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Global climate stabilisation by chemical weathering during the Hirnantian glaciation

P.A.E. Pogge von Strandmann1,

1London Geochemistry and Isotope Centre, Institute of Earth and Planetary Sciences, University College London and Birkbeck, University of London, Gower Street, London, WC1E 6BT, UK

A. Desrochers2,

2Department of Earth and Environmental Sciences, University of Ottawa, ON K1N 6N5, Canada

M.J. Murphy3,

3Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK

A.J. Finlay4,5,

4Chemostrat Ltd, Welshpool, SY21 8SL, UK
5School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth, PO1 2UP, UK

D. Selby6,

6Department of Earth Sciences, University of Durham, Durham, DH1 3LE, UK

T.M. Lenton7

7College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4QE, UK

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Pogge von Strandmann, P.A.E., Desrochers, A., Murphy, M.J., Finlay, A.J., Selby, D., Lenton, T.M. (2017) Global climate stabilisation by chemical weathering during the Hirnantian glaciation. Geochem. Persp. Let. 3, 230–237.

NERC advanced research fellowship NE/I020571/2 and ERC Consolidator grant 682760 - CONTROLPASTCO2.

Geochemical Perspectives Letters v3, n2  |  doi: 10.7185/geochemlet.1726
Received 24 November 2016  |  Accepted 15 May 2017  |  Published 15 June 2017




Figure 1 Carbonate (Pointe Laframboise and Ellis Bay West) and shale (Dob’s Linn) Li isotope ratios. Open squares are separately analysed brachiopods. Carbon and osmium (initial 187Os/188Os) isotope data are from the same samples (Finlay et al., 2010

Finlay, A.J., Selby, D., Grocke, D.R. (2010) Tracking the Hirnantian glaciation using Os isotopes. Earth and Planetary Science Letters 293, 339–348.

). Biostratigraphic correlation is based on the N. persculptus Zone (Melchin et al., 2013

Melchin, M.J., Mitchell, C.E., Holmden, C., Storch, P. (2013) Environmental changes in the Late Ordovician-early Silurian: Review and new insights from black shales and nitrogen isotopes. Geological Society of America Bulletin 125, 1635–1670.

).
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Figure 2 Comparison of data and model results. Sea level timing is from stratigraphic data (Ghienne et al., 2014

Ghienne, J.-F., Desrochers, A., Vandenbroucke, T.R.A., Achab, A., Asselin, E., Dabard, M.-P., Farley, C., Loi, A., Paris, F., Wickson, S., Veizer, J. (2014) A Cenozoic-style scenario for the end-Ordovician glaciation. Nature Communications 5, doi: 10.1038/ncomms5485.

). Seawater Li isotope data were generated from carbonate data by adding a 4 ‰ fractionation factor (Marriott et al., 2004

Marriott, C.S., Henderson, G.M., Crompton, R., Staubwasser, M., Shaw, S. (2004) Effect of mineralogy, salinity, and temperature on Li/Ca and Li isotope composition of calcium carbonate. Chemical Geology 212, 5–15.

). The model shows the changes in riverine and hydrothermal Li fluxes, the pCO2 levels and temperature anomalies caused by these changes, and the resulting oceanic δ7Li curve. The red model lines are for scenarios where riverine δ7Li = 3 ‰, 0 ‰, a change from 0 to 10 ‰ during the glaciation and “shale-constrained” (s.c.), using Dob’s Linn δ7Li data to constrain river values (see text and Supplementary Information for detail).
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Supplementary Figures and Tables


Figure S-1 Sample location maps. (a) Palaeogeographic location map, with sample locations highlighted (adapted from Finlay et al., 2010); (b) Current geography of sample locations from Scotland and Anticosti Island; (c) Detail of sample locations on Anticosti Island; (d) Detail of sample location of Dob’s Linn.
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Table S-1 Li isotope and trace element data from the section studies here.

Heightδ7Li 2 sdLi/CaMg/CaAl/CaMn/CaSr/Ca

m

µmol/molmmol/molmmol/molmmol/molmmol/mol
Point Laframboise
L-M-54180.810.80.111.134.60.22.12.3
L-M-56184.48.00.717.546.50.52.71.0
L-M-5818810.10.218.543.20.42.72.8
L-M-60189.811.80.746.361.60.23.61.2
L-M-61190.711.90.430.541.60.63.41.2
L-M-64193.314.20.111.827.80.22.30.9
L-M-66195.113.80.112.426.30.35.31.2
L-M-6719618.70.533.6413.70.68.91.2
PL-5i19817.60.723.2297.80.48.51.3
L-M-6919915.60.113.196.90.23.11.0
PL-8i20014.90.710.2376.30.27.41.1
PL-13i201.812.40.117.947.50.32.31.4
PL-17Bi203.88.40.212.131.80.23.50.7
PL-18i204.110.20.65.063.40.13.01.1
PL-19Ai204.311.40.220.715.60.21.20.6
PL-22i205.38.70.19.030.10.13.70.9
PL-27i207.513.00.311.724.70.31.81.2
Large fossils

194.512.11.110.231.20.12.11.2

19818.20.420.542.80.22.61.4

19817.60.623.224.30.23.11.3

20016.10.420.728.90.14.41.0

20016.20.321.441.60.13.40.9

200.414.20.315.138.00.12.91.0
Ellis Bay West
E-M-1011.20.644.088.20.24.21.3
E-M-318.80.925.054.60.53.51.0
E-M-41.511.20.620.682.90.10.81.2
E-M-7310.40.133.1113.10.40.91.6
E-M-9410.80.620.963.40.00.71.0
E-M-11512.30.614.743.60.00.60.8
E-M-167.518.50.726.1237.20.41.21.3
E-M-188.519.61.013.5318.10.26.71.0
E-M-19914.80.611.757.60.13.01.3
E-M-219.813.50.75.012.30.40.30.7
E-M-251114.30.238.0155.60.33.71.1
E-M-3112.810.20.58.523.50.50.71.0
E-M-3516.515.70.410.426.30.01.11.2
E-M-3920.511.80.89.529.20.40.21.2
E-M-4627.515.21.011.326.40.30.21.3
Dob's Linn
AF20-070.9-0.71.1




