Early Ordovician rifting of Avalonia and birth of the Rheic Ocean: U–Pb detrital zircon constraints from Newfoundland

Pollock, Jeffrey C.; Hibbard, James P.; Sylvester, Paul J.

doi:10.1144/0016-76492008-088

Cited by 99 publications

(75 citation statements)

References 86 publications

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“…Figure 11 shows a possible terrane configuration consistent with this hypothesis, based on the assumption that Megumia was located within a rift system between East and West Avalonia. This model is consistent with both the sinistral transpressional setting for the Menai Strait Fault System, with the likely initial position of Ganderia (e.g., Pollock et al 2009;van Staal et al 2012) along the Amazonian margin, and with substantial rotation of portions of Avalonia during later Paleozoic history as suggested by Vizan et al (2003).…”

Section: Relationship To the Welsh Basinsupporting

confidence: 80%

Stratigraphy, provenance and tectonic setting of the Lumsden Dam and Bluestone Quarry formations (Lower Ordovician), Halifax Group, Nova Scotia, Canada

Pothier¹,

Waldron

White

et al. 2015

atgeol

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Cambrian to Ordovician metamorphosed clastic sedimentary rocks of the Meguma terrane have no correlatives elsewhere in Atlantic Canada but are similar to successions in North Wales. In the Meguma terrane, the Cambrian Goldenville Group, dominated by sandstone, is overlain by the Halifax Group, consisting mainly of fine-grained slate and siltstone. Within the Halifax Group widespread Furongian black slate units are overlain by greyer units with rare Early Ordovician fossils, assigned to the laterally equivalent Bear River, Feltzen, Bluestone Quarry, Lumsden Dam and Glen Brook formations. The type section of the Bluestone Quarry Formation, here defined, is on Halifax Peninsula, where four constituent members are recognized; the type section of the Lumsden Dam Formation is here defined in the Lumsden Dam region near Wolfville. Detrital zircons extracted from a sample of the Lumsden Dam Formation show a range of ages similar to those displayed by the underlying Goldenville Group, including abundant Neoproterozoic zircon representing Avalonian or Pan-African sources, and a prominent group of peaks between 1.95 and 2.2 Ga, probably representing sources in West Africa. A sample from the Glen Brook Formation east of Halifax shows a similar distribution. In contrast to the correlative Welsh successions, no influx of Mesoproterozoic zircon is seen in Early Ordovician samples, suggesting that, if the two basins were in close proximity in the Cambrian, they had diverged by the Early Ordovician, possibly as a result of strike-slip motion along the margin of Gondwana.

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Section: Relationship To the Welsh Basinsupporting

confidence: 80%

Stratigraphy, provenance and tectonic setting of the Lumsden Dam and Bluestone Quarry formations (Lower Ordovician), Halifax Group, Nova Scotia, Canada

Pothier¹,

Waldron

White

et al. 2015

atgeol

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“…The late Neoproterozoic to early Cambrian peak displayed by all the samples is typical of peri-Gondwanan basins, including the Meguma Terrane of Nova Scotia (Krogh and Keppie, 1990;Waldron et al, 2009), East Avalonia (Murphy et al, 2004b;Waldron et al, 2011), and West Avalonia (Pollock et al, 2009) and reflects sources derived from within the Avalonian/Panafrican orogens. The sample from the Gamlan Formation (ML001A) contains only a small number of older grains, making attribution of sources speculative.…”

Section: Discussionmentioning

confidence: 82%

Peri-Gondwanan terrane interactions recorded in the Cambrian–Ordovician detrital zircon geochronology of North Wales

et al. 2015

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“…Isotopic data were obtained by LA-ICPMS at the MicroAnalysis Facility at Memorial University, Newfoundland and closely follow the procedures outlined in Pollock et al (2009). Zircons were ablated in situ using a Lambda Physik COMPexPro 110 ArF excimer laser operating at a deep UV wavelength of 193 nm and a pulse width of 20 ns.…”

Section: U-pb Zircon Ages Of the Birchy Complex And Flat Point Formationmentioning

confidence: 99%

Evidence of Late Ediacaran Hyperextension of the Laurentian Iapetan Margin in the Birchy Complex, Baie Verte Peninsula, Northwest Newfoundland: Implications for the Opening of Iapetus, Formation of Peri-Laurentian Microcontinents and Taconic – Grampian Orogenesis

