27 research outputs found
Late Quaternary evolution of the sedimentary environment in Modrejce near Most na Soči (Soča Valley, Julian Alps)
Geomorphological and geological mapping have long been used to study the glacial history of the Slovenian
Alps, but many uncertainties remain regarding the time and extent of Pleistocene glaciations there. Glacial
landforms and undisturbed glacial deposits are rare in the areas of the former glacier terminus, especially in the
Soča Valley, where large discrepancies in the interpretation of the extent of the former Soča Glacier have been
reported. Early studies proved inconclusive as to whether one or two glaciations extended into the Soča Valley as
far as Most na Soči. In order to answer this question, the Quaternary sedimentary succession and landforms in
the Modrejce Valley near Most na Soči were investigated. New geological and geomorphological field data allow
the interpretation of the sedimentary environment and the stratigraphic relationships between different units.
In response to glacial dynamics, the sedimentation developed from glaciofluvial and glaciolacustrine to fully
glacial environments, followed by slope deposition. At higher altitudes lateral moraines are preserved, while
the staircase-like slope below has been carved into older glacial, glaciofluvial and glaciolacustrine deposits by
glacial and post-glacial processes, including fluvial erosion and slope dynamics. We conclude that the succession
studied here was deposited over the course of two different glacial advances – LGM and pre-LGM. Our study
thus suggests that the Soča Glacier extended as far as the area of Most na Soči twice over the course of the late
Quaternary
Pleistocenska poledenitev v Logarski dolini
Članek prinaša rezultate preučevanja ledeniških ostankov iz časa zadnjega poledenitvenega viška na območju Logarske doline v Kamniško-Savinjskih Alpah. Namen članka je reinterpretirati dosedanje ugotovitve in podati novo tolmačenje obsega viška zadnje poledenitve na tem območju. S pomočjo ugotovitev, pridobljenih s terenskim delom, so bile opravljene morfometrične analize, po katerih smo začrtali skrajno mejo poledenitvenega sunka in izdelali tridimenzionalno rekonstrukcijo topografije površja takratnega ledenika
Spatial and climatic characterization of three glacial stages in the Upper Krnica Valley, SE European Alps
The southeastern European Alps represent the spot where mean annual precipitation is at its highest in
the entire Alpine chain. Accordingly, the glacial evolution here might have a different spatial and
chronological pattern if compared with other alpine areas. This paper discusses geomorphological evidence
of three glacial stages from the Krnica Valley in the Julian Alps of Slovenia, and is the first step
towards a comprehensive palaeoglaciological studies in this alpine sector. Very well-preserved glacial
landforms in the Upper Krnica Valley allowed the reconstruction of glacier surface topographies and
corresponding equilibrium line altitudes (ELAs) by means of field-based geomorphological and sedimentological
data and by using geospatial analysis. The uppermost frontal moraines belong to the Little
Ice Age (LIA) and the corresponding ELA is estimated at 1973 m a.s.l. Other two stages with the ELA
depressed by 50 m and 161 m compared to the LIA ELA, suggest early Holocene and Younger Dryas ages
of the palaeoglaciers, respectively. This assumption ensues from absolute age datings and related ELA
depressions observed elsewhere in the European Alps. The presence of buried ice under the debris in the
Krnica cirque, imaged through geophysical investigations, point to peculiar microclimatic conditions able
to preserve relict glacier ice. This is favoured by the recursive presence of snow on the ground caused by
the extreme summer shading and the significant winter snow-recharge triggered by snowblow and
avalanche feeding. The possible evolution of such relict ice under the ongoing climate warming is also
discussed
Is that a relict rock glacier?
