Cyclicargolithus abisectus


Ancestry: Coccolithophores -> Isochrysidales -> Noelaerhabdaceae -> Reticulofenestra -> C. floridanus group -> Cyclicargolithus abisectus
Sister taxa: C. abisectus, C. artuziae, C. floridanus, C. luminis, C. parvus, R. westerholdii, C. sp.,

Short diagnosis: Coccoliths large (>11µm), usually sub-circular.


Taxonomy:

Citation: Cyclicargolithus abisectus (Muller, 1970) Wise, 1973
Rank: Species
Basionym: Coccolithus? abisectus Muller, 1970
Notes & discussion: The distinction from C. floridanus on size is arbitrary, but of some biostratigraphic use (Olafsson, 1992)

Farinacci & Howe catalog pages: Coccolithus abisectus *

Short diagnosis: Coccoliths large (>11µm), usually sub-circular.

Geological Range:
Notes: Varol (1998) used the FO of C. bisectus as a sub-zonal marker within his North Sea zonation, occurring about 2/3 of the way through NP23.
Last occurrence (top): within NN1 zone (22.82-23.13Ma, top in Aquitanian stage). Data source: Young 1998
First occurrence (base): within NP23 zone (29.62-32.02Ma, base in Rupelian stage). Data source: Varol (1998)

Plot of occurrence data:

References:

Müller, C., (1970). Nannoplankton aus dem Mittel-Oligozän von Norddeutschland und Belgien. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, 135: 82-101.

Varol, O., (1998). Palaeogene. In: Bown, P.R. (Editor), Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publications Series. Chapman & Hall, London, pp. 200-224.

Wise, S.W., (1973). Calcareous nannofossils from cores recovered during Leg 18, Deep Sea Drilling Project: biostratigraphy and observations on diagenesis. Initial Reports of the Deep Sea Drilling Project, 18: 569-615.

Young, J.R., (1998). Neogene. In: Bown, P.R. (Editor), Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publications Series. Chapman & Hall, London, pp. 225-265.


Nannotax3 - Coccolithophores - Cyclicargolithus abisectus by: Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 26-3-2017

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Richard Denne (Marathon Oil, Houston, US)
I've always felt that the thicker collar and somewhat more elliptical opening of C. abisectus was a better way to differentiate it from C. floridanus than size. There is a large form (>13 microns) with a very thick collar that is found in frequent abundances within the lower NP25 that makes a relatively good assemblage marker (see photo of large Cyclicargolithus abisectus in the Noelaerhabdaceae gallery).
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