ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

also to the intense erosive action of the sea wave, we were
able to find out the areas with higher activity of mass movements
by comparing the topographic map of 1994 with
those of 1938. By means of the utilisation of 3D modelling
software we were able to recognize the areas where the topographic
differences between the two maps were largest.
In order to taking into account the different survey methodologies
between 1938 and 1994, only the areas where topographic
differences were greater than the tolerance value
found, were included in our interpretation.
It was also possible to evaluate the mean rate of cliffs recession
in the studied period, the coastline variation and
the order of magnitude of the volumes of material involved
in erosive and landslide phenomena.
CHEBO K. ASANGWE
Tidally-induced prograding mudflats along
the Ondo coast of Nigeria
Geomorphology Laboratory, Department of Geography & Planning,
Faculty of Environmental Sciences,
University of Lagos, Lagos, Nigeria
The Ondo coastal area has its own peculiar geomorphic
character when compared to other parts of the Nigerian
coastline. It is the only part of the 800 km Nigerian coastline
revealing muddy consistency on the marine and estuarine
environments of deposition. The structure-free Ondo
coastline with very low topography where areas less than I
m are common presents a scenario of coastal flooding and
saline water intrusion through tidal movements. This has
been known to have far-reaching socio-economic implications
on the people particularly with the pro-gradation of
mudflats, making life extremely difficult in this fast degrading
locality.
This paper examines the littoral process of tidally induced
sediments dispersal in the progradation of mudflats on the
barrier beaches and islands of the Ondo coast in Nigeria.
Sediment drifting and deposition by the low energy, gentle
waves in the estuarine environment of Molume and Awoye
has evolved extensive muddy features on the active barrier
beaches.
Laboratory analysis of collected samples revealed that sediments
of the study area are of Ferrigenous clastic category
with predominantly quartz consisting of not less that 95 %
composition in most samples. The analysis further revealed
clay-rich minerals and silt grade sediments of detrital origin,
implying long distances of the source of sediments to
this estuarine environment.
It is envisaged that the management of the Ondo coastal
environment characterised by fragile geomorphic features
will be greatly enhanced with focus on the sedimentological
analogue of the area.
58
ALESSANDRA ASCIONE & ALDO CINQUE
Tectonics and erosion in the long-term relief history
of Southern Apennines (Italy)
Dipartimento di Scienze della Terra, Universita di Napoli Federico II,
largo S. Marcellino 10, 80138 Napoli, Italy
The Southern Apennines fold-and-thrust belt resulted
from compressional tectonics events occurred between 14
and 1 Ma. It has a maximum elevation of 2,000 m and an
average width (measured from the Tyrrhenian coastline to
the inner border of the former foredeep basin, nowaday
filled and emerged) 100 km. The height to lenght ratio (log
H/log L) of the whole chain is 0.66; this value is exceptionally
low compared with other recent orogenic belts of the
world (Ahnert, 1984).
Within the belt, the relief energy is generally high, the local
relief reaching several hundred metres within unit-areas of
1 to few km across. Only little of the total amount of the
local relief represents the direct response to surficial deformation
accompaning the belt accretion. Indeed, both synorogenic
aggradation (filling-up of perched basins) and/or
phases of prevailing erosion, reduced and smoothed the relief
generated by compressional tectonics.
Post-compressional events dominated by extensional
block-faulting generated tectonic relief only in localized
areas, most of which are located in the inner belt. In particular'
fault scarps drew the Tyrrhenian coastline between
Late Pliocene and Early Pleistocene, and framed subsiding
depressions between Early and Middle Pleistocene.
Among the relief generating factors, rivers downcutting in
response to vertical tectonic movement played a major role.
Indeed, vertical tectonic movements (both absolute and
relative) exerted an indirect influence on local relief generation
by controlling rates and magnitude of fluvial downcutting.
The available geological and geomorphological data allow
to identify the time span ranging from Middle Miocene to
Late Pliocene pro parte as the one in which reduction of
the tectonic relief occurred in the inner belt. In particular,
from Middle to Late Miocene relief reduction was favoured
by the low elevation of the present inner portion of the
thrust belt which, during that time interval, coincided with
the outermost portion of the wedge. In the following period
(from Late Miocene to Late Pliocene), although the
thrusting had migrated towards the NE, relief reduction
still prevailed on relief increase. Indeed, the elevation increase
affecting the inner belt was compensated by the advance
of the foredeep basin coastline and in consequence
the mean river gradients were still low on the western slope
of the wedge. Relief reduction by erosion was caused
both by downwearing of the divides underlain by highly
erodable clastic formations (at that time outcropping much
more extensively than at the present time) and by karstic