Quaternary paleolake formation and cataclysmic flooding along the upper Yenisei River

Abstract

A suite of geomorphological and sedimentological features in the catchment of the upper Yenisei River in the Sayan mountains of southern Siberia testifies to the occurrence of cataclysmic floods that flowed down the river. Evidence of large-scale high-energy flood events includes: 1) gravel dunes, up to a few meters high and spaced 50 to 80 m apart, in the Kyzyl Basin 2) landforms such as hanging valleys and paleochannels and 3) flood sediments in a tributary valley. The origins of the Yenisei floods were likely diverse due to complex hydrological processes operating in the Sayan mountains. The possibilities include failures of multiple, variably impounded (ice, sedimentary, tectonic scarp, and lava flow dams) paleolakes in the two large intermontane basins of Darkhadyn Khotgor and Todza, and other minor basins, in the upper Yenisei River catchment. Dating techniques applied to the paleolakes in the Darkhadyn Khotgor and Todza basins revealed their formation during various periods in the middle–late Pleistocene and Holocene. Flooding from the Darkhadyn Khotgor appears to explain many of the inferred flood features, although contributions by flooding from other paleolake basins cannot be ruled out. Computer simulation of the flooding caused by a Darkhadyn Khotgor paleolake ice-dam failure indicates a probable peak discharge of ∼ 3.5 × 10 6 m 3 s − 1 , approximately one-fifth that of the floods that formed the Channeled Scabland in the U.S.A. Many of the outburst events probably occurred in the late Quaternary, but earlier floods could also have occurred.