Three pollen zones are found in 1 m of sediment from a small marsh on Pigeon Mountain. The oldest, which begins at 19,520 yr B.P. and ends at 10,820 yr B.P., has pollen of pine, spruce, deciduous trees, and herbs, which implies that the plateau was not forested in full-glacial time but that tree pollen was transported to the site from valleys below the plateau. The second zone of late Pleistocene or early Holocene age implies a mesic forest in which beech was a common tree. The youngest zone has pollen of oak, chestnut, sweetgum, and blackgum, representing the modern somewhat xeric oak forest.
The site was a pond with water lilies and rooted and submerged aquatic plants at the time of zones P-l and P-2. Subsequently, woody wet-ground plants (such as button-bush, red maple, sweetgum, and willow) invaded the site and converted it into a marsh.