Staal

Chew

Zagorevski

et al. 2013

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The Birchy Complex of the Baie Verte Peninsula, northwestern Newfoundland, comprises an assemblage of mafic schist, ultramafic rocks, and metasedimentary rocks that are structurally sandwiched between overlying ca. 490 Ma ophiolite massifs of the Baie Verte oceanic tract and underlying metasedimentary rocks of the Fleur de Lys Supergroup of the Appalachian Humber margin. Birchy Complex gabbro yielded a Late Ediacaran U–Pb zircon ID–TIMS age of 558.3 ± 0.7 Ma, whereas gabbro and an intermediate tuffaceous schist yielded LA–ICPMS concordia zircon ages of 564 ± 7.5 Ma and 556 ± 4 Ma, respectively. These ages overlap the last phase of rift-related magmatism observed along the Humber margin of the northern Appalachians (565–550 Ma). The associated ultramafic rocks were exhumed by the Late Ediacaran and shed detritus into the interleaved sedimentary rocks. Psammite in the overlying Flat Point Formation yielded a detrital zircon population typical of the Laurentian Humber margin in the northern Appalachians. Age relationships and characteristics of the Birchy Complex and adjacent Rattling Brook Group suggest that the ultramafic rocks represent slices of continental lithospheric mantle exhumed onto the seafloor shortly before or coeval with magmatic accretion of mid-ocean ridge basalt-like mafic rocks. Hence, they represent the remnants of an ocean – continent transition zone formed during hyperextension of the Humber margin prior to establishment of a mid-ocean ridge farther outboard in the Iapetus Ocean. We propose that microcontinents such as Dashwoods and the Rattling Brook Group formed as a hanging wall block and an extensional crustal allochthon, respectively, analogous to the isolation of the Briançonnais block during the opening of the Alpine Ligurian–Piemonte and Valais oceanic seaways.SOMMAIRELe complexe de Birchy de la péninsule de Baie Verte, dans le nord-ouest de Terre-Neuve, est constitué d’un assemblage de schistes mafiques, de roches ultramafiques et de métasédiments qui sont coincés entre des massifs ophiolitiques d’ascendance océanique de la Baie Verte au-dessus, et des métasédiments du Supergroupe de Fleur de Lys de la marge de Humber des Appalaches en-dessous. Le complexe de gabbro de Birchy a donné une datation U-Pb sur zircon ID-TIMS correspondant à la fin de l’Édiacarien, soit 558,3 ± 0,7 Ma, alors qu’un gabbro et un schiste tufacé intermédiaire montrent une datation LA-ICP-MS Concordia sur zircon de 564 ± 7,5 Ma et 556 ± 4 Ma, respectivement. Ces datations chevauchent la dernière phase de magmatisme de rift observée le long de la marge Humber des Appalaches du Nord (565-550 Ma). Les roches ultramafiques associées ont été exhumées vers la fin de l’Édiacarien et leurs débris ont été imbriqués dans des roches sédimentaires. Les psammites de la Formation de Flat Point susjacente ont donné une population de zircons détritiques typique de la marge laurentienne de Humber des Appalaches du Nord. Les relations chronologiques et les caractéristiques du complexe de Birchy et du groupe de Rattling Brook adjacent, permettent de penser que ces roches ultramafiques pourraient être des écailles de manteau lithosphérique continental qui auraient été exhumées sur le plancher océanique peu avant ou en même temps que l’accrétion magmatique de roches mafiques basaltiques de type dorsale médio-océanique. Par conséquent, elles seraient des vestiges d’une zone de transition océan-continent formée au cours de l’hyper-extension de la marge de Humber avant l’apparition d’une dorsale médio-océanique plus loin au large dans l’océan Iapétus. Nous proposons que des microcontinents comme de Dashwoods et du groupe de Rattling Brook ont constitués respectivement un bloc de toit et un allochtone crustal d’extension, de la même manière que le bloc Briançonnais a été isolé lors de l’ouverture des bras océaniques alpins de Ligurie-Piémont et de Valais.

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Early Ordovician rifting of Avalonia and birth of the Rheic Ocean: U–Pb detrital zircon constraints from Newfoundland

Cited by 99 publications

References 86 publications

Stratigraphy, provenance and tectonic setting of the Lumsden Dam and Bluestone Quarry formations (Lower Ordovician), Halifax Group, Nova Scotia, Canada

Stratigraphy, provenance and tectonic setting of the Lumsden Dam and Bluestone Quarry formations (Lower Ordovician), Halifax Group, Nova Scotia, Canada

Peri-Gondwanan terrane interactions recorded in the Cambrian–Ordovician detrital zircon geochronology of North Wales

Evidence of Late Ediacaran Hyperextension of the Laurentian Iapetan Margin in the Birchy Complex, Baie Verte Peninsula, Northwest Newfoundland: Implications for the Opening of Iapetus, Formation of Peri-Laurentian Microcontinents and Taconic – Grampian Orogenesis

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