Lincolnshire Limestone Formation
The Lincolnshire Limestone Formation is a geological formation in England, part of the Inferior Oolite Group of the (Bajocian) Middle Jurassic strata of eastern England. It was formed around 170 million years ago, in a shallow, warm sea on the margin of the London Platform and has estuarine beds above and below it.
Source: Wikipedia — Lincolnshire Limestone Formation (CC BY-SA 4.0)