Chalk Group Lithostratigraphy: Marlborough Downs/Berkshire Downs/Chilterns - Totternhoe Stone

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The Totternhoe Stone, named after the village of Totternhoe near Dunstable, Bedfordshire, where the stone is still worked in local quarries, is a brownish-grey, bioclastic calcarenite, with an erosive base (Wood, 1996). It is characterised by comminuted inoceramid shell fragments, and typically has a basal lag of glauconitised and phosphatised pebbles (Wood, 1996). The Totternhoe Stone is thickest where the channels cut in the underlying Chalk Marl are greatest, and reaches c. 6.5 m at Totternhoe, but elsewhere is generally 1.5 - 3 m thick (Hopson et al., 1996). Apart from inoceramid shell, the Totternhoe Stone contains a fauna of brachiopods, other bivalves (especially Entolium orbiculare and Oxytoma seminudum) and ammonites that show the bed to represent a condensation of several horizons equating with the higher part of the Chalk Marl of the Southern Region.

Macrofossil Biozonation: A. rhotomagense Zone (Shephard-Thorn et al., 1994; Wood, 1996)

Correlation: see Correlation with other parts of the UK

References[edit]

HOPSON, P. M., ALDISS, D. T. & SMITH, A. 1996. Geology of the country around Hitchin. Memoir of the British Geological Survey, Sheet 221 (England & Wales).

SHEPHARD-THORN. E. R., MOORLOCK, B. S. P., COX, B. M., ALLSOP, J. M. & WOOD, C. J. 1994. Geology of the country around Leighton Buzzard. Memoir of the British Geological Survey, Sheet 220 (England & Wales).

WOOD, C. J. 1996. Upper Cretaceous: the Chalk Group. In SUMBLER, M. G., British Regional Geology: London and the Thames Valley. Fourth Edition. (London: HMSO for the British Geological Survey).

See: Chalk Marl (Chilterns and adjoining areas), Chalk Marl (Southern Region)