Friday, 19 August 2022

A Further Survey of Ecclesall Woods

An ochreous spring in Ecclesall Woods

With my attempt to obtain a specimen of the Rough Rock being unsuccessful, I continued my walk with the intention of trying to find an exposure of the strata associated with the Ganister Coal at Ran Wood. The upper part of the course of the Limb Brook follows the line of a fault that separates the Rough Rock and younger Pennine Lower Coal Measures Formation (PLCMF) strata but, after entering Ecclesall Woods, the brook turns sharply to the south

Continuing along the path around the perimeter of the woods, I soon encountered one of several sections of sunken trackways that can be found in Ecclesall Woods, which is presumed by the Friends of Ecclesall Woods to be C19, or later, as it runs across a goit that took water down to the now ruined Ryecroft Mill. 
A sunken trackway
It is likely that they were used by packhorses or mules to carry their loads, quite possibly taking coal from Dore mine down to Abbeydale Industrial Hamlet, although an opencast quarry in the Bird Sanctuary produced poor quality coal and there are at least two old ganister quarries in Wood 3.
A tributary of the Limb Brook in Ran Wood
Having only a grid reference, provided by the Sheffield Area Geology Trust (SAGT), to help me locate the Ran Wood Local Geological Site, I followed the tributary of the Limb Brook for a short distance. Only finding detached blocks of sandstone in various sizes and deciding to come back and take a better look another day, I returned to the path and carried on until I reached a C18 Grade II Listed footbridge, which crosses the tributary. 
The Grade II Listed footbridge

Without having a detailed Ordnance Survey map or my Garmin GPS with me, I can only estimate the location of the various points of interest encountered, but I next came to an ochreous spring, which I had discovered during my previous visit to the woods in early 2017. 
The ochreous spring
Such ochreous deposits are usually associated with the bacterial weathering of the mineral iron pyrite, which is typically associated with coal seams and often mark the location of adits to shallow mines. Looking at the online version of the 1:50,000 British Geological Survey map, a very thin outcrop of the Loxley Edge Rock is overlain by the Forty-Yards/Hard Bed Band Coal (40Y) but I have not found any records of coal mining here. 
At the same location, in a small escarpment that runs along the edge of the wood, there is a small outcrop of massive sandstone, which forms an overhang above thin flaggy beds of siltstone. I can't precisely determine the position of these oucrops but, looking at the geological map, it think that it is a fine grained variety of the Loxley Edge Rock.
Massive sandstone overlying siltstone
I collected a couple of small samples, one of which is a pale grey/brown, thinly bedded, very fine grained sandstone/siltstone and the other is a slightly coarser, micaceous sandstone and contains oxidised iron bearing minerals, which in places give an orange tinge to the generally drab light brown colour of the stone. 
Specimens from Ecclesall Woods (21 mm diameter coin)
A little further along the path, I encountered further small outcrops of massive sandstone, which I didn’t examine closely. Looking at old Ordnance Survey maps, there are no quarries marked in this section of Ecclesall Woods and the first ganister quarries only appear on the 1924 edition map, but these are located either side of Abbey Lane approximately 1 km to the north.
An outcrop of Pennine Lower Coal Measures Formation sandstone

Tuesday, 16 August 2022

The Rough Rock at Whirlow in Sheffield

A detail of the Rough Rock next to the path up the Limb Valley

The Rough Rock is the most extensive sandstone in the Millstone Grit Group, of which it is the uppermost named sandstone, with many prominent features in the landscapes of the Peak District and Pennines being formed by it. 
I have seen the Rough Rock at Beaumont Park in Huddersfield and Roundhay Park in Leeds, and in many buildings in West Yorkshire. The Rough Rock from the Crosland Hill quarry in Huddersfield is uniformly medium/coarse grained and lacks the very coarse pebbly beds that are a feature of Kirkstall Abbey, Leeds Minster and very many of the Victorian historic buildings of Leeds. 
In the Sheffield area, it outcrops widely in the area around Brown Edge on the edge of the Peak District National Park, where it was once extensively quarried for stone slates, pavers, flagstone and general building stone; however, it is a part of Sheffield that I have not yet visited and the only places that I had seen it was at Whinfell Quarry Garden and in a quarry at Langsett, while surveying a potential RIGS (Regionally Important Geological Site).
Whinfell Quarry Garden
A few days after my trip to Tickhill, to look at the castle, St. Mary’s church and various historic buildings, I decided to spend an afternoon having another look at the Rough Rock at Whinfell Quarry Garden and around Whirlow, before following the Limb Brook down to Ecclesall Woods. 
The Rough Rock at Whinfell Quarry Garden

