Fossil leaves are the preserved remains of leaves that have been buried and mineralized over time. They provide valuable information about ancient plant life and the environments in which they thrived. Fossilization typically occurs when leaves are buried in sediment, where minerals gradually replace organic material, creating a lasting imprint. These fossils can be found in various geological formations and are often studied by paleobotanists to understand past climates and ecosystems. By examining fossil leaves, scientists can learn about the types of plants that existed during different geological periods, such as the Cretaceous or Paleogene periods.