ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

grass plots in the dolines where animal grazing used to be
intenzive, The stamping and natural dunging led to a
uniform grass assotiation, Pasturing and animal grazing
had been preceded by deforestation, having led to the formation
of secondary grass assotiaton,
This paper presents the analyzing a few more various ecological
factors and their effects on development of doline
morphology in Aggtelek Hills.
MAURIZIO BARBIERI 1, MARIO BARBIERI 1,
FRANCESCA CASTORINA 1, MAURIZIO D'OREFICE 2 ,
GIORGIO GIARDINI 2 & ROBERTO GRACIOTTI 2
Geomorphological features and petro-structural and
geochemical analyses of vulcanites found in the centralwestern
part of the Piana del Cavaliere, L'Aquila, Italy
1Dipartimento di Scienze della Terra, Universita di Roma La Sapienza,
p.le AIda Mora 5,00185 Roma, Italy
2 Servizio Geologico Nazionale, via Curtatone 3,00185 Roma, Italy
This paper shows the preliminary results of a series of geomorphological,
petro-structural and geochemical studies
carried out in the central-western part of the Piana del Cavaliere
(Oricola, AQ), as part of the Geomorphological
«Tagliacozzo» Sheet n? 367 research. The area concerned
is geographically located in a wide tectonic depression,
midpoint between two different paleogeographical domains,
separated by a section of the «Olevano-Antrodoco»
tectonic line.
Inside the Piana del Cavaliere, lake-type deposits are generally
found, limited in their upper part by a sub-horizontal
erosion surface, dried up by small valley formations with
steep slopes, often subjected to solifluction and by minor
landslides. Particularly interesting are the piping phenomena
causing pseudokarstic formations along the valley carvings.
Nearby the Bosco di Oricola area, by a process of erosion,
volcanic deposits cover the lake sediments. Two main systems
can be distinguished in these deposits: lithologic vulcanites
and incoherent red vulcanites. The most lithoid
part appears as a canalized body, within a preexisting small
valley, cut into the lake deposits. Following selective erosion,
which in time has created an inversion of the relief,
today the vulcanites are found along a ridge, above the more
easily erodible surrounding relief, yielding sub-horizontal
tabular forms in contrast with the rapid slopes shaped
within the lake deposits.
The present geomorphologic shape and the contrast between
the lithologic volcanic complex and the lake sediments
below have caused numerous gravitational phenomena
around the edges of that formation, as by the presence
of large rocks, placed below as a result of a roto-traslational
movement.
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On the other hand, the incoherent vulcanites is the backbone
of a series of hills found between Highway A24 and
Via Tiburtina, The smaller hills are perfectly conic, giving
the landscape its characteristic feature. From a mineralogical
point of view, all the lithologic vulcanites are characterized
by the presence of leucite, pyroxene, biotite and glassy
scoriae. The petro-structural analysis suggests petrogenic
characteristics similar to scoriae tuff (with 25 < An <
40) similar to tephritic-leucititic litotype, very rich in carbonatic
clasts. Radiometric determinations of the area carried
out by Bosi & alii (1991) suggest an age of 0,531 Ma.
The Strontium isotopic ratios were determined on some
vulcanite samples lacking secondary calcium carbonate.
The results (87Sr/86Sr equal to 0,71087 ± 0,00002) fall
within the Quaternary magmatism variation interval of the
tyrrhenian zone, but do not seem to be related to any of
the provinces mentioned in the literature. Therefore, we
infer, together with Bosi & alii (1991), that this volcanic
zone is the result of an independently developed local
magmatism.
CARLO BARONI
Geomorphological evolution of the Victoria Land
coastal area since the Last Glacial Maximum
Dipartimento di Scienze della Terra, Universita di Pisa,
via S. Maria, 53, 53126 Pisa, Italy
During the last glacial maximum (Lgm, stage 2) the Antarctic
ice sheet expanded and the surrounding ice shelves
became marine based and advanced on the sea floor covering
wide portions of the continental shelf. The Ross Ice
Shelf advanced extending in the Ross Sea embayment,
even though the most advanced position of its grounding
line is still matter of discussion. Radiocarbon dates of marine
organisms that lived below the floating ice shelves that
surrounted the marine based ice sheet supply more and
more information on the grounding line position during
Lgm and the following retreat phases.
The outlet glaciers that drain the ice sheet interior and the
alpine glaciers fed by local neves advanced and thickened
in the coastal area reaching several hundred metres above
the present sea level (up to 400-500 m at Terra Nova Bay).
Several reconstructions of late Wisconsin longitudinal glacier
profiles are based on the distribution of glacial drifts
and erratics deposited during the Lgm as well as on geomorphological
evidence of glacial erosion. They document
the maximum level of glacier surfaces and allow us to depict
the Lgm morphology of the area.
The glacial retreat that followed the Lgm is the last big
geological and environmental event that characterized the
landscape evolution of the Victoria Land coastal area. Retreating
ice isolated wider and wider rocky areas at the
head of embayments reached by the rising sea. Penguins
nested in those ice free areas and reoccupied the Victoria