Supplementary Data - Table S8 Major element composition of Gangetic plain bed sediment. Sample Locality Longitude Latitude Date SiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O TiO2 P2O5 LOI Total Al/Si Fe/Si wt% wt% wt% wt% wt% wt% wt% wt% wt% wt% wt% wt% mol:mol mol:mol Karnali-Ghaghara mol NAG 12 Khotiaghat 81.2010 28.3670 75.75 6.76 3.50 0.06 1.79 4.49 1.02 1.48 0.54 0.10 4.29 99.78 0.107 0.035 LO 743 Khotiaghat 81.2010 28.3670 10/08/07 73.76 7.75 2.70 0.05 1.53 4.68 1.24 1.84 0.45 0.12 4.84 98.94 0.125 0.028 BR 355 Ayodia 82.2025 26.8128 15/05/04 77.39 7.12 2.19 0.06 1.38 3.72 1.20 1.73 0.29 0.09 3.61 98.76 0.110 0.022 BR 371 Dohrighat 83.5127 26.2755 16/05/04 75.31 7.66 2.58 0.05 1.62 4.04 1.17 1.86 0.40 0.11 4.24 99.03 0.121 0.026 BR 372 Dohrighat 83.5127 26.2755 16/05/04 60.23 12.52 4.95 0.07 3.32 5.32 1.02 2.98 0.61 0.14 8.34 99.51 0.248 0.063 BR 343 Revelganj 84.5848 25.8195 12/05/04 72.53 8.76 3.24 0.05 1.95 3.94 1.13 2.18 0.44 0.09 4.73 99.04 0.144 0.034 BR 344 Revelganj 84.5848 25.8195 12/05/04 58.24 13.27 5.21 0.08 3.28 5.42 0.94 3.17 0.64 0.14 8.80 99.19 0.272 0.068 BR8115 Revelganj 84.6307 25.7795 18/08/08 79.56 7.03 1.72 0.03 1.17 3.41 1.22 1.87 0.24 0.06 3.79 100.08 0.105 0.017 Rapti NAG 9 Bhabaniyapur 81.7155 28.0661 74.15 8.18 3.48 0.05 1.24 4.13 1.46 1.75 0.75 0.16 4.33 99.68 0.132 0.036 PB 77 Bahlubang 14/07/05 77.47 5.86 4.13 0.11 0.75 4.35 1.50 1.04 1.20 0.32 3.61 100.34 0.090 0.041 BR 364 Gorakhpur 83.3452 26.7367 15/05/04 65.32 12.08 4.71 0.08 1.94 3.79 0.78 2.94 0.62 0.13 6.93 99.32 0.221 0.055 BR 365 Gorakhpur 83.3452 26.7367 15/05/04 83.35 4.93 1.79 0.03 0.66 2.53 0.60 1.24 0.34 0.06 2.87 98.38 0.071 0.016 Narayani-Gandak MO 217 Tribenighat 84.0583 27.5500 20/05/97 68.48 8.44 3.25 0.05 1.77 7.80 1.48 1.89 0.48 0.23 5.97 99.84 0.147 0.036 BR 335 Barauli 84.7452 26.3600 11/05/04 60.62 11.24 4.01 0.06 2.32 7.56 1.39 2.79 0.54 0.14 8.18 98.85 0.221 0.050 BR 336 Barauli 84.7452 26.3600 11/05/04 69.23 9.37 3.00 0.05 1.64 6.12 1.48 2.20 0.40 0.11 5.55 99.14 0.162 0.033 BR 117 Hajipur 85.1883 25.6882 05/08/01 66.01 9.04 3.21 0.05 1.86 7.69 1.29 2.08 0.49 0.12 7.10 98.94 0.164 0.037 BR 310 Hajipur 85.1883 25.6882 07/05/04 67.02 8.53 3.02 0.06 1.82 7.78 1.38 1.95 0.45 0.14 6.64 98.78 0.152 0.034 BR8107 Hajipur 85.1936 25.6793 17/08/08 71.09 10.07 3.22 0.05 1.54 4.25 1.57 2.55 0.38 0.07 4.19 98.98 0.169 0.035 Kosi BR 103 87.2277 25.4244 05/08/01 77.59 10.67 2.97 0.06 1.04 1.37 1.78 2.46 0.39 0.16 1.14 99.63 0.164 0.029 BR 330 Dumarighat 86.7212 25.5399 10/05/04 79.32 10.02 2.19 0.05 0.64 0.87 1.71 2.48 0.23 0.07 0.90 98.46 0.151 0.021 BR 331 Dumarighat 86.7212 25.5399 10/05/04 61.28 16.30 5.96 0.08 2.46 2.29 1.31 3.96 0.74 0.16 4.93 99.46 0.318 0.074 BR 332 Dumarighat 86.7212 25.5399 10/05/04 72.72 12.31 4.11 0.06 1.36 1.39 1.58 2.95 0.49 0.13 2.55 99.63 0.202 0.043 Gomti BR 378 82.9966 25.5772 16/05/04 80.78 7.84 1.70 0.04 0.67 1.90 1.30 2.01 0.23 0.08 2.06 