| 1. |
- Hammarlund, Dan, et al.
(författare)
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Climate and environment during the Younger Dryas (GS-1) as reflected by composite stable isotope records of lacustrine carbonates at Torreberga, southern Sweden
- 1999
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Ingår i: Journal of Quaternary Science. - 1099-1417. ; 14:1, s. 17-28
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Tidskriftsartikel (refereegranskat)abstract
- Climatic and environmental changes during the Younger Dryas stadial (GS-1) and preceding and following transitions are inferred from stable carbon and oxygen isotope records obtained from the sediments of ancient Lake Torreberga, southern Sweden. Event GS-1 is represented in the sediment sequence by 3.5 m of clay containing lacustrine carbonates of various origins. Comparison of isotopic records obtained on mollusc shells, ostracod valves, and Chara encrustations precipitated during specific seasons of the year supports estimates of relative changes in both lake water and mean annual air temperatures. Variations in soil erosion rates can also be estimated from a simple isotope-mass-balance model to separate allochthonous and autochthonous carbonate contributions to the bulk carbonate content of the sediments. The well-known, rapid climatic shifts characterising the Last Termination in the North Atlantic region are clearly reflected in the isotopic data, as well as longer-term changes within GS-1. Following maximum cooling shortly after the Allerod-Younger Dryas (GI-1-GS-1) transition, a progressive warming and a slight increase in aquatic productivity is indicated. At the Younger Dryas-Preboreal (GS-1-PB) transition mean annual air temperature rapidly increased by more than 5 degrees C and summer lake-water temperature increased by ca. 12 degrees C. The subsequent Preboreal oscillation is characterised by an increase in soil erosion and a slight decrease in mean annual air temperature. These results are in harmony with recent findings about large-scale climate dynamics during the Last Termination. Copyright (C) 1999 John Wiley & Sons, Ltd.
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| 2. |
- Sandgren, Per, et al.
(författare)
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Stratigraphic evidence for a high marine shore-line during the Late Weichselian deglaciation on the Kullen Peninsula, southern Sweden
- 1999
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Ingår i: Journal of Quaternary Science. - 1099-1417. ; 14:3, s. 223-237
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Tidskriftsartikel (refereegranskat)abstract
- Mineral magnetic properties and the carbon content of a sediment sequence in Lake Kullatorpssjon on the Kullen Peninsula in northwest Scania, southern Sweden, were investigated. Diatom and ostracod analyses were undertaken for palaeoecological reconstruction and a chronology was constructed from accelerator mass spectrometry (AMS) radiocarbon dating of terrestrial plant remains and mosses. Five stratigraphical units were identified (units 1-5, from oldest to youngest). The two lowermost units consist of clay. The lowest clay unit (1) is strikingly black, 2 m thick and has magnetic properties dominated by high concentrations of authigenic greigite (Fe3S4). In contrast, the overlying clay unit (2) is grey, 1.18 m thick and has magnetic properties dominated by low concentrations of detrital magnetite (Fe3O4). A major palaeoecological change is reflected in the diatom flora and ostracod fauna at the transition from unit 1 to unit 2. The sediment stratigraphy, geochemical, mineral magnetic and palaeoecological analyses also point to a significant change in depositional environment at this transition, which is proposed to represent the isolation of Lake Kullatorpssjon from the Kattegat Sea. Earlier investigations have determined the marine limit to ca. 65 m a.s.l. on the Kullen Peninsula. The separate independent lines of evidence presented here, however, suggest that the Late Weichselian marine limit developed at 85-90 m a.s.l. at the deglaciation ca. 17 200 cal. yr BP (ca. 14 500 yr BP). This limit is ca. 25 m higher than assumed previously. Lake Kullatorpssjon formed ca. 1000 cal. yr later when the basin became isolated from the Kattegat Sea. Copyright (C) 1999 John Wiley & Sons, Ltd.
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| 3. |
- Hjort, Christian, et al.
(författare)
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Holocene glacial history and sea level changes on James Ross Island, Antarctic Peninsula
- 1997
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Ingår i: Journal of Quaternary Science. - 1099-1417. ; 12:4, s. 259-273
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Tidskriftsartikel (refereegranskat)abstract
- A reconstruction of deglaciation and associated sea-level changes on northern James Ross Island, Antarctic Peninsula, based on lithostratigraphical and geomorphological studies, shows that the initial deglaciation of presently ice-free areas occurred slightly before 7400 14C yr BP. Sea-level in connection with the deglaciation was around 30 m a.s.l. A glacier readvance in Brandy Bay, of at least 7 km, with the initial 3 km over land, reached a position off the present coast at ca. 4600 yr BP. The culmination of the advance was of short duration, and by 4300 yr BP the coastal lowlands again were ice-free. A distinct marine level at 16–18 m a.s.l. was contemporaneous with or slightly post-dates the Brandy Bay advance, thus indicating the relative sea-level around 4600–4500 yr BP. Our results from James Ross Island confirm that over large areas in this part of Antarctica the last deglaciation occurred late.
