The Precambrian or Canbrian Unicoi Formation in southwestern Virginia consists of at least three litho logically distinct rock sequences which can be distinguished as formations. The Uhicoi therefore should be raised to the rank of group. The lowest rock sequence is named Iron Mountain Formation; the middle sequence, consisting of three basalt flow and inter-layered claatic sedimentary rocks, an the upper sequence of clastic sedimentary rocks are not named.Ph. D.