Bathonian

Bathonian is a standard stage of the Middle Jurassic epoch in the International Chronostratigraphic Chart. It spans roughly 168.3 to 166.1 million years ago, following the Bajocian and preceding the Callovian. The name derives from Bath, a city in Somerset, England, where rocks of this age were first studied in the 19th century.

The lower boundary of the Bathonian is defined by stratigraphic markers tied to characteristic fossil horizons, while the upper boundary corresponds to a marker that aligns with the base of the Callovian. These boundaries are established to enable global correlation across regions that preserve Middle Jurassic sediments.

Palaeogeographically, the Bathonian was a time of relatively warm global conditions with high sea levels. Widespread shallow seas covered large parts of Europe and other continents, producing extensive marine sedimentation. Continental regions supported forests and a variety of terrestrial life, contributing to a diverse fossil record.

The Bathonian is well represented in the fossil record by marine invertebrates, especially ammonites, belemnites, and brachiopods, which provide the key biostratigraphic markers used for correlation. Fossil floras and occasional terrestrial vertebrate remains are known from some locales, illustrating a ecosystem that included both flourishing marine environments and expanding land habitats.

In geology and paleontology, the Bathonian serves as a useful horizon for regional correlations across Europe and other basins. It helps researchers reconstruct Middle Jurassic environments and the evolution of marine and terrestrial life during this interval.