Wednesday, 23 June 2021

A Field Trip in Conisbrough - Part 4

A view to the west from Conisbrough Viaduct

Continuing with my exploration of Conisbrough, for a proposed field trip with the Sheffield U3A Geology Group, when making my way down the angled retaining wall at the outcrop of glaciofluvial sandstone at Constitution Hill Bridge, I had to consider how the group would cope with this incline.
A view down the angled retaining wall

Since joining the group in 2015, I had been out with them to numerous places where the vast majority of the members had tackled some steep climbs up rocky and uneven slopes but, although the study of geology necessarily entails exploration of such terrain, the U3A now require a risk assessment to be made for field trips.
Constitution Hill in February 2007
Having made my way safely back down to the track, I carried on eastwards towards the railway tunnel, which is at the east end of the site. During previous visits, I had found further clearly visible exposures of readily accessible glaciofluvial sandstone and beds of limestone, which have excellent examples of flowstone and calcite crystals on the exposed joint planes.
Calcite crystals on a joint plane as seen in February 2007

On this occasion, however, even though I had previously visted during September in 1997 and then during February in 2007, with the latter being the optimum time of the year to see bedrock, there were no obvious rock outcrops anywhere.
A view along Conisbrough Viaduct

In winter, the exposures may be much better exposed or a preliminary visit with gardening tools before a field trip may reveal some of the features that I had identified but, for now, I just carried on to Conisbrough Viaduct, which is built with the renowned Staffordshire Blue engineering bricks.
A view towards Cadeby Quarry from Conisbrough Viaduct

To the north, there are glimpses of the entrance to Cadeby Quarry, which contains a Geological SSSI - the type locality for the Cadeby Formation - and is now the major supplier of this dolomitic limestone. Although building stone was once widely quarried along the length of the Magnesian Limestone outcrop, it is now only available from a very few places.
A view east from Conisbrough Viaduct

On the east bank of the River Don, the waste stone from one of the old quarries that are found along this section of the Don Gorge can clearly be seen. Unlike others nearby, which are densely overgrown with vegetation, this quarry was active until quite recently and the spoil is still fresh.
A view to the north-east from Conisbrough Viaduct

Continuing across the viaduct, there are good views of the surrounding landscape and, although not illuminated by the afternoon sun, the escarpment on the Conisbrough outlier – known locally as The Crags – can be seen in the distance to the west and the keep of Conisbrough Castle is just visible above the surrounding trees.
A view of Conisbrough Castle keep from Conisbrough Viaduct

Having crossed the viaduct, I found a path that I had not traversed before and, instead of taking a diversion and following this eastwards to the Nearcliff Wood Quarries, which I would include in my field trip, I was more concerned with finding the best route back to Conisbrough.
A rock exposure next to the public footpath to Conisbrough

Tuesday, 22 June 2021

A Field Trip in Conisbrough - Part 3

A detail of a glaciofluvial deposit at Constitution Hill

Continuing with my recce for a proposed field trip in Conisbrough with the Sheffield U3A Geology Group, I left North Cliff Quarry and started to make my way down the path along the east end of the area known as The Crags, before stopping to photograph an outcrop of massive, well bedded dolomitic limestone of the Cadeby Formation. 
An outcrop of dolomitic limestone at The Crags

When visiting North Cliff Quarry with the first group of Year 7 KS3 students at XP School in Doncaster, where the Doncaster Geodiversity Assessment had been used to select suitable sites for a geology field trips, I hadn’t noticed any rocky outcrops because it was covered in trees and it made me wonder if the area might be worth further investigation at a later date. 
A headstock on Doncaster Road

Continuing down the hill to Doncaster Road, I crossed the road and stopped briefly at the old headstock that commemorates the former Cadeby Main Colliery that, with the nearby Denaby Main Colliery, once dominated the landscape here and employed thousands of people. 
Sculptures produced for the former Earth Centre

Crossing over the railway at the entrance to the site of the former Earth Centre, where sculptures entitled “Fund Raising Tree” and “Egg” are reminders of this ill conceived and money wasting Millennium Commission project, I crossed the bridge over the River Don and continued past the site of the colliery railway marshalling yard until I reached Cadeby Cliff. 
Cadeby Cliff

In February 2007, when I last visited this site, numerous bryozoan reefs stood out against the general background of the escarpment but, in late September, when the vegetation had reached the height of its growth, these are much less obvious. 
A view of Constitution Hill in February 2007

Walking eastwards past Constitution Hill Bridge, I was disappointed to see that one of the most interesting rock exposures that I had seen during my survey of several hundred potential RIGS (Regionally Important Geological Sites) in South Yorkshire, in 1996/1997, was in danger of becoming overgrown. 
A view of Constitution Hill in September 2020

Above an angled retaining wall to the north side of the old railway line, which I have always assumed was built to support it, the 6 m x 2.5 m exposure of well cemented Quaternary glaciofluvial rock is becoming engulfed by trees and shrubs. 
Mapped glaciofluvial deposits on Constitution Hill

