A Geology Field Trip in Lathkill Dale

 

A view up Lathkill Dale

Following on from a visit to a few sites in Doncaster in March 2022, the next Sheffield U3A Geology Group field trip took place on a fine April day, to investigate the Carboniferous Limestone of Upper Lathkill Dale in the Peak District National Park. 

 

The geology around Upper Lathkill Dale

Setting off from the meeting place next to the public toilets, to the east of Monyash, we headed east along Church Street until we found the footpath that leads down to Ricklow Dale, a now dry shallow tributary of Lathkill Dale where the Eyam Limestone is exposed. 

 

The Eyam Limestone Formation in Ricklow Dale

At the end of the dale, we then went to investigate the Ricklow Quarry, a SSSI (Site of Special Scientific Interest) that exposes a section through an outstanding example of a shelf developed reef, composed of carbonate mud mounds, which was fringed with crinoids and contains some of the UK’s best specimens of Gigantoproductus brachiopod fossils. 

 

Ricklow Quarry

We didn’t get to see any beds with brachiopods, but there were many good examples of crinoid stems, which had weathered proud of the calcite matrix. The crinoidal limestones in the Monsal Dale Limestone were once widely quarried and polished, to produce decorative stone for fireplaces and floors, but the only remaining source is the Once-a-Week-Quarry at nearby Sheldon. 

 

Crinoid stems

The quarry is on the edge of Lathkill Dale and although most waste rock was tipped into the valley bottom, there was plenty of stone lying around the quarry floor. Although it is illegal to collect samples from the rock face at SSSIs, I was able to obtain specimens of a brachiopod and crinoidal limestone from these using my Estwing hammer. 

 

Specimens with brachiopods and crinoids

After taking lunch, we then followed a path along the edge of the dale, where there were excellent views of its morphology and the various horizontal beds of Eyam Limestone exposed in the upper section, with the lower Monsal Dale Limestone covered by a thick scree slope. 

 

A view down Lathkill Dale from Ricklow Quarry

Making our way slowly down a steep and sometimes precipitous path, we eventually reached the bottom of the dale before having a quick look at the scree formed by waste rock from Ricklow Quarry. We didn't see any obvious reefs that apparently appear in the upper parts of the exposed limestone and headed east down the dale.

 

Views at the bottom of the path descending into Lathkill Dale

No rock exposures could be explored at low level due to the covering of scree, so we continued along the path for a few hundred metres before stopping at Lathkill Head Cave, from which the River Lathkill emerges when there are high levels of rainfall and groundwater, but which ceases when the water table drops. 

 

Lathkill Head Cave

When exploring the rock strewn temporary stream bed that leaves the cave, I found a large piece of limestone that contains several brachiopods with well preserved fine ribs and some crinoid stems - possibly from the Lathkill Shell Bed, which forms a distinctive marker horizon. Being persuaded by one of the group members not to beak off a piece, when I cleaned it of dirt and algae at home, the fossil casts are revealed to be brown in colour, with the binding matrix being white. 

 

A large specimen with brachiopods and crinoids

 

Lathkill Dale is a dendritic dry valley system, which is deeply entrenched into a karst plateau, and opposite Lathkill Head Cave, another former water course or waterfall has cut a nick into the Eyam Limestone to form quite a distinctive feature. 

 

A tributary valley

 

Continuing down the dale, deposits of calcite on the rocks mark the intermittent course of the river and, after a short distance, water was flowing from another spring that feeds the River Lathkill but before we reached Pudding Springs, which flows permanently except in times of severe drought, we crossed the footbridge and headed up Cales Dale. 

 

A spring feeding the River Lathkill

 

Walking along the path, we stopped to look at a block of limestone embedded in it, which contains a good example of corals – probably of the genus Lithostrotion or Diphyphyllum, which we had seen before in the Monsal Dale Formation at Hob’s House and Eyam.

A block of limestone with corals

Leaving Cales Dale by a steep path that led up to the limestone plateau, we encountered a small adit that has been dug into a short mineral vein, which is marked on the British Geological Survey map, where the rhombohedral habit of the crystalline calcite above it is quite obvious. 

 

An adit dug into a calcite vein

 

Although there is a long history of lead mining along Lathkill Dale, we didn’t see any galena, fluorite or barytes, which are very often associated with the rakes of Derbyshire. We continued along another unnamed shallow dale, which is tributary to Cales Dale, until we reached One Ash Grange – a settlement that was formed by the Cistercian monks of Roche Abbey in 1147. 

