Crystallographic variability and uniformity in Cretaceous heterococcoliths

摘要

The crystallographic orientations of calcite in several major groups of Cretaceous heterococcoliths in chalk from Dover, England, were investigated using electron backscatter diffraction (EBSD) and field-emission scanning electron microscope (FESEM) stereo-photogrammetry. The previous crystallographic classification of coccoliths according to sub-vertical and sub-radial orientations of the c-axis (V-units and R-units, respectively) were further divided into several types according to the orientations and inclination angles of c-and ai-axes. As a common property, all units were likely aligned with the calcite >481?481?< direction along the coccolith ring.