Pinnacle reefs in eastern Michigan were formed during a period of cyclic carbonate-evaporite deposition in uppermost Niagaran-lower Salinan time. At present, reef sequences have salt beds as their lateral equivalents. Restoration of evaporite sequences to their relative positions during deposition demonstrates, however, that this is due to differential compaction of carbonate beds, rather than contemporaneous deposition of reef rock and evaporites. Compaction of carbonate muds during lithification, rather than cementation, also accounts for the majority of porosity loss in the area. Where porosity is preserved, compaction-resistant framework is present with the resulting porosity directly proportional to quantity of framework.

The reef and surrounding carbonates are dolomitized. The pattern of dolomitization, quantity of dolomite in relation to bed thickness, position of the dolomites in relation to evaporite beds, and time of dolomitization suggest that dolomitization was caused by a continuous movement of large quantities of normal connate waters through the sediments. It cannot be shown that refluxion by highly concentrated brines during periods of evaporite deposition contributed substantially to dolomitization. Evaporite sequences overlying bodies of carbonate mud prevented the vertical escape of water during compaction, forcing this water to flow laterally to the reefs, and then vertically through them to the surface. This very large quantity of water was forced through a relatively small volume of ro k in the nearby reef area, supplying the magnesium for dolomitization. The outflow of water continued during intensely evaporitic cycles, altering evaporite deposition in the reef area, and preventing heavy brines from entering the porous reefs and destroying porosity.

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