The Bathonian Stage of the Middle Jurassic
Just like a book is divided up into chapters so geological time is divided up into a series of units. There are Eons, Eras, Periods, Epochs, and faunal stages, these are the typical units of division when it comes to exploring the geological timescale. A point reinforced when a team member from Everything Dinosaur made a visit to Somerset recently.
Descending order of size for the units of the geological timescale (deep time):
- Eon for example, the Phanerozoic (visible life) from 542 mya to the present day.
- Era for example, the Mesozoic, from 251 mya to 66 mya) or thereabouts.
- Period, for example, the Jurassic (199 mya to 145 mya) approximately.
- Epochs, for example, the Middle Jurassic (175 mya -161 mya) approximately.
- Stages or Ages such as the Bathonian (167.7 mya to 164.7 mya) approximately.
We mention this, as whilst working with Year 6 children and their teachers in the Bath area, we explained that the limestone rocks in their part of the world, were used as building materials and have been quarried for centuries. Many of the buildings around the school, and the walls of the school were constructed using these limestones. These limestones are the preserved remains of the shells of ancient sea creatures, that lived during the Jurassic. The Bathonian faunal stage was named after the spa town of Bath and the limestone found in this part of south-western England. It was included in scientific literature as early as 1843. A number of ammonite species are recognised from this Middle Jurassic strata and they help to provide a biostratigraphic profile and assist with relative ageing of the rocks. Bathonian rocks have provided a number of dinosaur fossil remains including sauropods, armoured dinosaurs, meat-eaters and even a distant relative of the most famous dinosaur of all Tyrannosaurus rex (Proceratosaurus).
Typical Bathonian Limestones used as Local Building Materials
It was a nice moment to ask the school children did they want to see something from the Jurassic? When they all said yes, we simply asked them to look out of the window.