AGE OF THE UDDENITES SHALE

The age of the Uddenites shale bed of the Gaptank Formation has been a source of major controversy since it was first named. Various authors have considered it to be Carboniferous or Lower Permian. Two ammonoid localities have been identified, one at the saddle at Wolf Camp and the other 4.5 to 5.5 miles northeast of Wolf Camp. These localities have been correlated based on the occurrence of Uddenites . The age discrepancy of the Uddenites shale is based largely upon fusulinacean analysis by various authors. Analysis of the ammonoid faunas suggest that the two localities are stratigraphically and faunally distinct. The ammonoid locality 4.5 to 5.5 miles northeast of Wolf Camp contains Uddenoceras oweni and U. harlani ,whereas the ammonoid locality at the saddle contains Uddenites schucherti and U. minor along with a new undescribed species of Uddenoceras. The saddle locality contains fairly advanced species of Vidrioceras (V. uddeni, and V. irregulare whereas the locality northeast of Wolf Camp contains primitive species of Vidrioceras including V. conlini and V. n.sp. The saddle locality contains an advanced species of Shumardites S. simondsi whereas the locality northeast contains a more primitive species including Shumardites cuyleri, along with Parashumardites. Based on correlation of these distinctive ammonoid faunas with north-central Texas, the saddle locality is considered to be mid-late Virgilian, and the locality northeast of Wolf Camp is assigned a lower Virgilian age. These conclusions are compatible with previous correlations of fusulinaceans by Ross.