Sherwood Sandstone Group

Sherwood Sandstone Group (SSG)

Parent unit

No change to current definition

Previous nomenclature

No change to current definition

Derivation of name

From the eponymous area, SK 57 59 to SK 64 77, Sherwood Forest, Nottinghamshire

Reference Sections

See constituent formations

Extant exposures/sections

No change to current definition

Lithology

Sandstone, red, yellow and brown, part pebbly; conglomeratic in lower part; pebbles generally extraformational quartz and quartzite, with some intraformational clasts; subordinate red mudstone and siltstone.

Lower boundary

Disconformable on the Lenton Sandstone Formation in the eponymous area and on the Kinnerton Sandstone Formation in Cheshire. Unconformable on the Aylesbeare Mudstone Group in east Devon, the Bridgnorth Sandstone Formation in the West Midlands, the Cumbrian Coast Group in Lancashire and Cumbria, and the Zechstein Group in north Nottinghamshire, Yorkshire and Durham. In other areas it rests unconformably on rocks ranging from Precambrian to Carboniferous in age.

Upper boundary

Gradational into the Tarporley Siltstone Formation of the MMG where mudstone/siltstone becomes dominant over sandstone. In the Bristol area it is taken at the upward change to red sandstones of the Redcliffe Sandstone Member of the MMG (Howard et al., 2008). In the East Midlands the boundary with the Tarporley Siltstone Formation is an unconformity.

Thickness

No change to current definition

Age

Induan (?) to Anisian (Early to early Mid-Triassic)

Equivalent units

No change to current definition

Geographical extent

No change to current definition

Subdivisions

• Helsby Sandstone Formation
  • Burcot Member
  • Delamere Sandstone Member
  • Finstall Member
  • Frodsham Sandstone Member
  • Kibblestone Member Sellafield Member
  • Shepshed Sandstone Member
  • Sugarbrook Member
  • Thurstaston Sandstone Member
• Burwardsley Hill Bed
• Thurstaston Hard Sandstone Bed
• Wilmslow Sandstone Formation
  • Wildmoor Sandstone Member
• Chester Formation
  • Freehay Member
  • Lodgedale Member
  • North Head Member
  • St Bees Sandstone Member
• Glen Dubh Sandstone Formation
• Hopwas Breccia Formation
• Lamlash Sandstone Formation
• Moira Formation