Maximum extent of the Eurasian ice sheets in the Barents and Kara Sea region during the Weichselian   总被引：1，自引：0，他引：1  

JOHN INGE SVENDSEN  VALERY I. ASTAKHOV  DMITRI YU. BOLSHIYANOV  IGOR DEMIDOV  JULIAN A. DOWDESWELL  VALERY GATAULLIN  CHRISTIAN HJORT  HANS W. HUBBERTEN  EILIV LARSEN  JAN MANGERUD  MARTIN MELLES  PER MÖLLER  MATTI SAARNISTO  MARTIN J. SIEGERT 《Boreas: An International Journal of Quaternary Research》1999,28(1):234-242

Based on field investigations in northern Russia and interpretation of offshore seismic data, we have made a preliminary reconstruction of the maximum ice-sheet extent in the Barents and Kara Sea region during the Early/Middle Weichselian and the Late Weichselian. Our investigations indicate that the Barents and Kara ice sheets attained their maximum Weichselian positions in northern Russia prior to 50 000 yr BP, whereas the northeastern flank of the Scandinavian Ice Sheet advanced to a maximum position shortly after 17 000 calendar years ago. During the Late Weichselian (25 000-10 000 yr BP), much of the Russian Arctic remained ice-free. According to our reconstruction, the extent of the ice sheets in the Barents and Kara Sea region during the Late Weichselian glacial maximum was less than half that of the maximum model which, up to now, has been widely used as a boundary condition for testing and refining General Circulation Models (GCMs). Preliminary numerical-modelling experiments predict Late Weichselian ice sheets which are larger than the ice extent implied for the Kara Sea region from dated geological evidence, suggesting very low precipitation.  相似文献   

Early Holocene shore-displacement in southern central Sweden as recorded in elevated isolated basins   总被引：1，自引：0，他引：1  

ANNA HEDENSTRÖM  JAN RISBERG 《Boreas: An International Journal of Quaternary Research》1999,28(4):490-504

Sediment cores from seven basins in two regions, the SÖdertÖrn peninsula and central Närke in southern central Sweden, were subject to diatom analysis and radiocarbon dating of the isolation events. In the former area, the compiled shore-displacement curve covers the time period from the deglaciation to 5700 BP. The latter area is covered from 8200 to 6500 BP. The chronology is based on combined macrofossil and bulk ages with an acknowledged correction. The most elevated sedimentary basin on the SÖdertÖrn peninsula was isolated at the end of the brackish water phase of the Yoldia Sea. During the Ancylus Lake stage of the Baltic, one minor ingression is recorded in the same area. The end of the Ancylus Lake is dated to c. 8200 BP on the SÖdertÖrn peninsula and to c. 8100 BP in central Närke. There was an interval of c. 1000 ¹⁴C years when brackish water prevailed in central eastern Sweden. Mastogloia is a typical diatom genus for that period. The onset of the brackish-marine Litorina Sea is dated to c. 7000 BP in central Närke. The amplitude for the early Litorina Sea transgression (L 1) did not exceed 2 m. L 1 is recorded 2–3 m higher in central Närke compared to the SÖdertÖrn peninsula, i.e. the former area has experienced a more intense isostatic uplift since 6500 BP.  相似文献   

The Fossvogur marine sediments in SW Iceland - confined to the Allerød/Younger Dryas transition by AMS 14 C dating     

ÁRNÝ E. SVEINBJÖRNSOTTIR  JÓN EIRÍKSSON  ÁSLAUG GEIRSDÓTTIR  JAN HEINEMEIER  NIELS RUD 《Boreas: An International Journal of Quaternary Research》1993,22(2):147-157

An exhaustive ¹⁴C dating programme of molluscs from the Fossvogur sediments in Reykjavik. Iceland is presented. For the first time all the fossiliferous units of the sediments are dated. The results confirm earlier conclusions of a widespread occurrence of marine sediments of Allerød age in Reykjavik. The set of dates from the Fossvogur sediments shows a narrow ¹⁴C age distribution (standard deviation of ±235 years) of molluscs from all localities and from successive marine units in vertical sections. The weighted mean conventional ¹⁴C age is 11,400 BP. Assuming a reservoir effect of 400 years. this corresponds to a reservoir-corrected age of I1,000 BP. i.e. the Allerød- Younger Dryas transition for the sampled units, These new ¹⁴C dates from Fossvogur confirm the need for a revision of the Upper Pleistocene chronology of the Reykjavik region. They also have a bearing on the Late Weichselian record of glacier readvances and sea-level changes in the area. The dates suggest that the marine units in Fossvogur accumulated within a restricted time-span of a few hundred years. The sediments in Fossvogur are of volcaniclastic origin and are extremely lithified, indicating local geothermal activity soon after their deposition. This may explain anomalously high D/L amino acid ratios measured in molluscs from the Fossvogur sediments. δ¹³C and δ¹⁸O results suggest that temperatures may have ranged up to 60°C.  相似文献   

