The BGS Lexicon of Named Rock Units — Result Details
Glauconitic Marl Member
| Computer Code: | GLML | Preferred Map Code: | GM |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Cenomanian Age (KE) — Cenomanian Age (KE) | ||
| Lithological Description: | Calcareous glauconitic sand and glauconitic sandy silty chalk with phosphatic nodules. | ||
| Definition of Lower Boundary: | The lower boundary is taken at the base of glauconite-rich sand or clay resting disconformably, at a strongly burrowed surface, on pale grey siltstones of the Upper Greensand (or grey mudstones of the Gault), which contain only a trace of glauconite at the most. Note: bioturbation may carry glauconitic sediment down into the underlying formation. | ||
| Definition of Upper Boundary: | The upper boundary is taken at the upwards cessation of sand and/or abundant glauconitic grains (and phosphatic pebbles) (can occur as a rapid transition over 10 cm or less) into grey, sparsely glauconitic chalky marl or marly chalk, comprising the rest of the West Melbury Marly Chalk Formation. | ||
| Thickness: | 2 to 4 m throughout much of the Southern Province, might be only a few tenths of a metre elsewhere over synsedimentary structural highs. Up to 5 m in Kent and at Eastbourne, East Sussex. | ||
| Geographical Limits: | Known throughout much of the Southern Province in Kent, Surrey, Sussex, Hampshire and Berkshire. | ||
| Parent Unit: | West Melbury Marly Chalk Formation (WMCH) | ||
| Previous Name(s): | Basement Bed [Obsolete Name and Code: Use GLML]
(-2828)
Chloritic Marl [Obsolete Name and Code: Use BRHD, CBG, GLML] (-4494) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Reference Section | Isle of Wight: coastal section, Compton Bay. The erosive contact between the Upper Greensand Formation and the member is generally well exposed just west of a small headland. The beds here dip at 45 degrees to the north. | ||
| Type Section | East Wear Bay, Kent. Member overlies the Gault Formation in the cliffs below Abbots Point at the eastern end of the bay where up to 7 m of glauconite-rich marl attributable to the member rests on a burrowed surface in dark grey clays of the Gault. | ||
| Reference Section | North Downs: coastal section at Copt Point. Exposure of Gault Formation overlain by the member visible in the cliffs which is also the boundary stratotype for the East Wear Bay Chalk Formation of Robinson (1986) and its partial correlative the West Melbury Marly Chalk Formation. | ||
| Reference(s): | |||
| Kennedy, W J. 1970. A correlation of the uppermost Albian and the Cenomanian of South-West England. Proceedings of the Geologists' Association, Vol.81, 613-677. | |||
| Young, B and Lake, R D. 1988. Geology of the country around Brighton and Worthing. Memoir of the British Geological Survey, Sheet 318 and 333 (England and Wales). | |||
| Robinson, N D. 1986. Lithostratigraphy of the Chalk Group of the North Downs, south-east England. Proceedings of the Geologists' Association, Vol.97(2), 141-170. | |||
| Hopson, P M. 2005. A stratigraphical framework for the Upper Cretaceous Chalk of England and Scotland, with statements on the Chalk of Northern Ireland and the UK Offshore Sector. British Geological Survey Research Report RR/05/01 102pp. ISBN 0 852725175 | |||
| Jukes-Browne, A J and Hill, W. 1903 The Cretaceous Rocks of Britain, Vol.2. The Lower and Middle Chalk of England. Memoir of the Geological Survey of Great Britain. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E254 E237 E300 E317 E332 | |||