Canadian Journal of Earth Sciences Strontium isotope geochemistry of modern and ancient archives: tracer of secular change in ocean chemistry Journal: Canadian Journal of Earth Sciences Manuscript ID cjes-2018-0085.R1 Manuscript Type: Article Date Submitted by the 09-Aug-2018 Author: Complete List of Authors: Zaky, Amir; Brock University Brand, Uwe; Department of Earth Sciences Buhl, Dieter; Ruhr-Universitat Bochum Blamey, Nigel; University of Western Ontario Bitner, Aleksandra;Draft Polish Academy of Sciences Logan, Alan; University of New Brunswick Gaspard, Daniele; Sorbonne Université Popov, Alexander; Far East Branch of the Russian Academy of Sciences, Far East Geological Institute Sr isotopes, modern and ancient brachiopods, halite, whole rock, Keyword: seawater-87Sr curve Is the invited manuscript for Advances in low temperature geochemistry diagenesis seawater and consideration in a Special climate: A tribute to Jan Veizer Issue? : https://mc06.manuscriptcentral.com/cjes-pubs Page 1 of 81 Canadian Journal of Earth Sciences 1 Strontium isotope geochemistry of modern and ancient archives: 2 tracer of secular change in ocean chemistry 3 4 5 6 7 8 Amir H. Zaky a, Uwe Brand a*, Dieter Buhl b, Nigel Blamey c, M. Aleksandra Bitner d, 9 Alan Logan e, Daniele Gaspard f , Alexander Popovg 10 11 12 13 14 15 16 17 a Department of Earth Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, 18 Ontario L2S 3A1, Canada 19 20 b Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität, D-44801 Bochum, 21 Germany. Draft 22 23 c Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, 24 Canada 25 26 d Institute of Paleobiology, Polish Academy of Sciences, ul. Twarda 51/55, 00-818 Warszawa, 27 Poland 28 29 e Centre for Coastal Studies, University of New Brunswick, Saint John, New Brunswick E2L 4 30 L5, Canada 31 32 f Muséum National d’Histoire Naturelle, Centre de Recherche sur la Paléobiodiversité & les 33 Paléoenvironnments (CR2P), Sorbonne Université, F-75005 Paris, France 34 35 g Far East Geological University, Far East Branch of the Russian Academy of Sciences, pr. 100 36 let Vladivistoku, Vladivostok, 690022, Russia 37 38 39 40 41 42 43 * Corresponding author e-mail: [email protected] 44 45 https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 2 of 81 46 Keywords 47 87Sr/86Sr, modern and ancient brachiopods, halite, whole rock, secular-87Sr seawater curve, 48 Phanerozoic, Precambrian 49 50 Research highlights 51 Sr isotope compositions of modern brachiopods and evaporites 52 No species-dependent effect and biological fractionation 53 Latitude and depth have no impact on the 87Sr/86Sr in modern brachiopods 54 Salinity and temperature have minor impacts on the 87Sr/86Sr in modern brachiopods 55 Intensive screening for diagenetic impact on fossil archives 56 High-resolution Phanerozoic and late PrecambrianDraft seawater-87Sr curves 57 58 59 60 61 62 63 64 65 66 67 68 https://mc06.manuscriptcentral.com/cjes-pubs Page 3 of 81 Canadian Journal of Earth Sciences 69 Abstract 70 Strontium isotopes of marine archives provide a significant means for tracing physical and 71 chemical processes operating over geologic time. Modern articulated brachiopods and halite 72 samples were collected from all depths of the world’s main water bodies. Material from the Arctic, 73 North and South Atlantic, North and South Pacific, Indian and Southern Oceans as well as 74 Caribbean and Mediterranean Seas provide baseline parameters for diagenetic screening and 75 reconstruction of seawater curves. 76 The strontium isotopic ratio of modern brachiopods is unobscured by latitude, depth and 77 biologic factors (Order, valves, and shell segment). However, there is a small but significant 78 impact of external sources reflected by salinity and temperature on the strontium isotope ratio of 79 modern brachiopods. We found a significantDraft difference in 87Sr/86Sr of brachiopods from polar and 80 temperate-tropical habitats (p = 0.001), which should be considered when working with deep-time 81 archives. The average 87Sr/86Sr value of all our modern shells (0.709160 ±0.000019; N = 95) and 82 halite (0.709153) is similar to values measured for modern seawater (0.710167 ±0.000009; p = 83 0.118). The radiogenic strontium content of present-day seawater does not vary significantly, and 84 modern biogenic-calcite 87Sr/86Sr ranges from 0.709126 to 0.709233 with a fluctuation of about ± 85 0.000054. 86 With the most rigorous diagenetic evaluations and stratigraphic assignment of deep-time 87 samples, and applying the strontium isotope fluctuation recorded by modern biogenic calcite to 88 ancient carbonates and a 1 Myr interval, reconstructions resulted in a seawater-87Sr curve with 89 greater details during the Phanerozoic and Neoproterozoic. 