Abstract: Porosity Reduction by Chemical Compaction--Stable-Isotope Model

R. M. Lloyd

Chemical compaction is a general term encompassing several specific processes (pressure solution, stylolitization, etc.) which lead to porosity reduction without the addition of new solid. The loss of porosity is compensated exactly by a reduction in bulk volume. In carbonates, chemical compaction is characterized by the chemical reorganization of at least part of the solid carbonate accompanied by isotopic reequilibration with pore water and loss of pore water. The isotopic changes that will occur in the carbonate can be modeled for different burial histories, temperature gradients, and compaction rates. Interpreting the final isotopic composition of a given tight limestone in the light of these models can yield significant conclusions as to porosity history.

An example of this approach using the Tamaulipas Formation (a Lower Cretaceous pelagic limestone) of central Mexico demonstrates that the Tamaulipas Formation retained significant porosity until late in its burial history.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC