Matti Saarnisto

Glaciation of Finland

This chapter discusses the glaciation history of Finland. According to the Finnish till stratigraphy, there are six stratigraphically significant till beds in Finnish Lapland. The uppermost three represent Weichselian tills. The so-called Till Bed IV was laid down during the Saalian glaciation, and the two lowermost till beds that underlie a Holsteinian peat stratum may represent Elsterian or pre-Elsterian tills. Although Elsterian or pre-Elsterian tills are preserved at scattered localities in northern Finland, there is no conclusive evidence for pre-Saalian tills in Southern Finland. In southern Finland, there are no end-moraines related to the early or middle Weichselian ice advances. Information on the extent of the ice streams is limited and based on the distribution of interstadial organic remnants and till stratigraphy. The stratigraphy of the Early and Middle Weichselian substages in Northern Finland is based on the correlation of interstadial organic deposits, till stratigraphy and till-covered glaciofluvial landforms. Many stratigraphically important areas and key localities are situated in the ice divide zone in Central Lapland. It appears that the processes of glacial erosion and deposition were ex-ceptionally weak in this zone.

Lateglacial of Lake Onega — Contribution to the history of the eastern Baltic basin

Abstract New stratigraphy data especially diatom analyses are presented from the area north of Lake Onega relevant to the discussion on possible Lateglacial connection between the Baltic Sea and White Sea. Following the deglaciation 12,000–11,000 years ago Lake Onega basin was occupied by a system of ice dammed lakes which drained to the Lake Ladoga basin. When the ice retreated from the threshold leading to the White Sea 11,000 years ago the water level dropped and since that the lake was controlled by its thresholds to the White Sea and the Baltic basin. Lake Onega has remained distinctly above the sea level and no Late Weichselian sea connection existed between the White Sea and Baltic basins. The marine diatoms frequently found in sediments are reworked older fossils as also suggested by some earlier workers. Lake Onega drained to the White Sea basin over the Maselga threshold and also to Lake Ladoga between 11,000 and 10,000 radiocarbon years ago, and to the White Sea alone between 10,000 and 9500 years ago, and the present outlet of Lake Onega, River Svir, originated 9500 years ago.

Comparative varve counting and magnetic properties of the 8400-yr sequence of an annually laminated sediment in Lake Valkiajärvi, Central Finland

Two varve counts made nearly 20 yrs apart and by different authors in the small and well sheltered meromictic lake of Valkiajärvi were compared with a view to establishing how similar, or otherwise, these two independent varve chronologies might be. The results were significant, the difference between the two varve counts being less than 2% for most of the sediment length, even though the average varve thickness was only 0.3 mm. The continuous and essentially uniform varve record - so far the longest in Finland - covers 8400 yrs and could be applied for accurate dating of palaeoenvironmental indicators in the sediment. As an example, we present a varve-dated pollen diagram for Lake Valkiajärvi.In addition, some magnetic parameters (susceptibility, ARM, SIRM) were measured on the sediment sequence to support the stratigraphic division and correlation of the cores, and to outline the development of the basin since the last deglaciation. Magnetic variables reflected mainly the variation in minerogenic material in the sediment, and were therefore related to changes in the catchment. The magnetic parameters also showed a drastic change some 6000 yrs ago, the reason for which, unfortunately, is still not fully understood.

Shoreline displacement of Lake Ladoga — new data from Kilpolansaari

Dating of sediments sampled from small lakes in the Kilpolansaari region, in the NW part of Lake Ladoga, indicate that the River Neva, which is the present outlet of Lake Ladoga, originated at 3,100 radiocarbon years BP. This is in agreement with some earlier estimations but no consensus concerning the age of the River Neva has previously been reached. New diatom data provide information concerning salinity and nutrient conditions in northern Lake Ladoga prior to the formation of the River Neva, when the Litorina Sea occupied the Baltic basin and approached the level of the ancient Lake Ladoga. Some slightly brackish water diatom species may indicate occasional saline water incursions into the Ladoga basin but, on the other hand, slightly brackish water species also occur in the present Lake Ladoga.

