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New geochronological data on Palaeozoic igneous activity and deformation in the Severnaya Zemlya Archipelago, Russia, and implications for the development of the Eurasian Arctic margin
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics. (orogen dynamik)ORCID iD: 0000-0001-6095-2941
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. (orogen dynamik)
2007 (English)In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 144, no 1, 105-125 p.Article in journal (Refereed) Published
Abstract [en]

The Severnaya Zemlya Archipelago, located close to the continental edge of the Kara Shelf in the Russian high Arctic, represents, together with northern Tajmyr, the exposed Neoproterozoic and Palaeozoic part of the North Kara Terrane. This terrane has been interpreted as an independent microcontinent or part of a larger entity, such as Arctida or Baltica, prior to collision with Siberia in Late Carboniferous time. A major stratigraphic break, the Kan'on (canyon) River Unconformity, separates folded Late Cambrian from Early Ordovician successions in one area, October Revolution Island. New geochronological U–Th–Pb ion-microprobe data on volcanic and intrusive rocks from this island constrain the age of an important magmatic episode in the earliest Ordovician. A tuff, in association with Tremadocian fossils, overlying the Kan'on River Unconformity, has been dated to 489.5 ± 2.7 Ma. The youngest rocks beneath the unconformity are of the Peltura minor Zone, and the latter has been dated previously, in western Avalonia, to 490.1+1.7−0.9 Ma. Thus, little time is available for the tectonic episode recorded by the unconformity, and the similarities in radiometric dates may indicate problems with the correlation of faunal markers for the Cambrian–Ordovician boundary across palaeo-continents. The other extrusive and intrusive rocks which have been related to Early Ordovician rifting in the Severnaya Zemlya area yield ages from 489 Ma to 475 Ma. An undeformed granite, cutting folded Neoproterozoic successions on neighbouring Bol'shevik Island has been dated to 342 ± 3.6 Ma and 343.5 ± 4.1 Ma (Early Carboniferous), in accord with evidence elsewhere of Carboniferous strata unconformably overlying the folded older successions. This evidence conflicts with the common interpretation that the structure of the Severnaya Zemlya Archipelago originated during the collision of the North Kara Terrane with Siberia in Late Carboniferous time. An alternative interpretation is that Severnaya Zemlya was located in the Baltica foreland of the Caledonide Orogen and that the eastward-migrating deformation of the foreland basin reached the area of the archipelago in latest Devonian to Early Carboniferous time. This affinity of the North Kara Terrane to Baltica is further supported by 540–560 Ma xenocrysts in Ordovician intrusions on October Revolution Island, an age which is characteristic of the Timanide margin of Baltica.

Place, publisher, year, edition, pages
2007. Vol. 144, no 1, 105-125 p.
Keyword [en]
geochronology, tectonics, Severnaya Zemlya, Baltica, Siberia
National Category
URN: urn:nbn:se:uu:diva-93214DOI: 10.1017/S001675680600272XISI: 000244395200006OAI: oai:DiVA.org:uu-93214DiVA: diva2:166627
Available from: 2005-05-11 Created: 2005-05-11 Last updated: 2015-07-21
In thesis
1. Eurasian Arctic Tectonics: Geology of Severnaya Zemlya (North Kara Terrane) and Relationships to the Timanide Margin of Baltica
Open this publication in new window or tab >>Eurasian Arctic Tectonics: Geology of Severnaya Zemlya (North Kara Terrane) and Relationships to the Timanide Margin of Baltica
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The North Kara Terrane (NKT), with Severnaya Zemlya as its main outcrop area, constitutes the Palaeozoic and older rocks of the northern part of the Kara Shelf. Potential field data suggest a continuation into the eastern Barents Shelf. Several lines of evidence imply that the NKT was a part of Baltica at least during the latter part of the Neoproterozoic, and probably was influenced by Timanian orogeny.

The Timanide type area is characterised by metaturbidites from the pre-Timanian passive margin of the East European Craton (EEC). Regional amphibolite facies metamorphism, as exposed on Kanin Peninsula, was probably followed by near-isothermal decompression. It is inferred that these conditions were reached by depression beneath the accreted outboard terranes. Subsequently, the metaturbidites were thrust into their present position onto the EEC’s pericratonic unmetamorphosed shelf sediments. The thrusting was accompanied by rapid exhumation. About 560 Ma late-orogenic granites intrude the Timanian accreted terranes.

On Severnaya Zemlya, Neoproterozoic turbidites, containing ca. 560 Ma zircons, are overlain by shelf deposits, which dominate the Palaeozoic until the end of the Silurian. The succession is interrupted by the regional Kan’on (canyon) River Unconformity and probably by a late Neoproterozoic unconformity. New U-Th-Pb ion-microprobe isotope-ages on volcanics and faunal evidence imply that the Kan'on River Unconformity developed in a short time span around the Cambrian-Ordovician boundary. Other isotope-ages demonstrate that intense igneous activity, which has been inferred to be related to rifting within the NKT, extended into the Arenig and was contemporaneous with the development of Baltica’s northeastern passive margin. Zircon xenocrysts (ca. 540 - 580 Ma) in these igneous rocks indicate a Timanian component in the crust below the Severnaya Zemlya Archipelago. In the latest Silurian, Old Red Sandstone facies sedimentation began with the migration of an inferred Caledonian foreland basin into the area of Severnaya Zemlya. The Caledonian deformation front overrode the area in the latest Devonian or earliest Carboniferous.

The inferred late Caledonian deformation terminated, according to biostratigraphy and new isotope-ages from Bol'shevik Island granites, before the end of the Visean (ca. 345 Ma). Thus, the Uralian collision between the NKT and Siberia (ca. 300 Ma) apparently did not affect the Severnaya Zemlya Archipelago.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. viii + 93 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 68
Earth sciences, Arctic, Severnaya Zemlya, North Kara Terrane, Baltica, bedrock, geology, tectonics, Timanides, Caledonides, Geovetenskap
National Category
Earth and Related Environmental Sciences
urn:nbn:se:uu:diva-5851 (URN)91-554-6286-3 (ISBN)
Public defence
2005-06-03, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2005-05-11 Created: 2005-05-11Bibliographically approved

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Publisher's full texthttp://doi.org/10.1017/S001675680600272X

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