Trenton strata in the western Illinois basin are very good prospects for oil exploration. Much drilling has been done in the area but, as yet, no producing wells have been completed. Oil stains and some tars have been found in some samples from most wells.
The Trenton in the area of Brown and Schuyler Counties is a fine-grained limestone that underlies the Maquoketa Shale at an average depth of 800 ft (244 m). Because of its position near the edge of the Illinois basin, the stratigraphy varies considerably and inconsistencies are present in most samples viewed.