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Not so non-marine? Revisiting the Stoer Group and the Mesoproterozoic biosphere

E.E. Stüeken1,2,3,

1School of Earth and Environmental Sciences, Uniizrsity of St. Andrews, St. Andrews, Fife, KY16 9AL, Scotland, UK
2Department of Earth Sciences, University of California, Riverside CA 92521, USA
3Virtual Planetary Laboratory, University of Washington, Seattle WA 98195, USA

E.J. Bellefroid4,

4Department of Geology and Geophysics, Yale University, New Haven CT 06520, USA

A. Prave1,

1School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, Fife, KY16 9AL, Scotland, UK

D. Asael4,

4Department of Geology and Geophysics, Yale University, New Haven CT 06520, USA

N.J. Planavsky4,

4Department of Geology and Geophysics, Yale University, New Haven CT 06520, USA

T.W. Lyons2

2Department of Earth Sciences, University of California, Riverside CA 92521, USA

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Stüeken, E.E., Bellefroid, E.J., Prave, A., Asael, D., Planavsky, N.J., Lyons, T.W. (2017) Not so non-marine? Revisiting the Stoer Group and the Mesoproterozoic biosphere. Geochem. Persp. Let. 3, 221-229.

NASA postdoctoral program (EES), Lewis & Clark Fund (EES), NSF Earth-Life Transition program (TWL, NJP), NSF Frontiers in Earth System Dynamics program (TWL), NASA Astrobiology Institute (TWL, NJP), NSERC PGS-D grant (EJB).

Geochemical Perspectives Letters v3, n2  |  doi: 10.7185/geochemlet.1725
Received 10 November 2016  |  Accepted 15 May 2017  |  Published 13 June 2017
Copyright © 2017 European Association of Geochemistry




Figure 1 Stratigraphy of the Poll a’Mhuilt Member. EUX = euxinic interval. The horizon at 5.6 m (red symbols) was affected by modern oxidative weathering and is not considered in the discussion. Black arrows = locations of tidal indicators.
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Figure 2 Sedimentary features compatible with a marine setting in the middle Poll a’Mhuilt Member. (a) Flaser- and lenticular-bedding. (b) Superposed sets of herringbone cross-lamination, 3D exposures confirm bi-directional character. Stratigraphic positions are marked in Figure 1. (c) Line drawing of sedimentary features showing superposed sets of bi-polar cross-laminated ripples (herringbone) with multiple reactivation surfaces commonly with thin clay drapes.
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Figure 3 (a) Iron speciation, (b) carbonate C and O isotopes, and (c) carbonate-bound Sr isotopes. Dashed lines in (a) mark redox transitions (Poulton and Canfield, 2011

Poulton, S.W., Canfield, D.E. (2011) Ferruginous conditions: a dominant feature of the ocean through Earth's history. Elements 7, 107–112.

). For comparison to our data in panel (b), values of contemporaneous unaltered marine carbonates fall between -10 ‰ and -7 ‰ for δ18Ocarb and 0 ‰ and +2 ‰ for δ13Ccarb (Shields and Veizer, 2002

Shields, G., Veizer, J. (2002) Precambrian marine carbonate isotope database: Version 1.1. Geochemistry Geophysics Geosystems 3, doi: 10.1029/2001GC000266.

) (see Fig. S-2 for discussion). In panel (c), data points represent individual leaches increasing acid strength; y-axis intercept = carbonate end-member.
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Supplementary Figures and Tables