98.60 0.116 0.016 BR 133 82.9966 25.5772 09/08/01 61.03 14.68 5.90 0.09 2.73 2.43 0.96 3.29 0.67 0.15 7.83 99.76 0.287 0.074 Yamuna BR 914 Kanpur 79.7539 26.1306 09/08/09 75.61 8.15 3.12 0.06 1.08 3.83 1.40 1.56 0.84 0.11 3.70 99.46 0.129 0.031 BR 909 Kanpur 79.7530 26.1301 09/08/09 49.84 14.40 7.82 0.14 3.13 7.49 0.67 2.06 0.94 0.16 13.98 100.63 0.345 0.120 BR 347 Allahabad 81.8365 25.4193 14/05/04 63.99 9.92 4.07 0.08 1.58 6.20 1.06 1.95 0.68 0.17 8.86 98.55 0.185 0.048 BR 348 Allahabad 81.8365 25.4193 14/05/04 81.30 6.56 2.01 0.04 0.62 2.83 1.14 1.61 0.33 0.07 2.28 98.79 0.096 0.019 Ganga river BR 905 Kanpur 80.2758 26.6131 08/08/09 83.32 7.52 2.16 0.06 0.78 1.32 1.50 1.59 0.35 0.12 1.55 100.27 0.108 0.020 BR 946 Kanpur 80.2758 26.6131 18/08/09 80.14 8.32 3.59 0.15 1.01 1.80 1.41 1.51 0.63 0.23 1.38 100.16 0.124 0.034 BR 351 Allahabad 81.8830 25.4332 14/05/04 60.72 14.89 5.96 0.09 3.38 2.75 1.16 3.39 0.70 0.14 6.38 99.58 0.293 0.075 BR 352 Allahabad 81.8830 25.4332 14/05/04 78.33 9.04 2.62 0.04 1.25 1.44 1.57 2.19 0.37 0.08 2.02 98.95 0.138 0.025 BR 136 Varanasi 83.0104 25.2989 10/08/01 85.41 6.83 1.72 0.04 0.43 1.19 1.31 1.61 0.23 0.07 1.09 99.93 0.095 0.015 BR 144 Varanasi 83.0104 25.2989 10/08/01 76.27 9.94 2.88 0.04 1.11 2.24 1.63 2.46 0.36 0.12 2.78 99.83 0.156 0.029 BR 382 Varanasi 83.0067 25.2973 17/05/04 82.69 6.92 2.08 0.05 0.69 1.75 1.26 1.42 0.32 0.09 1.36 98.63 0.100 0.019 BR 383 Varanasi 83.0067 25.2973 17/05/04 58.04 14.30 6.43 0.11 2.82 4.11 0.88 2.60 0.83 0.15 8.34 98.61 0.294 0.084 BR8135 Varanasi 83.0246 25.3184 21/08/08 84.88 7.43 2.43 0.08 0.60 1.27 1.37 1.71 0.29 0.07 0.69 100.82 0.105 0.022 BR 124 Patna 85.1458 25.6238 08/08/01 78.39 7.09 3.39 0.11 1.17 3.14 1.06 1.53 0.74 0.14 2.56 99.32 0.108 0.033 BR 306 Patna 85.1508 25.6240 07/05/04 80.01 6.85 2.42 0.06 1.04 2.85 1.11 1.48 0.52 0.11 2.47 98.92 0.102 0.023 BR8138 Manhar bazar 85.5486 25.5486 22/08/08 79.24 7.16 1.92 0.05 0.88 3.08 1.25 1.95 0.30 0.07 3.15 99.03 0.108 0.018 BR 314 Barauni 85.9985 25.3805 08/05/04 56.55 13.74 5.43 0.09 2.87 6.29 1.07 3.19 0.69 0.15 8.85 98.93 0.290 0.073 BR 315 Barauni 85.9985 25.3805 08/05/04 74.44 8.18 2.59 0.05 1.38 4.45 1.33 1.99 0.38 0.09 4.23 99.10 0.131 0.026 BR 317 Barauni 85.9985 25.3805 08/05/04 67.58 10.08 3.66 0.06 1.95 5.20 1.33 2.29 0.62 0.13 5.99 98.88 0.178 0.041 BR 105 Manihari 87.6042 25.3015 68.73 10.11 3.75 0.05 1.88 4.98 1.31 2.18 0.66 0.16 6.05 99.86 0.176 0.042 BR 106 Manihari 87.6042 25.3015 06/08/01 74.97 8.03 2.60 0.04 1.37 4.75 1.32 1.79 0.56 0.14 4.44 100.01 0.128 0.026 BR 322 Rajmahal 87.8405 25.0615 09/05/04 62.07 13.45 5.13 0.09 2.21 4.30 1.09 2.87 0.66 0.15 7.01 99.02 0.259 0.063 BR 324 Rajmahal 87.8405 25.0615 09/05/04 69.37 10.19 3.64 0.06 1.75 4.33 1.38 2.27 0.60 0.14 4.96 98.70 0.175 0.040 Average 74.12 9.33 3.32 0.07 1.46 3.20 1.27 2.08 0.51 0.12 3.88 99.37 0.16 0.04 Uncert 4.18 1.25 0.64 0.01 0.38 0.70 0.08 0.27 0.08 0.02 1.15 0.29 0.03 0.01