ABSTRACT

Detailed analysis of the petrography and distribution of compositionally zoned ferroan calcite and dolomite cements in the Devonian, Kaybob Reef Complex of Alberta, Canada, has demonstrated that porosity occlusion is predominantly a result of burial diagenesis to depths in excess of 4 km. Different but temporally related mechanisms of formation are indicated for the two cement types: coarsely crystalline dolomite and coarsely crystalline calcite. Calcite cement precipitational history, determined by correlation of compositional zones, demonstrates that pressure solution along stylolites was the essential mechanism of calcite cementation in the reef-interior and to a lesser extent in the reef-slope facies. Zoned dolomite cements are, in contrast, the major cement type in the reef-margi and reef-slope facies; a basinal source for dolomite precipitating fluids is indicated. It is suggested that the composition of basin-derived pore waters was controlled by temperature dependent clay mineral reactions as a function of progressive burial.