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.

Eon Era Period Epoch. Two or more periods comprise a geological era. However, eon is an indefinite period of time that is divided into many eras, which in turn recognize certain periods of time that are marked by some distinctive changes.

An epoch is longer than an era and can cover more than one lifetime. When first proposed as a division of geologic time, the beginning of the phanerozoic (542.0 million years ago)* was thought to coincide with the beginning of life. Epoch = a unit of.