DS2-04-0.03-0.20.9




AF07-07-1.1-3.10.8




AF32-07-1.6-1.00.4




AF23-07-1.72.00.7




AF24-07-2.22.30.3




AF26-07-2.75.60.3




AF27-07-3.15.30.4




AF11-07-3.695.30.9




AF12-07-4.380.20.2




AF29-07-50.60.3




AF15-07-5.88-3.61.3




AF30-07-5.9-1.60.4




AF31-07-7.1-1.31.4




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Figure S-2 Lack of correlation between δ7Li and grain size tracer Si/Al, and provenance tracers Li/Al and Os (Osi = 187Os/188Os) isotopes.
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Figure S-3 Lack of significant correlation between shale δ7Li and secondary mineralogy.
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Figure S-4 Example of isotope fractionation behaviour of two linked phases (in this case water and clay) for a constant fractionation factor. Solid lines represent equilibrium fractionation, while dotted lines represent Rayleigh fractionation.
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Table S-2 XRF major element concentration data (in wt. %) for the shales.

Al2O3SiO2TiO2Fe2O3MnOMgOCaONa2OK2OP2O5
AF-32-0719.4466.010.787.270.713.370.220.783.300.14
AF-27-0710.8443.130.536.021.076.078.160.352.040.08
AF-12-0714.8756.440.852.780.011.380.290.284.140.03
AF-07-0714.5254.850.806.160.112.630.220.413.030.11
DS2-0417.1260.330.668.460.023.250.002.773.030.05
AF-30-0713.7650.980.686.560.042.690.190.662.860.06
AF-04-0714.4753.620.674.910.022.340.101.013.170.04
AF-24-0713.7450.380.674.910.544.575.380.342.850.16
AF-31-0719.7961.790.847.950.103.930.310.813.530.06
AF-11-0715.2753.750.782.700.021.510.340.303.970.04
AF-26-0712.3046.450.635.010.564.215.180.252.600.10
AF-29-0719.1367.470.766.130.043.620.250.973.390.07
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Table S-3 Quantitative mineralogy data from some of the shale samples.
Siroquant Quantitative AnalysisAF0406DS104AF0807AF23A07AF26A07AF27A07
(wt. %)
Anhydrite------
Ankerite---61730
Calcite---331
Chlorite-1271087
Dolomite1-----
Gypsum------
Illite/Muscovite364132352921
Kaolinite932-32
K-Feldspar3-----
Plagioclase17121088
Pyrite752--1
Quartz433245363230
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Table S-4 Results of sequential leaching of some of the Dob’s Linn shales.

δ7Li 2 sd% of bulk Li
AF23-07
Exchangeable13.10.61.5
Carbonate8.60.33.5
Residue2.70.295
Bulk2.00.7
AF11-07
Exchangeable15.60.60.8
Carbonate14.31.02.2
Residue4.70.197
Bulk5.30.9
AF15-07
Exchangeable1.50.52
Carbonate-3.00.54
Residue-2.50.494
Bulk-3.61.3
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Figure S-5 Anticosti section lithology (Desrochers et al., 2010; Achab et al., 2011, 2013; Copper et al., 2013), compared to isotope data.
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Table S-5 Definitions of parameters used in the models.
SymbolParameter
AOcean-atmosphere reservoir of DIC/CO2 (mol)
A0Modern reservoir (mol)
FdDegassing flux of CO2 input (mol)
FwSilicate weathering flux of CO2 consumption (mol)
DNormalised degassing parameter
UNormalised uplift parameter
kVFraction of present weathering rate in the absence of plants
∆TTemperature change (K)

Lithium
FrRiverine Li flux
FhHydrothermal Li flux
FsedRemoval of Li into ocean secondary sediments
RIsotope ratio
NOcean reservoir of Li (mol)
kLiPartition coefficient of oceanic Li sink
khModern hydrothermal Li input (mol)
kwModern riverine Li input (mol)
sinkLi isotopic fractionation factor imposed by the Li sink
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Figure S-6 Result of a permanent decrease in degassing on the Li isotope composition of the oceans. Note that this scenario assumes Rr = 3 ‰.
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Figure S-7 Result of a permanent increase in vegetation cover on the Li isotope composition of the oceans. Note that this scenario assumes Rr = 3 ‰.
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Figure S-8 Result of a permanent increase in vegetation cover combined with an increase in riverine δ7Li on the Li isotope composition of the oceans.
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Figure S-9 Identical scenario to Figure S-8 (increase in vegetation cover combined with an increase in riverine δ7Li), but combined with a subsequent decrease in kv and Rr.
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Figure S-10 A scenario where the seawater δ7Li excursion is solely caused by a change in river δ7Li (Rr) (but there is no associated change in the modelled carbon cycle and global temperature).
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Figure S-11 Effect of an oscillatory system from the feedbacks described in the text on the relative temperature and seawater δ7Li values.
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Figure S-12 Effect of single glaciation on the relative temperature and seawater δ7Li values.
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Figure S-13 The same scenario as in Figure S-12, but with an added temperature control on the fractionation factor of the Li sink.
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Figure S-14 The same scenario as in Figure S-13, except that riverine δ7Li also increases.
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Figure S-15 Modelled Sr isotope ratio of seawater, using factors taken from the Li-C model.
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