The Holocene sedimentary history of the Kangerlussuaq Fjord-valley fill, West Greenland

Abstract

West Greenland has been intensively studied to reconstruct and better understand past relative sea level changes and deglacial history. This study extends these efforts by linking sea level and deglacial history to the sedimentary infill successions of Kangerlussuaq Fjord and associated landward valleys. Based on published and new land- and sea-based geophysical data, radiocarbon dates and geological observations we have characterized the infill and reconstructed the sedimentation history during the Holocene.Based on a revised sea level curve and data presented in this paper we defined three depositional phases. Phase I (>7000 yr BP) is represented by dominant glaciomarine deposition associated with a tide-water glacier system. As the Greenland Ice Sheet (GIS) continued to retreat it became land based. During phase II (7000–1500 yr BP) two separate depocenters formed. Keglen delta depocenter arose from a temporary stabilization phase of the GIS and prograded rapidly over the glaciomarine deposits of Phase I. Further inland, proglacial lake formation and subsequent sedimentary infill associated with the ongoing GIS retreat is represents the second depocenter. The Watson River connected both depocenters by a flood plain which transferred sediment from the GIS to the Keglen delta. Ongoing sea level fall due to glacio-isostastic uplift combined with a gradually cooler and dryer climate resulted in terrace formation along the Watson River flood plain. Around 4000 yr BP, the GIS margin reached its most landward location and began to advance to its present location. The final phase (Phase III; <1500 yr BP) is represented by a stabilized GIS position and a relative sea level rise which led to aggrading conditions near the present-day delta plain of Watson River. Simultaneously, subaqueous channels were formed at the delta front by hyperpycnal flows associated with jökulhlaup events.