The Logan Formation is a succession of siliciclastic sedimentary rocks of Early Mississippian age in eastern Ohio, USA. It is subdivided into four units - ascending from the base, they are the Berne Conglomerate Member, the Byer Sandstone Member, the Allensville Member, and the Vinton Member. The basal Berne Conglomerate is a thin (sometimes absent) quartz-pebble conglomerate horizon. The overlying Byer is a moderately thick, yellowish-brown to brownish-colored, limonitic quartzose sandstone unit. The Allensville is a coarse-grained sandstone to granulestone horizon. The uppermost unit is the Vinton, which is dominated by siltstones but sandstones and shales are also present. The Byer is the most fossiliferous unit. The Vinton is usually sparsely fossiliferous at best, but fossil horizons are not uncommon in some sections. Fossiliferous horizons in the Logan Formation usually consist of limonite-stained molds, dominated by brachiopods and crinoid stem columnals.

The Vinton Member rock shown above is the bottom surface of a fine-grained sandstone. The large sinuous structure is a megaburrow (trace fossil).

Stratigraphy: Vinton Member, upper Logan Formation, upper Waverly Group, Osagean Stage, upper Lower Mississippian