While less familiar than their animal counterparts, fossilized leaves have left their imprint in the geological record and serve as vital evidence in studies focused on CO2 and climate history. They are typically preserved in they types of deltaic and fluvial systems where rivers deposit sediment. Abandoned river channels that created oxbow lakes are a particularly prime location where they can be found.

Within oxbow lakes, plants tend to be deposited in fine-grained sediment that has been buried through a series of flooding events that ultimately compacted the ground and squeezed the water out. This compresses the leaf’s internal structure, leaving behind a thin carbonaceous film that preserves the original outline of the plant structure. Generally, large and angular sediment grains leave poorly detailed fossils, while smooth, fine sediments result in finely detailed imprints that simplify the identification process.

Beyond the aesthetic desirability of fossilized leaves, one major reason why they are retrieved and studied is to gain insight into the earth’s climate. Scientists employ them in estimating annual rainfall and temperature at various epochs in the planet’s history. They can then compare them with megafauna captured in the geologic record of the same region. This provides a complex picture of migration cycles and extinction events, and the overarching paleo-ecology of the region.