Supplementary Information

Development of a protocol to obtain the composition of terrigenous detritus in marine sediments -a pilot study from

International Ocean Discovery Program Expedition 361

Margit H. Simon1,2,3*, Daniel P. Babin3,4, Steven L. Goldstein3,4, Merry Yue Cai3, Tanzhuo Liu3, Xibin  Han5, Anne A. Haws6, Matthew Johns3,4, Caroline Lear7 and Sidney R. Hemming3,4

1 NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway2 SFF Centre for Early Sapiens Behaviour (SapienCE), University of Bergen, Post Box 7805, 5020, Bergen, Norway.3 Lamont-Doherty Earth Observatory of Columbia University, 61 Rt 9W, Palisades, New York 10964-8000, USA4 Department of Earth and Environmental Sciences, Columbia University, New York NY USA5Key Laboratory of Submarine Geosciences, State Oceanic Administration & Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, P. R. China6 Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA7 School of Earth and Ocean Sciences, Cardiff University, UK

*Corresponding author

1. Clay mineralogy on washed fraction

1.1. Background

With an equivalent spherical diameter of <2um, clay particles are produced through various geochemical processes [Bergaya and Lagaly, 2013]. In marine sediments, clay minerals may have different origins. Clays transported in water masses or authigenic clay can represent an important part of detritic marine sediments depending on the sedimentary context of the studied site. However, when marine sediment cores are located close to the mouth of a river, an area with a high terrigenous sedimentation rate, clay size minerals are mainly terrigenous clays that originate from the adjacent continent [Michalopoulos and Aller, 1995].

Terrigenous clay characteristics have been demonstrated as being good indicators of environmental changes and pathways of suspended sediments [Chamley, 1989; Bayon et al., 2015]. The species and proportions of individual clay minerals in soils and sediments depend mainly on the nature of the source rocks and on the climatic conditions [Biscaye, 1965; Griffin et al., 1968; Windom, 1976; Petschick et al., 1996]. Clay minerals can also be used to interpret the weathering processes [Galán, 2006]. In continental environments, mica (or illite)

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and chlorite are normally inherited from ancient rocks, modified by physical or moderate chemical weathering, whereas kaolinite forms through long-term weathering processes. Smectites are usually weathering by-products derived from the alteration of other silicates, or may also be authigenic [Singer, 1984; Chamley, 1989; Hillier, 1995]. Thus, the clay mineral ratio between transformed clays (smectite + kaolinite) and detrital clays (mica + chlorite) is a good indicator of the prevalent type of weathering (chemical or physical) that affected the parent rocks or soils. Consequently, the composition of the terrigenous clay mineral recorded in marine sediments may reflect both the geological history of the source areas as well as the type and intensities of the weathering processes occurring in the watershed.

1.2 Results and interpretation

The results show that the content of smectite and illite appears to differ significantly in the samples that have undergone a CsCl wash (SF. 1, Supplementary Table). In the aliquots treated with the 0.1N CsCl solution the apparent concentration of smectite decreased from 30% in the unwashed aliquot to 10%. Conversely, the apparent concentration of illite increased from 40% to 60%. We do not think that this suggest an actual change in the mineralogy of the samples rather that this could be caused by a more random orientation of the flocculated clay minerals in the washed group, but more investigation is required. We therefore recommend XRD studies should be conducted before applying the cation exchange wash.

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Supplementary Figure 1: Clay mineral content (%) down core of the 8 test samples from U1478 without CsCl treatment in solid line and dashed with CsCl treatment.

One potential explanation for the apparent loss of smectite and gain of illite might be the fact that the Cs+ solution changed the way the clay minerals flocculate and thus impact their orientations upon settling, which in turn impacts XRD results.

Studies have shown that different sample preparation procedures can alter the relative intensities in XRD powder patterns. If samples are prepared inadequately the measured results can deviate from their ideal values and are no longer only a function of structure, crystal chemistry, and concentration of the phases and instrumental parameters, but also depend on particle statistics, particle size, and preferred orientation [Kleeberg et al., 2008]. It would seem that having randomly orientated clay minerals, due to the rapid flocculation and settling in the salty solution, would provide a more reliable state to quantify clay mineralogy. However, the accuracy of this estimate would depend on standards being prepared in the same manner. In this study, standards were not measured. To avoid the problems observed here, that is, the change in the apparent concentration of clay minerals in the sample and the lack of an expected correlation with CEC, we suggest separating an aliquot for XRD clay mineralogy

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analysis prior to the CsCl wash. Additionally, this would be consistent with the standard approach to XRD clay mineral analysis.

Alternatively, it could be that the cation exchange with CsCl greatly modified the interlayer structure of the smectite (kaolinite is apparently not affected), causing a decrease of the area of the smectite 001 peak, and thus a systematically lower smectite content, compared to the illite fraction. A follow up study in which XRD patterns (EG state) of the untreated and washed samples are provided could to confirm/exclude such a potential effect. With respect to the quantification of the clay mineral contents a combination of XRD techniques conducted on powdered (not oriented) and randomly oriented preparations, in combination with a standard Rietveld approach (whole pattern fitting, instead of the 00l peak approach to account for orientation effects) would be beneficial.

