ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

The underwater geomorphologic survey based on 180 scuba
diving stations has revealed the existence of several sedimentary
formations situated at a depth of -28/-30 m,
-6/-8 m, -2 m and -1 m. Following an analysis of rock
samples, the surveyed deposits have been classified as beachrock
having Holocenic 14C calibrate radiometric age.
The surveyed deposits can be ascribed to a recent coastal
geomorphologic evolution affecting the littoral environment
and proximal shelf during the late Holocene transgression.
SANDRO DE MURO\ ANGELO DI GRANDE 2,
ANTONIO BRAMBATI 1
& ALBERTO MARINI 3
The Punta Catalina area in post-glacial MageIIanic
evolution Map N. 4/12 of the Geomorphological Atlas
of the Coasts of the Strait of Magellan
(Tierra del Fuego, Chile)
1Dipartimento Scienze Geologiche, Ambientali e Marine,
via E.Weiss 2, Trieste, Italy
2 Istituto di Geologia e Geofisica, corso Italia 55, 95129, Catania, Italia
3 Dipartimento Scienze della Terra, Remote Sensing Laboratory,
via Trentino n. 51, Cagliari, Italy
The results of the coastal geomorphological survey on a
1:50,000 scale map mainly concerning marine and transitional
terraces of Punta Catalina (Strait of Magellan - Patagonia)
are reported. The information mainly concerns
mapping and the on-field survey during Italian expeditions
(in 1992, 1994 and 1995), co-ordinated by the Dipartimento
Scienze Geologiche, Ambientali e Marine of the University
of Trieste within the Programma Nazionale di Ricerche
in Antartide (Pnra). In the framework of the Pnra, updated
studies on the coasts of the Strait of Magellan, have
been mainly aimed at the knowledge of the present littoral
dynamics and at the detailed cartography of morphological
units of the coastal belt (collection of geomorphological,
morphostructural, stratigraphic, micropaleontological and
sedimentological data, study of active cliffs, paleocliffs, dunes,
etc.).
The primary objective of the present research is the mapping
of the more recent marine and transitional terraces.
The aim is to publish an Atlas accompanied by about 12
geomorphological maps (of which this map is the fifth
example) topographically based on 28 Chilean LG.M.
1:50,000 scale maps of the area between Punta Dungeness
and Bah'a Incetil (De Muro & alii, 1996a and 1996b; Di
Grande & alii, 1996a and 1996b).
The map is mainly focused on the youngest terraces, from
which orders starting from the present sea-level have been
mapped; they belong mainly to the Holocene.
They are mostly depositional flat bodies; at times, however,
they are part of erosion surfaces; on other occasions
they are located, either on glacial erosional surfaces, which
they modify, or they lie on both morainal and/or glacifluvial
and Meso-Cenozoic basements. On the whole, they are
distributed following the present coastline, being genetically
connected to it; in some cases, they present an old
configuration that is different from the present Strait.
The First Order, presently located between 18 and 25m, is
not well represented along the explored and cartographed
coast. Besides, they are difficult to identify, since they link
up landwards with continental terraces of different orders
and the related hydrography network, which is older
(Lower Pleistocene ?). From the textural point of view,
they are made up of stratified sands and laminated pelites,
Holo-Pleistocenic age is hypothesised according to the
stratigraphic position and their relation with analogous deposits
of the Strait of Magellan dated by radiocarbon C 4 C
yr B.P.).
The Second Order concerns terraces between 6 and 11 m;
they are clearly more evident than the previous order, and
even show marine palaeoforms. The deposits are mostly
gravelly and sandy, at times clayey or fossiliferous. Their
age (Holocene) is presumed from their stratigraphic position,
their fauna content and dating by radiocarbon C 4 C
yr. B.P.).
The Third Order (Holocene) is not as clear as in the adjacent
areas, although they represent larger single outcrops
between 3 and 5 m. There can be spotted fossiliferous gravels
and sands.
The genetic similarity of Punta Catalina with the present
configuration of cuspate forelands of Punta Dungeness
and with those related to the past by Holocene terraces is
remarkable. The main aeolian morphology is spread following
the dominant Magellanic wind direction especially
in high -altitude areas.
MARCELO A.T. DE OLIVEIRA
Regressive alcoves, gully head extension
and gully integration
Departamento de Ceociencias, Cfch,
Universidade Federal de Santa Catarina, Campus Universitario,
Trindade, cep: 88.040-900, Florian6polis, SC, Brazil
The extension and integration of gullies on unchannelled
valleys had been studied since 1984 on the Southeastern
Brazilian Plateau. As a result, a conceptual model for gully
erosion evolution was proposed (fig. 1). The model conceives
the existence, at the same hillslope, of two types of erosive
incision: one connected to the main drainage net (I),
the other disconnected (II). With time, both incisions may
integrate into a whole channel, creating a unique gully erosion
system (III). At the moment of the integration
between the distinct incisions, the synergetics of overland
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