The inland sea retreated with the beginning uplift of the Laramide Rocky Mountains.
Rivers carried sediment from the mountains to the shore (Fox Hills Formation).
Along the rivers, sand, clay, and coal were deposited in alternating layers.
These river and swamp deposits are the Laramie Formation.
Dinosaurs and plant debris made impressions on muddy surfaces before being buried by sand that washed in from periodic floods.
The rocks where you are now standing are about 68 million years old.
The following diagrams show how the rocks you see along the Triceratops Trail were formed.
When dinosaurs left their tracks at this site,
the environment was similar to the swampy Mississippi Delta region of modern-day Louisiana.
River channels were flanked by swamps where clay and coal deposits formed.
During periodic floods, the river breached its banks, spilling sand across the swamps.
This repeated flooding created the alternating sand and clay layers that we see here.