Fig. 13--Photomicrographs of Trenton porosity and diagenesis.

1. Intercrystalline and moldic porosity (p) in a completely dolomitized rock. Original texture was probably packstone or wackestone. PPL. Total Faist No. 2-12, 5172 ft.

2. Good intercrystalline porosity with residual oil. Texture originally may have been a packstone. PPL. Humble Riley No. 20, 4172 ft.

3. Fractures, largely infilled, in skeletal wacke/packstone. Dark blue areas are highly ferroan dolomite. Margins of the fracture are lined with zoned dolomite. PPL. Consumers Power Co. No. 204, 4190 ft.

4. Largely infilled fracture in dolopackstone. Calcite is stained pink; the other dominant mineral in fracture is sphalerite. PPL. Total Faist No. 2-12, 5104 ft.

5. Skeletal wackestone with an anhydrite nodule. Nodule is lined with ferroan dolomite (blue-green) and filled with anhydrite. PPL. Consumers Power Co. Zittel No. 2, 3703 ft.

6. Anhydrite-filled fracture in a dolowackestone. Thin-section is from the top of the Trenton. CN.Consumers Power Co. No. 210, 3979 ft.