Paleocene

Much of the world's modern vertebrate diversity originated in a rapid surge of diversification in the early Paleogene, as survivors of the Cretaceous-Paleogene extinction event took advantage of empty ecological niches left behind by the extinction of the non-avian dinosaurs, pterosaurs, marine reptiles, and primitive fish groups.

The K-Pg extinction event, brought on by an asteroid impact (Chicxulub impact) and possibly volcanism (Deccan Traps), marked the beginning of the Paleocene and killed off 75% of species, most famously the non-avian dinosaurs.

The land bridge provided a northern route from Europe to North America from the Late Cretaceous to the Early Paleocene, although this timeframe has been disputed.

Around 50 to 60 million years ago, during the Paleocene Epoch, Antrim was subject to intense volcanic activity, when highly fluid molten basalt intruded through chalk beds to form an extensive volcanic plateau.

It was formed from Palaeocene-Upper Eocene with the interbedding of sandstone and shales.

This episode saw the reactivation of cretaceous thrust faults and the development of long and short wavelength folding of Paleocene marine sediments that infilled previous foredeep accommodation.

The Hell Creek Formation is an intensively studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana.

Measuring approximately 75 by 40 miles (121 by 64 km), the swell consists of a giant dome-shaped anticline of sandstone, shale, and limestone that was pushed up during the Paleocene Laramide Orogeny 40-60 million years ago.