Prolonged interglacial warmth during the Last Glacial in northern Europe

Few fossil-based environmental and climate records in northern Europe are dated to Marine Isotope Stage (MIS) 5a around 80 ka BP. We here present multiple environmental and climate proxies obtained from a lake sequence of MIS 5a age in the Sokli basin (northern Finland). Pollen/spores, plant macrofossils, NPPs (e.g. green algae), bryozoa, diatoms and chironomids allowed an exceptionally detailed reconstruction of aquatic and telmatic ecosystem successions related to the development of the Sokli Ice Lake and subsequent infilling of a relatively small and shallow lake confined to the Sokli basin. A regional vegetation development typical for the early half of an interglacial is recorded by the pollen, stomata and plant macrofossil data. Reconstructions of July temperatures based on pollen assemblages suffer from a large contribution of local pollen from the lake's littoral zone. Summer temperatures reaching present-day values, inferred for the upper part of the lake sequence, however, agree with the establishment of pine-dominated boreal forest indicated by the plant fossil data. Habitat preferences also influence the climate record based on chironomids. Nevertheless, the climate optima of the predominant intermediate- to warm-water chironomid taxa suggest July temperatures exceeding present-day values by up to several degrees, in line with climate inferences from a variety of aquatic and wetland plant indicator species. The disequilibrium between regional vegetation development and warm, insolation-forced summers is also reported for Early Holocene records from northern Fennoscandia. The MIS 5a sequence is the last remaining fossil-bearing deposit in the late Quaternary basin infill at Sokli to be studied using multi-proxy evidence. A unique detailed climate record for MIS 5 is now available for formerly glaciated northern Europe. Our studies indicate that interglacial conditions persisted into MIS 5a, in agreement with data for large parts of the European mainland, shortening the Last Glacial by some 50 ka to MIS 4-2.Peer reviewe

Syndepositional deformation in the Kurkiselkä esker, Kiiminki, Finland

Syndepositional and metadepositional deformation structures from an esker section in Kiiminki, Finland, are described and discussed. The small folds are suggested to be a response of cohesive, hydroplastic material to the drag of turbulent flow, and the accompanying differential pressure conditions. The data indicate a rippling mechanism. The small folds have a transition into more complicated structures derived mainly from syndepositional or metadepositional horizontal movements, apparently in part gravity-induced, which operated contemporaneously with the rippling mechanism. The syndepositional deformation structures of the category described are rather common in the Oulu vicinity, probably due to the widespread occurrence of water-laid deposits composed of fine sand, a grain size that favours this kind of deformation. They can readily be confused with deformation structures of other origin, which exist in juxtaposition within the same area

The northern discharge channel of ancient Päijänne and the palaeohydrology of the Atlantic period

The discharge and run-off of the Atlantic period are determined by the morphological measurements in the channel of the ancient Hinkua River discharging from the Finnish Lake Plateau. The climatic interpretation is discussed. The small run-off value and the dryness of the Atlantic period are in the first place a direct consequence of the greater evaporation caused by higher temperature

Consolidation of Finnish sediments by loading ice sheets

In the following the consolidation properties of clays are studied in Kimola and Ylikiiminki, Finland and, the general possibilities of the overconsolidation in the Finnish sediments created by the former overriding ice sheets are discussed. In general the conditions have favoured the sediments becoming consolidated by the glacier load and also for the consolidation properties to be preserved in the later history. In some environments the consolidation could, however, have been prevented or been partially or wholly lost. Because of this the non-existence of overconsolidation is not always significant as a negative evidence of a readvance of the ice sheet but greater confidence can be placed on the existence of overconsolidation

Acidification of till in Northern Finland: experimental study

The acid neutralizing capacity of till and some effects promoted by increasing acidity, were studied in a number of tills in northern Finland. pH profiles were measured in the field and acid neutralizing capacity (ANC mmol/100 g sample) in the laboratory as a function of the varying acidity in solution. The concentrations of Al, Ca, Mg, Fe, K, Mn, Zn, Cu and Sr in solutions were also analyzed. The results are presented in the form of graphs of ANC versus final pH of the solution and element concentration versus final pH. The total concentrations of the major elements were analyzed by XRF and those of trace elements by AAS. The pH measured in the test pits was lowest just below the ground surface, and rose rapidly to a value of 6 at a depth of about 1 m and then it remained more or less constant with depth. The laboratory analyses clearly suggest that the acid neutralizing capacity of till correlates well with sample depth. The ANC values, which represent the fast-working part of the capacity, are higher in the surficial parts owing to the easily soluble aluminium and iron hydroxides which have their origin in the weathering processes. The experiments resemble acid rain conditions, where the higher pH-level buffers are unable to neutralize the increase in acidity immediately, so that lower pH-level buffering processes such as Al and Fe hydroxide buffers come into play. The situation can be hazardous for both forests and surface water

Glacial geology and till geochemistry in ore exploration in the Tervola area, southern Finnish Lapland

Glacial geology and till geochemistry were studied in an ore exploration project in the Palaeoproterozoic Peräpohja Schist Belt in the Tervola area of southern Finnish Lapland. The starting point for the exploration were numerous Au-Cu-rich erratics, the source rock of which was unknown. The mapping of the glacial landforms was based on aerial photo interpretation. The structure, texture, lithology and geochemistry of the till were studied using test pits. Three sieved fractions together with a heavy mineral fraction of the till were analyzed chemically. The glacial landforms of the area include cover and ground moraines, drumlins, flute ridges and Rogen moraines. The ridges of the Rogen moraine were found to be composed of three different till beds. The surficial parts of the Rogen ridges showed very short transport distance, whilst the lower till was of more distant derivation. Gold and Cu contents in the till are above their regional background level sin every analyzed fraction in the two case study areas of Petäjävaara and Vammavaara. High metal contents in till are associated with basic volcanic rocks and their contact zones with quartzite in bedrock. Metal anomalies in till are usually very sharp-contrasted and dilute quickly with increasing distance from the source rock. The most useful indicator elements in till geochemistry, in addition to Au, are Cu, Te and Co. The combination of careful studies of glacial geology and till geochemistry proved to be a powerful means in locating source rock of glacially transported ore boulders in this area. As a result of the exploration, Cu-Au mineralization was localized at Petäjävaara