Search

Digital elevation models, based on laser scanning imageries (LiDAR-DEM) and aided by ground penetrating radar (GPR) data, were used to study glaciofluvial Gilbert-type ice-contact deltas in the Younger Dryas Salpausselkä end-moraine zone in southern Finland. The geomorphological data analysed were used to reconstruct the water-level drop of the late glacial Baltic Ice Lake to the early Holocene Yoldia Sea and tie these changes to a wider stratigraphic context. The results indicate that the sudden drainage event at around 11 650 cal. yrs BP left its imprint not only on the varved sediments but also on ice-contact glaciofluvial deltas in the Second Salpausselkä zone throughout southern Finland. This morphostratigraphic boundary can be placed at locations where the ice-contact deltas occur at two different levels; the higher-level deltas formed during the Baltic Ice Lake B III water-level stage and the lower-level deltas during the Yoldia Sea Y I water-level stage. This morphostratigraphically defined boundary in southern Finland marks the Pleistocene/Holocene chronostratigraphic boundary in southern Finland and shows the corresponding positions of the Scandinavian Ice Sheet's Finnish Lake District Ice Lobe and the Baltic Sea Ice Lobe. [ABSTRACT FROM AUTHOR]

Pollen analysis is a commonly used method to interpret vegetation and environmental change. The standard pollen preparation technique in minerogenic sediments involves the use of hydrofluoric acid (HF) which is highly toxic. Currently the European legislation requires that hazardous chemicals should be substituted with less hazardous or nontoxic chemicals if possible. In the present paper the authors introduce a safer pollen preparation method, based on the use of low-toxic heavy liquid lithium hetero polytungstate (LST Fastfloat) and provide instructions for pollen preparation with the LST Fastflow method. Furthermore, five paired samples were processed from clayey and silty sediments with LST Fastfloat and conventional HF methods and the pollen and spore counting results obtained from these two methods were compared to test if there is statistically significant differences between the taxa. Calculation of the 95 % confidence interval revealed statistical agreement in all studied taxa except one taxon in one sample pair. However, the study revealed systematic differences within two taxa, Betula and Pinus. Thus caution is needed when comparing results obtained by HF and heavy liquid (LST Fastfloat) methods. [ABSTRACT FROM AUTHOR]

Glaciofluvial ice-contact deltas were mapped and altitudes of the highest shorelines defined in the eastern arc of the Salpausselka zone, southern Finland, using Light Detection and Ranging (LiDAR)-based digital elevation models and GIS tools. Mapping of deltas and the highest shorelines in the Salpausselka zone were undertaken in order to calculate and define the glacio-isostatic uplift palaeo-isobases, uplift gradients and equidistant diagrams (distance diagrams) for the Salpausselka zone. The results indicate that the glacio-isostatic uplift palaeo-isobases were orientated NE-SW (50°-230°) and the uplift gradients for both the First and the Second Salpausselka in the eastern arc, are virtually the same, namely 0.6 mkm-1. This suggests that both Salpausselka ridge complexes, which were originally laid down in front of the Finnish Lake District Ice Lobe (FLDIL) in relatively shallow water, were deposited within a short time period during the Late Weichselian Younger Dryas Stadial. The results also suggest that the Baltic Ice Lake water level regressed 7.5 metres from Baltic Ice Lake level B I to level B III as the ice retreated in its eastern arc from the First to the Second Salpausselka. [ABSTRACT FROM AUTHOR]

Over the past tens of years, glacial sandstone erratics variably enriched In Zn, Pb and Cu have been collected from the coast south of Raahe, but their source has remained ambiguous. In these non-metamorphosed and non-deformed boulders, detrltal grains of quartz and minor feldspar are cemented by calcium carbonate, which is partly or wholly replaced by ore minerals, Including sphalerite, galena, pyrlte, marcaslte, and chalcopyrite. Analyzed mineralized boulders have yielded total base metals contents between 1 and 19 wt.%. The FeS content in sphalerite Is low and variable, ranging commonly between 0.5 and 15 mol.%, which is in harmony with its coexistence with pyrlte. Galena shows very radiogenic Pb isotope compositions, with 206Pb/204Pb and 207Pb/204Pb falling In the ranges of 20.55-21.06 and 15.90-15.94, respectively. These compositions are similar to those measured for the Lalsvall MVT Pb-Zn deposit in the Swedish Caledonides, being consistent with a similar Ordovician age of ore formation. However, S isotope analyses yielded heterogeneous compositions, with pyrlte showing mostly negative δ34S values from -15.6 to -7.6%o, Indicating partly a strong bacteriogenic signature, which are distinctly different from the generally heavy sulfur isotope compositions (avg. δ34S +24%O) reported from the Lalsvall-type deposits, pointing to a different source of sulfur. These results together with some mlneralogical differences (relatively abundant chalcopyrite, scarcity of fluorite and barite) suggest that the boulders were not derived from the eastern front of the Caledonian orogen but their provenance occurs much closer, potentially In a so-far-undiscovered occurrence of stratabound base metal mineralization in Cambrian sediments under the Bothnia Bay. The direction of transportation of the sandstone boulders can be estimated using associated carbonate and mafic metavolcanite boulders whose carbon isotope and major and trace element compositions, respectively, Indicate their derivations from the Kalix area, northern Sweden. [ABSTRACT FROM AUTHOR]

