ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

The following major tectonic units comprise the presentday
morphostructures in the Caucasus (from N to S) - the
Pre-Caucasian foredeeps, the Greater Caucasian ridge, the
Transcaucasian intermountain depression, the Lesser Caucasian
fold system and the South Armenian-Nakhichevan
subplatform. Now welded together these units (terrains)
were once separated from one another by intervening basins
with oceanic or suboceanic crust.
The progressive elimination of these oceanic areas took
place throughout the Late Mesozoic-Early Paleogene and
completed by the end of the Eocene. Thereafter, further
compression led to deformation, shortening and thickening
of the Earth's crust, the latter process being due to.
underthrusting southern continental blocks beneath the
northern ones. The boundary zones between terrains now
represent belts of increased geodynamics activity where
the intensity of tectogenesis, volcanism and seismicity is
most evident. These zones are also the places of the most
active morphogenesis.
The main positive morphostructural elements of the region,
the Greater and the Lesser Caucasus, are associated with
zones of maximal crustal thickening and thrusting. Their
formation was mainly caused by isostatic uplifting and differential
movements of the upthrusting blocks. The total
neotectonic uplift (since Late Sarmatian) reaches 8-9 km in
G.Caucasus and 5-6 km in. L. Caucasus that implies average
uplift rate -1 and -0.6 mm yr" correspondingly. The
following denudational cutting, therefore, was no less than
4 km for the G. Caucasus and 3 km for the L. Caucasus.
Formation of intermountain depressions can be linked with
frontal parts of the underthrusting plates. Molasse sequences
(up to 5 km thick) accumulating within their limits created
additional isostatic loading resulting in further sinking.
Thus, the amplitude of vertical differential movements in
the Caucasus was more than 10 km, locally even 13-14 km.
The main orogenic phases which form the present-day
structure and relief of the Caucasus have been the Pyrenean,
Attic, Rhodanian and Vallachian, the second and the
fourth being most important. These phases show good accordance
with the interaction between the Arabian and
Eurasian plates and epochs of the Red Sea opening.
JURI] KUNAVER
On morphogenesis of the superimposed valley
of Soca River (Isonzo), Western Julian Alps
Department of Geography, Faculty of Arts University of Ljubljana,
1000 Ljubljana A'Skerceva 2, Slovenia
After Czhoemig, Desio and Melik, who were dealing with
the valley of Soca River (Isonzo) in the first half of this century,
this area still offers some new views on the major gemorphological
development. In the meantime new local studies
were made which have to be taken in account in attempt
for the new improved explanation of the valley morphogenesis.
New geomorphological technics and new views
on neotectonics also help in the explanation of the region.
The present Upper Soca Valley is typical for its composition
of short gorges crossing the geological belts and of
longer valley parts, being paralel or subsequent to them.
The whole valley of Soca River has therefore a typical zig
zag course because it is composed of a succession of many
paralel and transverse valley parts. Each of them has its
own development, with special regard to the initial phase
of development.
The older geomorphological development of this part of
Julian Alps shows a completely different situation in comparison
with the present one. Desio and Melik (1926,
1956) have already supposed the existence of separate consequent
rivers, which in pliocene used to flow directly to
the Adriatic sea.
Beside dry valleys known before some new ones were
found. A system of erosion teracces also explains the geomorphological
history. The dry valleys are just a short transverse
incisions in a nanow and very long monocline or anticline
ridges which are typical for the middle part of the
Soca valley.
The former consequent drainage was of the superimposed
type because of its discordant position to the geological
structure. It is believed that the beginning of uplifting of
the Julian Alps at the end of pliocene and in older pleistocene
and the activation of the Idrija fault line enabled the
older rivers to deepen and accomodate their valleys to the
geological structure. That process has also caused that in a
relatively short time a new valley of Soca River originates
out of many independant and separate paleorivers. The
only exception is the gorge of Nadiza River (Natisore) which
is still a geomorphological enigma. It is supposed that
with the help of river capturing it opened the direct connection
between Friuli plain and the valley of Soca River.
At this interesting locality the gathering of upper Soca waters
was not completed.
YOSHIMASA KURASHIGE
Source of river suspended sediment
after-selective logging in a Headwater Basin
Graduate School of Environmental Earth Science,
Hokkaido University, Kita-ku, 060 Sapporo, Japan
Selective logging was performed from April to June 1992
in the Hiyamizusawa Brook basin (basin area of 0.93 km2)
in Hokkaido, Japan. An unpaved road was at first constructed
in the basin in 1989, and further part of the slope
was cut by bulldozer to carry out logs in 1992. During the
logging in 1992, the sediment cut from the slope was wasted
on the slope, in particular in the hollows. The road
crosses the brook at one site at the lower reach of the
brook, and the road surface water with high content of suspended
sediment flows into the river at the crossing during
a storm event. Accordingly, both wasted sediment fines
(Wsf) and suspended sediment in the road surface
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