Published Papers:
Zdzislaw Jary (2009): Periglacial markers within the Late Pleistocene loess–palaeosol sequences in Poland and Western Ukraine. Quaternary International 198: 124–135
Stratigraphic loess–palaeosol sequences represent exceptional, climate-controlled, terrestrial records of interglacial–glacial cycles. One of the most spectacular features within the northern part of the European loess belt is the occurrence of well-preserved relicts of the periglacial structures. From a variety of periglacial structures, three types are especially useful to reconstruct the former periglacial environment: cryogenic wedges with primary mineral infilling, cryoturbation and gelifluction structures; and ice-wedge casts. These structures form well-distinguishable horizons within loess–palaeosol sequences and their stratigraphic positions are not random. Periglacial horizons recorded in the Late Pleistocene loess–palaeosol sequences in the study area were formed as a result of extreme climatic conditions and/or rapid environmental changes during cold events of the Last Glacial period. These horizons are noted in almost all investigated sections, and thus they can be used as stratigraphic markers. The number of periglacial horizons and their morphological features vary, depending on their geographical settings and local conditions. The periglacial record indicates the occurrence of four main cold stages during the Last Glacial period. Two earlier stages are recorded in the last interglacial–early glacial palaeosol complex. Their onset was probably rapid. These short cold periods can be correlated with MIS 5d and 5b. The next two periglacial stages most probably correspond with MIS 4 and 2. Only during the last two stages were ice-wedges formed in the northern zone of the investigated loess area. This record indicates the twofold expansion and disappearance of the permafrost during the Last Glacial period.
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The effect of climate warming and permafrost thaw on desertification in the Qinghai–Tibetan Plateau
Pages 182-190
Xian Xue, Jian Guo, Bangshuai Han, Qingwei Sun, Lichao Liu
Abstract
Four sets of remote sensing images from
1987, 1994, 2000, and 2006, 50 years of meteorological and soil
moisture data corresponding to different desertified lands were
combined with populations and livestock data to analyze the process and
cause of desertification in a portion of the Qinghai–Tibetan Plateau
(QTP). It showed that surface soil temperature in the region has
increased at an average rate of 0.6 °C per decade between 1980 and
2005, the thawing days on the surface have increased by 60 days from
1983 to 2001, and the depth of the seasonal thawing layer has increased
by 54 cm, 102 cm and 77 cm in April, May and June, respectively, from
1983 to 2003. As a result, the upper soil layer has become drier due to
the thickening active layer and soil water infiltration. These changes,
in turn, have inhibited the growth of alpine meadow vegetation that has
shallow root systems. It is concluded that climate warming and
permafrost thawing have caused desertification in grazing regions of
the Qinghai–Tibetan Plateau (QTP).
Pages 312-320
Jean-Claude Hippolyte, Didier Bourlès, Régis Braucher, Julien Carcaillet, Laëtitia Léanni, Maurice Arnold, Georges Aumaitre
Abstract
Sackungs are the largest gravitational deformation observed in mountains. They are characterized by the long-term slowness of the movements, but their mechanism is still not well understood. Nowadays cosmic ray exposure (CRE) dating methods allow dating the morphologic structures involved in sackung and can contribute at the understanding of their origin. In the Alps, the 5.3 km long Arcs sackung initiated during the activity of rock glaciers. Three samples from these faulted rock glaciers provide their first CRE ages and show that at 2000 m elevation these block accumulations moved during the Younger Dryas and stopped in early Holocene. Six 10Be ages of fault scarps show that the Arcs sackung lasted only a few thousand years and stopped at about 8462 ± 432 10Be yr. They also reveal that deformation migrated upslope in agreement with a mechanism of flexural toppling of vertical layers. This unique and long gravitational event, characterized by migration of the deformation, does not support earthquake shaking as triggering mechanism for individual faults. It shows that, in the upper Isère valley, slope deformation was delayed of several thousand years after glacial debuttressing, and is not anymore active despite its fresh morphology.
