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1.
Frost-shattered bedrock and ventifacts interpreted to be abraded by drifting snow or ice particles occur frequently in the wooded areas of northernmost Sweden. Ice-wedge casts and periglacial involutions are encountered more sporadically. The phenomena cannot be explained by the present or the Holocene climate and demonstrably pre-date the last deglaciation. The relation to glacial and non-glacial stratigraphy, and to ice flow during the latest glacial stade, strongly suggests that the periglacial activity dates from the local Tärendö Interstadial, tentatively correlated with Odderade. The presence of the periglacial features implies not only that different morphological formations survived the erosive impact of the last continental ice sheet but also that in wide areas the very ground surface, including ventifacts in primary position, is the same today as during the interstadial. A similar situation appears to prevail in northernmost Dalecarlia and parts of Härjedalen and Jämtland in central Sweden.  相似文献   

2.
A peat layer beneath two till beds was found at Seitevare in Swedish Lapland. The pollen flora layer indicates deposition during the later part of the Eemian Interglacial. The vegetation consisted of open forests predominated by pine and birch, mixed with alder and spruce. The sedimentation took place in a small oligotrophic-dystrophic water basin with a pH about 5, according to the diatom flora. In an adjacent section, silty sediments with pollen indicating interstadial vegetation (birches, herbs) are covered by one till bed. These sediments are tentatively correlated with the Peräpohjola Interstadial in northern Finland and north-eastern Sweden. The lithostratigraphy indicates one pre-Eemian and probably three Weichselian glacial advances.  相似文献   

3.
Compared to the other islands in the Svalbard archipelago, Nordaustlandet offers only limited stratigraphical or sedimentological information on its Quaternary deposits. This article aims to fill the gap by presenting new results from glacial geological, sedimentological and chronological studies in the southern Murchisonfjorden area. Field data include reconnaissance mapping and detailed logging of vertical sections along cliff-face outcrops a few metres high adjacent to the present-day shoreline. Combined with OSL and AMS age determinations, these data provide evidence of three successive Weichselian sequences, each represented by the deposition of till followed by the accumulation of shallow marine deposits. Contrary to earlier conclusions, this study demonstrates that the area was occupied by a Late Weichselian glacier (LWG), although the LWG till is thin and discontinuous. Interstadial sublittoral sand related to the Mid-Weichselian interstadial was dated to 38–40 kyr, and an Early Weichselian interstadial to 76–80 kyr. The preservation of older sediments, multiple striae generations and abundant observations of weathered local bedrock material indicate weak glacial erosion within the study area. We suggest that the Late Weichselian glacier was relatively inactive and remained mainly cold-based until the deglaciation. The Isvika sections can be considered a new key site that offers further potential to improve our understanding of the Weichselian stage within the northwestern sector of the Barents–Kara Ice Sheet.  相似文献   

4.
Stratigraphical investigations of an inter-till peat in Brumunddal suggest a major interstadial of Early Weichselian age. The insect fauna and the pollen composition indicate a mean July temperature 2–3C lower than today during the climatic optimum. Larch and spruce immigrated at the end of the interstadial, which is tentatively correlated to the Jamtland Interstadial.  相似文献   

5.
All Known sites with fossils and ‘non-till sediments’ of possible Early and Middle Weichselian age in Norway are discussed. Along the west coast there are many sites marine shells which have been dated by means of radiocarbon, amino acids and thorium/uranium methods. Some sites are also correlated by means of underlying Eemian sequences. A tentative glaciation curve for western Norway indicates a first glacial advance soon after the end of the Eemian. There are indications of another re-advance around 40,000 B.P., and the Late Weichselian maximum (maxima?) occurred somewhere between 30,000 B.P. and 13,000 B.P. Parts of the coast may have been ice-free for most of the remaining periods. From the central parts of the country are known bones (e.g. mammoth), glaciolacustrine and fluvial sediments, peat, etc. The newly discovered site with peat of Brumunddal can very probably be correlated with the Jämtland Interstadial in Sweden, and the Brørup Interstadial in Denmark. If this is correct, nearly the whole of southern Scandinavia must have been deglaciated during the interstadial.  相似文献   

