The type area for the Marcellus subgroup, a major target for natural gas in the Appalachian Basin, is located near the village of Marcellus, Onondaga County, New York. The Marcellus crops out in several road and stream exposures, but the type section designated by Cooper in 1930 is incomplete; the Union Springs Formation and the lower Oatka Creek Formation are covered. A new composite type section that incorporates the original section in Jackknife Ravine, as well as another stream, contains a nearly complete exposure of the Marcellus subgroup. The composite type section now incorporates the lower most unit of the Marcellus overlying the Seneca Member of the Onondaga Limestone, the Union Springs Formation. The Union Springs Formation consists solely of the Bakoven Member in the type area marking the drowning of the Eifelian carbonate ramp and the base of the Hamilton Group. The Oatka Creek Formation, the first complete depositional sequence of the Hamilton Group, consists of five members in the composite type section: the Hurley, Cherry Valley, East Berne, Chittenango, and Cardiff. The Mottville Member of the Skaneateles Formation overlies the Cardiff, which marks the upper contact of the Marcellus subgroup. The total thickness of the Marcellus in the type area is approximately 83 meters.