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Radiolarian-bearing rocks have been collected from eastern Oregon (Rail Cabin Formation) and the Queen Charlotte Islands, British Columbia (middle member of the Kunga Formation). The Rail Cabin Formation consists predominantly of 365 m of thin-bedded, manganiferous argillite. The middle or black limestone member of the Kunga Formation consists of 210 to 280 m of thin-bedded, black carbonaceous limestone with minor amounts of black argillite.
The Rail Cabin Formation can be subdivided into two zonal units based on radiolarian biostratigraphy: a lower Mostlerium Zone (?Karnian, early Norian to late middle Norian) and an upper Pantanellium silberlingi Zone (late middle to late Norian). Samples from the middle member of the Kunga Formation contain radiolarians which are indicative of the Pantanellium silberlingi Zone. Norian ages for both radiolarian zones have been confirmed primarily by associated pectinacid bivalves.
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