International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Oligocene dinoflagellate cysts from the North Alpine Foreland Basin: new data from the Eggerding Formation (Austria)

Pages: 49 - 70

Authors: ALI SOLIMAN

Abstract: In spite of detailed geological and geophysical investigations, information available on palynostratigraphy for the successions deposited in the Austrian part of the North Alpine Foreland Basin (NAFB) is scanty. For the first time, relatively diverse and well preserved Oligocene dinocyst assemblages, comprising 53 genera and 138 species, are presented from the organic-rich sediments of the Eggerding Formation. These assemblages contribute to the biostratigraphy of the Oligocene deposits within the NAFB. Dinocysts such as Chiropteridium lobospinosum, Membranophoridium aspinatum, Cordosphaeridium spp., Enneadocysta spp., Deflandrea spp., Spiniferites/Achomosphaera group, Hystrichokolpoma spp., Apteodinium spp., Glaphyrocysta/Areoligera complex and Wetzeliella spp. represent the main palynological elements. The occurrence of Chiropteridium spp., Tuberculodinium vancampoae, Distatodinium biffii and Wetzeliella gochtii is of particular importance for regional correlations within the Lower Oligocene sediments. A comparison with age-controlled assemblages from the North Sea Basin, Carpathian and circum-Mediterranean regions substantiate the attribution to the Rupelian. Lack or sporadic occurrence of the oceanic taxa (e.g. Nematosphaeropsis and Impagidinium) and dominance of Glaphyrocysta/Areoligera indicate an inner-neritic marine setting during the deposition of the studied intervals. Although, it is difficult to reconstruct precisely the climatic conditions based on the recorded dinocysts, warm? sea surface water is suggested. A variation in salinities is interpreted based on the abundances of Homotryblium spp. The abundance of Peridiniaceae taxa (e.g. Lejeunecysta, Wetzeliella, and Deflandrea) indicates nutrient-rich surface water.

Keywords: Oligocene, Austria, North Alpine Foreland Basin, Eggerding Formation, paleoenvironment, dinocysts

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