Rhythmites

A rhythmite consists of layers of sediment or sedimentary rock which are deposited annually in glacial lakes, consisting of a light layer and a dark layer deposited at different seasons. It is a well stratified clastic sedimentary rock with blades and thin layers, usually of fine to medium granulation (medium to fine sand) alternating with fine-grained layers (silt / clay) that are rhythmically repeated indicating seasonal cycles and / or periodic variations on the transport energy related to the sediment input.