Unit 1 comprises the subsurface lacustrine and fluvio-deltaic sediments found in the basal parts of lake-floor cores and pits,and is subdivided into three subunits (1aec) based on differences in dominant structure, bedding, colour and grain size. The
basal Unit 1a consist of compact and massive beds of silt, clay (up to 80e95% silt and clay) and sand with occasional discontinuous beds of sand, granules and pebbles.