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The Bras d'Or terrane of central Cape Breton Island, Nova Scotia, Canada, contains a well-preserved record of the Ediacaran to early Cambrian evolution of Ganderia, a Gondwana-derived terrane in the northern Appalachian orogen. A complex assemblage of low- to high-grade metasedimentary rocks has varied detrital zircon signatures from laser ablation inductively coupled plasma mass spectrometry U-Pb zircon dating, but combining three or more samples yielded representative age spectra that support correlation of the low- and high-grade metasedimentary rocks throughout the Bras d'Or terrane and the corresponding Ganderian Brookville terrane of southern New Brunswick. In quartzite samples from the McMillan Flowage Formation in the northwestern Bras d'Or terrane, the youngest detrital zircons have ages >900 Ma, in contrast to previously studied psammitic and semipelitic samples from correlative units in the eastern Bras d'Or terrane in which youngest detrital ages are 620–600 Ma. Both quartzite and semipelitic samples from the McMillan Flowage Formation contain Neoproterozoic dates from zircon rims, which reflect metamorphic overgrowths during peak metamorphism at ca. 550 Ma, providing a robust age for peak metamorphism in the Bras d'Or terrane that supports similar, albeit sparse, ages reported previously from monazite and titanite samples. This metamorphism is coeval with the emplacement of voluminous dioritic to granitic plutons that occur throughout the Bras d'Or terrane and form in an Andean-type continental margin subduction zone. New U-Pb zircon ages presented here from plutons in the northern Bras d'Or terrane, combined with previously published ages, are consistent with subduction-related magmatism and associated metamorphism between ca. 575 and 540 Ma. [ABSTRACT FROM AUTHOR]

Zircon grains from metasiltstone beds in the Precambrian Ashburn Formation were dated to constrain the age of the stromatolite Archaeozoon acadiense. The largest group of analyzed grains consists of mostly well-rounded detrital zircon no younger than 1060 Ma with significant peaks at about 1200–1100, 1500, 1800, 2050, and 2700 Ma, as well as a few Mesoarchean ages. A second population of apparently euhedral grains gives ages in the range 680–400 Ma. The distribution of detrital zircon ages along with field relationships suggest that the Ashburn and Martinon formations are proximal and distal parts of the Green Head Group, respectively, and hence a previously reported maximum depositional age of ca. 602 ± 8 Ma for the Martinon Formation also applies to stromatolite in the Ashburn Formation. Paleozoic zircon recovered from the Ashburn Formation cannot be detrital because the rocks were intruded and contact metamorphosed by the Golden Grove Plutonic Suite at ca. 550–525 Ma. The Paleozoic zircon grains were found in four independently processed samples and have also been seen in other studies in the region, showing that they are not due to laboratory contamination. Zircon formed during younger magmatic activity may have been transported in hydrothermal fluids and emplaced into these metasedimentary rocks in veins. A single euhedral zircon recovered from an atypically thick vein gave an age of 659 ± 33 Ma. Hydrothermally transported zircon might provide a window into younger igneous processes for which evidence is not otherwise preserved in this and other areas. [ABSTRACT FROM AUTHOR]

Devonian granitoid plutons comprise a major part of the bedrock of northwestern Maine representing the magmatic expression of the Acadian orogeny in this part of the northern Appalachian orogen. They are petrographically diverse with minerals characteristic of both I- and S-type granites, in some cases within the same intrusion, and some are compositionally zoned. New LA-ICP-MS ages presented here elucidate the timing and duration of this magmatism. The earliest phase of granitoid magmatism began around 410-405 Ma with the emplacement of the Flagstaff Lake Igneous Complex, and the presence of contemporaneous mafic rocks suggests that mantle-derived magmas were also produced at this time. Late Devonian ages, ca. 365 Ma, for many intrusions, such as the Chain of Ponds and Songo plutons, reveal that magmatism continued for 45 million years during which compositionally diverse I- and S-type magmas were produced. In addition, there is evidence that intrusive activity was prolonged within some plutons, for example the Rome-Norridgewock pluton and the Mooselookmeguntic Igneous Complex, with 10-15 myr between intrusive units. The new ages suggest a break in magmatism between 400 Ma and 390 Ma apparently separating Acadian magmatism into early and late pulses. The production of lower crustal I-type magmas appears to have been concentrated later, ca. 380-365 Ma, although several S-type granitoids were also emplaced during this period. These Late Devonian plutons display abundant zircon inheritance with ages around 385 Ma, which suggests that the crust was experiencing enhanced thermal perturbations during this extended timeframe. The new data for granitoid plutons in northwestern Maine are consistent with tectonic models for other parts of Ganderia which propose initial flat slab subduction followed by slab breakoff and delamination. [ABSTRACT FROM AUTHOR]

