Abstract:
The Baltic Sea Basin (BSB) is one of the world's largest intra-continental basins. BSB has served as depositional sink throughout its geological history and accumulated sediments comprise a unique high-resolution paleoenvironmental archive. The IODP Proposal 672-Full 'Paleoenvironmental evolution of the Baltic Sea Basin through the last glacial cycle' mainly aims in investigating the climatic development during the past interglacial-glacial cycle, with emphasis on the last interglacial, the Eemian, and its transition into the Weichselian. In total 11 primary sites in 5 areas are postulated. A seismic pre-site survey was carried out during Heincke Cruise He244 in February 2006. Here we present results of this survey from the so called 'Anholt Loch'. The study area 'Anholt Loch' is situated in the southern Kattegat, south-easterly of the Danish island Anholt. The main aim of our work is to analyze whether Anholt Loch contains sediments of the complete last glacial cycle. The 'Anholt Loch' is a NW-SE trending valley, which is probably formed by sub-glacial melt-water erosion during repeated glaciations in the early and middle Quaternary. The valley is incised in tilted reflectors, which show a sharp increase in seismic velocity compared to the overlying sediments. The tilted reflectors are interpreted as pre-quaternary sediments. A boring on the island of Anholt shows that the pre-quaternary sediments are Jurassic in age. The erosional valley is filled with a more than 250 m thick sedimentary succession, in which five different facies could be identified. These were interpreted as quaternary sediments, which were deposited during Holocene to Saalian times. The lowermost quaternary facies was predominantly deposited under glacial conditions, probably Saalian till but also Eemian sediments, which were altered during the Weichsel-Glacial. The overlying facies shows chaotic reflection pattern as well as reflectors with high amplitudes and is interpreted as glacial Weichselian till. The stratification of the overlying two younger facies indicates a deposition under glaciomarine condition during the Weichsel-Glacial and in late Weichselian times. The youngest facies was deposited in the Holocene. The seismic data and the occurrence of Eemian sediments in a boring on the island of Anholt strongly suggest that sediments of the complete last glacial cycle exist in Anholt Loch. Based on a joint interpretation of all available data, IODP drilling in Anholt Loch would most likely result in the recovery of holocene marine clay, varved late weichselian clay, till of the Weichsel-glacial, eemian clay and saalian glacial sediments.