Tournaisian

The Tournaisian is the oldest part of a major time period called the Mississippian, which itself is the earliest part of the Carboniferous era. In the science that helps us understand how long ago things happened, the Tournaisian is known as 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 have found two smaller parts within the Tournaisian. These are called the Hastarian, which is the earlier part, and the Ivorian, which is the later part. These names originally came from studies done in Europe.

Name and regional alternatives

The Tournaisian was named after the city of Tournai in Belgium. A Belgian scientist named André Hubert Dumont first used this name in scientific writing in 1832. Today, the Tournaisian is part of the international timeline used to study Earth's history.

This time period matches with different local 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, which is a major division in Earth's history. Scientists identify the start of the Tournaisian by looking for a special type of tiny, ancient creature called a conodont, specifically a form known as Siphonodella sulcata. This helps them know when this time period begins.

The Tournaisian can also be identified by looking at certain fossils, including a type of ancient sea creature called an ammonite. There are special areas where scientists study these fossils to learn more about this time long ago. The Tournaisian includes several layers defined by different groups of these tiny fossils, which help scientists understand the order of events during this ancient time.

Paleoenvironments

The Tournaisian was a time when there were very few fossils of land animals and plants, making 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, which would later become very common in coal forests.

In northern Asia, such as Kazakhstan and Siberia, there were different types of smaller plants that were not as large as those in the tropics.

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 understand what the Earth was like during this ancient time.