Glacial Erosion/Sedimentation of the Baltic Region and the Effect on the Postglacial Uplift - The Baltic Sea Basin - page 61

Fig. 3.3 Sample output of glacial sedimentation module: 1 - end-moraine ridges; 2 - peripheral
sediments; 3 - products of subglacial sedimentation
The complement to erosion is sediment accumulation. This can occur under
or outside the ice. We distinguish the glacial, interglacial, and postglacial sedi-
ment deposition patterns. For example, a glacial sedimentation module simulates
the formation of end-moraine ridges, subglacial (i.e., drumlins, flutes, eskers), and
peripheral deposition that deals with meltwater redeposition of a material (Fig. 3.3 ) .
The thickness and width of end-moraine ridges are approximated as random within
defined bounds that are controlled by presumed sediment supply to the ice margin,
the mobility of the ice front, and the ice-stream pattern. Time-dependent grids spec-
ify the lithology at the base of ice. An interglacial-postglacial deposition module
forecasts thickness of debris accumulated between and after Weichselian erosion
episodes, when additional automated time-slice modules estimate the possible
thickness of interglacial sediments. This module was calibrated against Holocene
offshore and onshore data. Figure 3.3 shows the pattern of sediment accumula-
tion. Any sediment pockets could be individually resolved, depending on input grid
resolution.
The results of this kind of analysis are illustrated in a corridor that runs from the
northern Gulf of Bothnia across Finland and the Gulf of Finland into the Russian
Plain in Fig. 3.4 . The northern shore of the Gulf of Finland marks the approxi-
mate northern border of the Baltic-White Sea lowland - the area that contains the
most erodable material that was particularly affected by glacial erosion. Figure 3.4a
shows how we believe this transect looked at the end of the Tertiary before it
was affected by any continental glaciations. Figure 3.4b shows the erosion that
was accomplished in the first glacial cycles, showing the situation just after one