The Triassic Lykins
Formation is made of red shales and thinly bedded limestone and gypsum beds.
As a consequence, it erodes fairly easily and is often somewhat inconspicuous,
despite its brilliant red coloration. The limey beds are characterized by
thin layers that sometimes occur in mounds and hummocks called stromatolites.
The 400-foot-thick beds are named after Lykins Gulch, located north of Boulder.
Fossil stromatolite layers