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| Titel |
Carbonate landscapes evolution: Insights from 36Cl |
| VerfasserIn |
Vincent Godard, Franck Thomas, Vincent Ollivier, Olivier Bellier, Esmaeil Shabanian, Cécile Miramont, Jules Fleury, Lucilla Benedetti, Valéry Guillou, Aster Team |
| 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 |
250140525
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| Publikation (Nr.) |
 EGU/EGU2017-3925.pdf |
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| Zusammenfassung |
| Carbonate landscapes cover a significant fraction of the Earth surface, but their long-term
dynamics is still poorly understood. When comparing with the situation in areas underlain by
quartz-rich lithologies, where the routine use of 10Be-derived denudation rates has delivered
fundamental insights on landscape evolution processes, this knowledge gap is particularly
notable. Recent advances in the measurement of 36Cl and better understanding of its
production pathways has opened the way to the development of a similar physically-based
and quantitative analysis of landscape evolution in carbonate settings. However, beyond these
methodological considerations, we still face fundamental geomorphological open questions,
as for example the assessment of the importance of congruent carbonate dissolution in
long-wavelength topographic evolution. Such unresolved problems concerning the relative
importance of physical and chemical weathering processes lead to question the
applicability of standard slope-dependent Geomorphic Transport Laws in carbonate
settings.
These issues have been addressed studying the geomorphological evolution of selected
limestone ranges in Provence, SE France, where 36Cl concentration measurements in bedrock
and stream sediment samples allow constraining denudation over 10 ka time-scale. We first
identify a significant denudation contrast between the summit surface and the flanks of the
ranges, pointing to a substantial contribution of gravity-driven processes to the
landscape evolution, in addition to dissolution. Furthermore, a detailed analysis of the
relationships between hillslope morphology and hilltop denudation allow to identify a
fundamental transition between two regimes: (1) a dynamics where hillslope evolution
is controlled by linear diffusive downslope regolith transport; and, (2) a domain
where denudation is limited by the rate at which physical and chemical weathering
processes can produce clasts and lower the hilltop. Such an abrupt transition toward a
weathering-limited dynamics may prevent hillslope denudation from balancing the rate
of base level fall imposed by the river network and could potentially explain the
development of high local relief observed in many Mediterranean carbonate landscapes. |
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