An updated Weichselian chronostratigraphic framework of the Kongsfjorden Trough Mouth Fan and its implications for the glacial history of Svalbard

Abstract

The Arctic is a climate-sensitive area, responding rapidly to present changes, but for the past changes, the recordis still incomplete. Forinstance, theWeichselian glacial historyof the Svalbard–Barents Sea Ice Sheet (SBIS) haslargely been reconstructed based on studies of the fragmentary Spitsbergen terrestrial and shelf records. However, the sediments removed from the land and shelf areas during peak glacials were deposited on trough mouth fans located along the continental slope. By studying the stratigraphy and processes of the trough mouth fans, comprising a more complete sediment archive, our new data have allowed gaps in theWeichselian glacial historyof the SBIS to be refined and filled. Here we present new lithological and geochronological data from theKongsfjordenTroughMouthFan, closelylinked to the advance and decay of the SBIS. High-resolution TOPAS seismic profiles reveal three distinct packages of glacigenic debris flows (GDFs) within its upper stratigraphy, each interpreted to represent an advance of the SBIS to the shelf edge.A radiocarbon dated, 12.6-m-long core from the southern flankof theKongsfjordenTroughMouthFan penetrates trough sediments directlylinked to the youngestGDF package and terminatesin the secondGDF, allowing us to study thelast twoKongsfjordenice-stream advancesin greater detail than was previously possible.The agemodel of core GS10-164-09PC, based on combining ¹⁴C-, ¹⁸O-stable isotope and magnetic susceptibility data, spans the last ~54 ka. An EarlyWeichselian glacial advance is tentatively dated to have ended at ~90 ka. A second peak glaciation is estimated at ~70 ka, followed by a deglaciation from ~54 ka. An ice rafted debris-rich unit (U7) dated between 38 and 34 ka, followed by a plumite (U6), indicates an advance of unknown extent. The Last Glacial Maximum advance is dated to before 24 kaBP, followed by a rapid deglaciation at~15 ka.The presence of coarser-grained sorted sediments at the present seafloor is attributed to the influence of theWest-Spitsbergen Current, acting on water depths of at least 846 m, and is thought to have worked in the vicinity of the coring site since ~14 ka BP.