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Post-Timanian Palaeozoic Platform Successions |
VNIIOkeangeologia, 1, Angliysky pr., 190121, St Petersburg, Russia
Neoproterozoic and perhaps older metamorphic and igneous rocks in the Novaya Zemlya Archipelago are exposed in four main localities. On the South Island of Novaya Zemlya (the Southern Domain) largely metasedimentary, low greenschist facies, pelitic and flyschoidal formations, dated by acritarchs as late Riphean-Vendian occur; they are intruded by metagabbro-dolerites and lamprophyres. These rocks are overlain by Ordovician strata with sharp, angular unconformity and are therefore considered to be products of Timanian (Baikalian) tectonogenesis. On the southern part of the North Island (the Central Domain), metamorphic rocks of high greenschist to amphibolite facies are preserved which are partly migmatized and comprise metasedimentary and igneous rocks; their contact with Palaeozoic strata here is tectonic. Isotopic age determinations on metasediments and igneous rocks vary from 1550 to 598 Ma and are not yet conclusive. These relatively highly metamorphosed formations may be older than Neoproterozoic. A Neoproterozoic (late Riphean) age was determined for the Mitushev Kamen‘Granite Massif, which is located within the Main Novozemel’sky thrust zone. On the northern part of North Island, (the Northern Domain) Neoproterozoic strata (mainly turbidites) of low greenschist facies pass conformably up into Cambrian and younger strata.
A major NW-trending fault (the Baidaratsky fault zone) is believed to separate the Southern Domain from Central and Northern Domains. It is concluded that the southern area is a peripheral part of the Neoproterozoic Timanian (Baikalian) fold belt. Further to the NE across the Baidaratsky fault zone, lies a broad area of possibly older basement, including the Central and Northern Domains of Novaya Zemlya and possibly the Franz Josef Land Archipelago.
