M. G. Moiseeva

Flora development in Northeastern Asia and Northern Alaska during the Cretaceous-Paleogene transitional epoch

Study of floral succession from the Cretaceous-Paleogene boundary interval in Russian Far East (Zeya-Bureya depression), Northeastern Russia (Koryak Upland), and Northern Alaska (Sagavanirktok River basin) is crucial for better understanding palaeoclimatic and palaeogeographic factors, which controlled events in vegetation evolution at that time. The succession of fossil floras in the Zeya-Bureya depression includes plant assemblages of the Santonian, Campanian, early Danian, Danian, and Danian-Selandian age. The early Danian Boguchan Flora keeps continuity in composition and dominating taxa with the Campanian Late Kundur Flora. The Koryak Flora of the Amaam Lagoon area (Northeastern Russia) is dated as late Maastrichtian based on correlation of plant-bearing beds with marine biostratigraphy, whereas the Early and Late Sagwon floras of Northern Alaska are dated back to the Danian-Selandian and early Paleocene based on palynological and macrofloristic data. The Early Sagwon Flora is most close to the late Maastrichtian Koryak Flora of the Amaam Lagoon area in composition and main dominants, while the Late Sagwon Flora is comparable with the Danian or Danian-(?) Selandian flora from the Upper Tsagayan Subformation of the Amur area. In a florogenic aspect, trans-Beringian plant migrations from northeastern Asia and southern palaeolatitudes of the Far East, which became possible due to Paleocene climate warming in Arctic, have played an important role in forming of the Paleocene floras of Northern Alaska. Floras of the Far East and high latitudes of Asia and North America show no evidence of catastrophic event at the Cretaceous-Paleogene boundary. Their development was most probably controlled by climate changes, plant evolution and migration.

Late paleocene flora of the northern Alaska Peninsula: the role of transberingian plant migrations and climatic change

For the first time, the Late Sagwon Flora is described from the upper beds of the Prince Creek Formation (Upper Paleocene) at the Sagavanirktok River (northern Alaska Peninsula). The flora is dominated by the angiosperm Tiliaephyllum brooksense Moiseeva et Herman sp. nov. and conifer Metasequoia occidentalis (Newb.) Chaney. The Late Sagwon Flora is most similar to the Danian or Danian-Selandian flora from the middle part of the Upper Tsagayan Subformation (Amur Region) and lower part of the Wuyun Formation (Heilongjiang Province, China). This similarity allows us to hypothesize that the genus Tiliaephyllum, which dominated in the Late Tsagayan Flora, migrated via the Bering Land Bridge from southern paleolatitudes of the Far East to high latitudes of the Arctic Pacific, due to the progressively warming climate of the Paleocene. Additional new angiosperm species are described from the Late Sagwon Flora: Archeampelos mullii Moiseeva et Herman sp. nov., Tiliaephyllum brooksense Moiseeva et Herman sp. nov., and Dicotylophyllum sagwonicum Moiseeva et Herman sp. nov.

New angiosperms from the Maastrichtian of the Amaam Lagoon area (northeastern Russia)

New angiosperm taxa from the Koryak Formation of the Amaam Lagoon area (northeastern Russia) are described. Amaamia Moiseeva, with the type species A. tshucotica (Golovn.) Moiseeva, comb. nov., is substantiated as a new genus of the morphological system of dispersed angiosperm leaves. Rarytkinia amaamensis Moiseeva, sp. nov. is described. Members of Corylites Gardner (1887) ex Seward et Holttum (1924) are characterized by a broad morphological variability, which makes their specific diagnosis difficult. An extended diagnosis of this genus and the description of Corylites beringianus (Krysht.) Moiseeva, comb. nov. are presented. Ettingshausenia raynoldsii (Newb.) Moiseeva, comb. nov. is proposed for fossil leaves traditionally assigned to the genus Platanus.

New data on the composition and age of the Ust’-Emuneret flora from the Enmyvaam River basin (Central Chukotka)

The Ust’-Emuneret floristic assemblage from the Emuneret Formation developed in the Enmyvaam River basin (Okhotsk-Chukotka volcanogenic belt) is described. The age of flora-bearing deposits is debatable, being previously determined in the interval of the Cenomanian to Campanian. According to the new data, the assemblage includes 57 species of fossil plants with dominant angiosperms, subdominant conifers, and subordinate ferns, liverworts, ginkgoaleans, and czekanowskialeans. The Ust’-Emuneret flora is characterized by the presence of advanced forms among different plant groups, which occur in Santonian-Campanian and younger floras of northeastern Russia, and by the presence of relict ginkgoaleans and czekanowskialeans. The flora is compared with other floras from neighboring regions, which provides grounds for the inference on its most probable Late Santonian age (probably, including the Early Santonian and initial Campanian).

