Deglaciation history and subsequent lake dynamics in the Siljan region, south-central Sweden, based on new LiDAR evidence and sediment records

Summary, in Swedish

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-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 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 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.

• Författare: Per Möller; Svante Björck; T.P.F. Dowling; Dan Hammarlund; Martin Jakobsson; Karl Ljung; Martin Lund; Savvas Paradeisis-Stathis
• Avdelning/ar: Kvartärgeologi; BECC: Biodiversity and Ecosystem services in a Changing Climate; Miljövetenskap
• Publiceringsår: 2022-09-30
• Språk: Engelska
• Sidor: 3515-3545
• Publikation/Tidskrift/Serie: Earth Surface Processes and Landforms
• Volym: 47
• Länkar: http://dx.doi.org/10.1002/esp.5471
• Dokumenttyp: Artikel i tidskrift
• Förlag: John Wiley & Sons Inc.
• Ämne: Geology
• Nyckelord: Dalarna; ice sheet recession; glacial geomorphology; streamlined terrain; ribbed moraine; glaciofluvial deposits; lake isolation; drainage re-routing; lake bathymetry; ice-dammed lake; shoreline displacement; Baltic Basin; glacio-isostatic rebound; LiDAR; digital terrain models
• Status: Published
• ISBN/ISSN/Övrigt: ISSN: 0197-9337