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| Titel |
The effects of lithology and landsliding on hillslope sediment supply: case study from southern Italy |
| VerfasserIn |
Duna Roda-Boluda, Mitch D'Arcy, Alex Whittaker, Jordan McDonald |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141461
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| Publikation (Nr.) |
 EGU/EGU2017-4977.pdf |
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| Zusammenfassung |
| Sediment supply from hillslopes –including volumes, rates and grain size distributions–
controls the sediment fluxes from upland areas and modulates how landscapes respond to
tectonics. Here, we present new field data from tectonically-active areas in southern Italy that
quantifies how lithology and rock-mass strength control the delivery processes and grain size
distributions of sediment supplied from hillslopes. We evaluate the influence of landslides on
sediment supply along 8 normal faults with excellent tectonic constraints. Frequency-area
analysis of the landslide inventory, and a new field-calibrated area-volume scaling
relationship, reveal that landsliding in the area is not dominated by large landslides (β ∼2),
with 83% of landslides being < 0.1 km2 and shallower than 3 m. Based on volumetric
estimates and published erosion rates, we infer that our inventory likely represents the
integrated record of landsliding over 1-3 kyrs, implying minimum sediment fluxes between
6.90 x 102 and 2.07 x 103 m3/yr. We demonstrate that outcrop-scale rock-mass strength
controls both landslide occurrence and the grain sizes supplied by bedrock weathering,
for different lithologies. Comparisons of particle size distributions from bedrock
weathering with those measured on landslide deposits demonstrates that landslides
supply systematically coarser material, with lithology influencing the degree of
coarsening. Finally, we evaluate the effect of landslide supply on fluvial sediment
export, and show that D84 grain size increases by ∼ 6 mm for each 100-m increment
in incision depth, due to the combination of enhanced landsliding and transport
capacity in more incised catchments. Our results reveal a dual control of lithology and
rock-mass strength on both the sediment volumes and grain sizes supplied to the fluvial
system, which we demonstrate has a significant impact on sediment export from
upland areas. This study provides a uniquely detailed field data set for studying
how tectonics and lithology control hillslope erosion and sediment characteristics. |
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