Chalk Biozone 4 - Litosphaeridium siphoniphorum

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Age: Earliest Turonian.

Macrofaunal correlation: The W. devonense and F. catinus zones (= the W. coloradoense Zone.

Definition: The interval between the LAD of Wrevittia cassidata to the LAD of Litosphaeridium siphoniphorum.

Comments: The distinctive species Litosphaeridium siphoniphorum apparently became extinct close to the Cenomanian-Turonian boundary (Costa & Davey, 1992; Foucher & Monteil, 1998). An alternative marker for the top of this Biozone is the FAD of Florentinia clavigera (see Foucher & Monteil, 1998).

Lithostratigraphical correlation: The lower Holywell Nodular Chalk Formation (Southern Province), the Welton Chalk Formation (Northern Province) and the Herring Formation (North Sea).