Conodont apatite δ88/86Sr and δ44/40Ca compositions and implications for the evolution of Palaeozoic to early Mesozoic seawater

Sandrine Le Houedec, Malcolm McCulloch, Julie Trotter, Kai Rankenburg

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5 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)55-65
Number of pages11
JournalChemical Geology
Volume453
Early online date14 Feb 2017
DOIs
Publication statusPublished - 20 Mar 2017

Fingerprint

Apatites
conodont
Seawater
apatite
Paleozoic
seawater
Chemical analysis
Carbonates
carbonate
Weathering
Fractionation
brachiopod
Isotopes
Silurian
Ordovician
stable isotope
Triassic
weathering
fractionation

Cite this

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title = "Conodont apatite δ88/86Sr and δ44/40Ca compositions and implications for the evolution of Palaeozoic to early Mesozoic seawater",
abstract = "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.",
author = "{Le Houedec}, Sandrine and Malcolm McCulloch and Julie Trotter and Kai Rankenburg",
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Conodont apatite δ88/86Sr and δ44/40Ca compositions and implications for the evolution of Palaeozoic to early Mesozoic seawater. / Le Houedec, Sandrine; McCulloch, Malcolm; Trotter, Julie; Rankenburg, Kai.

In: Chemical Geology, Vol. 453, 20.03.2017, p. 55-65.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Conodont apatite δ88/86Sr and δ44/40Ca compositions and implications for the evolution of Palaeozoic to early Mesozoic seawater

AU - Le Houedec, Sandrine

AU - McCulloch, Malcolm

AU - Trotter, Julie

AU - Rankenburg, Kai

PY - 2017/3/20

Y1 - 2017/3/20

N2 - 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.

AB - 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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U2 - 10.1016/j.chemgeo.2017.02.013

DO - 10.1016/j.chemgeo.2017.02.013

M3 - Article

VL - 453

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JF - Chemical Geology

SN - 0009-2541

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