Abstract
The study of diagenetic events within the Devonian Detroit River Group sour zone carbonates reveals several stages of anhydrite development: (1) massive, bedded anhydrite; (2) nodular anhydrite; (3) pore-filling anhydrite; and (4) postcompactional laths. The massive, bedded anhydrite was deposited as subaqueous gypsum. The nodular anhydrite developed in early stages of shallow burial diagenesis. Abundance of nodules decreases vertically, away from the subaqueous, massive anhydrite deposits. These anhydrite nodules, also originally gypsum, grew displacively within sabkha carbonate muds. Nodular anhydrite is visible in hand samples as individuals or as a network of reticulate ovate patches. Within pelletal micrites, dolomicrites, and oolitic packstones, abundant solution vugs have been greatly or entirely reduced by middle to late diagenetic precipitation of a meshwork of individual crystals or singular crystals of primary anhydrite. Euhedral, randomly oriented anhydrite laths are also present but are not precipitated within macropore spaces. These laths, which reveal a postcompactional origin, are often abundant and form a decussate pattern easily seen in hand sample.
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