Sinemurian

Sinemurian

The Sinemurian was an important time in Earth's history. It was part of the Early Jurassic Epoch. It lasted from about 199.5 million years ago to 192.9 million years ago. Scientists use the Sinemurian to help organize and understand what happened long ago.

Right before the Sinemurian was the Hettangian period. After the Sinemurian came the Pliensbachian. These periods help scientists study changes in life and Earth's surface.

In Europe, especially in Great Britain, rocks from the Sinemurian and Hettangian are grouped together. They are called the lower Lias. In Britain, these rocks are well known as the Blue Lias. This name comes from the blue-gray layers often seen in Jurassic rock formations.

Stratigraphic definitions

The Sinemurian Stage was named by a French scientist, Alcide d'Orbigny, in 1842. It is named after the town of Semur-en-Auxois in France. This area has special rocky soil made from old limestone.

Scientists start the Sinemurian by looking for certain ancient sea creatures called ammonites, like the groups Vermiceras and Metophioceras. A key point for this stage is found in a cliff near East Quantoxhead in England. The end of the Sinemurian is marked by other ammonites, such as Bifericeras donovani and Apoderoceras.