The British Geological Survey map marks an area of about 3.5 hectares of Quaternary glaciofluvial sand and gravel, most of which is covered by the gorse that thrives on the sandy soil formed here, and it is very briefly described in the 1948 memoir - Geology of the Country Around Barnsley.
A detail of glaciofluvial sandstone at Constitution Hill

Scrambling up to the outcrop, I had a further look at the various sediments here. The upper part comprises grey/brown, well cemented shingle, with large angular and sub-rounded limestone clasts and flattened sandstone pebbles, which in places are imbricated to the east. 
A section through the outcrop

This overlies a pink/orange gritty sandstone, which does not contain blocks of limestone and contrasts in colour with the overlying rock on both weathered and fresh surfaces. In places, the stone is covered in flowstone, which suggests that the sediments have been laid down in fissures or rifts in the limestone, where they have been cemented with calcite that has dissolved and percolated through the rock from above.
An example of flowstone

During my surveys of geological sites in Doncaster, I encountered other glaciofluvial sand and gravel deposits, but they were unconsolidated deposits that lie immediately above the Chester Formation and some have a silty fine grained matrix that could be derived from reworked till. 
Mixed sandstone pebbles and limestone blocks

I am not an expert in Quaternary geology but a former curator of Natural History at Doncaster Museum, Colin Howes, has long since advocated further research along the Don Gorge and, based on my experience of undertaking geological surveys in Doncaster, I have always shared his views and have similarly expressed these to Doncaster MBC.
A section through the outcrop

Friday, 18 June 2021

A Field Trip in Conisbrough - Part 2

A bryozoan reef at North Cliff Quarry

As one of the field trip leaders of the Sheffield U3A Geology Group, reflecting my working background in the building restoration industry in London and specialist interests in building stones, many of the days out that I have organised have had an ‘urban geology’ theme – in Leeds, Sheffield and Pontefract.
Building in Stone - Information for Teachers
The English Heritage Information for Teachers leaflet, Building in Stone, which I co-wrote with the Education Officer at York in 2002, was strongly influenced by my experiences of visiting many of the castles in their care. These include Conisbrough, Peveril and Bolsover castles, which were built to take full advantage of prominent landforms that overlooked long established trade and communication routes.
With considerable experience of geological conservation, however, in South Yorkshire, the Peak District National Park and the Republic of Ireland, I have also encountered various geological sites with particular educational value, with the next stop on my ‘field trip’ being one of these – at North Cliff Quarry, which is 700 metres to the north-west of St. Peter’s church in Conisbrough.

The route from Wellgate to North Cliff Quarry
Taking the path at the end of Wellgate, which leads towards Conisbrough railway station, and then following the path along the northern boundary of the school playing fields, there are good views of Conisbrough Viaduct to the west, which marks the beginning of the Don Gorge.
Conisbrough Viaduct

Looking to the north, there are also good panoramic views of the Magnesian Limestone escarpment on the north side of the valley formed by the River Don, which stretches into the distance towards High Melton and Hickleton.
A panoramic view of the Magnesian Limestone escarpment

Arriving at the south-west corner of North Cliff Quarry, which sits on the edge of a faulted escarpment of the Cadeby Formation known locally as The Crags, I skirted the quarry along the path that continues around to its north side, before descending along a path into the quarry floor.
A general view of North Cliff Quarry

Health and Safety considerations are now paramount when organising field trips, with ‘risk assessments’ now being required by the leaders at the Sheffield U3A Geology Group. Usually, this just requires common sense and, during their field trip, the group of Year 7 KS3 students from the newly formed XP School in Doncaster took great care when navigating their way around the quarry, which has rocks hidden under long grass and bottles and cans left by inconsiderate youths.
The bryozoan reef and massive limestone
The principal feature of interest here is the bryozoan reef in the Wetherby Member of the Cadeby Formation, which forms a pillow like irregular and unbedded mass in the north-east corner of the quarry. Lookig closely, it can be seen that the thick massive beds of dolomitic limestone have been depressed by the weight of the overlying reef, when the sediment was still soft.
Massive bedded limestone at North Cliff Quarry

As with very many sites that I identified in South Yorkshire as having good educational value, the rock faces are slowly being obscured by shrubs and trees. Although the dumping of burnt out cars no longer seems to be a problem, Doncaster MBC do not maintain these sites and, like other local authorities in South Yorkshire, rely on the voluntary efforts of the mainly retired members of the Sheffield Area Geology Trust.
Cross-bedded limestone with bivalves

With a bit of care, however, it is still possible to get close up to the rock faces to examine some of the ooidal, cross-bedded massive beds, which are and packed full of shells of the diminutive bivalve Bakevellia antiqua that can be seen with the naked eye.
Massive bedded limestone

Thursday, 17 June 2021

A Field Trip in Conisbrough - Part 1

Conisbrough Castle

My day out in Lincoln during September 2020 had more than made up for the Heritage Open Days festival, which had been severely cut back due to the COVID-19 Pandemic restrictions still in place and, although I was unable to gain access to various buildings, I took very many photos and I was kept busy writing my Language of Stone Blog for nearly 8 weeks.
The route of my planned field trip
For my next excursion, in week 28 of the pandemic, I decided to try out a field trip that I had tentatively proposed as one of the field trips for the Sheffield U3A Geology Group in 2020 – an exploration of the geology and historic architecture in and around Conisbrough, which occupies the north-east end of an outlier of dolomitic limestone of the Permian Cadeby Formation.

