tephra SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 total Ref Hekla 4 Tephra 73.68 0.10 13.03 1.93 0.07 0.01 1.31 3.97 2.74 0.01 96.85 4822 Hekla 4 Tephra 72.56 0.12 12.80 1.94 0.12 0.04 1.32 3.71 2.70 0.01 95.32 4822 ------------------------------------------------------------------------ 4822: Wulf, S. Dräger, N. Ott, F. Serb, J. Appelt, O. Guðmundsdóttir, E. van den Bogaard, C. Slowinski, M. Laszkiewicz, M. and Brauder, A. (2016) Holocene tephrostratigraphy of varved sediment records from Lakes Tiefer See (NE Germany) and Czechowskie (N Poland). Journal of Quaternary Science 32, 1-14.