We investigated marine sediment core GS16-204-22CC for increased tephra occurrences and geochemically analysed the major element composition of tephra shards to identify their source volcano(es). In total we observed eight tephra zones of which five concentration peaks show isochronous features that can be used as independent tie-points in future studies. To ensure analytical precision, secondary standards (BCR2g (Basalt) and Lipari Obsidian (Rhyolitic)) were measured at the start and end of each run. Reference values are listed below and in the dataset comment.Standard SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Beam Size Date CommentBCR2g 54.1 2.26 13.5 12.42 - 3.59 7.12 3.16 1.79 0.35 98.49 Wilson (1997) "Wilson S.A. 1997 The collection preparation and testing of USGS reference material BCR-2 Columbia River Basalt: U.S. Geological Survey Open-File Report "std 0.8 0.05 0.2 0.2 - 0.05 0.11 0.11 0.05 0.02 Lipari 74.03 0.02 12.72 1.75 0.08 0 0.72 4.06 5.18 - 98.62 Sparks (1990) "Sparks R.S.J. 1990. – written communication to University of Edinburgh"Lipari 73.72 - 13.04 1.76 - 0.03 0.76 4.06 5.06 - 98.43 Hunt and Hill (1996) "Hunt J.B. Hill P.G. 1996. An inter-laboratory comparison of the electron probe microanalysis of glass geochemistry. Quaternary International 34-36 229-241."

Reference values Standard SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 Total Beam Size Date CommentBCR2g 54.1 2.26 13.5 12.42 - 3.59 7.12 3.16 1.79 0.35 98.49 Wilson (1997) "Wilson S.A. 1997 The collection preparation and testing of USGS reference material BCR-2 Columbia River Basalt: U.S. Geological Survey Open-File Report "std 0.8 0.05 0.2 0.2 - 0.05 0.11 0.11 0.05 0.02 Lipari 74.03 0.02 12.72 1.75 0.08 0 0.72 4.06 5.18 - 98.62 Sparks (1990) "Sparks R.S.J. 1990. – written communication to University of Edinburgh"Lipari 73.72 - 13.04 1.76 - 0.03 0.76 4.06 5.06 - 98.43 Hunt and Hill (1996) "Hunt J.B. Hill P.G. 1996. An inter-laboratory comparison of the electron probe microanalysis of glass geochemistry. Quaternary International 34-36 229-241."