In the Michigan basin, the Middle Silurian Niagaran reef facies directly underlies the Upper Silurian Salina evaporite facies. The basal Salina Formation includes the A₁-evaporite, subjacent to the A₁-carbonate and the A₂-evaporite in successive order. Subsurface study of 40 drill cores disclosed that most of the Niagaran pinnacle reefs in the inner-basin slope environment ceased growth by A₁-evaporite time and were regenerated during deposition of the A₁-carbonate.

The uppermost section of the algal stromatolite and algal boundstone facies at the top of the pinnacle reefs was deposited contemporaneously with the A₁-carbonate of the off-reef section. The algal-stromatolite facies of the A₁-carbonate overlies the A₁-evaporite on the reef flanks and extends laterally to the off-reef facies in the vicinity of the pinnacle reefs. The general lithology of the A₁-carbonate in the off-reef sections differs greatly from the lithology of the A₁-carbonate reef facies.

Some of the pinnacle reefs apparently continued to grow during the early formation of the A₂-evaporite. There is no significant erosional contact between the A₂-evaporite and the algal stromatolite at the top of the reef. Furthermore, LLH- and SH-type algal stromatolites show repeated stages of growth in situ, within the lowermost few feet of the A₂-evaporite section.

A vadose zone representing subaerial exposure is present in the pinnacle reefs at the top of the organic reef facies, which overlies the basal biohermal facies. This zone is characterized by a more complex sequence of diagenesis than either the basal biohermal facies or the uppermost algal stromatolite facies.

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