An Archaeological Dig in Sheldon

 

A section through the trench at the Sheldon archaeological dig

At the end of the Sheffield U3A Geology Group field trip to Cressbrook Dale, a few of us headed off to Sheldon, where an archaeological dig by students at Sheffield University and other volunteers - initially undertaken in 2022 and 2023 - was coming to an end. 

 

The report on the initial archaeological dig

 

My friend Catherine, who I had helped with the Bolsterstone Graveyard Project, an event with the Bolsterstone Archaeology and Heritage Group and the preparation of a field trip to Sheffield General Cemetery, is an active member of various archaeological groups and she wanted some advice on an unusual type of stone, which had been encountered in one of the trenches that that had been dug to investigate a circular ditch feature. 

 

The LIDAR map of the area to the east of Sheldon

Before our field trip, I had looked at the 1:50,000 scale British Geological Survey (BGS) map and this showed that the trenches had been dug into the upper part of the Monsal Dale Limestone Formation (MDLF), with lead rakes in the immediate vicinity. 

 

The geology of the area around Sheldon

 

Approaching the site, which was due to be restored in the immediate future, I noted a pile of turf and two large piles of subsoil that – according to the methodology cited in the report – was removed using a tracked machine with a toothless bucket and then by hand, down to the bedrock. 

 

A view of the archaeological dig

I have never participated in an archaeological dig and have no knowledge of the techniques used to uncover and record the various layers, but my first view of the trench reminded me of the limestone pavement that I first seen at Malham Cove 40 years earlier and at Co. Clare, when surveying County Geological Sites with the Geological Survey of Ireland. 

 

A view along the trench

 

These examples of karst topography exhibit clints and grykes with a rectangular pattern of jointing, but the limestone here shows no obvious jointing and has been brecciated. This is a common feature of limestone in the vicinity of lead rakes, where the mineral veins occupy fissures that were initiated as joints and faults during the Variscan orogeny.

 

A view of the brecciated limestone bedrock exposed in the trench

As a geologist, I would have liked to have had the time to take a close look at the soil profile that had been exposed but, being aware that at 4 o’clock in the afternoon everyone wanted to go home, I just took a few general record photos of the trench - in which it appears that there is a post hole according to Tim Cockrell, the archaeologist in charge of the dig. 

 

Contrasting rock types with a possible post hole in the upper layer

It was immediately obvious to me that the limestone was overlain by a thin layer of rock that was completely different – in terms of colour, texture, grain size and the pattern of jointing - and I collected loose specimens of each. 

 

A specimen of limestone from the Monsal Dale Limestone Formation

 

The specimen of limestone, which has a very light brown weathered surface, reveals a very fine grained dark grey fresh surface when broken open with some effort and, except for a fragment of a brachiopod shell, contains no fossils. The fresh surface has a siliceous appearance and the MDLF does contain substantial amounts of chert but, when tested with a drop of hydrochloric acid, it effervesces vigorously. 

 

A detail of the limestone and overlying rock

 

The overlying layer has weathered to a brown colour and, when in situ, it has a pattern of very small fractures/joints at approximate right angles to each other, which is quite unlike anything that I had seen before. Examining a few roughly cuboid pieces, which are considerably less dense than the limestone, they are extremely fine grained, do not react to hydrochloric acid and can be easily scratched with a finger nail to produce a very light grey/pink powder. 

 

Specimens of the strata above the limestone

 

When undertaking a survey of the RIGS (Regionally Important Geological Sites) in the Peak District National Park back in 1995/1996, I encountered a wide variety of rocks and minerals and I came to the conclusion that this might be a bed of weathered volcanic ash. These clay wayboards are rich in bentonite and, according to the BGS description of the Carboniferous Limestone Supergroup, often overlie palaeokarst surfaces. 

 

A view of the palaeokarst surface and the overlying clay wayboard

 

At the Hartington Station Quarry, the Temple Mine at Matlock Bath and on the High Peak Trail, exposures of these are weathered to a clay that is easily crumbled in the fingers and, although a chemical analysis would be needed to confirm its composition, a section through the nearby Magpie Mine produced by Noel Worley (1980) – provided by the Peak District Mining Museum – shows that clay wayboards do occur in this area.

