ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

landslides, and disruption of drainage. All these data are
best evaluated using a geographic information system
(Gis), where the topographic indicators along with other
data can be located and superimposed. Data from thousands
of abandoned mine locations have been evaluated in
this manner. The results indicate that subtle topographic
anomalies can identify potentially harmful impacts to the
environment. Locating these anomalies leads to cost-effective,
subsurface investigations and elimination of the environmental
hazards.
DIETER JAKEL
The formation of network and «Kessel»
dunes in BWk deserts (Gobi)
Institut fur Geographische Wissenschaften, Physische Geographie,
Freie Universitat Berlin, Grunewaldstr. 35, D-12165 Berlin, Germany
In September and early October 1995 we succeeded in
crossing the Badain Jaran Desert in Inner Mongolia (China)
four times (this desert is roughly the same size as Switzerland.)
We had to cross >400 m high mega-dunes, composed
of «dune ranges», aligned from southwest to
northeast, separated by «interdune corridors». Such dune
ranges are generally chains of star dunes; network and Kessel
dunes occur on their flanks and in the interdune corridors.
These secondary dunes consist of third-generation
dune sands superimposed on the mega-dunes, i.e, recently
and presently mobile loose sand overlies second-generation
sand layers, which have a higher percentage of clay
and silt and hence contain more moisture. The pattern of
the secondary dunes shows that they were formed by multidirectional
wind regimes.
Crossing the Badain J aran Desert was made possible, or at
least facilitated, by the fact that 1995 was a relatively rainy
year. Records show six days with heavy zonal, monsoonal
and cyclonic rainfall. The depth of moisture in the dune
sand and the infiltration behaviour of rainwater were measured.
Unique photographs were obtained because erosion
of the uppermost sand revealed the internal structure of
the mega-dunes, and the varying sand moisture resulted in
unusual colour effects. Observations of wind circulation
patterns after rainfall events helped to explain the formation
of the network and Kessel dunes. It was discovered
that the main controlling factor is the varying mobility of
dry and wet sand. As soon as corrasion and deflation processes
reached deeper, still-dry dune layers, hollows were
blown out. The overlying wet layers subsided and their edges
dried more quickly owing to greater exposure to the
wind. Doline-like depressions were formed, which are the
initial formation stage of either network or Kessel dunes,
depending on local circulation patterns. Hence the decisive
factors influencing the formation of such dunes are, first,
the complex infiltration processes of rainfall entering
dune sand and, second, the varying erodibility of dry and
216
wet sand. This process is intensified during the winter
months because the wet sand layers are then frozen.
OLEKSA J AKUBSKA
Tendencies of evolution of carbonate
mid-mountain slopes. The Western T atra Mts
Department of Earth Sciences, University of Silesia, Sosnowiec, Poland
The area of investigation in the Polish Tatra Mts. is located
in the limits: from the Mala Laka Valley to the Bystra Valley,
below the upper forest belt. The analysed area, with
features of a periglacial relief, is currently formed in the
conditions of temperate cool and cool climate. In the carbonate
rocks which outcrop there, four types of slopes have
been recognized: near-vertical wall scars, rock slopes,
rock-debris slopes, often termed mantle rock slopes, and
scree slopes. Mantle rock slopes of poligenetic structure
represent the commonest relief element.
The mechanical, mineralogical and petrographic compositions,
and CaC03 content of the rock debris material were
determined: Sarnia Skala, Dolinaza Bramka. The graphs of
grain-size frequency distribution, grain-size statistics and
CaC03 content are shown for using a laser. The values of
the grain-size statistics, mean, standard deviation, skewness
and kurtosis, have been determined using Folk and Ward's
(1957) formulas. The material studied shows a considerable
differentation of its mechanical composition in the individual
slope sections, However, a boulder-gravel, poortly
rounded fraction predominantes in each site. Slope deposits
show weak and rather not much differentiated sorting,
and positive, sometimes very positive skewness. The mean
values are differentiated and irregularly distributed along
the whole profile. It is assumed that the granulometric variation
of the deposits results from the climatic-vegetational
changes during late Pleistocene and Holocene. The material
studied shows different content of the CaC03 in the
individual fractions. The largest concentration of CaC03 ,
occurs in the boulder-gravel fraction and it gradually decreases
towards the smaller fractions. This relationship is
very clear along the whole slope profile.
Gravitational processes, modelling mantle rock-debris slopes
are the major ones-mainly of temperate activity including
soil-debris creening and land sliding. Rocks-debris
slopes are also modelled by outwash and mid-cover flow:
the share of the processes, mainly temperate ones, is similar.
The investigated groups of processes occur in majority
in lower and middle parts of slope surfaces, located at the
altitude 1000-1100 m a.s.l. with slope inclination 35-55°,
exposed towards west or east; sliding and gravitational accumulation
occur there also. The complete results of investigations
were presented in a graphic form, as computer
graphic programmes were applied.
The above analysis enabled to determine the share of particular
processes in current transformation of the midmountain
subsystem. Similar investigation have never been