Chalk Biozone 19 - Senoniasphaera inornata

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Age: Early to mid Danian.

Correlations: No macrofaunal correlation. Chalk Biozone 19 correlates with the calcareous nannofossil zones NP1 to lowermost NP4 of Martini (1971) and planktonic foraminiferal sub-biozones P1A to lower P1C of Blow (1969) and Berggren (1972). Furthermore, the interval equates with the D1 and lower D2 dinoflagellate cyst biozones of Costa & Manum (1988) and the Cco to lower Scr dinoflagellate cyst Interval biozones of Powell (1992).

Definition: The interval between the LAD of Palynodinium grallator and the LAD of Senoniasphaera inornata.

Comments: The LAD of Senoniasphaera inornata is a reliable marker for the late Danian (Hultberg, 1986; Harland et al., 1992; Powell, 1992; Wilkinson et al., 1993; Williams, Brinkhuis et al., 1998; Brinkhuis et al., 2000). The species has a relatively short range, its FAD lies in the late Maastrichtian (Hansen, 1977). The FADS of Alisocysta reticulata, Hafniasphaera septata, Tectatodinium rugulatum and Xenicodinium lubricum are present within this biozone (Hansen, 1977; Herngreen et al., 1986; Hultberg, 1986; Powell, 1992; Habib et al., 1996; Williams, Brinkhuis et al., 1998). Other dinoflagellate cyst datums within this biozone are the LADS of Carpatella cornuta, Cyclonephelium? castelcasiense, Hafniasphaera hyalospinosa and Spongodinium delitiense (see Powell, 1992; Williams, Brinkhuis et al., 1998).

Lithostratigraphical correlation: The Ekofisk Formation (North Sea).