A tephra based marine-ice core synchronization of the GS-9/GIS-8 transition (38-40.5 ka b2k)

Determination of the key physical processes involved in abrupt climate changes increasingly depend on integrated studies of paleoclimatic records from disparate climate archives. However, to identify coinciding rapid transitions and isolate the controlling mechanisms, it is fundamentally important to constrain, as precisely as possible, the timing, phasing and lead/lag issues of such events. Hence, prior to integrated studies, an independent high-precision cross-dating and synchronization of the different paleoclimatic records is required. As tephra is deposited instantaneously and are geochemically distinct, they can form isochrones or time-parallel marker horizons and thus comprise a key correlation, synchronization and dating tool. Previously, Bourne et al. (2013) reported ice core (i.e., NGRIP; NEEM) evidence of 14 separate volcanic events spanning the GS-9/GIS-8 transition (38-40.5 ka b2k). Although these horizons all fall geochemically within the compositional range of the FMAZ III, differences in their TiO2 values allow them to be discriminated from one another. Hence, when similar stratigraphically separated volcanic horizons can be detected in marine sediments, this provides the potential for marine-ice core cross-correlation and thereby, precise age constraints of this time interval. Here, we investigate the potential existence of such a similar suite of layers within a marine sediment core with an exceptional high sedimentation rate (MD99-2284). Tephra concentrations of different size fractions were counted using light microscopy. Stratigraphically separate volcanic horizons were then analyzed using electron-probe microanalysis with a special focus on the TiO2 content. Preliminary results argue for 3 distinct volcanic layers, which may be cross-correlated to the Greenland ice cores. As a result, we potentially achieve a more precise constraint on the timing and duration of the GS-9/GIS-8 transition which improves the interpretation of multi-proxy data representing atmospheric and oceanic processes involved in abrupt climatic events and thereby, the understanding of potential mechanisms behind them. Bourne, A.J. et al., 2013. Journal of Quaternary Sciene 28(7), 641-646