ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

marine succession ranging in age between Lower Cretaceous
and Neogene (Kwanza Basin succession). Still uncertain
is the exact age of the youngest, regressive terms of
this succession in the onshore portion of Kwanza Basin
(Luanda formation), which have been dated by different
authors between Lower Miocene and Pliocene.
The higher portion of the 50-170 strip (above 90-100 m
a.s.l.) is a planation surface to be interpreted as the result
of pedimentation processes. Due to differences in the bedrock
resistence, dip of strata and the presence of ancient
faults, this planation surface (hereinafter named Terrace I)
includes gentle cucsta-like reliefs and fault-line scarps. The
associate deposits are represented by a discontinuous
blanket of alluvium (siliceous sands and conglomerates up
to a dozen meters thick) which was fed by streams eroding
the main escarpment of the Angolan margin. On top of
these alluvial deposits is sometimes preserved a truncated
laterite profile. A younger and more extensive cover is represented
by few meters of finely laminated red sands which
can be ascribed to later phases of reworking and
weathering of the materials exposed on the planation surface
(former alluvial cover and/or siliciclastic formations of
the Neogene substratum). Where the above mentioned covers
lies on calcareous terms of the Cretaceous-Neogene
succession, the planation surface appears punctuated by
very large closed depressions (up to 3 km across and 20 m
deep) due to localized chemical downwearing (dambos).
A first phase of dissection of Terrace I is witnessed by a series
of hanging rivery valleys that are few tens of meters
deep, have gentle flanks and very low longitudinal gradients.
Some of these incisions appear markedly oversized
with respect to their present discharge because most of
their catchment area was pirated by other rivers (Kwanza
and Bengo) during the final, deep dissection of the surface.
The base level that controlled the first phase of Terrace I
dissection is represented by remnants of an ancient marine
abrasion platform (Terrace II) that occurs between 50 and
60 m a.s.I..and carries a thin, discontinous cover of fossiliferous
litoral sands followed by fluvial deposits. The coastal
cliff that bounds the Terrace II are locally cut by a
younger order of marine terraces between 15 and 20 m
a.s.l. (Terrace III). Along rocky promontories, it consists of
narrow and discontinuous remnants of a wave-cut
platform with associated fossilieferous beach deposits,
whilst it is represented by progradational fluvio-marine bodies
in front of some river mouths.
As the fossils we collected on the Terraces II and III have
little chronological value and, moreover, no numerical dating
is at the moment available, it is not possible to precisely
constraint the ages of the various orders of terraces we
have described above. Neverthless, the results of our investigation
coupled with a carefull reinterpretation of the
pre-existing data permit at least to refine the relative chronology
of the events and the tectonic significance of the
steeped profile of this tract of the Angolan coastal margin.
The Terrace I appears to be a polycyclic surface whose
erosional modelling extended from the NE to the SW following
the gradual emersion of the Kwanza basin. As the
stratigraphy of offshore wells demonstrates, during the
120
Pliocene (and Early Pleistocene?) this continental surface
extended towards SW far beyond the modern coastline.
Subsequently, a phase of downfaulting caused a large, outer
portion of the Surface to collapse under the ocean and
a first, moderate wave of fluvial dissection to invade the
emerged sector. After the genesis of the Terrace II along
the newly defined coastline, an uplift of few tens of meters
occurred which promoted a second, stronger phase of rivers
entrenchment and drainage re-arrangement. By taking
into account both the degree of preservation and the substantially
uniform elevation of the 15-20 meters sea-level
marks (Terrace III) along the whole Angolan coast, we are
inclined to assign it to a late Quaternary high-stand, possibly
to one or more peaks of the Oxygen Isotope Stage 5.
ADRIAN ClOACA
Geomorphological contributions to a natural reservation
conservation programme
Department of Dynamic Geomorphology, Institute of Geography,
Romanian Academy, 12, Dimitrie Racovita, Sector 2,
Bucharest 70307, Romania
According to local and country administration reports,
there are nearly one thousand reservations in Romania. No
state-of- equilibrium studies were previously made. Today,
they appear to be in part degraded, hence the need for a
complex geomorphological study of natural rehabilitation
opportunities.
The relief, a major element in the perception of the landscape,
undergoes quantity and quality alterations with
consequences on all the components of the landscape. If
the agregate of landforms affecte,d by these alterations is
rapidly changing in aspect, this fact is primarely the work
of catastrophic geomorphological processes.
An inventory of the landforms in which nature reserves have
been grouped by gee-type criteria (according to one or
several dominant geomorphologic-al processes) enable their
classification in terms of the geomorphological hazard they
are prone to. This also allows for conservation proposals to
be put forward.
DARIUSZ CISZEWSKI
Influence of geomorphological factors on accumulation
of heavy metals in polluted river channels
Institute of Nature Conservation, Polish Academy of Sciences,
ul. Lubicz 46,31-512 Krakow, Poland
The content of heavy metals in river bottom sediments was
investigated in longitudinal and cross profiles of rivers