| This report covers 21 collections, 16 from the Mississippian Lisburne group and 5 from the Permian Sadlerochit formation. Although the fossils are mostly crudely silicified and distorted, those that can be identified indicate a Late Mississippian age for the Lisburne group and a Permian (possibly Late Permian) age for the Sadlerochit formation. Correlation of the Lisburne here with the Alapah Limestone of the central Brooks Range is in line with mapping and stratigraphic correlations that have been carried on by Brosge and others during the past 10 years in the eastern Brooks Range. Lisburne Group The collections from the Lisburne fall into two groups: those from the lower 100 ft.; and those from the upper part, mainly the upper 100 ft. Concerning the corals from the lower part of the Lisburne, Duncan state: “None of the corals from beds assigned to the lower part of the Lisburne group in this area types known from the central Brooks Range. The occurrence of solitary corals suggestive of Faberophyllum, of lithostrotionoides, particularly the phaceloid form identified as Siphonodendron? (USGS 19570-PC), and of a Syringopora (USGS 19567-PC) comparable to a species that occurs in the lower Alapah are interpreted to indicate that most of the lower Lisburne in your area is of Late Mississippian age and probably equivalent to the lower part of the Alapah formation. There were no corals in the collection (USGS 19566-PC) made 5 to 10 feet above the base.” The few other fossils in these collections also suggest correlation with the lower Alapah. Gigantoproductus occurs with lithostrotionoid corals inmany places in the lower part of the Alapah limestone where it has been examined in the eastern Brooks Range. This has been previously explained by a change in the stratigraphic range of the genus from its high Alapah position in the central Brooks Range. In addition, Duncan remarks: “Few corals were obtained from the upper part of the Lisburne section. Those that do occur are types characteristically found in the later part of the Lower Carboniferous.” The spiriferoid brachiopods also suggest a correlation with higher parts of the Alapah limestone, although nothing diagnostic occurs in these collections. Sadlerochit Formation The collections from the Sadlerochit formation contain elements of the Permian brachiopod fauna found in many places in northeastern Alaska. The age is late Early Permian or early Late Permian. |