I was interested to note this time that, in one of the quarry faces, there has been some folding and possibly faulting, which is clearly seen in the disruption of the flaggy sandstone, which generally dip a few degrees to the south-east. 
Disrupted beds in the Rough Rock
Although I had my Estwing hammer with me, I didn’t see any obvious discrete place where I could obtain a specimen of this rock and, knowing that there were other places on my walk with good rock exposures, I just took a few photographs and continued to another old quarry face adjacent to the path up to Ringinglow. 
An old quarry face at the bottom of the Limb Valley
Here there is a succession of alternating beds of flaggy sandstone and mudstone, which have been highlighted by differential weathering to leave substantial overhangs. Shallow angle cross-bedding is seen in the sandstones and in the lower part of the section, there is an excellent example of spheroidal weathering in a bed of iron rich rock. 
The development of spheroidal weathering in an iron rich bed

In places, the uniform dip of the strata is interrupted by gentle flexing of the beds, but without the fracturing in the rock that I had seen in Whinfell Quarry Garden a few minutes earlier. Again, I decided not to collect a sample of Rough Rock here and just took a few more photos before continuing with my walk. 
Gentle flexing in the Rough Rock
Following the path that runs down the edge of the playing field to the south of Ecclesall Road South, I then diverted into the adjoining woodland to follow the course of Limb Brook, where I had seen many exposures of the Rough Rock in spring 2017. 
Rough Rock exposed in the streambed of Limb Brook
This time, at the beginning of the second week in September, I found a few exposures that were clearly visible but quite inaccessible but, after making my way downstream, the undergrowth around the stream banks had grown to such an extent that I was unable to obtain a rock sample.
Rough Rock in the streambed of Limb Brook

Historic Architecture in Tickhill

A detail of Tickhill Library

When briefly visiting Tickhill Castle and St. Mary’s church, I encountered a lot of good quality Permian dolomitic limestone that was probably quarried from the Cadeby Formation around Maltby, a few kilometres to the west – in addition to a limestone that I was not familiar with. 
A view along Paper Mill Dike

It is not unusual for the best stone to have been brought such distances to build castles and churches after the Norman Conquest but, when briefly exploring Castlegate, North Gate and Sunderland Street, I was interested to see that very many of its modest vernacular buildings and a lot of the boundary walls are also built in limestone. 
A boundary wall

The underlying geology of Tickhill comprises dolomitic limestone of the Upper Permian Brotherton Formation and calcareous mudstones of the Roxby Formation, which are overlain by the Triassic Lenton Sandstone Formation – none of which have a reputation for producing building stone, other than for very local use. 
A view along Sunderland Street
Unsurprisingly, brick rather than stone is the dominant building material, with red pantiles traditionally used for the roofs - although many have been replaced in Welsh slate There are 112 listed buildings in Tickhill, the vast majority of which are of Grade II status, but I didn’t see anything larger than Darfield House – a late C18 three storey house built in limestone ashlar. 
Darfield House and the Market Cross
I didn’t spend any time closely examining the stonework on any of the buildings that I passed, but none of them are built of very thinly bedded limestone, which I would expect if locally quarried limestone from the Brotherton Formation had been used. 
The Market Cross

The Market Cross, which is traditionally dated 1777, is in a circular peripteral Roman Doric temple form, with a saucer dome and four tiers of stone steps leading up to it. Massive blocks of limestone have been used here and these are undoubtedly from the Cadeby Formation.
The only civic building that I saw was Tickhill Library, a red brick structure with stone dressings that I initially assumed to be a further example of limestone from the Cadeby Formation; however, when getting up close to it, I discovered that White Mansfield stone has been used for raised lettering and the dressings. 
Tickhill Library