Relict sand wedges in southern Patagonia and their stratigraphic and paleo-environmental significance
Pages 1188-1199
J. Bockheim, A. Coronato, J. Rabassa, B. Ercolano, J. Ponce
Relict sand wedges are ubiquitous in southern Patagonia. At six sites
we conducted detailed investigations of stratigraphy, soils, and wedge
frequency and characteristics. Some sections contain four or more
buried horizons with casts. The cryogenic features are dominantly
relict sand wedges with an average depth, maximum apparent width,
minimum apparent width, and H/W of 78, 39, 3.8, and 2.9 cm,
respectively. The host materials are fine-textured (silt loam, silty
clay loam, clay loam) till and the infillings are aeolian sand. The
soils are primarily Calciargidic Argixerolls that bear a legacy of
climate change. Whereas the sand wedges formed during very cold (−4 to
−8 °C or colder) and dry (ca. ≤100 mm precipitation/yr) glacial
periods, petrocalcic horizons from calcium carbonate contributed by
dustfall formed during warmer (7 °C or warmer) and moister (≥250 mm/yr)
interglacial periods. The paleo-argillic (Bt) horizons reflect
unusually moist interglacial events where the mean annual precipitation
may have been 400 mm/yr. Permafrost was nearly continuous in southern
Patagonia during the Illinoian glacial stage (ca. 200 ka), the early to
mid-Pleistocene (ca. 800–500 ka), and on two occasions during the early
Pleistocene (ca. 1.0–1.1 Ma).
Retrogression characteristics of landslides in fine-grained permafrost soils, Mackenzie Valley, Canada
Baolin Wang, Bhuwani Paudel, Haoqiang Li (Landslides 6/2: 121-127)
Abstract Thirteen landslides
(retrogressive thaw flows) were investigated to study the behavior of
thaw retrogression in permafrost in the Mackenzie Valley, Northwest
Territories (NWT), Canada. Those landslides are all in fine-grained
ice-rich permafrost soils. Such landslides usually start from
small-scale slope failures followed by retrogressive thaw flows when
ice-rich permafrost soils are exposed to the atmosphere. The landslides
were marked with survey stakes to measure their retreat rates for the
thawing season of 2007. Two correlations are presented: one is between
scarp wall height and retreat rate; another is between overall slope
angle and retreat rate. It was found that thaw flow retrogression rate
increases with increase in scarp wall height and slope angle up to a
certain limit. It was also confirmed that thaw flow retrogression is
not influenced by slope orientation.
The
potential of optically stimulated luminescence for dating periglacial
slope deposits — A case study from the Taunus area, Germany
Pages 66-78
D. Hülle, A. Hilgers, P. Kühn, U. Radtke
Abstract
Periglacial
deposits overlying bedrock are widespread in the German low mountain
ranges. The age of these deposits is still a matter of debate and
therefore, three sections in the Taunus area were investigated with
luminescence dating techniques. In general, the heterogeneity of the
sediment, which is characterized by a mixture of grain sizes from clay
to cobbles, is the main problem for dating as dose-rate determination
is complicated. This is demonstrated based on comparisons of high
resolution γ-ray spectrometry, neutron activation analysis, β-counting
and in-situ measurements of
the γ-dose-rate. Insufficient bleaching due to the transport mode, and
consequently age overestimation, was expected to be a major problem for
luminescence dating of periglacial slope deposits. In order to get a
detailed insight into equivalent dose variations due to partial
bleaching, single aliquot regenerative dose (SAR) protocols have been
applied to the polymineralic fine-grain fraction, sand-sized K-feldspar
and quartz extracts. Our results do not confirm partial bleaching as a
problem, except for the basal layer. The luminescence properties vary
substantially depending on the site, the layer and the mineral fraction
that is measured for equivalent dose determination. However, hardly any
systematic tendencies can be observed. Micromorphology analysis
indicates post-depositional mixing which complicates the equivalent
dose estimation even further. Due to the lack of accuracy, the
relevance of the presented data for palaeolandscape reconstruction is
limited. Based on these observations, suggestions are made to improve
future attempts of dating periglacial cover beds with optically
stimulated luminescence (OSL).
