Chalk Biozone 4 - Litosphaeridium siphoniphorum
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).