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| Fossil bivalves |
My exploration of the Jurassic Trail in Leeds, in the middle of August 2021, was followed five days later by another trip to Leeds – this time with the Sheffield U3A Geology Group, to explore the geology around Roundhay Park.
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| A Walk Back in Time |
Back in 2015, I had a good walk around Roundhay Park during a day out to Leeds and noted some interesting historic buildings, follies and a few geological features along The Gorge, but I was unable to obtain a copy of Roundhay Park – A Walk Back in Time, produced by Bill Fraser of the Leeds Geological Association.
For most of our trips, the Group uses various books, guides and leaflets that members have collected over the years - to plan the walks - and the Group field trip leader of the day would lead us around using one of these; however, on this occasion it was arranged for Bill himself to lead more than twenty of us around Roundhay Park – starting at The Mansion House.
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| Gathering at the Mansion House |
Taking a path around the Upper Lake, which I had not previously explored, we saw various exposures of the thinly bedded Elland Flags from the Lower Coal Measures exposed in the streambed and then made our way to The Castle - a sham ruined castle gatehouse built for Thomas Nicholson, which is built out of large glaciofluvial cobbles from the nearby Quaternary Harrogate Till Formation, with gritstone for the dressings.
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| At The Castle |
Continuing to the top of The Gorge, we then followed the banks of the brook and stopped at numbered waymarkers, which correspond to the places of interest noted in A Walk Back in Time. Much to our great surprise, Bill then proceeded to unpack a large number of rocks and fossils that he had collected over the years from his rucksack, which we passed around the Group.
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| A goniatite |
The rocks that we looked at in The Gorge comprise sandstones, siltstones, mudstones and shales that are found beneath the Rough Rock, which is the uppermost named formation in the Millstone Grit Group but in reality are not much different to the sequences of rocks being laid down as the Pennine Lower Coal Measures Formation strata.
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| An exposure of shale in the streambank |
I didn’t take my Estwing hammer with me on this occasion and I gratefully received a few specimens of West Yorkshire sandstones and shales, which have been added to my rapidly growing collection of the rocks of Yorkshire and Derbyshire.
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| Various samples of rock from The Gorge |
Our next stop was at Scouts Quarry, where we inspected an exposure of the Rough Rock, which contains fingernail sized pebbles that were once rolled along the bottom of a massive river channel, in which dunes of coarse sand were also being pushed downstream.
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| Differential weathering of softer beds in the Rough Rock |
Of particular interest here is a soft sandy bed that has differentially weathered away to an arm’s length, which is a not feature of any of the exposures of coarse gritstone that I have seen around Derbyshire or Sheffield.
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| A Lepidodendron fossil |
Here, Bill retrieved yet another specimen from his rucksack, this time a piece of medium grained gritstone that contains a Lepidodendron fossil, which is more commonly found in the overlying Lower Coal Measures strata.
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| An exposure of the Elland Flags |
Continuing down the path along the stream, where we stopped at further examples of the Rough Rock, we then crossed the Roundhay Park Fault and eventually came to Waterloo Lake, where small exposures of the Elland Flags exhibit worm burrows on the bedding planes.
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| Worm burrows exposed on a bedding plane |
We finished our walk at the end of a surprisingly long day, by walking round the south end of the lake and heading back up to The Mansion, which I was told is built using a more massive variety of the Elland Flags - best known for its thinly bedded paving and roofing stone.
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| The east elevation of The Mansion |
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