The BGS Lexicon of Named Rock Units — Result Details

Ida Formation

Computer Code: IDA Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Pliensbachian Age (JE) — Pliensbachian Age (JE)
Lithological Description: The Ida Formation consists of thinly interbedded brown to grey siltstones, fine sandstones and argillaceous, occasionally oolitic (chamositic) and carbonaceous, limestones.
Definition of Lower Boundary: The lower boundary is defined by an abrupt downward transition from sandy and calcareous sediments to mudstones (Offa Formation). It coincides with an increase in gamma values and a decrease in velocity, which may be marked in some wireline logs.
Definition of Upper Boundary: The boundary is characterised by a downward change from mudstones (Cerdic Formation) to harder, sandy and calcareous, interbedded sequence of the Ida Formation. There is a sharp downward decrease in gamma values and an increase in velocity.
Thickness: Up to c. 30 m.
Geographical Limits: Southern North Sea Basin (quadrants 41-43, 46-49, 51-53).
Parent Unit: Lias Group (LI)
Previous Name(s): Lias Group (LI)
Alternative Name(s): Charmouth Mudstone Formation
Cleveland Ironstone Formation
Marlstone Rock Formation
Staithes Sandstone Formation
Stratotypes:
Type Section  North Sea Well 47/29a-1 between 590 and 607 m (Lott and Knox, 1994). 
Reference Section  North Sea Well 42/24-1 between 541 and 559 m (Lott and Knox, 1994). 
Reference Section  North Sea Well 48/18c-5 between 1030 and 1066 m (Lott and Knox, 1994). 
Reference Section  North Sea Well 53/1-3 between 912.5 and 929 m (Lott and Knox, 1994). 
Reference(s):
Lott, G K and Knox, R W O'B. 1994. 7. Post-Triassic of the Southern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. [British Geological Survey, Nottingham]. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable