Syneruptive and intereruptive lithofacies in lacustrine environments: The Cretaceous Beolkeum Member, Wido Island, Korea

Resedimented syneruptive lithofacies were primarily controlled by volcaniclastic sediment supply after eruptions. When volcaniclastic sediments were continuously supplied into the lake by debris flows, a volcaniclastic fan can be formed (SLA-1), resulting in a coarsening-upward trend and progradational geometry. In case of relatively small amounts of volcaniclastic sediment supply, turbidity currents would be a main depositional process, depositing a series of normally graded tuff on the primary syneruptive lithofacies (SLA-2), showing a fining-upward trend. In SLA-3 and SLA-4, there are only a few cm thick, normally graded tuff, reflecting minor volcaniclastic sediment supply. However, overlying normally graded sandstones in SLA-3, showing a coarsening-upward trend, and a thick normally graded sandstone in SLA-4 suggest favorable conditions for the generation of the sediment gravity flows, probably due to an increase in volcaniclastic sediment supply after eruptions.