The BGS Lexicon of Named Rock Units — Result Details

Lower Lias (Undifferentiated) [Obsolete Name And Code]

Computer Code: LLI Preferred Map Code: notEntered
Status Code: Index Level
Age range: Hettangian Age (JH) — Pliensbachian Age (JE)
Lithological Description: Grey mudstones with concretionary and tabular argillaceous limestone, ironstone or sandstone.
Definition of Lower Boundary: Base Hettangian or base Lias Group [see notes under "Geographical Limits"]
Definition of Upper Boundary: Top Lower Piensbachian or base of succeeding arenaceous/calcareous strata belonging either to the Lower or Upper Pliensbachian [see notes under "Geographical Limits"].
Thickness: Unspecified
Geographical Limits: The term was used loosely to signify the lower, mudstone-dominated, part of the Lower Jurassic succession now known as the Lias Group. It has been used more specifically to mean Hettangian to Lower Pliensbachian strata (chronostratigraphical, not lithostratigraphical). In this context it excluded latest Triassic beds of the basal Lias Group and included arenaceous beds (=Middle Lias of some authors) at the top of the Lower Pliensbachian.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Redcar Mudstone Formation
none recorded or not applicable
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:
E279 E280 E184 E126 E263 E262 E249 E248 E234 E064 E072 E114 E127 E143 E157 E159 E161 E170 E171 E172 E185 E187 E188 E201 E202 E204 E217 E218 E220 E235 E236 E250 E251 E253 E264 E265