TRACEing Last Glacial Period (25-80 ka b2k) tephra horizons within North Atlantic marine cores and exploring links to the Greenland ice-cores

Monday, 14 December 2015
Poster Hall (Moscone South)
Peter Michael Abbott1, Siwan Manon Davies2, Adam J Griggs3, Anna J Bourne3, Eliza Cook3, Nicholas J G Pearce4, William E N Austin5, Mark Chapman6, Ian R Hall7, Catriona S Purcell8, James David Scourse8 and Tine Lander Rasmussen9, (1)Swansea University, Geography, Cardiff, United Kingdom, (2)Swansea University, Cardiff, United Kingdom, (3)Swansea University, Swansea, United Kingdom, (4)Aberystwyth University, Aberystwyth, United Kingdom, (5)Scottish Association of Marine Science, Biogeochemistry & Earth Science, Oban, United Kingdom, (6)UEA, University of East Anglia, Norwich, United Kingdom, (7)Cardiff University, Cardiff, United Kingdom, (8)Bangor University, Bangor, United Kingdom, (9)University of Tromsø, CAGE -Centre for Arctic Gas Hydrate, Environment and Climate, Tromsø, Norway
Tephrochronology is a powerful technique for the correlation and synchronisation of disparate palaeoclimatic records from different depositional environments and has considerable potential for testing climatic phasing. For example, the relative timing of atmospheric and marine changes caused by the abrupt climatic events that punctuated the last glacial period within the North Atlantic region. Here we report on efforts to establish a framework of tephra horizons within North Atlantic marine sequences that can correlate these records and if traced in the Greenland ice-cores can act as isochronous tie-lines.

Investigations have been conducted on a network of marine cores from a number of sites across the North Atlantic. Tephra horizons have been identified using cryptotephra extraction techniques more commonly applied to the study of terrestrial sequences. There are two main challenges with assessing cryptotephras in the glacial North Atlantic; i) determining the transportation processes and ii) assessing the influence of secondary reworking processes and the stratigraphic integrity of the isochrons. These processes and their influence are investigated for each cryptotephra using shard size variations, major element heterogeneity and co-variance of IRD input for some cores.

Numerous Icelandic cryptophras have been successfully identified in the marine records and we will discuss the integration of a number of these with an isochronous nature into a marine tephra framework and how potential correlations to the Greenland ice-core tephra framework are determined. Spatial patterns in the nature of tephra records that are emerging from the core network will be highlighted to outline some of the key areas that could be explored in the future. In addition, the synchronisation of multiple North Atlantic records to the Greenland ice-cores using the North Atlantic Ash Zone II to test the synchroneity of an abrupt cooling in the North Atlantic will be discussed.