New findings regarding the Saksunarvatn Ash in Germany C. W. F. BRAMHAM-LAW, 1 * M. THEUERKAUF, 2 C. S. LANE 1 and J. MANGERUD 3 1 Research Laboratory for Archaeology and History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford OX1 3QY, UK 2 Institute for Geography and Geology, University of Greifswald, Germany 3 Department of Earth Sciences & Bjerknes Centre for Climate Research, University of Bergen, Norway ABSTRACT: The Saksunarvatn Ash is an important tephra layer for the correlation of Early Holocene environmental records in northern Europe, the North Atlantic and Greenland. The Saksunarvatn Ash is believed to have been produced by eruptions of the Grimsvo ¨ tn volcanic system 10.3 ka BP, which had two axes of dispersal, one plume in a north-west direction over northern Iceland and into Greenland, and a second southerly plume covering the Faroe Isles, Shetland Isles, western Norway and northern Germany. Here we present data from Potremser Moor, north-east Germany, extending the easterly margin of the ash fallout zone. We also present single grain trace element data from the type site at Saksunarvatn as well as from Potremser Moor. The Saksunarvatn Ash is indistinguishable between Potremser Moor and Saksunarvatn, suggesting the two tephras were produced by the same eruption. Trace element compositions from both sites are similar to data from the North Atlantic marine core (LINK 14:185), but different from the GRIP ice core (GRIP 1528.61 m), indicating that the south-east and north- west plumes may have arisen from separate eruption events. Copyright # 2013 John Wiley & Sons, Ltd. KEYWORDS: cryptotephra; Holocene; Potremser Moor; Saksunarvatn Ash; tephrochronology. Introduction High-resolution palaeoclimate archives, such as the Greenland ice core records, have demonstrated that climatic oscillations during the Lateglacial–Holocene transition were both complex and abrupt, occurring over centennial and even decadal time frames (Alley et al., 1993; Dansgaard et al., 1993; Kapsner et al., 1995; Rasmussen et al., 2006; Steffensen et al., 2008). This poses the challenge to scientists to determine the phasing of the palaeoenvironmental responses recognized across ice core, terrestrial and marine archives. Age models are most frequently generated by radiocarbon dating in the terrestrial and marine realms and these typically have centennial error ranges. A method that is increasingly employed in resolving these chronological issues is the use of, often invisible, volcanic ash layers (tephra, or cryptotephra). Tephra layers are deposited instantaneously, forming widespread isochrones that can be used to make correlations between sites, independent of other dating techniques (Mangerud et al., 1984; Turney et al., 2006; Brooks et al., 2012). Whilst the most explosive eruptions disperse ash over thousands of kilometres (e.g. Lane et al., 2011a), the distribution of tephra within sedimentary records is frequently discontinuous owing to atmospheric dynamics, sedimentation and preservation processes within varied landscapes (Boygle, 1999; Lawson et al., 2012; Pyne O’Donnell, 2011). The Icelandic Saksunarvatn Ash (SA) provides an example of the widespread but discontinuous nature of cryptotephra deposition. The SA was first described from the bog Hoydalar on the Faroe Islands (Jo hansen, 1975; Waagstein and Jo hansen, 1968). Subsequently, Jo hansen (1978, 1981, 1985) correlated an ash bed within Lake Saksunarvatn, also on the Faroe Islands, to the ash at Hoydalar. Further analysis, including microprobe analysis of the ash from Saksunarvatn by Mangerud et al. (1986), led to the ash being named the ‘Saksunarvatn Ash’, as the ash in Saksunarvatn was thicker, better dated and with existing samples, in contrast to the first finding at Hoydalar. Since then, tephra layers correlating with the SA have been identified within terrestrial, marine and ice core records across the North Atlantic region (Fig. 1) (Haflidason et al., 1990; Sjøholm et al., 1991; Merkt et al., 1993; Birks et al., 1996; Zielinski et al., 1997; Andrews et al., 2002; Lind and Waste- ga ˚rd, 2011). Whilst the SA is one of the most far-travelled Icelandic basaltic ash layers, being well represented in the Faroe Islands (Waagstein and Jo hansen, 1968; Jo hansen, 1981, 1985), the Shetland Islands (Bondevik et al., 2005) and Norway (Birks et al., 1996; Aarnes et al., 2012), it is relatively under- represented on continental Europe, with only two sites in northern Germany to date having confirmed geochemical representation (Merkt et al., 1993; Fig. 1). The SA has been dated using the GICCO5 timescale to 10 297  45 a BP (Rasmussen et al., 2006) and to 10 210  35 cal a BP in Kra ˚kenes, Norway (O. S. Lohne et al., 2013). Aims 1. To extend the known geographical ash footprint of the SA by documenting its presence in north-east Germany to the east of the last findings in central Europe by Merkt et al. (1993). 2. To fully chemically characterize the SA from the Saksunarvatn type site, using major, minor and trace element analysis. 3. To test chemical correlation of SA findings in Germany, the Faroe Islands and Greenland and re-evaluate the correlation of SA dispersal envelopes Study site Potremser Moor (53.991213˚N, 12.275659˚E) is an in-filled lake located in the Mecklenburg–Vorpommern region of Germany (Fig. 1). The former lake is located in an upland area surrounded by low hills and is 15 ha in size. Today the site is covered by acidic, mesotrophic birch woodland with Sphagnum in the field layer. In September 2007 a 570-cm core was extracted from the site with a section from 410–530 cm analysed for pollen and cryptotephra analysis. The lower portion of the core from 486–530 cm is composed of a clayey *Correspondence: C. W. F. Bramham-Law, as above E-mail: cassian.bramhamlaw@rlaha.ox.ac.uk Copyright # 2013 John Wiley & Sons, Ltd. ISSN 0267-8179. DOI: 10.1002/jqs.2615 JOURNAL OF QUATERNARY SCIENCE (2013) 28(3) 248–257