Sunday, 31 March 2019

The Building Stones of Leeds - Part 2

A detail of the frieze sculpture on Abtech House

During my last trip to Leeds in 2018, it was the exploration of its Minster that gave me the idea that, along with the civic buildings on the Headrow, there would be sufficient points of interest in these two key locations to provide the Sheffield U3A Geology Group with a good day out. 

The Building Stone Heritage of Leeds

Having had my ideas confirmed at the January indoor meeting, my next step was to go and take a much better look at Leeds city centre, using The Building Stone Heritage of Leeds – by Francis G. Dimes and Murray Mitchell – as my guide. 

A walk on Park Row

With more than one hundred locations cited, and various others found further afield, I knew that it would take a lot of effort to reorganise this comprehensive booklet into something that might appeal to our Group – within the typical time frame of 5 hours spent out in the field. 

No.1 Park Row

My first day out to reconnoitre Leeds focussed on Park Row, a street that is lined by banks, insurance companies and other financial institutions – past and present - and whose architecture includes ornate Victorian buildings, drab office blocks from the 1960’s and late 20th century multi-storied structures, whose main interest is the granites that have been used for their cladding. 

No. 1 City Square

Having made a note of various buildings on Park Row that I wanted to see, I was disappointed to find that since my guide book was written in 1996, a few of these had been redeveloped. It is also very busy with pedestrians and, having narrow pavements, in many places it is not easy to stop and explain a point of interest to a group that often contains more than 20 people. 

A view north along Park Row

With many of the buildings constructed in Carboniferous sandstone and Portland limestone, good example of which can be seen elsewhere in more easily accessible locations, I decided that I would plan my route to include only the most noteworthy buildings on Park Row, which are found at the northern end near to the Headrow. 

No. 14 Park Row

A particularly unusual stone for northern England, Guiting, is used for the cladding to an otherwise very unremarkable 1960’s office block. This orange Jurassic shelly and oolitic limestone, from Gloucestershire, is not often seen outside the south-west of England and I therefore made the decision to include this on the walk, especially since it can be viewed from across the street where a group would not form an obstruction to passers-by – which also applies to Park Row House

Park Row House

One particularly interesting building, Abtech House, is located opposite the cash point of the Royal Bank of Scotland and with no convenient street corners from which to view it; however, its magnificent frieze is the best example of architectural sculpture that I have seen in Leeds and, together with Swedish red granite and Larvikite, just had to be a stopping point on the walk. 

Abtech House

With a wide variety of civic, ecclesiastical and commercial buildings having been identified at opposite sides of Leeds city centre, my next step in the planning was to return to Leeds at another time to further investigate Walks 3 and 4 in the Building Stone Heritage of Leeds, to explore further the commercial quarter and to selectively investigate its shopping centre, which attracts very many visitors to the city.

Historic buildings on the west side of Park Row

Sunday, 24 March 2019

A Geology Practical in Chapeltown

An experiment in compaction, cementation and lithification

2019 commenced with the indoor meeting of the Sheffield U3A Geology Group at the Commercial Inn in Chapeltown. I particularly look forward to this event, because it increasingly provides me with the opportunity to plan my time for the coming year – as well as the continued social interaction with likeminded people, as I had discovered during the last meeting of 2018 in Totley

Listening to the introduction to the practical lesson

This year, Peter Kennett – who had led the group around the Porter Valley for the November 2018 field trip – was invited to give us a practical lesson in geology, using a wide variety of experiments that he had used when teaching geology to the students of High Storrs School

Learning about deformation

To start, we were split into small groups of 3-4 and given a tray of various rocks, together with a worksheet that introduced the Rock Cycle. This is a basic concept of geology that describes the transition between the three main rock types – igneous, sedimentary and metamorphic – over a period of time that is measured in millions of years. 

An introduction to the rock cycle

Having spent 3 years at Nottingham University to gain a modest BSc. (Hons) degree in geology, I don’t recall any practical lessons that made attempts to explain geological processes in the way that excited me, when learning chemistry at school - for example the combination of glycerol and potassium permanganate or dropping small pieces of lithium, sodium and potassium into water. 

Learning about compaction and lithification

My group’s task was to demonstrate the processes of compaction and lithification of sediments – with or without the addition of clay or a natural cement that would bind the grains together – and those of others next to me were to demonstrate sedimentary deposition and the effects of compressive and tensile forces on rocks. 

An experiment to demonstrate sedimentary deposition

I particularly liked the experiment that showed how horizontal strata could be displaced as thrust faults – or overturned as nappes - as can be seen in mountains such as the Alps or Pyrenees. Using alternating layers of different coloured material, the effects of lateral compression could clearly be seen.

A squeeze box used to demonstrate deformation

This hive of activity took place before a good lunch, after which we resumed our learning with an explanation of geological maps and then discussed our field trip itinerary for the coming year. In the 12 years that the Group had been running, it has explored the Peak District National Park, as well as many interesting places further afield; however, to keep the members interested, it was felt that we needed to find some new field trip locations. 

