Tephrochronology absolute dating
The best available age estimates for the Laacher See Tephra and Vedde Ash layers are incorporated into a revision of the radiocarbon-based Bayesian age-model for the last glacial to interglacial transition at Soppensee, which is used to explore synchronicity of climatic events between Europe and the North Atlantic.
Local temperature changes, recorded by biotic and abiotic proxies in Soppensee, appear to shift in phase with the oxygen isotope signal in Greenland at the onset of the Younger Dryas; however with the clarity of improved precision, an apparent offset that likely results from a dating artefact, is seen between records at the termination of the stadial event.
From a methodological standpoint, the results clearly show that only by establishing detailed and independent chronological frameworks can abrupt climatic variability be compared between different regions with sufficiently high temporal precision to addresses the notion of hemispheric climatic synchronicity at the centennial scale in the Late Quaternary.
Doctoral School of Earth Sciences and Ecology in cooperation with the Department of Geology, Institute of Ecology and Earth Sciences Tartu University are organizing Ph D training course‚Dating methods and their application’ in March 2-5, 2015.
Invited lecturers from dating labs of different universities will give lectures and practical classes with introduction to calculation, calibration tools and software.
Set of ‚absolute’ (radiocarbon, OSL, cosmogenic nuclides, dendrochronology, varve chronology) and relative dating (tephrochronology, palaeomagnetism) techniques and their applications will be introduced during the course.
The tephrostratigraphy of Soppensee, Switzerland, is presented here for the first time, with new geochemical data for four tephra layers, derived from three volcanic centres.
Speleothem studies are beginning to identify various geochemical signatures of tephra layers related to known explosive volcanic events. To establish a reliable speleothem tephrochronological absolute dating tool, researchers must develop a mechanistic understanding of the processes that govern the deposition, preservation, and geochemical composition of speleothem tephra marker horizons.
A large increase in diverse trace elemental impurities was found to correspond to the regional ashfall from the April 1982 V. Here we present results from an experimental simulation of early stage weathering of trachyandesitic tephra.Volcanic ash from the 1982 El Chichon eruption was obtained from the Smithsonian Institution for leaching experiments.Using a factorial design, aliquots of a weak nitric acid solution were exposed to fine (less than 64 micron) and bulk ash samples, both alone and in the presence of karst soil from Belize.Mixtures were filtered to separate the solid fraction from the leachate, and ICP-MS analysis was performed on the suite of leachate samples at Boston University.We discuss the experimental results with respect to the geochemical composition of the tephra and observed stalagmite cryptotephra layer.
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We also address implications for development of an absolute dating tool for Quaternary geochronolgy and paleoclimatology of speleothems.