 

The section of the Magpie Mine by Noel Worley

 

A Geology Field Trip in Cressbrook Dale

 

Silicified Lithostrotion coral in Cressbrook Dale

Setting off from Trinity United Reformed Church with Stuart and his friend Cheryl, having spent 15 minutes having a look at the Greenmoor Rock on Ecclesall Road while waiting for my lift, we arrived at the Tideswell Dale car park to find that only 8 others had turned up for the Sheffield U3A Geology Group June 2024 field trip. 

 

Spheroidal weathering at Tideswell Dale dolerite quarry

 

Quickly walking up to the Tideswell Dale dolerite quarry, which I have already described in my report on the recce undertaken by Stuart and I on the last day of April, the very bright back lighting didn’t make it easy to see the large scale variations of the physical characteristics and weathering of the dolerite sill that is well exposed here. 

 

A lump of highly weathered dolerite

 

Nevertheless, we could see good examples of the spheroidal weathering of the dolerite, which is well developed here and, using a lump of dolerite that I had collected from the small quarry near to the car park entrance, I demonstrated its highly weathered nature by crushing it in my hand. 

 

A specimen of dolerite from the chilled margin of the sill

 

After collecting a sample from a small quarry excavated into the floor of the main quarry, we all examined this with our hand lenses but none of the essential mineral components - olivine plagioclase feldspar and augite - could be seen as distinct crystals. This usually distinguishes basalt from dolerite, but the Lower Miller’s Dale Lava Member into which the dolerite has been discordantly intruded is typically vesicular and it is probable that this indicates a chilled margin. 

 

Weathered calcite with rhombohedral cleavage

Returning to our cars and driving the short distance to Litton, where we started our circular walk, everyone successfully negotiated the stiles on the way to Tansley Dale, where Stuart explained the lead mining history of the area – a Scheduled Monument – and I obtained specimens of weathered calcite with rhombohedral cleavage, which is associated with the lead rakes here. 

 

Taking lunch in Tansley Dale

 

Taking advantage of the relatively level top of an old waste tip to have our lunch, everyone admired the wide varieties of flowers and plants – identified by a member with considerable botanical knowledge - which now replaced the early purple orchids that had been seen on the recce. 

 

The east end of Tansley Dale

 

Continuing down to the end of Tansley Dale, where the Monsal Dale Limestone Formation (MDLF) changes from light grey calcarenites laid down on a shallow shelf to very fine grained and often argillaceous calcisiltites, which were deposited in deeper water and is described as the Dark Lithofacies on the GeoIndex Onshore map viewer. 

 

An outcrop of the vesicular Cressbrook Dale Lava

Making our way north along Cressbrook Dale, we noted the small outcrops of the vesicular Cressbrook Dale Lava along parts of the public footpath, before walking up the steep unmarked path to Peter’s Stone, where we had a good discussion about the formation of the landslip and noted the Lithostrotion corals that are exposed in one of the smaller slipped blocks. 

 

A view from Peter's Stone towards Wardlow Mires

Rummaging through the scree beneath Peter’s Stone, to find brachiopod fossils and further examples of colonial corals, and taking in the views along the valley to Wardlow Mires, which was flooded when undertaking the original recce in February and led to the field trip being postponed. 

 

Retracing steps from Peter's Stone to the low level public footpath

 

Retracing our steps down to the low level public footpath, we carried on until a place where we could cross over to the west side of the valley, where we explored the well exposed beds of the upper part of the MDLF that dip north-east down to the valley bottom. 

 

Examining a 'death bed' in the Monsal Dale Limestone Formation

When I first visited Cressbrook Dale back in 1993, when assessing the Geotourism potential of the RIGS (Regionally Important Geological Sites) in the Peak District National Park, I spotted some fine exposures of Lithostrotion coral and blocks of fossil scree, but Stuart and I only encountered a ‘death bed’ – a layer with a concentration of brachiopod shells that records a catastrophic event. 

