Are you planning on visiting the City of Bath? Maybe seek out the Bridgerton filming locations, enjoy a Sally Lunn Bun or simply kick-back and indulge in a two-hour spa session in the mineral-rich waters of Thermae Bath Spa. Whatever you are doing consider this over your cocktail that much of the city’s Bath Stone that built the skyline of Bath dates back to the Jurassic Period.
Described as a city set within its natural landscape this UNESCO World Heritage Site is principally known for its Roman thermal spa and hot baths at “Aquae Sulis” as well for its elegant Georgian period neoclassical Palladian buildings, terraces and crescents. The historic buildings of Bath owe their beauty to the extensive use of local stone known as Bath Stone.
The geology surrounding the City of Bath and the area of Avon is complex and dominated by sedimentary rocks dating from the early Ordovician to the late Jurassic with an influence of volcanic activity creating a number of unconformities, faults and a complicated outcrop topography of inliers, outliers and hot springs.
During the Jurassic Period the second of the three periods of the Mesozoic Era dating between 201.3 – 145 million years ago the area of Bath was once a small part of the hot desert interior of the supercontinent of Pangaea was submerged by a shallow warm tropical sea.
Roman thermal spa and hot baths at “Aquae Sulis”
Between 168.3 million and 166.1 million years ago during the Bathonian Stage, named after the City of Bath, of the Middle Jurassic epoch the variations of Bath Stone known as the Chalfield Oolite Formation, of which the Bath Oolite and the Combe Down Oolite are members, within the Great Oolite Group were formed. Bath Stone is recognisable in the city by its subtle, warm, honey colouring.
The word “oolitic” comes for the Greek word "òoion” meaning egg and “líthos” meaning stone formed from grains of calcium carbonate. The calcium carbonate was derived from the shell remains bivalves, brachiopods and corals. Ooids have a diameter between 0.25 – 2 mm and have concentric layers developed around a nucleus cemented together with calcite.
The rolling motion Ooids allows for their growth of concentric layers of carbonate, resulting in the formation of ooliths. Over time they became compressed to form oolitic limestone and subsequently in this specific case Bath Stone.
Bath Stone is a freestone meaning that it has a uniformity ideal for building grandeur architecture as it can be worked, cut or squared in any direction without compromising its strength.
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