The SIS (Scandinavian Ice Sheet) became divided into several active, semi-independent ice lobes during the last deglaciation ca 13 000–10 000 years ago. The largest of them, the North Karelian/Oulu Ice Lobe (NKIL/OIL), covered vast areas in central Finland and in northwest Russian Karelia. This paper studies the behaviour and subglacial conditions of the NKIL/OIL with the inversion modelling method. The method is based on the identification and interpretation of mapped glacigenic streamlined lineations, formed during active flow stages of the NKIL/OIL. DEM and LiDAR data on lineations was obtained from seven subsets in different zones of the NKIL/OIL. Results indicate that the NKIL/OIL dynamics were strongly affected by pre-existing Quaternary sediment thickness, bedrock lithology, structures and topography. Due to these factors, the NKIL/ OIL operated through several flow corridors and had several retreat and re-advance cycles throughout its life span. [ABSTRACT FROM AUTHOR]

A multiple till succession at Koivusaarenneva in Central Ostrobothnia, adjacent to the Gulf of Bothnia, was studied using conventional sedimentological techniques. In addition, a sand-rich unit between two till beds was dated by the Optical Stimulated Luminescence (OSL) method and organic-bearing silt was subjected to pollen analysis. The methods were applied to determine the Pleistocene sedimentation history of the area. The results obtained indicate that the lowest till above the crystalline bedrock at Koivusaarenneva was deposited from the NNW during the Saalian glaciation, whereas the organic-bearing sediments and deformed sand and silt above, were laid down during the Eemian and the Early Weichselian stages. Two till beds above the Early Weichselian sediments indicate that at least two separate Scandinavian Ice Sheet advances took place in the area, most likely in the early Middle Weichselian and the Late Weichselian substages. [ABSTRACT FROM AUTHOR]

The Rautuvaara section in northern Finnish Lapland has been widely considered as the stratotype for the northern Fennoscandian late Middle and Late Pleistocene. It exposes four till units interbedded with sorted sediments resting on Precambrian bedrock. In order to shed light on the Scandinavian Ice Sheet ( SIS) history and palaeoenvironmental evolution in northern Fennoscandia through time, a chronostratigraphical study was carried out at the Rautuvaara site. The succession was studied using sedimentological methods and different sand-rich units between till units were dated using the Optical Stimulated Luminescence ( OSL) method. The results obtained indicate that the whole sediment succession at Rautuvaara was deposited during the Weichselian Stage and there is no indication of older deposits. The SIS advanced across Finnish Lapland to adjacent areas to the east at least once during the Early Weichselian, twice during the Middle Weichselian (∼ MIS 4 and MIS 3) and once during the Late Weichselian substages. Glaciolacustrine sediments interbedded between the till units indicate that a glacial lake repeatedly existed after each deglacial phase. The results also suggest that there were two ice-free intervals in northern Fennoscandia during the Middle Weichselian close to the SIS glaciation centre. [ABSTRACT FROM AUTHOR]

The lithostratigraphy of pre- Late Weichselian sediments and OSL-dating results from four localities in the Suupohja area of western Finland, adjacent to the centre of the former Scandinavian glaciations, are presented. The studied sections expose glacifluvial, quiet-water, littoral and aeolian deposits overlain by Middle and/or Late Weichselian tills. Litho- and biostratigraphical results together with seven OSL age determinations on buried glacifluvial sediment at Rävåsen (94±15 ka) and on till-covered littoral and aeolian sediments at Risåsen, Rävåsen, Jätinmäki and Kiviharju (79±10 to 54±8 ka), accompanied by previous datings and interpretations, suggest that the glacifluvial sediments at Risåsen were deposited at the end of the Saalian Stage ( MIS 6) and those at Risåsen were deposited possibly in the Early Weichselian Substage (MIS 5d?). Palaeosol horizons and ice-wedge casts together with the dated littoral and aeolian sediments between the Harrinkangas Formation ( Saalian) and the overlying till(s) indicate that western Finland was ice-free during most of the Weichselian time. Littoral deposits, dated to the Middle Weichselian ( MIS 4-3), occur at altitudes of 50-90 m a.s.l., which indicates significant glacio-isostatic depression. The depression resulted from expansion of the ice sheet in the west of Finland at that time. [ABSTRACT FROM AUTHOR]