ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

led with debris material of various origins, for a total volume
of approximately 15,000,000 m'. along the seabed
down to the 15 m bathymetric line.
The main effects on the morphologic and dynamic features
of the studied area, deriving from the creation of the new
harbour could be synthetized in the following way:
- artificial progression (reclaimed area) of the shoreline of
aup to 800 m in front of the urban settlement of Pra, where
seaside resort and shipyards were formerly located;
- progression of Veltri beach (50/80 m ), to the west of
the harbour area, and consequently the raising of the seabed
in this area, due to the prevailing long shore downdrift
from west to east;
- recession of Pegli beach on the west side of the Varenna
Stream mouth ( to the east of the arbour area ) and progression
on the eastern side;
- landfill of residual chanell between the embankement
and the former Pra shoreline by the sediment supply of some
small rills.
MAME DEMBA THIAM
Cinematique des fleches sableuses de bordures
lagunaires: cas des lagunes de Joal et de Mbodiene
(Petite Cote, Senegal)
Departement de Geographie, Universite Cheikh Anta Diop,
b.p.: 206, Dakar, Senegal
Le Senegal compte trois systemes lagunaires exclusivement
situes dans la partie meridionale de la zone cotiere appelee
Petite Cote. Seules celles de Joal [14° 05' 30" N - 16° 48'
00" W] et de Mbodiene [14° 15' 00" N - 16° 52' 20" W]
sont bordees par des cordons sableux qui sont d'importance
assez inegale,
Le suivi de la dynamique de ces unites geomorphologiques
permet de comprendre les changements qui affectent cette
partie basse et sableuse du littoral senegalais, La demarche
employee met en exergue, de maniere comparative, le
comportement de deux environnements lagunaires qui ne
sont pas soumis au meme regime hydrologique, En effet, il
existe des differences quant aux facteurs - agents qui commandent
les modifications. II s'agit des points d' attache rocheux,
des apports d' amont, de la configuration cotiere
par rapport a la derive littorale, des actions eoliennes et
anthropiques, etc
A l' aide de divers documents iconiques, (cartes anciennes,
photographies aeriennes et images satellitaires), la cartographie
des situations a permis de restituer des valeurs qui
montrent des comportements faciles acomparer.
Un suivi sur le terrain durant quelques mois aide aussi ala
validation des constats qui resultent du suivi adistance. Ce
qui confirme que cete methode, peu couteuse peut servir a
renforcer la disponibilite de l'information utile aux decideurs,
en vue d'une meilleure politique d'amenagement du
milieu littoral
374
MICHAEL F. THOMAS \ M.B. THORP 2 & J. McALISTER 3
Morphogenesis in lowland equatorial environments
A study of weathering processes and the origins of
«white sands» in Kalimantan
IDepartment of Environmental Science, University of Stirling,
Stirling, FK9 4LA, UK
2Department of Geography, University College, Bellfield,
Dublin 4, Ireland
3School of Geosciences, Queen's University, Belfast, Bt7 Inn, UK
Studies of weathering processes and of associated alluvial
sediments in lowland, Kalimantan offer insights into
morphogenesis under perhumid, tropical conditions. A discontinuous
apron of so-called «white sands» forms a distinctive
sedimentary environment around the granitoid
landmass of western Kalimanatan, and similar sediments
are found in other Equatorial areas. They are associated
with alluvial terraces and sandy, coastal plain sediments.
Many such sedimentary formations appear to be Middle or
Late Pleistocene in age, and may reflect phases of more
seasonal climate, during which the forest cover on eroding
slopes degraded to more open, savanna and deciduous
woodland communities. In so far as these periods are
thought to have coincided with ice advances in the Polar
regions, many white sand terraces may also have formed
on extensions of alluvial floodplains seawards during low
sea levels. Similar white sand formations on cratonic surfaces
were ascribed by Fairbridge and Fink! to the results of
repeated wet-dry climatic oscillations during the Quaternary.
These sediments appear to be very thoroughly leached,
particularly of Fe, and to be mainly quartz, but gibbsitic
clays are also found intercalated with the sands.
Although associated with hydromorphic conditions, these
sands may also show down profile complexing of organic
matter and some minerals including Au. Although Fe staining
is seen in places, they are depleted of Fe and water
passing though the white sands generally does not precipitate
Fe 20; in oxidising conditions.
Similar white sand formations have given rise to much discussion
by pedologists, concerning the possible transformation
of ferrallitic soils (oxisols) into podzols (spodosols).
It is clear that while bauxitic residues appear to form the
ultimate weathering stage in many well drained and seasonal
forest environments, where Al is retained but Si is lost,
in Equatorial areas there is a tendency for Al to be lost
along with Si, creating yellow-red tropical podzolic soils,
even beneath well drained interfluves. The deep profiles
formed are also associated with massive fluxes of clay and
Fe down profile, creating a quartz-rich sandy topsoil, over
crystalline rocks.
The present study was undertaken in lowland Kalimantan,
over undulating (demi-oranges/meias laranjasi Cretaceous­
Tertiary igneous rock terrain, associated with extensive