Table S-1 Organic carbon isotopes and abundances. TOC = total organic carbon, RE = relative error, SD = standard deviation.
position TOCREδ13CorgSD
[m] [%] [%][‰][‰]
2.730.014.73-27.221.14
2.770.024.62-26.480.28
2.830.012.46-26.800.23
2.870.010.21-25.980.62
3.70.0115.62-28.110.84
4.10.022.71-28.680.00
4.380.041.44-28.850.12
4.420.072.61-29.730.05
4.650.120.33-30.960.07
4.750.361.02-31.230.08
4.90.340.44-30.860.01
5.30.321.10-30.500.01
5.450.280.51-30.380.01
5.60.120.79-29.940.05
5.650.280.36-30.290.05
5.80.171.70-30.330.04
6.50.020.06-26.270.46
7.10.015.30-25.040.14
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Table S-2 Carbonate carbon and oxygen isotopes and carbonate abundances (carb.). SD = standard deviation, carb = carbonate content by weight, RE = relative error.
position δ13CcarbSDδ18OcarbSD % carb.RE
[m][‰][‰][‰][‰]
[%]
2.73-1.940.01-16.360.0312.80.9
2.77-1.780.00-16.310.0218.02.8
2.83-1.540.01-16.300.0015.35.5
2.87-1.220.04-16.390.0219.00.3
4.10-1.140.01-16.250.0121.80.8
4.38-0.900.00-16.300.0028.33.8
4.42-0.610.01-16.200.0233.35.1
4.65-1.350.00-15.940.005.72.6
4.75-1.250.01-16.280.0110.62.2
4.90-1.160.00-16.380.0316.68.4
5.30-0.230.00-16.150.0021.01.5
5.450.020.01-16.050.0519.70.0
5.60-0.520.00-16.180.0315.40.5
5.65-0.270.01-15.930.0116.60.4
5.80-0.860.01-16.010.0312.60.7
6.50-2.020.01-15.060.0213.20.5
7.10-2.120.01-16.240.0213.06.2
16.050.580.01-15.860.017.37.2
16.850.65
-15.75
7.5
20.450.58
-16.00
5.7
22.750.77
-15.57
7.7
24.550.880.02-15.570.029.70.2
25.750.96
-15.67
6.4
25.951.03
-15.65
7.0
27.551.07
-15.84
6.6
29.151.150.00-15.470.026.37.0
30.951.16
-15.71
4.7
32.951.16
-15.54
5.4
34.251.160.02-15.960.036.90.1
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Figure S-1 Photomicrographs of the Poll a’Mhuilt Member. (a) Sample +2.77 m, plane-polarised light; calcareous red shale with 18 % CaCO3 present as microcrystalline laminae, separated by iron-oxide coated siliciclastics. (b) Sample +4.42 m, plane-polarised light; calcareous red shale with 33 % CaCO3 present as disrupted microcrystalline laminae and rare sparry fenestral fillings. (c) Sample +5.30 m, plane-polarised light; calcareous grey shale with 21 % CaCO3 present as microcrystalline laminae, separated by kerogenous siliciclastics. (d) Sample +25.75 m, crossed polars; partially desiccated facies with 6 % CaCO3 present as microcrystalline nodules and cement, stained with iron oxide, separated by iron-oxide coated siliciclastics. All samples contain angular silt grains composed of quartz, plagioclase, and K-feldspar and minor mica.
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Figure S-2 Stratigraphic section through the Poll a’Mhuilt Member with carbonate C and O isotopes. Lithostratigraphy, Mo, Cr, CaCO3 and TOC abundances are as in Figure 1 in the main text. The last panel shows δ18O and δ13C in carbonate in stratigraphic context. The trend highlights that the heaviest values in both isotopic proxies occur in the upper red shale. This is consistent with the high abundance of desiccation cracks in this part of the section, because evaporation forces these parameters to heavier values. The grey shale, which would have been most continuously flooded, shows relatively light values, consistent with a relatively lesser impact of evaporation. Despite the high degree of evaporation that is implied by the presence of gypsum pseudomorphs in the section (Stewart, 2002; Parnell et al., 2010) the δ18O values are overall light compared to other mid-Proterozoic carbonates of similar age (Shields and Veizer, 2002; Bartley and Kah, 2004), which we attribute to fluid alteration. Oxygen isotopes are much more easily reset than carbon isotopes. However, the overall trend towards heavier values in the most evaporitic part of the section is preserved.
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Table S-3 Bulk elemental abundances. The grey shale unit extends from +4.75 m to +5.8 m; the sample from +5.6 m is likely altered by modern weathering. Samples below 0 m are from the Stac Fada Member and contain volcanic fragments. Abundances are in weight-percent or parts per million (μg/g).
positionNaMgAlPK CaTiVCrMnFeCoNiCuZnAsSrMoCdPbThU
[m][%][%][%][%][%][%][%][ppm][ppm][ppm][%][ppm][ppm][ppm][ppm][ppm][ppm][ppm][ppm][ppm][ppm][ppm]
Poll a'Mhuilt section:
-5.003.362.236.780.071.800.460.3772.3217.3712.94.4329.8400.69.878.62.4170.00.40.09.64.10.7
-4.503.322.377.320.071.510.610.3870.0156.7774.73.8825.3270.810.770.11.6202.20.40.07.33.40.7
