It is subdivided into three formations that are all marine deposits (sands and clays) of Oligocene age.
The Rupel Group was first named by Belgian geologist André Hubert Dumont in 1849.
It shares its name with the Rupelian age (34 to 28 million years ago) of the geological timescale.
The formations of the Rupel Group therefore have a shallow marine to near coastal facies.
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