| 1. |
- Fitzsimmons, Kathryn E., et al.
(författare)
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Luminescence sensitivity of rhine valley loess : Indicators of source variability?
- 2022
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Ingår i: Quaternary. - : MDPI AG. - 2571-550X. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Loess provides a valuable terrestrial record of past environmental conditions, including the dynamics and trajectories of air mass circulation responsible for dust transport. Here we explore variations in the luminescence sensitivity characteristics of sedimentary quartz and feldspar as possible tools for identifying changes in source down a loess-palaeosol sequence (LPS). Luminescence sensitivity is a rapidly measurable index which is the product of interplay between source lithology and the history of the quartz or feldspar clasts. Variations in sensitivity of down profile may therefore reflect changes in sediment provenance as well as other factors such as weathering through pedogenesis. We undertake an empirical investigation of the luminescence sensitivity of quartz and feldspar from different grain-size fractions from the Schwalbenberg LPS in the German Rhine valley. We compare samples from a 30 m core spanning the last full glacial cycle with samples of oxygen isotope stage (OIS) 3–2 age exposed within nearby profile. We find an overall inverse relationship between quartz and feldspar sensitivity, as well as variability in sensitivity between different quartz grain sizes. Statistical analyses yield a significant correlation between IR50 sensitivity from unprocessed sediments and clay content, and feldspar sensitivity and Si/Al ratios down the core. Since Si/Al ratios may indicate changes in provenance, the latter correlation suggests that IR50 measurements on unprocessed samples may be used to provide a reliable, rapid scan of source variability over millennial timescales.
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| 2. |
- Schaetzl, Randall J., et al.
(författare)
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Approaches and challenges to the study of loess : Introduction to the Loess-Fest Special Issue
- 2018
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 89:3, s. 563-618
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In September 2016, the annual meeting of the International Union for Quaternary Research's Loess and Pedostratigraphy Focus Group, traditionally referred to as a LoessFest, met in Eau Claire, Wisconsin, USA. The 2016 LoessFest focused on thin loess deposits and loess transportation surfaces. This LoessFest included 75 registered participants from 10 countries. Almost half of the participants were from outside the United States, and 18 of the participants were students. This review is the introduction to the special issue for Quaternary Research that originated from presentations and discussions at the 2016 LoessFest. This introduction highlights current understanding and ongoing work on loess in various regions of the world and provides brief summaries of some of the current approaches/strategies used to study loess deposits.
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| 3. |
- Vinnepand, Mathias, et al.
(författare)
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Decoding geochemical signals of the Schwalbenberg Loess-Palaeosol-Sequences — A key to Upper Pleistocene ecosystem responses to climate changes in western Central Europe
- 2022
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Ingår i: Catena. - : Elsevier BV. - 0341-8162. ; 212
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Tidskriftsartikel (refereegranskat)abstract
- Loess deposits are the most extent continental archives of climatic- and environmental change and represent important components of local and global dust systems. Consequently, their geochemistry provides an excellent basis for studying climate oscillations on land and how these affect processes in the terrestrial system. It is, however, challenging to assess information archived in loess records due to complexities in their formation, causing interfering geochemical signatures. In particular, the use of element ratios to derive weathering indices may be complicated since dust sources change through time, and since ecosystems respond differently to changing conditions. Whilst this complexity appears as limiting factor, the explanatory potential of proxies increases when the diversity of geochemical processes is acknowledged. To make use of this potential, we integrate the decadic logarithm of element ratios indicative for provenance shifts, mineral sorting during transport and sediment reworking as well as weathering into multivariate statistical analysis. We test, if the sensitivity of Principal Component Analyses (PCA) and Linear Discriminant Analysis (LDA) can be increased by applying both to sub-datasets of diagnostic Stratigraphic Units (SU) of the Schwalbenberg Loess-Palaeosol-Sequences (Middle Rhine valley, Germany). The selected site recorded sub-millennial Upper Pleistocene ecological changes in an unprecedented resolution for Central European LPS. Differences in operating functions of PCA and LDA and our age model highlight timing and intensity of provenance shifts, sediment relocation, decalcification, redox dynamic and clay-mineral formation associated with Atlantic-driven climate oscillations. Based on this we provide evidence for the accretionary character of interstadial palaeosols caused by a close interplay of dust input and soil formation. Automated re-detection of SU across the site using LDA functions contributes important insights into slope dynamics through regional erosion events. Overall, our approach provides a key for tracing ecological changes during climate oscillations across continents.
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