2. CEC and clay mineralogy

The extent of weathering of a soil can be estimated from its CEC, as the availability of exchangeable cations depends on clay mineralogy, which is a function of the substrate composition and degree of chemical weathering. Of soil components, clay minerals and organic matter contribute most significantly to bulk cation exchange capacity. A soil with low CEC would likely have high primary mineral content, or a large proportion of weathering resistant minerals, such as quartz. Clay minerals often have negatively charged surfaces, due to unsatisfied valences at the edges of structural units or due to the substitution of aluminium or silicon atoms by elements with lower charge (e.g. Al3+ replaced by Mg2+), [Carroll, 1959]. As a result, clay can absorb

cations at 10-100 times the concentration primary minerals can. Our measurements on CEC provide a qualitative assessment of a sample’s clay mineralogy. Samples enriched in Al and K relative to Na, Ca, and Mg, tend to have lower cation exchange capacities, consistent with an interpretation of increasing

Supplementary Figure 2: Assessment of the correlations of cation exchange capacity (CEC) and a ratio of the major elements designed to sense variation in clay mineralogy by Vogt (1928). Samples with higher proportions kaolinite and illite relative to smectite and primary minerals should have higher ratios. Here, we observe samples predicted to have more kaolinite and illite by this major element ratio indeed have lower cation exchange capacity.

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kaolinite and illite concentration relative to smectite. CEC seems to be largely controlled by the abundance of smectite vs kaolinite.

The measurements of CEC on clay minerals reliably relates to the sample’s

mineralogy. A ratio of major elements (V=K 2O+Al2O3

Na2O+CaO+MgO¿designed by Vogt

[1927] indicates clay mineralogy and extent of chemical weathering by setting elements highly concentrated in products of higher chemical weathering (kaolinite, illite) to the numerator and those elements associated with less weathered clay minerals (smectite) in the denominator. Plotting this ratio against measurements of CEC yields a negative relationship, with lower CEC related to compositions associated with greater degrees of chemical weathering (R2=0.60), (SF. 2). The proportion of smectite to kaolinite in the unwashed samples seems to dominate the control on the CEC of that sample (SF.3). CEC relates to the clay mineralogy of the unwashed samples in a predictable way (SF.3). Samples with lower CEC in general have more kaolinite and illite. Samples with higher CEC have more smectite.). Comparing the clay mineralogy of the washed samples to the samples’ CEC does not yield a correlation (not depicted).

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Supplementary Figure: 3 Regression of CEC vs clay mineral abundances in the unwashed data set indicates CEC of clay minerals qualitatively predicts constituent clay minerals. In the samples analyzed, it is evident that much of the CEC variation explained by mixing of endmembers kaolinite (CEC=3-10 meq/100g) and smectite (80-120 meq/100g), though an effect of illite (15-25 meq/100g) is detectable. Comparison of the clay mineralogy of the washed data set with the CEC yields weak relationships (not pictured).

Supplementary References

Bayon, G., et al. (2015), Rare earth elements and neodymium isotopes in world river sediments revisited, Geochimica et Cosmochimica Acta, 170, 17-38. doi: 10.1016/j.gca.2015.08.001Bergaya, F., and G. Lagaly (2013), Chapter 1 - General Introduction: Clays, Clay Minerals, and Clay Science, in Developments in Clay Science, edited by F. Bergaya and G. Lagaly, pp. 1-19, Elsevier.Biscaye, P. E. (1965), Mineralogy and Sedimentation of Recent Deep-Sea Clay in the Atlantic Ocean and Adjacent Seas and Oceans, GSA Bulletin, 76(7), 803-832. doi: 10.1130/0016-7606(1965)76[803:MASORD]2.0.CO;2Carroll, D. (1959), Ion exchange in clays ans other minerals, GSA Bulletin, 70(6), 749-779. doi: 10.1130/0016-7606(1959)70[749:IEICAO]2.0.CO;2Chamley, H. (1989), Terrigenous Supply in the Ocean, in Clay Sedimentology, edited, pp. 163-192, Springer Berlin Heidelberg, Berlin, Heidelberg.Galán, E. (2006), Chapter 14 Genesis of Clay Minerals.

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Griffin, J. J., H. Windom, and E. D. Goldberg (1968), The distribution of clay minerals in the World Ocean, Deep Sea Research and Oceanographic Abstracts, 15(4), 433-459. doi: 10.1016/0011-7471(68)90051-XHillier, S. (1995), Erosion, Sedimentation and Sedimentary Origin of Clays, in Origin and Mineralogy of Clays: Clays and the Environment, edited by B. Velde, pp. 162-219, Springer Berlin Heidelberg, Berlin, Heidelberg.Kleeberg, R., T. Monecke, and S. Hillier (2008), Preferred orientation of mineral grains in sample mounts for quantitative XRD measurements: How random are powder samples?, Clays and Clay Minerals, 56(4), 404-415. doi: 10.1346/CCMN.2008.0560402Michalopoulos, P., and R. C. Aller (1995), Rapid Clay Mineral Formation in Amazon Delta Sediments: Reverse Weathering and Oceanic Elemental Cycles, Science, 270(5236), 614-617. doi: 10.1126/science.270.5236.614Petschick, R., G. Kuhn, and F. Gingele (1996), Clay mineral distribution in surface sediments of the South Atlantic: sources, transport, and relation to oceanography, Marine Geology, 130(3), 203-229. doi: 10.1016/0025-3227(95)00148-4Singer, A. (1984), The paleoclimatic interpretation of clay minerals in sediments — a review, Earth-Science Reviews, 21(4), 251-293. doi: 10.1016/0012-8252(84)90055-2Vogt, T. (1927), Sulitjelmafeltets geologi og petrografi, Norges Geologiske Undersokelse, 121, 1-560. Windom, H. L. (1976), Lithogenous material in marine sediments Chemical Oceanography, 103-136.

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