| 1. |
- Möller, Per, et al.
(författare)
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Late Weichselian environmental history in southeastern Sweden during the deglaciation of the Scandinavian ice sheet
- 1987
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 28:1, s. 1-37
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Tidskriftsartikel (refereegranskat)abstract
- Late Weichselian litho-, bio-, and chronostratigraphy (14C and varves) in southeastern Sweden provide a detailed picture of the deglaciation pattern and dynamics, shore displacement, late-glacial sedimentation, and history of the landscape, vegetation, and climate. Two plausible glacial models were tested against lithologic, chronologic, and climatic data. Permafrost at and outside the ice margin and topographic conditions beneath the ice apparently caused inward spread of frozen glacier-bed conditions. This led to a buildup of a large zone of debris-rich basal ice. A climatic amelioration about 12,700 yr B.P. changed the temperature profile in the ice sheet. Deposition of basal melt-out till began at the previously frozen glacier bed, and a rapid recession of the clean ice set in; thin exposed debris-rich basal ice which was separated from the active ice margin about 150 yr later. In this zone of stagnant ice there followed a 200– 300-yr period marked by subglacial and supraglacial melt-out and resedimentation, forming a large hummocky/transverse moraine. The mild climate favored rapid plant immigration, and a park-tundra was established. The gradual closing of the landscape was interrupted by a 100- to 150-yr period of tundra vegetation and a cool, dry climate, with local vegetational differences caused by differences in soil moisture. About 12,000 yr B.P. a second climatic amelioration set in, and during the next 1000 yr a birch (and pine) woodland gradually developed. Soils stabilized and Empetrum heaths became abundant as the climate gradually deteriorated at the end of this period. By 11,000 yr B.P. the area had become a tundra again with scattered birch stands, dominated by herbs such as Artemisia, Chenopodiaceae, grasses, and sedges. Some 500 yr later a birch/pine woodland again succeeded, and within about 500 yr the vegetation changed to a rather closed woodland as the climate ameliorated further. However, the time lag between climatic and vegetation change was considerable.
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| 2. |
- Ahokangas, Elina Marita, et al.
(författare)
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Geophysical characterization of late-Quaternary glaciofluvial complex and glacial stratigraphy in the Satakunta sandstone area, Köyliö, southwest Finland
- 2021
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Ingår i: Quaternary Research. - : Cambridge University Press. - 0033-5894 .- 1096-0287. ; 100, s. 135-153
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Tidskriftsartikel (refereegranskat)abstract
- We acquired high-resolution reflection seismic data using a broadband digital-based landstreamer system to characterize a depression related to the Mesoproterozoic (Jothnian) Satakunta sandstone basin in the Köyliö study area, southwest Finland. This ca. 800-m-wide depression is infilled with up to 100-m-thick (late) Quaternary interlobate glaciofluvial complex sediments. The seismic images clearly reveal details of the glaciofluvial complex, sandstone depression topography, and brittle structures related to the formation of the sandstone basin by oblique transtension. Additionally, we identified the setting of a diabase laccolith within the sandstone and the geometry and position of the steep sandstone contact. The esker core does not follow the sandstone-Svecofennian basement rock contact or lean to it. The esker core is at a depth of 50–60 m on the flank of the depression. The seismic data image the esker core and other architectural elements of the esker. We highlight the potential of the digital-based landstreamer in the research of complex Quaternary sediments in major bedrock depressions including the characterization of the underlying bedrock properties. We also discuss the possible tunnel valley origin of the sandstone depression.
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| 3. |
- Blass, Alex, et al.
(författare)
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Decadal-scale autumn temperature reconstruction back to AD 1580 inferred from the varved sediments of Lake Silvaplana (southeastern Swiss Alps)
- 2007
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Ingår i: Quaternary Research. - 0033-5894 .- 1096-0287. ; 68:2, s. 184-195
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative high-resolution autumn (September-November) temperature reconstruction for the southeastern Swiss Alps back to AD 1580 is presented here. We used the annually resolved biogenic silica (diatoms) flux derived from the accurately dated and annually sampled sediments of Lake Silvaplana (46°27'N, 9°48'E, 1800 m a.s.1.). The biogenic silica flux smoothed by means of a 9-yr running mean was calibrated (r=0.70, p<0.01) against local instrumental temperature data (AD 1864-1949). The resulting reconstruction (±2 standard errors=±0.7 °C) indicates that autumns during the late Little Ice Age were generally cooler than they were during the 20th century. During the cold anomaly around AD 1600 and during the Maunder Minimum, however, the reconstructed autumn temperatures did not experience strong negative departures from the 20th-century mean. The warmest autumns prior to 1900 occurred around AD 1770 and 1820 (0.75 °C above the 20th-century mean). Our data agree closely with two other autumn temperature reconstructions for the Alps and for Europe that are based on documentary evidence and are completely unrelated to our data, revealing a very consistent picture over the centuries.
