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Fan Development (fan + development)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

Controls on modern alluvial fan processes in the central Alps, northern Italy

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2004
Giovanni B. Crosta
Abstract Alluvial fan development in Alpine areas is often affected by catastrophic sedimentary processes associated with extreme ,oods events, causing serious risks for people living on the fans. Hazard assessment in these areas depends on proper identi,cation of the dominant sedimentary processes on the fans. Data from a set of 209 alluvial fans from the central Alps of Italy are presented in this paper and analysed with the help of various statistical techniques (linear regression, principal components analysis, cluster analysis, discriminant analysis and logistic regression). First, we used modern sedimentary facies and historical records (,ood events since 15th century), to distinguish between the two dominant sedimentary processes on alluvial fans: debris ,ows and stream,ows. Then, in order to analyse the main controls on past and present fan processes, 36 morphological, geological and land-use variables were analysed. As with observations for arid-environment fans, catchment morphology is the most in,uential factor in the study area, whereas geology and land use are minor controls. The role of climatic change and landsliding within the catchments also seems to be very important and is discussed. Statistical techniques also help in differentiating groups of alluvial fans by sets of controlling factors, including stage and type of evolution. Finally, by using discriminant analysis and logistic regression, we classi,ed alluvial fans according to the dominant sedimentary process, with a success rate ranging between 75 and 92 per cent. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Little ice age alluvial fan development in Langedalen, western Norway

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2001
Simon G. Lewis
This paper reports a preliminary investigation of the sedimentary succession in two alluvial fans in western Norway. Sedimentological information is supplemented by palaeoecological data from pollen analysis and the age of the sequence is constrained by six radiocarbon age estimates on woody fragments and peat. These data suggest that significant accumulation of fan sediments took place after AD 1637,1685. Before this, the fluvial landscape and the adjacent slopes may have been more stable with the development of Betula, Salix and Alnus woodland on the valley floor and sides. Although there is no indication of gradual climatic deterioration in the vegetation record from these sites, the radiocarbon chronology suggests that enhanced fan development was coincident with the climatic change associated with the ,Little Ice Age'. This was probably a response to glacier expansion and increased discharge and sediment supply to the alluvial fans from outlets of the Jostedalsbreen ice cap on the southern side of Langedalen. Initial response to climate change in this setting was therefore enhanced geomorphic activity and instability of the valley-side slopes. [source]

Alluvial fan development and morpho-tectonic evolution in response to contractional fault reactivation (Late Cretaceous,Palaeocene), Provence, France

BASIN RESEARCH, Issue 2 2009
S. Leleu
ABSTRACT Along-strike variability within a Late Cretaceous to early Palaeocene contractional growth structure and associated alluvial fan deposits is documented at the northern margin of the Arc Basin (Provence, SE France). This contribution shows that alluvial fans can be used as high-resolution proxies to reconstruct structural segmentation and palaeo-geomorphological evolution of a source/basin margin system. Facies-based reconstruction allows the spatial and temporal distribution of alluvial fan bodies to be mapped. Relationships between fan area and catchment size from modern alluvial fan systems were used to estimate palaeo-catchment size. Combining alluvial fan morphologies with catchment area, pebble provenance analysis and growth structure reconstruction, we show that: (1) fan distribution and related depositional processes were strongly influenced by intrinsic parameters such as drainage basin evolution, local structural inheritance and lateral facies changes in source area lithologies; (2) Inherited structures trending N100 effectively controlled the first-order location of the fold and thrust structures (Montagne Sainte-Victoire Range) and adjacent depositional areas (Arc Basin); (3) Syn-sedimentary faults trending N010-030 influenced the source/basin margin development and interacted with developing growth structures; (4) Facies changes in Jurassic carbonates controlled fold development and consequently the structural evolution of the source area; and (5) the N010-030 faults and along-strike variability of the source/basin margin system were ultimately controlled by basement structures that controlled where Late C etaceous deformation nucleated. The overall architecture of the source/basin margin system reflects segmentation and strain partitioning along strike, as demonstrated by diachronous alluvial fan distribution. [source]