Abstract:
The sediment composition and sedimentation conditions of Maastrichtian and Danian deposits in the vast territory of the Russian plate and adjacent regions of North Eurasia were studied. The succession of Late Cretaceous carbonaceous conditions of sedimentation in the Early Paleocene is noted in the major part of North Eurasia sedimentary basins. In some areas of the Lower Volga region and of the Northern Cis-Caspian basin, a radical change occurred in the sedimentation conditions at the Cretaceous-Paleogene boundary: Lower Paleocene siliceous formation replaced Maastrichtian carbonaceous formations. It is assumed that in this case the silica mass delivery into the basin was caused by tectonic rejuvenation of faults system at the border between the Russian platform and the Cis-Caspian basin under the large impact events. At the Maastrichtian-Danian boundary and above in the Danian, the increase of magnetic susceptibility of rocks is commonly noted for the major part at the expense of enrichment of rocks with iron in paramagnetic compounds (ferric hydrooxide and iron-containing clayey minerals) similar to metal-bearing sediments and to a lesser degree at the transport of terrigenous material addition in the period of large Early Paleocene regression. In the sediments, microspherules of metallic iron are noted that are most likely of cosmic meteoric dust.
