Prof. Dmitry V. Metelkin fr om the Chair of General and Regional Geology at NSU and the Trofimuk Institute of Petroleum Geology and Geophysics SB RAS tells us wh ere Siberia was located during different historic periods and if we should expect a warm climate.
Paleomagnetic data have allowed researchers to reconstruct tectonics of the Siberian continental plate for almost 1.0 Ga.
Siberian Craton occupies the central place in the structure of Northern Asia and is located between the largest rivers of Eastern Siberia - the Yenisey and Lena; it includes Irkutskaya region, a major part of Krasnoyarsky Kray and the Sakha Republic, some parts of Amurskaya and Chitinskaya regions and the Republic of Buryatia.
Geologically, our Eurasian continent is very heterogeneous. It includes ancient blocks and some relatively young areas. Siberian Craton is one of the biggest ancient massifs within Eurasia. About 1.0 Ga, this massif made a certain large peninsula being a part of Rodinia and was situated in the tropical part of the northern hemisphere. The tectonic evolution of Siberia is correlated with gathering and disintegrating of two supercontinents: Rodinia and Pangea. Rodinia having disintegrated, Siberia separated into an independent continent located primarily in the tropical and subtropical areas almost till the appearance of Pangea about 250 Ma. Although paleomagnetic data allow us to reconstruct only the changes in the latitude and the angle of rotation, the calculated drift velocity of Siberian Craton, similar to any other tectonic plate, as a rule does not exceed 10 cm/year, and the amplitude of rotation is less than 1 degree per million years. The direction of the drift changed quite frequently depending on the global changes in the planet dynamics, such as development of oceans. The terrain underwent a northern drift from the near-equatorial position to the modern subarctic one, which began in the Cambrian period, about 500 Ma. According to paleomagnetic data, during that time the plate gradually rotated clockwise at an angle of about 180掳, and up to the beginning of the Triassic the northern margin of Siberia faced west.
As for the Siberian climate during that equatorial period, it is really difficult to define it. The atmosphere, currents in the ocean and many other factors influencing the climate changed along with the development of the planet, and the climatic zones at those ancient times were absolutely different.
In order to get to the bottom of the environment conditions in the reconstructed area, we analyze fossils and the rocks which formed during the period in question. For example, a cold climate is usually characterized by a particular set of deposits connected with moving and melting ice-fields. If we find such deposits in the crust, it proves glacial action and testifies to the cold climate in the area, even though the block used to be located at the Equator. During the Cryogenian period (850-630 Ma), which was one of global glacial eras in the geological history, Siberia along with other ancient continent massifs was located at tropical latitudes. At the same time, all the massifs demonstrate substantial glacial deposits, which gave rise to the hypothesis of the Snowball Earth.
Speaking about the territory of present-day Novosibirsk, Dmitry Metelkin says that the continental plate below the city appeared relatively recently, about 480 Ma, as a result of the ocean basin development on the margins of the Siberian paleocontinent. Due to the global drift of the continents, the plate is going to move southwards, and in 200-250 million years it will return back to the subtropical zone of the northern hemisphere. Let鈥檚 just hope that the climate will not become icy and the living conditions will be favorable enough.
