The cretaceous flora of the Kuk-Kaolak area, northern Alaska

Among restudied floras from the Kuk-Kaolak area, three taphofloras are defined. The "lower" one from members 1-4 including the Karmak and Kungok floras and the lower subassemblage of the Kuk flora (Smiley, 1966) is dated back to the middle-early late Albian. The "middle" taphoflora from members 5 and 6 comprising the upper Kuk subassemblage after Smiley and Ketik flora is of the late Albian-Cenomanian age, and the "upper" Turonian flora from Member 7 corresponds to the Smiley's Kaolak flora. The taxonomic composition and ages of above taphofloras suggest that Cretaceous floras from the Kuk-Kaolak area developed gradually and successively. Paleobotanic data disprove the former idea of stratigraphic hiatuses in the section (Smiley, 1972a). Cretaceous sedimentation in the Kuk-Kaolak area terminated in the Turonian but not in the Maastrichtian as was previously believed. Members 1, 2-6, and 7 can be considered as lithological analogues of the Tuktu, Chandler, and Seabee formations, respectively, of the Umiat-Chandler and Sagavanirktok areas of northern Alaska. Younger subdivisions known in the last two areas (Prince Creek, Schrader Bluff, and Sagavanirktok formations) have no analogues in the Kuk-Kaolak area. Lithological members 1-6 of the Kuk-Kaolak area are correlative with the Kukpowruk and Corwin formations in the Utukok-Corwin area, where younger Cretaceous sediments are missing. During the Albian-Paleogene time, geological settings changed gradually and irreversibly so that marine sedimentation and sedimentation in general terminated later in easterly areas of the subregion than in western areas of northern Alaska.