Resolving the frequency of mass movements (landslides, rockfalls) in response to climate change with new luminescence techniques


  • Supervisors: Dr Rachel Smedley, University of Liverpool
    Dr Elisabetta Mariani, University of Liverpool


  • External Supervisors: Dr Stuart Dunning (Newcastle University, UK)

  • Contact:

    Dr Rachel Smedley, University of Liverpool, rachel.smedley@liv.ac.uk

  • CASE Partner:

Application deadline: 10 January 2020

Introduction:

Mass movement processes (landslides, rockfalls) are common in glacial and post-glacial landscapes, with timing related to rebound induced seismicity, rock-mass damage. More recently, permafrost degradation has been linked to increased rates of mass movements as thermal thresholds are crossed. With anthropogenic climate change in glacial and permafrost regions, it is important to understand how sensitive the frequency of mass movement processes in these environments are to warming temperatures. This project aims to apply new luminescence techniques to resolve the timing of large rock avalanches and more recent permafrost degradation induced debris flows of superficial sediments in the U.K., followed by a key site in W. Greenland (Benjamin et al. 2018).

Luminescence dating is a geochronological technique important for reconstructing past environments on Earth over the last million years (see Smedley, 2018 for details). Routine luminescence dating has long been performed on sedimentary grains (e.g. sand), but new developments in the technique now mean that we can use rocks for both burial and exposure dating (Sohbati et al. 2012; Jenkins et al. 2018). It has been shown that in a rock surface continuously exposed to daylight, resetting of the luminescence signal progressively propagates deeper into the surface with time and a luminescence profile measured through a rock surface can be exploited to determine exposure or burial ages. This provides a new, exciting opportunity to apply luminescence dating to mass movement processes (e.g. landslides, rockfalls).

Project Summary:

This project will develop new luminescence techniques to resolve the record of mass movements (landslides, rockfalls) in response to deglaciation. It will first use samples collected from well constrained examples of landslides and rockfalls in the United Kingdom to validate the technique. The latter stages of the project has the option to collect samples from W Greenland to constrain the timing of rock-slope failures caused by ice loss, and, more recent activity due to climate warming. A unique dense cluster of deposits are present at Vaigat that allow detailed consideration of the timing of rock-slope failure due to ice loss, and, more recent activity due to climatic warming.

The project will use state-of-the-art equipment to provide new insights into the geochemistry, crystalline structure and light attenuation of different lithologies on an unprecedented scale. The project will aim to better understand the uncertainties caused by different lithologies used for luminescence dating, including the rock geochemistry and light attenuation. The luminescence readers housed within the Liverpool Luminescence Laboratory led by Dr Smedley give us the capabilities of measuring light penetration into rock surfaces, and thus, determining luminescence exposure and burial ages. The internal geochemistry and structure of mineral phases can be determined using the scanning electron microscope facilities (SEM) housed within Electron Microscopy Laboratory (EBSD-SEM) led by Dr Mariani at Liverpool.

References:

Benjamin J et al. (2018). Transferability of a calibrated numerical model of rock avalanche run-out: application to 20 rock avalanches on the Nuussuaq Peninsula, West Greenland. Earth Surface Processes and Landforms. DOI: 10.1002/esp.4469 

Jenkins et al. 2018. A new approach for luminescence dating glaciofluvial deposits-High precision optical dating of cobbles. Quaternary Science Reviews, 192, 263-273. 

Sohbati, R., Jain, M., Murray, A.S., 2012. Surface exposure dating of non-terrestrial bodies using optically stimulated luminescence: A new method. Icarus 221(1), 160-166. 

Smedley, R.K. (2018). Dust, sand and rocks as windows into the past. Elements, 14 (1), 9-14.

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