EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Temporal shifts in erosion provenance through multiple earthquake cycles

Jin Wang1,2, Jamie Howarth3, Erin McClymont2, Alexander Densmore2, Sean Fitzsimons4, Thomas Croissant2, Darren Gröcke5, Martin West2, Erin Harvey2, Nicole Frith2, Mark Garnett6, and Robert Hilton2
Jin Wang et al.
  • 1Institute of Earth Environment, Chinese Academy of Sciences, China (
  • 2Department of Geography, Durham University, Durham, UK
  • 3School of Geography, Environment and Earth Science, Victoria University of Wellington, Wellington, New Zealand
  • 4School of Geography, University of Otago, Dunedin, New Zealand
  • 5Department of Earth Sciences, Durham University, Durham, UK
  • 6NERC Radiocarbon Facility, Rankine Avenue, East Kilbride, Glasgow, UK

Landslides are a dominant mechanism of erosion in mountain landscapes. Widespread triggering of landslides by large storms or earthquakes can lead rapid changes in short-term erosion rates. If landslides occur repeatedly in particular parts of a mountain range, then they will dominate the evolution of that section of the landscape and could leave a fingerprint in the topography. Despite this recognition, it has proved difficult to examine shifts in the focus of landslide erosion through time, mainly because remote sensing approaches from single events to a few decades at most. Here we turn to the depositional record of past erosion, attempting to track landslide occurrence and the provenance of eroded material using a novel combination of the isotopic and molecular composition of organic matter (bulk C and N isotopes, molecular abundance and isotopic composition) deposited in Lake Paringa, fed by catchments proximal to the Alpine Fault, New Zealand. In the modern day forest, we find correlations between elevation, soil depth and the bulk δ13C values of the organic matter and the carbon preference index of n-alkanes. We find large shifts in these measurements in the lake core. Using an empirical model based on modern soil samples we suggest that the erosion provenance shifts dramatically after each of four large Alpine Fault earthquakes in the last one thousand years. These shifts in inferred erosion altitude match shifts in the hydrogen isotope composition of long-chain n-alkanes (plant wax biomarkers) and the inferred shifts in depth track changes in organic matter radiocarbon activity and nitrogen isotope composition, lending support to our model. The combination of bulk isotopic composition and biomarker ratios has the potential to track erosion provenance in other settings. In the Lake Paringa record, we find that post-seismic periods eroded organic matter from a mean elevation of 722 +329/-293 m at the headwaters of source catchments and supplied 43% of the sediment in the core, while inter-seismic periods sourced organic matter primarily from lower elevations (459 +256/-226 m). These results demonstrate that repeated large earthquake consistently focus erosion at high elevations, while inter-seismic periods appear less effective at modifying the highest parts of the topography. 

How to cite: Wang, J., Howarth, J., McClymont, E., Densmore, A., Fitzsimons, S., Croissant, T., Gröcke, D., West, M., Harvey, E., Frith, N., Garnett, M., and Hilton, R.: Temporal shifts in erosion provenance through multiple earthquake cycles, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9817,, 2020


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