Data from 590 wells in Antrim and Kalkaska counties of Michigan were used to model pinnacle reefs in the northern trend of the Michigan basin. The data consisted of tops for 6 units: Niagaran Formation, Gray and Brown; Salina Formation, A-1 Evaporite and Carbonate, and A-2 Evaporite and Carbonate.

Building grids and contour maps of the top of Niagaran Brown (Pinnacle) surface using standard algorithms produced a surface that projected below and above the interreef surface. By using a combination of standard algorithms, filters, and surface and data operations the Pinnacles and interreef (nonreef Niagaran Brown) surface were acceptably gridded. The Salina evaporites and carbonates are usually modeled using either direct gridding or addition of a thickness grid to an adjacent surface. However, these approaches did not produce surfaces that reflected the geologist's interpretation. Simple modifications to the thickness-gridding approach allowed more accurate representation of the geology. The evaporites were gridded assuming they were deposited parallel to a paleo-water surface. T e carbonates were gridded assuming they draped the surface existing at the time of deposition.