STUDYING CRYSTALLINE STRUCTURE OF CONODONT MICROFOSSILS WITH X-RAY DIFFRACTION

Conodonts are agnathan chordates and the tooth-like elements of their feeding aparatus can be used to provide chemical and thermal information on the ancient ocean and related sedimentary basins. These abundant microfossils have been used to assess the thermal history of geologic formation through the establishment of the Conodont Color Alteration Index (CAI). CAI is a common qualitative method used to assess the past thermal history that relies on an optical assessment of the fossil color. Additional studies have suggested that there are chemical and structural changes that could also be used to create a more quantitative metric. Changes in the crystalline lattice also can dictate uptake of trace elements and lead to differences during diagenesis. Moreover, systematic investigations of structural variations in different conodont elements can be used to provide additional paleobiological information of this important clade. In the present study, we analyzed the crystalline structure of cone-like conodonts (coniform elements) using a Bruker D8Quest single crystal X-ray diffractometer equipped a CMOS area detector, which allows us to explore diffraction patterns of both highly-ordered, single-crystal and polycrystalline material. The elements displayed variability along the length of the element ranging from single crystalline to polycrystalline. Mesocrystallinity was noted in a large subset of the samples with texturing also observed in the polycrystalline regions. The use of mosaicity and β values will be discussed as potential structural metrics to describe crystallographic changes in conodont elements.