The Tibbstown Formation of the Culpeper Group is here named for outcrops in Tibbstown in the Barboursville basin, Va. At the top of the formation in different localities are two conglomerate members with which it intertongues, the Haudricks Mountain and Mountain Run Members. It is composed of reddish-brown, feldspathic, micaceous sandstone interbedded with coarse-grained, pebbly, arkose conglomerate. It gradationally overlies the Balls Bluff Siltstone. The upper contact has been removed by erosion. South of Culpeper most of the Tibbstown lies adjacent to intrusive diabase and is incorporated in its thermal metamorphic aureole. Thickness averages 300 m (1,000 ft) in the Culpeper basin and 450 m (1,500 ft) in the Barboursville basin. Age is probably early Norian based on sporomorphs from shale in the Tibbstown.

Source: GNU records (USGS DDS-6; Reston GNULEX).