Floian

The Floian is an important time period from Earth's past called the second stage of the Ordovician Period. It came after the Tremadocian stage and, together with it, makes up what we call the Lower Ordovician series. Before the Floian was the Dapingian Stage, which is part of the Middle Ordovician.

The Floian lasted from about 477.1 to 471.3 million years ago. Scientists mark the beginning of this stage by looking for the first appearance of a special type of ancient sea creature called a graptolite. This particular graptolite is known as Tetragraptus approximatus. Studying the Floian helps us learn about how life on Earth developed many millions of years ago.

History and naming

The Floian Stage was officially approved in 2002 by the International Commission on Stratigraphy. It is named after the village of Flo in Västergötland, southern Sweden. The name "Floan" was suggested in 2004, but the group chose to use Floian as the official name.

GSSP

The Floian stage begins where the lower Tøyen Shale is found in Diabasbrottet Quarry. This point marks when the tiny creature Tetragraptus approximatus first appears, about 2.1 meters above the rocks from the Cambrian time. Scientists have figured out that this change happened 477.1 million years ago.

The Floian ends where the creature Baltoniodus triangularis first shows up. This happens in a place called Huanghuachang in Hubei Province, China.

Regional stages

In some places, the Floian stage is similar to other stages with different names. In Baltoscandia, the Hunneberg stage (lower) and Billingen stage (upper) are like the Floian. On the Siberian Platform, the Ugorian stage matches the Floian.

Major events

During the Early Floian age, a big change in the oceans happened called the global Billingen Transgressive Event. This event is linked to special kinds of rocks found in places like Gorny Altai and Salair in Russia, including black graptolitic argillites, conglomerates, and gritstones.

Paleontology

Scientists have found very old fossils in rocks from the Floian time in Newfoundland. These fossils, which look like corals, show that early sea environments were already quite developed.

During the Floian age, tiny ancient sea creatures called conodonts lived in places such as Kazakhstan, Korea, China, Indochina, and Australasia. Other special fossils called graptolites were found in Sweden, mainly in shallow water. Scientists also discovered trilobites, which were small sea creatures with hard shells, in northwest China. Additionally, a strange fossil named Falloaster anquiroisitus was found in the USA.