科研之友
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摘要
Albian-Cenomanian grey-green marl succession crops out at several restricted outcrops north of Rabisha mound in Northwest Bulgaria. The continuous sequence near Tolovitsa karst spring is characterised by calcareous nannofossils and dinoflagellate cysts. It is subdivided in two nannofossil zones: Eiffellithus turriseiffelii and Lithraphidites acutum. The former is subdivided in two subzones: Prediscosphaera columnata and Prediscosphaera cretacea. The boundary between them is used to define the Albian-Cenomanian boundary. Thus, the present study demonstrates the higher stratigraphic potential of this event for the Albian-Cenomanian boundary, and provides a new reliable datum for its identification. Dinoflagellate cyst assemblages indicate the Litosphaeridium siphoniphorum dinocyst zone. The concurrent presence of L. siphoniphorum, E. spinosa, X. alatum, P. infusorioides, P. cingulatum and O. costata allows correlation to its lower part and confirms again a latest Albian - earliest Cenomanian age for the studied interval. High amounts of granular amorphous organic matter (AOM), together with sharp increase in dinocyst abundance in the lowermost part of the section could be considered to indicate the well-documented global latest Albian ocean anoxic event (OAE 1d).
- 出版日期2014
