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River discharge is the main source of terrigenous sediments in many coastal areas adjacent to estuaries and deltas of large rivers. Spreading and mixing dynamics of river plumes governs transport of suspended sediments and their deposition at sea bottom at these areas. Generally river plumes have very large synoptic and seasonal variability, which cannot be reconstructed from structure of bottom sediments due to their small accumulation velocity. However, bottom sediments can be indicative of variability of river plumes on inter-annual and decadal time scales. In this study we focus on the large Ob and Yenisei buoyant plumes formed in the central part of the Kara Sea. These plumes interact and mix in the area adjacent to the closely located Ob and Yenisei gulfs. Suspended sediments carried by these river plumes have significantly different geochemical characteristics that can be used to detect Ob or Yenisei origin of bottom sediments. Using new geochemical methods we revealed dependence between spreading patterns of these plumes and spatial distribution and vertical structure of bottom sediments in the study area. This relation is confirmed by a good agreement between local wind and discharge conditions reconstructed for 1948-2001 and vertical structure of bottom sediments.