Stratigraphy and distribution of tephra layers in marine sediment cores from the Faeroe Islands, North Atlantic

The stratigraphical position of eight discrete tephra layers is investigated in four marine sediment cores from north and south of the Faeroe Islands. The tephras are correlated to the marine oxygen isotope stratigraphy and the interstadial/stadial cycles (Dansgaard–Oeschger cycles) of the Greenland ice cores. A very prominent volcanic event occurred during interstadial 23 in Marine oxygen Isotope Stage (MIS) 5c correlating with a cold event within this otherwise warm interval. Two tephra horizons in MIS 5a correlate with the beginning and end of interstadial 21, respectively. The most widely distributed ash is the well-known Ash Zone 2 from the lower part of MIS 3. In the two cores from north of the Faeroe Islands, it consists of two discrete layers, a lower one composed of rhyolitic and basaltic tephra and an upper layer composed exclusively of basaltic glass. The two tephra falls coincide with the two warm intervals of Dansgaard–Oeschger cycle No. 15. A hitherto unknown basaltic tephra was recorded just above Heinrich event H4 in the lower part of the warm interstadial 8 and dated to ca. 33 14C ka BP. Another frequently recorded layer termed the Fugloyarbanki Tephra is likewise basaltic. It is dated to 23.1 14C ka BP. It was deposited after the peak warm phase of interstadial 3 at the MIS 3/2 transition. Finally, a tephra dated ca. 15.4 14C ka BP was found in two cores from north of the ridge. It was deposited at the beginning of the deglaciation between the Last Glacial Maximum and Heinrich event H1.