TY  - JOUR
A1  - Braun, Jean
A1  - Gemignani, Lorenzo
A1  - van der Beek, Peter
T1  - Extracting information on the spatial variability in erosion rate stored in detrital cooling age distributions in river sands
JF  - Earth surface dynamics
N2  - One of the main purposes of detrital thermochronology is to provide constraints on the regional-scale exhumation rate and its spatial variability in actively eroding mountain ranges. Procedures that use cooling age distributions coupled with hypsometry and thermal models have been developed in order to extract quantitative estimates of erosion rate and its spatial distribution, assuming steady state between tectonic uplift and erosion. This hypothesis precludes the use of these procedures to assess the likely transient response of mountain belts to changes in tectonic or climatic forcing. Other methods are based on an a priori knowledge of the in situ distribution of ages to interpret the detrital age distributions. In this paper, we describe a simple method that, using the observed detrital mineral age distributions collected along a river, allows us to extract information about the relative distribution of erosion rates in an eroding catchment without relying on a steady-state assumption, the value of thermal parameters or an a priori knowledge of in situ age distributions. The model is based on a relatively low number of parameters describing lithological variability among the various sub-catchments and their sizes and only uses the raw ages. The method we propose is tested against synthetic age distributions to demonstrate its accuracy and the optimum conditions for it use. In order to illustrate the method, we invert age distributions collected along the main trunk of the Tsangpo-Siang-Brahmaputra river system in the eastern Himalaya. From the inversion of the cooling age distributions we predict present-day erosion rates of the catchments along the Tsangpo-Siang-Brahmaputra river system, as well as some of its tributaries. We show that detrital age distributions contain dual information about present-day erosion rate, i. e., from the predicted distribution of surface ages within each catchment and from the relative contribution of any given catchment to the river distribution. The method additionally allows comparing modern erosion rates to long-term exhumation rates. We provide a simple implementation of the method in Python code within a Jupyter Notebook that includes the data used in this paper for illustration purposes.
Y1  - 2018
U6  - https://doi.org/10.5194/esurf-6-257-2018
SN  - 2196-6311
SN  - 2196-632X
VL  - 6
IS  - 1
SP  - 257
EP  - 270
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Govin, Gwladys
A1  - van der Beek, Peter
A1  - Najman, Yani
A1  - Millar, Ian
A1  - Gemignani, Lorenzo
A1  - Huyghe, Pascale
A1  - Dupont-Nivet, Guillaume
A1  - Bernet, Matthias
A1  - Mark, Chris
A1  - Wijbrans, Jan
T1  - Early onset and late acceleration of rapid exhumation in the Namche Barwa syntaxis, eastern Himalaya
JF  - Geology
N2  - The Himalayan syntaxes, characterized by extreme rates of rock exhumation co-located with major trans-orogenic rivers, figure prominently in the debate on tectonic versus erosional forcing of exhumation. Both the mechanism and timing of rapid exhumation of the Namche Barwa massif in the eastern syntaxis remain controversial. It has been argued that coupling between crustal rock advection and surface erosion initiated in the late Miocene (8-10 Ma). Recent studies, in contrast, suggest a Quaternary onset of rapid exhumation linked to a purely tectonic mechanism. We report new multisystem detrital thermochronology data from the most proximal Neogene clastic sediments downstream of Namche Barwa and use a thermo-kinematic model constrained by new and published data to explore its exhumation history. Modeling results show that exhumation accelerated to similar to 4 km/m.y. at ca. 8 Ma and to similar to 9 km/m.y. after ca. 2 Ma. This three-stage history reconciles apparently contradictory evidence for early and late onset of rapid exhumation and suggests efficient coupling between tectonics and erosion since the late Miocene. Quaternary acceleration of exhumation is consistent with river-profile evolution and may be linked to a Quaternary river-capture event.
Y1  - 2020
U6  - https://doi.org/10.1130/G47720.1
SN  - 0091-7613
SN  - 1943-2682
VL  - 48
IS  - 12
SP  - 1139
EP  - 1143
PB  - American Institute of Physics
CY  - Boulder
ER  -