Abstract
The Fennoscandian shield, a part of the East European Craton, is distinguished by the exposed bedrock which is mainly composed of Precambrian metamorphic and igneous rocks. Large parts of the ground surface closely coincides with a late Precambrian denudation surface; the sub-Cambrian peneplain. Palaeozoic and younger sediments were deposited on the peneplain but these sediments have been removed from most areas that now form the mainland of Sweden and Finland and there are just a few remnants left. In the Baltic Sea, located in large-scale depressions on the boundary of in the Fennoscandian Shield/ in the East European Craton/, the Precambrian bedrock is still in large parts covered by Palaeozoic sediments. The Palaeozoic sedimentary rocks, as they are well bedded, may form a memory of the late Palaeozoic and younger tectonic events in the underlying basement rocks. Such data are used here to complement the structural observations made at sites located on the mainland, giving information on displacement along faults. Significant for the Baltic Sea are faults oriented in N-S that appear as segments, displaced relative to each other. Other structures are oriented in E-W, NE-SW and NW-SE. The SKB Forsmark site is located in a relatively flat coastal area
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Citation Formats
Beckholmen, Monica, and Tiren, Sven A.
Displacement along extensive deformation zones at the two SKB sites: Forsmark and Laxemar.
Sweden: N. p.,
2010.
Web.
Beckholmen, Monica, & Tiren, Sven A.
Displacement along extensive deformation zones at the two SKB sites: Forsmark and Laxemar.
Sweden.
Beckholmen, Monica, and Tiren, Sven A.
2010.
"Displacement along extensive deformation zones at the two SKB sites: Forsmark and Laxemar."
Sweden.
@misc{etde_1013175,
title = {Displacement along extensive deformation zones at the two SKB sites: Forsmark and Laxemar}
author = {Beckholmen, Monica, and Tiren, Sven A}
abstractNote = {The Fennoscandian shield, a part of the East European Craton, is distinguished by the exposed bedrock which is mainly composed of Precambrian metamorphic and igneous rocks. Large parts of the ground surface closely coincides with a late Precambrian denudation surface; the sub-Cambrian peneplain. Palaeozoic and younger sediments were deposited on the peneplain but these sediments have been removed from most areas that now form the mainland of Sweden and Finland and there are just a few remnants left. In the Baltic Sea, located in large-scale depressions on the boundary of in the Fennoscandian Shield/ in the East European Craton/, the Precambrian bedrock is still in large parts covered by Palaeozoic sediments. The Palaeozoic sedimentary rocks, as they are well bedded, may form a memory of the late Palaeozoic and younger tectonic events in the underlying basement rocks. Such data are used here to complement the structural observations made at sites located on the mainland, giving information on displacement along faults. Significant for the Baltic Sea are faults oriented in N-S that appear as segments, displaced relative to each other. Other structures are oriented in E-W, NE-SW and NW-SE. The SKB Forsmark site is located in a relatively flat coastal area within the sub-Cambrian peneplain. The sea area at the Forsmark site has a more accentuated relief than what is found on the mainland, for example, a furrow along the western side of the N-S oriented island Graesoe northeast of Forsmark (below 30m b.s.l. and locally more than 50m lower than Graesoe) and the deep between Aaland and Sweden (301m b.s.l.) about 100km east-southeast of Forsmark. In the Forsmark-site area two sets of structures interfere: a WNWESE trending set with relatively straight faults along the north coast of Uppland and a NNW-SSE to N-S trending set, slightly curved, along the (north)east coast of Uppland. The Forsmark site is located in an elevated WNW trending lath-shaped rock block outlined by WNW-ESE and NE-SW trending faults. In the Forsmark area, accumulated vertical, relative displacement on a structure during the late Precambrian (from 1600 to about 1000Ma), along steeply dipping faults, e.g. WNW-ESE trending faults, may have been on kilometre scale, while Phanerozoic accumulated relative displacement (about 540Ma to present) is of the scale of a few tens of metres or less. The Phanerozoic displacement is related to block-faulting and often combined with tilting of the blocks. Earthquakes are minor and relatively few in the surroundings of the Forsmark site. However, earthquakes are relatively frequent along the coast north of Gaevle (about 65km to the northwest). In the surroundings of Forsmark earthquakes occur preferentially along WNW-ESE and N-S trending faults. The Laxemar site is also located in a coastal area with low relief; on a regional scale, the ground surface is tilted eastwards. The relief in the sea area east of the Laxemar area is similar to that inside the Laxemar area, though on a regional scale the inclination of the sea bottom/sub-Cambrian peneplain increases slightly eastwards. Late Precambrian displacement (between 1 450 to 900Ma ago) with a vertical relative offset in the order of 500m is indicated for a N-S trending fault along the western boundary of the Laxemar area. The region displays a relatively complex rock block pattern. Rock blocks appear on different scales and the blocks have, in general, a low symmetry. Block faulting occurs on various scales. Relative vertical displacement between blocks in the region surrounding the Laxemar site, since the formation of the sub-Cambrian peneplain, is less than a few tens of metres. However, such displacement is not found in the