Controls on modern fan morphology in Calabria, Southern Italy
Introduction
Studies concerning the morphology, hydrology, and sedimentology of alluvial fans are numerous (e.g., Blissenbach, 1954; Bull, 1972; Nilsen, 1982; Harvey, 1988; Blair and McPherson, 1994), however, few studies have explored, on a probabilistic basis, the relationships between sedimentary facies, fan morphology, and drainage-basin geology and morphology (Melton, 1965; Kostaschuck et al., 1986; Marchi et al., 1993; Sorriso-Valvo and Sylvester, 1993). The purpose of this work is to examine the relationships between some of the distinctive morphometric elements of alluvial fans and their catchments, including fan facies, clast composition, area, length, overall slope and shape; and drainage-basin area, length, relief and ruggedness, and siting of the localized deposit source zone. We also explored the influence on fan morphology of the dominant depositional processes, and of the mechanical characteristics of the slope material, such as the rock hardness, as determined on a rank scale in the field. Our database includes a sample population of 68 cases.
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Setting
Fan populations used in this study come from three study zones and two sites in north Calabria (Fig. 1). Calabria is the southernmost part of continental Italy and is characterized by a complex geological framework. Its geomorphology is strongly controlled by its bedrock geology and neotectonics. The bedrock geology in the central and southern part of the region consists of Neogene sedimentary rocks that cover a thick stack of allochthonous nappes. These nappes consist of crystalline rocks
Survey and measurement
We measured or assessed at 83 sites, the following alluvial-fan parameters: area, length, width, slope angle, and horizontal distance along the feeder channel from the active part of the catchment to the fan apex (Table 1). The latter parameter, called the source ratio (SRCR) is illustrated in Fig. 3. For the drainage basins we determined area, length, relief. We also determined the following non-parametric variables: presence or absence of sediment storage in the feeder channel, confinement
Alluvial-fan characteristics
Fans can be distinguished on the basis of several criteria. For the purpose of this paper, we differentiate the fans according to: (1) a mountain front or intramontane-valley setting, in which constraints are imposed by the host morphology in terms of confinement; (2) mechanical resistance of the clasts; and (3) the type of dominant depositional process (water flows vs. mass flows). Applying the fan terminology of Blair and McPherson (1994), we have designed as CI fans those whose deposits are
Statistical analysis of fan and drainage basin elements
We described the morphology of the fans and their drainage basins by means of variables which displayed their average and statistical dispersion parameters, including mean square residuals, minimum and maximum values (Table 2). The relationships between the different variables was first investigated through a correlation analysis (Table 3). The values of Pearson's correlation coefficient (r) are shown for the variables that could be measured for the whole sample population and, separately, for
Discussion
In Calabria, fans appear to have been much more active in the past. Indeed, most of the fans studied here are inactive, and some are reduced to remnants by dissection. The large majority of fans are of the CI type, indicating that rapid, high-magnitude and relatively rare processes, control fan evolution. Several fans are cast as inset fills in the main channel of older fans. This aggradation and dissection pattern commonly is observed in Calabria (Sorriso-Valvo, 1990) and elsewhere (Harvey,
Conclusions
In conclusion, it appears that fan morphology is controlled to varying degrees by different factors in the fan setting (mountain front versus intramontane valleys). In general, fan form is controlled by fan constructional processes and is tightly linked to basin morphology. Fans seem to be much more regular in the spatially constrained mountain front (Table 3), but the influence of constructional processes on fan morphology is higher in the intramontane valleys. On the other hand, fan and basin
Acknowledgements
The authors wish to thank T. Blair, A. Harvey, J. McPherson and H. Mills for fruitful discussion and suggestions.
References (23)
Pollenanalytiische Untersuchung zur würmzeitalichen Vegetationsgeschichte von Kalabrien (Süditalien)
Flora
(1977)Aggradation and dissection sequences on Spanish alluvial fans: influence on morphological development
Catena
(1984)- et al.
Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies
J. Sediment. Res.
(1994) Geology of alluvial fans in semi-arid regions
Geol. Soc. Am. Bull.
(1954)Recognition of alluvial fan deposits in the stratigraphic record. In: Rigby, J.K., Hamblin, W.K. (Eds.), Recognition of Ancient Sedimentary Environments.
SEPM Special Publication
(1972)- et al.
Le precipitazioni in Calabria (1921–1980)
Geodata
(1990) Regional erosion: rates and scale problems in the Buonamico basin, Calabria
Catena Suppl.
(1988)Controls of alluvial fan development: the alluvial fans of the Sierra de Carrascoy, Murcia, Spain
Catena Suppl.
(1988)- Kock, G.S. Jr., Link, R.F., 1970. Statistical Analysis of Geological Data. Dover Publications, vol. 1, 375 pp. and vol....
- et al.
Depositional process and alluvial fan-drainage basin morphometric relationships near Banff, Alberta, Canada
Earth Surf. Process. Landforms
(1986)
Flow processes on alluvial fans in the eastern Italian Alps
Z. Geomorphol. Neue Fold
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