Jökull - 01.01.2012, Blaðsíða 55

Reviewed research article
Holocene marine tephrochronology on the Iceland shelf:
An overview
Esther Ruth Guðmundsdóttir1,2 Jón Eiríksson1,3 and Guðrún Larsen1
1Institute of Earth Sciences, University of Iceland, Askja, Sturlugata 7, IS-101 Reykjavík, Iceland
2The Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland
3University of Copenhagen, Centre for GeoGenetics, Natural History Museum, Copenhagen, Denmark
Corresponding author: estherrg@hi.is
Abstract – Currently the Late-glacial and Holocene marine tephrochronology on the shelf around Iceland
comprises 130 tephra layers from 30 sediment cores ranging in age from 15,000 years cal. BP to AD 1947. A
vast majority of the cores and tephra layers are from the North Iceland shelf. Much fewer tephra layers have
been found on the South and West Iceland shelf. The early Holocene Saksunarvatn ash and Vedde Ash are the
only tephra layers identified on all investigated shelf areas. For the last 15,000 years correlated tephra layers
from the shelf sediments around Iceland to their terrestrial counterparts both in Iceland and overseas are 40 of
which 26 are terrestrially dated tephra markers. Thirty correlations are within the last 7050 years. The terres-
trially dated tephra markers found on the shelf have been used to constrain past environmental variability in the
region, as well as marine reservoir age. The marine tephra stratigraphy on the North Iceland shelf has revealed
variations in volcanic activity in Iceland further back in time than terrestrial records in Iceland. The numerous
tephra layers identified in the sediments on the shelf demonstrate the potential of marine tephrochronology for
dating purposes, land-sea correlation, marine reservoir estimations and reconstruction of past volcanic activity
of Icelandic volcanoes.
INTRODUCTION
The application of tephrochronology is twofold; as a
tool in volcanology, deciphering volcanic history and
as a stratigraphic dating tool, using layers of tephra
as time parallel marker horizons. In recent times
tephrochronology (sensu lato) has been adopted as a
general term used broadly to describe all aspects of
tephra studies (Lowe, 2011). The term tephra was
brought to modern terminology by Sigurður Þórarins-
son in 1944 and is a collective term for all airborne
pyroclasts produced in volcanic eruptions regardless
of size and shape.
Tephrochronology has been a growing field in
geology. The reason for the increased interest in
tephrochronology is the unique ability of the method
to precisely link and date geological, palaeoecolog-
ical, palaeoclimatic or archaeological sequences or
events. Not many methods if any can match the pre-
cision it offers temporally and spatially (Lowe, 2011).
Tephrochronology has proven to be one of the prin-
cipal chronological tools for dating Quaternary se-
quences. This is demonstrated in globally impor-
tant projects such as INTIMATE (Integrating ice-core,
marine and terrestrial global records 60,000 to 8,000
years ago) (Turney et al., 2004; Davies et al., 2012)
SMART (Synchronizing marine and ice-core, marine
records using tephrochronology) (Abbott et al., 2011;
Abbott and Davies, 2012), SUPRAnet, (Studying un-
certainty in palaeoenvironmental reconstructing – a
net) (Lowe, 2008), HOLSMEER, Millennium (Eiríks-
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