Plants From The Cretaceous Period. Other cretaceous period plants included: During the late cretaceous l evels fall to ~1,000 ppm.

The most dramatic occurrence during the cretaceous was the first appearance of flowering plants, the angiosperms!! During the late cretaceous l evels fall to ~1,000 ppm. Oxygen levels begin at ~20.5% and increase to ~22.5% by the end of the period.