Callovian

The Callovian is a special time in Earth's history. It is part of what scientists call the Middle Jurassic. It lasted from about 165.3 million years ago to 161.5 million years ago. This time came after another period called the Bathonian and before one called the Oxfordian.

Scientists use names like Callovian to help organize the layers of rock and fossils found around the world. By studying these layers, they can learn about the plants, animals, and climate from the past.

The Callovian helps us picture a world very different from today. Dinosaurs roamed the land, and the continents looked unlike they do now. It is important for learning about how Earth and its living things have changed over millions of years.

Stratigraphic definitions

The Callovian Stage was first described by a French scientist named Alcide d'Orbigny in 1852. Its name comes from a place called Kellaways Bridge in England.

The start of the Callovian is marked by the first appearance of a special type of fossil shell called an ammonite, specifically a group known as Kepplerites. The end of the Callovian is marked by the first appearance of another ammonite species called Brightia thuouxensis.

The Callovian is sometimes split into three smaller parts: Early, Middle, and Late Callovian. In a region called the Tethys domain, it includes six zones based on different ammonite fossils.

Palaeogeography

During the Callovian time, Europe was made up of many large islands. Between these islands were wide areas of shallow ocean. Because of this, we find layers of stone from shallow seas in places like Russia, Belarus, Poland, Germany, France, Spain, and England. Near the old coastlines of these islands, we often find sediments that came from the land, such as in western Scotland.

The Louann Salt and the southern Campeche Salt in the Gulf of Mexico are believed to have formed when a part of the Pacific Ocean pushed into what is now Mexico.