6.
The Late Quaternary ( c . 130,000–10,000 BP) glacial history of the central west coast of Jameson Land, East Greenland, is reconstructed through glacial stratigraphical studies. Seven major sedimentary units are described and defined. They represent two interglacial events (where one is the Holocene). one interstadial event and two glacial events. The older interglacial event comprises marine and fluvial sediments, and is correlated to the Langelandselv interglacial, corresponding to oxygen isotope sub-stage 5e. It is followed by an Early Weichselian major glaciation during the Aucellaelv stade, and subsequently by an Early Weichselian interstadial marine and deltaic event (the Hugin Sø interstade). Sediments relating to the Middle Weichselian have not been recognized in the area. The Hugin Sø interstade deposits have been overrun by a Late Weichselian ice advance, during the Flakkerhuk stade, when the glacier, which probably was a thin, low gradient fjord glacier in Scoresby Sund, draped older sediments and landforms with a thin till. Subsequent to the final deglaciation, some time before 10,000BP, the sea reached the marine limit around 70 m a.s.l., and early Holocene marine, fluvial and littoral sediments were deposited in the coastal areas.  相似文献   

7.
Till beds and waterlain sediments from at least 3 stadials and 2 interstadials during the Weichsel glaciation are recorded on Finnmarksvidda. The oldest, possibly Weichselian, ice-free period recorded on Finnmarksvidda is represented in one river section and is preliminary named the Vuolgamasjåkka thermomer. Its initiation is TL-dated to about 120 ka, which indicates a pre-Weichselian, possibly Eemian age. The interstadial which follows the subsequent and assumed oldest Weichsel stadial on Finnmarksvidda, the Eiravarri interstaeial, has previously been tentatively correlated lithostratigtrahically with the Peräpohojola interstadial ( sensu stricto ) in North Finland. The youngest interstadial, the Sargejåk internatiodial , is in this paper suggested to correlate with the Tärändö interstadial in North Sweden. The initial Weichselian ice movement across Finnmarksvidda is so far unknown, but locally N of Kautokeino in the W the initial (recorded) ice movement was directed towards NW-N. The regional ice movements for the two subsequent stadials on Finnmarksvidda were initially directed towards NE-ene and NNW, respectively.  相似文献   

8.
Sejrup, Hans Petter 1987 03 01: Molluscan and foraminiferal biostratigraphy of an Eemian-Early Weichselian section on Karmøy, southwestern Norway. Boreas , Vol. 16, pp. 27–42. Oslo. ISSN 0300–9483.
At Karmøy, southwestern Norway, a section with marine sediments from the last interglacial (the Avaldsnes Interglacial) and from two ice-free periods (the Torvastad and Bø Interstadial) in the Weichselian have been examined for molluscs and foraminifera. The following conclusions concerning the depositional environments of these sediments can be drawn: (1) The Avaldsnes Interglacial was a high-energy environment with a sea level 20 to 50 m higher than at present, regressing towards the end of the interglacial. Sea temperatures were as in the area today or slightly warmer. (2) During the Torvastad Interstadial (71–85 ka) the sea level was between 0 and c . 20 m higher than at present, and sea temperatures were as between Svalbard and northern Norway today. (3) The Bø Interstadial (40–64 ka) shows a complete interstadial cycle, with changing sea level and temperatures. Its optimum was close to the conditions prevailing in North Norway today or slightly colder. By comparison with other sites, a total of at least four interstadial episodes through the Weichselian in southwestern Norway is proposed. These date to c . 30 ka, 40–64 ka, 71–85 ka and 87–101 ka. The episodes and the glacial advances between them do not directly correlate with published interpretations of changes in surface circulation in the Norwegian Sea through the Weichselian. It is suggested that the nourishment of the southern part of the Scandinavian ice sheet might be more related to sea surface conditions in the North Atlantic than to those of the Norwegian Sea.  相似文献   

