Reconciling the roles of climate and tectonics in Late Quaternary fan development on the Spartan piedmont, Greece
Richard J. J. Pope, Keith N. Wilkinson, 2005. "Reconciling the roles of climate and tectonics in Late Quaternary fan development on the Spartan piedmont, Greece", Alluvial Fans: Geomorphology, Sedimentology, Dynamics, A. M. Harvey, A. E. Mather, M. Stokes
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The evolution of five alluvial fan systems is discussed in relation to chronology and possible tectonic and climatic triggering mechanisms. Two types of fan have evolved on the Spartan piedmont, Greece. First relatively large, low-angle fans, comprising four segments (Qf1–Qf4) composed of debris-flow and hyperconcentrated-flow deposits, with fluvial sediments restricted to the upper deposits of the distal segments. Second small, steep telescopically segmented fans, which consist of three segments (Qf1–Qf3), formed predominantly by debris-flow and hyperconcentrated-flow deposits. Morphological analysis of surface soils coupled with mineral magnetic and extractable iron (Fed) analyses of B-horizons suggest that individual segments can be correlated across the piedmont and have equivalent age. Luminescence dating of fine-grained deposits suggests that Qf1 segments formed during marine isotope stage (MIS) 6, Qf2 segments during MIS 5, Qf3 segments during MIS 4–2, and Qf4 segments during MIS 2 and 1. Tectonics has exerted a limited influence on fan systems. Regional uplift provides the gross relief conducive for fan development. The locations of fans were determined by transfer faults of Tertiary age, while Quaternary faulting initiated short phases of fan incision. Climate change as manifested by cycles of aridity and low vegetation cover during stadials, and humidity and deciduous woodland during interglacials and interstadials, played a key role in fan evolution during the later Middle and Upper Pleistocene. Aggradation occurred during stadials, with minor deposition and intermittent erosion during most interstadials, and entrenchment during the interglacials and longer interstadials. Deposition during the Holocene is limited in extent.
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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.