 

A 'death bed' full of brachiopod shells

Having encouraged the group to split up and have a good look at the mainly unfossilferous beds that are exposed in this locality, someone finally discovered the location of the coral that had previously jumped out at me.

 

Another view of the 'death bed'

 

The fossils here have been silicified and differential weathering has left them proud of the surrounding limestone - a spectacular example of which the group had seen along with solitary corals at Hob’s House in Monsal Dale a few years earlier. 

 

Cheryl and Stuart admiring the silicified Lithostrotion coral

Returning to the east side of Cressbrook Dale, we discovered a place where the ephemeral stream flows underground and, cutting across this to avoid the busy A623 road where another public footpath starts, we headed back to Litton.

 

The stream at the head of Cressbrook Dale

 

Greenmoor Rock on Ecclesall Road

 

Greenmoor Rock from the old quarry behind Rustlings View

The day after my trip to Sheffield, to look at some of the architectural sculpture by Frank Tory, I set off from Treeton to meet my friend Stuart from the Sheffield U3A Geology Group, who I had last met at the end of April when undertaking a recce for the June field trip to Tideswell Dale, Tansley Dale and Cressbrook Dale. 

 

Ecclesall Road on the 1894 and 1905 OS maps

 

Alighting from the No. 81 bus at the Ecclesall Road/Junction Road stop with several minutes to spare before meeting him outside the Trinity United Reformed Church, I had a quick look at some of the semi-deatched and terraced houses that had been built on the site of an old quarry on the Greenmoor Rock, sometime between the publication of the 1894 and 1905 editions of the Ordnance Survey (OS) map.

 

The geology around Ecclesall Road and Brincliffe Edge

The Greenmoor Rock at Brocco Bank, Ecclesall Road and Brincliffe Edge was quarried extensively for building stone and for use in headstones, with the John Gregory and Son Ltd. brickworks exploiting the mudstones that are often predominant in this formation. 

 

No. 715 Ecclesall Road

Over the years, I have explored this part of Sheffield in some detail and have led field trips with the Sheffield U3A Geology Group and as part of the Nether Edge Festival to look at the geology that can still be seen in the old quarries and in many substantial Victorian villas in Nether Edge and late Victorian and Edwardian terraced houses on Ecclesall Road. 

 

An old quarry face in the back garden

In a few places, along Kenilworth Place, gennels in the terraced houses and spaces between the semi-detached houses, partly overgrown quarry faces can be seen at the back gardens and loose stone has been used for rockeries in the front gardens.

 

A rockery at No. 707 Ecclesall Road

Although some of the sandstone produced for grindstones was described as Brincliffe Blue, due to the reduced oxidation state of its iron bearing minerals, much of the sandstone used for the substantial terraced houses on Ecclesall Road actually has a green/grey colour. 

 

Edwardian terraced houses

 

Making my way up to Marmion Road, I spent a few minutes exploring the area to the rear of Rustlings View, I was interested to see a small exposure of Greenmoor Rock in a remannt of an old quarry face next to the electricity substation. 

 

An old quarry face to the rear of Rustlings View

 

Walking up the steps and scrambling up the loose material at the base of the quarry face, I managed to obtain a couple of specimens with my Estwing hammer and, retracing my steps back to Ecclesall Road, I took a photo of the modest terraced houses further up the hill before going back to the church to wait for Stuart to arrive.

 

Late Victorian terrraced houses

  

Scissors Paper Stone and Frank Tory

 

Scissors Paper Stone at St. John's church in Ranmoor

Towards the end of 2023, following an illustrated talk that I had given to the Ranmoor Society the year before, I had been contacted by Mary Grover to ask if I would be prepared to contribute to the Scissors Paper Stone community history project that she and others were working on – to help raise funds for the restoration of the spire at St. John’s church in Ranmoor. 

