The life of those times, preserved as fossils, reveal the development of
the higher invertebrates, then the fishes, and finally land animals and
plants. At the foot of McAdams Peak, Twin Springs flows from
Ordovician-Silurian rocks, deposited in the sea 350 million years ago.
All the ridges are mantled with loess (pronounced "less"), wind blown
dust laid down a million years ago at the time of the Great Ice Age. The
vertical banks of yellow clay seen along the road to the upper areas are
composed of this material, capped by the black topsoil that supports the
present forest.
More than 60 species of trees have been listed; Pecans, Red Cedars and
Butternuts being notable. Spring comes with the flowering of the
Shadbush; Redbud and Wild Plum are succeeded by the even more lovely
Dogwood. Flowers abound, and later berries light up dark places, and
mosses, ferns and lichens, form an agreeable ensemble. Mushrooms are
conspicuous for their number. With autumn the woods are a
never-to-be-forgotten blaze of color.