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Tephrochronology of the Greenland ice-cores and the North Atlantic Region during Marine Isotope Stage 4. / Peter Michael, Abbott
Swansea University Author: Peter Michael, Abbott
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The occurrence of several high-magnitude abrupt climatic changes during the last glacial period (~120-10 ka BP) was first recognised within the Greenland deep ice-core records. Subsequent identification of similar climatic variations has demonstrated the potential global significance of these events...
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The occurrence of several high-magnitude abrupt climatic changes during the last glacial period (~120-10 ka BP) was first recognised within the Greenland deep ice-core records. Subsequent identification of similar climatic variations has demonstrated the potential global significance of these events. Three of these millennial-scale events occurred during Marine Isotope Stage (MIS) 4 (~79-59 ka BP), a period characterised by cooler global temperatures. An understanding of the forcing mechanisms and the environmental responses to these events is currently unattainable due to chronological uncertainties and the inability to precisely synchronise disparate records. Tephrochronology, however, has the potential to facilitate high-precision ice-marine correlations by tracing isochronous horizons between different sequences spanning this period. This potential is demonstrated through the construction of the first tephrochronological framework for MIS 4 within the North Atlantic region. Fourteen cryptotephra horizons are identified within the NGRIP and GRIP ice-cores and the MD04-2822 marine core. Both major and trace element compositions are presented for these previously unknown tephra horizons and form the backbone of this framework. In addition, high-precision, independent age estimates have been assigned to the horizons identified within the ice-core sequences. This framework represents a significant first step towards the regional and potentially hemispheric synchronisation of MIS 4 climatic archives. As well as providing the first evidence for the activity of Icelandic volcanic systems during MIS 4, this framework also demonstrates the widespread dispersal of basaltic-trachybasaltic products from the Jan Mayen volcanic region and potentially the deposition of Japanese volcanic material over Greenland. In addition, investigations of laser ablation inductively coupled plasma mass spectrometry have demonstrated that reliable trace element characterisations can be obtained from tephra shards?20 ?m in diameter, which opens up new possibilities for the incorporation of this technique in distal tephra studies.
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