Late Holocene glacier variations and climate at Jan Mayen     

EINAR ANDA  OLAV ORHEIM  JAN MANGERUD 《Polar research》1985,3(2):129-140

Jan Mayen is a small (373 km²) remote island in the Norwegian Sea. One third of it is covered by glaciers, all located on the Beerenberg volcano. There have been at least two Holocene periods of glacier expansion at Jan Mayen. The first may have taken place around 2500 B.P. Some glaciers had their maximum extent during the second period, around 1850 A.D. They have subsequently shown an oscillating retreat, with marked expansion around 1910, and with a minimum extent around 1950. Many glaciers advanced again around 1960. The advance of Sørbreen probably culminated around 1965. The climate appears to have been more arctic-continental than today during these two periods of glacier advances, caused by expanded pack ice cover in the East Greenland current and strong influence from the Greenland-Arctic high pressure area. The interplay between the high pressure area and the low pressure tracks in the North Atlantic Ocean determines the climate over the north-western part of the Atlantic, and this results in parallel climate and glacier variations within this region. We conclude, contrary to previous reports, that the advances of the glaciers around 1960 were caused by reduced summer temperatures and ablation, and not by increased precipitation.  相似文献   

Duration of ship-following by Kittiwakes Rissa tridactyla in the Barents Sea     

KJELL EINAR ERIKSTAD  JAN OVE BUSTNES  ODD JACOBSEN 《Polar research》1988,6(2):191-194

Ship-following Kittiwakes Rissa tridactyla were caught and dye-marked with picric acid on three occasions from a ship trawling in the Barents Sea in August 1986. The ship trawled regularly every 20-30 nautical miles and most of the trawl contents were fed to the birds accompanying the ship. Kittiwakes followed the ship for an average of 480-591 min. Between trawl-stations the birds rested on lifeboats and on the rail of the ship, and resting birds showed aggressive behaviour towards neighbours and intruders. The mean departure rate ranged from 4.2 to 5.1% per hour, and the turnover rate was 32 hours. It is obvious that the Kittiwakes behaved opportunistically and had adapted to exploit the waste from the commercial fisheries in the area.  相似文献   

Weichselian stratigraphy and palaeoenvironments at Bellsund, western Svalbard   总被引：1，自引：0，他引：1  

JON Y. LANDVIK  MAGNE BOLSTAD  ANNE KATRINE LYCKE  JAN MANGERUD  HANS PETTER SEJRUP 《Boreas: An International Journal of Quaternary Research》1992,21(4):335-358

A coastal cliff facing the ocean at the west coast of Spitsbergen has been studied, and seven formations of Weichselian and Holocene age have been identified. A reconstruction of the palaeoenvironment and glacial history shows that most of the sediments cover isotope stage 5. From the base of the section, the formation 1 and 2 tills show a regional glaciation that reached the continental shelf shortly after the Eemian. Formation 3 consists of glacimarine to marine sediments dated to 105,000–90,000 BP. Amino acid diagenesis indicates that they were deposited during a c . 10,000-year period of continuous isostatic depression, which indicates contemporaneous glacial loading in the Barents Sea. Foraminifera and molluscs show influx of Atlantic water masses along the west coast of Svalbard at the same time. Local glaciers advanced during the latter part of this period, probably due to the penetration of moist air masses, and deposited formation 4. A widespread weathering horizon shows that the glacial retreat was succeeded by subaerial conditions during the Middle Weichselian. Formation 5 is a till deposited during the Late Weichselian glacial maximum in this area. The glaciation was dominated by ice streams from a dome over southern Spitsbergen, and the last deglaciation of the outer coast is dated to 13,000 BP. A correlation of the events with other areas on Svalbard is discussed, and at least two periods of glaciation in the Barents Sea during the Weichselian are suggested.  相似文献   

Precise 14C ages of the Vedde and Saksunarvatn ashes and the Younger Dryas boundaries from western Norway and their comparison with the Greenland Ice Core (GICC05) chronology     

