Carboniferous Geology in Roundhay Park

Remembering my old running, cycling, tree-climbing haunt of Roundhay Park (North Leeds) today I thought I'd show some pictures related to the geology of the place. Firstly here's a GoogleEarth view of the northern end of Waterloo Lake, with "The Folly" at the top of the grassy slope and "The Gorge" snaking away beneath the sea of trees.

And here below is a sketch map I made about a decade ago for a guided tour. The tour started at the outlet of the upper lake (1), went past the folly (at 2) then along the West side of the gorge before descending to the stream and continuing back down the gorge (3 and 4) towards Waterloo Lake.

You'll see there's a fault, shown in red, where the gorge meets Waterloo Lake, with Elland Flags to the South and Rough Rock with Millstone Grit mudstones to the North.

The vertical order of the different rock types is shown in the following sketch:

Looking back at the sketch map you'll see that the younger (Westphalian) Elland Flags have been faulted down to the South to lie next to the older (Namurian) Rough Rock sandstones and underlying mudstones.

A couple of "marine bands" are shown on the sketch of the vertical section and they are fun because they contain marine fossils. Here is a piece of shale from the gorge containing fossils of long-extinct goniatites, something a bit like modern nautilus.

These are from the Cancelloceras cumbriense marine band and are just a few cm across. Fully grown examples could reach about 10 cm across.

You can also find scallop-like bivalved molluscs, like these Dunbarellas, in the marine bands:

Imagine these animals alive in an ancient tropical Yorkshire sea:

The bit of Earth called Yorkshire these days was very close to the equator when these animals were alive, a little over 300 million years ago (about 315-317 Ma). The climate in this part of the world was a little different then and a good place to get a feel for what it might have been like is tropical West Central Africa.

If you ever do this walk along the gorge and around the lake you could finish off with a visit to "Tropical World" by the entrance to the park and get a hint of a flavour of that ancient Carboniferous Leeds.


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