The BGS Lexicon of Named Rock Units — Result Details

Easton Anhydrite Member

Computer Code: EANHY Preferred Map Code: notEntered
Status Code: Full
Age range: Visean Stage (CV) — Visean Stage (CV)
Lithological Description: Grey or white anhydrite interbedded with limestones, shales, siltstones and sandstones.
Definition of Lower Boundary: The base of the member is not seen, but seismic interpretation indicates the presence of ‘several thousands of feet’ of conformable strata below the succession in some parts of the Solway Basin (see Ward, 1997, p. 283).
Definition of Upper Boundary: The top of the member is taken where numerous beds of anhydrite interbedded with limestones, shales, siltstones and sandstones give way to strata with variously algal, oolitic, peloidal, shelly, crinoidal and serpulid limestones, which may represent the Main Algal Member of the Lyne Formation. However, this has not been positively identified.
Thickness: More than 1153 m (base not seen).
Geographical Limits: Solway Basin, proved in the Easton 1 borehole. The member is not exposed at the surface (breccias present suggest it was removed by solution), but seismic reflectors suggest that the top of the member extends at depth from west Cumbria eastwards to the flanks of the Bewcastle Anticline and beyond (see Ward, 1997, fig. 11). A total area well in excess of 1000 km2 is inferred.
Parent Unit: Lyne Formation (LYNE)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  The partial type section is the Easton 1 borehole (BGS Registration Number NY47SW/15) [NY 44124 71694] from 1054 to 2260 m depth (the base of member not being proved). An upper unit, 126 m thick, includes successions of generally upward-thinning beds of anhydrite, interbedded with limestone, some dolostone, sandstone and shale. A middle unit, 639 m thick, includes nine large cyclical sequences of limestones, shales, sandstones and anhydrite. A lower unit, at least 440 m thick, includes composite limestone-anhydrite beds, 2.4–6.1 m thick, separated by shales or claystones that thicken downwards. Sandstones in this unit are numerous but thin. 
Reference(s):
Dean, M T, Browne, M A E, Waters, C N and Powell, J H. 2011. A lithostratigraphical framework for the Carboniferous successions of northern Great Britain (onshore). British Geological Survey Research Report, RR/10/007. 165pp. 
Ward, J. 1997. Early Dinantian evaporites of the Easton-1 well, Solway Basin, onshore Cumbria, England. 277-296 in Petroleum geology of the Irish Sea and adjacent areas. Meadows, N S, Trueblood, S P, Hardman, M, and Cowan, G (editors). Geological Society of London Special Publication, No. 124. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable