APPLICATIONS OF ELECTRON BACKSCATTER DIFFRACTION ON FOSSILIZED AND MODERN EGGSHELL

Electron backscatter diffraction (EBSD) provides high resolution information on crystal orientation and is routinely used in material science. Recently this technique was used to analyze the crystallography of fossilized and modern eggshell. Eggshell microstructure was examined for dinosaur eggs from the Cretaceous Tiantai Basin of Zhejiang Province, China, fossilized turtle eggs from the Cretaceous Kaiparowits Formation of Utah, and modern avian eggs. The samples used in this study were cut radially and micro-polished for mapping. The EBSD detection on a scanning electron microscope was used to map the average orientation of the crystals pixel by pixel. The orientations were then identified using the pixel data and displayed in maps and stereographic pole figures to show the preferred orientation and spatial arrangement of individual crystals. Details of calcite and aragonite structure of the eggshells, (i.e., preferred orientation, misorientation between adjacent shell units, lattice distortions, and sub-grain structure), were then observed and quantified. The avian eggshell will be mapped in order to compare the structure to the fossilized dinosaur eggshell, thereby showing possible morphologic differences and effects of diagenesis. The turtle eggshell will be mapped to show both preferred orientation and location of possible calcite replacement of the original aragonite. This technique allows the microstructure of fossilized and modern eggshell to be studied at high resolution and could be used for morphological and diagenetic studies.