0.003.032.558.180.071.970.830.4989.9139.9694.75.3624.6178.812.596.65.5133.10.30.011.66.31.2
0.503.981.866.400.081.400.940.4897.9128.0654.54.0125.4170.816.173.73.9136.60.80.09.15.41.4
0.753.591.887.660.051.511.450.3666.1117.5625.73.8718.8136.416.169.93.6109.10.60.09.04.81.2
1.654.451.336.920.080.931.890.3982.3139.8540.93.4817.5170.316.147.54.5107.30.40.07.44.20.7
2.052.981.606.340.101.981.040.4695.2130.6529.05.4523.7165.716.188.86.587.70.70.09.16.22.2
2.734.221.868.830.081.015.630.48114.2114.41025.63.7021.194.316.163.64.2116.10.50.014.45.55.2
2.773.321.417.220.071.157.490.4387.998.21062.42.9318.284.816.152.72.8107.30.40.124.25.03.8
2.801.783.278.740.102.770.580.56115.9134.2663.15.8739.5197.516.1103.95.576.10.50.024.28.13.2
2.832.611.877.210.091.675.800.5496.5116.01125.63.8427.4129.616.178.44.3101.10.60.119.45.54.7
2.873.121.787.190.071.387.580.4389.4110.01142.63.2322.7128.016.164.22.3111.70.20.011.75.53.8
3.202.442.357.800.081.481.330.4587.8127.7554.15.1518.6140.616.161.12.6116.50.50.09.66.51.5
3.702.692.087.390.071.921.090.4682.2119.6589.74.5715.8136.816.176.41.7277.30.40.06.45.81.6
4.102.740.955.990.051.526.950.2880.083.9960.92.7310.886.116.145.14.6107.11.30.015.04.44.9
4.382.621.075.340.070.6910.690.32100.8100.41171.72.9516.999.616.148.73.1142.50.70.113.84.64.7
4.422.420.854.600.070.7012.840.3282.383.61176.72.1412.978.516.135.73.8161.91.10.112.04.15.8
4.652.492.056.880.111.622.360.53150.9117.5622.53.5912.1127.016.174.12.3119.21.70.09.96.77.7
4.753.061.816.740.091.264.150.45174.3110.3824.34.2726.0106.116.188.018.5110.289.20.332.76.48.5
4.902.841.756.390.081.015.850.43153.495.2925.04.4136.1100.916.197.015.7168.4122.20.424.85.97.1
5.302.671.565.790.081.247.780.41138.2100.8962.73.2715.398.016.1197.93.4163.823.50.95.46.05.5
5.452.521.876.530.071.087.370.39121.693.61205.24.4820.6110.216.1137.127.994.4166.21.850.65.83.8
5.602.391.878.710.092.195.730.46119.1100.1880.14.4819.0105.016.1150.92.2154.31.10.34.96.13.4
5.652.781.726.070.081.286.190.46119.197.61128.94.2921.6100.516.1110.626.183.4106.17.467.86.24.3
5.802.342.026.960.081.585.040.40125.495.5882.53.4723.385.616.179.511.0142.89.30.213.26.33.7
6.501.652.306.840.062.215.140.4876.685.21056.24.1215.175.716.199.50.2147.01.10.14.07.01.9
7.102.651.776.790.061.385.180.4169.992.4919.34.0513.362.516.167.72.587.30.40.05.75.71.4
12.101.492.928.460.093.290.800.57157.0114.3583.15.8323.9101.616.199.925.566.41.40.016.312.24.0
13.051.143.178.770.063.831.900.41110.6106.9702.26.3424.6102.116.199.715.652.41.30.117.310.53.3
14.651.362.357.160.083.022.330.47121.7101.0778.95.5823.498.816.191.710.169.60.90.015.410.83.3
16.051.822.357.240.093.072.990.45123.5111.9794.75.4022.9103.516.186.413.2100.21.10.115.59.63.1
16.851.462.376.880.092.973.120.51114.4104.0824.55.3422.299.516.189.59.293.30.90.115.09.33.0
20.451.822.446.890.092.882.650.54111.5108.3685.45.6623.1107.216.181.68.798.81.20.114.38.72.7
22.751.552.778.570.093.053.170.48111.7110.5787.15.2423.0102.316.198.67.695.51.20.114.18.42.7
24.551.752.136.520.092.734.220.46110.4116.4922.85.0822.3103.816.182.39.799.80.80.113.98.62.7
25.751.392.698.090.083.142.780.40121.8152.9773.15.3224.1111.616.188.812.792.31.00.015.08.52.7
25.951.592.257.190.082.913.060.39108.4108.3765.45.3323.0103.516.187.68.8103.63.00.114.78.62.7
27.551.472.437.650.092.573.020.47121.5111.0747.74.6923.2108.016.185.67.8111.80.90.114.48.12.5
29.151.432.337.800.113.022.790.48106.8113.5702.05.1421.5102.516.187.810.8101.20.80.115.29.62.5
30.951.622.577.830.073.162.320.48114.1109.4644.45.6023.0105.716.182.88.1101.01.60.115.59.22.6
32.951.572.597.750.093.122.600.46126.5125.0762.85.4624.8117.816.194.56.4114.01.00.014.78.62.4
34.251.502.417.550.093.063.280.48119.0112.9773.75.2223.3114.316.186.610.1108.71.10.114.67.72.1
basement gneiss:
G12.960.167.250.005.030.370.079.33.7119.90.282.17.515.117.7-0.3269.80.50.010.91.50.7
G25.850.117.360.021.320.850.049.87.494.70.212.12.44.37.3-0.9252.10.20.09.73.80.6
G34.450.127.180.032.641.350.078.22.2156.40.401.83.60.711.0-1.0475.30.20.06.11.50.2
basement amphibolite:
A10.665.277.840.030.287.190.48286.5231.71856.310.2349.377.371.678.6-0.478.80.60.13.90.60.1
A21.413.287.560.080.366.460.78283.3195.51614.910.1840.499.069.794.9-0.8165.80.40.02.11.30.3
A31.822.957.270.030.515.290.47238.0212.01266.97.2631.582.346.593.0-0.5305.00.30.14.50.20.0
A43.751.758.320.120.683.710.42106.178.2623.44.1319.565.159.261.40.5505.10.20.05.40.60.1
A51.586.606.440.030.435.880.33138.31252.21669.88.4041.4264.86.0113.9-0.5284.30.10.23.00.30.2
