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We present high precision (TIMS double spike) stable isotope measurements of both δ44/40Ca and δ88/86Sr together with radiogenic 87Sr/86Sr ratios determined from conodont apatite. These data represent five intervals ranging from the early Ordovician to late Triassic. The conodont δ44/40Ca values (relative to NIST 915a) range from − 0.47‰ to + 0.15‰, with an apparent shift to more positive values between the early Silurian and late Devonian/early Carboniferous, similar to the brachiopod-based marine δ44/40Ca record (Farkaš et al., 2007a). We calculated a δ44/40Ca seawater-bio-apatite fractionation factor of about − 1.9‰, which allowed us to reconstruct a palaeo-seawater δ44/40Ca record from bio-apatites. Despite a slightly positive offset of about + 0.2 to + 0.5‰, the δ44/40Ca record obtained from bio-apatites is consistent with the previously reported δ44/40Ca seawater record inferred from carbonates. We find that unlike the carbonate δ44/40Ca records, the δ88/86Sr measurements from conodont apatite show unexpectedly large variations (up to ~ 1‰), with ratios ranging from − 0.6‰ to 0.3‰. These reconnaissance data reveal a reasonable correlation between δ88/86Sr and radiogenic 87Sr/86Sr* (r2 = 0.60, n = 13, p = 0.002), suggesting that the controls from differential weathering regimes and/or continental crustal compositions buffered ancient seawater compositions.
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- 3 Finished
McCulloch, M., Cawood, P., Lynch, M., Wasson, R., Lavery, P., Waite, A., Lowe, R., Kilburn, M., Trotter, J., Clode, P., Falter, J., McNaughton, N., Wyrwoll, K., Collins, L., Loneragan, N. & McInnes, B.
1/01/10 → 31/12/10
Trotter, J., Williams, I., Barnes, C., Beerling, D. & Wellman, C.
1/01/10 → 31/12/12