Sample of Haüyne from Mayen, Eifel Mountains, Rhineland-Palatinate, Germany. Attribution: Rob Lavinsky, iRocks.com

Lazurite is a major component of Lapis Lazuli (or stone of azure) which can be differentiated from Sodalite by the presence of small inclusions of pyrite (FeS₂) giving it an attractive appearance.

Lapis Lazuli
Image: Wikipedia.

It is said that the best Lapis Lazuli has been mined in the Badakhshan province of Afghanistan for a period of c.6,000 years, with other sources located in South America, Russia and India. It was employed as an aphrodisiac by the Romans, and as a treatment for a variety of ailments.

From around the 6^th century A.D. Lapis Lazuli was ground for use as the pigment ultramarine. The brilliant blue permanent colour became much-prized during The Renaissance in Europe when it complemented the purest red vermillion and gold of egg-tempera religious paintings and illuminated manuscripts. Following a laborious extraction process in Afghanistan, the expensive pigment would be imported through the port of Venice. In 1508, the artist Dürer complained that 100 florins (approximately US$20,000) purchased barely a pound of ultramarine, making it more expensive than gold at the time.

Bacchus and Ariadne by Titian uses ultramarine for the robes.
Image: Wikipedia.

Fossil wood is not usually found associated with the rest of the tree (leaves and roots) and identification can be difficult, in these cases the specimens are given a special botanical name. These usually feature the term xylon, along with the plant type it is assumed to be part of, to show that the identification is not bases on whole specimen. (e.g. Arucarioxylon – linked to the Arucaria (Monkey Puzzle) or related genus)

A well-preserved specimen of fossil wood recovered from the Redcar Mudstone Formation near Staithes.

This example of a piece of fossilised wood was found on the beach near Staithes. It has been preserved through a process known as permineralization. The original piece of wood was buried amongst sediment deposited millions of years ago. Over time the minerals from the rock soaked into the wood and replaced the original organic material, whilst keeping the structure of the wood. (in this case it was part of the Redcar Mudstone Formation which was laid down approximately 190 million years ago).

In the specimen shown above you can still clearly see the growth rings hundreds of millions of years after the tree, which grew on land, was transported by rivers to the ancient Tethys Sea where it eventually became incorporated into the sea floor sediment.

©2011 Tees Valley RIGS Group.

In situ fossils in the Redcar Mudstone Formation on Redcar Scar.

The ancient seas that covered Britain millions of years ago are now continually revealing the extinct organisms that once roamed the oceans.

Living within the Tees Valley area provides us with many opportunities and locations to acquire a whole host of these interesting objects. The abundance and diversity of fossils throughout our region is wide and varied. From the famous Jurassic ammonites to the alluring fossil gastropods (sea snails).

Once collected most fossils will need preparing in some way to enhance their natural beauty, this can take many hours even weeks to complete and requires patience and a good eye for detail.

A selection of fossil preparation equipment.

When starting out on preparation most hobbyist collectors will find the use of a rotary tool kit with interchangeable heads immensely versatile. Along with an electric engraver, steel probes and craft knives, these can be helpful for carefully picking away and removing the surrounding sediments. Fortunately the tools just mentioned do not take up much space and can be purchased at very little expense to the user.

A selection of prepared fossils and pertinent literature.

As the collector becomes more proficient in preparation they may eventually want to turn to more robust specialist equipment. There are many tools and supplies on the market to choose from, and one recommendation has to be the pneumatic fossil preparation pen – using compressed air to vibrate a tungsten tip at high speed these can remove the hardest of matrices accurately and effectively in a fraction of the time of other methods. Although professional equipment can prove somewhat expensive the end results almost always outweigh any of the costs.

We would like to thank RIGS Group member Scott Bradley for providing this month’s article.

Please Note: Fossil collecting must be done responsibly to preserve key beds and specimens for the enjoyment of others. Please feel free to collect loose specimens from the beaches, but leave in-situ specimens for the enjoyment of those who follow in your footsteps. Click here to see an informal fossil collecting code.

PLEASE NOTE: Tees Valley RIGS Group cannot be held responsible for the content of external sites.

©2011 Tees Valley RIGS Group.

Site Description

Grid Reference: NZ 751 198 to 783 191
BGS Sheet: 34
OS Sheet: 94

Site Status: Heritage Coast (Not RIGS, other references Nos. 55 and 80). Open access.

Description of Geodiversity: West of Boulby the cliffs rise to over 200m O.D. with the upper parts being formed of the old Boulby and Loftus Alum Quarries. These are SSSIs and, also for access reasons, are described separately. Between Boulby and Cowbar can be found superb sea cliffs and rocky foreshore (scar) with extensive Lias Group exposures. Much historical and industrial archaeological interest. The Cleveland Way passes along the cliff top.