New U-Pb zircon ages from volcanic, plutonic, and sedimentary units in the Avalonian Caledonia terrane of southern New Brunswick provide better timing constraints in this geologically complex area. Previous ca. 620 Ma ages from the Broad River Group are now corroborated by additional dates from felsic tuff in the Gordon Falls Formation and rhyolite in the former Fairfield (now East Branch Black River) Formation of 620 ± 5 Ma and 622 ± 1.9 Ma, respectively. Combined with ages ranging from ca. 625 Ma to 615 Ma from crosscutting plutons, the data suggest that the minimum age of the Broad River Group is about 615 Ma. A quartzfeldspar porphyry dyke in mafic volcanic rocks of the previously undated Long Beach Formation yielded an igneous crystallization age of 685 ± 10 Ma, the oldest unit yet dated in the Caledonia terrane but similar in age to porphyry in the Stirling belt in the Avalonian Mira terrane of Nova Scotia. The age of the Coldbrook Group was constrained previously by U-Pb (zircon) ages of volcanic rocks between 560 and 550 Ma as well as by similar ages from comagmatic plutons. Five additional samples from both volcanic and plutonic units lie in the same range of 560-550 Ma, including errors, demonstrating that the Coldbrook Group and related plutons formed in less than 10 million years. Such a large volume of mainly felsic magma erupted and emplaced in a short time span suggests a "supereruption/supervolcano" environment such as the late Cenozoic southwestern USA but not yet recognized at ca. 560-550 Ma elsewhere in Avalonia. Two units yielded Paleozoic ages: felsite of the Bloomsbury Mountain Formation with a zircon population at 427 ± 9 Ma, indicating a Silurian maximum emplacement age, and dacite of the Grassy Lake Formation with several zircon grains at 382.8 ± 8.3 Ma, indicating a maximum age of middle Devonian, the first rocks of this age to be identified in the Caledonia terrane. [ABSTRACT FROM AUTHOR]

Zircon grains from a granitic pegmatite clast from conglomerate at the base of the Ross Island Formation on Grand Manan Island indicate an igneous crystallization age of 664.1 ± 4.6 Ma. The clast also contains abundant older inherited grains back to the Archean. Muscovite in the same clast and an additional similar clast yielded cooling ages of 607.0 ± 3.7 Ma and 619.6 ± 4.1 Ma, respectively, providing a maximum depositional age for the host conglomerate of the Ross Island Formation. The Seven Hundred Acre Island Formation in the Islesboro block in Penobscot Bay, Maine, contains a granitic pegmatite dyke of similar age, suggesting that it was close to the site of deposition of the Ross Island Formation of Grand Manan Island in the late Ediacaran. This suggestion is supported further by similarity in rock types and detrital zircon spectra between the Seven Hundred Acre Island Formation and the Thoroughfare and Kent Island formations on Grand Manan Island. [ABSTRACT FROM AUTHOR]

Granitoid plutons are a major component of pre-Carboniferous rocks in Cape Breton Island and knowledge of the time and tectonic setting of their emplacement is crucial for understanding the geological history of the island, guiding exploration for granite-related economic mineralization, and making alongorogen correlations. The distribution of these plutons and their petrological characteristics have been used in the past for recognizing both Laurentian and peri-Gondwanan components in Cape Breton Island, and for subdividing the peri-Gondwanan components into Ganderian and Avalonian terranes. However, ages of many plutons were assumed on the basis of field relations and petrological features compared to those of the relatively few reliably dated plutons. Seventeen new U-Pb (zircon) ages from igneous units reported here provide enhanced understanding of the distribution of pluton ages. Arc-related plutons in the Aspy terrane with ages of ca. 490 to 475 Ma likely record the Penobscottian tectonomagmatic event recognized in the Exploits subzone of central Newfoundland and New Brunswick but not previously recognized in Cape Breton Island. Arc-related Devonian plutonic activity in the same terrane is more widespread, continuous, and protracted (445 Ma to 395 Ma) than previously known. Late Devonian magmatism in the Ganderian Aspy terrane is similar in age to that in the Avalonian Mira terrane (380 to 360 Ma) but the tectonic settings are different. In contrast, magmatic activity in the Bras d'Or terrane is almost exclusively arc-related in the Late Ediacaran (580 to 540 Ma) and rift-related in the Late Cambrian (520 to 490 Ma). The new data support the terrane distinctions previously documented. [ABSTRACT FROM AUTHOR]

