Geology at Wincobank Hill

 

A specimen of Silkstone Rock from Wincobank Hill

On the LIDAR map, the ridge of Silkstone Rock upon which Wincobank Iron Age Hillfort is set is clearly visible, with its ramparts effectively occupying the whole summit and overlooking steeply sloping ground on either side.

 

A LIDAR map of Wincobank Hill

Continuing my walk down towards Wincobank Wood, most of the views to either side of the ridge were largely obscured by trees but, before long, the ridge narrows markedly and the steep sided slopes are easy to see from the path.

 

Silkstone Rock exposed along the path

In the well worn path, the occasional rocky projection soon turns into small but distinct sheets of flaggy sandstone of no great durability, which outcrop beneath and around the path for a considerable distance along the ridge.

 

Steeply dipping strata

This extensive exposure of Silkstone Rock was completely unexpected and, everywhere I looked, there were obvious signs of the presence of the Don Monocline, with the strata marked on the British Geological Survey map as dipping as much as 30 degrees to the south-east.

 

A broad expanse of Silkstone Rock along the path

The sheets of flaggy sandstones are pervaded by irregular jointing, which is often quite small in scale and breaks the rock into fragments that are easily weathered and eroded, both by the elements and the walkers that traverse the path.

 

A detail of the Silkstone Rock

In several places, I stopped to take photographs of the various outcrops but I found it very difficult to capture the nature of the landscape that I could see around me or the steepness of the slopes just to either side of the path.

 

Steeply dipping Silkstone Rock

I collected a few samples from different places along the path, which steepens noticeably to the south-west and these are all fine grained and grey/light brown in colour, with iron staining where the sandstone has weathered along the joints.

 

Specimens of Silkstone Rock from Wincobank Hill

The larger sample, taken from one of the more competent beds, has well developed laminations that are rich in iron oxides/hydroxides and, although I saw no nodules of ironstone anywhere, iron slag has been found near Wincobank Hillfort and geophysical evidence suggests that ironworking may have taken place in the fort itself.

 

A specimen of Silkstone Rock from Wincobank Hill

In post-medieval times, Wincobank Wood was worked for the coal and ironstone that occurs beneath the Silkstone Rock, as seen at nearby Kimberworth, along with charcoal burning and the production of white coal.

 

A panoramic view from Wincobank Hill

 

Stopping briefly to admire the panoramic views over north-east Sheffield, I continued down the path to a way marker, where I was curious to see directions to a place called Sandstone. Here, I met a couple who knew the area well and we talked for ages about the area around Wincobank Hillfort, before I set off to Grimesthorpe.

 

A waymarker