Geoscience Reference
In-Depth Information
of the Baltic Sea, in northern Poland, and in the area of the Rügen Island. After
small amplitude faulting in the Mesozoic, the tectonic activities increased during the
Cretaceous inversion in the south-western part of the basin. The bottom morphol-
ogy of the Baltic Sea mirrors large-scale ancient structures, but glacial erosional
processes contributed undoubtedly to the shape and the depth of the Baltic Sea. Oil,
gas, geothermal energy, and reservoir formations which can be used as storage sites
(natural gas, CO
2
, compressed air) are the major resources of the deeper under-
ground of the Baltic basin. Amantov et al. assume that Plio-Pleistocene erosion
and sedimentation significantly impact post-glacial uplift of the basin. The authors
estimate that in the last glacial cycle, sedimentation could produce up to 155 m of
subsidence, and erosion 32 m of uplift. The analysis is based on the changes in sur-
face load caused by glacial and post-glacial erosion and sedimentation over 1,000
year time intervals (coarser intervals before 50,000 years) utilizing a largely auto-
mated interpretation of regional geological and geomorphological observations. The
analysis suggests that the first glaciations probably shaped the major over-deepened
troughs, and younger glaciations mainly removed sediments left by their predeces-
sors, decreasing the thickness of the Quaternary succession and only locally incising
and changing the dip of the bedrock surface. The basin fill provides in particular for
the last glacial cycle (LGC) valuable records for the reconstruction of the changing
climate of the northern Europe.
The Quaternary sedimentary fill of the Baltic basin provides the records for
the
reconstruction of the climate and sea level history
(Part III) of the border
area between the northeast Atlantic and Eurasia. Despite the erosional effects
of the Weichselian ice sheet, sediments displaying the whole LGC are at least
fragmentarily preserved, and Late Pleistocene to Holocene sediments display the
environmental change continuously by high-resolution proxy-data records. This
topic of climate history is approached here by three articles. Andrén et al. describe
the environmental change within the Baltic area for the last 130,000 years. First,
the authors compare the conditions of the Eemian interglacial with the modern
warm period and conclude that both salinity and sea surface temperature of the
Baltic Sea were significantly higher during at least parts of the last interglacial,
130-115 ka BP. Also, the hydrology of the Baltic Sea was significantly different
from the Holocene because of a pathway between the Baltic basin and the Barents
Sea through Karelia that existed during the first ca. 2.5 ka of the interglacial. A
first early Weichselian Scandinavian ice advance is recorded in NW Finland during
marine isotope stage (MIS) 4 and the first Baltic ice lobe advance into SE Denmark
is dated to 55-50 ka BP. After the last glacial maximum (LGM), ca. 22 ka BP, the ice
sheet retreated northwards with a few still stands and re-advances, and by ca. 10 ka
BP the entire basin was deglaciated. After different freshwater stages, full brackish
marine conditions were reached at ca. 8 ka BP. The present Baltic Sea is charac-
terized by a marked halocline, preventing vertical water exchange and resulting in
hypoxic bottom conditions in the deeper part of the basin. Harff et al. have inves-
tigated sediment echosounder data and sediment cores from the eastern Gotland
basin in order to reconstruct Holocene hydrographic and climatic conditions for the
Baltic Proper. The down-hole physical facies variations from the eastern Gotland
