Home – Home – Jornals – Russian Geology and Geophysics 2011 number 12

There were two key stages in the history of Paleozoids that formed in the place of the Paleoasian ocean, one in the Cambrian-Ordovician and the other in the Permian-Triassic. Both time spans were characterized by a combination of similar geodynamic, magmatic, and geomagnetic events: closure and opening of oceanic basins, intense plume magmatism associated with Earth's core cooling, and absence of geomagnetic reversals (superchrons). Three superchrons about 490-460, 260-300, and 124-86 Ma correlate with major events of plume magmatism. Plume reconstructions have to be updated for the period 490-460 Ma, which corresponded to the third superchron and was marked by ocean opening. The previous superplume, about 800-740 Ma, requires further justification but fits the global periodicity with 240 Ma major cycles and smaller ones of 120 (or also 30) Ma.
In the Late Cambrian-Ordovician, large-scale accretion and collision events acted, in similar tectonic settings, upon the vast territory that currently extends from the Polar Urals to Lake Baikal (and was times larger in the past). As a result, Gondwanian microcontinents (Kokchetav, Altai-Mongolian, Tuva-Mongolian, etc.) and island arcs joined into the Kazakhstan-Tuva-Mongolian system. The formation of the Late Cambrian-Ordovician orogen in Central Asia was synchronous with the opening of the Ural, Ob-Zaisan, Turkestan, and Paleotethys oceans. The plume pulses (520-500 and 490-460 Ma) might have been responsible for the opening of new oceans, accelerated amalgamation of terranes, and synchronicity in geodynamic events from the Urals to Transbaikalia.