318 Upper Triassic Radiolaria and radiolarian zonation from western North America

Radiolaria have proven to be of great value in interpreting the stratigraphy within complex geologic terranes. This report focuses on Norian age Radiolaria from strata in eastern Oregon (Rail Cabin Mudstone), Baja California (San Hipolito Formation), and the Queen Charlotte Islands, British Columbia (“Middle member” of the Kunga Formation). Fifty-four species and ten new genera are described herein.

A preliminary system of radiolarian zonation (two zones, five subzones) is proposed for the Norian Stage of the Upper Triassic of western North America. This zonal system has been based upon biostratigraphic data offered by pectenacid bivalves (Halobia Bronn, 1830), as well as various ammonites.

The lower Capnodoce Zone was originally defined by Pessagno (1979) and termed an Oppel Zone. In this report the Capnodoce Cone is expanded and divided into three subzones: a lower Justium novum Subzone; a middle Xipha striata Subzone; and an upper Latium paucum Subzone. The base of the Capnodoce Zone is defined by the first occurrence of Capnodoce DeWever, 1979. Other genera that make their apparent first appearance at or near the base of the zone are Loffa Pessagno, 1979; Renzium Blome, 1983; Justium Blome, 1983; Xenorum new genus; Corum new genus; Canesium new genus; Castrum new genus; Latium new genus; and Quasipetasus new genus. The top of the Capnodoce Zone is defined by the final occurrence of Capnodoce.

The upper Betraccium Zone is treated as an Oppel Zone and is dicided into two subzones: a lower Pantanellium silberlingi Subzone, and an upper Betraccium deweveri Subzone. The base and top of this zone are defined by the first and final occurrences of Betraccium Pessagno, 1979.

Newly described genera, in alphabetical order include: Canesium, Castrum, Corum, Ferresium, Latium, Laxtorum, Pachus, Quasipetasus, Xenorum, and Xipha. Newly described species include: Acanthocirus burnsensis, A. dotti, A. harrisonensis, A. izeensis, A. largus, A. laxus, A. lupheri, A. macoyensis, A. ochocoensis, A. prinevillensis, A. rotundus, A. silverensis, A. supleensis, A. usitatus, A. vigrassi, Betaccium (?) incohatum, B. inornatum, Canesium lentum, Canoptum (?) browni, C. farawayense, C. laxum, C. macoyense, Cantalum alium, C. globosum, Castrum perornatum, Corum perfectum, C. regium, C. speciosum, Gorgansium acutum, Ferresium contorum, F. hecatense, F. laseekense, F. loganense, F. lyellense, F. titulense, Latium longulum, L. mundum, L. paucum, Laxtorum atliense, L. hindei, L. kulense, Pachus firmus, P. indistinctus, P. longinquus, P. luculentus. Pseudoheliodiscus sandspitensis, Pseudosaturniforma minuta, Quasipetasus disertus, Q. insolitus, Syringocapsa turgida, Triassocampe immaturum, T. proprium, Xenorum flexum, X. largum, Xipha striata.

C.D. Blome

Pages: 88, 17 pls., 7 text-figs., 9 tables, appendix