Jökull - 01.01.2012, Blaðsíða 78

S. Wastegård and J. Boygle
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Den.
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16°E
60°N
Malmö
Göteborg
Stockholm
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Sundsvall
YD m
orai
nes
Gotland
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Figure 1. Map showing locations in Sweden that
have been investigated for tephrochronology. Most
Holocene sites (hollow dots) are bogs and LGIT
sites (black diamonds) are either lakes or infilled
basins with lake sediments in the bottom. Numbers
refer to sites in Table 2. The complete stratigraphy
has only been investigated in a few sites. – Kort
af stöðum sem hafa verið kannaðir með tilliti til
gjóskulaga í Svíþjóð. Flestir staðanna frá nútíma
(opnir hringir) eru mýrar, en staðir frá lokum síðasta
jökulskeiðs (svartir tíglar) eru annað hvort stöðuvötn
eða dældir með stöðuvatnaseti á botni. Tölur vísa til
staðarnafna í töflu 2. Jarðlagaskipan hefur einungis
verið rannsökuð á nokkrum stöðum.
Two significant new additions to the LGIT
tephrochronological frameworks of NW Europe are
the Hässeldalen (ca. 11.3 ka BP) and Askja-S tephras
(ca. 10.4 ka BP) that were first reported from the
Hässeldala port site in SE Sweden by Davies et al.
(2003). The Askja-S Tephra (also reported as the
Askja 10-ka Tephra) has earlier been described from
Iceland (Sigvaldason, 2002) but no earlier records
have been made of the Hässeldalen Tephra. Since this
first record, these two tephras have emerged as impor-
tant regional isochrones in NW Europe for the early
Holocene (Lind and Wastegård, 2011; Davies et al.,
2012; Lane et al., 2012). Both tephras occur in close
association to rapid climatic events and will be central
to the goals of the INTIMATE project which aims to
integrate ice-core, marine and terrestrial records from
the time period between 60 and 8 ka BP (Blockley et
al., 2012; Davies et al., 2012). Recent investigations
confirm that the Hässeldalen tephra is widespread in
the southern Baltic Sea region (Lane et al., 2012; Lilja
et al., in press).
The only layer from the early part of the
Lateglacial period is a tephra that was originally cor-
related with the Borrobol Tephra, ca. 14.0 ka BP
(Davies et al., 2003), previously found in lateglacial
sequences in Scotland (Turney et al., 1997). How-
ever, later investigations of the Hässeldala port se-
quence indicate that the tephra found in Sweden more
likely correlates with the slightly younger Penifiler
Tephra (ca. 13.8 ka BP) that has the same major el-
ement geochemistry as the Borrobol Tephra (Davies
et al., 2004; Pyne-O’Donnell, 2007). However, the
issue of possibly two or three different tephras with
similar geochemical composition in the early part of
the Greenland Interstadial 1 (GI-1) is not yet fully re-
solved (Matthews et al., 2011).
THE MIDDLE TO LATE HOLOCENE
(c. 7 ka BP-present)
Persson (1966, 1971) investigated several peat bogs
in western central Sweden for possible occurrences
of tephra. He noted three or four peaks in tephra
concentration in many bogs and with help of meth-
ods such as refractive indices and grain size distribu-
76 JÖKULL No. 62, 2012