Eocene

Article

January 26, 2022

The Eocene (Ancient Greek: ἠώς (ḗōs) dawn; καινός (kainós) new; or the dawn of the new) is an epoch in the geologic time scale, lasting from 56.0 to 33.9 million years ago (Ma) . The Eocene follows the Paleocene and is followed by the Oligocene. The Eocene was an era with a distinctly warm and wet climate. In fact, the earliest part of the Eocene had the warmest climate of the past 100 million years. Later in the Eocene, some temperature decreases occurred, but tropical temperatures continued to prevail up to high latitudes. Above the Arctic Circle there was a temperate climate and deciduous forest grew. The diversification of mammals and birds, which began during the Paleocene, continued during the Eocene. Among the plants appeared the first modern grasses. The Eocene ended with a mass extinction that is called de grande coupure, especially in European faunas.

Paleogeography

During the Eocene, Antarctica and Australia moved further and further apart, leaving Antarctica isolated at the South Pole. As a result, the sea current in an easterly direction around this continent (the so-called Circum-Antarctic sea current) could arise. India and Africa also moved north, causing the Tethys Ocean between these continents and Eurasia to slowly close and the Alpine orogeny continued. At the same time, Greenland was moving further away from Europe, widening the northern part of the Atlantic. Under the influence of this, crust extension also prevailed in the North Sea basin, as a result of which further tectonic subsidence of the earth's surface took place and the area around the present North Sea (including the Netherlands and the north of Belgium) was covered by the sea. Further south, the Alps began to form. North of the new mountain range, a large foreland basin in present-day Switzerland and southern Germany, called the Molasse basin, was covered by an inland sea stretching between the Alps and Central Europe. Mountains also began to form elsewhere in Europe and Asia: the Pyrenees, Dinaric Alps and Hellenids in Europe and the Zagros and Himalayas in Asia. Europe and Asia were separated by the Turgai Strait east of the Urals. North and South America were separated from each other during the Eocene. In western North America, the Laramide orogeny continued. At the North Pole, the continents of North America, Europe, and Asia were almost abutting, only the narrow connections of the then narrow northern Atlantic Ocean, the Labrador Sea, and the Turgai Strait connected the Arctic Ocean with other seas. Because these connections were not very wide, there was no thermohaline circulation in the Eocene that mixed the waters of the Arctic Ocean with that of other seas, as it does today.

Paleoclimate

Thermal maximum

The transition between the Paleocene and Eocene is marked by a sudden and brief global temperature rise called the Paleocene-Eocene Thermal Maximum (PETM). Average temperatures at higher latitudes rose to 7°C in 20,000 years, one of the fastest and largest climatic changes in geological history. This unusually warm situation lasted less than 100,000 years. The climate change caused a mass extinction that makes the Eocene fauna very different from that of the Paleocene. There are a number of possible causes for the sudden temperature rise, but none explain the speed at which the temperature rise occurred. However, it is suspected that the gradual warming during the Late Paleocene brought sea temperatures above a certain critical value, causing massive dissolution of gas hydrates on the ocean floor, releasing large amounts of methane into the atmosphere. Methane is a very strong greenhouse gas (twenty times the effect

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