Luminescence based chronologies on Late Pleistocene loess-palaeosol sequences: an applied-methodological study on quartz separates

Understanding morphological processes that sculpt former terrestrial landscapes is one of the driving rationales in Quaternary research. Loess records have been found to be valuable archives for reconstructing palaeoenvironmental conditions. However, once identified, characterised and classified by fieldwork, the stratigraphic significance of such records has to be revealed by numerical dating. Luminescence dating, especially optically stimulated luminescence (OSL), is the leading dating approach for establishing chronologies on loess archives. Furthermore, the development of luminescence dating techniques on sediments is closely connected with the history of loess research and vice versa. As part of the European loess belt the Saxonian Loess Region is located in a transition zone between oceanic dominated western and continental dominated eastern climates. The Saxonian Loess Region comprises up to 20 m thick Weichselian loess accumulations, with intercalated palaeosoils. Loess research in Saxony dates back to the late 1950s. For an interdisciplinary research project funded by the German Research Foundation (DFG), since 2008 the Saxonian Loess Region has been re-investigated by fieldwork and laboratory methods. For the first time, during the work on this thesis, high-resolution numerical chronologies were established in the Saxonian Loess Region on five loess sections using OSL dating on quartz separates. Here, age results of these dating from two sections are presented. The dating was employed as a comparison of three quartz grain size fractions (coarse, middle and fine grain) commonly used for luminescence dating. As a survey on four loess sections, three from Germany (Saxony and Saxony-Anhalt) and one from the Czech Republic, these studies investigate the question whether the use of different grain size fractions from one sample yield consistent luminescence characteristics and age results. By combining dating application with methodological investigations, this thesis is intended as contribution towards the establishment of reliable high-resolution numerical chronologies on Late Pleistocene loess-palaeosol sequences based on OSL dating of quartz separates. In summary seven studies are presented along with an extended summary. Four studies (Study I, Study II, Study VI, Study VII) present numerical chronologies using OSL dating techniques on different grain size and (mineral) fractions. Although dating of the quartz fraction is the main focus of this study, in Study VI polymineral fine grain dating results using the post-IR IR protocol are presented for a comparison. Two studies (Study III, Study IV) deal with technical issues that arose during the dating applications. Firstly, an R package for luminescence dating data analysis ('Luminescence') was developed and secondly, the cross-bleaching behaviour of IR-LEDs of the used luminescence readers were quantified. Study V treats the question whether the common practice of using an identical alpha-efficiency (a-value) for the conventional IR50 and pIRIR225 dating is justified under theoretical and empirical viewpoints. It was found that for the established numerical chronologies on loess the fine grain quartz fraction results in reliable age estimates up to the Eemian (MIS 5e, 5d). The high-resolution dating in Saxony uncovered a prominent hiatus of c. 30 ka between the early and the late Weichselian found in all investigated loess sections in Saxony. The fine grain quartz age results are confirmed by the polymineral fine grain dating. The results of a cross-bleaching survey on 10 luminescence readers revealed substantial cross-bleaching behaviour of the IR-LEDs (mean cross-bleaching: c. 0.026 %), in an order of magnitude higher than for blue LEDs. This may lead to systematic underestimations during De determination. The investigation on the a-values of polymineral fine grain samples gave evidence for significant differences between the mean a-values obtained with the IR50 and the pIRIR225 signals; at least by 0.02. The a-value obtained with the pIRIR225 signal is always higher. As consequence of the cross-bleaching measurements a new component for the luminescence readers was developed by the manufacturer, which is capable to reduce the cross-bleaching of the IR-LEDs up to 20-times (Study IV). The developed R package 'Luminescence' was launched in the course of this thesis enabling data analysis and visualising options, which had not been available before.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bayreuth

Year

2013

Author dc:creator

• Kreutzer, Sebastian

Contributors dc:contributor

• Fuchs, Markus

Repository record source_url

https://epub.uni-bayreuth.de/id/eprint/1673/

OAI identifier oai:identifier

oai:epub.uni-bayreuth.de:1673