NEW CONODONT AND TRILOBITE OCCURRENCES FROM THE CAMBRIAN OF EASTERN ALASKA

New conodont recoveries from the Cambrian-Ordovician Jones Ridge Formation at its type section in easternmost Alaska allow significant refinement of the Late Cambrian (Furongian) conodont biozonation in this remote region. Previous, reconnaissance-level sampling in this ~150 m thick interval of carbonate strata, mostly limestone, which was deposited at the platform margin near the [present-day] western margin of Laurentia, had yielded only fairly long-ranging species diagnostic of the Proconodontus muelleri and Eoconodontus Zones. New finds, herein in ascending order of first occurrence, include: Cambropustula? sp., Prooneotodus gallatini, Proconodontus tenuiserratus, a primitive (?) unnamed species of Proconodontus, Cambrooistodus minutus, and Eoconodontus alisonae. These new occurrences confirm the presence at Jones Ridge of the Proconodontus tenuiserratus or P. posterocostatus Zone below the P. muelleri Zone, and the Cambrooistodus minutus Subzone of the Eoconodontus Zone. The specimen of probable Cambropustula is the first reported occurrence of that problematic genus from outside of Sweden, and also extends its known range upward into strata above the Paibian Stage, on the basis of associated trilobites and carbon isotopic data at Jones Ridge. The occurrence of Eoconodontus alisonae likewise is notable, as this species has been reported previously only from eastern North America and Kazakhstan. As in those other sites, the Jones Ridge E. alisonae was recovered from the C. minutus Subzone within deeper water carbonate facies deposited at or seaward of the platform margin. The shelfbreak to upper slope facies of the Jones Ridge Formation also yielded new trilobite collections that expand the known geographic range of several deep water Sunwaptan species, including Idiomesus ultimus. This trilobite species, previously reported only from uppermost Sunwaptan boulders in the Cow Head Group of western Newfoundland, was recovered from less than a meter below the horizon that yielded E. alisonae.