The Laacher See Tephra discovered in southernmost Sweden

Abstract

We present the first geochemically confirmed finding of the Laacher See Tephra (LST) on the Swedish mainland, now the northernmost extension of the LST. Sediments were sampled at the Körslättamossen fen, southernmost Sweden, and a high‐concentration cryptotephra occurrence (>65 000 shards cm−3) of the LST was found in a sequence of calcareous gyttja. Tephra identification was confirmed by geochemical analysis using field‐emission electron probe microanalysis and through comparison of the results with published LST data from proximal sites and distal sites north‐east of Laacher See. The LST has previously been divided into eruption phases suggested to have spread in several dispersal fans, but it was not possible to confidently determine the phase of the tephra here closer than to the MLST or ULST. The finding of the LST presented here further strengthens the potential of tephrochronological studies in the south Scandinavian region.

Small shards and long distances – three cryptotephra layers from the Nahe palaeolake including the first discovery of Laacher See Tephra in Schleswig-Holstein (Germany)

“…The general characteristics of geochemical composition ( fig. 6), age and morphology of shards are in line with the description from sites in Northern Europe (Davies et al 2005;Mangerud et al 1984;Timms et al 2017;Wastegård et al 2018).…”

“…In combination with finds of LST at Lake Hämelsee (Jones et al 2018) as well as Körslättamossen fen (Larsson and Wastegård 2018) the results of the present study demonstrate that the dispersal envelope of the Laacher See Eruption must be shifted further to the North-West.…”

“…Consequently, we here present the first find of LST in Schleswig-Holsteinpreviously located outside the reconstructed ash plume. The combination of published LST findings from Lake Hämelsee (Jones et al 2018) as well as Körslättamossen fen (Larsson and Wastegård 2018) reveals that the dispersal fan reached further to the North-West than previously assumed (Litt et al 2003;Riede et al 2011;Schmincke et al 1999;Theuerkauf 2003;van den Bogaard and Schmincke 1984). Hence, the detection of LST in Denmark comes within reach, inheriting the potential to correlate important Lateglacial type localities with recent palaeo-environmental investigations.…”

“…The sequence already analyzed palynologically covers spatially as well as temporally the eruptions and (predominantly) fall out zones of e.g. Borobol-type tephra and Penifiler tephra, as well as Askja-S tephra, or Hässeldalen tephra (Davies et al 2012;Davies et al 2003;Pyne-O'Donnell et al 2008;Turney et al 1997;Wastegård et al 2018;Wulf et al 2016). Hence, we here emphasize the high potential of future investigations.…”

“…The advancements in search techniques for non-visible volcanic ash beds, or cryptotephra, has widened the possibilities of searching for additional chronological markers in sediment archives (Blockley et al 2005;Lowe and Hunt 2001;Turney 1998;Turney et al 2004). In this way the detection of non-visible tephra horizons has been extended to further distal sites throughout Europe (Blockley et al 2007;Bramham-Law et al 2013;Haflidason et al 2018;Lane et al 2012b;Larsson and Wastegård 2018;Wastegård and Boygle 2012;Wastegård et al 2000;Wulff et al 2013). To successively increase the temporal resolution of the NAH sediment record a targeted search for well dated cryptotephra horizons was performed.…”