Poplar

The fossilised leaves seen here on this marlstone came from trees that grew in the immediate vicinity of lakes, oxbow lakes or floodplains. Their leaves fell into water and were quickly coated in chalk-rich mud. As a result, the recognisable leaves of poplar, willow and plane trees have not been destroyed, but instead have lasted for 13.5 million years! Carbon was the only original residual chemical element in the leaf, which is why the leaf fossil is black.
The earliest discoveries of the Populus family are around 58 million years old! Poplar trees still grow in wet habitats today.