40Ar/39Ar in situ UV laser ablation of white mica, Rb–Sr mineral isochrons and zircon fission track dating were applied to determine ages of very low- to low-grade metamorphic processes at 3.5±0.4 kbar, 280±30°C in the Avalonian Mira terrane of SE Cape Breton Island (Nova Scotia). The Mira terrane comprises Neoproterozoic volcanic-arc rocks overlain by Cambrian sedimentary rocks. Crystallization of metamorphic white mica was dated in six metavolcanic samples by 40Ar/39Ar spot age peaks between 396±3 and 363±14 Ma. Rb–Sr systematics of minerals and mineral aggregates yielded two isochrons at 389±7 Ma and 365±8 Ma, corroborating equilibrium conditions during very low- to low-grade metamorphism. The dated white mica is oriented parallel to foliations produced by sinistral strike-slip faulting and/or folding related to the Middle–Late Devonian transpressive assembly of Avalonian terranes during convergence and emplacement of the neighbouring Meguma terrane. Exhumation occurred earlier in the NW Mira terrane than in the SE. Transpression was related to the closure of the Rheic Ocean between Gondwana and Laurussia by NW-directed convergence. The 40Ar/39Ar spot age spectra also display relict age peaks at 477–465 Ma, 439 Ma and 420–428 Ma attributed to deformation and fluid access, possibly related to the collision of Avalonia with composite Laurentia or to earlier Ordovician–Silurian rifting. Fission track ages of zircon from Mira terrane samples range between 242±18 and 225±21 Ma and reflect late Palaeozoic reburial and reheating close to previous peak metamorphic temperatures under fluid-absent conditions during rifting prior to opening of the Central Atlantic Ocean. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Brookville terrane represents ca. 650Ma passive margin of Puncoviscana Ocean. [•] Formed on Proto-Andean-Caribbean edge of Amazonia. [•] Dominated by Meso- and Paleoproterozoic detrital zircon ages. [•] Active margin in Late Neoproterozoic-Cambrian. [•] Separated in mid-Cambrian to become the foundation of Ganderia. [Copyright &y& Elsevier]

A quartz sandstone bed in a dominantly conglomeratic section in the central part of the Lower Carboniferous Horton Group on Petit-de-Grat Island, offshore southern Cape Breton Island, Nova Scotia, contains detrital zircon grains with ages ranging from mid-Devonian to Archean. The similarity of the Devonian and Neoproterozoic age spectrum to ages of igneous units in the adjacent Avalonian Mira terrane, in particular the Coastalbelt, indicates that it was the main source area. This interpretation is supported by the similarity of the Neoproterozoic and older detrital zircon age spectrum to that of the detritalzircon age spectrum in a Cambrian sandstone unit from the Miraterrane. This interpretation indicates post-depositional dextral fault motion between the Isle Madame area and the Coastal belt. [ABSTRACT FROM AUTHOR]

The article discusses a field trip which highlights the unique geology of the Meguma terrane of southern Nova Scotia, the most easterly component of the northern Appalachian orogen. The Meguma terrane is described as a thick package of Early Cambrian to Early Ordovician turbiditic metasandstone and slate, locally overlain unconformably by a thin sequence of slate, quartzite and volcanic rocks. It suggests that the Meguma terrane was formed in a rift between Gondwana and Avalonia as shown by the stratigraphic differences across the Chebogue Point shear zone together with similarities to Avalonian detrital zircon populations, juvenile Nd isotopic compositions and sparse faunal evidence indicating Avalonian affinity.

