Chalk Biozone 20 - Tectatodinium rugulatum

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Age: Late Danian.

Correlations: No macrofaunal correlation. Chalk Biozone 20 correlates with the calcareous nannofossil zones lower NP4 of Martini (1971) and planktonic foraminiferal sub-biozone P1C of Blow (1969) and Berggren (1972). Furthermore, the interval equates with the D2 dinoflagellate cyst biozone of Costa & Manum (1988) and the upper Scr and lower Cst dinoflagellate cyst Interval biozones of Powell (1992).

Definition: The interval between the LAD of Senoniasphaera inornata to the LAD of Tectatodinium rugulatum and/or the top of the Ekofisk Formation (the Ekofisk Formation/Maureen Formation transition in the North Sea).

Comments: This, the youngest of the Chalk Group dinoflagellate cyst biozones represents the uppermost Ekofisk Formation of the North Sea (Knox & Holloway, 1992), above the LAD of Senoniasphaera inornata. The LAD of Tectatodinium rugulatum marks the top of this biozone (Hansen, 1977; Powell, 1992)

Lithostratigraphical correlation: The Ekofisk Formation (North Sea).