| 1. |
- Bertrand, Sebastien, et al.
(författare)
-
Inorganic geochemistry of lake sediments : a review of analytical techniques and guidelines for data interpretation
- 2024
-
Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 249
-
Forskningsöversikt (refereegranskat)abstract
- Inorganic geochemistry is a powerful tool in paleolimnology. It has become one of the most commonly used techniques to analyze lake sediments, particularly due to the development and increasing availability of XRF core scanners during the last two decades. It allows for the reconstruction of the continuous processes that occur in lakes and their watersheds, and it is ideally suited to identify event deposits. How earth surface processes and limnological conditions are recorded in the inorganic geochemical composition of lake sediments is, however, relatively complex. Here, we review the main techniques used for the inorganic geochemical analysis of lake sediments and we offer guidance on sample preparation and instrument selection. We then summarize the best practices to process and interpret bulk inorganic geochemical data. In particular, we emphasize that log-ratio transformation is critical for the rigorous statistical analysis of geochemical datasets, whether they are obtained by XRF core scanning or more traditional techniques. In addition, we show that accurately interpreting inorganic geochemical data requires a sound understanding of the main components of the sediment (organic matter, biogenic silica, carbonates, lithogenic particles) and mineral assemblages. Finally, we provide a series of examples illustrating the potential and limits of inorganic geochemistry in paleolimnology. Although the examples presented in this paper focus on lake and fjord sediments, the principles presented here also apply to other sedimentary environments.
|
|
| 2. |
- Löwemark, Ludvig, et al.
(författare)
-
Practical guidelines and recent advances in the Itrax XRF core-scanning procedure
- 2019
-
Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182 .- 1873-4553. ; 514, s. 16-29
-
Tidskriftsartikel (refereegranskat)abstract
- XRF core scanning has evolved to become a standard analytical technique for the rapid assessment of elemental, density and textural variations in a wide range of sediments and other materials, with applications ranging from palaeoceanography, paleoclimatology, geology, and environmental forensics to environmental protection. In general, scanning provides rapid, non-destructive acquisition of elemental and textural variations at sub-millimetre resolution for a wide range of materials. Numerous procedural adaptations have been developed for the growing number of applications, such as analyses of unconsolidated, water-rich sediments, powdered soil samples, or resin bags. Here, practical expertise and guidance from the Itrax community, gained over 15 years, is presented that should provide insights for new and experienced users.
|
|
| 3. |
- Meijer, Niels, et al.
(författare)
-
Loess-Like Dust Appearance at 40 Ma in Central China
- 2021
-
Ingår i: Paleoceanography and Paleoclimatology. - 2572-4517 .- 2572-4525. ; 36:3
-
Tidskriftsartikel (refereegranskat)abstract
- Asian mineral dust has been studied extensively for its role in affecting regional-to global-scale climate and for its deposits, which enable reconstructing Asian atmospheric circulation in the past. However, the timing and origin of the dust deposits remain debated. Numerous loess records have been reported across the Asian continent with ages varying from the Miocene to the Eocene and linked to various mechanisms including global cooling, Tibetan Plateau uplift and retreat of the inland proto-Paratethys Sea. Here, we study the Eocene terrestrial mudrocks of the Xining Basin in central China and use nonparametric end-member analysis of grain-size distributions to identify a loess-like dust component appearing in the record at 40 Ma. This is coeval with the onset of high-latitude orbital cycles and a shift to predominant steppe-desert vegetation as recognized by previous studies in the same record. Furthermore, we derive wind directions from eolian dune deposits which suggest northwesterly winds, similar to the modern-day winter monsoon which is driven by a high pressure system developing over Siberia. We propose that the observed shifts at 40 Ma reflect the onset of the Siberian High interacting with westerly derived moisture at obliquity timescales and promoting dust storms and aridification in central China. The timing suggests that the onset may have been triggered by increased continentality due to the retreating proto-Paratethys Sea.
|
|
