Oligocene

Oligocene Chart

Mediterranean Rupelian

65 Myr Climate Change

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Turtle Cove mural - Roger Witter

Ancient Mammal at Denver Museum of Nature and Science

Paraceratherium transouralicum

Oligocene is a geologic epoch of the Paleogene Period in the Cenozoic Era, spanning from about 33.9 million to 23 million years ago. It follows the Eocene Epoch and precedes the Miocene Epoch. The Oligocene is significant for its major geological and climatic changes, which had profound effects on the planet's ecosystems and the evolution of life.

Overview

During the Oligocene, the world's climate began cooling, leading to the expansion of glacial ice sheets on Antarctica and a drop in global sea levels. This epoch saw the development of the first grasslands, which would later become crucial environments for many species, including early grazers. The cooling climate also led to a shift in vegetation from tropical and subtropical forests to more temperate forests in many areas.

Fauna

The Oligocene epoch was a time of significant evolutionary change for many animal groups. Mammals, in particular, began to diversify into many forms that would become dominant in later epochs. Early forms of mammals such as horses, camels, and elephants started to appear. The Oligocene also saw the rise of the first large predators, including the ancestors of modern cats, dogs, and bears.

Flora

The flora of the Oligocene was diverse, with a significant shift towards modern plant species. The spread of grasslands encouraged the evolution of new types of plants that were adapted to drier, more open environments. This period also saw the continued dominance of angiosperms (flowering plants), which had become the predominant form of plant life during the preceding Cretaceous and Paleocene epochs.

Geology

The Oligocene was marked by significant tectonic activity, which shaped much of the modern world's geography. The formation of the Alps, Himalayas, and other major mountain ranges occurred during this time, as a result of the ongoing collision between the African, Eurasian, and Indian Plates. Additionally, the opening of the Drake Passage between South America and Antarctica is believed to have occurred in the late Oligocene, leading to the establishment of the Antarctic Circumpolar Current and further cooling of the global climate.

Climate

The climate of the Oligocene was cooler and more arid than that of the preceding Eocene, with significant glaciation on Antarctica. This cooling trend was a continuation of the Eocene-Oligocene extinction event, which marked the transition between the two epochs. The drop in temperatures and the expansion of ice sheets contributed to a decrease in sea levels, affecting marine life and altering coastlines around the world.

Impact on Evolution

The environmental changes of the Oligocene had a profound impact on the evolution of life on Earth. The adaptation to cooler climates led to the development of new species better suited to the changing conditions. The expansion of grasslands provided new niches for mammals, leading to an increase in diversity and complexity of mammalian species. This period set the stage for the evolution of modern ecosystems in the Neogene Period.