Ullmann, C. V.3; Campbell, H. J.2; Frei, R.3; Korte, C.3
1 Geology, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet2 GNS Science3 Geology, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet
Brachiopod fossils from the sedimentary sequences of the Téremba Terrane (New Caledonia) provide a unique opportunity to study the environmental parameters of the Late Triassic. 87Sr/86Sr ratios, δ13C and δ18O values, and Sr/Ca, Mg/Ca and Mn/Ca ratios were measured on brachiopods from Oretian to Otapirian (Norian to Rhaetian) fossil localities of the Baie de St.-Vincent area. Post-depositional impacts on the geochemical proxies were investigated by analysing calcite cements and partly recrystallized shell material. Diagenetic fluids carried strontium with a low 87Sr/86Sr ratio of c. 0.7065, and light δ13C values of c.-20‰, suggesting major contributions by oxidized organic matter. Diagenetic equilibrium was reached at δ18O values of c.-12‰, very low Sr/Ca ratios of < 0.05 mmol/mol and locally variable Mn/Ca ratios of up to 5.9 mmol/mol. Results from the best-preserved samples suggest that calcification temperatures of Warepan and Otapirian brachiopods from New Caledonia were consistently ≥ 15 °C.
New Zealand Journal of Geology and Geophysics, 2014, Vol 57, Issue 4, p. 420-431
Sr/Sr; Brachiopod; Diagenesis; New Caledonia; Stable isotopes; Trace elements