 |
| Titel |
Long-term stability of the SE Australian escarpment inferred from cosmogenic-nuclides and high-resolution topography analysis |
| VerfasserIn |
Vincent Godard, Anthony Dosseto, Olivier Bellier, Didier Bourlès, Jules Fleury, Aster Team |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250145347
|
| Publikation (Nr.) |
 EGU/EGU2017-9281.pdf |
|
|
|
|
|
| Zusammenfassung |
| Passive margin escarpments are major features of continental relief and long-standing
remnants of rifting episodes. Despite their presence along many continental borders, their
mode of evolution is highly debated and various types of scenarios are proposed, such as
parallel retreat or down-wearing of the escarpment. Reported rates of evolution also vary over
several orders of magnitudes, from a few meters to a few kilometers per million years. For
these reasons additional geomorphological data that allow to constrain their history are highly
needed.
We quantified landscape dynamics across the SE Australian Escarpment (Bega Valley), in
order to assess its stability over the Late Cenozoic to Holocene timescales through
the determination of CRN basin-averaged denudation rates of 20 catchments. The
calculated landscape denudation rates are 10-20 mm/ka in lowland and upland
catchments for both sides of the escarpment while catchments draining across the
escarpment display denudation rates up to 60 mm/ka. Geomorphic parameters
extracted from a high-resolution Digital Elevation Model derived from stereo-pairs
of Pléiades images show that hilltop curvature is constant in the lowland part, up
to the very edge of the escarpment. We estimate an apparent hillslope diffusion
coefficient from CRN-derived denudation rates and Pléaides DEM-derived hilltop
curvature. When confronted with measured hillslope lengths in the lowland part, it
leads to a hillslope relaxation time lower bound on the order of several Ma, and
suggests that the landscape is stable over such a timescale. This argues against
significant recent evolution of the escarpment, and, in particular, against rapid retreat
rates.
Our study also demonstrates the potential of high-resolution Digital Elevation Models derived
from Pléiades images pairs in quantitative geomorphology studies. Such technique provides a
suitable and cost-effective alternative to airborne LiDAR, and allows to extract
fine-scale morphometric parameters over large areas in low-vegetation settings. |
|
|
|
|
|
|