The origin of Middle Cambrian-hosted mid-platform dolomite: Cathedral Formation, Whirlpool Point, Alberta

Dolomite laminites, replacement dolomite, and saddle dolomite spar form a single genetic unit in a mid-platform dolomite body of the Cathedral Formation. The dolomite body consists of a stratiform halo of replacement dolomite surrounding central pervasively dolomitized breccia zone. Primary fine-grained dolomite laminites change in character and chemistry laterally northward from the breccia zone. Fluids that precipitated syndepositional dolomite laminites and diagenetic dolospar and replacement dolomite had an average near surface temperature of 143°C and were enriched in 18O relative to Middle Cambrian seawater.; Northeast trending changes in thickness of the Cathedral Formation across the Middle Cambrian platform is attributed to the reactivation of basement faults during post-rift thermal subsidence. Thermally driven convection of dolomitizing fluids through the basement accounts for the high temperature and enriched isotope values. Regional dolomite trends in Middle Cambrian stratigraphy are attributed to and approximated by the basement Regmatic Fracture Pattern.