9.
The Quaternary stratigraphy in Finland is discussed on the basis of an example from the Oulainen area of Ostrobothnia. Organogenic deposits found beneath till at this site are correlated with the Eemian Interglacial on biostratigraphical evidence. This is confirmed by TL dates of 97,000 ± 18,000 B.P. and 150,000 ± 30,000 B.P., whereas a finite radiocarbon date of 63,200 +5500 -3200 B.P. is probably too young. Correlation of the Weichselian stratigraphy is based on deep-sea oxygen isotope data, in which the variations in isotope ratios are assumed to reflect global changes in climate and fluctuations in the volume of the ice-caps. It is concluded on the latter grounds that Finland must have been free of ice at two periods during the Early Weichselian but at least for the most part covered by ice thereafter up to the final deglaciation. The sediments attributed to the only known Weichselian interstadial in Finland, the Perapohjola Interstadial, are taken to correspond most probably to the Brørup, although some may represent the Odderade, Information on the Weichselian till stratigraphy in the Oulainen area is largely confined to the deglaciation phase, the relatively complex nature of which suggests that complete reconstruction of the earlier phases of the Weichselian in an area such as Finland, located towards the centre of the ice sheet, is scarcely feasible by the methods currently available.  相似文献   

10.
The Veikimoraines in northernmost Sweden display a very conspicuous distribution pattern, sharply demarcated to the east and successively decreasing to the south, west and north. The sharp demarcation to the east is thought to reflect the front of a stagnant ice sheet. The downwasting of this glacier was retarded by the insulation of a thick superglacial debris cover and subarctic vegetation invaded at least parts of the slowly collapsing ice. Radiocarbon datings of organic matter deposited in connection with the formation of the Veiki moraine, lithostratigraphical evidence and the relation to other glacial features prove the Veiki moraine landscape to date from the deg laciation of the first Weichselian ice sheet, i.e. the Peräpohjola Interstadial. The good preservation of the features implies that in extensive areas of northern sweden the Early Weichselian glacial landscape escaped significant erosion despite being overrun by two later glaciers. Previous interpretations of the Late Weichselian/Holocene deglaciation are largely based on an Early Weichselian deglaciation pattern.  相似文献   

11.
The Saalian sequence of Belchatów, central Poland, is exceptionally thick and complete. Five tills, two from the older Saalian (Odranian, Drenthe) and three from the younger Saalian (Wartanian, Warthe), which are separated by the fluvial Chojny Formation, have been identified. The Saalian sequence at Be?chatów is underlain by Holsteinian and overlain by Eemian sequences, both palaeobotanically analysed. The Chojny Formation contains deposits of meandering (lower member) and braided (upper member) rivers, with occasional aeolian deposits. The lower member of the formation contains numerous organic layers. Pollen analysis indicates temperate (sub-boreal) to cold (sub-arctic) climatic conditions, with coniferous to mixed forests in the optimum phase of the interstadial. The interstadial floras of the Chojny Formation are interpreted as representing the intra-Saalian Pilica Interstadial. Profiles from Belchatów are designated as the stratotype profiles of this substage. The data from Be?chatów show clearly that reforestation occurred between the major advances of the Saalian ice sheet, although only interstadial rank, not interglacial, may be inferred from the pollen data.  相似文献   

12.
A brief summary is given of the present state of knowledge about the Weichselian glaciations and interstadials in sweden. The following stages are discussed: (1) The first Weichselian glaciation (W1). This glaciation has not been identified. Probably only northern Sweden was ice-covered. (2) The Jämtland Interstadial , dated at > 50,000 B.P. and correlated with the Finnish Peräpohjola and the Danish Brörup Interstadials. - (3) The second Weichselian glaciation (W II). There are several uncertainteis concerning this glaciation. Sweden was probably ice-covered down to the latitude of Stockholm. – (4) A Middle Weichsedlian interstadial , or complex of interstadials. Some radiocarbon dates indicate, although very uncertain, that most of Sweden may have been free of ice some time rather well known. – Some main problems which have to be investigated are also identified.  相似文献   

