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Optical dating of loessic hillslope sediments constrains timing of prehistoric rockfalls, Christchurch, New Zealand
Author(s) -
Sohbati Reza,
Borella Josh,
Murray Andrew,
Quigley Mark,
Buylaert JanPieter
Publication year - 2016
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/jqs.2895
Subject(s) - geology , loess , thermoluminescence dating , optically stimulated luminescence , colluvium , feldspar , chronology , mass movement , geochemistry , geomorphology , prehistory , quartz , paleontology , alluvium , landslide
Developing a robust chronology for mass‐movement events is of crucial importance to understanding triggering mechanisms and assessing hazards. We constrain the emplacement time of four palaeorockfall boulders near Christchurch, New Zealand, using optically stimulated luminescence (OSL) of quartz and infrared stimulated luminescence dating (IRSL) of K‐feldspar from loessic hillslope deposits underlying and upslope of individual boulders. The quartz OSL and K‐feldspar pIRIR 290 ages are all consistent with the stratigraphy and in excellent agreement with each other, indicating that all the boulders that overlie the in situ loess must have been emplaced <13 ka ago. A comparison of luminescence ages with cosmogenic 3 He surface‐exposure ages from the surfaces of each boulder shows that two out of four boulders contain pre‐deposition 3 He inheritance. Overall, the optical ages are consistent with both a prehistoric rockfall event at 6–8 ka and a possible preceding event at 12–14 ka. This study is the first to show a successful application of luminescence dating to New Zealand colluvium loess and demonstrates the great advantage of a multi‐technique approach in mass‐movement dating.