Changes

The '''postdepositional stage''' is the time after final deposition. All the porosity that forms during this stage is diagenetic or secondary in origin. Diagenetic processes are related to changes in water chemistry, temperature, pressure, and water movement.

The '''postdepositional stage''' is the time after final deposition. All the porosity that forms during this stage is diagenetic or secondary in origin. Diagenetic processes are related to changes in water chemistry, temperature, pressure, and water movement.

==Time-porosity table==

==Time-porosity table==

The following table and chart list time–porosity terminology and relationships.

The following table and chart in [[file:predicting-reservoir-system-quality-and-performance_fig9-68.png|Figure 1]] list time–porosity terminology and relationships.

 

[[file:predicting-reservoir-system-quality-and-performance_fig9-68.png|thumb|{{figure number|9-68}}After .<ref name=ch09r10 />]]

==Postdepositional substages==

==Postdepositional substages==

The '''mesogenetic substage''' (middle diagenetic) encompasses the time when the sediment is out of the influence of surface diagenetic processes. Cementation is the major process. [[Porosity]] obliteration occurs when mosaics of coarsely crystalline calcite precipitate in large pores. Pressure solution occurs at higher pressures.

The '''mesogenetic substage''' (middle diagenetic) encompasses the time when the sediment is out of the influence of surface diagenetic processes. Cementation is the major process. [[Porosity]] obliteration occurs when mosaics of coarsely crystalline calcite precipitate in large pores. Pressure solution occurs at higher pressures.

The '''telogenetic substage''' (late diagenetic) occurs when sedimentary carbonates are raised to the surface and erosion occurs along unconformities. The telogenetic zone extends from the surface to the point where surface processes no longer influence diagenesis. Solution by meteoric water creates porosity. Internal sedimentation and cementation by precipitation from solution destroy porosity.

The '''telogenetic substage''' (late diagenetic) occurs when sedimentary carbonates are raised to the surface and erosion occurs along unconformities. The telogenetic zone extends from the surface to the point where surface processes no longer influence diagenesis. Solution by meteoric water creates porosity. Internal sedimentation and cementation by precipitation from solution destroy porosity.

==Path of diagenesis==

==Path of diagenesis==

The parts of the path of diagenesis that a carbonate sediment follows determine the evolution of its porosity. The figure below summarizes the diagenesis that occurs along the path.

The parts of the path of diagenesis that a carbonate sediment follows determine the evolution of its porosity. [[:file:predicting-reservoir-system-quality-and-performance_fig9-69.png|Figure 1]]summarizes the diagenesis that occurs along the path.

 

[[file:predicting-reservoir-system-quality-and-performance_fig9-69.png|thumb|{{figure number|9-69}}Modified. Copyright: Harris et al., 1985; courtesy SEPM.]]

==See also==

==See also==