scholarly journals Late Holocene ice-wedge polygon dynamics in northeastern Siberian coastal lowlands

2018 ◽  
Vol 50 (1) ◽  
pp. e1462595 ◽  
Author(s):  
Lutz Schirrmeister ◽  
Anatoly Bobrov ◽  
Elena Raschke ◽  
Ulrike Herzschuh ◽  
Jens Strauss ◽  
...  
Keyword(s):  
Late Holocene ◽  
Ice Wedge ◽  
Coastal Lowlands

Interpretation of radiocarbon dates from the upper surface of late-Holocene peat layers in coastal lowlands

The Holocene ◽  
2006 ◽  
Vol 16 (1) ◽  
pp. 51-61 ◽  
Author(s):  
M. P. Waller ◽  
A. J. Long ◽  
J. E. Schofield
Keyword(s):  
Plant Communities ◽  
Late Holocene ◽  
A Priori ◽  
Radiocarbon Dates ◽  
Coastal Lowland ◽  
The North ◽  
Clastic Sediments ◽  
The North Sea ◽  
Underlying Processes ◽  
Coastal Lowlands

Marine/brackish clastic sediments replace freshwater peats in the stratigraphic column of many coastal lowland areas bordering the North Sea during the late Holocene. Radiocarbon dates are routinely used to provide a chronology for this shift. We examine the assumptions underpinning this approach. The results of investigations from 13 sites in the Rye area of Romney Marsh, southeast England, are reported. Dates from apparently gradational contacts of a highly humified, laterally persistent, peat layer range from 3170-2840 cal. yr BP to 1290-1050 cal. yr BP. Multiple inundations or prolonged gradual inundation are nevertheless rejected, as discrete post-peat bodies of sediment are absent and because peat growth appears to have slowed-down or ceased at many sites in advance of inundation. Additionally in the Rye area, sharp contacts are widespread and the pollen assemblages rarely indicate the occurrence of transitional plant communities. A review of the dating evidence from other coastal lowland regions reveals that multiple dating of the upper surface of peat beds invariably produces diachronous results. As a consequence time transgressive processes feature prominently as causal mechanisms underlying this shift. However, many of the dating difficulties recognized in the Rye area appear to apply to other regions. We conclude that radiocarbon dates from the upper surface of peat layers should in most instances only be regarded as limiting ages for the deposition of the overlying clastic sediments. New chronologies need to be built without a priori assumptions as to the underlying processes, ideally through the direct dating of the clastic sediments.

scholarly journals Environmental Change in Coastal Lowlands around the Lake Hamana during the Middle to Late Holocene

2011 ◽  
Vol 84 (3) ◽  
pp. 258-273 ◽  
Author(s):  
SATO Yoshiki ◽  
FUJIWARA Osamu ◽  
ONO Eisuke ◽  
UMITSU Masatomo
Keyword(s):  
Environmental Change ◽  
Late Holocene ◽  
Lake Hamana ◽  
Coastal Lowlands

Modern and past periglacial features in Central Asia and their implication for paleoclimate reconstructions

2015 ◽  
Vol 40 (3) ◽  
pp. 369-391 ◽  
Author(s):  
Frank Lehmkuhl
Keyword(s):  
Central Asia ◽  
Late Holocene ◽  
Large Degree ◽  
Climatic Conditions ◽  
Ice Age ◽  
Soil Humidity ◽  
Air Temperatures ◽  
Rock Glaciers ◽  
Ice Wedge ◽  
Moisture Conditions

In the continental areas of Central and High Asia, periglacial landform assemblages, sediment structures and processes are mainly influenced and determined by of soil humidity during freeze–thaw cycles. These cryogenic processes result in periglacial landforms such as solifluction, earth hummocks or patterned ground. The distribution of rock glaciers as clear indicators of permafrost is additionally determined by rock fall or moraine debris composed of large boulders (e.g. of granite). Periglacial features were used to reconstruct past climatic conditions, e.g. relict involutions and ice-wedge casts provide evidence for the distribution of former permafrost, say, for the Last Glacial Maximum (LGM). Past temperatures, e.g. mean annual air temperatures, can be estimated from these periglacial features and can be compared with other proxy data, such as glacier fluctuations. Examples from late Holocene solifluction activity in the Altai, Khangai and north-eastern Tibetan Plateau show a different intensity of solifluction processes during the late Holocene and Little Ice Age due to a decrease in temperature and higher soil humidity. The distribution of past permafrost in some regions is still a matter of debate because of different interpretations of sediment structures: sometimes features described as ice-wedge casts may be caused by roots or desiccation cracks due to drying of clay rich sediments. Seismically deformed unconsolidated deposits (seismites) can also be misinterpreted as periglacial involutions. The lack of certain landform assemblages and sediment structures does not necessarily mean that the area had no permafrost. Moisture conditions can also determine the periglacial landform generation to a large degree. They can be ordered in Central Asia as follows (from highest moisture availability to lowest): solifluction; rock glacier; permafrost involutions; ice-wedge casts; sand-wedge casts.

scholarly journals Late Holocene Mangrove Habitat and Evolution of Coastal Lowlands in Southern Thailand.