Development
of tongue-shaped and multilobate rock glaciers in alpine environments –
Interpretations from ground penetrating radar surveys
Pages 94-107
John J. Degenhardt Jr.
Abstract
Rock glaciers occur as lobate or
tongue-shaped landforms composed of mixtures of poorly sorted, angular
to blocky rock debris and ice. These landforms serve as primary sinks
for ice and water storage in mountainous areas and represent
transitional forms in the debris transport system, accounting for ~ 60%
of all mass transport in some alpine regions. Observations of active
(flowing) alpine rock glaciers indicate a common association between
the debris that originates from cirque headwalls and the depositional
lobes that comprise them. The delivery of this debris to the rock
glacier is regulated primarily by the rate of headwall erosion and the
point of origin of debris along the headwall. These factors control the
relative movement of individual depositional lobes as well as the
overall rate of propagation of a rock glacier. In recent geophysical
studies, a number of alpine rock glaciers on Prins Karls Forland and
Nordenskiöldland, Svalbard, Norway, and the San Juan Mountains of
southwest Colorado, USA, have been imaged using ground penetrating
radar (GPR) to determine if a relationship exists between the internal
structure and surface morphology. Results indicate that the overall
morphologic expression of alpine rock glaciers is related to lobate
deposition during catastrophic episodes of rockfall that originated
from associated cirque headwalls. Longitudinal GPR profiles from alpine
rock glaciers examined in this study suggests that the difference in
gross morphology between the lobate and tongue-shaped rock glaciers can
be attributed primarily (but not exclusively) to cirque geometry,
frequency and locations of debris discharge within the cirque, and the
trend and magnitude of valley gradient in relation to cirque
orientation. Collectively, these factors determine the manner in which
high magnitude debris discharges, which seem to be the primary
mechanism of formation, accumulate to form these rock glaciers.
Eemian and Late Glacial/Holocene palaeoenvironmental records from permafrost sequences at the Dmitry Laptev Strait (NE Siberia, Russia)
Pages 73-95
Sebastian Wetterich, Lutz Schirrmeister, Andrei A. Andreev, Michael Pudenz, Birgit Plessen, Hanno Meyer, Viktor V. Kunitsky
Abstract
Terrestrial permafrost sections from the southern and northern coasts of Dmitry Laptev Strait have preserved records of landscape transition from glacial to interglacial periods. They allow geomorphologic and environmental changes to be traced from pre-Eemian time to the Eemian, and from the Late Glacial to the Holocene. The transition from one period to another induced extensive thawing of permafrost (thermokarst). Evolving thermokarst depressions transformed formerly frozen ground into taberal (unfrozen) deposits with accumulating overlying lacustrine deposits. Lacustrine horizons rich in palaeontological remains retain evidence of changes in environmental conditions. The pollen records reflect changes from grass-sedge dominated vegetation during the Early Eemian to shrub dominated spectra during the Middle Eemian thermal optimum followed by Late Eemian grass-sedge dominated tundra vegetation. Abundant Larix pollen have been found in Middle Eemian deposits from the south coast of the Dmitry Laptev Strait (Oyogos Yar), but are absent in similar deposits from the north coast (Bol'shoy Lyakhovsky Island), likely indicating that the northern tree line was located near the Oyogos Yar region during the Eemian thermal optimum. Grass-sedge dominated tundra vegetation occurred during the Late Glacial/Holocene transition which was replaced by shrub tundra during the early Holocene. Rich fossil ostracod records from Eemian and Late Glacial/Holocene lacustrine deposits could be correlated with the Eemian thermal optimum and the Late Glacial Allerød warm period. For both periods, the stable oxygen isotope data from the fossil ostracods suggest an approximate mean summer water temperature range between about 10 and 19 °C in the palaeo-lakes.