Fig. 8.

EBSD band contrast image of hydrothermally altered T. transversa shell. Alteration occurred at 175 °C for 28 days and was carried out in simulated burial fluid. In some parts of the shell the original fibrous shell microstructure was distorted by amalgamation of fibres due to alteration (yellow dashed rectangles). The amalgamation of fibres can be explained by lateral growth of the inorganic rhombohedral calcite (IRC) of one nanocomposite mesocrystal biocarbonate (NMB) fibre growing into the neighbouring fibre. Note that altered shell areas are next to shell areas which appear to be little affected by alteration (white dashed rectangle).