Development and application of luminescence dating of cobbles from glaciofluvial sediments

  • Geraint Jenkins

Student thesis: Doctoral ThesisDoctor of Philosophy


The aim of this thesis is to develop and test the luminescence dating of cobblesfrom glaciofluvial sediments. In recent years luminescence dating has increasingly been applied to date glaciofluvial sediments, but uncertainties about the degree of bleaching of the luminescence signal make dating challenging. Sub-surface luminescence measurements from cobbles from well-bleached environments are able to confirm that the cobbles were well-bleached at deposition. Having this confirmation when studying heterogeneously bleached environments would be a significant advantage. Bleaching experiments are undertaken to assess if numerical models of bleaching with depth are correct in nature. Measurements confirm that as the length of exposure increases the luminescence signal is reset to greater depths. Cobbles obtained fromOrrisdale Head, Isle of Man, show significant sub-surface bleaching, with rock slices to depths of 12 mm into the cobble sub-surface having been completely bleached at deposition. Fading-corrected IRSL50 ages (20.7 ± 1.3 ka) agree with independent age control at the site. One cobble also appears to show both the advance (26.2 ± 0.3 ka) and retreat of the Irish Sea Ice Stream. A major advantage of applying luminescence dating to cobbles instead of sand-sized grains is that at depths of > 2 mm into the cobble 92 % of the dose rate comes from the cobble itself and this makes luminescence ages insensitive to water content. In further tests of this approach, cobbles from two locations in north Wales show limited sub-surface bleaching, however the IRSL50 ages from the surface slices agree with independent age control. Following the trial at locations with independent age control, cobbles are obtained from a deposit at Bridgwalton which marks the furthest extent of a separate ice lobe which occupied the Cheshire-Shropshire basin. The IRSL50 age (25.3 ± 1.6 ka) gives the first depositional age for this location and shows that the Last Glacial Maximum (LGM) at this site is synchronous with that observed for the IrishSea ice stream at the Scilly Isles. Luminescence dating of cobbles has an enormous potential in providing accurate and robust ages for glaciofluvial sediments that are challenging to date
Date of Award2019
Original languageEnglish
Awarding Institution
  • Aberystwyth University
SupervisorGeoff Duller (Supervisor), Neil Glasser (Supervisor) & Helen Roberts (Supervisor)


  • cobbles
  • glacial
  • sediments
  • luminesnce
  • quaternary
  • IRSL

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