Late Quaternary ice flow in a West Greenland fjord and cross-shelf trough system: submarine landforms from Rink Isbrae to Uummannaq shelf and slope

• Main Authors: Julian A. Dowdeswell, K.A. Hogan, Colm O Cofaigh, E.M.G. Fugelli, Jeffrey Evans, R. Noormets
• Format: Other Non-Article Part of Journal/Newspaper
• Language: unknown
• Published: 2014
• Subjects: Earth Sciences not elsewhere classified; Arctic; Ice flow; Ice stream; Late Quaternary; Submarine landforms; Trough-mouth fan; West Greenland; Greenland; Moraine Ridge; South Ice; Uummannaq Fjord; Ice Sheet; Iceberg*; Rink Isbrae; Uummannaq
• Online Access: https://figshare.com/articles/journal_contribution/Late_Quaternary_ice_flow_in_a_West_Greenland_fjord_and_cross-shelf_trough_system_submarine_landforms_from_Rink_Isbrae_to_Uummannaq_shelf_and_slope/9482345

Sea-floor landforms and acoustic-stratigraphic records allow interpretation of the past form and flow of a westward-draining ice stream of the Greenland Ice Sheet, Rink Isbrae. The Late Pliocene-Pleistocene glacial package is several hundred metres thick and down-laps onto an upper Miocene horizon. Several acoustic facies are mapped from sub-bottom profiler records of the 400km-long Uummannaq fjord-shelf-slope system. An acoustically stratified facies covers much of the fjord and trough floor, interpreted as glacimarine sediment from rain-out of fine-grained debris in turbid meltwater. Beneath this facies is a semi-transparent deformation-till unit, which includes buried streamlined landforms. Landform distribution in the Uummannaq system is used to reconstruct past ice extent and flow directions. The presence of streamlined landforms (mega-scale glacial lineations, drumlins, crag-and-tails) shows that an ice stream advanced through the fjord system to fill Uummannaq Trough, reaching the shelf edge at the Last Glacial Maximum. Beyond the trough there is a major fan built mainly of glacigenic debris flows. Turbidity-current channels were not observed on Uummannaq Fan, contrasting with well-developed channels on Disko Fan, 300km to the south. Ice retreat had begun by 14.8cal.ka ago. Grounding-zone wedges (GZW) in Uummannaq Trough imply that retreat was episodic, punctuated by several still-stands. Ice retreat between GZWs may have been relatively rapid. There is little sedimentary evidence for still-stands in the inner fjords, except for a major moraine ridge marking a Little Ice Age maximum position. On the shallow banks either side of Uummannaq Trough, iceberg ploughing has reworked any morphological evidence of earlier ice-sheet activity. © 2013 The Authors.