porosity

depth

porosity

depth

This review indicates that mud-rich shallow marine carbonates behave differently than sand-rich, grain-supported sediments with regard to reduction in porosity and thickness. Quantitative analysis of compaction behavior in carbonate sediments reveals that, barring early cementation, carbonate muds suffer significant thickness reduction early in their burial history and at shallow depths, e.g., 50% thickness reduction with about 150-200 m overburden. However, primary porosities of carbonate muds, approximately 70-80%, are reduced only to about 42% under that overburden. Thus, the potential exists for significant retention of primary porosity in carbonate muds in the form of microporosity. This indicates that interparticle cementation, with or without chemical compaction, is required to transform muddy carbonate sediments into lithified rock. In the absence of early lithification, carbonate sands compact more slowly than muds. Primary interparticle porosities of about 40-45% can be maintained in the first 200-300 m of burial, with little thickness reduction.