Early and middle Eocene dinoflagellate cysts from the Aktulagay section, Kazakhstan

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A mid neritic-upper bathyal Ypresian section at Aktulagay, western Kazakhstan, has been analyzed palynologically. A number of key dinoflagellate cyst events are directly calibrated with published calcareous nannofossil data from the same section. The events are used to identify eight dinoflagellate cyst zones from a recently established zonation, used elsewhere in the eastern Peri-Tethys, and to calibrate these zones with the standard nannofossil zonation (NP zones). The events include the lowermost occurrences of Deflandrea oebisfeldensis (∼1%), Dracodinium simile, Eatonicysta ursulae, Dracodinium varielongitudum, Charlesdowniea coleothrypta, Ochetodinium romanum, Charlesdowniea columna, Samlandia chlamydophora, Areosphaeridium diktyoplokum, and Wetzeliella eocaenica. An important regional unconformity separates the Ypresian section from overlying non-calcareous strata with the age-diagnostic species Enneadocysta arcuata, Wetzeliella ovalis, Wilsonidium echinosuturatum, and Rhombodinium draco, indicating the Rhombodinium draco Zone of latest Lutetian–Bartonian age. Based on fluctuations of ecological groups of dinoflagellate cysts, a series of different depositional environments are interpreted and related to the existing sequence stratigraphic model of the section. In most cases dinoflagellate cyst agree with, or supplement, calcareous micro- and nannofossil indications, and support the sequence stratigraphic model. Impagidinium wardii sp. nov. is atypical for the otherwise oceanic genus as it bloomed in a mid-neritic environment. The first cooling at the end of the Early Eocene Climatic Optimum (EECO) is suggested to have caused a strong acme of Eatonicysta ursulae and distinct lowering of the sea level in the NP13 zone. Four new species are formally described: Cribroperidinium cavagnettiae sp. nov., Dracodinium robertknoxii sp. nov., Impagidinium wardii sp. nov., and Samlandia chriskingii sp. nov. The Aktulagay Formation of King et al. (2013) is renamed the Kulsary Formation.

OriginalsprogEngelsk
TidsskriftPalynology
Antal sider31
ISSN0191-6122
DOI
StatusE-pub ahead of print - jan. 2020

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