A61.645.197.190.130.446.320.60245.9330.41596.79.2945.295.947.8111.50.3471.70.20.27.52.00.2
additional Stac Fada sample from different locality:
SF2.362.387.260.071.981.140.4391.7221.3765.54.3931.3382.826.7110.00.7270.20.20.07.44.40.9
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Table S-4 Iron speciation. FeCarb = carbonate-bound iron, FeOx = ferric oxide-bound iron, FeMag = magnetite-bound iron, FePy = pyrite-bound iron. FeHR = highly reactive iron, which is the sum of all four phases. FeT = total iron from Table S-5. FePy was not determined in most of the red shale facies and assumed to be zero as in the few examples. * = Carbonate content was calculated from the concentration of Ca in the acetic acid extract, assuming a CaCO3 stoichiometry. Note that this calculation is an upper estimate, because it does not account for partial dissolution of silicates, which may become important below a carbonate content of 5 %, as suggested by the low molar Ca/Mg ratios in those samples.
position [m]FeCarb [%]FeOx [%]FeMag [%]FePy [%]FeHR [%]FePy/FeHR [by mass]FeHR/FeT [by mass]carb.* [%]molar Ca/Mg
00.090.690.39
1.170.000.220.10.2
0.50.321.110.33
1.750.000.440.40.2
0.750.090.470.26
0.820.000.213.06.4
1.650.130.580.11
0.830.000.244.15.8
2.050.070.600.34
1.020.000.192.37.3
2.730.590.510.21
1.310.000.3611.84.3
2.770.160.320.110.000.600.000.2118.228.3
2.80.100.350.18
0.640.000.110.51.2
2.830.170.470.14
0.780.000.2014.723.2
2.870.170.270.130.000.580.000.1817.428.3
3.20.760.680.38
1.810.000.351.90.7
3.70.290.160.190.000.640.000.141.92.4
4.10.100.530.18
0.810.000.3020.649.0
4.380.110.450.11
0.670.000.2326.964.0
4.420.100.270.090.010.470.030.2231.176.4
4.650.490.170.230.070.950.070.265.32.9
4.750.160.070.101.231.570.780.3710.021.3
4.90.230.080.111.151.580.730.3615.828.0
5.30.130.080.080.270.560.480.1719.346.6
5.450.190.200.221.361.980.690.4419.38.8
5.60.270.560.230.001.060.000.2414.223.4
5.650.790.070.121.112.090.530.4915.217.7
5.80.120.070.080.240.510.460.1511.723.5
6.50.370.160.240.000.770.000.199.85.9
7.10.180.380.17
0.730.000.1812.621.7
12.10.031.550.32
1.890.000.321.53.5
13.050.021.330.24
1.600.000.254.814.0
14.650.020.990.30
1.310.000.235.615.8
16.050.031.140.25
1.420.000.267.314.3
16.850.041.270.26
1.570.000.297.412.3
20.450.020.830.26
1.110.000.206.115.6
22.750.020.980.28
1.280.000.247.817.5
24.550.021.050.33
1.400.000.289.220.0
25.750.020.950.25
1.220.000.236.519.0
25.950.031.000.26
1.290.000.248.224.7
27.550.031.090.28
1.400.000.306.813.9
29.150.031.030.27
1.320.000.266.318.7
30.950.021.180.29
1.490.000.275.214.0
32.950.020.880.26
1.160.000.215.817.6
34.250.010.840.22
1.080.000.217.422.4
42.10.011.790.31
2.110.000.320.20.5
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Table S-5 Molybdenum isotopes of bulk rocks, relative to NIST3134 = +0.25 ‰. Samples with reported standard deviations (SD) were prepared and analysed in replicates.
position [m]δ98/95Mo [‰]SD [‰]
-5.001.24
-4.501.05
0.001.00
1.651.00
2.730.35
2.770.33
2.800.52
2.83-0.310.02
3.200.30
3.700.200.04
4.100.910.04
4.380.47
4.420.30
4.650.570.01
4.750.130.02
4.900.330.09
5.301.100.22
5.450.760.02
5.601.32
5.651.190.01
5.800.680.03
6.500.43
7.100.46
12.10-0.05
13.05-0.170.05
14.65-0.16
16.05-0.340.02
16.85-0.24
20.45-0.34
22.75-0.38
24.55-0.26
25.75-0.32
25.95-0.24
29.15-0.24
30.95-0.360.04
32.95-0.34
34.250.03
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Table S-6 Dissolution method for carbonate bound Sr analysis.
StepReagentVolume [ml]Concentration [M]pH
1-2Ammonium Acetate101-
3-6Acetic Acid7.50.043.07
7-8Acetic Acid80.1752.76
9Acetic Acid60.8752.41
10Acetic Acid61.752.26
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Table S-7 Elemental abundances and Sr isotopes of carbonate leaches. N1-N2 = ammonium acetate washing steps, S1-S8 = acetic acid extractions with increasing acid strength. Concentrations are relative to bulk rock.
sampleMg [ppm]Al [ppm]Ca [%]Mn [ppm]Fe [ppm]Rb [ppb]Sr [ppb]Rb/SrMn/Sr87Sr/86Sr
+4.20 m, N125451.797216044313140.192.30.71553
+4.20 m, N210341.591151523218580.025.30.71272
+4.20 m, S111623.803460185216930.0115.90.71072
+4.20 m, S211824.394101201239390.0117.1n.d.
+4.20 m, S393362.292184127138550.0115.70.71061
+4.20 m, S41081260.6378813578140.029.90.71303
+4.20 m, S51454610.39492314450070.039.90.71562
+4.20 m, S61694410.14213414225140.068.5n.d.
+4.20 m, S72226560.11198510414580.0713.30.72046
+4.20 m, S82196260.12177610213060.0813.30.72028











