Distribution, sediment magnetism and geochemistry of the Saksunarvatn (10 180 ± 60 cal. yr BP) tephra in marine, lake, and terrestrial sediments, northwest Iceland

• Published in: Journal of Quaternary Science
• Main Authors: Andrews, John T., Geirsdóttir, Aslaug, Hardardóttir, Jórunn, Principato, Sarah, Grönvold, Karl, Kristjansdóttir, Gréta B., Helgadóttir, Gudrún, Drexler, John, Sveinbjörnsdóttir, Arny
• Other Authors: National Science Foundation (USA), Marine Research Institute., Iceland Research Council, Science Funds of the University of Iceland., National Geographic Society.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2002
• Subjects: Greenland; Húnaflóaáll; Saksunarvatn; Greenland ice core; ice core; Iceland; North Atlantic
• Online Access: http://dx.doi.org/10.1002/jqs.727; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjqs.727; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jqs.727

Abstract In 1997, seismic surveys in the troughs off northwest and north Iceland indicated the presence of a major, regional sub‐bottom reflector that can be traced over large areas of the shelf. Cores taken in 1997, and later in 1999 on the IMAGES V cruise, penetrated through the reflector. In core MD99‐2269 in Húnaflóaáll, this reflector is shown to be represented by a basaltic tephra with a geochemical signature and radiocarbon age correlative with the North Atlantic‐wide Saksunarvatn tephra. We trace this tephra throughout northwest Iceland in a series of marine and lake cores, as well as in terrestrial sediments; it forms a layer 1 to 25 cm thick of fine‐ to medium‐grained basaltic volcanic shards. The base of the tephra unit is always sharp but visual inspection and other measurements (carbonate and total organic carbon weight %) indicate a more diffuse upper boundary associated with bioturbation and with sediment reworking. Off northwest Iceland the Saksunarvatn tephra has distinct sediment magnetic properties. This is evident as a dramatic reduction in magnetic susceptibility, an increase in the frequency dependant magnetic susceptibility and ‘hard’ magnetisation in a −0.1T IRM backfield. Geochemical analyses from 11 sites indicate a tholeiitic basalt composition, similar to the geochemistry of a tephra found in the Greenland ice‐core that dates to 10 180 ± 60 cal. yr BP, and which was correlated with the 9000 14 C yr BP Saksunarvatn tephra. We present accelerator mass spectrometry 14 C dates from the marine sites, which indicate that the ocean reservoir correction is close to ca. 400 yr at 9000 14 C yr BP off northwest Iceland. Copyright © 2002 John Wiley & Sons, Ltd.