 

An introduction to the church tour by Mary Grover

 

In addition to providing general advice, based on my experience of historic architecture and buildings stones, I had been asked to give a talk entitled The Stones of St John’s - A Geological Assessment on 6th July; however, I was interested in some of the other events that would be held through the year, the first of which was a tour of the church.

 

A good attendance of the church tour

 

Although I had only last visited the church a few days before Church Explorers Week, to closely examine its decorative stones, I wanted to use this event as an opportunity to have another quick look at the sandstone used for the fabric and take a few photos that I might use in my talk. 

 

Ancaster limestone tracery in a south aisle window

 

Once Mary had finished her talk outside the church, everyone convened to the interior to attend the formal opening of the display of artwork by Margaret Bennett, the Committee Secretary of the South Yorkshire branch of the Victorian Society, who had helped to organise the event. 

 

Views of the walling on the south aisle

 

I hung back for a few minutes to take a look at several parts of the walling, where the sandstone had been repaired with what seems to be a sand and cement skim coat and, where spalling of the stone is pronounced, I discreetly removed a couple of pieces with my stainless steel knife. 

 

Samples of sandstone from the south asle of St. John's church

 

After joining the attendees inside the church to catch up with a few colleagues over tea and biscuits, I said my goodbyes and headed back to Sheffield City centre on the No. 120 bus, where the east side of Fargate was illuminated by bright sunshine. 

 

A carved tympanum at Carmel House

 

Carmel House (1892), on the corner with Norfolk Row, was designed by Herbert Watson Lockwood for the YMCA and it has many fine stone carvings by the eminent architectural sculptor Frank Tory, whose work at St. John’s church is exemplary – especially the capitals to the arcades and the reredos. - which I would be mentioning in my forthcoming presentation. 

 

A carved tympanum at Carmel House

 

The Pevsner achitectural guide for Sheffield by Ruth Harman and John Minnis refers to 10 arched panels that depict the days of Creation and the progress of Divine Law but, with the Scissors Paper Stone schedule of events including a talk by Sylvia Dunkley – considered to be a national authority on Frank Tory and Sons - I just took a couple of record photos and continued along Fargate. 

 

The Black Stone Walk elevation of Caffè Nero

 

Except for the architectural sculpture produced by Frank Tory and his twin sons Alfred and William, whose work can be seen in several listed buildings in Sheffield, I have never seen any reference to any other sculptors working in Sheffield and have often wondered who might have undertaken work on the fine Victorian buildings that can still be seen on Fargate – including the former Barclays Bank (1897), which is now the Caffè Nero. 

 

An elaborate datestone at Caffè Nero

 

Frank Tory came to Sheffield in 1880 to work on the long since demolished Corn Exchange and the architects, M.E. Hadfield and Son, were so impressed with his work that he was encouraged to relocate to Sheffield and set up his own business. Having done so, several other prominent Sheffield architects, including Flockton & Gibbs and W.J. Hale, made good use of his services. 

 

Granites at Caffè Nero

During a previous Sheffield U3A Geology Group field trip, I had been shown a now out of print Sculpture Trail by Bob Hodges and later given a photocopy, which highlights the work of the Tory family that can be seen in Sheffield city centre; however, I needed to do some shopping before catching my hourly bus back to Treeton and I just took a couple of photos of the various granites used in the façade of Caffè Nero, before returning to Sheffield a few days later. 

 

Pairs of grotesques on the gate piers

 

On the corner of High Street and East Parade, the brick built Parade Chambers (1884) by M.E. Hadfield and Son has its Huddersfield stone dressings decorated with fine architectural sculpture, which includes a magnificent range of grotesques and fantastical beasts on the high level string course. Next to this building are four massive gate piers, which replaced the original ones in 1882 and are decorated with more wonderful grotesques, which I never cease to wonder at. 

 

A grotesque on a gate pier

Having taken a few more photos to add to my collection, which show these in various lighting conditions at different times of the day, I popped into Sheffield Central Library to return a book and say hello to my friend Claire and noted that flyers for my talk had been distribute, which was a timely reminder that some more preparation needed to be done.

 

A flyer at Sheffield Central Library