Time-transgressive deposits of repeated depositional sequences within interlobate glaciofluvial (esker) sediments in Köyliö, SW Finland

摘要: ABSTRACT Evidence of conspicuous repeated seasonal to annual deposition glaciofluvial and glaciolacustrine sequences within a structurally complex interlobate esker segment in SW Finland is presented. The time-transgressive, overlapping depositional consist deposits from two successive melt seasons, including three vertically stacked lithofacies associations: (1) massive stratified coarse gravels = summer deposits; (2) trough ripple cross-stratified fine-grained deposits = autumn winter (3) sandy beds = spring deposits. environment each association involves transition subglacial or submarginal tunnel subaqueous re-entrant environment, which then passes proglacial environment. study also presents evidence headward extension deposits, related the rapid shifting expansion point during increasing spring discharge, occupied old exit: this mode has not been reported previously studies. good preservation rhythmic associations suggested as resulting conditions associated with rapidly decaying icestreams. Therefore, model may provide key recognizing time-transgressive eskers that form an important geomorphological sedimentological record meltwater activity last deglaciation Fennoscandian Laurentide ice sheets. identification palaeo-icestream behaviour essential step forward for more accurate models sheet palaeoclimatic reconstructions.