Chalk Group Lithostratigraphy: Northern England - Burnham Chalk Formation

The Burnham Chalk is characterised by the occurrence of common, predominantly tabular flints and thin-bedded (so called 'laminate') chalk with marl seams (Gaunt et al., 1992). The formation is 138-140 m thick, and according to Whitham (1991) is softer than the underlying Welton Chalk, although Wood & Smith (1978) stated the opposite. Several laterally continuous bands of indurated chalk occur in the Burnham Formation and produce a mappable feature where they are developed below the Ulceby Marl, although no hardgrounds are recorded (Gaunt et al., 1992).

The mostly tabular flints vary from 10-300 mm thick and may be solid or carious (Gaunt et al., 1992). Nodular burrow-form flints are uncommon, but Paramoudra flints occur at some levels, particularly towards the base (Gaunt et al., 1992). The horizons of thin-bedded chalk comprise marl-coated bedding planes (commonly stylilotised; personal observation) a few mm apart that are valuable for long-range correlation (Gaunt et al., 1992). The main seams of marl range up to 50mm, and locally up to 110 mm, and the more important are named and form a useful framework for correlation (Gaunt et al., 1992).

The fauna of the Burnham Chalk is more abundant and diverse than the underlying Welton Chalk, comprising in the lower part of the succession common echinoids (Sternotaxis and Infulaster), brachiopods (Orbirhynchia and Terebratulina lata) and inoceramid bivalves (Inoceramus ex gr. inaequivalvis & I. lamarcki stuemckei) (Gaunt et al., 1992). Slightly higher in the succession the dominant echinoids are Micraster and Sternotaxis, and there are local representatives of the Reussianum Fauna found in southern England (including the ammonite Hyphantoceras reussianum) (Gaunt et al., 1992). Above this are acmes of Pycnodonteine oysters and beds with the trace fossil Zoophycos, associated with the bivalves Didymotis and Cremnoceramus, overlain by further records of Cremnoceramus and the echinoids Micraster normanniae and M. buccaillei. (Gaunt et al., 1992). Towards the top of the succession the fauna is dominated by inoceramid bivalves, particularly Volviceramus and Platyceramus (Gaunt et al., 1992), and the highest beds are sponge-rich (Whitham, 1991).

The base of the Burnham Chalk is the bedding plane below the Ravendale Flint, and the top is the top of the flinty chalk (Gaunt et al., 1992). Whitham (1991) named the highest flint the High Stacks Flint, after High Stacks [TA 258 704], Flamborough Head, where Wood & Smith (1978) reported the horizon to occur.

The key named marker beds in the Burnham Chalk are as follows (many more flints and marls occur than those shown):

DIAGRAM HERE

Macrofossil Biozonation: S. plana Zone, M. cortestudinarium Zone, M. coranguinum Zone (pars) (= lower Hagenowia rostrara Zone of Whitham, 1991)

Correlation: see Correlation with other UK Chalk Group successions

References

GAUNT, G D, FLETCHER, T P & WOOD, C J. 1992. Geology of the country around Kingston-upon-Hull and Brigg. Memoir of the British Geological Survey.

WHITHAM, F.1991. The stratigraphy of the Upper Cretaceous Ferriby, Welton and Burnham formations north of the Humber, north-east England. Proceedings of the Yorkshire Geological Society, Vol. 48(3), 227-255.

WOOD C J & SMITH, E G.1978. Lithostratigraphical classification of the Chalk in North Yorkshire, Humberside and Lincolnshire. Proceedings of the Yorkshire Geological Society, Vol. 42(2), 263-287.

See: flint, marl, stylolite, Reussianum Fauna