Views from the No. 272 Bus

The 272 bus from Sheffield to Castleton

Having spent a day out, walking around the Burbage Valley to look at some of the gritstone edges in the Dark Peak of South Yorkshire, a couple of weeks later I took advantage of the 272 bus again – to venture further into the White Peak of Derbyshire.

Surprise View

At Fox House, the bus turns right and heads off towards Hathersage down the escarpment, which is formed by the erosion of the Chatsworth Grit and the underlying beds of much softer siltstone and shale.

Winding around Millstone Edge, the aptly named Surprise View appears very suddenly - with the course of the River Derwent seen down in the valley below and the Kinderscout Grit and Shale Grit looming in the distance.

A plateau formed from these rocks, which are older than the Chatsworth Grit, can be seen from the main road along the Hope Valley but, turning off into Bradwell and passing over the low lying Bowland Shale, the geology changes abruptly to Carboniferous Limestone.

The Kinderscout Grit and Shale Grit

Bradwell is set on the very edge of the White Peak but, from my position on the top deck of the bus, I couldn't see any outcrops of limestone whilst passing through the village; however, the basic stone walling for the vernacular architecture and church reflects the underlying geology and contrasts with the sandstone that is used for quoins, lintels and other stone dressings - which provide structural integrity to the buildings.

Ecclesiastical and vernacular architecture in the Hope Valley

Burbage Rocks

A view across a spring line in the Burbage Valley

Various sedimentary structures can be seen at Carl Wark and Higger Tor, in the fallen rocks and when peering out along the crags; however, at Burbage Rocks, the foreset and top set beds - deposited in an ancient deltaic environment - are spectacularly exposed along its length.

Large scale sedimentary structures at Burbage Rocks

Like all the other gritstone edges, it is popular with rock climbers but it is easy to get up close to the vertical crags and look at the rocks in greater detail.

On this occasion, I preferred to see them from the path that runs parallel to the edge and below the blockfield.

In all of the blocks found off the path, there are plenty of opportunities to look at the coarse sandstone - comprising sub-angular grains of quartz, with weathered feldspar and mica - as well as abundant pebbles of vein quartz.

Walking further along the edge, two sets of joints running at right angles to each other are clearly visible – one runs parallel to the edge and the other cuts into the rock face – and in places they are eroded to produce buttress like overhangs that offer a severe challenge to the rock climbers.

Structural geology in the Burbage Valley

It might be easy to miss, when looking at such a spectacular skyline, but the path coincides with a spring line, where the upper leaf of the Chatsworth Grit meets the underlying shale.

Although this natural feature is partially obscured by the path, the occurrence of the springs is marked by a very noticeable change in the vegetation.

In mid-September, both the heather and the  bracken are at the height of their growth and dominate the other plants.

Sphagnum moss, however, is in its element in such boggy conditions and - once you look beneath the distinctive grass like stems of the sporophytes that appear to have died off at this time of the year - it is clearly visible.

Sphagnum moss

With the length of my Geotour around the Burbage Valley being determined by the hourly bus timetable, I could have spent an extra hour exploring an old quarry where millstones were once made and then walked back up to Fox House to have a well earned drink; however, having spent just over 4 hours between arriving and departing, I decided that this 5 mile walk in the Peak District was enough for one day and headed back into Sheffield instead.

Putting my feet up at a traveller's rest in Sheffield

Burbage Brook

A view of Burbage Brook on the approach to Carl Wark

On the way to Carl Wark, Burbage Brook is seen to meander through thick deposits of head, which occupies the wide valley floor; this comprises loam - clay, sand and gravel – which is packed full of blocks of gritstone and was largely formed by solifluction in a periglacial climate.

The Burbage Valley

Although mostly obscured by head, the valley cuts through the Chatsworth Grit into the Marsden Formation - siltstone and mudstone that were formed in marginal coastal plains - with lakes and swamps periodically inundated by the sea.

Shale and siltstone

The marine bands that are found within this formation contain goniatites, which are used as index fossils to correlate strata and were once important for coal mining in the UK. Depending on the water level of the brook and the thickness of the vegetation covering its banks, there are various exposures of shale to be seen; however, fossils are very rarely found here.

A view of Burbage Bridge

Seen from Higger Tor, Burbage Brook steepens considerably towards the head of the valley. At Burbage Bridge, there are actually two streams that converge to cut a distinct v-shaped profile  - forming cataracts over the blocky scree that lies immediately below the Chatsworth Grit...

 

Burbage Brook

Higger Tor

A view of Higger Tor from Carl Wark

Viewed from Carl Wark, the plateau like Higger Tor – capped by the coarse, pebbly upper leaf of the Chatsworth Grit – is 45 metres higher than the equivalent rocks that you are standing on and cannot be accounted for by the dip of the strata. It is the result of a fault that traverses the Burbage Valley and can also be seen in the gritstone edge towards the southern end of Burbage Rocks.

A general view of Higger Tor

By the time that I had finished looking around Carl Wark, I was accompanied by numerous other casual visitors, as well as the participants in a fell running race, and so I walked quickly up to Higger Tor, noting a variety of other similar rocks, and stopped only very briefly to look closely at a soil horizon.

Somewhere on my walk, presumably whilst steadying myself on one of the many slippery or rocky slopes, muddy water had splashed onto my camera lens – much to my annoyance.

Higger Tor

Although I noticed this when I sat down for a bite to eat, many of my views of Higger Tor were spoiled – especially updates of those I had previously taken with colour transparency film and which I have frequently used for publicity - and to illustrate various talks on the geology and architecture of South Yorkshire and the Peak District.

Everywhere on this walk there is evidence of the powerful rivers that flowed into the deltas, which existed in Namurian times - and the all round views are quite stunning. Boggy areas, with peat, cover much of the top of Higger Tor and although I didn’t include this site as part of my walk - from a distance - the slumped shales found beneath the lower leaf of the Chatsworth Grit can clearly be seen.

An example of slumped shales in the Peak District National Park