Quickly settling sediments also favor fossilization. Each layer of sediment protects the leaf from organisms that would destroy it. So paleobotanists like Wing search for plant fossils in sediment that was once very wet and accumulated rapidly. Where floods laid down new earth quickly, layers of sediments are stacked, one on top of the other, making the rock striped. If earthworms had destroyed the plants, they also would have churned up the earth, erasing the boundaries between layers.
Wing looks for fossils in dark stripes, because fossil plant material makes rock dark.
But scientists can look for these visual cues only if the they can see the rock. That's why they end up working in places like Wyoming, where much of the land is desert or semi-desert, and erosion has exposed layers from tens of millions of years ago. Once scientists have found dark-colored layers of rock from the geologic time they are studying, they start hunting for fossils. Using a pick and shovel, Wing collects chunks of rock the size of toaster ovens, and meticulously labels them by location. He splits open a rock by hitting it on its edge.