 

Views of One Ash Grange

I didn’t see anything in the various agricultural buildings that suggested such an ancient history; however, I thought that the Grade II Listed C18 pigstyes are quite spectacular – especially since large slabs of Carboniferous Limestone, instead of sandstone, have been used for their flat roofs, which I had not seen before. 

 

A detail of the pigstyes at One Ash Grange

 

We finished the day by taking the public footpath from One Ash Grange back to the southern edge of Lathkill Dale, where we got another view of the Ricklow Quarry, before continuing along the path that drops into the dale and back to our starting point. 

 

A view of Ricklow Quarry

Having got back to Sheffield, with half an hour to wait for my bus back to Treeton, I took advantage of the late afternoon sunshine by enjoying a very welcome pint of beer at a great traveller’s rest, the Old Queen’s Head.

 

A pint of beer at the Old Queen's Head

Various Building Stones in Hayes

 

Sandstone and flint at St. Mary's church

During my brief visit to London, to help my mother with her convalescence after she had broken her hip, I had undertaken a couple of half day visits that appealed to me as a geologist – particularly the 'dinosaurs', ‘Geological Illustrations’ and deposits of the Claygate Member of the London Clay Formation at Crystal Palace Park and the Harwich Formation at Keston Common.

 

The Triton Stone Library

 

Having worked in the building restoration industry in London and later devising the Triton Stone Library, I was also very interested to encounter several building stones at the Church of St. John the Baptist in West Wickham, some of which I was not very familiar with.

 

The New Inn

 
On my last day, I decided to take a quick look at Hayes which, like many of the suburbs in this part of Greater London, is an old village that has been absorbed by vast interwar housing developments and its character is mostly lost. Arriving on the No. 119 bus from West Wickham, I was immediately attracted to the New Inn, which first appears on the 1909 Ordnance Survey map and was rebuilt after it had received a direct hit with a bomb in WWII. 

 

A detail of walling at the New Inn

The thinly bedded rubble walling masonry, which is orange/brown in colour and contains very high concentrations of iron that would probably classify it as an ironstone. Obtaining a loose piece from the boundary wall from the car park, it contains thin medium grained sandy layers in a body of stone that is finer grained, with both reacting strongly to hydrochloric acid. 

 

Ironstone from the boundary wall to the New Inn

Looking at an old photo of the original building, the two storey southern section seems to have survived and the dressings to the door and windows are made of a honey coloured limestone that is composed mainly of shell fragments. I have only encountered Ham Hill stone from Somerset on a very few occasions, once in central London, but I think that it has been used here. 

 

An intricately carved Ham Hill door surround

The main rebuilt façade, which has very large windows with mullions and transoms, also contains a lot of ironstone and red brick. The dressings are built with a limestone that has a very similar colour to the original window dressings but, although displaying large patches of shelly material, the large ashlar blocks show no sign of bedding structures.

Limestone used for the rebuilt structure

I didn’t spend any time closely examining the stone with my hand lens but, when having a look at the large capping stones to the large gate piers, the limestone is cross-bedded and softer beds within the stone are differentially weathered, which gives it a texture that again suggests that this is Ham Hill stone. 

 

A hamm Hill capping stone to a gate pier

As usual, I had prepared a listed of buildings that required photos on the British Listed Buildings website; however, none of these are built in stone and the next building of interest to this Language of Stone Blog that I encountered was the Grade II Listed Church of St. Mary the Virgin, which is sited in the oldest part of the village. 

 

The tower at St. Mary's church

The lower part of the Tower and the west wall of the Nave with a lancet window date from c.1200 and the mullions of the windows in the south aisle and the vestry from c.1350, but the church was largely rebuilt in the C19 by Sir Gilbert Scott in 1856 and by his son, J Oldrid Scott, in 1879 and the chancel by Sir Thomas Jackson in 1905.

 

A general view of the east end of St. Mary's church

I just had a quick walk around its exterior, noting that it is essentially built in knapped flint with Bath stone dressings, before having a quick look around the churchyard. I took record photos of two Commonwealth War Graves, but I was more interested in a large wall like Portland stone monument, with Christ on the cross and flanked by two angels. 

 

The Hambro family monument

This very unusual and ornate monument, dated 1906, is very surprisingly not mentioned in the Historic England listing description or by Pevsner, but which an internet search suggests relates to several members of the Hambro banking family. 

 

A detail of the Hambro family monument

Continuing anticlockwise around the church and passing the Bath stone porch (1965), I was interested to see that the quoins on the south-west corner of the south aisle are built in a sandstone that has a distinct green/grey patina. 

