Sedimentological and geochemical investigation of Denmark Strait sediments

Geophysical data from the Kangerlussuaq Trough, E Greenland (Dowdeswell et al., 2010; Stein, 1996), and from the West Iceland shelf (Syvitski et al., 1999) indicate that there are sites where pre Last Glacial Maximum (LGM) sediments exist, but no such sites have been successfully cored. However, a significant number of cores have been recovered that penetrate a basal diamicton, sometimes containing shells and foraminifera, and which are overlain by glacial marine sediments rich in ice rafted debris (IRD) (Jennings et al., 2000; Olafsdottir, 2004). At the LGM, reconstructions and marine field data (Andrews, 2008; Andrews et al., 1998, 2000; Dunhill, 2005; Funder et al., 2004; Hubbard et al., 2006; Vasskog et al., 2015) indicate that the Iceland and Greenland ice sheets were terminating at their shelf breaks with deposition on the slopes above the Denmark Strait. Active sediment deposition ceased on the Kangerlussuaq Trough Mouth Fan (KTMF) ca. 15.3 ka 14C BP (Andrews et al., 1998; Dunhill, 2005) and retreat to the present coastline occurred prior to deposition of the Vedde tephra (Jennings et al., 2006). There is strong evidence that a major change in deep-water circulation at ~15 cal ka BP resulted in abrupt warming at the onset of the Bølling/Allerød (B/A) interstadial (Thiagarajan et al., 2014; Thornalley et al., 2011). Syvitski et al (1999) and Norddahl and Ingolfsson (2015) argued that the Iceland Ice Sheet retreated rapidly during this time, driven by a rapid rise in relative sea level. Jennings et al. (2006) also presented radiocarbon evidence from marine cores for a rapid retreat of the Greenland Ice Sheet along Kangerlussuaq Trough (KT, Fig. 1).