Thursday 22 October 2015

The Roundhay Park Fault


A view across the Roundhay Park Fault to the Rough Rock

Arriving in Leeds from the south, the gentle dip and scarp topography formed by the Coal Measures strata fades away into the Aire Valley, with much of the city being quite low lying; however, the topography changes quite dramatically to the north, with a thick slab of the Elland Flags rising above the city to form higher ground around Oakwood and Roundhay.

Roundhay Park Gorge

Wandering around Roundhay Park to take in the landscape, the original water courses have obviously been obscured by the artificial lakes; however, the topography records the erosion of the Elland Flags – and the Rough Rock – along with their associated softer siltstone and shale, to form various gentle escarpments and vales.

A view across the Roundhay Park Fault to the Elland Flags

The meandering brook, now gently flowing through Roundhay Park Gorge, doesn't have the erosional power to have created the steep sided valley that now exists and this provides evidence that fast flowing glacial meltwater - in Quaternary times - once cut through the hard rock.

A Geological Map of the British Islands

Looking at a Geological Map of the British Islands that hangs on my office wall – the 1969 edition, at the scale of 25 miles to the inch – there is a very distinct break between the Coal Measures and the Millstone Grit, which I have often wondered about.

Folded Carboniferous siltstone and shale

In South Yorkshire, and the parts of West Yorkshire that I had previously visited, the Coal Measures strata generally dip in a north-easterly direction – at Roundhay Park, the sharp change in the landscape to the north of Victoria Park can be partially explained by the appearance of the Roundhay Park Fault.

The geology around Roundhay Park

The Castle at Roundhay Park provides yet another unexpected insight into the variety of geology that can be found around this part of West Yorkshire - to the east, there is a deposit of Quaternary glacial till, which is the source of cobbles of Carboniferous sandstone used in its construction.

The Castle at Roundhay Park