Revised Megafossil Biostratigraphic Zonation for Carboniferous of Northern Alaska: ABSTRACT

Abstract

Carboniferous megafossils are widely distributed in the Kayak Shale and Lisburne Group throughout the northern Brooks Range. Diverse assemblages of brachiopods, corals, and mollusks, with subordinate echinoderms and bryozoans, were collected from 40 measured sections. The combined stratigraphic ranges and abundances of more than 300 species were assessed to construct a biostratigraphic zonation that can be applied regionally for correlation. Preliminary zonations, used for more than a quarter century, were revised to account for the rapidly accumulating data. The 18 assemblage zones, from youngest to oldest, are: Umboanctus? sp., Corwenia jagoensis, Choristites? sp., Delepinoceras sp., Siphonodendron ignekensis, Gigantoproductus striatosulcatus-Stelechophyllum? aff. S.? m lareni, Goniatites americanus-Siphonodendron lisburnensis, Sciophyllum lambarti, Eumetria costata, Stelechophyllum? mclareni, Naticopsis suturicompta-Lithostrotion reiseri, Skelidorygma subcardiiformis, Spirifer tenuicostatus-Siphonodendron dutroi, Sychnoelasma konincki s.1.-Actinocrinites sp., Brachythyris choteauensis, Cryptoblastus-Pentremites, Leptagonia analoga, and Scalarituba-Lepidodendropsis. In the central and western Brooks Range, the deeper water Kuna formation contains a low-diversity fauna of mollusks and brachiopods. Goniatites are found at several levels but never more than two zones in any partial section. Regionally, these goniatite zones, from youngest to oldest, are: Delepinoceras (late Chesterian), Goniatites americanus (late Meramecian-early Chesterian), Beyrichoceras (early to middle Meramecian), Ammonellipsites (Osagean) and Muensteroceras-Protocanites (late Kinderhookian?). Correlations of megafossil zones with the foraminiferal zones of Mamet are discussed. The 15 Mississippian zones have an average age-resolution of about 2 m.y. By themselves, the goniatite zones give an age-resolution of about 6 m.y. zone. End_of_Article - Last_Page 663------------