Palaeogeographic Model for the SW Estonian Coastal Zone of the Baltic Sea - The Baltic Sea Basin - page 169

A map with the isobases of the recent postglacial rebound of Fennoscandia and
Baltic compiled by Ekman ( 1996 ) was used to reconstruct the relative sea-level sur-
face for the 100-year period (1892-1991). Apparent uplift rates on Ekman's map
were calculated from the sea-level and lake-level records combined with repeated
high-precision levelling results, and the uncertainty of these rates was estimated
to be 0.5 mm/a and less (Ekman 1996 ) . The uplift rates of Ekman's map were

recently compared to the velocities of the permanent GPS stations, and overall
agreement (consistency) was found at the 0.5 mm/a level (Lidberg et al. 2009 ) .

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8.3.2 Water-Level Change Curve for the Pärnu Area

A set of 18 sites within an area of 3,500 km 2 displaying 66 radiocarbon dates from
different stages of the Baltic Sea at different levels (Table 8.1 ) was used to recon-
struct the water-level curve for the area (Veski 1998 , Heinsalu et al. 1999 , Veski
et al. 2005 , Saarse et al., 2003 , 2006 ) . Before reconstructing the curve, the correc-
tion for the spatial spread of the sites was applied using interpolated surfaces of
water levels with different shoreline tilting gradients. All sites were transposed to
the Paikuse location (Fig. 8.2 ) . The elevations of the pre-Ancylus Lake and Ancylus
Lake sites (sites 1-27 in Table 8.1 ) were corrected in respect to the Ancylus Lake
surface and the pre-Littorina and Littorina Sea sites (sites 28-61 in Table 8.1 ) in
respect to the Littorina Sea surface. For correction of the Littorina Sea regression
sites (sites 16-18 in Table 8.1 ) , the Littorina Sea surface was combined with the
Baltic Sea surface at 100 years ago (Ekman 1996 ) assuming a linear decay in shore-
line tilting gradient and the differences in elevation were calculated depending on
the age of each site (for details see Sect. 3.3 ).
The data can be divided into six groups that delimit the various stages of the
Baltic Sea in the past (Fig. 8.3 ) . Baltic Ice Lake coastal landforms at different levels
form the first group, representing the time span from the deglaciation of the area
to the Billingen drainage (Figs. 8.2 and 8.4 ) . The second group represents organic
matter from the lowstand of the Baltic Sea during the Yoldia Sea and Ancylus Lake
stages buried under the transgressive Ancylus Lake waters (Table 8.1 ) , and the third
group embraces the coastal landforms from the culmination of the Ancylus Lake
transgression (Figs. 8.2 and 8.3 ) . The fourth group represents buried organic mat-
ter of the period between the transgressions of the Ancylus Lake and the Littorina
Sea at altitudes above 0 m a.s.l. A subgroup of this set is the cluster of dated
organic matter from Uku and Reiu (Fig. 8.2 ) at altitudes distinctly below 0 m a.s.l.
(Table 8.1 ) , which is discussed separately due to suspected redeposition. The coastal
landforms from the culmination of the Littorina Sea make up the fifth group, and
the few sites that define the water level after the Littorina Sea transgression form
the last group (Figs. 8.2 and 8.3 ) . Thus the described groups record three regres-
sive phases interrupted by two transgressive phases (Ancylus Lake and Littorina
Sea transgressions) in the Baltic Sea water-level change history in the Pärnu
area (Fig. 8.3 ) .