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.

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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.