Laxemar site. Post-glacial distortions are found along two faults in the sea area east of Laxemar: along a NNE trending fault east of Oeland and along a set of NWSE trending faults southeast of Gotland. Earthquakes are minor and few in south-eastern Sweden. They occur preferentially along the NNE trending strait between Oeland and the main land ( Kalmarsund) and along NW-SE trending structures north of Laxemar. Some earthquakes line up along N-S and E-W trending faults. Minor earthquakes are recorded for the regional E-W trending Mederhult zone, which forms the northern boundary of the Laxemar site and extends eastwards, far into the sea area. However, the Mederhult zone appears not to have been recognized in the marine geophysical survey covering the sea areas east of south-eastern Sweden despite that the structure has a topographical expression}
place = {Sweden}
year = {2010}
month = {Dec}
}
title = {Displacement along extensive deformation zones at the two SKB sites: Forsmark and Laxemar}
author = {Beckholmen, Monica, and Tiren, Sven A}
abstractNote = {The Fennoscandian shield, a part of the East European Craton, is distinguished by the exposed bedrock which is mainly composed of Precambrian metamorphic and igneous rocks. Large parts of the ground surface closely coincides with a late Precambrian denudation surface; the sub-Cambrian peneplain. Palaeozoic and younger sediments were deposited on the peneplain but these sediments have been removed from most areas that now form the mainland of Sweden and Finland and there are just a few remnants left. In the Baltic Sea, located in large-scale depressions on the boundary of in the Fennoscandian Shield/ in the East European Craton/, the Precambrian bedrock is still in large parts covered by Palaeozoic sediments. The Palaeozoic sedimentary rocks, as they are well bedded, may form a memory of the late Palaeozoic and younger tectonic events in the underlying basement rocks. Such data are used here to complement the structural observations made at sites located on the mainland, giving information on displacement along faults. Significant for the Baltic Sea are faults oriented in N-S that appear as segments, displaced relative to each other. Other structures are oriented in E-W, NE-SW and NW-SE. The SKB Forsmark site is located in a relatively flat coastal area within the sub-Cambrian peneplain. The sea area at the Forsmark site has a more accentuated relief than what is found on the mainland, for example, a furrow along the western side of the N-S oriented island Graesoe northeast of Forsmark (below 30m b.s.l. and locally more than 50m lower than Graesoe) and the deep between Aaland and Sweden (301m b.s.l.) about 100km east-southeast of Forsmark. In the Forsmark-site area two sets of structures interfere: a WNWESE trending set with relatively straight faults along the north coast of Uppland and a NNW-SSE to N-S trending set, slightly curved, along the (north)east coast of Uppland. The Forsmark site is located in an elevated WNW trending lath-shaped rock block outlined by WNW-ESE and NE-SW trending faults. In the Forsmark area, accumulated vertical, relative displacement on a structure during the late Precambrian (from 1600 to about 1000Ma), along steeply dipping faults, e.g. WNW-ESE trending faults, may have been on kilometre scale, while Phanerozoic accumulated relative displacement (about 540Ma to present) is of the scale of a few tens of metres or less. The Phanerozoic displacement is related to block-faulting and often combined with tilting of the blocks. Earthquakes are minor and relatively few in the surroundings of the Forsmark site. However, earthquakes are relatively frequent along the coast north of Gaevle (about 65km to the northwest). In the surroundings of Forsmark earthquakes occur preferentially along WNW-ESE and N-S trending faults. The Laxemar site is also located in a coastal area with low relief; on a regional scale, the ground surface is tilted eastwards. The relief in the sea area east of the Laxemar area is similar to that inside the Laxemar area, though on a regional scale the inclination of the sea bottom/sub-Cambrian peneplain increases slightly eastwards. Late Precambrian displacement (between 1 450 to 900Ma ago) with a vertical relative offset in the order of 500m is indicated for a N-S trending fault along the western boundary of the Laxemar area. The region displays a relatively complex rock block pattern. Rock blocks appear on different scales and the blocks have, in general, a low symmetry. Block faulting occurs on various scales. Relative vertical displacement between blocks in the region surrounding the Laxemar site, since the formation of the sub-Cambrian peneplain, is less than a few tens of metres. However, such displacement is not found in the Laxemar site. Post-glacial distortions are found along two faults in the sea area east of Laxemar: along a NNE trending fault east of Oeland and along a set of NWSE trending faults southeast of Gotland. Earthquakes are minor and few in south-eastern Sweden. They occur preferentially along the NNE trending strait between Oeland and the main land ( Kalmarsund) and along NW-SE trending structures north of Laxemar. Some earthquakes line up along N-S and E-W trending faults. Minor earthquakes are recorded for the regional E-W trending Mederhult zone, which forms the northern boundary of the Laxemar site and extends eastwards, far into the sea area. However, the Mederhult zone appears not to have been recognized in the marine geophysical survey covering the sea areas east of south-eastern Sweden despite that the structure has a topographical expression}
place = {Sweden}
year = {2010}
month = {Dec}
}