The Maastrichtian flora of the Amaam Lagoon area (Northeastern Russia)

The Maastrichtian Koryak flora from the Amaam Lagoon area is comprehensively studied with reference to available data on the stratigraphy of the study area and age assessment of the flora-bearing deposits. In the Koryak flora 32 species of plant fossils are identified and systematically described in the work. The established traits of the Koryak floristic assemblage are used to correlate it with the other assemblages close in age from different localities of Northeastern RNortheastern Russiaussia and Alaska. The results of correlation and taxonomic revision of plant fossils from the upper part of the Prince Creek Formation, Northern Alaska show that in the Anadyr-Koryak and Northern Alaska circum-Pacific regions the Koryak stage of flora development and the respective phytostratigraphic horizon (upper Maastrichtian-Selandian), of key significance for interregional correlation of continental deposits, are distinguishable. Floristic changes recorded in the northern circum-Pacific regions across the Cretaceous-Paleogene boundary suggest that the evolution of vegetation was gradual, controlled by climatic change, evolutionary factors and plant migration. These results are inconsistent with the postulated global significance of the ecological crisis at that time.

New Data on the Cenomanian Flora of the Ugol'naya Bay (Northeastern Russia)

The taxonomic composition of the Middle Ginter Flora of the Ugol’naya Bay area (northeastern Russia) is supplemented with new data based on newly determined and revised materials. The uniqueness of the flora lies in the fact that its age (Middle Cenomanian) is dated to a zone by marine fauna. The floristic assemblage contains 29 species of fossil plants and is dominated by angiosperms and conifers. The refined taxonomic list shows even greater than was earlier supposed similarity of the flora to the Grebenka assemblage from the Krivorechenskaya Formation at the left bank of the Anadyr River, which is the type assemblage of the Grebenka phase of the flora development in northeastern Russia. A new combination is proposed: Ettingshausenia louravetlanica (Herman et Shczepetov) Herman et Moiseeva, comb. nov.

New angiosperms from the Late Cretaceous Ust’-Emuneret flora of central Chukotka

New angiosperms from the Emuneret Formation of the Enmyvaam River basin are described: Menispermites lebedevii sp. nov., Cissites reticulatus sp. nov., Viburniphyllum emuneretum sp. nov., and Dicotylophyllum stipulare sp. nov. These species are characteristic elements of the Ust’-Emuneret floristic assemblage, which occur from the volcanogenic deposits of the late stage of the development of Okhotsk-Chukotka volcanogenic belt. The floristic assemblage includes 57 species of fossil plants. It is characterized by dominant angiosperms, subdominant conifers, and subordinate ferns, liverworts, ginkgoaleans, and czekanowskialeans. Macrofloristic study indicates the Santonian-Early Campanian age of plant-bearing deposits.

New species of the genus Macclintockia (Angiosperms) from the Campanian of the Ugol’naya Bay (Northeastern Russia)

New species of angiosperms are described as members of the genus Macclintockia from the Ugol’naya Bay area, in northeastern Russia: M. barykovensis Moiseeva, sp. nov., M. gigantea Moiseeva, sp. nov., and M. terranea Moiseeva et Herman, sp. nov. Leaves of this genus are considerably variable, which hampers differentiation between particular species. The study of new material has allowed the author to trace the morphological variability of these species and revised on this ground the composition of the species M. ochotica Vachr. et Herman and M. beringiana Herman. The composition of Macclintockia is discussed, as well as its occurrence during the Late Cretaceous.

The Koryak phase of the Flora development in the Northern Pacific frame

The Koryak phase of the floristic development in the Northern Pacific frame is discussed. Newly obtained data on the Koryak Flora from the Amaam Lagoon area (Northeastern Russia) and Paleocene floras of the Northern Alaska have extended geographic and temporal ranges of the phase. Interregional statuses of the Koryak phase and phytostratigraphic horizon based on this phase, which is traced over the entire Northern Pacific frame and not just the Anadyr-Koryak region as was earlier supposed, are substantiated. The upper boundary of this horizon is defined; the age ranges from the Late Maastrichtian-Danian to Early Selandian.

Growing conditions of the Ust’-Emuneret flora and the Santonian-Campanian climate of Chukotka

New data on climatic conditions of the Ust’-Emuneret flora growth in the Enmyvaam River basin, Okhotsk-Chukotka volcanic belt, are reported. A great diversity of woody dicot leaves in the studied flora permits for the first time for this region the reconstruction of quantitative paleoclimatic parameters using the CLAMP analysis. On the basis of the available results, the Santonian-Campanian climate of the northern Okhotsk-Chukotka volcanic belt and the adjacent Anadyr-Koryak region is analyzed.