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updated to follow: Stratigraphic Guide to the Cromer Knoll, Shetland and Chalk Groups of the North Sea and Norwegian Sea. Felix M. Gradstein & Colin C. Waters (editors), Mike Charnock, Dirk Munsterman, Michelle Hollerbach, Harald Brunstad, Øyvind Hammer & Luis Vergara (contributors). Newsletter on Stratigraphy, vol 49/1 pp71-280, 2016
The term Lamplugh Formation was introduced for a unit of argillaceous, chert-bearing, chalky limestones which underlie harder relatively chert-free chalks of the Jukes Formation and overlie hard, chalky limestones of the Herring Formation (Lott & Knox, 1994; Table).
After the eminent geologist G.W. Lamplugh (1859В1926) who carried out detailed studies of the Cretaceous successions in Yorkshire in the late 19th century.
The Lamplugh Formation consists of chalky limestones which are typically white to grey, soft to moderately hard, commonly argillaceous and characteristically chert-bearing. The presence of chert (flint) bands throughout the unit is a characteristic feature (Lott & Knox, 1994).
The Lamplugh Formation ranges up to 200 m (e.g. well 49/25-1), but may vary in thickness due to intra-basinal tectonic controls and post-Cretaceous erosion.
The Flounder Formation is confined to the southern part of the South Viking Graben and the extreme north of the Central North Sea.
38/24-1: 1585.5В1670.5 m (5202В5481 ft) |
Lat. 55° 12’ 35.3”N Lat. 54° 45’11.3”NВ В В В Lat. 53° 52’ 05.0”N |
Long. 02° 37’ 33.1”E Long. 1° 33’07.8”E Long. 02° 49’ 04.0”E |
The upper boundary of the Lamplugh Formation is marked by a downward change from the chalky limestones of the Jukes Formation into harder, more argillaceous chalks (Lott & Knox, 1994).
The top of the Lamplugh Formation is marked by a sharp downward increase in velocity accompanied in some sections by a slight increase in gamma-ray values e.g.В 49/24-1. In some wells the mid-part of the Lamplugh Formation is particularly argillaceous (e.g. well 42/29-C01 Panel 1; 53/4-2 Panel 2, Lott & Knox, 1994) giving the log profiles a 'waisted' appearance. At the base of the formation there is a corresponding downhole decrease in gamma ray and increase in sonic velocity responses (Lott & Knox, 1994).
The FDO of Stensioeina granulata granulata marks the top of the formation and two intraformational biomarkers are S. granulata levis and S. granulata kelleri. Palynomorph recovery in the Lamplugh Formation is generally relatively low.
The Lamplugh Formation passes northwards into the lower part of the Mackerel Formation of the Central North Sea (Table). Onshore, in eastern England the formation equates largely with the Burnham Chalk Formation of Wood & Smith (1978; refer also to Whitham, 1991).
The chalky limestones of the Lamplugh Formation were deposited in an open marine setting as pelagic carbonates and consist primarily of fine bioclastic skeletal debris (dominated by coccolith plates). Terriginous clay is present as thin beds and seams (Lott & Knox, 1994).
None in UK waters.