High resolution seismic investigations of the south-western Baltic sea: A seismic pre-site survey for the IODP-Proposal 'Paleo-environmental evolution of the Baltic Sea Basin through the last glacial cycle'
Zusammenfassung der Projektergebnisse
This project is intimately linked to the IODP drilling proposal 672 by Andren et al. from 2004 on and the IODP Expedition 347 in autumn 2013. The proponents contributed significantly to the development of the proposal since 2006 and provided data, evidence and geologic/geophysical interpretation for site selection. The original purpose had been to work up the seismic data acquired during R/V Heincke Cruise He 244 to support the selection of drill sites, to characterize the depositional environment and to determine the basic stratigraphic framework. In the course of the project it became evident that the geologic complexity is higher than expected, and that further seismic data would be needed not only to come up with sound scientific publications, but also to finally receive drill site approval by the EPSP. While selection of study areas had focused on subsurface depressions, identified from old and low quality/resolution seismic data, the newer data reveal, that they do not represent classical fill structures, but rather chaotic or complex seismic facies is identified. While quiet conditions are required to provide well stratified units, originating from late glacial or interglacial times, in all selected locations likely glacial till or deformed bedrock is associated with the depression fill, and virtual fill structures, related to listric fault zones within the bedrock, may instead play a major role. During the preparation of a safety review package for EPSP, this evidence was summarized in 5 extended reports, which also led to an adjustment of site locations compared to the original proposal. The newer interpretation had then been mostly confirmed by the drilling during Expedition 347. While valuable evidence was gathered with a workload far beyond what had been funded by DFG, the material still awaits a thorough analysis to connect the geophysical data to the drilling results.
