tephra SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O total Ref Hekla 4 Tephra 75.53 0.08 12.97 1.89 0.08 0.06 1.27 4.07 2.80 98.76 969 Hekla 4 Tephra 73.78 0.10 12.94 1.94 0.10 0.05 1.38 4.16 2.83 97.29 969 Hekla 4 Tephra 73.76 0.10 12.84 1.81 0.08 0.04 1.34 4.46 2.94 97.37 969 Hekla 4 Tephra 73.67 0.09 12.59 1.94 0.09 0.05 1.25 4.42 2.79 96.87 969 Hekla 4 Tephra 73.57 0.12 13.05 1.91 0.07 0.06 1.34 4.34 2.77 97.24 969 Hekla 4 Tephra 73.21 0.14 13.10 1.93 0.06 0.05 1.37 4.36 3.04 97.26 969 Hekla 4 Tephra 72.64 0.07 12.80 1.94 0.06 0.03 1.28 4.58 3.05 96.44 969 Hekla 4 Tephra 72.42 0.13 12.64 1.92 0.10 0.06 1.35 4.58 2.86 96.06 969 Hekla 4 Tephra 72.31 0.14 12.68 1.89 0.09 0.07 1.31 4.32 2.78 95.59 969 Hekla 4 Tephra 72.20 0.07 12.39 1.91 0.09 0.05 1.26 4.28 2.82 95.07 969 ------------------------------------------------------------------------ 969: Boygle, J.E. (1994) Tephra in lake sediments: An unambiguous geochronological marker? PhD. Thesis, University of Edinburgh, Edinburgh,