A similar to 8,000-yr record of palaeohydrology and environmental change in fluvial-influenced sediments from Arles-Piton core, upper Rhone Delta, France

摘要

This paper presents new data on Holocene palacohydrology and environmental history of the Rhone Delta. Derived from integrated stud), of a 18.3 m Arles-Piton core drilled immediately to the south of the present delta apex, sediments were investigated for sedimentology, micropalaeontology, palynology, magnetic susceptibility and microcharcoal contents. C-14 dates, archaeological/historical data and palyno-correlation provided chrono-stratigraphic control. Sedimentary and micropalacontological analyses show the following palaeo-environmental succession: the top of a distributary-channel infilling (before 6157-5843 BC), doubtless very close to the palaeocoastline; a brackish- or freshwater swamp (5719-5530/4796-4463 BC) partially disconnected from the Rhone channel; a distal flood plain (5719-5530/4796-4463 BC) in which phenomenon of rapid aggradation is linked to abundant flood supplies of the Rhone River; a high-energy palaeochannel (4796-4463/2900-2503 BC) with a ravel-sand material load; a proximal flood plain (2900-2503 BC/AD 270-290) in which pedosedimentary processes and occupation levels indicate discontinuous aggradation and exundation; a crevasse splay (after AD 270-290) that covers the present floodplain surface. Channel avulsion is a very important process in the high delta-plain construction of the Rhone River. Avulsion process controls 43% of the alluvial fill studied. The alluvium arriving in the upper Rhone Delta was derived mainly from proximal source areas (Massif Central, southern Alps) during the last 8,000 years, except during for the Rhodanian hydrological change of the Roman antiquity during which detrital inputs were derived firstly from the northern and southern Alps, and secondly from the Massif Central. Finally, the interference between biomass-burning tracks, wildfires and anthropogenic impact is discussed to the regional (catchment) and local (delta) scales.