The BGS Lexicon of Named Rock Units — Result Details

Green Ammonite Member

Computer Code: GAB Preferred Map Code: GA
Status Code: Full
Age range: Pliensbachian Age (JE) — Pliensbachian Age (JE)
Lithological Description: Medium grey mudstones, with irregular limestones developed at three principal horizons (Lower Limestone; Red Band; and Upper Limestone). Phelps, 1985, beds 7 to 41.
Definition of Lower Boundary: Top of Belemnite Stone (bed 121 of Lang, W D, et al, 1923). Conformable junction with Belemnite Marl Member.
Definition of Upper Boundary: Base of lowest bed of the Three Tiers Sandstone (=base of Eype Clay Member of Dyrham Formation).
Thickness: To 31m
Geographical Limits: Southwest Dorset, United Kingdom. Mapped on Sheet 327 (Bridport). Northern limit not yet proved.
Parent Unit: Charmouth Mudstone Formation (CHAM)
Previous Name(s): Wear Cliff Beds (-270)
Green Ammonite Beds (-1550)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Cliffs around Golden Cap, near Seatown, Dorset. Lang, W D, 1936. 
Reference(s):
Arkell W J, 1933. The Jurassic System in Great Britain [Oxford: Clarendon Press.] 
Lang, W D, 1936. The Green Ammonite Beds of the Dorset Lias. Quarterly Journal of the Geological Society, London, Vol.92, 423-455. 
Day, E C H, 1863. On the Middle and Upper Lias of the Dorsetshire Coast. Quarterly Journal of the Geological Society of London, Vol.19, 278-297. 
Lang, W D, 1914. The geology of Charmouth cliffs, beach and fore-shore. Proceedings of the Geologists' Association, Vol.25, 293-360. 
Woodward, H B and Ussher, W A E, 1911. Sidmouth and Lyme Regis. Memoir of the Geological Survey, Sheets 326 and 340 (England and Wales). 
Phelps, M C, 1985. A refined ammonite biostratigraphy for the middle and upper Carixian (ibex and davoei zones, Lower Jurassic) in north-west Europe and stratigraphical details of the Carixian-Domerian boundary. Geobios, Vol.18, 321-361. 
Lang, W D, 1913. The lower Pleinsbachian - 'Carixian' - of Charmouth. Geological Magazine, Vol.10, 401-412. 
Hesselbo, S P and Jenkyns, H C A, 1995. A comparison of the Hettangian to Bajocian successions of Dorset and Yorkshire. 105-150 in Taylor, P D (Editor). Field geology of the British Jurassic (London Geological Society). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E327 E341 E342 E343