Date of this Version
Published in Transactions of the Nebraska Academy of Science, Volume 4 (1977).
Chalk is affected by different diagenetic processes in comparison with other carbonate rocks. Commonly observed lithification processes are pressure-solution and reprecipitation and neomorphism. The first process is divisible into: (a) spot-welding or welding; (b) overgrowth; (c) stylolitization and cementation. Further, pressure-solution and reprecipitation is dependent on (a) geostatic pressure and (b) the ratio of Mg/Ca in the pore fluid. Overgrowth of calcite cement is controlled by the size and shape of the biogenic crystals. Neomorphism is also important in diagenesis. Neomorphic process dominates when pressure-solution process is ineffective. Organic and insoluble residue content dictate neomorphism. In conclusion, pressure-solution or neomorphism or a combination of both accounts for various modes of lithification observed in chalk.