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| 4. |
- Andrén, Thomas, et al.
(författare)
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Correlation of Swedish glacial varves with the Greenland (GRIP) oxygen isotope record
- 1999
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Ingår i: Journal of Quaternary Science. - 0267-8179 .- 1099-1417. ; 14:4, s. 361-371
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Tidskriftsartikel (refereegranskat)abstract
- A mean varve thickness curve has been constructed for a part of the Swedish varve chronology from the northwestern Baltic proper. The mean varve thickness curve has been correlated with the delta(18)O record from the GRIP ice-core using the Younger Dryas-Preboreal climate shift. This climate shift was defined by pollen analyses. The Scandinavian ice-sheet responded to a warming at the end of the Younger Dryas, ca. 10 995 to 10 700 clay-varve yr BP. Warming is recorded as a sequence of increasing mean varve thickness and ice-rafted debris suggesting intense calving of the ice front. The Younger Dryas-Preboreal climatic shift is dated to ca. 10 650 clay-varve yr BP, about 40 yr after the final drainage of the Baltic Ice Lake. Both the pollen spectra and a drastic increase in varve thickness reflect this climatic shift. A climate deterioration, correlated with the Preboreal oscillation, is dated to ca. 10 440 to 10 320 clay-varve yr BP and coincides with the brackish water phase of the Yoldia Sea stage. The ages of the climatic oscillations at the Younger Dryas-Preboreal transition show an 875 yr discrepancy compared with the GRIP record, suggesting a large error in the Swedish varve chronology in the part younger than ca. 10 300 clay-varve yr BP.
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| 5. |
- Coope, G.R., et al.
(författare)
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Temperature gradients in northern Europe during the last glacial-Holocene transition (14-9 14C kyr BP) interpreted from coleopteran assemblages.
- 1998
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Ingår i: Journal of Quaternary Science. - 0267-8179 .- 1099-1417. ; 13:5, s. 419-433
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Tidskriftsartikel (refereegranskat)abstract
- Late-glacial and early Holocene climatic conditions have been reconstructed for northern Europe using the mutual climatic range (MCR) palaeoclimate method based on fossil coleopteran assemblages. Altogether, beetle faunas from 77 sites have been analysed ranging from Ireland in the west to Poland and Finland in the east, and MCR estimates calculated. The results are plotted on 16 maps, each representative of a selected time-slice covering the period from 14.5 C-14 kyr BP to 9.0 C-14 kyr BP. Eight of the maps show the MCR estimates of T-max (mean temperature of the warmest month) derived from each site for which data are available, while the remainder show estimated T-max isotherms interpolated from these values. It can be demonstrated that at times the thermal climate was fairly uniform throughout the study area, whereas at others temperature gradients were much steeper than they are in the region today. There also appears to be a distinct contrast between cold periods, when contours trended NW-SE, and warmer periods, when contours trend W-E or even NE-SW. The pattern of climatic changes that emerges is shown to be very different from the traditional view that has been used up to now as a template for classifying Late-glacial climatic events on a wide, even global, scale. The suddenness and intensity of changes in the thermal climate may have been partially responsible for an apparent lack of equilibrium between the flora and fauna of the time and the physical environment in which they lived.
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| 6. |
- Björck, S., et al.
(författare)
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An event stratigraphy for the Last Termination in the North Atlantic region based on the Greenland Ice-core record: a proposal by the INTIMATE group.
- 1998
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Ingår i: Journal of Quaternary Science. - 0267-8179 .- 1099-1417. ; 13:4, s. 283-292
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Tidskriftsartikel (refereegranskat)abstract
- It is suggested that the GRIP Greenland ice-core should constitute the stratotype for the Last Termination. Based on the oxygen isotope signal in that core, a new event stratigraphy spanning the time interval from ca. 22.0 to 11.5 k GRIP yr BP (ca. 19.0-10.0 k C-14 yr BP) is proposed for the North Atlantic region. This covers the period from the Last Glacial Maximum, through Termination 1 of the deep-ocean record, to the Pleistocene-Holocene boundary, and encompasses the Last Glacial Late-glacial of the traditional northwest European stratigraphy. The isotopic record for this period is divided into two stadial episodes, Greenland Stadials 1 (GS-1) and 2 (GS-2), and two interstadial events, Greenland Interstadials 1 (GI-1) and 2 (GI-2). In addition, GI-1 and GS-2 are further subdivided into shorter episodes. The event stratigraphy is equally applicable to ice-core, marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon-dated chronostratigraphy that has been used hitherto.
