ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

CLAUDIO A. CARIGNANO & MARCELA A. CIOCCALE
Landscapes antiquity of the Central Sierras Pampeanas
(Argentina):
geomorphic evolution since the Gondwanas times
Universidad Nacional de Cordoba
Conicet, Duarte Quiros 46, 5111 Rio Ceballos, Cordoba, Argentina
This paper discusses the significance of relict landforms
eroded on Precambrian, Paleozoic and Mesozoic rocks of
the Sierras Pampeanas (Argentina), within the framework
of the Gondwana evolution. The Pampean belt belongs to
a complex collage of cratonic blocks, brought together
along the southwestern Gondwanaland margin in late Precambrian
to early Paleozoic times. The geomorphological
evolution of the Central Sierras Pampeanas is analized
within the geological framework of southern portion of
South America during Mesozoic and Cenozoic times. This
masif permanently underwent subaereal denudation since
at least Triassic times.
The erosion surfaces which have successively levelled the
relief are identified by using geomorphological, geometrical
and sedimentological criteria. The reconstructed morphogenetic
evolution proceeded as follows.
During Jurassic times a long period of tectonic quiescence
and predominantly humid tropical climate enabled the
progressive elaboration of a broad surface. The ocurrence
of corestones, bornhardts, rocking stones and deep
. weathering profiles are interpreted as residual forms of
that surface.
The late Jurassic-early Cretaceous transition was marked
by continental rifting and the surface degradation under
arid and semiarid climates.
During the mid-Cretaceous a second surface was generated;
some remnants are preserved on weathered basalts. Later,
that surface was eroded during the upper Cretaceous.
From uppermost Cretaceous to Lower Eocene times a
third planation surface was developed under humid climate.
It was further worn during the Eocene-Oligocene.
A fourth planation surface developed during the Miocene.
Thick and mature calcretes remain as evidence of a long time
stability.
Due to the faulting and Pampean uplifting during the last
10 Ma almost all surfaces were broken and tilted. Two late
Cenozoic minor planation surfaces were also identified.
The Sierras Pampeanas planation surfaces are correlated
with the Eastern Brasil ones.
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LUIGI CAROBENE, MARCO FIRPO, MAURO PICCAZZO
& MARINO VETUSCHI ZUCCOLINI
Raised Quaternary coastal features along the Ligurian
Sea passive margin from Genova to Savona (Italy)
Dipartimento di Scienze della Terra, Universita di Genova,
corso Europa 26, 16143 Genova, Italy
The morphology and deposits linked to the action of the
sea during the Quaternary period in Liguria have been the
object of study since the last century, by IsseI (1883) and
then Rovereto (1923). These studies, like those of other later
Authors, provided detailed, well localized descriptions.
There are also more recent studies, but they lack adequate
cartographic support. Our objective was thus to present
the results of surveys and morphological studies carried
out by us in recent years along the coast between Genova
and Savona, on a 1:25,000 scale Map showing forms created
by uplifting.
The coastal tract we chose is particularly interesting as it
formed being part of a passive continental margin with a
prevalent uplift of this sector during the Pliocene and Quaternary
periods. The mapped forms are thus evidence of
ancient sea-levels stand due to the interaction of uplift and
eustacy. The objects mapped are the forms and deposits of
marine origin which we see today as relics, where erosion
may have removed all or part of the original deposits and
where sedimentation, on the other hand, may be masking
the original morphology. These factors have made both interpretation
and representation difficult; furthermore, the
lack of datable deposits is an obstacle to correlation.
The legend used to explain the information about the
forms and any marine and/or continental cover due to
stands and fluctuations of the sea level is deliberately limited
to descriptive elements. The symbols define the extent
of the terraced surfaces and morphological limits, elements
that are closely connected with the environmental conditions
of formation and with subsequent remodeling. In
particular, the nomenclature of the relic forms includes the
inner margin and outer edge symbols of the terraced surfaces,
which represent the key moments in the marine
morphogenetic phase. The symbols describe the various
forms corresponding to the more or less preserved relics of
terraces of various size observable along the ridges descending
seaward.
The marked presence of tracts of sub-horizontal ridges
obliged us to develop a criterion for the mapping of relic
forms that are heavily degraded but still recognizable as
terraced surfaces. Interpretation of these forms also took
into account lithology and geological setting, which is very
complex in this area.
Separately we also mapped low gradient terraced surfaces
caused by marine and continental deposits covering and
masking marine abrasion platforms. In some cases evidence
of these can be found on scarp slopes close to the current
shoreline. Lastly, we also marked recent small sized
coastal plains delimited by the foot of the valley sides.
They sometimes present one or more orders of fluvial terraces.
The simplified topography (thalwegs, contour lines,
elevations) also includes recurrent altimetric culminations
linked to the more evident forms. The Map is thus a basic
tool for making morpho-stratigraphic correlations and evaluations
of tectonic movements and the uplifting of the zone
in the Quaternary period. Examination of the Map
shows there was a high degree of erosion after the formation
of the terraced surfaces, thus giving the area its present
morphological aspect.