TY - JOUR

T1 - Wrench-fault structures superimposed by glaciotectonic complexes, interpreted from high-resolution reflectionseismic sections and boreholes along the western bank of Esrum Sø, north-east Sjælland, Denmark

AU - Winsløw, Line Bayer

AU - Schack Pedersen, Stig A.

AU - Boldreel, Lars Ole

AU - Nørmark, Egon

PY - 2020/8/7

Y1 - 2020/8/7

N2 - Wrench-fault structures below Danian limestone and Palaeogene marl, and an overlyingstructural framework of Quaternary glacial deposits in north-east Sjælland,Denmark, are interpreted from two vibro-seismic sections recorded to 600 msec TWTdepth. The main seismic section is 6.3 km long, N–S oriented, and intersected by a 0.7km long, E–W oriented satellite seismic section. In addition, boreholes in the vicinityof the seismic profile are used for the interpretation. The sections were acquired in2014 along the western shoreline of the lake Esrum Sø in the Gribskov area. In thelower part of the seismic section (the interval 100–300 msec TWT), parallel-beddedgeological layers occur along most of the profile apart from six locations, where sixwrench-fault structures displace the upper part of the Chalk Group and lower Palaeogenemarl. The northernmost of the six wrench-fault locations correlates to theeastern slope of the buried Esrum–Alnarp valley, which suggests that the valley isan inherited tectonic feature. The location of the wrench- fault structures supportsthe outline of faults related to the Sorgenfrei-Tornquist Zone on previous geologicalmaps, which had almost no seismic data from the area.Above the stratigraphic level presented by the Danian limestone and lower Palaeogenemarl, a composite glaciotectonic complex comprising two glaciodynamicsequences is recognized by e.g. thrust-fault structures and the lithostratigraphyof glacial successions recorded in the wells. In parts of the seismic sections, thelowermost level of the glaciotectonic complex inherited the wrench-tectonic faultstructures, most significantly seen in the northern segment. The advance of theScandinavian ice sheet caused the glaciotectonic structures displayed in the seismicsection. The two sequences represent events related to the Norwegian and theSwedish glacial advances. From the interpretation of the seismic section it is foundthat the glaciotectonic complex conceals the wrench-tectonic flower structures.

AB - Wrench-fault structures below Danian limestone and Palaeogene marl, and an overlyingstructural framework of Quaternary glacial deposits in north-east Sjælland,Denmark, are interpreted from two vibro-seismic sections recorded to 600 msec TWTdepth. The main seismic section is 6.3 km long, N–S oriented, and intersected by a 0.7km long, E–W oriented satellite seismic section. In addition, boreholes in the vicinityof the seismic profile are used for the interpretation. The sections were acquired in2014 along the western shoreline of the lake Esrum Sø in the Gribskov area. In thelower part of the seismic section (the interval 100–300 msec TWT), parallel-beddedgeological layers occur along most of the profile apart from six locations, where sixwrench-fault structures displace the upper part of the Chalk Group and lower Palaeogenemarl. The northernmost of the six wrench-fault locations correlates to theeastern slope of the buried Esrum–Alnarp valley, which suggests that the valley isan inherited tectonic feature. The location of the wrench- fault structures supportsthe outline of faults related to the Sorgenfrei-Tornquist Zone on previous geologicalmaps, which had almost no seismic data from the area.Above the stratigraphic level presented by the Danian limestone and lower Palaeogenemarl, a composite glaciotectonic complex comprising two glaciodynamicsequences is recognized by e.g. thrust-fault structures and the lithostratigraphyof glacial successions recorded in the wells. In parts of the seismic sections, thelowermost level of the glaciotectonic complex inherited the wrench-tectonic faultstructures, most significantly seen in the northern segment. The advance of theScandinavian ice sheet caused the glaciotectonic structures displayed in the seismicsection. The two sequences represent events related to the Norwegian and theSwedish glacial advances. From the interpretation of the seismic section it is foundthat the glaciotectonic complex conceals the wrench-tectonic flower structures.

KW - Faculty of Science

KW - Seismic architecture, glaciotectonics, glaciodynamics, Esrum–Alnarp valley, wrench- fault tectonics, flower structures.

U2 - 10.37570/bgsd-2020-68-08s1

DO - 10.37570/bgsd-2020-68-08s1

M3 - Journal article

VL - 68

SP - 171

EP - 193

JO - Bulletin of the Geological Society of Denmark

JF - Bulletin of the Geological Society of Denmark

SN - 0011-6297

ER -