The Physical Landscape of Graves Park The Geology:

The sequence of strata found within the boundaries of Graves Park includes typical sedimentary rocks including mudstones, ironstones, shales, siltstones and sandstones. The full sequence is illustrated in Figure 1. All these sediments are referred to as “Coal Measures” and are dated as belonging to the Upper Carboniferous period (see Figure 2).

Figure 1. Geological Sequence present in Graves Park

Two major sandstones, the Greenmoor Rock and the Sandstone, dominate the landscape of the Park creating the distinctive features of escarpment ridges and gently sloping dip-slopes which control the distribution of the soils and the cover of vegetation across the Park. Examination of the sandstone reveals that while they appear similar, in colour, they are different in composition.

The Greenmoor Rock has bands of fine to medium grained sand separated by layers of siltstone and mudstone. Outside of the Park, within the area, the sandstone has been quoted with thickness between 50 to 150 feet. It has been worked for building stone and for grindstones. Part of the outcrop has been quarried, along the south-western margin of the park, where about 6feet of the upper part of the sequence is very thinly bedded creating both ‘Flagstones’ (for paving) and as ‘Tilestones’ (for Roofing). Waste from the quarrying has been dumped over the edge thereby increasing the angle of slope and requiring the planting of beech trees to help to stabilise the slope. Associated mudstones and shales have been worked, outside of the park, in the past for the manufacture of bricks.

The Grenoside Sandstone tends to be more micaceous and has more clay minerals present. One key feature is that it tends to split readily along the bedding direction enabling large flat slabs of stone to be recovered for us as flagstones and tilestones. Some evidence is found within the Park for the use of these materials but there is limited evidence of actual quarrying of the stone inside.

fs/ch/march15 – photos Chris Percy Norton in the Heart of Chantrey Land 1

Westphalian B

Middle CoalMiddle

Measures Upper

Duckmantian

Thornhill Rock

Silesian

Wesrphalian A

Lower Coal

Measure

Carboniferous GRENOSIDE Langsettian SANDSTONE

GREENMOOR ROCK

Namurian

Millstone Rough Rock

Yeadonian Grit

Figure 2. Table indicating the age of the main sandstones

So what is the origin of these two sandstone beds? We know approximately when and where they formed but where did the material making up their composition come from and what was the site of deposition like at the time? To offer answers to these questions researchers, over the past 50 years, have closely examined the mineral composition of the sandstones and also the detail of structures found within them. The results of these investigations brought together two lines of enquiry, namely ‘Heavy Mineral Suites’ and ‘Palaeo-current Directions’.

Using the ‘Heavy Mineral Suites’ provides an indication of the minerals present in the parental source rocks from which the grains were liberated. The name ‘heavy mineral’ suggests that these mineral grains had a high specific gravity and were relatively hard thus able to prevent their destruction during transport from the source rock. The Palaeo-current directions provide an indication of the direction of flow of the river systems bringing the eroded debris to the site of accumulation and deposition. As the river reaches deeper water the flow rate reduces and so it tends to drop the sediment grains onto the lake or sea floor in a progressive style to create cross- bedding forms.

Using such evidence it is possible to suggest where the sand debris originated before being transported by, fluvial systems, to the depositional site in . The area where these deposits accumulated is within the Southern margin of the extensive Pennine Basin. This was surrounded by upland areas, to the north, the remains of the Caledonian Mountains (Laurentia), to the west the Lake District and Appalachia and to the south the Wales-Brabant high (Charnwood Forest). The basin where deposition was taking place comprised of extensive waterlogged plains, linked ultimately by a channel to the south and to the extensive open ocean. The whole basin tended, at times, to sink and become flooded by sea-water but at other times the basin filled up with sediments to form land. This allowed soils to form and vegetation to establish thus creating the diversity of sediment types, grouped together as ‘Coal Measures’.

fs/ch/march15 – photos Chris Percy Norton in the Heart of Chantrey Land 2

Figure 3. Rock outcrop within Graves Park.

Within the basin the sandstones were deposited in fluvial channels, levees and lacustrine deltas where cross-bedding is commonly visible and therefore can be used to indicate the direction of flow of the water transporting the sand grains. From the evidence accumulated it appears that the debris of the Greenmoor Rock came from the west where ancient sea-floor basalts and some metamorphosed sediments were actively being eroded.

The Grenoside Sandstone shows evidence that it was derived from the north where an ancient landmass, comprising metamorphic rocks and granites was present. Weathering of this landmass provided the detritus that was carried by the flowing waters into the depositional site of the Pennine Basin, of which Graves Park was a very small part. Deposition in the Pennine Basin continued for some 30 million years before the next major episode of Plate movement which saw the large plate of Pangea move south against the large plate of Gondwanaland. The result of this sequence of events was to create successive lines of fold-mountains aligned east to west between the respective plates. These fold- mountains extended from Russia, in the east, to Ohio (USA) in the west. In the UK we have the Pennines, aligned north to south and other folds aligned east to west from Kent through Bristol to South Wales and southern Ireland. Besides the large Pennine fold we have smaller folds along the eastern flank created due to forces of compression followed by relaxation and stretching. This has resulted in the folds, around Sheffield, of the Don Monocline (under Wincobank) then the Norton-Ridgeway Anticline, faulted on its southern flank from the Povey Syncline and the corresponding small Troway Anticline before reaching the much larger Dronfield Syncline. Thus the two sandstones in Graves Park are influenced by the Norton- Ridgeway fold causing them to dip towards the south-east at about 8 or 9 degrees.

