The BGS Lexicon of Named Rock Units — Result Details

Middleton Dale Anhydrite Formation

Computer Code: MIDA Preferred Map Code: notEntered
Status Code: Full
Age range: Tournaisian Stage (CT) — Tournaisian Stage (CT)
Lithological Description: Bedded and nodular anhydrite interbedded with dark grey mudstone and thin beds of dolostone. A thin grey-green and red sandstone marks the base of the formation, with dark grey dolostone and thin dolomitic mudstone beds dominant in the lower part of the unit.
Definition of Lower Boundary: Unconformable, with grey-green and red sandstone of the Middleton Dale Anhydrite Formation overlying grey and purple mudstone of Ordovician age.
Definition of Upper Boundary: Sharply unconformable, and defined as the base of the lowermost thick, dark grey dolostone bed of the Woo Dale limestone Formation, overlying anhydrite of the Middleton Dale Anhydrite Formation.
Thickness: Measured as 73.6 m thick in the Eyam Borehole.
Geographical Limits: Proved in the subsurface only, in the northern part of the Peak District [SK27].
Parent Unit: Not Applicable (-)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  The Eyam borehole (SK27NW), located within the Furness Quarry, Middleton Dale, about 1.3 km SSW of Eyam, from a depth of 1803.25 to 1729.64 m. Dunham, 1973. 
Reference(s):
Dunham, K C. 1973. A recent deep borehole near Eyam, Derbyshire. Nature Physical Science, Vol. 241, 84-85. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E099