Deglaciation history and subsequent lake dynamics in the Siljan region, south‐central Sweden, based on new LiDAR evidence and sediment records. Issue 15 (30th September 2022)

• Record Type: Journal Article
• Authors: Möller, Per; Björck, Svante; Dowling, Thomas P. F.; Hammarlund, Dan; Jakobsson, Martin; Ljung, Karl; Lund, Martin; Paradeisis‐Stathis, Savvas
• Is Part Of: Earth surface processes and landforms. Volume 47:Issue 15(2022)
• Page Start: 3515
• Page End: 3545
• Publication Date: 2022-09-30
• Subjects: Baltic Basin -- Dalarna -- digital terrain models -- drainage rerouting -- glacial geomorphology -- glaciofluvial deposits -- glacio‐isostatic rebound -- ice sheet recession -- ice‐dammed lake -- lake bathymetry -- lake isolation -- LiDAR -- ribbed moraine -- shoreline displacement -- streamlined terrain; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.5471
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: The Siljan region hosts Europe's largest impact structure. The high‐relief landscape, with a central granite dome bordered by lake basins, contains an array of glacial and shore‐level landforms. We investigated its deglaciation history by mapping and analysing landforms on high resolution LiDAR (light detection and ranging)‐based digital surface models coupled with well‐dated sediment successions from peat and lake sediment cores. The granite dome and bordering areas are characterized by streamlined terrain and ribbed moraine with a streamlined overprint. These suggest an ice‐flow direction from north‐northwest (NNW) with wet‐based thermal conditions prior to deglaciation. During its retreat, the ice sheet was split into thinner plateau ice and thicker basin ice. Sets of low‐gradient glaciofluvial erosion channels suggest intense ice‐lateral meltwater drainage across gradually ice‐freed slopes, while 'down‐the‐slope' erosion channels and eskers show meltwater drainage from stagnated plateau ice. Thick basin ice receded with a subaqueous margin across the deep Siljan–Orsasjön Basin c . 10, 700–10, 500 cal. bp . During ice recession the ingression of the Baltic Ancylus Lake led to diachronous formation of highest shoreline marks, from ~207 m in the south to ~220 m above sea level (a.s.l.) in the north. Differential uplift resulted in shallowing of the water body, which led to the isolation of the Siljan–Orsasjön Basin from the Baltic Basin at c . 9800 cal. bp . The post‐isolation water body – the 'Ancient Lake Siljan' – was drained through the ancient Åkerö Channel with a water level at 168–169 m a.s.l. during c . 1000 years. A later rerouting of the outlet to the present course was initiated at c . 8800 cal. bp, which led to a lake‐level lowering of 6–7 m to today's level of Lake Siljan (~162 m a.s.l.). This study shows the strength of an integrated methodological approach for deciphering the evolution of a complex landscape, combining highly resolved geomorphological analysis with well‐dated sediment successions. Abstract : Glacial geomorphology and postglacial landforms, derived from LiDAR‐based digital terrain models, together with radiocarbon‐dated sediment sequences, form the basis for landscape reconstruction spanning c . 2000 years (10, 500–8500 cal. bp ). After formation of streamlined terrain and ribbed moraine tracts followed intense glaciofluvial activity at deglaciation. Subaqueous ice retreat was across a series of deep basins, simultaneously with ingression of the Baltic Basin‐based Ancylus Lake. Isostatic uplift led to isolation of the Siljan Basin from the Baltic and subsequent rerouting of its outflow.