ØYSTEIN S. LOHNE  JAN MANGERUD  HILARY H. BIRKS 《第四纪科学杂志》2013,28(5):490-500

  相似文献   

Soft-bedded subglacial meltwater channel from the Welzow-Süd opencast lignite mine, Lower Lusatia, eastern Germany     

JAN A. PIOTROWSKI  JÖRN GELETNEKY  RALF VATER 《Boreas: An International Journal of Quaternary Research》1999,28(3):363-374

An excellent section in the Welzow-Süd open-cast lignite mine in Lower Lusatia, eastern Germany, provided a rare opportunity to study a small (5 m deep), buried subglacial meltwater channel of Saalian age. The channel is steep-sided and distinctly U-shaped. It is separated from undeformed outwash deposits in which it is incised by a sharp erosional contact and it is filled with meltwater sand and till. The till was possibly squeezed into the channel from the adjacent ice/bed interface. Directly beneath the channel, there is a partly truncated diapir of clayey silt, evidencing sediment intrusion into the channel from below. During channel formation, the pressure gradient was oriented from the surrounding sediments into the channel, so that the channel served as a drainage conduit for groundwater from the adjacent subglacial aquifer. The substratum consists largely of sandy aquifers with a total thickness of about 100 m, separated by two aquitards. Channel formation was initiated when hydraulic transmissivity of the bed did not suffice to evacuate all the subglacial meltwater as groundwater flow. As the Welzow-Süd channel belongs to a dense network of subglacial channels in eastern Germany, temporary ice-sheet instability in this region prior to channel formation seems possible.  相似文献   

Early Holocene drowned lagoonal deposits from the Kattegat, southern Scandinavia     

OLE BENNIKE  JØRN BO JENSEN  PETER B. KONRADI  WOLFRAM LEMKE  JAN HEINEMEIER 《Boreas: An International Journal of Quaternary Research》2000,29(4):272-286

Shallow seismic profiling indicated the presence of a drowned lagoon-barrier system formed during the transgression of the southern Kattegat, and investigations of core material have confirmed this. Studies of plant and animal macrofossils show that the lagoonal sediments contain a mixture of marine, brackish, lacustrine, telmatic and terrestrial taxa, and analyses of foraminifers indicate brackish-water conditions. Low oxygen isotope values obtained on shells of marine molluscs also point to lowered salinity. The lagoonal sediments are situated at depths between 24 and 35 m below present sea level. They are dated to between c. 10.5 cal. ka BP and c. 9.5 cal. ka BP, and reflect a period characterized by a moderate relative sea level rise. The lagoonal sediments are underlain by lateglacial glaciomarine clay and silt, which are separated from the Holocene deposits by an unconformity. The earliest Holocene sediments consist of littoral sand with gravel, stones and shells; these sediments were formed during the transgression of the area before the barrier island-lagoon system was developed. The lagoonal sediments are overlain by mud, which contains animal remains that indicate increasing water depths.  相似文献   

LICHENOMETRIC AGES OF THE LITTLE ICE AGE MORAINES ON KING GEORGE ISLAND AND OF THE LAST VOLCANIC ACTIVITY ON PENGUIN ISLAND (WEST ANTARCTICA)     

PIOTR JAN ANGIEL  MACIEJ DĄBSKI 《Geografiska Annaler: Series A, Physical Geography》2012,94(3):395-412

The recently observed recession of glaciers on King George Island is associated with decades of climate warming in the Antarctic Peninsula region. However, with only 60 years of glaciological observations in the study area ages of the oldest moraines are still uncertain. The goal of the study was to estimate ages of lichen colonization on the oldest moraines of the Ecology and White Eagle Glaciers on King George Island and on the Principal Cone of Penguin Island volcano. The first lichenometric studies on these islands from the late 1970s used rates that had about four to five times slower Rhizocarpon growth rates. We re‐examined the sites and measured 996 thalli diameters to establish the surface ages. To estimate the age we used (1) long‐term Rhizocarpon lichen group growth rates established by authors using data from a previous lichenometric study on King George Island, and (2) previous data of lichen growth rates from other sub‐Antarctic islands. Our results suggest growth rates between 0.5 and 0.8 mm yr^–1. According to these rates the ages of the oldest moraine ridges are of the Little Ice Age and were colonized at the beginning of the twentieth century. The mid‐twentieth century age of lichen colonization on the historically active Penguin Island volcano might support the date of the last eruption reported by whalers in the end of the nineteenth and the beginning of the twentieth century.  相似文献