| Description |
Lower Middle Cambrian rocks in northern Utah and southeastern Idaho are diverse in composition and sequence. Contrasts in the rock sequence have required new nomenclature and modified usuages of the names Brigham, Langston, and Ute. Strata formerly assigned to the Langston Formation have been divided into the Naomi Peak Tongue of the Twin Knobs Formation, the Spence Tongue of the Lead Bell Shale, the High Creek Limestone, and the Langston Dolomite. During the Middle Cambrian, lithofacies of the inner dotrital, middle carbonate, and outer detrital belts developed roughly parallel to the ancient Cambrian coastline. Detrital sediments of the Brigham Quartzite and the Ute Formation were deposited in the inner detrital belt. The outer detrital belt is represented by the Spence Tongue of the Lead Bell Shale. The Naomi Peak Tongue of the Twin Knobs Formation, the High Creek Limestone, the langston Dolomite, and the carbonate units of the Ute Formation represent the middle carbonate belt. The biostratigraphic framework for the part of the Cambrian represented by the Twin Knobs Formation, Spence Tongue, Langston Dolo mite, High Creek Limestone, and Ute Formation consists of the Albertella., Glossopleura. and possibly the lower part of the Bathyuriscus-EIrathina Zone. In this paper, the trilobite faunas of each zone are subdivided into informal units designated as faunules. The Albertella Zone fauna Is divided into four distinct faunules and the Glossopleura Zone fauna consisof two less distinct faunules, The distribution and succession of faunules appears to be environmentally controlled. The boundary between the Albertella and Glossopleura Zones is placed at the first occurrence of Glossopleura in the lower Spence Shale Tongue although no significant faunal change appears at this point, The lower boundary of the Eathyuriscus-Elrathina Zone is tentatively placed at the first occurrence of typical Ehmaniella in the basal shales of the Ute Formation. Forty-seven-genera and 99 species of trilobites, seven unassigned trilobites, and two genera and four species of echinoderms were collected, described;, and illustrated. In addition, several of Resser's type specimens were reillustrated for comparison. One new Eodiscoid species of Agnostida, lagetia lira, is described. One new genus, Zeugospina, and 16 new species of Corynexochids are described which Include Albertella gynthos, Albertelioides fritzit Dory-pyge wellsvillensis, Glossopleura granosa, G. punctatum, Kootenia aircuata, K. melindensis. K. wellsvillensis, Olenoides spencei, Poliella milleri, Ptarmiganoides stokesi, Zacantholdes avernus, Z. fedori, Z. latust Z, prolixus, and Zeugospina guntheri. Six new genera, Haladella, Naomiaspis, Nyellina, Oraspis, Palmerella, and Pseudomexicella, and 21 new species of Ptychoparioids are described, which include Alokistocare mccollumi, A. nannos. A. mutablis, A, melindensis, Achlysopsis punctatum, Caborcella cracens, Ehmaniella petalora, E. stibinus, Maladella oculatus. Mexicella granosat Naomiaspis typicalls, Nyelja periosus, N. limbus, Nyellina maladensis, Onchocepha- stibinus, Oraspis limbus, Pachyaspis eurylimbus, Palmerella exiguus, Prohedinia? spencei, Pseudomexicella granulosa, and Volocephalina stokesi. |