 

Sandstone quoins on the south aisle

Examining a small piece of stone that I broke off with my fingers using a hand lens, which is quite orange in colour, I can see very many very dark grains of probable glauconite in a fine to medium grained sandstone, but there is no reaction with hydrochloric acid. 

 

A sample of sandstone from a quoin on the south aisle

I finished my brief exploration of Hayes by having a quick look at The Knoll and then walking down Pickhurst Lane, where I came across the ancient Jacob’s Well, where the surrounds are built with what, from my photographs, looks like large blocks of chalk with flints, which is incorporated into an ironstone rubble wall. 

 

Jacob's Well

The ironstone has the same colour and textures as that seen in the boundary wall in the New Inn, but large angular blocks used with the thinly bedded stone are often composed of coarse grained sand. Neither chalk or ironstone make good building stones, with their use being restricted to vernacular architecture near to the quarry sources, but I have no idea of where these were. 

 

Ironstone walling

 

An Exploration of Keston Common

 

A detail of the Blackheath Member of the Harwich Formation

Leaving the Church of St. John the Baptist in West Wickham, where I encountered a variety of building stones that I was not familiar with, I made my way along various public footpaths, which are underlain by the Chalk, until I reached a gentle escarpment that is capped by the Eocene Harwich Formation. 

 

An escarpment capped by the Harwich Formation

Although these are not mapped, the path traversed a sandy soil that is full of very rounded flint pebbles, which are presumably the remnants of sediments that were deposited on the Chalk and, when walking along the path up the escarpment, in a couple of places I noticed exposures that looked very similar to this. 

 

An exposure next to the public footpath

Reaching Heathfield Road, which runs along the edge of the escarpment, I turned south and after 100 metres I encountered the Keston war memorial, which is set in front of a semi-circular hedge with yew trees to each side of it. It was built in 1920 using Portland limestone to the design of the sculptor Sydney March and consists of a monolithic stone pillar buttressed on all four sides with a cruciform top, which has a very unusual form. 

 

Keston war memorial

Continuing down to the junction with Westerham Road, I went in search of the Keston Common gravel pit, which worked the Blackheath Member of the Harwich Formation – interpreted as the deposits of tidal channels and nearshore sand and gravel bars.

 

An exposure of the Harwich Formation

 

It mainly comprises small rounded black flint pebbles, which is in places well cemented and forms a solid rock section that is several metres high. I had never encountered rocks of this type or age before and I was therefore very keen to obtain a specimen for my growing rock collection. 

 

An exposure of the Harwich Formation

Not having my Estwing hammer with me, I looked around for a sturdy piece of wood to try and prise a piece off one of the exposures but, with this not being able to do the job, I instead used a large lump of solid gravel to break off a piece that I could carry home in my rucksack. 

 

A specimen of the Harwich Formation

Although it was not that easy to remove my sample, it has proved to be quite friable and, when transporting it back to Treeton in my suitcase with other well wrapped specimens, many fingernail sized pebbles became dislodged. The Harwich Formation at Keston Common has been described as being cemented with calcite in places but, when the dark brown cement in my sample was tested with hydrochloric acid, there was no reaction. 

 

The Harwich Formation

The pit was opened up to provide gravel for the repair and maintenance of the Westerham Road and other roads in the area. Its dimensions can be quite clearly seen on a LIDAR map, which is approximately 225 metres long and, at is maximum extent, 60 metres wide. 

 

A general view of the gravel pit

Heading north-east towards the Keston Common car park, there are further extensive exposures on the south side of the gravel pit, but I did not collect further samples and was just content to take a few record photographs before exploring the rest of the common. 

A view along the gravel pit

The River Ravensbourne rises from a spring at the junction of clay beneath the sands and gravels of the Harwich Formation, which has been engineered in brick and is called Caesar’s Well - a reference to a legend that Julius Caesar noticed a raven drinking here, when his legions were in great need of water. Certainly, the cold water here was since considered to have great medicinal value and was also very popular for bathing. 

 

Caesar's Well

I didn’t spend much time at the Keston Ponds and didn’t go to look for Keston Bog, which was studied by Charles Darwin, but instead had a quick wander around the common to see if I could see any evidence of the Iron Age embankment and ditch. The common is densely vegetated, which makes landscape features difficult to see, but a linear gorse covered feature, which rises slightly above the heather covered surroundings, is probably a section of this. 

 

A gorse covered Iron Age embankment

Numerous unmarked paths criss-cross the common and I just wandered around until I found one of the principal paths, which sometimes exposed pebbly beds of the Harwich Formation, before heading north to Fishponds Road. Carrying on to Keston village, I stopped at the Greyhound for a quick pint of beer before taking a few photos for the British Listed Buildings website, while walking back to Hayes. 

