Biostratigraphy of the Lower Cretaceous sediments based on the study of calcareous nannofossils (Outer Flysch, Western Carpathians, Czech Republic)


Lilian Švábenická

Geoscience Research Reports 41, 2008 (GRR for 2007), pages 63–72

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Calcareous nannofossils of the Lower Cretaceous age have been found in the black pelites that form isolated fissure fillings in the tectonically deformed Jurassic limestones. Assemblages are characterized by high number or even dominance of Watznaueria barnesae and by the presence of low latitude/Tethyan species, such as Speetonia colligata, Cruciellipsis cuvillieri, Calcicalathina oblongata, Conusphaera rothii, Micrantholithus obtusus, M. hoschulzii, nannoconids, etc. Repeated input of boreal (Micrantholithus speetonensis, Nannoconus inornatus, N. abundans) or bipolar (Sollasites horticus, Crucibiscutum salebrosum, Seribiscutum primitivum, and Tegulalithus septentrionalis) high-latitude taxa has been recorded in the Lower Valanginian and during the Hauterivian. Moreover, episodic occurrence of nannoconids was observed in the interval from the Lower Berriasian to the lower Upper Hauterivian. Nannoconids usually indicate warm epicontinental sea and oligotrophic waters with minor input of terrigenous material. The scarce presence of high-latitude nannoflora during Valanginian-Hauterivian reflects the occasional influence of Boreal province in the depositional area of NW part of Tethys, nowadays Silesian Unit, Outer group of nappes, Western Carpathians.