The BGS Lexicon of Named Rock Units — Result Details

Marlstone Rock Formation

Computer Code: MRB Preferred Map Code: MRB
Status Code: Full
Age range: Pliensbachian Age (JE) — Toarcian Age (JT)
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: Lias Group (LI)
Previous Name(s): Marlstone Rock Member (-2328)
Marlstone (-1709)
Marlstone Rock Bed (-1710)
Marlstone Rock (-4803)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Tilton Railway Cutting (SSSI). Tilton, Leicestershire. Hallam, A, 1955, 1968; Howarth, M K, 1980, 1992. 
Reference Section  Marlstone workings at Fulbeck. See Lamplugh and others, 1920, p.124. 
Type Section  Jeffries Brickworks, near Stonehouse. See Ager, 1956. 
Reference Section  Stanley's Quarry, Edge Hill, Warwickshire. See also Cox, B M, et al, 1999 for additional sections. 
Reference(s):
Arkell W J, 1933. The Jurassic System in Great Britain [Oxford: Clarendon Press.] 
Howarth, M K, 1980. The Toarcian age of the upper part of the Marlstone Rock Bed of England. Palaeontology, Vol.23, 637-656. 
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. 
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). 
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). 
Ager, D V. 1956. Field meeting in the central Cotswolds. Proceedings of the Geologists' Association, Vol.66, 356-365. 
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. 
Hallam, A, "In" Sylvester-Bradley, P C and Ford, T D, (Editors), 1968. The geology of the East Midlands, chapter 11. 
Brandon, A. 1987. Geological Notes and Local Details for 1:10,000 Sheet SK94NW (Caythorpe). British Geological Survey Technical Report, WA/87/16. 
Lamplugh, G W, Wedd, C B, and Pringle, J. 1920. Bedded iron ores of the Lias, Oolites and later formations in England. Special Reports on the Mineral Resources of Great Britain, Vol. XII. Memoir of the Geological Survey of Great Britain. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E089 E127 E234 E199 E235 E102 E072 E080 E114 E143 E157 E170 E171 E203 E185 E186 E201 E202 E217 E218 E142 E236 E251 E103 E156 E184 E216 E219