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Dan Hammarlund

Dan Hammarlund

Professor

Dan Hammarlund

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

Författare

  • Per Möller
  • Svante Björck
  • T.P.F. Dowling
  • Dan Hammarlund
  • Martin Jakobsson
  • Karl Ljung
  • Martin Lund
  • Savvas Paradeisis-Stathis

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.

Avdelning/ar

  • Kvartärgeologi
  • BECC: Biodiversity and Ecosystem services in a Changing Climate
  • MERGE: ModElling the Regional and Global Earth system
  • Miljövetenskap

Publiceringsår

2022-09-30

Språk

Engelska

Publikation/Tidskrift/Serie

Earth Surface Processes and Landforms

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