As I celebrate my 45th orbit of the sun, it would seem appropriate that one old fossil gets to visit some other old fossils, so today finds us extreme dog walking deep into Derbyshire at the limestone deposits of Steeplehouse Quarry by the National Stone Centre. This 50 acre site at Wirksworth on the edge of the Peak District is of special scientific interest for its geological features and quarry fossils.
That’s because approx 330 million years ago, just before the formation of the Pangea super-continent, Britain was much closer to the equator and this area was a lagoon, a shallow sea bed with a much more tropical climate. Today, these rocks are made from limestone (calcium carbonate), carboniferous rocks from the Eyam Limestone Formation (Dinantian age) are full of crinoids and brachiopods, the shelly remains of of billions of animals. carboniferous means coal-bearing and a time when large amounts of coal deposits were formed (you’re burning up your ancestors…).
Some of the fossils are more intact with hollows in the rocks that are impressions made by brachipods. They were bi-valve creatures (with two half shells), like a clam where they lived on the calm sea bed away from strong currents and waves. They were once as abundant as shellfish today and there are plenty of broken up remains in the rock face. They became virtually extinct 250 million years ago during the Permian mass extinction, often know as the Great Dying. The end of the Permian period was marked by the biggest mass extinction event of the last 600 million years of which 95% of all species on Earth died out. C’est la vie. Or not.
Walking further along the quarry, we come across a mass of of dark grey rock that formed the back slope of a reef that sheltered the lagoon from open sea. Clearly visible in the quarry fossils are the mass remains of Crinoids, a creature related to modern starfish and often called sea-lilies due to their resemblance to plants. Crinoids are the most common fossil in this quarry and used to feed by sieving seawater with their fronds and filtering plankton. They were attached to the seabed by a long stem and grew in large colonies where their main predators, sharks, attacked their calyxes which was the main body of the animal. Crinoid stems were made up of small rings of calcite known as columnals or ossicles which are preserved more easily, held together by soft tissue like skin and the slope in front of us shows many large unbroken crinoid stems.
While we did not collect any actual specimens, it feels a little disrespectful to bash these quarry fossils with a hammer when they’ve been quite happily sat there for the past few hundred million years, aside from the unfortunate Great Dying of course. It’s still a far more successful fossil hunt than our last attempt near here, although we’ve not seen this much stone since our Nerdy Neolithic Monster Megalithic Monument Tour last year. Then again we didn’t have Nelson with us that time and today he’s taught us to never underestimate your dogs ability to sniff out ancient fossils, a mere 330 million years old and wee on them with utter contempt. By the way, fossil, comes form the Latin word fossilis means ‘dug up’ which is what I’ll be in danger of if I drag Mrs C to anymore abandoned quarries.