 

The Harwich Formation exposed in a footpath

 

St. John's Church in West Wickham

 

The Church of St. John the Baptist in West Wickham

The day after a very productive investigation of the ‘urban geology’ of Crystal Palace Park, including the 'dinosaurs' and the 'Geological Illustrations', I set off from Corkscrew Hill in West Wickham to explore the Keston Common gravel pit, a recommended RIGS (Regionally Important Geological Site) where the Blackheath Member of the Eocene Harwich Formation is exposed. 

 

The geology of the area around West Wickham and Keston

As for my walks in South Yorkshire, I had prepared a list of buildings to photograph for the British Listed Buildings website - including the Grade II* Listed Church of St. John the Baptist, which dates to c.1490 and incorporates earlier stonework but was substantially rebuilt in 1844-47 by John Whichcord, with later additions. 

 

The approach to St. John's church

 

Passing through the lychgate, I firstly stopped to look at the organ chamber (1889), which is built in a chequered pattern, with knapped flint nodules and ashlar panels and quoins of a grey shelly limestone that I am not familiar with. 

 

A detail of the masonry to the organ chamber

The thinly bedded rock-faced walling forming the lower part of the organ chamber is also very shelly, with the same colour, but it contains several blocks that are very fine grained and muddy looking and contains no shell fragments. 

 

A detail of the rock-faced walling to the organ chamber

Moving on to the tower, which is offset to the south-west of the nave, this was rebuilt in flint along with the nave and the north aisle as part of Whichcord’s restorations, with Bath stone used for the restored late C15 straight sided arched windows. 

 

The tower

 

The south doorway in the tower also has a surround that is made in Bath stone, which at low level can be seen to be typically cream/beige in colour and contains distinct shelly beds, which are highlighted by differential weathering of the calcite cement. 

 

A detail of the Bath stone to the south door

 

The quoins and cappings to the buttresses, however, are made of an iron rich sandstone with a well developed greyish patina. This is another building stone that I was not familiar with, although West Wickham is not that far from sources of the Cretaceous Wealden sandstones. 

 

Sandstone quoins to a buttress

When having a look at the north side of the church, I found a lump of a fine grained yellow sandstone, which appears to be from a failed moulded section from one of the buttresses. It contains rusty brown and occasional black streaks along the bedding planes and does not react with hydrochloric acid, which would probably rule it out as being Reigate stone. 

 

A sample of fallen sandstone from the north elevation

In 1961, an extension was added to the north elevation and another floor was added to the Lady Chapel, which are again built with knapped flint, with a streaky yellowish sandstone also being used for the dressings. 

 

A view of the north elevation

 

On the north wall of the Lady Chapel, the lower few courses of masonry comprises alternating courses of knapped flint and irregular and roughly squared blocks of an off-white stone, which has a noticeably very pale green tinge and is also used as scattered blocks in the stonework above. 

 

A detail of masonry to the Lady Chapel

Without touching it, I could see that it was much more friable than the sandstone used for the dressings, with the surface generally decaying and laminating, and I found a few pieces lying on the ground that had become detached from the masonry. 

 

A detail of the sandstone masonry to the Lady Chapel

The samples that I collected are extremely fine grained and feel slightly gritty when rubbed with my fingers, but using a hand lens I can’t distinguish any individual grains; however, very fine specks of dark green glauconite are disseminated throughout the stone, which catch the light and the stone reacts strongly with hydrochloric acid. 

 

Samples of calcareous and glauconitic sandstone

Although the Reigate Stone that I have seen is darker and greener, Historic England’s Building Stones of England Atlas for Kent describes it as pale grey to off-white calcareous siltstone and, sometimes, resembling chalk from a distance. From one of the samples, I crushed a small piece that had broken off and covered it with hydrochloric acid until it stopped effervescing, which left a residue of green/grey silt like material. 

 

A glauconitic silty residue

 

After finding a couple of samples of very white oolitic limestone, which I presume have been left behind after restoration of the windows, I was invited by the churchwarden – who I had first met when arriving at the church more than an hour earlier - to take another look at the interior and enjoy a cup of tea before the Annual General Meeting. 

 

White oolitic limestone

 

Even though, as a geologist, I have developed specialist stone identification skills since working in the building restoration industry in London, I have to say that the very fine grained white stone used for the arcade and arches took me quite by surprise and it has made me wonder if these are actually examples of Chalk and not Portland limestone, which is the most common building stone in the capital.

 

Views of the arcade and arches