Title: Biostratigraphy of Carboniferous of Northern Alaska: ABSTRACT
Abstract:Depositional patterns and facies are major controlling factors of Carboniferous biostratigraphy in Arctic Alaska. Marine onlap was dominant in the Early Mississippian, the most continuous deposition b...Depositional patterns and facies are major controlling factors of Carboniferous biostratigraphy in Arctic Alaska. Marine onlap was dominant in the Early Mississippian, the most continuous deposition being in the central part of the Brooks Range. On both the northeast and west, progressively younger Mississippian beds lie on older Paleozoic terrane. Correlations with other parts of the American Arctic indicate that this northward and eastward onlap was a general pattern in the Carboniferous; Eurasian and cosmopolitan faunal elements became more prominent after mid-Mississippian time. Oldest marine rocks are in the Shainin Lake area, central Brooks Range, where basal Mississippian nearshore clastic rocks succeed Upper Devonian nonmarine strata. By Meramec time the seas had spread across northern Alaska, except for the northernmost areas (Barrow-Sadlerochit Mountains trend). Carbonate deposition continued into the Pennsylvanian and Early Permian near the center of the eastern Brooks Range, but there was uplift in the Sadlerochit-Shublik Mountains area after mid-Pennsylvanian time. Megafossil zonation is based mainly on ranges and occurrences of lithostrotionoid corals, brachiopods, bryozoans, echinoderms and mollusks. Early Mississippian (Kinderhook-Osage) zones are (in ascending order): Leptagonia analoga, Cryptoblastus, Zaphrentis konincki, Unispirifer tenuicostatus, and Brachythyris suborbicularis. Late Mississippian (Meramec-Chester) zones are: Naticopsis suturicompta, Lithostrotion (Siphonodendron) aff. L. asiaticum, Eumetria costata, Sciophyllum lambarti, Goniatites cremistria, Gigantoproductus striato-sulcatus, and Lithostrotion (Siphonodendron) spp. Pennsylvanian megafossil zonation is not as clearly defined as that for the Mississippian, but two main assemblages occur: a Morrowan bryozoan-echinoderm assemblage and an Atokan Corwenia-Lithostrotionella assemblage. Larger fossils other than corals are rare in the Pennsylvanian strate. The megafossil succession is consistent with that developed for the Foraminifera by B. L. Mamet and only minor difficulties arise when correlations are attempted with other parts of the world. End_of_Article - Last_Page 2478------------Read More