Stone Age to recent land-use history at Pegrema, northern Lake Onega, Russian Karelia

Abstract. The village of Pegrema in Karelia may be regarded as a Stone Age innovation centre in the large Lake Onega area. Two pollen and plant macrofossil diagrams are presented which represent the first contribution to the study of human impact in the area using anthropogenic pollen indicators. A continuous but sporadic human presence from the Mesolithic onwards is demonstrated. While there is no archaeological evidence relating to the period 4200–3000 B.P., the pollen data suggest continuous, though rather sparse human presence. The data do not support any natural catastrophes in Pegrema as has been suggested elsewhere. Cerealia pollen is recorded earlier than expected (c. 5000 B.P.=. In the Bronce Age and Iron Age, the settlement of the Zaonezhye peninsula is reflected by a slight increase in herb pollen representation, sporadic Cerealia pollen and several periods of regression in Picea. The long introductory period of agriculture to the area, as well as the similarities and discrepancies between different sources of evidence (palaeoecological, archaeological and historical) are discussed at some length. The start of land clearance for permanent cultivation in the profile Pegrema S was dated to the late 13th century. The beginning of more intensive field cultivation in the 15th century is clearly seen in the pollen succession at both localities. The fluctuation in anthropogenic indicators can be related to population density based on historical data. The village of Pegrema was depopulated in 1956 which is reflected in a distinct decline in settlement indicators.

Valdaian glacial maxima in the Arkhangelsk district of northwestern Russia

Abstract The marginal configurations and ages of the Valdaian (Weichselian) glacial maxima in northern Russia have hitherto not been well established, thus, numerous versions of the Last Glacial Maximum (LGM) positions of the Scandinavian Ice Sheet are known ( Fig. 1B ). New data on ice sheet growth and decay indicate at least three glacial maxima during the Late Pleistocene each with individual spreading centres and different ages. Results of modern investigations in the Arkhangelsk region, conducted by the authors, are compared with an analysis of previous data on the Late Quaternary geology of Northwest Russia, which comprises a thorough presentation of Russian literature on this subject. This has allowed us to question and revise former models on Valdaian glaciation history and ice-marginal positions in a major part of the Russian North. An Early-Middle Valdaian (c. 70 ka BP) glaciation from the east and southeast, possibly originating on the Timan ridge, crossed the Pyoza River basin and reached the White Sea coast along the Bay of Mezen. The southern terminus of the ice sheet is probably found along parts of the Mezen River ( Fig. 2A,B ). The presence of an Early-Middle Valdaian Scandinavian glaciation, which covered the Arkhangelsk region and in neighbouring areas of Karelia and Vologda is not supported by geological data. In the Middle Valdaian (c. 70 ka BP) an ice sheet from the Barents-Kara Sea flowed from the north, northeast and reached the lower Pyoza River and the south and western shores of Mezen Bay on the White Sea coast. The terminal formations of its maximal stage stretch from west to east just north of Pyoza River and then run marginal to the Timan ridge from the north joining with the Markhida end-moraines on the Pechora Lowland ( Fig. 2A, B ). During the Late Valdaian, the Scandinavian Ice Sheet occupied the northwestern part of the Arkhangelsk region around 19-17 ka BP. The limit of this Late Valdaian glacial maximum runs from the White Sea shore of the Kanin Peninsula in the north, along the Kuloi River south of Mezen to the Middle Pinega River, crossing the rivers Severnaya Dvina and Vaga near the villages of Cherevkovo and Ust-Padenga. The glacial boundary bordered the Melovian and Nyandoma high ground and continued southwestwards to Lake Kubenskoe in the Vologda region. The Pyoza, Mezen and Vashka river basins remained ice-free during the Late Valdaian time, this area being covered by fluvial flood plains, with abundant evidence of permafrost and lakes. The latter have yielded pollen evidence indicating an arctic to subarctic environment between 18-10 ka BP ( Fig. 2A, B ).

Late- and postglacial history of lakes of the Karelian Isthmus

The Late Pleistocene and Holocene history of five lakes in the central part of Karelian Isthmus, south of the present Vuoksi River, are described on the basis of sediment stratigraphical investigations. Two of the Lakes, Michurinskoe (94 m a.s.l.) and Uzornoe (55 m a.s.l.) are situated in an upland area that remained dry land after the deglaciation even during the early high water stages of the Baltic Sea (Baltic Ice Lake until c. 10000 yr BP and Ancylus Lake 9500–8800 BP). The low-lying central parts of the Isthmus were flooded by the outflow of Lake Ladoga that took place across this area until the formation of Neva River, c. 3100 yr BP, and further by the waters of River Vuoksi that started flowing into the area from the NW c. 5000 yr BP as a new outlet of Lake Saimaa. The basins of the lakes Krasnoe and Vishnevskoe (both 16 m a.s.l.) became isolated when River Neva was formed and Lake Ladoga sank to its present level. Lake Rakovoe (12 m a.s.l.) was on the level of River Vuoksi up until the mid-19th century, when water level in the central stretch of the river was artificially lowered. Each of the lakes has been variously affected by hydrological and climatic changes and consequences of human activities, e.g. eutrophication due to intensified land use. As a consequence to artificial lowering, done in order to gain field and meadowland, the large, shallow Lake Rakovoe has been largely overgrown by macrophytic vegetation.

