General geology of southern Kattegat, the Hesselø windfarm area. Desk Study. Report for Energinet Eltransmission A/S

Research output: Book/ReportReport (publicly available)

Abstract

Energinet A/S has requested that GEUS undertakes a geological desk study of the Hesselø Offshore Wind Farm (OWF) region. The study has resulted in a general geological description and establishment of a geological model. The study is based on existing data and is to be used as a background for future interpretations of new seismic data, geotechnical investigations and an archaeological screening.

In this study we have used a combination of published work, archive seismic data and sediment core data to assess the general geological development of the southern Kattegat area, including the planned Hesselø OWF and the cable corridor. A geological description is provided, and a geological model has been developed. As a result of the geological desk study it has been possible to establish a relative late glacial and Holocene sea-level curve for the area and to describe the palaeo development relevant for an archaeological screening.

The general geological description includes the complete geological succession from the general pre-Quaternary framework, the pre-Quaternary surface, glacial deposits, the deglaciation and late glacial and Holocene deposits. The geological model of the southern Kattegat is based on sequence stratigraphical studies by Jensen et al. (2002) customized to the Hesselø OWF and cable corridor case. On the basis of the presented geological model the Integrated Ocean Drilling Program (IODP) Expedition 347 in September 2013 carried out a more than 200 m deep drilling at site M0060. The obtained sediment succession was divided into seven different lithostratigraphical units and description of lithology and downhole core logging were performed including physical parameters.

A parallel scientific multichannel survey was carried out the same year and a detailed correlation has been carried out between the seismic data and core M0060. In the southernmost part of the Hesselø OWF area and the cable corridor, detailed studies of late glacial and early Holocene sea-level changes as well as the development of a Holocene barrier spit/estuary complex formed the basis for the evaluation of the geological model as well as input for construction of palaeo stratigraphical maps.

The maps reveal late glacial and early Holocene archaeological interesting coastal complexes in the time period for the Ahrensburg and Maglemose cultures. while the area was transgressed by the sea during younger cultures. In relation to geotechnical challenges a number of focal points has been raised such as neotectonics, recent earthquakes, gas in sediments, glaciotectonic deformations, great thickness of weakly consolidated glaciomarine clay, Holocene sand and clay with high organic contents.
Original languageEnglish
Place of PublicationCopenhagen
PublisherGEUS
Number of pages149
Volume2020
DOIs
Publication statusPublished - 19 May 2022

Publication series

NameDanmarks og Grønlands Geologiske Undersøgelse Rapport
PublisherGEUS
No.53
Volume2020

Keywords

  • Denmark

Programme Area

  • Programme Area 5: Nature and Climate

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