Neoproterozoic though Cambrian clastic sedimentary and/or metasedimentary rocks occur in the Hammondvale Metamorphic Suite (HMS; ca. 680-620 Ma) and the Broad River (ca. 620 Ma), Coldbrook (ca. 560-550 Ma), and Saint John (ca. 540-490 Ma) groups in the Avalonian Caledonia terrane of southern New Brunswick. Evolved Nd isotopic values show that the HMS and the metasedimentary rocks of the Broad River Group were in part derived from older cratonic material. The presence of Mesoproterozoic and the absence of Paleoproterozoic zircon in the HMS suggest that the source of this older cratonic material was the Amazonian craton. In contrast, sedimentary rocks of the Coldbrook Group show generally positive ϵNd values and likely were derived from local Avalonian sources. More evolved isotopic signatures in the lower Saint John Group indicate a return to older cratonic source areas. Detrital zircon from the lowest part of the Saint John Group has Mesoproterozoic ages like those of the HMS but also has 2000- and 800-Ma ages. The Mesoproterozoic grains are likely from Amazonia, but the additional 2000-800-Ma grains suggest a new source area, likely the West African craton. The increasingly evolved Nd isotopic values, the absence of Mesoproterozoic zircon, and the addition of 2000- and 800-Ma zircon in Early Cambrian sediments suggest that by the Early Cambrian Avalonia was deriving detritus exclusively from the West African craton. This transition in provenance apparently started after transtensional rifting recorded by volcanic and sedimentary rocks in the Coldbrook Group and continued through the Cambrian as Avalonia moved along strike-slip faults from its location along the Amazonian margin closer to the West African margin before starting its journey to Laurentia. [ABSTRACT FROM AUTHOR]

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 (Grand Manan Island belt), Matthews Lake (New River belt), Ellsworth (Ellsworth belt), Calais (St. Croix belt), and Baskahegan Lake (Miramichi belt). Their maximum age of deposition is based on the youngest detrital zircon population and minimum age of deposition based on stratigraphic, paleontological, and cross-cutting intrusive relationships. The determined range of depositional ages are: Martinon between 602 ± 8 (youngest zircons) and 546 ± 2 Ma (age of cross-cutting intrusion); Flagg Cove between 574 ± 7 (youngest zircons) and 535 ± 3 Ma (age of cross-cutting intrusion); Matthews Lake between 539 ± 5 (youngest zircons) and 514 ± 2 Ma (age of overlying volcanic rocks); Ellsworth between 507 ± 6 (youngest zircons) and 504 ± 3 Ma (age of overlying volcanic rocks); Calais between 510 ± 8 (youngest zircons) and 479 ± 2 Ma (graptolite zone); and Baskahegan Lake between 525 ± 6 (youngest zircons) and 488 ± 2 Ma (graptolite zone). All samples are dominated by Neoproterozoic (Gondwanan) zircon populations. The Early Paleozoic Matthews Lake, Ellsworth, and Calais formations contain main population peaks at 539 ± 5 Ma, 545 ± 4 Ma, and 556 ± 7 Ma, respectively, consistent with derivation mainly from magmatic rocks of the Brookville, Grand Manan Island, and/or New River belts, previously dated at ~553 to ~528 Ma. In contrast, the main peak in the Early Paleozoic Baskahegan Lake Formation is older at 585 ± 5 Ma. The main peak in the Neoproterozoic to Early Cambrian Flagg Cove Formation is at 611 ± 7 Ma with a secondary peak at 574 ± 7 Ma; the former was likely derived from locally exposed igneous units dated at ~618 to ~611 Ma. The Neoproterozoic Martinon Formation exhibits dominant peaks at 674 ± 8 Ma and 635 ± 4 Ma. Ganderian basement gneiss dated at ~675 Ma and intruded by plutonic rocks dated at ~584 Ma in the Hermitage Flexure of Newfoundland are possible sources for these older zircon components in the Martinon and Baskahegan Lake formations. Plutonic rocks in the New River belt dated at ~629 to ~622 Ma may be the source of the younger component in the Martinon Formation. The samples also contain a small number of Mesoproterozoic, Paleoproterozoic, and Archean zircon grains, the latter as old as 3.23 Ga. The presence of zircons in the range 1.07 to 1.61 Ga is consistent with an origin along the peri-Gondwanan margin of Amazonia rather than West Africa. The general similarity of zircon provenance for samples from New Brunswick and coastal Maine suggests that all the Ganderian belts were part of a single microcontinent rifted from the Amazonian craton. The Grand Manan Island and New River belts both record two distinct periods of Neoproterozoic arc magmatism (~629 to ~611 Ma and at ~553 to ~535 Ma) whereas the Brookville belt experienced only a single period of arc magmatism lasting from ~553 to ~528 Ma. These differences are attributed to migration of the younger period of arc magmatism further inboard into Ganderia due to shallowing of the subduction zone. A Penobscot rifted arc system is recorded in the New River and Ellsworth belts from ~514 to ~502 Ma, following migration of Ganderia into the widening Iapetus Ocean. The progressively younger depositional ages of the quartzose sandstone sequences of the Brookvlle belt (Martinon Formation), Grand Manan Island belt (Flagg Cove Formation) and New River belt (Matthews Lake Formation) can be attributed to these episodic periods of quiescence and arc activity along the convergent margin of Ganderia.… [ABSTRACT FROM AUTHOR]