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| 4. |
- Burman, Johan, 1966, et al.
(författare)
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Oceanography in northwestern Europe during the last interglacial from intrashell d18O ranges in Littorina littorea gastropods
- 2008
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 70:1, s. 121-128
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Tidskriftsartikel (refereegranskat)abstract
- Coastal sea-surface temperature (SST) and sea-surface salinity (SSS), including seasonality, in northwest (NW) Europe during the early phase of the Eemian interglacial ca. 125 ka ago were reconstructed from Littorina littorea (common periwinkle) gastropods. The results were based on intra-annual δ18O analyses in recent and fossil shells, mainly originating from the sea of Kattegat (Sweden) and the English Channel (United Kingdom), and confined to intertidal settings. The Eemian L. littorea shells indicated annual SSTs in the range 8-18°C for the English Channel and 8-26°C for Kattegat. All specimens from the Eemian sites experienced summer SSTs of ca. 1-3°C above recent conditions. The estimated winter SST in the English Channel during the Eemian was comparable to modern measurements of ca. 8°C. However, the Kattegat region displayed Eemian winter SST approximately 8°C warmer than today, and similar to conditions in the western English Channel. The recent-fossil isotope analogue approach indicated high SSS above 35 practical salinity units (psu) for a channel south of England in full contact with the North Atlantic Ocean during the last interglacial. In addition, the Kattegat shells indicated a SSS of ca. 29 psu, which points out a North Sea affinity for this region during the Eemian.
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| 5. |
- Cardyn, R., et al.
(författare)
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Molar gas ratios of air entrapped in ice : A new tool to determine the origin of relict massive ground ice bodies in permafrost
- 2007
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 68:2, s. 239-248
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Tidskriftsartikel (refereegranskat)abstract
- The molar ratios of atmospheric gases change during dissolution in water due to differences in their relative solubilities. We exploited this characteristic to develop a tool to clarify the origin of ice formations in permafrost regions. Extracted from ice, molar gas ratios can distinguish buried glacier ice from intrasedimental ground ice formed by freezing groundwaters. An extraction line was built to isolate gases from ice by melting and trapping with liquid He, followed by analysis of N2, O2,, Ar, 18OO2 and 15NN2, by continuous flow mass spectrometry. The method was tested using glacier ice, aufeis ice (river icing) and intrasedimental ground ice from sites in the Canadian Arctic. O2/Ar and N2/Ar ratios clearly distinguish between atmospheric gas in glacial ice and gases from intrasedimental ground ice, which are exsolved from freezing water. δ15NN2 and δ18OO2 in glacier ice, aufeis ice and intrasedimental ground ice do not show clear distinguishing trends as they are affected by various physical processes during formation such as gravitational settling, excess air addition, mixing with snow pack, and respiration.
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| 6. |
- Courtney Mustaphi, Colin J., et al.
(författare)
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A 3000-year record of vegetation changes and fire at a high-elevation wetland on Kilimanjaro, Tanzania
- 2021
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Ingår i: Quaternary Research. - : Cambridge University Press. - 0033-5894 .- 1096-0287. ; 99, s. 34-62
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Tidskriftsartikel (refereegranskat)abstract
- Kilimanjaro is experiencing the consequences of climate change and multiple land-use pressures. Few paleoenvironmental and archeological records exist to examine historical patterns of late Holocene ecosystem changes on Kilimanjaro. Here we present pollen, phytolith, and charcoal (>125 mu m) data from a palustrine sediment core that provide a 3000-year radiocarbon-dated record collected from a wetland near the headwaters of the Maua watershed in the alpine and ericaceous vegetation zones. From 3000 to 800 cal yr BP, the pollen, phytolith, and charcoal records show subtle variability in ericaceous and montane forest assemblages with apparent multicentennial secular variability and a long-term pattern of increasing Poaceae and charcoal. From 800 to 600 cal yr BP, montane forest taxa varied rapidly, Cyperaceae abundances increased, and charcoal remained distinctly low. From 600 yr cal BP to the present, woody taxa decreased, and ericaceous taxa and Poaceae dominated, with a conspicuously increased charcoal influx. Uphill wetland ecosystems are crucial for ecological and socioeconomic resilience on and surrounding the mountain. The results were synthesized with the existing paleoenvironmental and archaeological data to explore the high spatiotemporal complexity of Kilimanjaro and to understand historical human-environment interactions. These paleoenvironmental records create a long-term context for current climate, biodiversity, and land-use changes on and around Kilimanjaro.
