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Chronostratigraphy of the Vistulian glaciation on the Kujawy Moraine Plateau (Central Poland) based on lithostratigraphic research and OSL dating

100%

Przegiętka K. R. , Chruścińska A. , Oczkowski H. L. , Molewski P.

tom Vol. 32

69-77

The subject of the investigations presented here is fixing dilemmatic character (transgressive or recessive) of the Poznań phase of the Vistulian (Weichselian) Glaciation and answering the question about the possibility of lithostratigraphic separation of this phase from the Leszno phase in the region of so called Vistula lob. Here we present the outcomes of the research project carried out on a few tills exposures, which constitute the sedimentological record of the last ice sheet advance on the Kujawy Moraine Plateau. The absolute ages of 17 samples (collected from fluvial deposits uncovered in the geological logs) have been determined by means of the OSL method applying the single aliquots regenerative (SAR) dose protocol. The OSL data are analysed with regard to supposed bleaching conditions at the moment of the last transport and deposition of the material. In conclusion, some remarks on suitability of fluvial sands for OSL dating are made. In most of the investigated sites, there appears to exist only a single till level associated with the main stage of the Vistulian Glaciation. This fact and the results of OSL dating support the hypothesis, that the Poznań phase in Kujawy Moraine Plateau is not a distinct lithostratigraphic unit, but it is a recessive phase of the last glaciation.

Optical dating of a late quaternary sediment sequence from Sokli, Northern Finland

80%

Alexanderson H. , Eskola K. O. , Helmens K. F.

tom Vol. 32

51-59

Interstadial and non-glacial stadial sediments collected in boreholes from Sokli in northeastern Finland have been dated by optically stimulated luminescence on quartz and feldspar grains. The quartz OSL ages follow stratigraphic order, with one exception, and support the litho- and biostratigraphical correlation with the NW European mainland climate-stratigraphy and the marine oxygen-isotope stages. Feldspar IRSL dates generally overestimate the age, probably due to incomplete bleaching. The data show that during the last glacial cycle north-eastern Finland was not glaciated until MIS 5b, around 90 ka. Interstadial conditions occurred around ∼94 ka (MIS 5c), ∼74-80 ka (MIS 5a) and 42-54 ka (MIS 3). The OSL ages have large standard errors mainly due to small sample sizes, relatively poor luminescence characteristics and uncertainties in dose-rate determinations.