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Fifteen U–Pb (zircon) radiometric age determinations have been made on igneous rocks of Middle Devonian to Early Carboniferous age from the southern margin of the Magdalen basin in Cape Breton Island and northern mainland Nova Scotia. Volcanic rocks interbed with early rift-basin sedimentary rocks with some palynological biostratigraphy; dated intrusive rocks cut these sedimentary units. Our biostratigraphically constrained ages are in close agreement with the current Devonian time scale. Combined with previously published data, the age determinations show that igneous activity occurred in four pulses: Middle Devonian (390–385 Ma), early Late Devonian (375–370 Ma), latest Devonian to early Tournaisian (365–354 Ma), and late Tournaisian to early Visean (ca. 339 Ma). Middle Devonian (385–389 Ma) volcanic rocks are confined to the Guysborough Group. The Fisset Brook Formation (basalt and minor rhyolite) in the type area and elsewhere in Cape Breton Island and northern mainland Nova Scotia is Late Devonian (ca. 373 Ma), whereas the biostratigraphically distinct succession at Lowland Cove is younger (365 Ma). These Late Devonian rocks are synchronous with plutonism in the Cape Breton Highlands and the Meguma terrane. In the Cobequid Highlands, rhyolite of the Fountain Lake Group was synchronous with Horton Group deposition and with widespread granite plutons (362–358 Ma) emplaced during shear on the Cobequid fault zone. The overlying Diamond Brook Formation basalts are slightly younger (355 Ma). Late Tournaisian – early Visean mafic intrusions and minor basalt occur along the Cobequid – Chedabucto fault zone and in a belt from southern New Brunswick through Prince Edward Island to southwestern Cape Breton Island.Quinze déterminations d'âge par radiométrie U–Pb (zircon) ont été effectuées sur des roches ignées (Dévonien moyen au Carbonifère précoce) de la bordure sud du bassin de la Madeleine sur l'île du Cap Breton et le nord de la partie continentale de la Nouvelle-Écosse. Des roches volcaniques sont interstratifiées avec des roches sédimentaires d'un bassin de fosse précoce contenant un peu de biostratigraphie palynologique; des roches intrusives dont les âges sont connus recoupent ces unités sédimentaires. Les âges que nous avons obtenus biostratigraphiquement concordent de près avec l'échelle dévonienne actuelle. Combinées aux données publiées antérieurement, les déterminations d'âge montrent que l'activité ignée a eu lieu en quatre impulsions : Dévonien moyen (390–385 Ma), Dévonien tardif précoce (375–370 Ma), Dévonien terminal au Tournaisien précoce (365–354 Ma), et Tournaisien tardif au Viséen précoce (~339 Ma). Les roches du Dévonien moyen (385–389 Ma) sont restreintes au Groupe de Guysborough. La Formation de Fisset Brook (du basalte et un peu de rhyolite) dans l'endroit type et ailleurs dans l'île du Cap Breton et le nord de la partie continentale de la Nouvelle-Écosse date du Dévonien tardif (~373 Ma), alors que la succession biostratigraphiquement distincte de Lowland Cove est plus jeune (365 Ma). Ces roches du Dévonien tardif sont synchrones au plutonisme dans les terres hautes du Cap Breton et du terrane de Meguma. Dans les terres hautes de Cobequid, la rhyolite du Groupe de Fountain Lake était synchrone à la déposition du Groupe de Horton et à la mise en place de très nombreux plutons granitiques (362–358 Ma) durant le cisaillement dans la zone de faille de Cobequid. Les basaltes de la Formation de Diamond Brook sus-jacente sont légèrement plus jeunes (355 Ma). Des intrusions mafiques et un peu de basalte du Tournaisien tardif – Viséen précoce se trouvent le long de la zone de faille Cobequid – Chedabucto et dans une ceinture qui va du sud du Nouveau-Brunswick, à travers l'Île du Prince Édouard jusqu'à l'île du Cap Breton.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

