CHEMICAL ANALYSIS OF CONODONT PLATFORM ELEMENTS AND THE IMPLICATIONS FOR CONODONT PHYLOGENY AND STRONTIUM ISOTOPE STRATIGRAPHY

The general composition of conodont elements has been well documented for several decades, with a rough composition approaching that of francolite. Chemical variations in conodont elements are increasingly being used for both chronostratigraphic correlation as well as biologic affinity determination. In recent years, the strontium isotopic composition of these elements has been used for chronostratigraphic purposes while the overall similarities in composition to enamel have at times been used to place conodonts within the vertebrata. In this study, we utilized a combination of both Energy Dispersive X-ray Spectrometry (EDX) and Thermal Ionization Mass Spectrometry (TIMS) to analyze both the chemical elemental distribution throughout conodont elements as well as the strontium isotopic content of experimentally altered conodont elements. Our findings reveal a common distribution of sulfur at early growth stages of several genera of ‘unaltered’ conodont elements indicating a common biologic origin unrelated to vertebrate enamel, but pointing to a distinct phylogenetic position within the vertebrate clade. The sulfur distribution signature was however determined to be absent in experimentally altered conodont elements, and may be a possible indicator of some low temperature diagenesis. This is a significant finding, as this study also revealed that changes to strontium isotope ratios in conodont elements can be achieved at lower temperatures and timescales than previously thought. This suggests that low CAI conodonts may in fact still experience significant diagenetic alteration in preserved strontium isotope ratios indicating that future studies should investigate several elements individually rather than as a bulk sample.