Geologic units in Covington City, Virginia

Brallier Formation (Devonian) at surface, covers 12 % of this area: Brallier Formation - Micaceous shale, siltstone, and sandstone.
Lithology: shale; siltstone; sandstone
Ridgeley Sandstone, Helderberg and Cayugan Groups (Silurian-Devonian) at surface, covers 18 % of this area: Ridgeley Sandstone, Helderberg and Cayugan Groups - Calcareous sandstone; partly cherty limestone; calcareous shale; fossiliferous.
Lithology: limestone; sandstone; shale
Millboro Shale and Needmore Formation (Devonian) at surface, covers 71 % of this area: Millboro Shale and Needmore Formation - Black, fissile shale; gray calcareous shale; Tioga metabentonite at top of Needmore.
Lithology: black shale; shale; bentonite; limestone