Oxfordshire Rock Types

Rock types of Oxfordshire
The oldest rocks to crop out are in the north, of the county, in the Banbury area, and are of Lower Jurassic age, circa 200 million years old. Younger rocks Mezozoic formations crop out successively towards the south-east. The harder rock types are relatively more resistant to weathering and erosion and these form hills. These more resistant rocks are known as limestone and chalk. The intervening vales are bottomed by clays and sands.
A simplified Jurassic stratigraphy of Oxfordshire
Kellaways Beds
sands and clays
Great
Oolite
Group
flaggy limestone & clay
Forest Marble
fossilferous limestone
White Limestone
Hampen
thin limestones interbedded with marls
Taynton
shelly oolitic limestone
thin-bedded clay
Sharp's Hill
Horsehay Sand
sandstone, ironstone
Northampton Sands
Ancholme
Group
Inferior
Oolite
Group
Chipping Norton
176 Million Years Ago
LOWER/
EARLY
JURASSIC
161 Million Years Ago
Upper
mainly clay
Middle
silt, sand and muddy marlstone
Lower
clay and muddy limestone