Fig. 9.10. Scanning electron micrographs of calcitic chalk showing coccolithic rings and skeletal fragments of algal nannoplankton. Unlike aragonitic lime mud,
chalk does not undergo neomorphism, so porosity may be preserved, though permeability is low, due to fine particle size. (Left) Lower Campanian chalk, Fannin County, Texas. (Right) Coniacian chalk, Kiplingcotes Station quarry, Yorkshire. (Courtesy of J. M. Hancock.)