ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

leozoic sedimentary rocks and was fragmented by cretaceous
and tertiary movements. The surface is well preserved
at 600-700 m. In the Septentrionales Range the planation
surface lays beetween 450-600 m. It was developed
mainly on precambric granitic and migmatitic rocks. In
this range, different authors recognized deep weathering
profiles.
Remnants of a planation surface could be also recognized
in neighbouring areas. North, in Uruguay Republic, a fragmented
surface ocuppies more of 100000 km', It was formed
on granitic-migmatitic rocks of precambrian age
(Early-late Proterozoic, Rio de la Plata Craton). Thick continental
cretaceous deposits related.to erosion of weathering
surfaces could be observed north-west of the planation
surface. South of Colorado Basin is North Patagonian
Cratonic area; also a remanant of planation surface (at
1000 m) of «gondwanic age» developed in precambrianpaleozoic
granitic rocks partly affected by effusion of intraplate
tertiary basalts. All these surfaces probably constitute
fragments of a poligenetic planation surface developed
before the breaking up of Gondwanaland. It is possible
that an older planation surface was formed before the continental
accretion that lead to the formation of Gondwanaland
(post Brasilian cicle?).
Pattern of regional drainage is related to domal uplift,
reactivation of early structures, the effect of Andean Orogeny
and the basins' development. The integration of the
intracratonic basins and Salado aulacogene was an important
factor in the design of the drainage, probably following
a large scale megacapture model. The Salado aulacogene
could be an important foci of continental drainage
outlet to a newly opened ocean. Finally, structural control
of the Parana, la Plata and minors rivers by faulting and tilting
of the Rio de la Plata Craton is streghtened by the design
of the drainage. The scheme proposed here allows a
new perspective for the interpretation of South American
plains geomorphic evolution, related with the passive margin
development, and could replaced the «andean» vision.
ANDREAS PETEREK
Studies on the late Neogene to Recent morphotectonic
evolution of western Crete
Institute of Geology, Ruhr-University Bochum, Universitatsstr, 150,
D-44801 Bochum, Germany
In the western part of Crete (west of Chania area) the
morphostructural features reflect important influence of
late Neogene to Recent tectonic activity for the development
of the relief. Aspects on the morphotectonic structures
has been published earlier by various workers (e.g, Angelier
& alii 1982, Bonnefont 1971, Armijo & alii 1992).
The aim of the presented study is to evaluate the «time-table»
of the tectonic activities from morphotectonic criteria.
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This includes morphotectonic field mapping of fault scarps
as well as relief elements which are dislocated by faults
(e.g, planation surfaces, river and marine terraces) or controlled
by faulting (drainage pattern, alluvial fans). Field
mapping is supported by the analyses of aerial photographs
and satellite images.
The main fault zones of western Crete dissect the Neogene
basins as well as the pre-Neogene «basement areas» that
are built up by pre-late Miocene units (Creutzburg & alii
1977). Most of these faults already came active during the
late Miocene to early Pliocene sedimentation of the Neogene
deposits (cf Frydas & Keupp 1996). Coarse conglomerates
within the Neogene strata occur within the vicinity of
synsedimentarily active fault scarps. Only slight degradation
of the present fault scarps bounding the Neogene basins
indicates intense vertical displacements along these
faults during Pliocene and Quaternary times. These faults
crosscut uplifted pediments and valley terraces developed
within the footwall area. In many cases Holocene to sub­
Recent reactivation of older fault scarps can be observed.
At the base of the Neogene basin fill, a paleorelief is exhumed
showing a pronounced pre-late Miocene topography
in the range of some hundred meters. However, identification
of this paleorelief is not always clear due to differentially
uplifted and downthrown «basement» blocks within
the Neogene basins.
The topography in the «basement area» of western Crete
is characterized by the step-like arrangement of individual
fault-bounded blocks that bear remnants of planation surfaces.
In the area central part of the study area an approximately
10 km wide and NNE-SSW trending intramontaneous
graben segment has developed.
The western boundary of the Lefka Ori Mts. (2400 m) is
represented by a NNE-SSW trending escarpment. Triangle
facets and a poorly developed drainage pattern within
the range front indicate Pleistocene to Recent fault activity.
In the footwall of this fault a separate graben-like basin developed
preserving remnants of Neogene sediments (Moni
basin).
Quaternary and active faulting characterizes the morphology
of the southern and western coastal areas of Crete as
it is indicated by well contoured range fronts as well as
steep and instable slopes. Most of the primary faults (master
faults) are located off-shore. Secondary fault scarps
and landslides are very common in the uplifted footwall
that is represented by the island. V-shaped and deeply incised
valleys indicate rapid uplift.
ELLEN L. PETTICREW 1
& IAN G. DROPP0 2
Sediment flocculation: an important consideration for sediment
transport studies in Fluvial Geomorphology
1 Geography Programme, University of Northern British Columbia,
3333 University Way, Prince George, British Columbia, V2N 429 Canada
2 National Water Research Institute, Canada Centre for Inland Waters,
p.o. box 5050, Burlington, Ontario, L7R 4A6 Canada