Aptian

The Aptian is a time period in Earth's history. It is part of the Early Cretaceous, when dinosaurs lived. The Aptian happened about 121 to 113 million years ago. It came after a time called the Barremian and before another time called the Albian.

During the Aptian, big changes happened in the oceans. There was an event called the Selli Event, which changed the oceans and affected many sea creatures. This event happened around 120 million years ago and lasted for about a million years.

Another important thing from the Aptian was a small drop in the number of some animals and plants. Scientists call this the Aptian extinction. It happened around 116 to 117 million years ago. These events help scientists learn about how Earth has changed over millions of years.

Stratigraphic definitions

The Aptian was named after the small city of Apt in the Provence region of France. It was first used in science by a French scientist in 1840.

The Aptian comes after the Barremian and before the Albian in the study of very old rock layers. It is part of the Early Cretaceous period.

Subdivision

In an area called the Tethys domain, the Aptian can be divided using special fossils called ammonites. These include zones named after different types of ammonites.

Sometimes the Aptian is split into three smaller parts: Bedoulian, Gargasian, and Clansayesian. In modern studies, it is split into Lower and Upper parts. The Lower Aptian is similar to the Bedoulian, and the Upper Aptian includes the Gargasian and Clansayesian parts.

Lithostratigraphic units

During the Aptian, many important rock layers formed around the world. Some examples are the Antlers Formation, Cedar Mountain Formation, Cloverly Formation, Elrhaz Formation, Jiufotang Formation, Little Atherfield, Mazong Shan, Potomac Formation, Santana Formation, Twin Mountains Formation, and Xinminbao Group. These rock layers help scientists learn about Earth from millions of years ago.

Climate

See also: Aptian-Albian Cold Snap

At the start of the Aptian, the world got colder. We know this because some tiny ocean plants moved to warmer places near the equator. During this time, the amount of a gas in the air called carbon dioxide went down from about 1,000 parts per million to around 800 parts per million. Later in the Aptian, the amount of this gas stayed between about 515 and 1030 parts per million.