Dinosaur Park

A Petrified Forest

5 Digs

Dinosaur Park volunteer Jennifer Crump is working on labeling and identifying petrified wood specimens.

In 2014, avocational fossil hunter Chip Ohlhaver donated his substantial collection of petrified wood to Dinosaur Park. The term “petrified wood” literally means wood turned to stone. This occurs through the process of permineralization, in which water containing minerals gently percolates through the pores and cells of dead organisms. The organic components eventually disappear, but the minerals remain, preserving the structure of the organism at the cellular level. This process takes tens of thousands of years. Most dinosaur fossils form via permineralization, but the same process can preserve pieces of trees and other woody plants.

Mr. Ohlhaver collected most of the petrified wood near Dinosaur Park, in a location that is now a housing development. Like the Dinosaur Park fossils, the wood comes from the early Cretaceous Period, but it may be several million years older or younger than the fossils found at the Park. Since the particular exposure the petrified wood came from no longer exists, it is especially important that these specimens be conserved for future study.

This summer, we have been working on identifying, labeling, and housing the petrified wood collection. The vast majority of the wood is apparently cypress – or something similar. Some specimens have been tentatively identified as tree ferns and deciduous trees. So far, this supports our understanding that much of central Maryland was a swampy lowland during the early Cretaceous. Today, cypress trees are common in lowland swamps throughout the southeast United States. These trees are well-adapted to life in waterlogged, swampy soil. In addition to their rot-resistant wood, their knees (woody extensions of the roots) help to stabilize the tree in soft ground.

Plant fossils are important because they are reliable indicators of climate and environment. The environmental tolerances of modern plants (temperature, annual rainfall, soil acidity and stability) give paleontologists a good idea of what the ancient environment was like when we find their fossil relatives. We can also compare the plant communities in fossil deposits of different ages to learn how the Earth’s climate has changed over time.