Conodont biostratigraphy of Devonian strata of west Texas and eastern New Mexico and the apparatus of Early Devonian Icriodus species

Conodont faunas obtained from Devonian strata in the subsurface of West Texas and eastern New Mexico permit biostratigraphic subdivision and dating of the Frame, Thirtyone and Woodford Formations in the Permian Basin. The dark shales and carbonates of the Frame Formation span the Silurian/Devonian boundary and contain a Lochkovian (Early Devonian), postwoschmidti Zone conodont fauna of Icriodus postwoschmidti, and coniform taxa. The carbonates and cherts of the Thirtyone Formation produced a fauna of Icriodus claudiae, Polygnathus pireneae, and coniform taxa, of the Pragian sulcatus to kindlei zones (Early Devonian). Abundant elements of I. postwoschmidti and I. claudiae permit apparatus reconstructions that suggest relationships to older species.; Conodont faunas from strata generally assigned to the Woodford Formation in the Permian Basin permit the resolution of two distinct shale units that are separated by a significant hiatus. Green and gray clay shales that rest on the lower Paleozoic carbonate section, or that have infiltrated into karst fillings in the carbonates, contain late Givetian to early Frasnian conodont elements (late Middle to early Late Devonian). The typically black pyritic shale of the Woodford Formation rests unconformably on the lower green and gray shale unit. Conodont faunas show that the black shale ranges in age from the middle to late Famennian (late Late Devonian), and the hiatus between the lower unit and the upper black shale unit spans much of the Frasnian.; Biostratigraphic resolution of conodont faunas in the Permian Basin permits timing and interpretation of depositional events in the basin and correlation to the Devonian eustatic sea-level curve. Comparison to strata to the west in New Mexico and Arizona, and to the Northeast in Texas and Oklahoma provides further evidence for the occurrence of Late Devonian tectonic events.; The Dimple Limestone, an Early Pennsylvanian allodapic carbonate that was subsequently moved by thrust faulting into the Marathon Uplift during the Ouachita orogeny, contains reworked Devonian conodonts. Identification of the conodont faunas recovered from the Dimple suggests the Woodford Formation as a source, and suggests that the hiatus between the lower and upper units of the Woodford includes a much shorter time-span in the southern part of the Permian Basin.