Age: Radiolarians indicate a Late Pennsylvanian to Middle Permian age; the conodonts restrict the age to Sakmarian-early Artinskian (middle Early Permian; see fig. 6) (from p. 13)

Two conodont samples from the Seventymile terrane in the Big Delta D-1 quadrangle (loc. 8, fig. 2; locs. 8a, 8b, table 1) yielded conodonts of Permian age. Red chert from locality 8a was collected for radiolarians but also yielded a few conodonts. The radiolarians are Late Pennsylvanian to Middle Permian; the conodonts restrict the age to middle Early Permian (Sakmarian and early Artinskian; fig. 6). A re-collection of red chert in the same vicinity (loc. 8b) yielded only one poorly preserved Mesogondolella sp. of Permian age. Radiolarians from this sample indicate a Late Pennsylvanian or early Early Permian (Asselian and Sakmarian) age (loc. 8b, table 1). Thus, taken together, the collection is restricted to the Asselian and Sakmarian. On the basis of conodonts from locality 8a and radiolarians from locality 8b, both samples could be of the same or nearly the same age--Sakmarian and early Artinskian (fig. 6) (from p. 18)

Three radiolarian collections of late Paleozoic age are known from the Seventymile terrane. Two of these collections are from red chert associated with green-and-gray chert interlayered with basaltic greenstone that, in turn, occurs with the peridotite of Salcha River (Foster and others, 1994) in the northeastern part of the Big Delta quadrangle (Foster and others, 1978). The two samples were collected near one another at different times (loc. 8, fig. 2; locs. 8a, 8b, table 1). Both samples yielded radiolarians, as well as a few conodonts. The sample collected in 1975 (loc. 8a, table 1) was described by Foster and others (1978) in generalized taxonomic terms. The other sample (loc. 8b), colleced in 1977, contains much the same radiolarians (B.L. Murchey, written commun., 2002), including several specimens of Pseudoalbaillella sp., subordinate Triactofenestrella sp., and rare Paronaella? cf. P.? A of Murchey (1990), indicating a Late Pennsylvanian or early Early Permian age. The associated conodonts in both collections restrict that age to Sakmarian to early Artinksian (middle Early Permian, fig. 6). According to B.L. Murchey (written commun., 2002), the radiolarians in both collections are generally found in argillaceous and cherty facies that were deposited along teh maring (outer slope) of late Paleozoic North America. Because the faunas are fairly diverse, the radiolarian-bearing chert might have formed between very proximal facies dominated by such forms as Triactofenestrella and Paronaella? cf. P? sp. A. of Murchey (1990)(wagonwheel or discoidal forms, possibly with photosynthetic symbionts) and typical distal ribbon-chert faunas dominated by such elongate forms as Pseudoalbaillella. The radiolarian faunas from the Big Delta quadrangle are similar to those of the Havallah Formation in Nevada, which likely formed in a back-arc basin. (from p. 19)