The BGS Lexicon of Named Rock Units — Result Details

MARLSTONE ROCK FORMATION
Computer Code: MRB  Status Code: FORMAL, NATIONAL 
Preferred Map Code: MRB 
Age or Age Range: [ JE ] PLIENSBACHIAN  to [ JT ] TOARCIAN 
Lithological Description:
Sandy, shell-fragmental and ooidal ferruginous limestone interbedded with ferruginous calcareous sandstone, and generally subordinate ferruginous mudstone beds. Locally any of these lithologies may pass by increase in iron content into generally ooidal ironstone, and in places any of these may dominate. The iron content (as ooids, altered shell material or in the groundmass) is berthierine (dark green iron-rich layered silicate formed in low-oxygen marine conditions), altering to siderite. Fossil content variable throughout but locally abundant especially in limestone beds. 
Definition of Lower Boundary:
At downward change to mudstone/siltstone of the Dyrham Formation, or (in East Midlands Shelf north) mudstone of Charmouth Mudstone Formation; base typically erosive and conglomeratic. Locally may rest on a sandstone bed at the top of the Dyrham Formation, which it may be impractical to map separately from the Marlstone Rock. 
Definition of Upper Boundary:
At upward change to mudstone/nodular limestones of the Whitby Mudstone Formation. 
Thickness:
To about 10m 
Geographical Limits:
East Midlands Shelf and Worcester Basin (Mendip to Market Weighton). 
Parent Unit: Parent Unit Code:
LIAS GROUP  LI
Previous Name(s): Previous Code(s):
MARLSTONE   
MARLSTONE ROCK MEMBER   
MARLSTONE ROCK BED  MRB 
MARLSTONE ROCK   
Alternative Name(s):
none recorded or not applicable
Stratotypes:
Reference Section  Marlstone workings at Fulbeck. 
Type Section  Jeffries Brickworks, near Stonehouse. 
Type Section  Tilton Railway Cutting (SSSI). Tilton, Leicestershire. 
Reference Section  Stanley's Quarry, Edge Hill, Warwickshire. 
Reference(s):
Arkell, W J. 1933. The Jurassic System in Great Britain. [Oxford: Clarendon Press.] 
Brandon, A. 1987. Geological Notes and Local Details for 1:10,000 Sheet SK94NW (Caythorpe). British Geological Survey Technical Report, WA/87/16. 
Hallam, A, "In" Sylvester-Bradley, P C and Ford, T D, (Editors), 1968. The geology of the East Midlands, chapter 11. 
Lamplugh, G W, Wedd, C B and Pringle, J, 1920. Special Reports on the Mineral Resources of Great Britain, Vol.XII, Iron Ores (ctd) Bedded Ores of the Lias, Oolites and later Formations in England. Memoir of the Geological Survey of Great Britain. 
Brandon, A, Sumbler, M G and Ivimey-Cook, H C, 1990. A revised lithostratigraphy for the Lower and Middle Lias (Lower Jurassic) east of Nottingham, England. Proceedings of the Yorkshire Geological Society, Vol.48, 121-141. 
Ager, D V, 1956. Field Meeting in the Central Cotswolds. Proceedings of the Geologists' Association, Vol.66, p.360. 
Cox, B M, Sumbler, M G and Ivimey-Cook, H C, 1999. A Formational framework for the Lower Jurassic of England and Wales (Onshore Area). British Geological Survey Research Report No. RR/99/01. 
Hallam, A, 1955. The palaeontology and stratigraphy of the Marlstone Rock-bed in Leicestershire. Transactions of the Leicester Literary and Philosophical Society. Vol.49, 17-35. 
Howarth, M K, 1980. The Toarcian age of the upper part of the Marlstone Rock Bed of England. Palaeontology, Vol.23, 637-656. 
Howarth, M K, 1992. The ammonite family Hildoceratidae in the Lower Jurassic of Britain. Part 1. Monograph of the Palaeontographical Society London: 1-106, pls.1-16. (Publication No.586, part of Vol.145 for 1991). 
Hallam, A, 1968. The Lias. 188-210 in The geology of the East Midlands. Sylvester-Bradley, P C and Ford, T D (editors). (Leicester: Leicester University Press). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
Map Code Sheet Name
E  234
E  219
E  156
E  216
E  89
E  127
E  235
E  199
E  203
E  186
E  157
E  170
E  102
E  72
E  114
E  171
E  80
E  143
E  185
E  201
E  217
E  236
E  202
E  142
E  251
E  218
E  184
E  103

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