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| 7. |
- Witte, H.J.L., et al.
(författare)
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Regression coefficients of thermal gradients in northwestern Europe during the last glacial-Holocene transition using beetle MCR data.
- 1998
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Ingår i: Journal of Quaternary Science. - 0267-8179 .- 1099-1417. ; 13:5, s. 435-445
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Tidskriftsartikel (refereegranskat)abstract
- Palaeotemperature estimates obtained from 74 sites in northern Europe, and collectively spanning approximately the last 45 000 yr (radiocarbon time-scale), have been compiled as a major component of the EPECC project. The data presented here have been obtained using the mutual climatic range (MCR) method based on beetle assemblage data. The sites range across a transect from Ireland in the west to Poland and Finland in the east. Thermal gradients have been derived from the data using multiple linear regression. The regression models were solved for each of a series of 'time windows'. Each interval has a separate time-dependant trend, which was removed by detrending before solving the regression equations. The robustness and confidence intervals of the regression coefficients were estimated using the bootstrap method, with samples being selected from the data set by Monte Carlo simulation. The resulting palaeotemperature gradients were compared with modern temperature gradients over Europe. The data suggest that there were significant changes in the steepness of latitudinal temperature gradients over northern Europe during the past 45000 yr, although most attention in our compilations is focused on the last glacial-Holocene transition, the period for which the most abundant data are available so far. A significant delay in warming at the end of the last glacial stage in the northern part of the study area, by comparison with the southern sector, is also inferred. Reasons for these temporal and geographical variations and their possible palaeoclimatic implications are discussed.
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| 8. |
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| 9. |
- Adrielsson, Lena, et al.
(författare)
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Interactions between the Greenland Ice Sheet and the Liverpool Land coastal ice cap during the last two glaciation cycles
- 2005
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Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 20:3, s. 269-283
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Tidskriftsartikel (refereegranskat)abstract
- The sedimentary record from the Ugleelv Valley on central Jameson Land, East Greenland, adds new information about terrestrial palaeoenvironments and glaciations to the glacial history of the Scoresby Sund fjord area. A western extension of a coastal ice cap on Liverpool Land reached eastern Jameson Land during the early Scoresby Sund glaciation (approximate to the Saalian). During the following glacial maximum the Greenland Ice Sheet inundated the Jameson Land plateau from the west. The Weichselian also starts with an early phase of glacial advance from the Liverpool Land ice cap, while polar desert and ice-free conditions characterised the subsequent part of the Weichselian on the Jameson Land plateau. The two glaciation cycles show a repeated pattern of interaction between the Greenland Ice Sheet in the west and an ice cap on Liverpool Land in the east. Each cycle starts with extensive glacier growth in the coastal mountains followed by a decline of the coastal glaciation, a change to cold and arid climate and a late stage of maximum extent of the Greenland Ice Sheet.
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| 10. |
- Alexanderson, Helena, et al.
(författare)
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Depositional history of the North Taymyr ice-marginal zone, Siberia - a landsystem approach
- 2002
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Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 17:4, s. 361-382
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Tidskriftsartikel (refereegranskat)abstract
- The sediment-landform associations of the northern Taymyr Peninsula in Arctic Siberia tell a tale of ice sheets advancing from the Kara Sea shelf and inundating the peninsula, probably three times during the Weichselian. In each case the ice sheet had a margin frozen to its bed and an interior moving over a deforming bed. The North Taymyr ice-marginal zone (NTZ) comprises ice-marginal and supraglacial landsystems dominated by thrust-block moraines 2-3 km wide and large-scale deformation of sediments and ice. Large areas are still underlain by remnant glacier ice and a supraglacial landscape with numerous ice-walled lakes and kames is forming even today. The proglacial landsystem is characterised by subaqueous (e.g. deltas) or terrestrial (e.g. sandar) environments, depending on location/altitude and time of formation. Dating results (OSL, C-14) indicate that the NTZ was initiated ca. 80 kyr BP during the retreat of the Early Weichselian ice sheet and that it records the maximum limit of a Middle Weichselian glaciation (ca. 65 kyr BP). During both these events, proglacial lakes were dammed by the ice sheets. Part of the NTZ was occupied by a thin Late Weichselian ice sheet (20-12 kyr BP), resulting in subaerial proglacial drainage. Copyright (C) 2002 John Wiley Sons, Ltd.
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