For the past 290 million years the upland areas of the Pennines have been under constant periods of weathering and erosion, under different climatic regimes from arid dessert, through sub-tropical warm seas to clear shallow warm seas until the onset of the last Ice Age some 2 million years ago. There no evidence in Graves |Park of any ice coverage but one can assume that the whole area must have been subject to freezing temperatures creating extensive permafrost across the whole region. The end of the glacial period saw the thawing of the permafrost and the creation of a regolith of clayey debris covering the land. This material was the parent material from which the soils covering the region was formed. fs/ch/march15 – photos Chris Percy Norton in the Heart of Chantrey Land 3 The Landforms:

The landforms present today in Graves Park have a very long history because they are the product of two major events, namely the folding and uplifting of the bedrocks and then the extremely long period of weathering and erosion of that land area. The folding and uplift of the land has been referred to earlier when the movement of the plates caused the creation of major fold mountains by the compression of the collected sediments in the ocean basin, of which Britain was a part.

From the end of the Carboniferous period these fold-mountains were never covered by any younger deposits thus they have been at the mercy of the weathering and eroding agents for a very long time. The relative hardness of the sandstones allowed them to resist rapid erosion while the surrounding softer mudrocks eroded rapidly and allowed large river valleys to be created. In the case of Graves Park it was the development of the Sheaf valley which cut down through the sediments to reveal the sandstones on both sides. However due to the folding, the east side of the valley is steeper and creates typical escarpments while the west side is more gentle and equates to the dip of the strata (see Figure 4).

Figure 4. Geological Section through Graves Park

The area of Graves Park is located in the south of the . It is bounded to the west by the escarpment sloping down from BoleHill Farm to Road, a drop from 650 feet (a.o.l) down to 425 feet (a.o.l.). This escarpment is created by the outcrop of the Greenmoor Rock. It dominates the landform along the east-side of Woodseats Road before turning north across the Sheaf Valley towards Brincliffe Edge. The position and shape of the landforms is illustrated in the following cross-section of the Park

At the top of the escarpment, beyond Bolehill Farm the Park has a gentle slope towards the south-east with an average elevation of around 670 feet (a.o.l.). From the east-north-east a ridge over 700 feet high extends into the Park for about 500 yards. This feature is created by the outcrop of the younger Grenoside Sandstone. From the ridge the land slopes down into the small valley, aligned east-north-east to west-south-west, that carries a small stream which is the principal drainage channel of the Park. This stream has been dammed up at three locations to form small ponds, ideal for aquatic fauna. Along the southern side of this valley is a steep escarpment rising some 50 feet from the level of the ponds to the top, where the Rose Garden Cafe is located. It is created by the outcrop of the Grenoside Sandstone where, further along, to the east, is the site of . From this ridge the ground falls gently away towards the southern boundary of the Park with two smaller ridges created by outcrops of younger, un- named sandstones. fs/ch/march15 – photos Chris Percy Norton in the Heart of Chantrey Land 4

Figure 5. Watercourse through Graves Park

The main drainage of the Park is via a small stream which appears to the east of Bunting Nook, is culverted under the road and into the east wall of the upper dam. It then flows south- south-west through the ponds and into the steep-sided, wooded valley, through the outcrop of both the Grenoside Sandstone and the Greenmoor Rock before disappearing into a culvert under Woodseats Road. Along the length of the channel there is much evidence of anthropogenic activity in the form of stone-built footbridges and stone-walled channel margins. A very small tributary, from the south, joins the main stream within the valley while a second small stream that forms from a spring near to Hemsworth Road flows south westerly down into the main valley below the last pond. Wherever the land is underlain by the mudrocks there is much evidence of water seepage creating boggy conditions but with insufficient flow to form streams.

Soils:

The soils present in Graves Park have been formed in more recent times, since the end of the Ice Age (about 12,000 years before present), where the interplay of landforms, parent materials and climate have reacted together to develop the layer of soils present.

The variety of sediments and the variation in the landforms does control which types of soils form and where they accumulate. On the outcrops of the sandstones, with the steeper slopes, the soil types range between a sandy Podsol type and a clayey Brown Earth depending upon the level of drainage through the rock. The pH values should range between 3.0 and 3.9 thereby encouraging acid-loving plants to dominate the vegetation. All the steeper slopes have been planted with trees. On the gentler slopes, where the ‘Coal Measures’ are the parent fs/ch/march15 – photos Chris Percy Norton in the Heart of Chantrey Land 5 materials then more clayey Brown Earth soil types are more frequent and have pH values greater than 4.0. Only in the valley floor and on the ‘playing fields’ do the soils become more clayey, due to the more recent accumulation of alluvium due to the location and the anthropogenic activity of the ground staff on the playing fields. These are often Gley type soils with higher pH values of greater than 5.0.

Figure 6. Anthropogenic modification of soils in Graves Park

References

Armitage, H. (1910) Chantrey Land: Being an Account of the North Village of Norton. Sheffield City Libraries reprint 1981, Sheffield UK.

Eden, R.A., Stevenson, J.P., and Edwards, W. (1957) Geology of the Country around Sheffield. HMSO London pp238.

Hallsworth, C.R. & Chisholm, J.I. (2000) Stratigraphic evolution of the provenance characteristics in Westphalian sandstones of the Yorkshire Coalfield. PYGS Vol.53, Part 1, pp 43-72.

Dr Frank Spode March 2015

fs/ch/march15 – photos Chris Percy Norton in the Heart of Chantrey Land 6