ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

Serra do Geres (NW Portugal). This mountain is a granite
range with a maximum altitude of 1545 m a.s.l. (fig. 1) and
is characterized by a complex plateau where bare-rock outcrops
are dominant. In this plateau, the interfluve of Outeiro
do Passaro was studied in detail and a geomorphological
map at 1:5 000 was presented. Such a detailed study
allowed the identification of small accumulations of coarse
sand and granules which present a superficial layer of
about 1cm depth formed by homometric granules of
quartz and feldspar. Under this layer, the material is more
heterometric and sandy-silty with a higher organic matter
content. The sedimentological analysis of the deposits and
the comparison of the aspect of the micro-accumulations
with a map showing the anemomorphic deformations of
small shrubs of Cbamaespartium tridentatum and Calluna
vulgaris allowed an hydro-aeolian interpretation for their
genesis. This means that both wash and wind erosion seem
to be the main processes involved in the evolution of the
observed features. A first accumulation phase of aeolian
origin is necessary, followed by the deflation and washing
of fines, which give origin to a lag-surface about one-granule-thick
at the surface of the accumulation. Although,
for the thickening of the lag-surface, posterior episodes of
accumulation over it are needed. After these smaller accumulation
events, deflation and washing take place again,
contributing to the coarsening of the superficial layer. This
would explain the sedimentological characteristics of the
superficial layer (Figure 2). In what concerns to the sub-su-
o 50km
L...-.-J
FIG. 1 - Location of the Serra do Ceres (1) and Serra da Estrela (2) in
Portugal.
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perficial layer, their sedimentological characteristics seem
to be more closely related to the first accumulation event
and by posterior fine-sand, silt and organic matter contamination.
The importance of needle ice in the genesis of
the grain-size differences between the two layer is also
being studied.
The author is now developing a similar study in the Serra
da Estrela (fig. 1), which is also a granite mountain with
plateaus between 1500 and 2000 m a.s.l. The poster will
present the studies done in the Serra do Geres and Serra
da Estrela and a comparison of both evidencing the main
similarities and differences concerning the occurrence of
hydro-aeolian processes.
FIG. 2 Hypothesis for the genesis of micro-accumulations against
obstacles
HEATHER A. VILES
Disturbance and the dynamics of rocky coasts
School of Geography, University of Oxford, Mansfield Road,
Oxford, OXl 3TB, England
Rocky coasts composed of cliffs and coastal platforms provide
an ideal opportunity to study the dynamics of biogeomorphological
systems, and the influence that various disturbances
over different timescales have upon them. Specific
questions of interest are: how are changes in biological
systems reflected in geomorphological change (and vice
versa)?, and to what extent are extreme natural events important
to the biogeomorphological evolution of rocky
coasts?
The Glamorgan Heritage Coast in South Wales provides
an ideal site in which to investigate these questions. Liassic
limestone cliffs of great instability are fronted by limestone
coastal platforms dissected by a complex range of microtopographies,
and populated by a suite of sessile and mobile
organisms. Data on erosion rates, population dynamics,
microenvironmental conditions, climatic variability and
anthropogenic disturbances, allied with simple modelling
techniques, provide a clearer picture of the coastal biogeo-