ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

Swedish-Russian expedition «Tundra Ecology-94» along
all arctic coast of Russia have allowed to find some regularities
of spreading of modern geomorphological processes
in Arctic tundra and to determine their intensity.
The most characteristics of tundra relief are lakes having
essential influence on relief. Study of lake basins structure
and dynamics was carried out on the basis of research of
loose sediments by a complex geomorphological and paleogeographical
methods. Large-scale geomorphological
maps of Kara Sea islands (archipelagoes of Izvestiya TsIK,
Arctic Institute, Sverdrup and other) and inaccessible places
of continental coast are made for the first time. Radiocarbon
dating of peats and bone rests of Quaternary mammals
was widely applied.
Erosion, abrasion, rockfall and talus processes play the
most appreciable role in modern relief transformation of
arctic islands. On low-lying sites of coasts are active also
eolian processes and suffosion. The most important peculiarity
of localization of exogenic processes in Arctic is
their high intensity on sites of spreading of underground
ice (Central Yamal, Nothern Yakutiya, New Siberian
islands). Ground ice slump and the development of thermokar
and thermo-cirque play here a fundamental role.
They proceed here in so close interaction with erosion and
solifluction, that it is expediently to allocate uniform process
of thermodenudation in similar regions. Thermokars
are the circularitical depressions in coastal breakages. They
appeared here as a result of underground ice thawing. Frequently
for their appearence amd subsequent transformation
in ground ice slump a presence of a few sentimeters of
ice layer may be enough (Sverdrup island, Russian island).
Human activity (building and tramsport mainly) raises
strongly the intensity of geomorphological processes in natural
conditions favorable for their development (ground
ice slump - 4 m/year or 50-80 m'zyear and erosion - up to
30 m/year on CentraIYamal;' thermoerosion - 20-30
m/year on Preobrazhenye island in the Laptev sea).
The obvious tendency of reduction of the area water reservoir
comes to light due to overgrowing and descent for the
majority of investigated territories. The drain process goes
with speed about 0.01 smi/year (Central Yamal). The
majority of lakes on low (5-45 m) accumulative terraces have
a residual origin, the thermokarst role in their formation
is insignificant.
The determining factor for geomorphological processes
development in high Arctic is the substratum tipe (mainly
its ice-cover). The mechanism and speed of erosion, abrasion,
slumping and other in a little ice-covered rocks do
not differ practically from the same processes in more
southern areas without eternal permafrost. The presence of
winter rest periods, close dependence of processes speed
on weather conditions during the warm period of a particular
year, high correlation of processes with each other
are characteristic. Because of high ice-cover of loose sediments
composing of arctic low land, the general denudation
intensity on the nothern plains is more than in mountain
regions.
A combination of several favorable conditions is necessary
for especially intensive development of processes, that is
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observed rather seldom, and consequently the high speeds
of processes in natural conditions are observed on rather
limited sites. Opposite, the acceleration of geomorphological
processes near to arctic settlments is an ecological problem
now and can completely change the relief aspect of
these sites.
GHEORGHE T. ROMANESCU
L'evolution morphohydrographique du delta du Danube
pendant Ie Quaternaire en fonction des oscillations
du niveau de la Mer Noire
1Deparrement de Geographie, L'Academic Roumaine, la filiale Iaoi, 8,
Bd. Copou, 6600 Ia''i, Roumanie
En analysant les series des transgressions et des regressions
qui ont influence Ie territoire actuel du delta du Danube
on a essaye de reconstituer les paleodeltas et les paleoriviere&
qui se sont formes pendant 1'intervalle compris entre Ie
Pleistocene inferieur et Ie Holocene.
On remarque l'existence de deux hauteurs predeltaiques
(Letea et Caraorman) qui ont fonctionne comme barriere
pour les sediments transportes par Ie Danube. En meme
temps ces deux temoins d' erosion constituaient une ligne
de littoral qui separait une zone occidentale lagunaire et
une autre orientale, marine. Cette ligne du littoral situee
entre Jibrieni et Ie promontoire Dunavse presentait sous la
forme d'un cordon littoral de type fleche,
En analysant plus de 100 forages qui ont ete realises dans
Ie cadre du delta du Danube nous avons mis en evidence
deux couches de tourbe: la premiere situee a des protondeurscomprises
entre 25 m et 35 m, seulement Ie long du
bras Sf. Gheorghe; la deuxieme, situee a des profondeurs
comprises entre 3-10 m, etant presente au long du bras Sf.
Gheorghe et aussi au long du bras Sulina.
Les donnees obtenues confirment Ie fait que Ie plus vieux
bras du delta du Danube c'est en meme temps Ie plus meridional
(Sf. Gheorghe), pendant que Sulina, Ie bras median,
est Ie plus recent.
L' evolution du territoire deltaique est mise en evidence par
rapport aux mouvements eustatiques specifiques pour la
mer Noire mais aussi par rapport a ceux de la mer Mediterranee,
NIKOLAI N. ROMANOVSKII
Icing formation and topography in the valleys
of the East Siberian Mountains
Geocryology Department, Faculty of Geology, Moscow State University,
119899 Moscou, Russia