Fossil leaves. Fossils are impressions formed in rocks of objects buried in the original deposits from which the rocks formed. Under the right conditions, the details and anatomy of the objects, such as animals and plants, can be preserved. Here, the veins of the leaves are clearly seen. Fossils can indicate how climate and ecology have changed over geologic time. These fossils were found in Tertiary rocks (65 million to 1.8 million years ago) on a glacial moraine, in Longyearbyen, Svalbard, an Arctic archipelago governed by Norway.