Carbonate sediments of the northern reef trend in Michigan have been the subject of serious scientific scrutiny since the discovery of significant hydrocarbon reservoirs in pinnacle reefs in the late 1960s and early 1970s. The reef trend is a complex of reef and nonreef carbonate facies capped by an evaporite/carbonate sequence. The reef and the evaporite/carbonate sequence have been extensively described and discussed over the last decade. However, the nonreef (interreef) facies has received little more than brief descriptions throughout this time. As these nonreef carbonates are virtually barren of hydrocarbons, their analysis has been neglected.

Most exploration for pinnacle reefs centers around geophysical techniques; however, it should be considered that patterns of textural or geochemical gradients may occur between the reef masses and surrounding nonreef deposits. This study examines, in detail, the petrographic and geochemical character of these nonreef (interreef) sediments. These characteristics can provide additional data and a potential exploration tool for determining the spatial facies relationship between pinnacle reefs and interreef carbonates in the Michigan northern reef trend.

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