Distal ash isochrons throughout Northern Eurasian lake records

The ability to precisely correlate the relative timings of palaeoenvironmental change events between distant sequences is vital if researchers are to answer questions about the synchroneity of such events and link them with causal factors. The Greenland i ce-core records highlight a number of such short lived and climatic events during the last glacial period, and which were of such rapidity that transitions occurred within time periods as short as decades or years. Conventional geological dating technique s such as radiocarbon and optically stimulated luminescence (OSL), with their associated centennial to millennial error ranges, however are lacking in the resolution required to match the resolution of the ice-core records. It is the aim of this project to use a novel approach which has been developed in recent years. The approach utilises fine volcanic ash layers as high-precision time lines or isochrons. The ultra-distal form are microscopic ('microtephras': <100 microns size) and are thus capable of long-range atmospheric transport from various volcanic sources over distances of thousands of kilometres. They can then become deposited and preserved long term in sedimentary archives such as marine and lake sediments, and ice and organic peat. Microteph ra layers in these archives can be detected and extracted by laboratory procedures and geochemically analysed ('fingerprinted') for correlation with the same isochrons elsewhere, thus establishing precise time-lines of the same age. This project intends t o detect the presence of known and new microtephra isochrons within a number of long lake sediment sequences in the northern Ural Mountains region and develop a chronological framework for Arctic Eurasia against which the timings of local palaeoenvironmen tal events can be measured relative to the North Atlantic and European region.