The Prehistoric Potteries

The Carboniferous landscape

The geological history of Stoke-on-Trent began over 300 million years ago in the Carboniferous period of the Palaeozoic era. At that time, the geological layers that today form part of the substrata of modern Britain were part of a giant landmass, the mighty super-continent of Pangaea. Over the eons Pangaea broke apart and millions of years more of creeping continental drift  moved one of its large fragments, the future continent of Europe, into the temperate climes of the northern hemisphere that it occupies today. In the Carboniferous period, however, Britain and its near neighbours lay in the tropics, just south of the equator and the land that now forms North Staffordshire was part of an extended coastal region. Lying where it did, the surface of the land here fluctuated just above or just below sea level, a situation which produced the varied deposits that make up the modern geology of North Staffordshire. 

The earliest of this local strata, comprising millstone grit and early sandstone, were laid down as thick oozing sediments on the prehistoric ocean floor. Occasionally, every million years or so, these accumulating layers would form into a delta, which pushed itself above sea level. Here, once a layer of earth had been laid down, peat deposits formed from vast steamy jungles of prehistoric plants that quickly colonised the swampy flood plains. Eventually, though, the sea returned, the plants died and the jungle floor silted over, entombing the lower layers in the geological record. As the aeons passed, the accumulating sediments once again clogged the shoreline, turning it in time into a swamp once more. This natural cycle, repeated itself many times during the 65 million years of the Carboniferous period and over time heat and pressure would squeeze the water out of the accumulating layers and crush them solid. Mud, silt and sand became shale, siltstone and sandstone. The layer of earth that had covered the raised delta, was transformed into seat earth, from which fireclay formed, while the millions of years worth of accumulated peat that lay above it, was over time compacted into rich seams of coal.

About 285 million years ago, however, this cycle came to an end. Conditions changed drastically, the land rose and most of the jungles disappeared. It was during this period that the thick band of common clay, the so-called Etruria marl, which with the coal measures later assured the rise of the Staffordshire pottery industry, was laid down as a reddish sediment that filtered into the remaining coastal lagoons. The climate then grew much hotter, turning the jungles to deserts, the sands of which now form the Triassic sandstones of Staffordshire, such as may be seen at Park Hall and Trentham. Later in the Triassic period, however, the waters returned once again, covering the deserts and Staffordshire spent the bulk of the Mesozoic era, the age of the dinosaurs, at the bottom of a warm, shallow sea.

Many millions of years later, when the seas had subsided and the land had been folded up by movements in the earth’s crust, the upper layers were periodically raked by the passage of ice sheets. The coming and going of these glaciers had a number of effects on the area. They gouged out valleys and dropped 'erratics' or large boulders all over the district, a notable example of which (seen here) until a few years ago used to sit outside the Staffordshire University Film Theatre in Stoke. 

The passage of the glaciers also exposed the ancient shoreline deposits, bringing a wealth of raw materials within easy reach. These deposits have also yielded a great many fossils, revealing the variety of animal life that once walked, or swam, over the Potteries. Though no dinosaur bones have been discovered, the fossilised remains of various ancient fish, lizards and some prehistoric mammals, have been found within the confines of the City of Stoke on Trent. For instance, there are the remains of prehistoric sharks that once swam over what is now Longton and Fenton. Mammoth bones have also been unearthed. In his Natural History of Staffordshire, published in 1686, Dr Robert Plot describes the jaw and tooth of a ‘young elephant’, that was found in a marl pit on the Leverson Gower estate in Trentham. Plot, living in an age where natural history was a very patchy science, believed this to be the remains of a modern elephant that had been brought to England and perhaps kept for prestige and entertainment of a local lord, though this seems very unlikely. More bones and tusks have been discovered in Stoke Road, Shelton and in another marl pit in Fenton. In 1877, when the course of the Fowlea Brook, near Etruria Station was being altered, the skull and horn cores of a Bos taurus primogenous, or auroch, a prehistoric wild ox, much larger than a modern-day bison, was discovered. According to Josiah Wedgwood, many fossils were unearthed by James Brindley’s men when they were cutting the Grand Junction Canal, but nothing of these remains save for the briefest mention of various plant impressions and the finding of a rib from some giant unknown animal.