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Pleistocene/early Holocene freshwater to brackish-marine environment can be seen
at a core depth of about 380 cm where almost homogeneous sediments at the bottom
are replaced to the top by laminated sequences. The reason for the general differ-
ence in the sedimentary facies is mainly caused by the halocline established by the
inflow of saline water. During the late Pleistocene and early Holocene, the Baltic
Basin was - except for the short Yoldia Sea Stage - disconnected from the world
ocean. Within the lacustrine, partly isolated basins, the sedimentary facies were con-
trolled primarily by variation in atmospheric temperature and precipitation. These
parameters controlled changing water levels and contours of coastlines and changing
supply of detrital sedimentary material from the drainage area. Lateral exchange of
water masses between the basins did not play the important role assumed for the late
Holocene when the permanent connection between the Baltic Sea and the Atlantic
Ocean was opened.
For the B zones laminated sediments prevail. However, it should be stressed that
zones B1, B3, and B5 are clearly laminated, while zones B2 and B4 (and B6) are
more homogeneous. This is interpreted as a result of bioturbation due to good supply
of oxygen to the bottom water. Zone B4 shows in its lower part still some lam-
ination and can be regarded as a transition from laminated zone B3 to the more
homogeneous structure of zone B4 (upper part). According to the dating, zone B5
represents the Medieval Climate Anomaly (MCA), while zone B6 denotes the Little
Ice Age (LIA). The recent warm period is not displayed because the gravity coring
system does not preserve the uppermost layers. The last 1,000 years is represented
by multi-corer (MUC) samples that Leipe et al. ( 2008 ) describe from the Eastern
Gotland Basin (site: 56 55 N, 19 20 E).
In Fig. 5.7 also the age model used for the master station is given as a curve. The
age data of the zone boundaries have been projected from core 211660-1 to cores
211660-5 and 313610-12. The age model of core 211660-1 which combines data
from paleomagnetic studies, AMS dating, and glacial varve analyses is explained
by Harff et al. ( 2001a ) . Kotilainen et al. ( 2000 ) used inclination and declination of
magnetic measurements of sediment cores for comparison to the secular variation
recorded in varved lake sediments in Finland to date the sedimentary sequence over
the past 3,000 years. Littorina Sea sediments were dated by Andrén et al. ( 2000 )
by AMS 14 C analysis. These dating results are still used here and by Andrén et al.
( Chap. 4 ) in this topic since no more reliable data for Littorina Sea sediments for
the master station have been published during the last years. Dating of glacial varves
came frommeasuring and correlating the Swedish time scale to the Greenland GRIP
ice core
18 O record (Andrén 1999 , Andrén et al. 2000 ) .
δ
5.5.2 Spatial Correlation of Late Pleistocene
to Holocene Sediments
In order to correlate the lithostratigraphic zonation from the basin centre along the
basin axis to the SW, the Stolpe Foredelta, and the Gdansk Basin (Fig. 5.3 ) , the cores
along a profile marked in Fig. 5.5 have been compared based on their MSCL data
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