Famennian

The Famennian was a time period during the later part of the Late Devonian epoch, an ancient time in Earth's history. It was one of two main stages in this epoch, coming after the Frasnian stage and before the Tournaisian stage. Scientists believe the Famennian lasted from about 372.15 million years ago to 358.86 million years ago.

This stage is important for understanding how life on Earth changed over time. Many kinds of animals lived in the oceans during the Famennian, and studying this period helps scientists learn about how Earth’s environment and its creatures developed long ago. The Famennian gives us clues about the history of our planet and the development of life.

Major events

During the Famennian, a new group of sea creatures called clymeniids, which were a type of ammonoid cephalopods, appeared, spread around the world, and then went extinct.

The start of the Famennian was marked by the final stages of a big extinction event, known as the Kellwasser Event. At the end of this time, there was another smaller but still serious extinction event, called the Hangenberg Event. There was also a short period of cold weather, possibly linked to this event, which was the first of several cold periods before the Late Palaeozoic ice age in the later Carboniferous and Permian periods.

Subdivisions

The Famennian is divided into four informal substages based on conodont zonation. In German stratigraphy, it is also known as the Nehdenian, Hembergian, Dasbergian, and Wocklumian, though these do not match the international subdivisions exactly. In North America, the Famennian includes stages such as the Chautauquan, Canadaway, Conneaut, Conneautan, Conewango, and Conewangan.

Name and definition

The Famennian Stage was proposed in 1855 by Belgian geologist André Hubert Dumont and accepted in 1981. It is named after Famenne, a natural region in southern Belgium. The main reference point for the start of this stage was later set in 1993 within the Coumiac Formation near Cessenon in southern France.

Since 2017, scientists have used changes in tiny fossil creatures called conodonts to mark the beginning of the Famennian. They look for when certain types of conodonts, like Palmatolepis bogartensis, disappear and new ones, like Palmatolepis subperlobata, appear. Earlier ways to define this stage have been updated as scientists learned more.