Geological Structure of the Quaternary Sedimentary Sequence in the Klaipeda Strait, Southeastern Baltic - The Baltic Sea Basin - page 144

Olando Kepure outcrop that also was most probably formed by a glacier advance
during MIS 4 (Molodkov et al. 2010 ) . According to fabric measurements in the
Olando Kepure outcrop, this till was formed by a glacier advancing from the north
(Bitinas 1997 ) . All these data are in good agreement with a reconstruction made
by Svendsen et al. ( 2004 ) according to which part of the southwestern margin of
the Eurasian ice sheet could have been situated in the Lithuanian Coastal Area or
in the whole Western Lithuania during the Weichselian early pleniglacial maximum
(MIS 4). The till bed formed during the early pleniglacial has been distinguished
in the neighbouring Western Latvia: in stratigraphic schemes it has been iden-
tified as Talsi Stadial (Zelcs and Markots 2004 ) . In the more southern region -
territory of Poland - the till bed of the same age has been identified as Swiecie
Stadial (Lindner and Marks 1995 , Ber 2006 ) . According to the assumptions of
some former researchers, the glacial advance could reach Lithuania during the early
Weichselian - the corresponding till bed was distinguished as Varduva Stage
in the stratigraphic scheme of Lithuania (Vonsavicius 1984 ) . Later this opin-
ion was not confirmed by factual data and the mentioned stratigraphic unit was
rejected from the stratigraphic schemes (Gaigalas 2001 , Satkunas et al. 2007 ) . The
results of geochronological investigations presented in this chapter suggest that the
Quaternary stratigraphic scheme of Lithuania should be supplemented by a new
stratigraphic unit (for instance, it could be named as Melnrage Stadial) valid for
Western Lithuania.
Thus, the evidence reported in this study does not support an opinion that the
till layer beneath the bottom of the Klaipeda Strait and those at the same alti-
tudes in the surroundings formed during the Warthanian (Medininkai) glaciation
(MIS 6). The till layers in the northern part of the Klaipeda Strait, lying between the
above-mentioned middle Weichselian till and pre-Quaternary sediments (Fig. 6.2 ,
boreholes 4/98, 8140, 10092), most probably belong to the middle Pleistocene.
6.6 Conclusions
The results obtained in this work show that the absolute majority of the IR-OSL
ages of investigated inter-till sediments beneath the bottom of the Klaipeda Strait
fall within the age range of MIS 5d-5a, i.e. these sediments were formed during
the early Weichselian. The sampled inter-till sediments are occurring not in situ,
but as blocks (rafts) within the till bed formed during the Weichselian (Nemunas)
glaciation. According to a reconstruction by Svendsen et al. ( 2004 ) , the latter most
probably can be associated with the ice movement during MIS 4 - part of the south-
western margin of the Eurasian ice sheet could have been situated in the Lithuanian
Coastal Area and, probably, in the whole Western Lithuania during the Weichselian
early pleniglacial maximum (MIS 4). This conclusion does not support the stand-
point that the till beds beneath the bottom of the Klaipeda Strait were formed during
the Warthanian (Medininkai, MIS 6) glaciation.
Acknowledgements We are grateful to colleagues Tatyana Balakhnichova and Marina Osipova
for their contribution to IR-OSL dating laboratory work reported here, to Helle Kukk for checking