|
Alexander Kalenich, State Company SEVMORGEO (Russian Federation)
Andrey Morozov, ROSNEDRA (Russian Federation)
Gennady Ivanov, State Company SEVMORGEO (Russian Federation)
|
|
The pre-Mesozoic evolution of the arctic Kara paleobasin was historically determined by its geographical location at the junction of three megastructures in northern Gondwanaland: the North American, Baltic and Siberian cratons. The peripheral parts of these megastructures were extended by plates (the Svalbard Basin, Timan-Pechora Plate and Kara Basin), with their most distant points corresponding to the modern archipelagos of Novaya Zemlya and Severnaya Zemlya, Taimyr and Pai-Hoi. Integrated analysis of geological data on the Novaya Zemlya orogenic province shows that its basement comprises three different tectonic segments (Northern, Central and Southern). Each segment has its own geological history and is characterized by different age of crust consolidation and time of amalgamation. Novaya Zemlya tectonic segments correspond to the above-named megastructures. The basement of the Central block consolidated in the Grenvillian and forms part of the Svalbard Plate. The basement of the Northern segment belongs to the Kara Plate that consolidated in the Karelian. The Southern segment of Novaya Zemlya, together with Vaygach Island, lies within the northeastern circumference of the Timan-Pechora Plate, which is generally thought to have consolidated during the Baikalian tectonogenesis. The tectonic ages of the basement units are based upon the available geological and geophysical data, arctic offshore and onshore field observations and isotope and paleontological dating of various parts of the sedimentary cover. In the South Kara paleobasin the pre-Mesozoic sedimentary cover is underlain by a basic layer, which may be interpreted as a relic of a residual oceanic basin. Such basins usually formed in areas where plates were partially connection with angular outlines. It is significant that the pre-Mesozoic geological units of the Kara paleobasin were generated in the same environment and can therefore be reliably correlated. The region's thick geological sections contain a continuous stratigraphic sequence of marine sediments from the Middle Riphean to the Permian. Paleofacies analysis of the depositional environments makes it possible to reconstruct in detail almost every stage of the Riphean - Paleozoic evolution of the Kara paleobasin - from an initial deep sedimentary structure to shallow marine with abruptly changing facies environments. Comparative analysis of the locations of the isochronous sedimentary units within the various parts of the Kara paleobasin reveals distinct tectonic-sedimentary differentiation within the Barents-Kara region. This differentiation is most explicit during the initial and concluding stages of the period under review. Recurring features of the geological section can be reliably correlated with global tectonic-sedimentary cycles. The differences seen in the prevalent regressive sequences in the upper third of the section reflect specific (provincial) features of the Kara paleobasin's tectonic history.
|
