Dr. Martin Stange
Postdoc
CV
Project: Climatic versus tectonic drivers of intense catchment erosion in the southern Pyrenees, fincanced by Bremen TRAC,
Martin Stange (in cooperation with J. Kuss & C. Spiegel)
This study investigates the coupling of earth surface processes, climate,
and tectonics, particularly focussing on fluvial incision and sediment
routing in the river systems of the Pyrenees. Extensive terrace staircases
in the foreland domains formed in the deeply entrenched valleys of the
transverse river network of the Pyrenees. The paired (bilateral) terrace
staircases in the southern Pyrenees foreland (i.e. Ebro basin) show striking
similarities between the major southern Pyrenean tributary rivers as to
the number and elevation of individual terrace levels and the inferred
long-term (Quaternary) incision magnitudes. The amplitudes of valley entrenchment
are consistent in northern Pyrenean rivers but valley cross-sections disclose
asymmetric staircase geometries and non-uniform terrace extent and preservation.
Aiming at unravelling the drivers of fluvial valley entrenchment and terrace
staircase formation in the Pyrenees two major river systems have been
investigated (i) the prominent Segre River in the southeastern Pyrenees
and (ii) the Garonne River which drains large parts of the central northern
Pyrenees. Terrace staircases are composed of successions of abandoned
river floodplains separated by incision scarps that result from alternating
periods of extensive floodplain aggradation during cold-climate periods
and phases of vertical and lateral erosion associated with climatic transitions
(e.g., Vandenberghe, 2001, 2008). Such climate-triggered terrace formation
is superimposed on a long-term incision trend by a river that is stream-power
controlled and determined by the base level position of the fluvial network
(e.g., Whipple and Tucker, 1999; Blum and Törnqvist, 2000). Long-term
river incision is commonly a response to base level lowering or catchment
scale uplift (Merritts et al., 1994; Maddy et al., 2001) and, hence, can
only be evaluated considering the specific climatic, tectonic and base
level setting of a drainage network. At first, numerous sediment outcrops
were investigated for (post)depositional structures and deformations.
Major terrace levels were sampled for exposure dating via 10Be cosmogenic
nuclides. Field-based geomorphological mapping was combined with GIS-based
DEM and stream profile analyses. In a second step, results were integrated
in a numerical landscape evolution model (TISC; Garcia- Castellanos et
al., 2003) that was used to assess the relative impacts of Quaternary
climate change, tectonic uplift, lithospheric flexural isostasy, and differential
bedrock erodibility on stream (terrace) profile development in the southern
Pyrenean drainage system.