Reconstructing a continuous Holocene composite sedimentary record for the eastern Gotland Deep, Baltic Sea

It has been generally assumed that sediments in the deepest parts of the Gotland Basin have accumulated in a relatively calm depositional environment during the entire Holocene, thus representing a continuous sedimentary record. As part of the Baltic Sea System Study (BASYS) we have had access to several long cores from the Gotland Deep, which we have investigated in detail. The study, utilising sediment physical properties (e.g., magnetic susceptibility) and lithostratigraphic (core descriptions, photographs, stereo X-ray radiographs) data, has shown that even over very short horizontal distances the sedimentary records reflect considerable variations in sediment accumulation. Definable sedimentary units show marked variation in thickness, including clear hiatuses. These indicate that environmental conditions have been far more dynamic than has been previously assumed, and that the patchy nature of sediment deposition in the Baltic Sea is characteristic also to the Gotland Deep. This is true especially of the Litorina Sea, Post-Litorina Sea and Recent Baltic Sea stages of the Baltic Sea (~ past 7500–8000 cal years BP). Due to the fact that sediment stratigraphy can change a lot even over very short distances in this deep basin, correlation between different cores should be done with great care. To produce a stratigraphically continuous sequence for the Gotland Deep, we have spliced data together from several different cores.