A wide variety of methods exists to date paleosols and to derive past environmental conditions. Past climatic and environmental conditions can be characterized by using magnetic properties of soils that present the situation under which conditions they formed. The distribution of stable carbon isotopes and carbon along profiles give a hint about soil surface processes. The combined use of δ13C and δ18O in sediments or soils indicates local or regional environmental conditions that clearly deviate from global signals. Each dating method has its own specific limitations. A powerful tool to reconstruct past environments is the radiocarbon dating of macrofossil charcoal fragments buried within soil profiles. Also soil organic matter offers some possibilities for dating; however, an age determination of bulk samples is often not that conclusive due to the high variability of organic matter composition. Depositional events of a sediment can be revealed by luminescence dating. Methodological progress has provided a powerful toolset to identify incomplete bleaching (quartz, feldspar) and to correct for its effects in age calculation. Terrestrial cosmogenic nuclides (such as 10Be, 26Al, 36Cl, 14C, etc.) have substantially improved the dating accuracy of the geomorphic surfaces on which paleosols have developed. Besides in situ produced also meteoric 10Be can be reasonably well used for dating soil surfaces. The application of paired nuclides, such as in situ 10Be and 26Al or 14C, each with a different half-life, allows for a deeper understanding of complex timing patterns of soil and rock surface exposures.

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Paleoecological Methods and Dating of Paleosols

  • Markus Egli,
  • Dennis Dahms

摘要

A wide variety of methods exists to date paleosols and to derive past environmental conditions. Past climatic and environmental conditions can be characterized by using magnetic properties of soils that present the situation under which conditions they formed. The distribution of stable carbon isotopes and carbon along profiles give a hint about soil surface processes. The combined use of δ13C and δ18O in sediments or soils indicates local or regional environmental conditions that clearly deviate from global signals. Each dating method has its own specific limitations. A powerful tool to reconstruct past environments is the radiocarbon dating of macrofossil charcoal fragments buried within soil profiles. Also soil organic matter offers some possibilities for dating; however, an age determination of bulk samples is often not that conclusive due to the high variability of organic matter composition. Depositional events of a sediment can be revealed by luminescence dating. Methodological progress has provided a powerful toolset to identify incomplete bleaching (quartz, feldspar) and to correct for its effects in age calculation. Terrestrial cosmogenic nuclides (such as 10Be, 26Al, 36Cl, 14C, etc.) have substantially improved the dating accuracy of the geomorphic surfaces on which paleosols have developed. Besides in situ produced also meteoric 10Be can be reasonably well used for dating soil surfaces. The application of paired nuclides, such as in situ 10Be and 26Al or 14C, each with a different half-life, allows for a deeper understanding of complex timing patterns of soil and rock surface exposures.