90 91 1. Introduction https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 4 of 81 92 The interplay between Earth’s continental and oceanic activities and climate processes 93 controls the strontium isotopic composition of modern seawater, whereas their evolution through 94 time changed the marine Sr isotope ratio (87Sr/86Sr) significantly with geologic history (e.g., 95 Burke et al., 1982; Elderfield, 1986; Veizer, 1989). Defining these changes is of great 96 importance not only for correlating marine sediments on regional and global scales, but also for 97 understanding the processes of the past and their impacts on ecosystems, habitats, biological 98 diversity and geochemical cycles (e.g., Palmer and Edmond, 1989; Capo and DePaolo, 1990; 99 Hodell et al., 1990; Derry et al., 1994; Martin and Macdougall, 1995; Montañez et al., 1996; 100 Denison et al., 1998; McArthur et al., 1998, 2012). 101 The main carriers of Sr into the oceans are fluvial discharge and hydrothermal flux, and 102 perhaps coastal groundwater discharge.Draft Their Sr isotope loads reflect the intensity of weathering 103 processes, type of rocks subject to erosion and rate of sea floor spreading (Capo and DePaolo, 104 1990; Berner,1991; Raymo and Ruddiman, 1992; Palmer and Edmond, 1992; Basu et al., 2001; 105 Krabbenhöft et al., 2010). Although strontium is dissolved at high concentration in modern 106 seawater (~7.8 ppm), it is unable to precipitate its own minerals because of its high atomic mass 107 (Capo et al., 1998). Instead it is incorporated into the crystal lattice of chemical and biochemical 108 marine precipitates (e.g., Veizer, 1983; Farrell et al., 1995). Furthermore, rubidium is a low- 109 abundance element with large ionic radius (1.48Å) compared to that of calcium (0.99Å) that is 110 unlikely to substitute for Ca+2 in carbonate minerals, and no significant addition of 87Sr from 87Rb 111 decay happens after precipitation of carbonate archives (Veizer, 1983; Capo et al., 1998). 112 Assessing the 87Sr/86Sr variations in paleo-oceans and its evolution through time requires 113 measuring the Sr composition of pristine marine archives that inherit a marine signature with 114 minimal isotope fractionation and extraneous outside influences. This precondition has been https://mc06.manuscriptcentral.com/cjes-pubs Page 5 of 81 Canadian Journal of Earth Sciences 115 subject to intensive work aimed at evaluating the diagenetic state of ancient marine archives and 116 thus their preservation. This study evaluates the Sr isotope composition of modern brachiopods 117 and halite of the world’s main water masses (Arctic, North and South Atlantic, North and South 118 Pacific, Indian and Southern Oceans as well as Caribbean and Mediterranean Seas), they are 119 either quite resistant or readily dissolve during diagenetic processes (e.g., Brand and Veizer, 120 1980; Schreiber and El Tabakh, 2000). Although resistant to alteration, brachiopods as archives 121 for trace elements, stable isotopes have limitations that must be considered when analysing 122 modern and ancient counterparts. For example, their primary layer incorporates stable isotopes in 123 disequilibrium with ambient seawater, a similar observation has been made about their umbonal 124 area (e.g., Carpenter and Lohman, 1995; Brand et al., 2003; 2015). Trace elemental contents, 125 especially Mg and Sr show variation in Drafttheir valves with growth stage, and the optimal area for 126 geochemical investigation is the internal mid-section of both ventral and dorsal valves for 127 modern and ancient brachiopods (Romanin et al., 2018). This gives us an opportunity to test the 128 concept that the standard normalization procedure for 87Sr/86Sr removes any natural fractionation 129 within marine archives (cf. McArthur et al., 2012). Since this remains unsubstantiated for may 130 biogenic carbonates, it gives us an opportunity to test this on our database of modern 131 brachiopods covering the world’s oceans, and various biological parameters, oceanographic and 132 environmental conditions. Furthermore, we aim to apply our findings for modern archives to 133 ancient ones, and supplemented them by detailed diagenetic evaluations of select brachiopods, 134 conodonts and whole rock to improve on the Sr isotope curves reconstructed for Phanerozoic and 135 Neoproterozoic seawater. 136 The strontium isotope composition of whole rock presents a special problem, 1) the 137 Precambrian is dominated by this material for analysis, which in turn 2) may be subject to https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 6 of 81 138 aluminosilicate contamination and diagenetic alteration. These two issues tend to make the Sr 139 isotope compositions more radiogenic (e.g., Shields and Veizer, 2002), although in special 140 circumstances may make them less radiogenic (cf. Brand et al., 2010). The degree of diagenetic 141 alteration can be assessed by rigorous screening of other proxies and petrographic means (i.e. 142 cathodolumninescence), but contamination remains an on-going concern because of the bulk 143 digestion method and selecting limited amounts of acid or strengths may not be sufficient to 144 obviate this concern.