SEARCH Articles Figures Tables 8.6.2 Ohio Range Devonian:Horlick Formation Black shale Devonian Coals Devonian Devonian Early Devonian Middle Devonian Source Shales Devonian Upper Devonian age Devonian era Devonian oil shales Devonian period Devonian period, sedimentary rock Devonian rocks Devonian samples Devonian shale Devonian shale minerals Devonian shale, thermal Devonian, upper, black shales Devonian-Mississippian black shales Great Devonian Controversy Marcellus formation middle Devonian Middle Devonian Keg River Middle Devonian rocks Siluro-Devonian Taylor Group, Devonian