ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

Such a lack of finds can only be explained by changes in
the ancient morphology; rivers flowed in a several meters
deep engraved floodplain (fig. 1) the alluvial sediments filled
up the engraved valleys as a consequence of subsidence
and change in climate during the High Middle Age (fourth
to eighth centuries AD) (fig. 2).
ALES SANDRA GIOVANNINI l , NASSER ABu-ZEID 2
& GIANDREA ALLEGRI 3
Application of an integrated methodology in the
characterisation and analysis of the fluvial morphology
of paleo-riverbeds in the eastern lowlands of Ferrara
(Northeast of Italy)
1 Dipartimento di Scienze Geologiche e Paleontologiche,
Universita di Ferrara, c.so Ercole 1° d'Este 32,44100 Ferrara, Italy
2Istituto di Mineralogia, Universita di Ferrara,
c.so Ercole 1° d'Este 32,44100 Ferrara, Italy
3 via Mazzini 29, 48026 Russi (RA), Italy
This work deals with the application of an investigation
methodology to characterise the mechanism by which two
old tributaries (paleo-riverbeds) of the Po River were formed.
These are located to the SE of Ferrara, along the Voghenza-S.Vito-Ostellato-Spina
and Finale di Rero-Migliarino-Migliaro-Massa
Fiscaglia alignment and are known as
Padoa-Eridano (VII-VIII A. C.) and Volano (Roman epoch-Upper
medieval period).
The applied methodology aims at integrating the geomorphologic
studies with recent geoelectrical measurements
that included the execution of several Vertical Electrical
Soundings (Ves), a number of profiles (Dipole-Dipole)
and many auger holes drilled to a maximum depth of
10m over the two sites.
Analysis of these data led to the identification of the old riverbeds
main characteristics in terms of principal channel
pattern, delimitation of their levees, individuation of the
flooded planes, determination of paleo-channel thickness
and localisation of the interdigitating zones.
The resulting geomorphological conceptual model for the
studied areas proved to be complex. Although many pieces
of information have been obtained, a complete view of the
relative evolution of the dynamic processes that led to the
formation of these areas were not totally resolved. For this
reason a resort to statistics have been made through the
employment of the geostatistical techniques (Kriging). The
advent of such technique is to assist in the construction of
more detailed conceptual models taking into consideration
not only the probability with which a certain parameter
would exist, but also the error committed in its extrapolation.
To do this, all data were analysed by constructing several
experimental variograms describing the spatial distribution
of paleo-riverbeds characteristics (e.g. subsurface
heterogeneity distribution). The obtained models were
180
further compared to known theoretical models, then the
variogram parameters (i.e, sill and range of influence) of
the model that resulted in the best fit to the experimental
data was used as input for the construction of bidimensional
maps (detailed geomorphological map). In this way,
the spatial variation of each parameter was investigated,
hence ambiguities regarding the lateral extension of these
parameters where minimised, if not completely resolved.
This was made possible through the construction of maps
demonstrating the standard deviation of the analysed parameter
(thickness and resistivity), thus reflecting the
amount of estimated error.
Finally, all the obtained results where used to construct a
detailed geomorphological map of the two sites. Such a
map show the probable limits of the paleo-riverbeds as
well their mutual relationships which were of help in the
reconstruction of their geomorphological development.
Last but not least, the research demonstrated that the application
of such an integration methodology, characterised
by a good cost/benefit ratio, could be of extreme utility
for the investigation of areas where their is an urgent
need to define and delimit the probable extension of buried
structures such as paleo-riverbeds (e.g, protection of
groundwater from contamination). Moreover, these studies
are believed to be of paramount importance to land
planing organisations, especially for those engaged to the
planning of lowland areas (e.g, the Padana Plain).
CHRISTIAN GIUSTI
.Aplanissements etages dans Ie sud du Massif Central
(France)
Ura 1562, Cnrs, 29, boulevard Gergovia,
67037 Clermont-Ferrand cedex 1, France
Dans Ie sud du Massif central fran ais (Aveyron, Herault,
Tarn), a la charniere des mondes hercynien et alpin, les
contrees s'etendant des confins du Sidobre a l'Escandorgue
et du sillon Jaur - Thore aux vallees du Dourdou, du
Rance et du Dadou constituent une seule et m me unite
geomorphologique: la Montagne.
Du Somail aux Monts d'Orb et du Lacaunais aux Monts
du Haut-Dourdou, Ie plan d'organisation des formes
majeures du relief est en effet remarquable de coherence
puisque, en depit d'innombrables nuances Iiees a la complexite
du canevas structural, partout s'observent les vestiges
de deux surfaces d' aplanissement etagees et deformees:
la haute surface Sl et la basse surface S2' Parce que les traces
respectives des deux aplanissements se suivent sur des
kilometres independamment de la nature du substrat dans
lequel elles s'inscrivent, l'essentiel est bien moins d' opposer
les formes para-appalachiennes de la Zone axiale aux
formes ortho-appalachiennes deson flanc septentrional,
que de distinguer les contrees OU l'aplanissement S2 regne