Upland Forest: Quarries
Fossils from uplands are scarce because these high grounds were sites of erosion—not the deposition required to bury and preserve fossils. At the Allied Stone Company Quarry in Milan, Illinois, Changes Institute scientists uncovered an ancient Pennsylvanian river channel. Upland plants that had fallen or were washed into the river were preserved in the shale that formed from the mud on the river bottom.
Spencer Farm Quarry
At Spencer Farm Quarry, near Mt. Sterling, Illinois, upland fossils are preserved in siltstone that formed in localized depressions. Nearly 30 genera of plant fossils have been collected from Spencer Farm and Allied Quarry.
Variation occurs across space in the types of fossils that were found in
the coal swamp, the estuaries, and marine areas.