A day at Tideswell, Derbyshire, with the OU Geological Society

Studying geology isn't just about reading books. To really get to grips with the subject you simply have to get out in the open air. With this in mind I recently joined the East Midlands branch of the Open University Geological Society, with the aim of getting a bit of practical geology experience, before I dive head first into the level 2 geology couse with the university.

So, the ‘Basic Geology Day’ at Tideswell, Derbyshire (click here for a map of the area) sounded like the perfect introduction for a relative beginner like me. It was designed to give people like me a gentle introduction to sedimentary and igneous rocks. S276, the geology course is all part of my master plan to get a geology based degree sometime before senility creeps in, but is not likely to figure until next year. The first question was, would I be out of my depth? Would an unintensional 'faux pas' see me ridiculed in such educated company? Not a bit of it! I was made to feel welcome right from the off and able to ask any question I felt necessary.

A group of eight gathered in the car park at the old railway station at Millers Dale which comprised four committee members and four ‘newbies’ of varying levels of geological experience. Not only was this my first geology field trip, but it was also the first outing for my brand new walking boots bought specially for this very day - quite obvious to all probably as said boots were quite unfeasibly shiny!

Anyway, after brief introductions, it was off on a short walk to the first stop – a limestone quarry, where Don Cameron, the group leader, described the ‘Derbyshire Dome’. Around 300 million years ago, the sea floor was lifted and a gentle anticline formed across what is now the Peak District, giving the area the characteristic 'dome' shape, hence the name. Folding of the rocks caused cracks (faults) to appear, particularly so within the limestone.

From the top down, the sequence of rocks present are coal measures; millstone grit; shale and limestone. The coal measures and millstone grit were then subject to erosion and at the most exposed upper part of the dome the gritstone was completely removed thus exposing the limestone in the centre of the Peak District.

A former Limestone quarry, Millers Dale Derbyshire.

Don suggested we all take a look at some of the rocks lying around the base of the quarry and seen in the foreground of the above photo. I was of course aware of the fossil content of limestone but not how numerous they can be. The rock that I examined was packed with vast numbers of brachiopods, rugose corals and crinoid stem fragments of varying sizes.

Limestone containing fossil coral (upper centre)

I won’t give you a detailed description of the geology of the day for fear of getting something hopelessly wrong and embarrassing myself, but what this day emphasised for me was that it doesn’t matter how much studying and reading you do at home or in a college, nothing quite matches seeing things out there in the great outdoors. Even something as straight forward as a fault or an unconformity means so much more when you see it with your own eyes and in three dimensions.

A fault line in the limestone caused during the formation of the anticline.

The day finished off with a quick drive up the road to take a look at a doloritic intrusion at Tideswell Dale Quarry, which was well worth the extra short drive. Here, hot liquid rock deep within the earth slowly cooled allowing fairly large crystals to develope forming the dark rock characteristic of dolerite.

Exposure of a dolerite intrusion, Tideswell Dale Quarry, Derbyshire.

Close up of the dolerite intrusion, Tideswell Dale Quarry, Derbyshire.

Close up of a recent rock fall at the exposure.

Some rocks (lower centre) exhibit severe weathering

and a redish colouration due to their iron content.

View towards Froggatt Edge (I think) which denotes the edge of the Millstone Grit.

To the left of the peak, lies shale and limestone.

So all in all, a fascinating intro to geology and the OU Geological Society. Sadly, I can’t make the next trip to The Roaches this Saturday (due to 50th birthday celebrations!), but I will definitely make the (for me) short journey to Bradgate Park in June to find out more about the oldest rocks in England.

Me and my boots can't wait!

Cheers, Alyn