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This report covers 9 collections that are definitely Mississippian; three represent the dark facies of the Lisburne (probably Kuna Formation). In addition, 2 collections consisting of slightly calcareous ironstone concretions seem to be about the same age and may represent a special facies of the Kuna. Contrary to the impression given by Mull et al (1983), many collections from beds now assigned to the Kuna in the central Brooks Range contain a distinctive megafauna which, in many places, is either late Meramecian or earliest Chesterian in age. Most of the goniatites described by Gordon (1957) came from beds now assigned to the Kuna. Several outcrops on the Kiruktagiak River, northwest of Chandler Lake, yield goniatites of the GONIATITES AMERICANUS Zone (identified by Gordon in 1957 as G. CRENISTEA) which is late Meramecian. By correlation eastward, this level is equivalent to the black chert-shale member of the Alapah Limestone of Bowsher and Dutro (1957). Westward, where the Kuna encompasses all of the Lisburne Group, older beds are encountered. In the Etivluk Valley, both the GONIATITES Zone and the next older BEYRICHOCERAS ZONE goniatites are found. The BEYRICHOCERAS Zone is a lower Meramecian equivalent. In the Kiligwa River headwaters, four zones are represented: the previous two plus two older zones, the AMMONELLIPSITES and MUESTEROCERAS Zones, middle and lower Osagean equivalents, respectively. In the central Brooks Range, the GONIATITES Zone assemblage includes a characteristic brachiopod-pelecypod fauna which is found more widely than the cephalopods themselves. It is this shelly fauna that appears in the Kuna collections of this shipment. Four collections are from rocks of the Lisburne Group, all possibly from the Alapah Limestone. Three of these contain corals and will be reported on separately by W.J. Sando (field nos. 83AMu26, 83AMu77, and 83AKa7-6). The fourth collection (83AMu84-4) contains only fenestrate bryozoans that are like similar forms from the Alapah Limestone elsewhere in the central Brooks Range and are probably of Late Mississippian age. REFERENCES - Bowsher, A.L., and Dutro, J.T., Jr., 1957, The Paleozoic section in the Shainin Lake area, central Brooks Range, Alaska: U.S. Geol. Survey Prof. Paper 303-A. Gordon, M., Jr., 1957, Mississippian cephalopods of northern and eastern Alaska: U.S. Geol. Survey Prof. Paper 283. Mull, C.G. and others, 1982, New Upper Paleozoic and Lower Mesozoic stratigraphic units, central and western Brooks Range, Alaska: Amer. Assoc. Petrol. Geol. Bull., v. 66, no. 3, p. 348-362. |