Morphometry and depositional style of Late Pleistocene alluvial fans: Wadi Al-Bih, northern UAE and Oman
Asma Al-Farraj, Adrian M. Harvey, 2005. "Morphometry and depositional style of Late Pleistocene alluvial fans: Wadi Al-Bih, northern UAE and Oman", Alluvial Fans: Geomorphology, Sedimentology, Dynamics, A. M. Harvey, A. E. Mather, M. Stokes
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Three types of alluvial-fan settings are recognized in the Wadi Al-Bih area of the Musandam Mountains, northern UAE and Oman; mountain-front fans, tributary-junction fans and steep hillslope debris cones. Three styles of fan geometry, only partly dependent on fan setting, can be recognized: telescopic fans, stacked fans and truncated fans. Each style, together with degree of confinement, reflects the topographic and geological context of the fan and its source area. The mountain-front fans are mostly unconfined fans with telescopic styles. The tributary-junction fans are confined fans, some with stacked or telescopic styles, others that have been truncated by base-level-induced toe trimming. Most of the debris cones are simple hillfoot debris cones. Standard morphometric analyses of fan areas and fan gradients in relation to drainage basin area yield results that compare with other studies, but the relationships differ between the three groups of fans, in part reflecting fan style, especially between mountain-front and tributary-junction fans. The morphometry of the debris cones is only poorly characterized by the morphometric relationships. Cone morphology most strongly reflects source-area lithology. Analysis of the residuals from the regression analyses suggests that the morphometric differences between the three groups reflect fan sedimentary processes, fan setting and fan style, particularly relating to confinement.
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Alluvial fans are important sedimentary environments. They trap sediment delivered from mountain source areas, and exert an important control on the delivery of sediment to downstream environments, to axial drainages and to sedimentary basins. They preserve a sensitive record of environmental change within the mountain source areas. Alluvial fan geomorphology and sedimentology reflect not only drainage basin size and geology, but change in response to tectonic, climatic and base-level controls. One of the challenges facing alluvial fan research is to resolve how these gross controls are reflected in alluvial fan dynamics and to apply the results of studies of modern fan processes and Quaternary fans to the understanding of sedimentary sequences in the rock record. This volume includes papers based on up-to-date research, and focuses on three themes: alluvial fan processes, dynamics of Quaternary alluvial fans and fan sedimentary sequences. Linking the papers is an emphasis on the controls of fan geomorphology, sedimentology and dynamics. This provides a basis for integration between geomorphological and sedimentological approaches, and an understanding how fluvial systems respond to tectonic, climatic and base-level changes.