ABSTRACT

The carbonate members of the Dennis Formation can be divided into five regional diagenetic facies that are defined by differing preservation of originally unstable carbonate grains. Such grains contain no relict internal structure in the uppermost facies (A); they are better preserved in middle facies (B and C); and they are well preserved in the lowest facies (D). A fifth facies (E) contains no originally unstable grains and is characterized by a microcrystalline dolomite fabric. The five facies exhibit differing patterns of compaction and dolomitic void filling.

The textures and interpreted diagenetic environments of the diagenetic facies were caused by progressive interaction of initially unsaturated meteoric water with the marine sediments during a general regression. Transfer of CaCO₃ in that interaction and the resulting distribution of cements governed later patterns of pressure solution and void filling by ferroan dolomite. Paleohydrologic controls caused irregularities in the distribution of diagenetic facies. Paleotopographic and depositional trends derived from diagenetic evidence agree with previous interpretations based on depositional evidence.