in the Kingston Group, which is typically steeply dipping and trends northeast to north-northeast. Hence, in contrast to some earlier interpretations, the Kingston terrane does not consist of a bimodai dike complex. The Kingston Group, granitic rocks, and mafic sheets contain mineral assemblages consistent with metamorphism to upper greenschist-lower amphibolite facies. New U-Pb (zircon) ages of 442 [+ or -] 6 Ma from a dacitic tuff unit and 437 [+ or -] 10 Ma from a granitic pluton corroborate previous U-Pb dates that had suggested that the volcanic and granitic rocks in the Kingston terrane are Early Silurian, rather than Precambrian, as had been earlier assumed. The felsic volcanic and granitic rocks are interpreted to be comagmatic on the basis of their field relationships and similar U-Pb ages and chemical character. Compositions of both the felsic rocks and less abundant mafic and intermediate and mafic rocks are consistent with calc-alkalic affinity and emplacement in a continental-margin volcanic arc, herein termed the Kingston arc. A U-Pb date of 435 [+ or -] 5 Ma was also obtained from compositionally similar granite that forms a dike in an adjacent fault-bounded amphibolite-facies metasedimentary unit. The similarity in age and composition of the granite dike suggests a link between these metasedimentary rocks and the Kingston terrane, possibly as part of an accretionary complex. If so, its location southeast of the Kingston terrane indicates that subduction was to the present northwest. Mafic sheets in the Kingston terrane are tholeiitic but have some arc-like characteristics, consistent with their origin in a former arc setting, but the sheets were likely emplaced in a subsequent extensional setting. The compositional similarity of the mafic sheets to Late Silurian mafic volcanic rocks and plutons of the Coastal Maine magmatic province suggests that they may be related. A possible model for evolution of the Kingston terrane is proposed, wherein the Kingston Group and related granite formed in an Early Silurian arc on the margin of Ganderia, as represented by the New River terrane of late Precambrian and early Paleozoic age. Northwestward subduction culminated in collision between the Kingston arc and a continental block now represented by the Brookville terrane to the southeast. Subsequent transpressive motions in the Late Silurian may have been responsible for the crustalscale extensional environment in which the Coastal Maine magmatic province was formed, including emplacement of mafic dikes into the deformed former Kingston arc. Transpressive motions-related to juxtaposition of the Avalon and Meguma terranes with the previously accreted, more inboard terranes--continued through the Devonian and into the Carboniferous. Keywords: Appalachians, geochemistry, Silurian, U-Pb dating, volcanic arcs.

ABSTRACT Latest Neoproterozoic and Cambrian plutons in the Brookville terrane of southern New Brunswick are termed the Golden Grove Plutonic Suite. Four groups are recognized on the basis of composition: [...]

Gabbro from the Caledonia Mountain Pluton in the northeastern Caledonian Highlands of southern New Brunswick yielded a U-Pb (zircon) crystallization age of 615 ± 1 Ma. The age shows that [...]

The source regions of magmas under Cape Breton Island, Nova Scotia, Canada have been investigated using Pb and O isotopic data from felsic plutons. The Aspy terrane rock constitution has been found to be different from the Blair River Complex rocks which have the most primitive Pb, low and narrow range of delta-18 O values, and a different Nd isotopic composition. The isotopic values indicate towards mantle-derived, hybridized, crust-contaminated magmas. The Pb isotopic data agree well with an Nd isotopic study on plutons from Cape Breton Island.

U-Pb geochronological studies were carried out to understand the evolution of the Aspy terrane, Cape Breton Island and to study the relationships between Aspy and Bras d'Or terranes and Ganderia in the Canadian Appalachians.

The West Branch North River (WBNR), Bothan Brook (BB), Centre Road (CR), and Peter Brook (PB) plutons are in the Aspy terrane of central Cape Breton Island, part of Ganderia in the northern Appalachian orogen. The plutons are elongate parallel to regional trends but are undeformed and appear to have been emplaced after Acadian deformation in the area. U-Pb zircon dating has confirmed previously assumed late Devonian ages of ca. 370-360 Ma. No petrological studies have been done on these plutons since the 1980s, and their mineralization potential and tectonic setting have not been investigated. Preliminary petrographic examination of cut slabs and thin sections from about 40 samples collected as part of regional mapping projects that included these plutons show a wide range in rock types from monzodiorite to syenogranite. Samples from WBNR, BB, and PB plutons consist mostly of medium-to coarse-grained equigranular biotite monzogranite, whereas the CR pluton includes both hornblende-biotite monzodiorite and quartz monzonite. Chemical analyses of 33 samples range in SiO2 content from about 53% to 77%, with lowest contents in samples from the CR pluton and the highest in the BB pluton. Most samples have high K2O contents suggesting that they are of shoshonitic affinity. Trace element compositions indicate that they formed in a subduction-related environment, perhaps from magmas generated in a post-collisional slab-failure tectonic setting. Although no mineralization has been observed, the highly evolved compositions in the BB pluton suggest some potential for Li or other critical elements. [ABSTRACT FROM AUTHOR]