Climate Variability in Europe and Africa: a PAGES-PEP III Time Stream II Synthesis

The PEP III Europe-Africa transect extends from the arctic fringes of NW Eurasia to South Africa. It encompasses the presently temperate sector of mid-latitude Europe, the Mediterranean region, the arid and semi-arid lands of the Sahara, Sahel and the Arabian Peninsula, and the inter-tropical belt of Africa. The palaeoenvironmental evidence available from these regions, which has been summarised in earlier chapters of this volume and which collectively spans the last 250,000 years, clearly bears the stamp of long-term global climate forcing induced by variations in solar insolation. External forcing is ultimately the reason why the Eurasian continental ice sheets waxed and waned repeatedly during the late Quaternary, and why the southerly limit of permafrost migrated southwards across mid-latitude Europe, periodically becoming degraded during warmer episodes. At the same time, pronounced fluctuations in atmospheric and soil moisture have affected the Mediterranean, desert and Sahel regions, while there is abundant evidence from every sector of the PEP III transect for marked migrations of the principal vegetation belts, as well as for other major environmental changes, that are also considered to reflect long-term climate forcing. It is only in the last decade or so, however, that the full complexity of the history of climate changes during the last interglacial-glacial cycle, and their environmental impacts in continental Europe and Africa, have begun to be recognised. The discovery of evidence for the abrupt Dansgaard-Oeschger (D-O) and Heinrich (H) climatic oscillations in Greenland ice-core (Johnsen et al. 1992) and North Atlantic (Bond et al. 1993) records, have prompted a re-examination of the continental record. This, together with a number of technical improvements in field and laboratory equipment, greater access to sites in remote and difficult terrain, diversification in the range of available palaeoecological and geochronological tools, and closer inter-disciplinary collaboration, have led to a more penetrating examination of the field evidence, which has progressed the science considerably. We can now see that the stratigraphical record is much more complex than appreciated hitherto, and more detailed and refined models of past climatic and environmental models are beginning to emerge. There is, for example, a growing body of evidence which suggests that D-O and H events had significant impacts on the environment of Europe and Africa, as well as on the Mediterranean Sea.

Constraints for the latest glacial advance on Wrangel Island, Arctic Ocean, from rock surface exposure dating

Abstract During an expedition to Wrangel Island in 1997, three samples of quartz veins were collected for surface exposure dating. Two were bedrock surface samples from different parts of the island, one was from a local boulder. The samples were collected where former coverage by valley glaciers can be excluded. Especially, the bedrock surface samples were expected to provide new constraints for the chronology of glaciations on the island and on the arctic continental shelf in the Beringian region. Minimum exposure age estimates for these bedrock samples, calculated on the basis of 10 Be concentrations, are 64,600±6400 and 26,400±2100 years. These estimates suggest that no major glaciations have affected Wrangel Island or the adjacent shelf area after 64,600±6400 years. Specifically, these dates seem to rule out any major glaciation during the Last Glacial Maximum (LGM). The estimates should however be regarded as preliminary, as only two bedrock surface samples were analysed, but are compatible with the absence of glacial morphology and sediments, and with radiocarbon dates from mammoth remains.

Gold in bedrock and glacial deposits in the Ivalojoki area, Finnish Lapland

Abstract Three types of Au mineralization are known in the Ivalojoki area, in the southern part of the granulite complex of Lapland. These are epigenetic quartz-carbonate and quartz-hematite veins, the likely source of placer gold, and an arsenopyrite-bearing shear zone at Harrioja. The average Au content of the quartz-carbonate veins is 0.2 ppm, varying between 0.002 and 3.0 ppm; 2–6 ppm Au has been detected earlier in the Makararova quartz-hematite vein. The maximum Au value in the Harrioja shear zone, where no placer gold has been found, is 0.4 ppm. Arsenic and Sb are both correlative with Au in veins and glacial till, as are Au and vein quartz in the till. The correlation between panned gold and instrumentally analyzed Au is low, as in most cases are the correlations between Au and other trace metals, till lithology and heavy minerals. The isotopic composition of trace lead from placer gold samples suggests the age of granulite metamorphism, but this may be spurious due to restricted sample material.