We are very pleased to announce the next (and last) Landscapes Live online seminar of the fall 2021 block by Sébastien Carretier (IRD and University of Toulouse) that will occur on Thursday, November 2nd at 4 pm CET / 3 pm GMT / 7 am PST / 10 am EST on:
"How can the movement of grains be linked to geomorphological transport laws (on long time scales)?"
This seminar will be live on Zoom and open to anyone interested (with a limit of 300 participants). Register in advance for this meeting: https://univ-rennes1-fr.zoom.us/meeting/register/tJMpfuyspj0tH9ze30aEfV3HzWEd8S3_KsPF (after registering, you should receive a confirmation email containing information about joining the meeting).
More information on these talks as well as the videos of previous talks are available on our website (https://www.landscapeslive.org/). Landscapes Live is the EGU Geomorphology Division's virtual webinar series focused on sharing exciting geomorphology research throughout the international scientific community. Feel free to contact us if you have questions or suggestions: landscapesliveseminar@gmail.com
Important: We are currently looking for new members to join the Landscapes Live organization team (https://www.landscapeslive.org/team-members) and to help us to organize and animate the next seminar series that will start in early 2022. If you are interested, please feel free to contact us, we will be happy to hear from you. We are also looking for potential speakers for 2022, and we are encouraging (self-)nomination, in particular (but not restricted to) from early career researchers.
Best wishes,
The Landscapes Live team: Rebekah Harries, Michal Ben-Isreal, Pierre Valla, Philippe Steer, Steffi Tofelde, Charlie Shobe, Vivi Pedersen and Boris Gailleton
Abstract
When a pulse of sediment is produced in a mountain during a tectonic or climatic change, this pulse spreads out gradually, some of the sediment is deposited along rivers, while some is transported to sedimentary basins in the form of strata. These strata are the main record of tectonic and climatic variations over geological time. However, these events can only be recorded if the time between two pulses is greater than the time required to transfer the sediment to the basin. Modelling this sediment transfer is therefore fundamental and has been the subject of much research. Models (e.g. diffusion) generally use geomorphic transport laws (GTLs) that depend on local variables such as slope, water discharge and riverbed grain size. However, there is evidence that sediment flux is dependent on upstream topography. This "non-locality" of transport has been evidenced by tracking grains in rivers over a few years or in channel experiments. It is the grains coming from upstream that have long travel lengths that induce this non-locality. GTLs can incorporate this non-locality in the simplified form of a transport distance, but the link between these GTLs and grain movement can be complicated. Furthermore, extrapolating these short time observations to the long time periods characteristic of landscape evolution (>>ka) is uncertain. Methods must therefore be found to 'track' the grains over long timescales and link them to the GTLs. The cosmogenic isotope 10Be measured in pebbles from a river in Chile has documented their dispersion from a known source. The data suggest a dispersion that deviates from the diffusion classically used to model sediment transport. The storage of some pebbles in the river for long periods of time seems to be at the origin of this behaviour. At the scale of a basin at the foot of a mountain, the long storage of these grains also seems to control part of the sedimentary record in a landscape evolution model coupled with grain transport. Ways can be proposed to link the GTLs in these models to the long-term grain dispersions measured by cosmogenic nuclides and OSL on individual grains.