13.
Examination of a 10 m piston core from the eastern Kattegat revealed marine sediments spanning a period from the late Middle Weichselian to the Early Holocene. The oldest marine unit in the core is 14C-dated to about 30,000–36,000 years BP. These sediments represent the Middle Weichselian Sandnes/Denekamp-Hengelo Interstadial (upper part of stable isotope stage 3) and can be correlated to marine deposits from several localities in the Kattegat region by means of foraminifera. The Late Weichselian deposits comprise sediments from the Oldest Dryas Stadial and the Allerød Interstadial. The intervening periods are not represented in the sequence (hiatuses). Sediments from the latest part of the Early Holocene Preboreal period succeeding the Allerod sequence indicate a considerable hiatus spanning 2000–3000 years around the Weichselian/Holocene boundary. The late Preboreal faunas document a high freshwater inflow during this period, and stable conditions seem not to have been reached in the area until a few hundred years later, in the Boreal period. Comparison with boxcore material from the same site documents a reduction of the energy level of the bottom currents some time between c. 8000 and 800 years BP.  相似文献   

14.
Alexanderson, H., Johnsen, T. & Murray, A. S. 2009: Re‐dating the Pilgrimstad Interstadial with OSL: a warmer climate and a smaller ice sheet during the Swedish Middle Weichselian (MIS 3)? Boreas, 10.1111/j.1502‐3885.2009.00130.x. ISSN 0300‐9483. Pilgrimstad in central Sweden is an important locality for reconstructing environmental changes during the last glacial period (the Weichselian). Its central location has implications for the Scandinavian Ice Sheet as a whole. The site has been assigned an Early Weichselian age (marine isotope stage (MIS) 5 a/c; >74 ka), based on pollen stratigraphic correlations with type sections in continental Europe, but the few absolute dating attempts so far have given uncertain results. We re‐excavated the site and collected 10 samples for optically stimulated luminescence (OSL) dating from mineral‐ and organic‐rich sediments within the new Pilgrimstad section. Single aliquots of quartz were analysed using a post‐IR blue single aliquot regenerative‐dose (SAR) protocol. Dose recovery tests were satisfactory and OSL ages are internally consistent. All, except one from an underlying unit that is older, lie in the range 52–36 ka, which places the interstadial sediments in the Middle Weichselian (MIS 3); this is compatible with existing radiocarbon ages, including two measured with accelerator mass spectrometry (AMS). The mean of the OSL ages is 44±6 ka (n=9). The OSL ages cannot be assigned to the Early Weichselian for all reasonable adjustments to water content estimates and other parameters. The new ages suggest that climate was relatively mild and that the Scandinavian Ice Sheet was absent or restricted to the mountains for at least parts of MIS 3. These results are supported by other recent studies completed in Fennoscandia.  相似文献   

15.
Coastal Jameson Land is characterized by thick Quaternary deposits from the last interglacial/glacial cycle. The successions at the mouth of Langelandselv exhibit a key stratigraphy where sediments from the Langelandselv interglaciation (Eemian) are overlain by three till units interbedded with glacimarine and deltaic interstadial successions. Immediately after the retreat of glaciers after the extensive Scoresby Sund glaciation (Saalian). advection of warm Atlantic surface water surpassed what is known from the Holocene. The two lowermost Weichselian tills, deposited during the Aucellaelv and Jyllandselv stades (Early Weichselian), reflect short-lasting readvances of fjord glaciers. Luminescence dates and correlation with adjacent areas suggest ages of 110–80 ka and 70–60 ka for the Hugin Sø and the Møselv interstades, respectively.  相似文献   

16.
A 2 m thick laminated lacustrine deposit of silt and clay recovered from the high-latitudinal site at Sokli (northern Finland) provides a unique mid-Weichselian fossil record for Fennoscandia. High-resolution botanical and zoological analyses of the lacustrine deposit allow detailed reconstruction of the regional vegetational development and of the history of the lake and the wetland ecosystem within the Sokli basin during the early part of the Weichselian Middle Pleniglacial (=equivalent to Marine Isotope Stage (MIS) 3). The inferred terrestrial vegetation represented by the Sokli MIS 3 sequence (so-called Tulppio Interstadial) was probably low-arctic tundra, treeless but with shrub elements including juniper, willow, dwarf birch, ericoids, lycopods and a rich herb flora with a variety of arctic–alpine taxa and heliophilous, pioneer elements. The presence of herbs such as Rubus chamaemorus, Epilobium palustre, Potentilla palustris and Sphagnum, Drepanocladus and other mosses suggests that the lake was fringed by wet meadows and peatlands or peaty telmatic communities. The distributional ranges of pine and tree birch were probably only a few hundred kilometres south or southeast of Sokli. This is concordant with evidence for the presence of boreal tree taxa during the MIS 3 in the Baltic countries and further east in Europe, but contradicts with the commonly inferred treeless tundra or grass-dominated steppe conditions in central Europe.  相似文献   

