Submerged HoloceneWave-Cut Cliffs in the South-eastern Part of the Baltic Sea: Reinterpretation Based on Recent Bathymetrical Data - The Baltic Sea Basin - page 207

The topographic cross section of the southern part of the Baltic shows the absence
of step- or ridge-like formations. The first-order morphostructure mentioned con-
tains complex second-order structures, represented in the area of study by the
Curonian-Sambian Plateau, separated from the central Baltic depression in the
west by linear morphostructures (tectonic scarps) which correspond to fault zones
(Fig. 10.2 ) . At places, these cliffs coincide with fossil coastlines. Marine accumu-
lation formations are common at the bottom offshore, while erosion-accumulation
structures occur in the coastal area. Erosion-accumulation surfaces are usually rep-
resented by seaward-inclined plains, the relief of which shows recent and ancient
wave-cut cliffs and accumulation formations. These fossil coastlines correspond
to different stages of the Baltic history. The Curonian-Sambian Plateau is char-
acterized by having a complex late- and post-glacial erosion-accumulation-terraced
topography, with relics of glacial-accumulation undulations. Ancient wave-cut cliffs
are extremely common. The SE part of the Gulf of Gdansk shows the presence
of an extensive moraine plain banded by limno-glacial surfaces (Gelumbauskaite
et al. 1991 ) .
10.3 Previous Studies
The first attempt to determine the possible location of the former coastlines in
the area of study was made by Gudelis in the early 1950s, who extrapolated the
shore record of the Lithuanian coast (Gudelis et al. 1977 ) . Subsequently, based on
echo-sounding, vibrocoring, and dredging data collected in 1965-1978 by research
vessels operated by the Atlantic Branch of P. P. Shirshov Institute of Oceanology
(USSR Academy of Sciences) and VNIIMorGeo, spectrograms of fossil coastlines
were developed (Gudelis et al. 1977 , Gelumbauskaite 1982 ) and wave-cut terraced
surfaces were mapped (Blazhchishin et al. 1982 ) .
The spectrogram described by Gudelis et al. ( 1977 ) consisted of six submerged
levels dated, from the bottom to the top, to the Yoldia Sea (Y) (on the Kaliningrad
coast; 58-63 m); the first Ancylus transgression (Anc1) (36-42 m); the first Littorina
transgression (Lit1) (27-33 m); the second Littorina transgression (Lit2) (15-20 m);
the second Ancylus transgression (Anc2) (4-10 m); and the third Littorina trans-
gression (Lit3) (2-7 m). As earlier levels were not preserved in the topography, they
were drawn as the best estimates. No signs of ancient coastlines could be detected
at depths exceeding 70 m, therefore that depth is considered to be the lowest post-
glacial Baltic level. The ancient coast slopes were determined by extrapolating the
coastal slopes of Lithuania and Latvia, i.e. north of the area of study. The vibro-
cores, dated by means of biostratigraphic proxies (diatom assemblages and fossil
macrofauna remains), made it possible to outline transgression-regression contacts
of differently aged sediment complexes originating at different stages of the Baltic
history. However, Gudelis et al. ( 1977 ) maintained that the geomorphologic and
biostratigraphic data they had were not adequate to be used for determining, tracing,
and dating the various complexes of submerged fossil coast formations.