+4.38 m, N119461.595511645269800.062.10.72807
+4.38 m, N2103141.58932207208780.014.40.71223
+4.38 m, S110523.79225074227820.009.90.70989
+4.38 m, S210443.99238185240110.009.90.70977
+4.38 m, S310253.97239266247440.009.60.70964
+4.38 m, S493332.53172461182760.009.40.71005
+4.38 m, S51001831.10841563102180.018.20.71061
+4.38 m, S61272000.3632205944040.017.30.71258
+4.38 m, S72515070.5146846848640.019.40.71242
+4.38 m, S82053330.3632635431210.0210.20.71223











+4.90 m, N1273171.486523129310460.102.10.71398
+4.90 m, N2124281.351005317286220.013.50.71156
+4.90 m, S111572.912151117250230.008.60.70999
+4.90 m, S2157223.082343192290030.018.10.71004
+4.90 m, S31611400.657810150122660.016.3n.d.
+4.90 m, S41621330.2530129167370.014.5n.d.
+4.90 m, S52113480.2629379161470.014.7n.d.
+4.90 m, S62483290.1418487849100.023.7n.d.
+4.90 m, S72454130.0711885416970.036.70.71635
+4.90 m, S83516590.10151356314510.0410.70.71751











+5.65 m, N1_rep1546151.666425502173010.323.70.72204
+5.65 m, N2_rep1195251.37993566132030.047.50.71338
+5.65 m, S1_rep1180122.962402176184630.0113.00.71000
+5.65 m, S2_rep1215252.882384200189120.0112.60.71000
+5.65 m, S3_rep12441740.811091117662440.0317.50.71258
+5.65 m, S4_rep12641810.36481410528690.0416.60.7162
+5.65 m, S5_rep13376840.32425912024190.0517.20.72024
+5.65 m, S6_rep13044310.111951818240.1022.70.72909
+5.65 m, S7_rep164412750.0923214886940.1333.90.73967
+5.65 m, S8_rep156112000.0819179785640.1433.4











