Research-paper
Eocene microphytofossils (dinoflagellate cysts and continental palynomorphs) of Northwestern Siberia (Severnaya Sosva Basin)
Iakovleva, Alina I.; Kulkova, Inessa A.; Cavagnetto, Carla
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Abstract
A palynological study (dinoflagellates and pollen grains) was carried out in two boreholes through the Eocene of the Severnaya Sosva River Basin in the north of Western Siberia. Five zones were identified: two (Dracodinium varielongitudum and Charlesdowniea coleothrypta zones) in the Ypresian, and three (Rhombodinium draco, Rhombodinium porosum and Kisselevia ornata zones) in the Bartonian. The absence of the dinoflagellate zones characterizing the Lutetian in other regions suggests an interruption in marine sedimentation in Northwestern Siberia during the beginning of the Middle Eocene. A palaeoecological interpretation of some dinoflagellate groups was proposed. It shows a shallow marine environment with a reduced salinity, followed by a marine basin regression during the Bartonian. For the first time the ecology of the acritarch genera Paucilobimorpha and Tritonites was interpreted.