New U–Pb zircon, titanite, and monazite ages reported here, along with existing age data, demonstrate that granitoid bodies in the northwestern segment of the Paleoproterozoic Makkovik Province, Labrador, are of three distinct ages. The redefined Island Harbour Bay plutonic suite consists of varied dioritic to granitic units that were syntectonically emplaced into Archean crust of the Kaipokok domain between ca. 1895 Ma and 1870 ± 2 Ma. This plutonism occurred during the early stages of the Makkovikian Orogeny in an obliquely convergent, Andean continental margin setting. The Hares Islands and Drunken Harbour granites form smaller, discrete plutons that were emplaced in or adjacent to the Island Harbour Bay plutonic suite at 1805 ± 5 Ma and 1791 ± 2 Ma, respectively, during dextral strike-slip deformation that accompanied accretion of an outboard juvenile terrane. Magmatic activity during this period was preferentially sited along active structural zones, but also occurred outside of these zones. The undeformed Blacklers Bight A-type granite was emplaced in the Kaipokok domain at 1716 ± 1 Ma, late in the development of the orogen. A-type granites of this age form a significant component of the southeastern Makkovik Province, and their generation is linked to mafic underplating and heterogeneous regional extension. The new age data support the conclusion of earlier workers that crustal growth via synorogenic and postorogenic plutonism was episodic, and allow, along with field and geochemical data, inferences to be made regarding the tectonic setting of individual plutonic events.Les nouveaux âges U–Pb sur du zircon, de la titanite et de la monazite, rapportés ici avec certaines données d'âge déjà existantes, démontrent que des amas granitoïdes dans le segment nord-ouest de la province de Makkovik, du Paléoprotérozoïque, au Labrador, sont de trois âges distincts. La suite plutonique Island Harbour Bay redéfinie comprend des unités dioritiques à granitiques variées qui ont été mises en place syntectoniquement dans la croûte archéenne du domaine Kaipokok il y a environ 1895 à 1870 ± 2 Ma. Ce plutonisme a eu lieu au cours des premiers stages de l'orogénie makkovikienne dans un environnement de marge continentale andin à convergence oblique. Les granites de Hares Islands et de Drunken Harbour forment de plus petits plutons distincts qui ont été mis en place dans la suite plutonique Island Bay Harbour ou adjacents à cette dernière respectivement à 1805 ± 5 Ma et 1791 ± 2 Ma, au cours d'une déformation dextre qui a accompagné l'accrétion d'un terrane juvénile extérieur. L'activité magmatique au cours de cette période était localisée surtout le long de zones structurales actives mais elle a aussi eu lieu en dehors de ces zones. Blacklers Bight, le granite non déformé de type A, a été mis en place dans le domaine de Kaipokok ca. 1716 ± 1 Ma, soit tard dans le développement de l'orogène. Des granites de type A de cet âge sont une composante significative de la province Makkovik du sud-est et leur génération est liée à une remontée de magma mafique sous les plaques et à une extension hétérogène régionale. Les nouvelles données d'âge supportent les conclusions de travailleurs précédents à savoir que la croissance de la croûte par du plutonisme syn- et post orogénique était épisodique et permettaient, avec les données de terrain et géochemiques, de tirer des conclusions sur l'environnement tectonique d'événements plutoniques individuels.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Basement rocks from the Continental Offshore Stratigraphic Test (COST) No. G-1 petroleum exploration well, Georges Bank, offshore Massachusetts, USA, show the first direct evidence for a fragment of Paleoproterozoic West African crust preserved along the eastern North American continental margin. Detrital zircon from two metawacke samples near the base of the core yielded ca. 3.05-1.90 Ga laser ablation-inductively coupled plasma-mass spectrometry dates, with a predominant 2.2-2.0 Ga population. This detrital zircon signature is consistent with that in the Taghdout Group of the Anti-Atlas region, which is part of the Paleoproterozoic passive margin rocks deposited directly on the Archean-Paleoproterozoic WAC shortly after its formation. African provenance has previously been recognized for the Suwannee and Meguma terranes in the southern and northern Appalachians, respectively. However, these areas represent Neoproterozoic-Paleozoic sedimentary basins, deposited well over a billion years after formation of the Paleoproterozoic WAC and cover rocks, including those in the COST No. G-1 well. The Paleoproterozoic rocks in the COST No. G-1 well were likely amalgamated with the North American margin during final closure of the Rheic Ocean and assembly of Pangea near the end of the Paleozoic. [ABSTRACT FROM AUTHOR]