The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.
Portrait of Alexandre Brongniart, who coined the term "Jurassic"
Folded Lower Jurassic limestone layers of the Doldenhorn nappe at Gasteretal, Switzerland
Middle Jurassic strata in Neuquén Province, Argentina
Tidwell Member of the Morrison Formation (Upper Jurassic), Colorado
The Triassic is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic.
Early Triassic sandstone (Buntsandstein) near Stadtroda, Germany
Middle Triassic Muschelkalk (shell-bearing limestone) near Dörzbach, Germany
Late Triassic Steigerwald Formation and overlying Hassberge Formation in Schönbuch, Germany
Sydney, Australia lies on Triassic shales and sandstones. Almost all of the exposed rocks around Sydney belong to the Triassic Sydney sandstone.
