ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

include long ridges and isolated esker hummocks as well as
erosional landforms, such as channels, bare-washed rocky
slopes of hills and even gorges crossing water divides.
By aerial photo interpretation, geomorphological and stratigraphical
studies it was possible to determine the age relations
of these systems. The esker chains without a till cover
are the youngest ones, because they cross-cut the other
esker systems. They have been deposited in subglacial
meltwater systems flowing in a fan-like pattern. In the
southern part of the ice-divide they run from WNW to
ESE (equals the flow direction of the meltwater that deposited
the esker chain). In the central part of the ice divide
they turn to a west-east direction and in the northern part
from SW to NE. These meltwater systems were formed
under the marginal zone of the receding Late-Weichselian
ice sheet. The eskers vary in size from over 25 m high gravel
and sand ridges with steep flanks to only a few metres
high stony and gravelly mounds. The sediment is loosely
packed and the walls of the gravel pits collapse readily.
The esker ridges are often separated by distinct erosional
forms, like subglacial gorges, where the meltwater action
has eroded all surficial deposits away from the bedrock.
The two till-covered esker systems predate the latest deglaciation.
The till cover is about 40-70 em thick, and was formed
either during the latest glaciation or during the previous
one. The eskers that were deposited from the
northern or north-northeastern direction, are small, only
5-15 m high, generally continuous ridges. An abundance of
morphological details have been preserved such as steep
ridges and kettles, ice-contact landforms and parallel ridges.
Erosional landforms are gently sloping, elongated depressions,
however frequently covered by younger deposits.
The north-south trending eskers were possibly deposited
during the deglaciation of the second stadial of the
Early Weichseliam deglaciation phase, or may represent
the early phase of the Late-Weichselian deglaciation with
the ice margin still located far beyond the region.
The till-covered eskers deposited from northwest to
southeast are the oldest ones. They consist of massive, over
25 m high erosional remnants of formerly coherent esker
ridges. They are clearly reworked by glacial flow. The glaciofluvial
material is compacted and coarser than that in
younger eskers. The till cover is often lacking on the sum-
mits. The erosional landforms connecting the separate ridges
are gentle and visible in the field as elongated valleys
and depressions in the large-scale morphology. These systems
were probably formed during the deglaciation of the
first stadial of the Early Weichselian. The dates of the optically
stimulated luminescence suggest that some of them
may even have been formed during the Late-Saalian deglaciation.
MAURICE JULIAN
Mouvements de terrain en zones d'extraction
et d'amenagement (France meridionale)
Universite de Nice-Sophia-Antipolis, France
En fonction d' activites diverses, en milieu urbain et nonurbain,
mais toujours du fait de l' action humaine, dans des
mines et des carrieres ou sur des chantiers de construction
et de travaux publics, un assez grand nombre de mouvements
de masse se sont produits recemment, dans la region
Provence-Alpes-Cote d'Azur ; ils ont eu des effets dommageables,
sans occasionner, aune exception pres (Saint-Cyrles-Lecques.Var),
de pertes de vies humaines.
Sauf Ie cas du Cap Sicie, pres de Toulon, ou la localisation
d'une station d'epuration en bas d'un haute falaise, imposee
par Ie trace anterieur du collecteur, met en jeu une dynamique
naturelle pre-existante, les autres cas correspondent
a des modifications des pentes de versants en fronts
de carrieres d' extraction (bauxite du Thoronet, materiaux
de construction, comme aMougins) ou dans des chantiers
de remodelage urbain (anciennes carrieres d' argiles a
Saint-Henri de Marseille). D'autres instabilites sont dues a
des terrassements (la Trinite, pres de Nice). Dans tous les
cas, ces pentes non etayees subissent des effets de traction,
auxquels s'ajoutent des pressions hydriques, en raison des
nouvelles Iacilites d'infiltration. Leur stabilisation necessite
des travaux parfois tres couteux (galerie drainante du
Thoronet).
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