Abstract
Pennsylvanian and Permian radiolarians are common constituents of the allochthonous siliceous rocks of the Cordillera of North America. Eight widely distributed Pennsylvanian and Permian radiolarian assemblages are defined for this region. These assemblages are dated by (1) joint occurrence with conodonts, as well as by (2) correlation with dated radiolarian-bearing sequences on the craton of North America. From oldest to youngest, these assemblages are: (1) Pseudoalbaillella sp. A Assemblage: In Nevada this assemblage occurs with Desmoinesian conodonts. It correlates with Desmoinesian radiolarian faunas from Oklahoma. (2) Ps. U-forma-Ps. elegans Assemblage: This assemblage occurs with late Wolfcampian conodonts in Alaska. It apparently correlates directly with the Japanese assemblage of the same name. (3) Ps. sp. B-Ps. elegans Assemblage: The biostratigraphic position of this assemblage is uncertain. It predates Ps. scalprata Assemblage and probably postdates Ps. U-forma-Ps. elegans Assemblage in the Cordillera. This assemblage cannot be correlated directly with known North American cratonal faunas or with Japanese assemblages. (4) Ps. scalprata Assemblage: This assemblage occurs with Leonardian conodonts in Nevada and Alaska. It may be equivalent to the Japanese assemblages Ps. lomentaria and/or Ps. rhombothoracata. The latter occurs with late Wolfcampian conodonts. (5) Ps. sp. aff. Ps. rhombothoracata-Ps. sp. aff. Ps. sakmaraensis: This assemblage is not independently dated in the Cordillera; it appears, however, to grade into Follicucullus scholasticus Assemblage. It may be correlative with the Ps. rhombothoracata Assemblage in Japan and with the Leonardian Bone Spring Limestone of Texas. (6) Ps. fusiformis Group Assemblage: This assemblage is younger than or equivalent to the Cordilleran Ps. sp. aff. Ps. rhombothoracata-Ps. sp. aff. Ps. sakmaraensis Assemblage. The lower part of the assemblage zone correlates well with the Leonardian Bone Springs Limestone. The most closely related Japanese assemblage is Ps. globosa Assemblage. (7) Follicucullus scholasticus Assemblage: This assemblage occurs with Wordian(?) conodonts in northern California. It is apparently correlative with the Guadalupian Lamar Limestone of Texas and with the Japanese assemblages Fo. moancanthus(?) and Fo. scholasticus. (8) Neoalbaillella Assemblage: This assemblage correlates with either Na. optima and/or Na. ornithoformis Assemblages in Japan. Elements of this assemblage overlie Wordian brachiopods and underlie Middle Triassic ammonites in Nevada. The assemblage is not known to occur on the craton of North America. End_of_Article - Last_Page 522------------
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