The Present Continental Setting

To further understand the origin of these calcite cement zones, it is necessary to determine the carbon and oxygen isotopic chemistry of each zone. The ranges of 

ESTIMATES OF WATER CHEMISTRY DURING PRECIPITATION OF CEMENT ZONES 

Mississippian 813C HCO3- -+2%o PDB 818Q = +0.5 %o SMOW assuming 25°C assuming 45°C 

The wide range of 8180 values for post-Mississippian Zone 5 cements reflects, in part, precipitation of these cements at elevated temperatures. The trace element contents indicate little seawater influence on water chemistry. The values are variable but intermediate and suggest intraformational or extraformational cement carbon sources owing to pressure solution in conjunction with stylolitization during progressive burial of the formation to a depth of about 1000 m (Meyers and Lohmann, 1985 Moore, 1989). 

Helderberg carbonates are extensively cemented by clear equant calcite cement that postdates marine cement and fills most of the original pores. These cements are compositionally zoned as shown by cathodoluminescence and trace element analyses. These precipitates include nonluminescent, bright and dull cements. The luminescent cement is the earliest generation of cement followed by 

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