Geoscience Reference
In-Depth Information
widest point and 385 m at its narrowest. Due to permanent cleaning and dredging of
the harbour basin area its depth varies from 8.0 to 14.5 m.
Geological setting of the Klaipeda Strait region is complicated. The lower-
most part of the Quaternary sedimentary sequence was formed during the last
few glacial-interglacial cycles and is represented by layers of glacial, glacioflu-
vial, glaciolacustrine, limnic and organogenic sediments, while the uppermost part
was formed in the Late glacial and Holocene during a few stages of the Baltic Sea
development (Fig. 6.2 ) . The dredging of the strait opens the layers of fine-grained
sand filled by groundwater. Some of these layers are under high hydrostatic pressure
that causes sub-aquatic suffusion posing a threat to the jetties of the seaport. Thus,
the complicated geological structure and hydrogeological conditions were the valid
reason to start a detailed (at a scale of 1:5 000) engineering geological mapping of
the Klaipeda Strait area. The vast majority of geological information presented in
this chapter was collected during this mapping.
The Klaipeda Strait and surroundings, investigated in detail, can be considered as
an important key area for the Lithuanian Coastal Area and whole Western Lithuania.
During the different stages of the Baltic Sea development - the Baltic Ice Lake,
Yoldia Sea, Ancylus Lake, Littorina and Post-Littorina Seas - the paleogeographic
situation in the Klaipeda Strait environs was very different and changeable, but this
Fig. 6.2 Geological cross-section along the Klaipeda Strait: 1 - borehole and its number; 2 -sur-
face of pre-Quaternary sediments; 3 - upper Jurassic sediments; 4 - lower Cretaceous sediments;
5 - middle Pleistocene glacigenic sediments; 6 - middle Pleistocene glaciofluvial and glaciola-
custrine sediments; 7 - upper Pleistocene glacigenic sediments with glaciotectonized blocks of
inter-till limnic sediments; 8 - late glacial and Holocene marine and lagoonal sediments; 9 -
Holocene aeolian sediments; 10 - anthropogenic sediments. Lithology of sediments: 11 - till;
12 - boulders; 13 -sandwithgravel; 14 - various-grained sand; 15 - fine-grained sand; 16 -very
fine-grained sand; 17 - silty sand; 18 - sandy silt; 19 -clay; 20 - gyttja, peat; 21 - fine dispersal
remnants of organic matter; 22 - glaciotectonic features (folds, thrust faults); 23 - sampling point
for infrared optically stimulated luminescence (IR-OSL): number indicates the luminescence age
of sediment (in ka)
 
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