Cretaceous Terrigenous Rocks between the Pilda and Amur Rivers (Lower Amur Region): Material Composition, Source Areas, and Sedimentation Conditions

The results of the study and paleogeodynamic interpretation of the material composition of Cretaceous terrigenous deposits that developed in the basins of the Pilda, Limuri, and Amur rivers (Lower Amur region) are considered. Initial data were obtained that made it possible to assess the composition of the rock-forming components, as well as the content and distribution of rock-forming, small (rare), and rare-earth elements in sandy and clay-siltstone rocks, and on this basis to establish the source areas and geodynamic conditions of sediment formation. It was found that, according to their mineralogical and geochemical characteristics, sandstones are attributed to graywackes, which have low degrees of maturity and lithodynamic reworking of detrital material. Clay–siltstone rocks correspond to clay shales. The sediments were formed due to springs composed mainly of felsic igneous, metamorphic, and ancient sedimentary rocks. In addition, at the time of accumulation of Cenomanian–Turonian deposits, explosive volcanic material of a much more mafic composition also entered the basin. Paleogeodynamic interpretation of the results suggests the accumulation of Cretaceous terrigenous deposits of the Lower Amur region in the basin is associated with a regime of transform sliding of lithospheric plates.