The BGS Lexicon of Named Rock Units — Result Details

Middle Lias (Undifferentiated) [Obsolete Name And Code]

Computer Code: MLI Preferred Map Code: notEntered
Status Code: Index Level
Age range: Pliensbachian Age (JE) — Toarcian Age (JT)
Lithological Description: Siltstones, sandstones, ironstones and limestones with subsidiary mudstone or sandstone.
Definition of Lower Boundary: Base of Upper Pliensbachian or base of arenaceous/calcareous strata belonging to either Lower or Upper Pliensbachian. [See notes under "Geographical Limits".]
Definition of Upper Boundary: Top of Upper Pliensbachian or top of arenaceous/calcareous/ferruginous strata belonging to either the Upper Pliensbachian or the Lower Toarcian. [See notes under "Geographical Limits".]
Thickness: Unspecified
Geographical Limits: The term Middle Lias was used as a loose term to signify the middle, arenaceous/ferruginous part of the Lower Jurassic succcession that is now known as the Lias Group. It has commonly been used to mean Upper Pliensbachian strata (ie used in a chronostratigraphical, not lithostratigraphical, sense).
Parent Unit: Lias Group (LI)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Staithes Sandstone Formation
Stratotypes:
none recorded or not applicable
Reference(s):
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:
E184 E064 E072 E114 E127 E143 E157 E159 E170 E171 E172 E185 E186 E201 E202 E204 E217 E218 E220 E235 E236 E251 E253 E265 E279