Tournaisian

The Tournaisian is the oldest part of a major time period called the Mississippian. It is the earliest part of the Carboniferous era. In science, the Tournaisian is called a "stage." This means it is one of the smallest pieces we use to divide up deep time. The Tournaisian lasted from about 358.86 million years ago to 346.7 million years ago.

Before the Tournaisian came the Famennian, the last part of the Devonian period. After the Tournaisian came another stage called the Viséan. Scientists who study rocks and fossils found two smaller parts within the Tournaisian. These are called the Hastarian, the earlier part, and the Ivorian, the later part. These names came from studies done in Europe.

Name and regional alternatives

The Tournaisian was named after the city of Tournai in Belgium. A scientist from Belgium, André Hubert Dumont, first used this name in a science book in 1832. Now, the Tournaisian is part of the timeline scientists use to study Earth’s history.

This time period has different names in other parts of the world. In North America, it is called the Kinderhookian and lower Osagean stages. In China, it is known as the Tangbagouan stage. In the British Isles, the Tournaisian is sometimes called the Courceyan stage.

Stratigraphy

The Tournaisian is the earliest part of the Carboniferous period. This is an important time in Earth's history. Scientists find the start of the Tournaisian by looking for a special tiny, ancient creature called a conodont. They look for a form known as Siphonodella sulcata. This helps them know when this time period begins.

The Tournaisian can also be found by looking at certain fossils. These include a type of ancient sea creature called an ammonite. Scientists study these fossils in special areas to learn more about this ancient time. The Tournaisian has several layers. These layers are defined by different groups of tiny fossils. They help scientists understand the order of events from long ago.

Paleoenvironments

The Tournaisian was a time when there were very few fossils of land animals and plants. This made it a gap between the older Devonian period and the Carboniferous period that followed. During this time, South America was near the South Pole and part of a large landmass called Gondwana. The coasts of this area had many types of sea creatures.

Forests and swamps were not very common during the Tournaisian, even though some trees grew very tall—up to 40 meters or 131 feet. Rivers during this time looked more like those from the Devonian period than the ones that came later.

Flora

The Tournaisian saw many new types of large plants, such as tree-like lycophytes and giant sphenophytes, also known as horsetails. These plants grew alongside ferns and early wood-bearing plants, including the first seed plants. Some of these early seed plants were called "seed ferns."

In places that are now Europe, North America, and China, there were swamps filled with many types of plants. One common plant was a large lycophyte named Lepidodendron.

In northern Asia, such as Kazakhstan and Siberia, there were different types of smaller plants.

Invertebrates

Trilobites, an ancient type of sea creature, had one of their last big moments of growth during the Tournaisian. Most of these new trilobites belonged to a group called Phillipsiidae. At first, they lived in deep water, but later they moved to shallower areas and spread across different parts of the world, including North America, Europe, and East Asia.

Notable formations

Some important rock layers from the Tournaisian time include the Albert Formation in New Brunswick, Canada, and the Agua de Lucho Formation in Argentina. Other notable formations are the Ballagan Formation and Cementstone Group in Scotland, the Herbesskaya Formation in Russia, and the Horton Bluff Formation in Nova Scotia, Canada. We also find the Mansfield Group in Australia, the Price Formation in West Virginia and Virginia in the United States, and the Tournai Formation in Belgium. These formations help scientists learn about the Earth during this ancient time.