Geodiversity

Chipping Norton Formation

Some Key Words

calcareous

containing calcium carbonate

cross-bedded

a sedimentary structure developed by the migration of small ripples, sand waves, tidal-channel large-scale ripples, or dunes and consists of sets of beds that are inclined to the main horizontal bedding planes. 

lignite

a soft coal, usually dark brown, often having a distinct woodlike texture, and intermediate in density and carbon content between peat and bituminous coal.

ooidal

consisting of or containing small, spherical or sub-spherical ooids.

Parent group:

Great Oolite

Period:

Jurassic

Age:

Bathonian

(166.1–168.3 Ma)

Description:

This limestone ranges in thickness from 0-12 m (12.7 m at Chipping Norton). Lithologically it is a hard, splintery, buff/brown rock. Texturally it may be described as fine to medium-grained ooidal and coated peloidal grainstone. Fine burrows, medium to coarse-grained shell detritus, flakes of greenish grey mudstone, dark lignite and minor amounts of fine-grained sand elude to its near shore, marine depositional environment.   The Chipping Norton Limestone can be described as a thick-bedded and cross-bedded, weathering to flaggy or platy. Thin shell-detrital and ooidal marl and mudstone intercalations in places.  

 

Boundaries:

Vertically, the Chipping Norton limestone has a lower boundary  which is conformable/non-sequential with the Clypeus Grit member. Locally a mudstone bed (Roundhill Clay)  up to c.1 m thick occurs at the base. The upper boundary is with the Sharp's Hill Formation.      Laterally the formation passes into the Horsehay Sand Formation to the north east.  

 

Thickness:

0-12 m

 

Spatial distribution:

North Oxfordshire Cotswolds.  


Type Section:

Oxfordshire County Council Quarry, Chipping Norton. 
     

Reference sections:

Ditchley Quarry aka Town Quarry, Charlbury (SP 370 200)