Chalk Group Lithostratigraphy: Southern North Sea (UK Sector) - Ekofisk Formation

The following details are based on the account of Lott & Knox (1994).

The Ekofisk Formation, up to 55 m thick, but more typically 10-30 m thick, is sporadically developed in the Southern North Sea. It comprises fine-grained and compact chalky limestones, typically without flint.

The top of the formation is lithologically marked by a downward change from mudstone to chalky limestone, corresponding with a sharp downward decrease in gamma log values and increase in sonic velocity.

The lower boundary is lithologically defined by a downward change from poorly flinty chalky limestone to flinty and less argillaceous chalky limestone. Geophysically, the boundary is most easily defined by a downward reduction in gamma log values.

Age: Early Paleocene (Danian)

Biozonation:

Dinoflagellates: equates with BGS biozones 19-20

References

LOTT, G K & KNOX, R W O'B. 1994. Post-Triassic of the Southern North Sea. In: KNOX, R W O'B & CORDEY, W G. (eds) Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham.