Gloucestershire Geology Trust


Gully Oolite [Crease Limestone]

Early Carboniferous (Chadian)

Carboniferous Limestone
Gully Oolite

Typically comprising pale and adrk grey medium- fine- grained, cross-bedded oolitic and crinodal limestone, which is white weathering and exceedingly massive, with strong vertical joints. Often internal structures have been destroyed by dolomitisation and emplacement of iron ores, chiefly haematite and goethite. Within the main ore field it is found as a light grey, crystalline, subsequent dolomite which resembles granulatd sugar in grain size.

Upper Boundary
The top of the Formation is taken at the sharp erosional contact between the mudstone/clay palaeosol at the top of the Formation and the overlying thin-bedded calcite mudstones and mudstones of the Llanelly Formation (Whitehead Limestone).

Lower Boundary
The base is taken at the gradational to sharp contact between the dolomitised sparsely crinoidal packstones of theBarry Harbour / Friars Point Limestone Formation or its parent the Black Rock Limestone Subgroup and the overlying oolitic grainstones or dolomitised oolite of the Formation. In the south the junction appears conformable but can be difficult to determine due to subsequent dolomitisation blurring the boundary; in the north a thin red clay overlying a palaeokarstic surface is locally present; in such cases the top is taken at the top of the red clay.

Representative Sites
Tintern Quarry
Old Park Wood Scowles
Lydney Park

and BGS Memoirs.

