Abstract
Conodont microfossils record seawater strontium isotope values ( (super 87) Sr/ (super 86) Sr), permitting chemostratigraphic correlation for tectonic and climatic reconstructions of the Paleozoic and early Mesozoic (541-201 Ma). Advances in laser ablation multiple collection inductively coupled plasma mass spectrometry (LA MC-ICP-MS) enable rapid, high resolution (super 87) Sr/ (super 86) Sr analyses of conodont bioapatite, but require validation by comparison with solution analysis. We compare solution and LA MC-ICP-MS (super 87) Sr/ (super 86) Sr analyses of Carboniferous-age conodonts. The two analytical methods generally agree for conodonts from the same stratigraphic level. In addition, we find that individual conodonts from the same stratigraphic level exhibit (super 87) Sr/ (super 86) Sr variability beyond the precision of reference materials. This finding suggests that solution (super 87) Sr/ (super 86) Sr values determined by dissolving multiple conodonts are homogenizing distinct (super 87) Sr/ (super 86) Sr signatures of individual conodonts. As such, the precision of these solution measurements does not capture the geologic variability of conodont (super 87) Sr/ (super 86) Sr within a stratigraphic level. We explore possible reasons for this geologic variability including time averaging, spatial variability in in seawater (super 87) Sr/ (super 86) Sr, and differential diagenesis. We further calculate what fraction of the geologic variability in conodont strontium isotope values contributes to the uncertainty in age estimations based on correlations to the seawater strontium isotope curve. Conodont (super 87) Sr/ (super 86) Sr measurements that do not account for geologic variability are at risk of false calibrations with the paleo-seawater (super 87) Sr/ (super 86) Sr curve, which has implications for the timing of geologic events and reconstructions of paleo-environmental changes.