Paleogene

Paleogene

The Paleogene Period is a major division of the geologic timescale that began about 66 million years ago and ended about 23 million years ago. It is the first period of the Cenozoic Era, following the Cretaceous Period and preceding the Neogene Period. The Paleogene is divided into three epochs: the Paleocene, Eocene, and Oligocene.

Geological Overview

The Paleogene Period marks a significant transition in Earth's history, characterized by dramatic changes in climate, geography, and life forms. It followed the mass extinction event at the end of the Cretaceous, which wiped out approximately 75% of Earth's species, including the non-avian dinosaurs.

Paleocene Epoch

The Paleocene Epoch (66 to 56 million years ago) was a time of recovery and diversification. The climate was warm and humid, and the continents were beginning to take on their modern shapes. Mammals, which had been small and nocturnal during the age of dinosaurs, began to diversify and occupy new ecological niches.

Eocene Epoch

The Eocene Epoch (56 to 34 million years ago) saw the emergence of many modern mammal families. The climate was warm, with tropical conditions extending to high latitudes. This epoch witnessed the appearance of the first primitive whales, early horses, and many other mammalian groups.

Oligocene Epoch

The Oligocene Epoch (34 to 23 million years ago) was a time of global cooling, leading to the development of polar ice caps. This cooling trend caused significant changes in flora and fauna, with the expansion of grasslands and the evolution of grazing mammals.

Paleogeography

During the Paleogene, the continents continued to drift toward their present positions. The Atlantic Ocean widened as North America and Eurasia moved apart. The Tethys Ocean closed as Africa and India moved northward, leading to the formation of the Alps and the Himalayas.

Flora and Fauna

The Paleogene Period was a time of significant evolutionary change. Following the extinction of the dinosaurs, mammals rapidly diversified and became the dominant terrestrial vertebrates. Birds also diversified, and flowering plants continued to evolve and spread.

Mammals

Mammals underwent an adaptive radiation during the Paleogene, filling ecological niches left vacant by the extinction of the dinosaurs. This period saw the rise of many modern mammal groups, including primates, rodents, and ungulates.

Birds

Birds also diversified during the Paleogene, with the appearance of many modern orders. Large flightless birds, such as the Gastornis, were common in some regions.

Plants

Flowering plants (angiosperms) continued to dominate the landscape, with the spread of deciduous forests and the first appearance of grasses.

Climate

The Paleogene climate was initially warm and tropical, but it gradually cooled, leading to the development of ice caps in the polar regions by the end of the period. This cooling trend was influenced by changes in ocean circulation and the configuration of the continents.

Also see

• Cenozoic Era
• Mesozoic Era
• Neogene Period
• Paleocene–Eocene Thermal Maximum
• K–Pg extinction event