Learning about the recrystallisation of minerals under pressure

Having previously led walks to Green Moor and around Sheffield city centre, and the Group now beginning to appreciate my experience as a geological conservation and building stone specialist, I was particularly pleased that – subject to works to its castle being finally completed – a day out to the historic market town of Pontefract was finally agreed.

Learning about physical and chemical weathering

In addition, somewhat to my surprise having only tentatively suggested it, “The Building Stones of Leeds” was immediately inked in for the first outdoor meeting of 2019 and I therefore had to get my act together and visit Leeds again very soon.

Various experiments in progress

Saturday, 16 March 2019

Further Surveys of the Greenmoor Rock

Spheroidal weathering and Liesegang rings at Heeley Retail Park

During my brief exploration of Totley, I discovered an escarpment of the Greenmoor Rock that I had never seen before. Although I didn’t see any rock exposures, and had to rely on the vernacular buildings to give me an idea of its physical characteristics here, it provided further insight into its importance - in contributing to the landscape and economy of Sheffield. 

The outcrop of the Greenmoor Rock between Norton and Brincliffe Edge

Having encountered the Greenmoor Rock many times when exploring Sheffield in the last couple of years, I thought that it might be possible to base a future field trip with the Sheffield U3A Geology Group on the sites that I had visited. 

Sites visited to examine the Greenmoor Rock

When visiting the church of St. James the Great in Norton, roughly following the route of the Sheffield Round Walk, I walked through Graves Park a couple of times and was interested to see that several spring fed streams converge here, before flowing down through Cobnar Wood. At the end of October 2018, I decided to go and take a closer look. 

Entering Cobnar Wood in Graves Park

Knowing already that the nearby Morrisons supermarket in Meadowhead occupies an old quarry, with accessible rock faces, I was interested to see how much rock was exposed and if it had potential as a field trip location. 

Mudstone exposed along the stream bank in Cobnar Wood

The strata between the Grenoside Sandstone and the Greenmoor Rock are composed of mudstone and siltstone, which the various streams in Graves Park essentially follow; however, after converging, a single brook runs down through a spectacular steep sided V-shaped valley that has been cut into the similar softer rocks beneath the Greenmoor Rock. 

A detail of mudstone

Although extensive rocky exposures of flaggy sandstone are rare, in many places where the banks of the brook have not been lined with stone walls, it is possible to see outcrops of the finely bedded mudstone and siltstone. 

A general view of Cobnar Wood

Leaving Graves Park at the Cobnar Road entrance, the brook disappears beneath a built up area before reappearing 150 metres further down the road, to the west of the steeply falling ground at the rear of the Big Tree public house.

An outcrop of flaggy sandstone in Cobnar Wood

I had previously walked down the A61 through Woodseats down to the Homebase/Dunelm site, which sits in another large old quarry – exploited for making bricks - where there are good exposures of the Greenmoor Rock and underlying strata, so I decided to try and follow the course of the brook down to the River Sheaf and see what I might find. 

A walk to Sheffield from Graves Park

Discovering that the brook largely flowed through underground culverts, I quickly made my way down to Abbeydale Road and headed back to Sheffield, but not before coming across the site of an old quarry that I had passed by many times in a car or on the bus. 

An old quarry face on Marden Road

Occupied by a petrol station as long as I had known it, and now the site of a car wash, the old quarry faces visible from Abbeydale Road are covered by concrete blocks that form a retaining wall. Turning into Marden Road, however, an extensive exposure of flaggy sandstone can clearly be seen, which I later discovered was another exposure of Greenmoor Rock. 

A detail of the quarry face on Marden Road

From here, a walk up and along the escarpment formed by Brincliffe Edge connects with several locations where the Greenmoor Rock is exposed in old quarries, which once supplied vast amounts of the local variety known as Brincliffe Blue, for general building, kerbs and setts and for high quality memorials. 

Greenmoor Rock at Brincliffe Edge

With my walk from Graves Park to Marden Road revealing two good sites for a potential field trip, my exploration of the Greenmoor Rock in Sheffield in 2018 finally came to an end in the week before Christmas, when I unexpectedly discovered another old quarry that is now occupied by the Heeley Retail Park – which I visited to buy a new DVD player in time for the holiday. 

An old quarry face at Heeley Retail Park

In the car park, in addition to exposures of flaggy sandstone there is an excellent example of spheroidal weathering and Liesegang rings, with an angular spur of sandstone being rounded off by the delamination of sheets of sandstone parallel to its exposed surfaces. 

An exposure of Greenmoor Rock at Heeley Retail Park

Also, at the junction of beds of sandstone with underlying mudstone, an artificial spring line has developed, where permeable and impermeable rocks meet. It makes a good stopping point between the exposures at Homebase/Dunelm and Marden Road and, with a short diversion along the way, to Meersbrook Park, a natural spring can be seen too.

A stream fed by a spring in Meersbrook Park

Tuesday, 12 March 2019

Historic Stone Architecture in Totley

A view of the interior of All Saints church in Totley

In December, the Sheffield U3A Geology Group have a social event held at one of the members’ houses, instead of a field trip, and this year this was held in Totley – a place that I driven through several times on my way to the Peak District National Park, but had never explored on foot. 

