Geodiversity
Oxfordshire Rock Types: Chipping Norton
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)