Figure 1
BSE images of shell cross-sections depicting the internal structure of Pulleniatina obliquiloculata shells. (a) mode of sectioning the shell. (b, c) BSE images of etched shell surfaces. (d, e, f) BSE images of highly polished, not etched, surfaces; these surfaces were used for EBSD measurements. Well visible is the subdivision of the shell wall by the primary organic sheet (POS) (red arrows in (b, e, f)) into two layers (b, c). These have different microstructures (white and yellow stars in (b) and (c)). White dots in (b, c) indicate the pores that are filled with EPON resin. The course of the POS is very evenly (e.g. (e)) curved and predefines the curvature of the chamber. In contrast, the course of other organic incorporations (yellow arrows in (d, e)) is wavy. The blue arrow in (b) and (e) indicates the cortex. The thickness of the latter varies slightly between 2–4 µm (e).
