La Plaine orientale de Thessalie: mobilité des paysages historiques et évolution tecto-sédimentaire

In order to understand the present-day morphological, geographical and environmental patterns of the Larissa Plain, a large amount of historical, archaeological, sedimentological, stratigraphic, tectonic and seismic data have been collected and analysed. The collaboration of different specialists was essential for these aims. The Larissa Plain is an inter-mountain basin formed during the Pliocene as a result of the post-orogenic collapse of the Hellenides. From the Middle Pleistocene, the region has been affected by a new tectonic phase which caused an important palaeogeographic change and fragmented the area into three distinct geographical domains characterised by different sedimentary conditions: the Pinios alluvial plain to the North; the Karla Lake to the South, and the Chasambali Bulge in between. The first sector corresponds to the active Tyrnavos Basin, while the second to the southern part of the inherited Pliocene Larissa Basin. The Chasambali Bulge has been differentiated by a system of northward down-stepping normal faults thus creating a temporary hydrographic divide between the two major domains. Recent dikes have disconnected the present physiography of the plain from the hazards of the recurrent floods of the Pinios River over the alluvial plain and discharged the Asmaki River of its past function of an overflow convector from the northern drainage system (Tyrnavos Basin) towards the southern one (Karla Lake). A four-step model of the tecto-sedimentary evolution of the Tyrnavos Basin is proposed. a) The profile of the Pinios River is in equilibrium. b) The area is affected by a tectonic paroxysm that produced a partition of the plain. c) Local erosion as well as a distributed fluvio-lacustrine sedimentation occurred until the gap was filled up. d) Once widespread sedimentation halted, the abandoned alluvial plain suffered a diffuse pedogenesis. Several secondary factors (prolonged morphogenic activity, compaction-induced subsidence, differential sedimentary compaction, erosional phenomena outside the basin, climate variations and anthropic activity) that may have disturbed and changed this simple cyclic evolution, locally or temporarily, have been considered and analysed in detail. The paradox of the Larissa Plain, where the Pinios River flows 20 to 40 m higher than the Karla Lake and exits the area crossing the Palaeozoic bedrock along the Rodia Narrow, has been satisfactorily explained. Probably during the last few thousand years, this palaeogeographic pattern was characterised by an alluvial plain in the Tyrnavos Basin and an independent large lake in the southern Larissa Plain, since Middle Pleistocene, became unstable due to one or more concomitant and possibly inter-dependent causes which are discussed here in detail. The build up of an artificial embankment along the Pinios River North of Larissa, definitely fossilised the present-day geography

Changes in the particle size distribution of quartzose sands affected by laterization: an approach by computer simulation

International audienc

La Zone Atelier Bassin du Rhône (ZABR) : un observatoire pour les scientifiques et les acteurs opérationnels mobilisés sur la gestion durable des hydrosystèmes du Rhône

[Departement_IRSTEA]RE [TR1_IRSTEA]RIE / TRANSFEAU [TR2_IRSTEA]QSA / DYNAQ [TR2_IRSTEA]QSA / HYDRECOIn 2000, the C.N.R.S. project Environment, Life, and Society proposed the setting up of workshop zones or Long Term Ecological Research groups dedicated to develop interdisciplinary research on anthroposystems or complex ecological systems including biophysical components and sociological aspects. Located in Lyon, the Rhone Watershed Workshop Zone (Zone Atelier Bassin du Rhône or ZABR) was officially labeled in 2001. It is the result of the mobilization of about 28 teams working in the watershed, and belonging to multiple academic disciplines contributing in studies dealing with water management. The ZABR aims at setting up field sites dedicated to observation and/or experimentation . The ZABR is laying research programs, intending to bring up new and updated data to public decision making when dealing with sustainable management of rivers and watersheds. The operational target of the Workshop Zone is to provide decision makers with a methodology to better evaluate the effects of watersheds rehabilitation applied to the functioning of hydrosystems, in terms of biodiversity (potential effects of restoration and rehabilitation steps on biodiversity), of sustainability (perennity of the effects of restoration works), and of potential water uses.En 2000, le Programme Environnement, Vie et Société du CNRS en France a proposé la création de Zones Ateliers destinées à développer la recherche interdisciplinaire sur les anthroposystèmes, ou systèmes fonctionnels complexes intégrant les milieux bio-physiques et les systèmes sociaux. Localisée à Lyon, la Zone Atelier Bassin du Rhône (ZABR) a été officiellement labellisée par le CNRS en octobre 2001. Elle mobilise 28 équipes de recherche soit 135 chercheurs travaillant sur ce grand bassin, et appartenant à de multiples champs disciplinaires impliqués dans l'aménagement des eaux. La ZABR met en place des sites ateliers d'observation et/ou d'expérimentation pour asseoir des programmes de recherche destinés à apporter des éléments scientifiques directement opérationnels pour l'aide à la décision publique en matière de gestion durable des cours d'eau et de leurs bassins versants. L'objectif opérationnel de la Zone Atelier est de mettre à disposition des décideurs des méthodologies d'évaluation a priori des effets des opérations de réhabilitation ou de restauration des bassins versants sur le fonctionnement des hydrosystèmes fluviaux en terme de biodiversité (effet potentiel et progressif des mesures sur la biodiversité), de durabilité (pérennité des effets des travaux de restauration), et d'usages potentiels des eaux

La Delta du Tibre. Delta du Tibre. Campagne de carrotage 2008. Etude des canaux de Portus.

A description of the results of the programme of geoarchaeological coring undertaken at Portus in 200