17.
The landscape evolution of the Mepal area from Late Devensian Block Fen Terrace times to the beginning of the Flandrian, a period of ca. 8000 radiocarbon years, is reconstructed. Stratigraphy is based on borehole transects and single boreholes, centred on a depression between the Block Fen Terrace and the Isle of Ely. Within the depression is a Devensian late‐glacial sequence, with the Windermere Interstadial represented by radiocarbon‐dated organic sediments. Pollen and plant macroscopic remains of the late‐glacial sediments are analysed. Plant communities with Betula developed in the interstadial. Before and after the interstadial there is much reworked pollen in the inorganic sediments, derived from local pre‐Devensian Pleistocene sediments, including temperate Ipswichian Stage sediments, and from mass‐wasting of the local Jurassic bedrock. Periods of such mass‐movement occur before and after the deposition of the late‐glacial lake sediments. Deposition of aeolian sediment occurs later than the main period of mass movement, but before the Windermere Interstadial. The relationship of the aeolian sediments in time and space to permafrost, indicated by local contraction polygons and cracks, is discussed. Solifluction diverted the flow of the River Great Ouse from a northeast direction in Block Fen Terrace times to a southwest direction as a channel developed to the west of the Chatteris–March ‘island’. This led to a drainage divide in Flandrian times. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

18.
An inter-till organic sediment, probably a paleosol, was found in a ridge in the Setesdal Valley. A radiocarbon date on the fraction soluble in NaOH gave a finite age of 35,850 B.P., which is probably a minimum age as contamination of younger carbon might have occurred. Pollen analysis indicates that the sediment has originated above the tree-limit. Compared with different interglacial and interstadial deposits in Scandinavia, the sediment is interpreted as representing an interstadial period, tentatively named the Vatnedal interstadial, of Early or Middle Weichselian age.  相似文献   

19.
The glacial history of the Fennoscandian ice cap beyond some 20,000 years B.P. is fairly poorly known because of the absence of a reliable dating control. The Eemian Interglacial of Europe is not dated at all. The Weichselian Glaciation seems to be characterized by three main glaciation maxima separated by two main interstadial periods (of quite different conditions). The Grande Pile continuous lake sequence offers a uniquely detailed paleoclimatic and paleomagnetic record of the last 130,000 years. There are obvious correlations between the Grande Pile record, the Dutch palynological records and the Fennoscandian glacial records.  相似文献   

20.
Four geologic units previously mapped in southern Jameson Land. East Greenland (Funder 1978, 1990) are identifiable on a false colour composite of Landsat Thematic Mapper (TM) spectral hands TM5. TM4 and TM1. The area covered by the Weichselian glaciations has a fresh glacial morphology and a less developed drainage system than the older landscape. The Weichselian glaciers reached more than 200 m a.s.l. in the west. but only about 100 m a.s.l. in the east. A contextual analysis (local frequency and local orientation) was included in a Maximum Likelihood classification (M-L) to map the extent of the Weichselian glaciations. Deposits correlated with the Saalian Scoreshy Sund glaciation are found on the central plateaux of Jameson Land. Landsat TM geological mapping of the surficial distribution of deposits from the Scoreshy Sund glaciation and of weathered Jurassic sandstone or deposits with a high percentage of such sandstone was done using a supervised Maximum Likelihood procedure. Except for the mapping of thc extent of the Late Weichselian Flakkerhuk glaciation, the Maximum Likelihood boundaries between units are in general agrecnient with earlier mapping or with the visual interpretation of the false colour composite. A strong vegetational influence. and similar spectral reflectance lrom deposits of different age due to similarities in lithological composition reduced the possibility of an independent remote sensing approach. Taking already existing general geological knowledge and chronology into account allowed successful Landsat TM geological mapping.  相似文献   

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