Towards the southern end of the Magnesian Limestone escarpment, the Cadeby Formation becomes increasingly sandy and, in the Mansfield region of Nottinghamshire, the rock would be classified as a dolomitic sandstone rather than a dolomitic limestone.
A detail of weathered White Mansfield stone at Tickhill Library

It typically contains very fine beds of green clay, which differentially weather to produce a very distinctive surface texture that reminds me of old crinkled leather. Like its counterpart, Red Mansfield stone, it is no longer available and finding a stone suitable for repairing it is not easy. 
St. Leonard's Hospital

Before heading home, I had a quick look at St. Leonard’s Hospital, a Grade II* Listed timber framed building, which dates to 1471. The ground floor sub-bays are divided by octagonal posts, which are set on moulded limestone plinths – a feature that I had not encountered before. 
Moulded stone plinths at St. Leonard's Hospital

Sunday, 14 August 2022

St. Mary's Church in Tickhill

St. Mary's church in Tickhill

Although it was the first time that I had been to Tickhill Castle, I have visited the village of Tickhill a few times before – including a survey of an outcrop of Triassic sandstone for the Doncaster Geodiversity Assessment and a quick look at St. Mary’s church on behalf of the architect who had appointed me to survey the stonework at Brocklesby Hall in 2004. 
The approach from Church Lane

Back then, I didn’t have the interest in and experience of surveying mediaeval churches that I do now and I only noted that it is built in Permian dolomitic limestone from the Cadeby Formation and I only took one photograph - to record the condition of the limestone that has been used for a repair to the north porch.
The tower
Approaching along Church Lane, the early Perpendicular Gothic style windows to the south aisle and clerestory are its most distinctive feature - on first impression - and various sources period of extensive rebuilding and extension that took place from about 1350 onwards. 
The south porch

The church was not open and I just had a quick walk around its exterior, noting the principal elements of the structure and those parts of the uniformly grey limestone masonry that had been restored, which includes most of the window tracery. 
Restored window tracery in the south aisle

The fabric is in generally very good condition, with only repairs to some of the buttresses and isolated sections of ashlar having been undertaken with whole blocks of stone but, in places, the practice of using stone slips to undertake a SPAB (Society for the Protection of Ancient Buildings) style ‘honest repair’ has been followed. 
A repair with slips of limestone

Continuing anti-clockwise around the church, the only elaboration decoration that I noticed was on the tall crocketted pinnacles but, looking closely at my photographs, I can see that there are couple of grotesques on the string course below the castellated parapet on the south aisle. 
The east end
Moving round to the east end, I did notice one of these at the junction between the chancel and the north-east chapel, which was built in the early C14 and has simple Early English Y-tracery to the east window, which has probably been reused. Its wide open mouth suggests that it is a gargoyle rather than a grotesque, but its current position does not form part of the roof drainage detailing and it may therefore also have been reset. 
A gargoyle on the chancel
With the north elevation being in deep shade, I just took a couple of general photos and continued around to the tower, which has an early C13 lower stage with very large simple clasping buttresses. It was raised during the general rebuilding but was still incomplete by 1429, which gives quite an accurate date for the subsequent completion of the tower, with arched crenellations. 
The west door

The church website states that the oldest parts of the church date back to 1109, when major work was being undertaken to the castle, with the broad buttresses forming part of the Norman church. The west door is Early English, but has many elements that are transitional from the Norman style of doorway, including its three orders of shafts and large nailhead decoration. 
Shafts and nailhead decoration to the west door

Looking up the tower, numerous coats of arms can be seen and a study of the heraldry show these to be associated with John of Gaunt, who held the castle and had claims on Castile and Leรณn. This dates this part of the rebuilding from 1373 to 1399 and other shields adjoining the west door are those of William Eastfield (d.1386) and of John Sandford who lived here in 1394.
A view up the tower
At the same level as the heraldic shields of the latter, there are other sculptures on the upper stage of the tower, which Pevsner describes as a canopied saint, along with a knight with his son and a lady, who are presumed to be the principal benefactors of the church. 
Figurative sculptures on the tower

