Archaeological Investigation

Fine shelly beds in stone used for the restoration

As a geologist, with specialist interests in the building stones used in historic structures and experience of their restoration – as well as possessing a good eye for detail – I have always thought that I could make a very useful professional contribution to the work of archaeologists.

Various stones used in the construction and restoration

A quick walk around the exterior of St. Peter's church, in Conisbrough, shows the variations in the Permian dolomitic limestone used in different parts of the building – representing the masonry techniques and quarry sources used  from the 12th to the early 20th century.

When undertaking stone matching, it involves a detailed inspection of the building, where there may be various phases of construction or restoration - with subtle variations in the colours and textures - and sometimes the stone is completely different.

The Victorian restoration obliterated so much of the external fabric of the church that it is often difficult to positively identify the original mediaeval masonry and, in places, Carboniferous sandstone has been used to restore the limestone ashlar.

Restoration of the 15th century chancel with limestone and sandstone

 

Having only visited St. Peter’s church for my own pleasure, and taken a few photos on the sunny sides of the exterior, I have never had a reason to undertake a hydrochloric acid test or examine the stones through my hand lens, as I would normally do as part of my professional work.

Roughly squared and ashlar walling from the 14th and 15th century

I have not yet studied the Victorian and Edwardian additions to the dark, north side of the church and I am interested to see if the stones used here are similar to those used to restore the south aisle and tower - with differential weathering exposing distinctive ripple marks and highlighting very fine shelly beds. These look more like the Jurassic limestone of Lincolnshire than the dolomitic limestone that I have seen in very many places.

Ripple marks in limestone used for extensive restoration

St. Peter's Church - The Exterior

A general view of St. Peter's church

When last standing on the top of the keep at Conisbrough Castle – surveying the landscape all around me – I struck up a conversation with an elderly couple who had driven from Lincoln and were on the way to see their family in Huddersfield. Having talked about the merits of the castle, which they had never visited before, I highly recommended that – if they had the time – they should visit St. Peter’s church.

A view of the chancel

As a valuation surveyor – in Lincolnshire, Derbyshire and South Yorkshire – I developed an interest in old stone buildings when visiting countless villages where the settlement had grown around the church and I thought that they would particularly like this place.

14th century stonework

Archaeologists have studied this church in great depth and it is considered to be the oldest Saxon church in South Yorkshire; scholarly texts also indicate that it would probably have been one of the very many burghs that were developed to counter the constant attacks from the Vikings from Denmark - who wanted to claim the throne of England for themselves.

Carved bosses

At first sight, St.Peter’s church displays all of the features of the perpendicular style of architecture but, looking closely at the masonry around the exterior, there are also sections from the 14^th century and various “restorations” by the Victorians and additions by the Edwardians – as well as various undated repairs.

A Norman arch with zig-zag mouldings

Once you have entered the porch, it becomes clear that this church is in fact a lot older than the exterior suggests, with a round Norman arch with zig-zag mouldings to the doorway. Set into the wall of the porch, there is also a highly weathered stone carving of Romano-British age.

A Romano-British sculpture

The Keep

The keep at Conisbrough castle

The first stone castle at Conisbrough was constructed in the late 12^th century by Hamelin Plantagenet, the illegitimate half-brother of King Henry II, and the extremely well preserved round keep is the only one of its kind in England.

The staircases in Conisbrough castle keep

It is very solidly built and, looking at the exterior, the fine ashlar masonry is punctuated by a few small windows that light the staircases - which are incorporated into its thick walls - and the chambers that lead off from the principal rooms on the upper floors.

The principal chamber

When I first visited Conisbrough Castle, the keep was an empty shell and although you could go up to the top and take in the views of the surrounding landscape, the magnificent fireplaces and other fine architectural details - carved in Permian dolomitic limestone - could hardly be seen.

A detail from the fireplace in the principal chamber

Now, with the roof and floors reinstated – and with artificial lighting to illuminate what would originally have been a very dark interior – these can now be fully appreciated...

A detail of a vaulted ceiling

Conisbrough Castle

A general view of Conisbrough Castle

When writing Building in Stone – Information for Teachers, my inspiration was taken from visits to numerous English Heritage properties throughout England and from the efforts of the South Yorkshire RIGS Group to promote the best sites for their education value - my idea was to highlight the relationships between stone built ancient monuments and the local geology.

A memorial in Conisbrough

At Brodsworth Hall and Roche Abbey, there are good opportunities to study quarried and natural exposures of the Magnesian Limestone respectively - as well as the building stones used in the monuments themselves.

Conisbrough Castle, like Pontefract Castle, takes advantage of an elevated fault bound outlier of Magnesian Limestone – with commanding views of the Don Gorge and the limestone escarpment, both to the north and the south.

Arriving in Conisbrough on the X78 bus from Rotherham, a bronze sculpture commemorates the coal mining disaster at Cadeby Main Colliery and, walking down and around the high street, there are many old buildings and a well to see.

The old town well

On every approach to Conisbrough Castle, the magnificent keep dominates the skyline and its circular design, with great buttresses, is unique in England. At some time before 1538, a very large section of the curtain wall and the gatehouse collapsed into the moat and left the castle indefensible - it therefore took no part in the English Civil War, when very many castles were completely demolished.

A section of the collapsed curtain wall

Although there are only the foundations of the inner buildings left, the remaining walls provide some good examples of mediaeval stonemasonry and the fine ashlar to the keep is exceptional. The castle itself is set on a very small outcrop of limestone, which is detached from the outlier on which Conisbrough is sited and, at the edge of the moat, a spring continually flows.

A view of the inner ward from the keep

The Yellow Sands Formation often appears immediately beneath the Magnesian Limestone and is an important aquifer for many of the old settlements along the escarpment. Although not marked on the geological map, the spring and the wells in the old town and the castle keep may also tap these porous rocks.

A spring at the edge of the moat

The Don Gorge

A view of the Magnesian limestone escarpment

In previous posts, I have briefly described a few places along the Magnesian limestone escarpment, which I hadn’t visited before – including Pontefract, South Elmsall and Creswell Crags - to assess their potential for field trips.

The geology around the Don Gorge

Together with many other RIGS that I surveyed for Doncaster MBC, these sites are recommended to anyone who wants to know more about the Permian geology of this part of England.

Further to the north of Maltby Crags, shortly after its confluence with the River Dearne, the River Don cuts through the limestone escarpment to eventually form the Don Gorge.

At Cadeby Cliff, across the valley from Conisbrough, several bryozoan reefs stand out from the head, which has crept down the slope, and there are also some very rare exposures of cemented fluvio-glacial sediments, flowstone and excellent examples of crystalline calcite.

 

A detail of fluvio-glacial sediments at Cadeby Cliff

Walking further along the River Don beyond Conisbrough Viaduct, the Don Gorge is now heavily wooded - with nature reserves - but the quarrying industry has left its mark all along its length; although there are no longer any coal mines in South Yorkshire, the dolomitic limestone here is still used for making steel and glass, as well as for constructing and repairing roads and buildings.

A view of Conisbrough Viaduct and the Don Gorge

Although much of the terrain around here is difficult to explore, the large scale slumping and development of large rifts – infilled by loose sand and breccia – adds to its geological interest, as does the appearance of red marl.

A rift filled with limestone breccia and sand