+5.65 m, N1_rep253391.255115407163370.333.10.72299
+5.65 m, N2_rep2226121.28822709138120.055.90.71374
+5.65 m, S1_rep2189122.992201176189440.0111.60.70964
+5.65 m, S2_rep2210143.042302179189290.0112.20.70977
+5.65 m, S3_rep2189791.241325124100000.0113.20.71075
+5.65 m, S4_rep22571710.54691111845310.0315.30.71359
+5.65 m, S5_rep24277730.41585814733350.0417.40.71779
+5.65 m, S6_rep23275400.1524509811560.0821.00.72447
+5.65 m, S7_rep270415120.15312109711040.0928.00.72969
+5.65 m, S8_rep252710570.0919153746150.1231.00.73106
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Table S-8 Strontium isotope results of basement rocks and impact/volcanic debris layer. 87Sr/86Sr ratios at 1.2 Ga were calculated as described in Section S1.7.
IDSr [ppm]Rb [ppm](87Sr/86Sr)measured(87Sr/86Sr)1.2Gatype
A6579.37.90.702940.70227mafic
A2249.89.20.706890.70508mafic
G2242.123.80.720370.71554felsic
G1121.156.00.749910.72717felsic
-5 m198.546.70.718220.70666impact/volcanic
-4.5 m243.540.50.714220.70604impact/volcanic
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