I didn’t spent long enough to study the stonework in depth but, from subsequent desktop research into the extent of the land held by the Cistercian Order, I concluded that the stone used to build it was probably supplied by the Roche Abbey quarries.
A canopied saint on the tower

Thursday, 11 August 2022

An Open Day at Tickhill Castle

A view of the motte and bailey at Tickhill castle

After a busy August, when most of my days out had a geological theme and ended with a recce of Lyme Park, my next trip was on the first weekend of September 2021 to visit Tickhill Castle, which is only opened to the general public on one Sunday afternoon a year. 
The guide to Tickhill Castle

From Treeton, it is less than 18 km away as the crow flies and is easy to get to by car; however, by public transport it requires two changes each way, via Doncaster, which I was determined to do last year, but which cuts to the Sunday service in Treeton has now made exceedingly difficult. Luckily my next door neighbour Dan, who had accompanied me on walks in Treeton Wood and Rawmarsh, also wanted to go and so a day mainly spent travelling was avoided. 
Treeton to Tickhill as the crow flies

The original motte and bailey castle was built by Roger de Busli, a Norman Baron who participated in the Norman Conquest of 1066 and was granted the Honour of Tickhill, which included numerous manors in Nottinghamshire, Derbyshire and also South Yorkshire, where he built castles at Laughton-en-le-Morthen, Mexborough and Kimberworth. 
The original castle was built on a spur of the Triassic Lenton Sandstone Formation, which rises no more than 10 metres above a surrounding low lying andscape that is composed of soft marl, sandstone and alluvium - into which the moat was dug. 
The Norman gatehouse

The guide to the castle states that the gatehouse was built c.1070-1080, using Permian dolomitic limestone from the Cadeby Formation to the west, and the Sheela Na Gig Project also dates the stone carvings on its front to the late C11. 
A detail of the gatehouse
Passing through the gatehouse and looking at its east elevation, there is a very obvious change in the masonry from the original very pale grey massive limestone to the thinly coursed, very well bedded dark buff stone, which is used for the surround to the large Elizabethan mullioned window. 
The east elevation of the gatehouse
At the time, I didn’t even think about looking at the various stones very closely, as the castle was only open for 2½ hours and I was wandering around it with Dan, but when looking at my photographs close up on my computer screen, it has puzzled me – especially since the late C16 west wing of Tickhill Castle House and the early C17 buttresses on its east side have been built from a very similar stone. 
Tickhill Castle House
The north and south buttresses have round arches of an unknown date set into them and the walling stone has very many vughs along the bedding planes, which reminds me of the Cadeby Formation that I saw in Pontefract - which is underlain by the Yellow Sands Formation – and also isolated blocks in boundary walling at Carr. 
A round arch in the northernmost buttress
The building of the curtain wall began in 1102, after a siege of the castle by Robert Bloet, with the limestone being very probably brought from the quarries in the manor of Maltby, which were later used to build Roche Abbey and also supplied stone for many Norman churches in the region. 
A section of the eastern curtain wall

Henry II began the construction of an eleven sided stone keep in 1180, which was completed in 1192, but only the foundations of this remain today; however, access to the upper part of the motte was not permitted and I didn’t get an opportunity to look at the stonework. 
A view of the motte
The castle functioned as a key administrative centre on the Nottingham/Yorkshire border and was subjected to further sieges, including action during Prince John’s failed attempts to displace his brother, King Richard I. Its various owners therefore spent considerable money on its maintenance and improvement and, when walking around the walls, various phases of building can be seen. 
A view of the exterior of the curtain wall
By 1540 the castle was in very poor repair, like very many other castles throughout Britain, due to their decreasing military importance in the face of the threat of heavy artillery. After he took a lease in 1614, it was later restored and fortified by Sir Ralph Hansby and was a Royalist stronghold during the English Civil Wars, but the keep was pulled down in 1649.
The Hansby coat of arms