A geological map of Totley

Planning my journey so that I would arrive nearly an hour before the allotted meeting time, I had a quick walk around the Conservation Area in the village to look at the various Grade II listed buildings that can be found here, and which are mainly built out of the local sandstone – the Greenmoor Rock

Greenmoor Rock used as walling for terraced cottages along the A621

I had encountered this rock formation several times before in Sheffield - at Brincliffe Edge, the Upper Don Valley and during visits to Norton and Chancet Wood – and further afield at Green Moor, the type locality, and at Castle Hill near Huddersfield. It forms a distinct escarpment wherever it outcrops and, at Totley, this is found in the part of the village to the north side of the A621, where the land falls sharply to Totley Brook

Greenmoor Rock used as a walling stone for a cottage on Totley Hall Lane

On the main road, several cottages are built with roughly squared and coursed blocks of Greenmoor Rock that are generally thinly bedded. A large proportion are stained brown/red due to the high iron content – as I previously noted in former agricultural buildings near to Beauchief Abbey, which is overlooked by the Greenmoor Rock escarpment. 

A late Victorian commercial building on the corner of the A61 and Totley Hall Lane

For the quoins, Greenmoor Rock is also often used for the older vernacular housing, but with more massive sandstone of unknown provenance used for the lintels, cills and jambs and as a general building stone in late Victorian buildings that are found in the Conservation Area. 

A late Victorian house on Totley Hall Lane

On Norton Hall Lane, the Grade II listed old School House, dated 1827, and the Totley Hall Farmhouse and outbuildings – as well as the older cottages – are also built out of the Greenmoor Rock, but the whereabouts of the quarry source for the village is not known. 

The old School House

Carrying on down the hill, following the dip slope of the Greenmoor Rock, Totley Hall – dated 1623 - is set back from the Totley Hall Lane on higher ground, but it can be seen that the general walling here is also iron stained Greenmoor Rock, with more massive sandstone used for the quoins and large lintels, cills, transoms and mullions in the windows of a typical Jacobean style. 

A general view of Totley Hall

Having quickly seen the building of architectural merit in the southern part of the Conservation Area, I walked back up Totley Hall Lane and then went to have a look at All Saints church - dated 1923 and designed in a Neo-Norman style - which had caught my eye when looking on Google Earth before my trip. 

A view of  All Saints church from the north-west

Walking very quickly around its exterior, it is unusual for its modern style of rubble walling, with hand tooled ashlar dressings and, although I didn’t have the time to closely examine the stone, it is very different to that seen in the vernacular architecture of Totley – particularly the very distinct red colouration of very many of the stones. . 

A view of All Saints church from the north-east

Unexpectedly, the church was open and the abundance of round arches in its interior continues the Neo-Norman theme, although the piers and columns are square in profile and not round, as seen in the original Romanesque churches. 

A view of the nave in All Saints church

A very quick exploration of the Conversation Area to the north of the A621, revealed only the modest Grade II listed Bryn and Moor Cottages, which was originally a single house built in 1704 with an L shaped plan and again using the local Greenmoor Rock.

A general view of Bryn and Moor Cottages

Sunday, 10 March 2019

St. James the Great Revisited

A view of the nave at the church of St. James the Great

After the Sheffield U3A Geology Group visit to the Porter Valley, on 21st November, I thought that the extended period of exploration that I had enjoyed since the Heritage Open Days at St. Helen’s church in Treeton would at last come to end. 

The lopsided Early English Gothic tower arch

With the record breaking summer of 2018 having turned into an Indian summer, I had more than made up for a year of relative inactivity compared to my investigation of mediaeval churches in and around South Yorkshire, back in 2016. 

A view of the arcades from the north aisle

My next day out coincided with a coffee morning at the church of St. James the Great in Norton. I had visited this church twice before, once when it was closed and I was only able to survey its exterior and a year later to see its interior, which coincided with one of the Farmers' Markets that are regularly held here. 

The chancel

On this occasion I had the opportunity to look a bit more closely at the various details, especially in the Blythe Chapel, where Magnesian Limestone has been used as general walling stone for its external fabric and dressings in its interior – particularly for the piscina

The piscina is carved from dolomitic limestone

Here, I was also able to take a better look at the details of the alabaster tomb to William and Saffrey Blythe and to the finely inscribed grave slabs that can be seen on its floor, including the memorial to William Selioke and his wife Joyce. 

The memorial to William Selioke and his wife

Without closely investigating the various stones with tools that I normally use when employed as a professional geologist – hydrochloric acid, a steel knife and a hand lens – I could only make an educated guess as to their provenance. 

A detail of the tomb of William and Saffrey Blythe

In hindsight, I have discovered that many Norman fonts that I have seen, and which I had assumed to be made of Magnesian Limestone, are actually made from Caen stone – a soft, easily carved Jurassic limestone from Normandy, which was imported in vast amounts to build cathedrals and abbeys after the Norman Conquest in 1066. 

A detail of the font

The font dates to c.1190 and judging by its pale colour, which contrasts with the yellowish Magnesian Limestone used in the walling of the chancel, this could easily be made of Caen stone and I will investigate further on my next visit.

A detail of the salamander on the font