Geoscience Reference
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Fig. 5.9 NE-SW echosounder cross-sectional profile 0. Dark lines mark the stratigraphic base
boundaries A and B zones. Coring locations and core depths are schematically displayed
If one compares the seismoacoustic profile in Fig. 5.9 with the lithostratigraphic
correlation scheme of the cores displayed in Fig. 5.8 as well as within the seismic
signal in the MSCL data, the bases of A and B zones can be recognized easily by
the contrast in their sedimento-physical properties. The boundaries within each of
the seismic profiles (bold red lines in Fig. 5.5 ) have been digitized and marked by
thin dark lines as it is shown in Fig. 5.9 . Digitized and geo-referenced stratigraphic
boundaries were stored in a database for mapping the subsurfaces. However, the
seismic survey of the POSEIDON expedition POS 323-1 did not sufficiently cover
the area of the Stolpe Foredelta. As this basin structure plays a key role in under-
standing the depositional system of the central Baltic, additional lithostratigraphic
cross-sections (yellow lines in Fig. 5.5 ) have been incorporated in the analysis.
Emelyanov ( 2007 ) analysed sediment echosounder and sediment core data on NW-
SE tracks crossing the basin axis perpendicularly. The digitized data from these
profiles have also been integrated into the database so that finally an adequate data
set was available for mapping of the subsurface of the base of the A3 zone (top of
glacial sediments) and the base of the B zones (top of the Ancylus Lake sediments).
The sea bottom surface is given by the bathymetric data of the Baltic Sea (Seifert
et al. 2001 ) . Having modelled the surface and subsurfaces the thicknesses of the A3
to A6 zone sediments (top of Baltic Ice Lake to top of Ancylus Lake) and B zones
(Littorina to recent Baltic Sea sediments) can easily be calculated and mapped. In
Fig. 5.10 both thickness maps can be compared.
For the A3 to A6 zone sediments the Eastern Gotland Basin and, in particular,
the Gdansk Basin form the depo-centres. The thickness maps support the results
achieved by core-to-core correlation (Fig. 5.12 ) . The transport and deposition are
obviously dominated by terrestrial (fluvial) sediment sources. The (paleo-) Wisla
River discharged its load to the Gdansk Basin whereas the Eastern Gotland Basin
sediments also descend from the (uplifting) Gotland Island in the west and from the
mainland in the east. In contrast, the depositional pattern of the younger B zones
is determined by particle load delivered by the currents entering the Gotland Basin
 
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