Abstract
The Quaternary geology at the Forsmark site has been characterized using both a map of Quaternary deposits and a regolith depth model (RDM) that show the stratigraphy and thickness of different deposits. Regolith refers to all the unconsolidated deposits overlying the bedrock. The surface geology and regolith depth are important parameters for hydrogeological and geochemical modelling and for the overall understanding of the area. The safety assessment analysis should focus on processes involved during a period of 120,000 years, which includes a full glacial cycle; however, the investigations within the site description model do not cover the temporal change of the regolith, a limitation that does not fulfil the requirements for the safety assessment. To this end, this study constructs a model that can predict the surface geology, stratigraphy, and thickness of different strata at any time during a glacial cycle and applies this model to the Forsmark site. The Weichselian ice sheet covered the study area until around 9500 BC. The deglaciation revealed a marine landscape with bedrock, till and glacial clay. For the safety assessment, the most important unconsolidated strata are clay or silt: these small grains can bind nuclear elements more easily than coarser sediment particles. Thick
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Citation Formats
Brydsten, Lars, and Stroemgren, Maarten.
A coupled regolith-lake development model applied to the Forsmark site.
Sweden: N. p.,
2010.
Web.
Brydsten, Lars, & Stroemgren, Maarten.
A coupled regolith-lake development model applied to the Forsmark site.
Sweden.
Brydsten, Lars, and Stroemgren, Maarten.
2010.
"A coupled regolith-lake development model applied to the Forsmark site."
Sweden.
@misc{etde_1004319,
title = {A coupled regolith-lake development model applied to the Forsmark site}
author = {Brydsten, Lars, and Stroemgren, Maarten}
abstractNote = {The Quaternary geology at the Forsmark site has been characterized using both a map of Quaternary deposits and a regolith depth model (RDM) that show the stratigraphy and thickness of different deposits. Regolith refers to all the unconsolidated deposits overlying the bedrock. The surface geology and regolith depth are important parameters for hydrogeological and geochemical modelling and for the overall understanding of the area. The safety assessment analysis should focus on processes involved during a period of 120,000 years, which includes a full glacial cycle; however, the investigations within the site description model do not cover the temporal change of the regolith, a limitation that does not fulfil the requirements for the safety assessment. To this end, this study constructs a model that can predict the surface geology, stratigraphy, and thickness of different strata at any time during a glacial cycle and applies this model to the Forsmark site. The Weichselian ice sheet covered the study area until around 9500 BC. The deglaciation revealed a marine landscape with bedrock, till and glacial clay. For the safety assessment, the most important unconsolidated strata are clay or silt: these small grains can bind nuclear elements more easily than coarser sediment particles. Thick layers of clay can be found where post-glacial clay settled on top of glacial clay, especially where the middle-aged erosion of postglacial clay is missing and where there is an uninterrupted sequence of accumulation of finegrained particles. Such areas could be found in deep marine basins that later become lakes when raised into a supra-marine position. The coupled regolith-lake development model (RLDM) predicts the course of events described above during an interglacial, especially the dynamics of the clay and silt particles. The RLDM is divided into two modules: a marine module that predicts the sediment dynamics caused by wind waves and a lake module that predicts the lake infill processes. The major part of the study area was covered by postglacial clay shortly after the area was deglaciated. As the water got shallower following isostatic rebound, more postglacial clay resuspended and exposed the glacial sediments beneath. The minimum areal extension of the postglacial clay occurred about 2000 BC and was localized to a deep area west of the island Graesoe. Next, the area of postglacial clay increased again to reach a local maximum around 2500 AD, then successively decreased until the sea left the study area (about 11,500 AD), exposing the greater part of the postglacial clay found in the lakes. Most of the lakes are shallow and will infill completely in 2,000 to 6,000 years. Exceptions are the deep lakes situated along today's Graesoeraennan that will exist for about 25,000 years. The last lake will be totally infilled around 35,000 AD. Permafrost conditions will appear in the Forsmark area at around 9400 AD. At that time, 30 of the 42 modelled lakes are already completely infilled and sedimentation processes will not be affected by the changed conditions.}
place = {Sweden}
year = {2010}
month = {Nov}
}
title = {A coupled regolith-lake development model applied to the Forsmark site}
author = {Brydsten, Lars, and Stroemgren, Maarten}
abstractNote = {The Quaternary geology at the Forsmark site has been characterized using both a map of Quaternary deposits and a regolith depth model (RDM) that show the stratigraphy and thickness of different deposits. Regolith refers to all the unconsolidated deposits overlying the bedrock. The surface geology and regolith depth are important parameters for hydrogeological and geochemical modelling and for the overall understanding of the area. The safety assessment analysis should focus on processes involved during a period of 120,000 years, which includes a full glacial cycle; however, the investigations within the site description model do not cover the temporal change of the regolith, a limitation that does not fulfil the requirements for the safety assessment. To this end, this study constructs a model that can predict the surface geology, stratigraphy, and thickness of different strata at any time during a glacial cycle and applies this model to the Forsmark site. The Weichselian ice sheet covered the study area until around 9500 BC. The deglaciation revealed a marine landscape with bedrock, till and glacial clay. For the safety assessment, the most important unconsolidated strata are clay or silt: these small grains can bind nuclear elements more easily than coarser sediment particles. Thick layers of clay can be found where post-glacial clay settled on top of glacial clay, especially where the middle-aged erosion of postglacial clay is missing and where there is an uninterrupted sequence of accumulation of finegrained particles. Such areas could be found in deep marine basins that later become lakes when raised into a supra-marine position. The coupled regolith-lake development model (RLDM) predicts the course of events described above during an interglacial, especially the dynamics of the clay and silt particles. The RLDM is divided into two modules: a marine module that predicts the sediment dynamics caused by wind waves and a lake module that predicts the lake infill processes. The major part of the study area was covered by postglacial clay shortly after the area was deglaciated. As the water got shallower following isostatic rebound, more postglacial clay resuspended and exposed the glacial sediments beneath. The minimum areal extension of the postglacial clay occurred about 2000 BC and was localized to a deep area west of the island Graesoe. Next, the area of postglacial clay increased again to reach a local maximum around 2500 AD, then successively decreased until the sea left the study area (about 11,500 AD), exposing the greater part of the postglacial clay found in the lakes. Most of the lakes are shallow and will infill completely in 2,000 to 6,000 years. Exceptions are the deep lakes situated along today's Graesoeraennan that will exist for about 25,000 years. The last lake will be totally infilled around 35,000 AD. Permafrost conditions will appear in the Forsmark area at around 9400 AD. At that time, 30 of the 42 modelled lakes are already completely infilled and sedimentation processes will not be affected by the changed conditions.}
place = {Sweden}
year = {2010}
month = {Nov}
}