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Weichselian ice dynamics in Jämtland, central Sweden: Lithostratigraphic study of the Köttsjön till deposits

Filbà I Serra, Laura LU (2025) In Dissertations in Geology at Lund University GEOR02 20251
Department of Geology
Abstract
This study provides a comprehensive sedimentological and geochemical analysis of the Late Quaternary Köttsjön sequence in central Sweden. Its aim is to identify the processes and transport mechanisms involved in till formation, and to investigate ice dynamics and sediment provenance. Ultimately, the research contributes to a better understanding of glacial dynamics and palaeoenvironmental evolution in central Scandinavia, particularly the complexity of Middle to Late Weichselian ice-sheet behaviour.
The stratigraphic succession consists of six units, including several till beds (the lowermost known as the “old clayey till” or “blue till”) interbedded with sorted sediments. These tills record at least two major glacial advances, which,... (More)
This study provides a comprehensive sedimentological and geochemical analysis of the Late Quaternary Köttsjön sequence in central Sweden. Its aim is to identify the processes and transport mechanisms involved in till formation, and to investigate ice dynamics and sediment provenance. Ultimately, the research contributes to a better understanding of glacial dynamics and palaeoenvironmental evolution in central Scandinavia, particularly the complexity of Middle to Late Weichselian ice-sheet behaviour.
The stratigraphic succession consists of six units, including several till beds (the lowermost known as the “old clayey till” or “blue till”) interbedded with sorted sediments. These tills record at least two major glacial advances, which, when correlated with the regional stratigraphy, likely occurred during MIS 4 and MIS 2. These advances are separated by an interstadial period (MIS 3) characterized by meltwater deposits and ice retreat.
Clast fabric and lithology analyses reveal shifts in ice flow direction from NW–SE to NE–SW, reflecting changes in the position of the ice divide. Geochemical data support these findings and suggest sediment reworking and varying weathering conditions (particularly within the lower till) highlighting the influence of environmental factors such as soil development. (Less)
Popular Abstract
Jämtland County, located in central Sweden, is a key area for studying the geological record left behind by glaciers that, over hundreds of thousands of years, have shaped Scandinavia through repeated advances and retreats triggered by major climate shifts. The village of Köttsjön, where the study site is located and positioned near the former centre of the Scandinavian Ice Sheet, preserves evidence of multiple glaciations, with layers of glacial deposits (tills) separated by meltwater sediments. Among these, a distinctive blue-grey, clay-rich layer, commonly referred to as the “old clayey till” or the “blue till”, raises several unresolved questions.
This study aims to understand how the glacial deposits found in Köttsjön, especially the... (More)
Jämtland County, located in central Sweden, is a key area for studying the geological record left behind by glaciers that, over hundreds of thousands of years, have shaped Scandinavia through repeated advances and retreats triggered by major climate shifts. The village of Köttsjön, where the study site is located and positioned near the former centre of the Scandinavian Ice Sheet, preserves evidence of multiple glaciations, with layers of glacial deposits (tills) separated by meltwater sediments. Among these, a distinctive blue-grey, clay-rich layer, commonly referred to as the “old clayey till” or the “blue till”, raises several unresolved questions.
This study aims to understand how the glacial deposits found in Köttsjön, especially the older, clay-rich "blue till", were formed, what processes and transport mechanisms were involved, which direction the ice moved in, and where the sediments originally came from. To achieve this, the exposed sediment layers were studied and sampled in the field, and later analysed in the lab using a combination of methods: clast fabric analysis (to determine ice flow direction), clast shape and lithology studies (to understand how the material was transported and where it came from), and geochemical analysis (to trace the chemical signature of the sediments and identify their origin).
The findings reveal at least two major glacier advances separated by a warmer period when the ice retreated. Early glaciers pushed sediments from the northwest, while later movements shifted to a northeast-southwest direction, indicating changes in the ice sheet’s internal structure. Chemical signals also highlight periods of stronger erosion and drier conditions during glacier advances, contrasting with wetter phases when meltwater flowed freely. Interestingly, the lower glacier deposits (those of the “blue till”) appear to have been recycled and altered over time, reflecting changing environmental conditions.
By linking the Köttsjön data with broader reconstructions of regional glacial histories, this study helps understand how ice sheets once shaped central Scandinavia as the results suggest that the ice didn’t always cover the land continuously, but instead advanced and retreated in complex patterns, with shifting flow directions over time. This reinforces the idea of a dynamic and changing ice sheet during the last glacial cycles. It also provides new insights into the enigmatic “blue till”, helping to clarify its origin and what it may reveal about past environmental conditions. (Less)
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author
Filbà I Serra, Laura LU
supervisor
organization
course
GEOR02 20251
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Sedimentological analysis, geochemical analysis, till formation, Weichselian, blue till, clast fabric, lithology analisis, ice flow direction
publication/series
Dissertations in Geology at Lund University
report number
705
language
English
id
9193120
date added to LUP
2025-06-05 09:08:32
date last changed
2025-06-05 09:08:32
@misc{9193120,
  abstract     = {{This study provides a comprehensive sedimentological and geochemical analysis of the Late Quaternary Köttsjön sequence in central Sweden. Its aim is to identify the processes and transport mechanisms involved in till formation, and to investigate ice dynamics and sediment provenance. Ultimately, the research contributes to a better understanding of glacial dynamics and palaeoenvironmental evolution in central Scandinavia, particularly the complexity of Middle to Late Weichselian ice-sheet behaviour. 
The stratigraphic succession consists of six units, including several till beds (the lowermost known as the “old clayey till” or “blue till”) interbedded with sorted sediments. These tills record at least two major glacial advances, which, when correlated with the regional stratigraphy, likely occurred during MIS 4 and MIS 2. These advances are separated by an interstadial period (MIS 3) characterized by meltwater deposits and ice retreat. 
Clast fabric and lithology analyses reveal shifts in ice flow direction from NW–SE to NE–SW, reflecting changes in the position of the ice divide. Geochemical data support these findings and suggest sediment reworking and varying weathering conditions (particularly within the lower till) highlighting the influence of environmental factors such as soil development.}},
  author       = {{Filbà I Serra, Laura}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Dissertations in Geology at Lund University}},
  title        = {{Weichselian ice dynamics in Jämtland, central Sweden: Lithostratigraphic study of the Köttsjön till deposits}},
  year         = {{2025}},
}