Tropics ◽  
1999 ◽  
Vol 8 (3) ◽  
pp. 317-328 ◽  
Author(s):  
Masatomo UMITSU ◽  
Paiboon PRAMOJANEE ◽  
Akio OHIRA ◽  
Kumiko KAWASE
Keyword(s):  
Late Holocene ◽  
Mangrove Habitat ◽  
Southern Thailand ◽  
Coastal Lowlands

scholarly journals Middle and Late Pleistocene climate and continentality inferred from ice wedges at Batagay megaslump in the Northern Hemisphere’s most continental region, Yana Highlands, interior Yakutia

2018 ◽  
Author(s):  
Thomas Opel ◽  
Julian B. Murton ◽  
Sebastian Wetterich ◽  
Hanno Meyer ◽  
Kseniia Ashastina ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Late Holocene ◽  
Winter Climate ◽  
Isotopic Signatures ◽  
Pleistocene Climate ◽  
Winter Temperatures ◽  
Ice Wedge ◽  
Middle And Late Pleistocene ◽  
Sand Sheets ◽  
Ice Complex

Abstract. Ice wedges in the Yana Highlands of interior Yakutia – the most continental region of the Northern Hemisphere – were investigated to elucidate the winter climate and continentality during the Middle to Late Pleistocene. The Batagay megaslump exposes ice wedges and composite wedges that were sampled from three cryostratigraphic units: the lower sand unit of Marine Isotope Stage (MIS) 6 age, the upper Ice Complex (Yedoma) and the upper sand unit (both MIS3 to MIS2). A terrace of the nearby Adycha River provides a Late Holocene (MIS1) ice wedge that serves as a modern endmember for analysis. Stable-isotope values of ice wedges in the MIS3 upper Yedoma Ice Complex at Batagay are more depleted (mean δ18O about −35 ‰) than those from 17 other ice-wedge sites across coastal and central Yakutia. This observation points to lower winter temperatures and, therefore, higher continentality in the Yana Highlands during MIS3. Likewise, more depleted isotope values compared to other sites in Yakutia are found in Holocene wedge ice (mean δ18O about −29 ‰). Ice-wedge isotopic signatures of the MIS6 lower sand unit (mean δ18O about −33 ‰) and of the MIS3-2 upper sand unit (mean δ18O from about −33 to −30 ‰) are less distinctive regionally and preserve traces of fast formation in rapidly accumulating sand sheets and of post-depositional fractionation.

scholarly journals Late Holocene Vegetation and Environmental Changes of Coastal Lowlands in Northern Iran: Possible Role of Climate, Human Impact and Caspian Sea Level Fluctuations

2021 ◽  
Author(s):  
Fang Gu ◽  
Kamaleddin Alizadeh ◽  
Hermann Behling
Keyword(s):  
Human Impact ◽  
Caspian Sea ◽  
Late Holocene ◽  
Biological Diversity ◽  
Ice Age ◽  
Northern Iran ◽  
Climatic Fluctuations ◽  
Alder Forest ◽  
Coastal Lowlands

Abstract Coastal forests and wetlands play an important role in supporting biological diversity, protecting the hinterlands and shorelines along the continental margins from erosion, as well as for contributing to carbon and freshwater storage. To reconstruct late Holocene vegetation and environmental dynamics in the coastal lowlands in northern Iran and detect the possible role of climate, human impact and Caspian Sea (CS) level fluctuation on coastal ecosystems, a multi-proxy analysis including pollen, spores, non-pollen palynomorphs, macro-charcoal and X-ray fluorescence analysis, have been applied on the radiocarbon dated sediment cores from the Eynak (EYK) lagoon further inland and Bibi Heybat (BBH) alder swamp near the coast. Open wetlands covered relatively large areas since the recorded period (1450 cal yr BP). At BBH larger areas of open vegetation occurred and alder forests covered only small areas that expanded during the late Little Ice Age (1650-1850 AD) and were most abundant during the last about 100 years. Further inland at EYK, areas of alder and mixed broad-leaved Hyrcanian forest were larger. Alder forest in general expanded since 600 cal yr BP. In the last 170 years, alder forest areas and wetlands declined strongly, due to deforestation and strong human activities. The intensity of human impact, climatic fluctuations and changes in CS level were the most important factors controlling the dynamics of the northern Iranian coastal vegetation.

Late Holocene syngenetic ice-wedge polygons development, Bylot Island, Canadian Arctic Archipelago

2004 ◽  
Vol 41 (8) ◽  
pp. 997-1012 ◽  
Author(s):  
Daniel Fortier ◽  
Michel Allard
Keyword(s):  
Late Holocene ◽  
Canadian Arctic ◽  
Canadian Arctic Archipelago ◽  
Thermal Contraction ◽  
Current Configuration ◽  
Outwash Plain ◽  
Bylot Island ◽  
Ice Wedge ◽  
The Mean ◽  
Organic Sediments

The initial configuration of the syngenetic ice-wedge polygons that developed in the outwash plain of glacier C-79 after 6000 BP was modified by the accumulation of wind-blown and organic sediments that began after 3670 ± 110 BP. The late Holocene sedimentation led to an increase in the thermal contraction coefficient of the soil and the formation of third- and fourth-order contraction cracks, partially explaining the current configuration of the polygonal network. The upturning of the sedimentary strata bordering the ice wedges was associated with the summer thermal expansion and resulting internal creep of the soil. The mean annual soil displacement coefficient was in the order of 2.5–2.7 × 10–5 /°C at the thousand-year scale. The late Holocene sedimentary strata under the centre of the polygons were undisturbed, which will make it possible to use this sedimentary record in further studies to attempt paleoenvironmental reconstructions from cores.

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