School Seminar - Professor Taylor Schildgen - GFZ Potsdam - Title: Alluvial channel systems: Shredders or recorders or paleoclimate history?
Professor Taylor Schildgen, GFZ Potsdam
Room G25, Reynolds Lecture Theatre, School of Earth Sciences, Wills Memorial Building
We are pleased to welcome Professor Taylor Schildgen from GFZ Potsdam, who will be delivering the School Seminar:-
Title: Alluvial channel systems: Shredders or recorders or paleoclimate history?
River systems can modify sediment-discharge signals through transient storage and release of sediment, thus complicating our ability to reconstruct past changes in landscape dynamics from stratigraphic records. The ability of a river to faithfully transmit sediment-discharge signals to its outlet (and into a depositional sink) depends on the system response time, i.e., the time required for a river to reach a new steady-state form following a perturbation. Response times that are slower than the forcing period result in either damping or amplification of the sediment-discharge signal, the magnitude of which is currently difficult to predict. In this talk I synthesize results from six field areas in the Central Andes, where rivers record periodic changes in past climate forcing in the form of cut-and-fill fluvial terrace sequences or alluvial-fan lobes. Systems with shorter lengths record a higher frequency of forcing (20-kyr and less) compared to longer systems (100-kyr to 400-kyr), despite being subjected to a similar climate history. I propose that alluvial systems comprise highly sensitive records of climate forcing, because changes in channel-bed elevation, which can occur shortly after a perturbation, can be recorded as geomorphic landforms. Moreover, different periods of forcing among a set of superimposed forcing periods will be recorded at different downstream lengths, due to the diffusive nature of alluvial-channel profiles. This finding implies that different sectors of alluvial-channel systems, from mountain-front alluvial fans to downstream alluvial rivers, will be sensitive to different forcing frequencies of climate, and should also show different sensitivities to anthropogenic climate change.
All staff and students welcome.
For further information, please contact Dr James Drewitt.