When undertaking geological survey work on behalf of the South Yorkshire RIGS Group and resurveying these sites for the Doncaster Geodiversity Assessment, while temporarily working with the British Geological Survey, I had identified several geological sites in the area that I thought had good educational value.
Conisbrough Castle

Alighting the X78 bus on Castle Hill, where the car park here is a good place to meet, I walked up to Conisbrough Castle, which is sited on a very small outlier of the Cadeby Formation. A short walk around the curtain wall provides a good introduction to the use of local building stone, as I had demonstrated with a Rotherham WEA geology class several years earlier.
St. Peter's church
On the west side of the castle, the moat cuts into the Pennine Upper Coal Measures Formation strata to produce a spring that, according to one of the English Heritage staff when I last visited the castle in 2015, flows permanently; however, this time, I couldn’t find it beneath the vegetation and continued up Castle Hill to St. Peter’s church.
Side alternating quoins at St. Peter's church
Allegedly, it is the oldest building in South Yorkshire, dating to c.750, and is full of interesting features and the various phases of construction and different architectural styles provide a good introduction to standing buildings archaeology.
A blocked Anglo-Saxon window

I have visited the church numerous times and, except during services, it has always been open to the general public and, on this occasion, I took a closer look at the Anglo-Saxon elements – side alternating quoins at the end of the nave, which were once on the exterior, and the blocked window above the north arcade.
The north aisle of St. Peter's church

Except for the Victorian north aisle, built in 1866, which I hadn’t previously examined in any detail, I didn’t spend any time looking at the exterior of the church and crossed the road to Wellgate, where a very unusual late mediaeval well cover stands at the edge of a small housing estate.
The old town well on Wellgate

Monday, 14 June 2021

Steep Hill in Lincoln

The doorway to Jews House

On the last leg of my day out in Lincoln, on the 15th of September 2020, having taken 200 photographs of the interior of Lincoln Cathedral – nearly a third of the total for the day - I finished my exploration of its stone built architecture at Steep Hill.
Norman House

Norman House at 46/47 Steep Hill, is a Grade I Listed building, dated c.1170, and was once known as ‘Aaron’s House’, because it was erroneously believed to have been the home of Aaron of Lincoln, a wealthy Jewish moneylender, who advanced large sums to the nobility, including the king of England - Henry II.
The entrance to Norman House

Although it still retains its original doorway, which once had a chimney projecting from the wall above, it has been altered considerably over the years, with the majority of the windows being added much later in the C18 and C19.
The restored double arched window

During its restoration in 1878, a double round headed window was found in pieces in a recess on the ground floor and was reset in its current position, with most of the masonry sections, including the foliate capitals, being renewed in matching Lincoln stone.
Harding House
A little further down Steep Hill, the Grade II Listed Harding House dates to the C16, with a Lincoln stone ground floor and a timber framed upper storey, but it was substantially altered in the C18 and restored in the mid C20.

Jews Court

Continuing down the hill, just before Steep Hill turns into The Strait at Danes Terrace, Jews Court provides another example of a Norman stone built town house. Also dated to c.1170 and Grade I Listed, it lacks the obvious C12 features of Norman House, with it being completely remodelled in the early C18.
Jews House

Next door, there is yet another Norman house of the same date, Jews House, which still possesses many of its original features; however, it was altered in the C18 and refenestrated in the early C19 and the C20, which resulted in the loss of most of the columns and details to the double arched round windows on the first floor.
Altered windows at Jews House

It is still the most impressive of the three Norman houses and the doorway, which still has a chimney above, is richly ornamented with interlacing and foliate capitals, although the latter are very weathered and much of the detail is lost.
A detail of the door arch at Jews House

Although most visitors to Lincoln would probably be attracted to the cathedral and the castle and other ‘uphill’ monuments such as the Roman Newport Arch and east gate, this collection of Norman houses, which also includes St. Mary’s Guildhall, is the richest in Britain – to which can be added Boothby Pagnell manor house in South Kesteven.

The route of my walk around Lincoln

Having spent five hours wandering around this fantastic city and taken over 650 photographs, which has provided plenty of material for my Language of Stone Blog, I now had to make my way back to the railway station and catch my train. Arriving back in Sheffield, I had just enough time for a pint of Thwaites Wainwright at the Old Queens Head before my bus home to Treeton arrived.  
A pint of Thwaites Wainwright