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| 7. |
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| 8. |
- Curry, B. Brandon, et al.
(författare)
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The DeKalb mounds of northeastern Illinois as archives of deglacial history and postglacial environments
- 2010
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 74:1, s. 82-90
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Tidskriftsartikel (refereegranskat)abstract
- The ""type"" DeKalb mounds of northeastern Illinois, USA (42.0 degrees N, -88.7 degrees W), are formed of basal sand and gravel overlain by rhythmically bedded fines, and weathered sand and gravel. Generally from 2 to 7 m thick, the fines include abundant fossils of ostracodes and uncommon leaves and stems of tundra plants. Rare chironomid head capsules, pillclam shells, and aquatic plant macrofossils also have been observed. Radiocarbon ages on the tundra plant fossils from the ""type"" region range from 20,420 to 18,560 cal yr BP. Comparison of radiocarbon ages of terrestrial plants from type area ice-walled lake plains and adjacent kettle basins indicate that the topographic inversion to ice-free conditions occurred from 18,560 and 16,650 cal yr BP. Outside the ""type"" area, the oldest reliable age of tundra plant fossils in DeKalb mound sediment is 21,680 cal yr BP; the mound occurs on the northern arm of the Ransom Moraine (-88.5436 degrees W, 41.5028 degrees N). The youngest age, 16,250 cal yr BP, is associated with a mound on the Deerfield Moraine (-87.9102 degrees W, 42.4260 degrees N) located about 9 km east of Lake Michigan. The chronology of individual successions indicates the lakes persisted on the periglacial landscape for about 300 to 1500 yr.
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| 9. |
- Fenn, Kaja, et al.
(författare)
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Insights into the provenance of the Chinese Loess Plateau from joint zircon U-Pb and garnet geochemical analysis of last glacial loess
- 2018
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 89:3, s. 645-659
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Tidskriftsartikel (refereegranskat)abstract
- The Chinese Loess Plateau, the world's largest and oldest loess record, preserves evidence of Asia's long-term dust source dynamics, but there is uncertainty over the source of the deposits. Recent single-grain detrital zircon U-Pb age analysis has progressed this issue, but debates remain about source changes, and the generation and interpretation of zircon data. To address this, we analyze different groupings of new and existing datasets from the Loess Plateau and potential sources. We also present the results of a first high resolution sampling, multi-proxy provenance analysis of Beiguoyuan loess using U-Pb dating of detrital zircons and detrital garnet geochemistry. The data shows that some small source differences seem to exist between different areas on the Loess Plateau. However, sediment source appears to be unchanging between loess and palaeosols, supporting a recent material recycling hypothesis. Our zircon and garnet data demonstrates, however, that Beiguoyuan experienced a temporary, abrupt source shift during the last glacial maximum, implying that local dust sources became periodically active during the Quaternary. Our results highlight that grouping data to achieve bigger datasets could cause identification of misleading trends. Additionally, we suggest that multi-proxy single-grain approaches are required to gain further insight into Chinese Loess Plateau dust sources.
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| 10. |
- Feurdean, Angelica, et al.
(författare)
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Younger Dryas to mid-Holocene environmental history of the lowlands of NW Transylvania, Romania
- 2007
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 68:3, s. 364-378
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Tidskriftsartikel (refereegranskat)abstract
- Pollen, micro-charcoal and total carbon analyses on sediments from the Turbuta palaeolake, in the Transylvanian Basin of NW Romania, reveal Younger Dryas to mid-Holocene environmental changes. The chronostratigraphy relies on AMS 14C measurements on organic matter and U/Th TIMS datings of snail shells. Results indicate the presence of Pinus and Betula open woodlands with small populations of Picea, Ulmus, Alnus and Salix before 12,000 cal yr BP. A fairly abrupt replacement of Pinus and Betula by Ulmus-dominated woodlands at ca. 11,900 cal. yr BP likely represents competition effects of vegetation driven by climate warming at the onset of the Holocene. By 11,000 cal yr BP, the woodlands were increasingly diverse and dense with the expansion of Quercus, Fraxinus and Tilia, the establishment of Corylus and the decline of upland herbaceous and shrubs taxa. The marked expansion of Quercus accompanied by Tilia between 10,500 and 8000 cal yr BP could be the result of low effective moisture associated with both low elevation of the site and with regional change towards a drier climate. At 10,000 cal yr BP, Corylus spread across the region, and by 8000 cal yr BP it replaced Quercus as a dominant forest constituent, with only little representation of Picea abies. Carpinus became established around 5500 cal yr BP, but it was only a minor constituent in local woodlands until ca. 5000 cal yr BP. Results from this study also indicate that the woodlands in the lowlands of Turbuta were never closed.
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