The distribution of rock glaciers is often used to investigate the occurrence of permafrost inmountain areas and to
understand their climate and paleoclimate evolution. This requires the creation of regional and global inventories
capable of discriminating active and relict landforms in order to forecast the presence or absence of ice in the
ground. In this paper, geomorphological, geophysical and microclimatic surveys are performed on a rock glacier
of the Carnic Alps (Eastern European Alps). In the classification currently used for implementing regional inventories
of permafrost evidence in the Alps, this rock glacier would be defined as relict. However the geophysical,
climatological and geomorphological results indicate that internal ice is widespread in large portions of the
rock glacier. These are generally interpreted as ice in pore spaces and local ice lenses, probably without layers
of massive ice. Moreover the occurrence of ice during the maximum thawing season at depths b15 m, assumed
here as the depth of zero annual amplitude, suggests that the ice occurring within the rock glacier is related to
current cryotic conditions due to density driven air flow (i.e. the chimney effect). This research demonstrates
that the current altitudinal limit of alpine permafrost can be locally several hundreds of meters lower than forecasted
byempiricalmodeling based only on the rock glacier distribution and classification. Therefore, rock glacier
classifications based only on remote sensing and geomorphological evidence as the main sources for extracting
regional climate and paleoclimate signals should be treated with caution
Paraglacial adjustment of alluvial fans to the last deglaciation in the Snežnik Mountain, Dinaric karst (Slovenia)
Glaciokarst depressions are major glacigenic depocenters in the Dinaric mountain karst areas and often store important information about the timing and nature of glacial processes and paraglacial sediment reworking. This study focuses on Praprotna draga, which is one of the largest glaciokarst depressions in the Sneznik Mountain (Dinaric karst), with an area of similar to 3.4 km(2) and a maximum depth of 140 m. The western slopes of the depression are characterized by undulated moraine morphology and alluvial fans are filling its entire floor. We present the results on the thickness, origin and age of the sediment infill using a complementary geomorphological, sedimentological, geophysical and dating approach. Distribution of moraines point to two glacial advances that were associated with two main alluvial fan aggradation phases recognized using the electrical resistivity tomography measurements. The youngest alluvial deposits were sampled for cosmogenic Cl-36 analysis using amalgamated carbonate pebbles. The depth profile of Cl-36 concentrations suggests an age of 123 +/- 1.7 ka when assuming a likely denudation rate of 20 mm ka(-1). Since the existence of the Younger Dryas glaciers in the study area is climatically difficult to explain, we tentatively propose that the youngest alluvial deposition in Praprotna draga took place after the glacier retreat during the paraglacial period. Our findings suggest that the time window of paraglacial adjustment in the Sneznik Mountain was brief and likely conditioned by quick recolonization with vegetation and inefficient surface runoff on deglaciated karst terrain. (C) 2019 Elsevier B.V. All rights reserved
Recent increases in winter snowfall provide resilience to very small glaciers in the Julian Alps, Europe
Very small glaciers (<0.5 km2) account for more than 80% of the total number of glaciers and more than 15% of the total glacier area in the European Alps. This study seeks to better understand the impact of extreme snowfall events on the resilience of very small glaciers and ice patches in the southeastern European Alps, an area with the highest mean annual precipitation in the entire Alpine chain. Mean annual precipitation here is up to 3300 mm water equivalent, and the winter snow accumulation is approximately 6.80 m at 1800 m asl averaged over the period 1979–2018. As a consequence, very small glaciers and ice/firn patches are still present in this area at rather low altitudes (1830–2340 m). We performed repeated geodetic mass balance measurements on 14 ice bodies during the period 2006–2018 and the results show an increase greater than 10% increase in ice volume over this period. This is in accordance with several extreme winter snow accumulations in the 2000s, promoting a positive mass balance in the following years. The long-term evolution of these very small glaciers and ice bodies matches well with changes in mean temperature of the ablation season linked to variability of Atlantic Multidecadal Oscillation. Nevertheless, the recent behaviour of such residual ice masses in this area where orographic precipitation represents an important component of weather amplification is somehow different to most of the Alps. We analysed synoptic meteorological conditions leading to the exceptional snowy winters in the 2000s, which appear to be related to the influence and modification of atmospheric planetary waves and Arctic Amplification, with further positive feedbacks due to change in local sea surface temperature and its interactions with low level flows and the orography. Although further summer warming is expected in the next decades, we conclude that modification of storm tracks and more frequent occurrence of extreme snowfall events during winter are crucial in ensuring the resilience of small glacial remnants in maritime alpine sectors