Jungle on a Seabed
A jungle grew here. Before that, a shallow sea covered the land,
Both are gone now, but both left evidence of their passing.
The sea's signature is ammonites,
baculites, and clams, pearly foxxils
entombed in fossil mud called the
Pierre Shale, This shale is exposed in
the gully below you.
A jungle sprang up after the sea drained
away about 65 million years ago. For a
long time tree roots broke up the shale,
and chemicals from decaying plants
produced a yellow soil. About 37 million
years ago sediment from the west washed
over the jungle.
The jungle rebounded, converting the
new sediment into a red soil. Buried by
later sediments, both yellow and red soils
were fossilized. We call them the Yellow
Mounds Paleosol and the Interior Paleosol.