Bicentenary of the Chalk (and Coal

Two hundred years ago in 1822, Jean d’Halloy, a Belgian pioneer geologist and anthropologist, formally proposed that the chalk in France belonged to such a distinct kind of ancient rock with ammonite shells that it should lend its name (in latin, creta) to a new geological division – the Crétacé. In the following decades, the Cretaceous Period of Earth history was also recognised in England, and there is indeed a chalk ammonite at the bottom of Seaford Head (image above). By the turn of the century, our local chalk (image left) was being explored in considerable detail in order to compare with the French chalk and beyond (Seaford Scene February, 2016, issue 106, page 28). With the discovery of the Earth’s natural radioactivity in the last century, we learnt that the Cretaceous was 66 to 145 million years ago, and was longer than the length of time since the Cretaceous Period ended!

The Cretaceous proved not all chalky, however, and came to include the clays and sandstones of the Weald, as well as the chalk of the North and South Downs. The clays contain ironstone and the iron grave marker in St Leonard’s Churchyard (image right) is a reminder that South-East England was once the centre of Britain’s iron industry when fuelled by charcoal from the forest. The end was nigh, however, when also in 1822, William Conybeare, West Country curate and lecturer, proposed the ‘Carboniferous Period’, with its focus on coal – which now shifted the industry to the English Midlands. At the same time, he recognized the ‘Weald Clay Formation’ (image left) which later became renowned for its dinosaurs and even fossil insects (image below), as well as for making bricks and tiles.

In the stone age, the chalk produced another historic raw material – flint, for making tools before metals were known. Next month, we commemorate the Dieppe Raid that was in the summer 80 years ago. Unfortunately, the abundant flint pebbles on the beaches of Dieppe, unlike here, slowed down the advance of our new tanks in support of the infantry. This was not fully anticipated, as our beach pebble supply had been blocked by the Victorian quay building in Newhaven, which had created a new pebble rather than flint-land there instead (image below). Being light in weight, the brown coal (strombolo)

from West Sussex nevertheless still washes up onto the beach at Seaford (image right). As in China today, it was once used for carving and rough-outs for Celtic bracelets,

resembling lost fishing gear, which occasionally still wash up after storms (image left, 20p for scale). No Carboniferous coal has been found in Sussex, unlike in the Midlands, but tradition has it that Mary Mantell came across the Iguanodon in 1822 (first vegetarian dinosaur) – it was a memorable year! Biddy and Ed Jarzembowski