Oxfordshire Rock Types
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 STRATIGRAPHIC COLUMN of OXFORDSHIRE ROCK FORMATIONS
A stratigraphic column works by listing the youngest rock formations at the top, down to the oldest rock formations at the bottom. This list is partially interactive - we're working to make it totally interactive by Winter 2022, click on the formation for more information - if a link isn't active yet, it will be very soon.
2.6 Million Years Ago
TERTIARY
66 Million Years Ago
Thames
Group
Lambeth
Group
bioturbated dark clay
London Clay
plastic, mottled clays
Reading
66 Million Years Ago
UPPER/LATE CRETACEOUS
100.5 Million years ago
White
Chalk
Grey
Chalk
firm, white chalk with tabular flint seams
Seaford Chalk
moderately hard chalk
Lewes Nodular Chalk
moderately hard chalk
New Pit Chalk
nodular chalks with thin flaser marls
Holywell Nodular Chalk
marly, hard chalk
West Melbry Marly Chalk
100.5 Million Years Ago
LOWER/EARLYCRETACEOUS
145 Million Years Ago
Upper Greensand
clay and sandstone
Gault
blue-grey clay or mudstone
Lower Greensand
sands & sandstone with some clay and silts.
Kellaways Beds
sands and clays
Great
Oolite
Group
Inferior
Oolite
Group
flaggy limestone & clay
Forest Marble
fossilferous limestone
White Limestone
Hampen
thin limestones interbedded with marls
Taynton
shelly oolitic limestone
thin-bedded clay