Oxygen isotope variability in conodonts: implications for reconstructing Palaeozoic palaeoclimates and palaeoceanography

Conodonts have the potential to elucidate the intricacies of Palaeozoic climates, especially if δ 18O values of single apatitic tooth-like 'elements' can be used to map evolving sea surface temperatures and differentiate oceanic water masses. Their ecological distribution as pelagic and nektobenthic organisms, high-resolution biostratigraphy, and abundance in Cambrian-Triassic rocks qualifies them as potentially robust climate archives. Previous ion microprobe conodont δ 18O studies have proceeded directly to palaeotempera-ture interpretation without appreciation of inter- and intra-element variability or post-mortem artefacts. Here, ion microprobe analyses of Ordovician and Silurian conodonts establishes that: intra-element crown tissue δ 18O typically varies by <1%o (53% of conodonts analysed), is normally