Combined X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) Analysis of Strontium and Calcium Phases in An Ammonite

An ammonite is an extinct cephalopod that first appeared in the Late Silurian to Early Devonian Periods and became extinct at the end of the Cretaceous Period . There is a vast diversity of shapes and styles and colors. This diversity is fortunate as they are, in fact, classified based on the structures of the spiral or coiled chambers called camerae and exterior ridge features. The different shapes and features can also be characteristic of different time periods.

Fossils are ancient records of environmental conditions and indicative of their surroundings. Insight into compositional changes due to conditions of long ago periods in the Earth's history can be garnered through the application of modern analytical tools such as WDXRF with discrete small spot analysis capabilities and XRD.

In both the bulk xrf and xrd scans, Ca, Sr, were the two primary elements with Aragonite, Calcite, as the two primary phases. However, interesting trends appeared during 1mm diameter spot XRF analysis.Though not readily apparent in the bulk overall scans, distinct elemental differences were observed in various regions of the ammonite fossil structures, especially between the camerae or chamber walls, the cell interior and exterior structures. High concentrations of Strontium and Calcium existed in very specific regions, while Fe, Si and P existed within other regions of the ammonite structures. The regions highest in Sr and Ca are the septa, or cell walls that separate one chamber from the next. This septa was formed by the creature while living. Ordinarily, the septa would be principally composed of CaCO3, but the Sr presence is intriguing. This project deals with the combined XRF and XRD of the Strontium/ Calcium (aragonite to calcite phases) in these regions and possible implications of time period identifications, and possible environmental conditions either pre or post mortem.