View of Cowbar Nab from Staithes Harbour showing beds of the Staithes Formation capped by glacial 'till'.

Geology

With shallow dips, the strata that can be examined directly in situ are limited to the uppermost beds of the Redcar Mudstone Formation and the base of the Staithes Sandstone Formation. In the past, there were tracks down the cliffs that enabled geologists to study the full section easily.

• Whitby Mudstone Formation: This forms the upper part of the sea cliffs at Boulby with the alum shale quarry at about 130m O.D.
• Cleveland Ironstone and Staithes Sandstone Formations: These form the main cliff faces.
• Redcar Mudstone Formation: This forms the base of the cliffs and the scar. It is part of the Ironstone Shale, the uppermost, informal sub-unit, and consists principally of sandy, silty shale with conspicuous ironstone and calcareous beds and nodule bands (some remarkably like cannon balls).

Geomorphology: The cliffs for about 2 km to the west of Cowbar Nab are capped by glacial till, bedrock being at 40 to 50m O.D. Staithes Beck has cut a deep channel through the till in to the solid strata. On the coast, several landslips and rockfalls can be seen and, in contrast, examples of slow, gradual marine erosion. The marine erosion has been the subject of detailed studies by Agar (1960) and by Durham University in recent years.

Historical geology: This is the site of 19^th century measured sections by Rev. George Young, John Phillips, Lewis Hunton and others.

Industrial Archaeology:

• The cliffs form the seawards edge of Main Seam (Cleveland Ironstone Formation) underground workings of Boulby and Grinkle Ironstone Mines.
• With regard to the alum industry, the landing place (dock) and tunnel (leading to a shaft up to the alum house) are at Hole Wyke (NZ 762 193).

Access

Access to the scar is achieved from the west side of Staithes harbour. Visitors should park in the car park at the top of Staithes Bank (NZ 781 185), follow Staithes Lane north for c.400m before crossing Staithes Beck by bridge (NZ 781 189), then follow the road east to Cowbar Nab.

It is imperative to start no less than 2 hours before low tide and when sea conditions are reasonably calm. Please read the safety information given below and check tide times before setting off.

Access map for Boulby - Cowbar Foreshore showing suggested parking in Staithes and Mean High Water along cliff base.
(Click on map to enlarge.)

General Assessment:

This coastal section is not recommended for general geological studies owing to the access problems. However, the scar at Cowbar Nab is easy to visit at low tide; it forms a small part of the Geologists’ Association Guide No. 34 by Rawson and Wright (locality 1A, page 18 in 3rd edition). It is adventurous to visit the unique alum tunnel (about 2 km to the west) but this must on no account be entered. Children are best taken to the scar on the east side of Staithes, a world-renowned geological location.

Associated Sites

Boulby Alum Quarries (SSSI, Other reference no. 54);
Loftus Alum Quarries (SSSI, Other reference no. 53).
Hummersea (Other reference no. 51).

Safety Information

WARNING: When going along the scar it is imperative to be aware of the tide times and the sea conditions, the sea reaches the cliff foot at high water and the uneven nature of the scar here makes the tide’s inward progress difficult to predict.

The scar is likely to be wet and slippery and there is danger of falling rock from the unstable cliffs. Please remain at least 10 metres from the cliff foot at all times.

A boulder field makes going west beyond Hole Wyke difficult and further westerly progress should be avoided.

Disclaimer: Tees Valley RIGS Group cannot be responsible for the safety of anyone visiting this coastal site. The accompanying map was accurate when this trail was devised in 2011, but these cliffs are prone to landslip through natural processes and paths may be lost.

A NOTE ON FOSSILS

Please feel free to collect loose fossil specimens weathered from their places of original deposition. However, to enable future scientific study, and for the enjoyment of others who may follow in your footsteps, in situ fossils (i.e. those still embedded in their position of original deposition) should not be collected, but their positions noted and details passed on to TVRIGS, a local museum or other similar body.

Please follow the Countryside Code. Do not light fires. Take any litter home.

Supplementary Information

Geology

Structure: The succession is shown in the cross-section. The beds dip at a slight angle to the east at Cowbar Nab and then swing to a more southerly direction at Boulby and beyond with the result that, going westwards from Cowbar Nab, one is gradually descending the Redcar Mudstone Formation succession.

Section through Boulby Cliff showing the dip of the beds to the south.

Whitby Mudstone Formation (marine, in part anoxic): The Hard and Mulgrave Shale Members are present high up in Boulby Cliff. Fallen blocks, mainly of calcareous and sideritic nodules, can be examined on the scar.

Cleveland Ironstone Formation (shallow marine, even shoaled, oxidic, ironstone formed under slow sedimentation): The various ironstone seams can be seen high in the cliff face below Boulby Quarry and particularly the Pecten and Main Seams. Measured sections were made by various geologists using the tracks down to the beach (e.g Bewick, 1861, Chowns, 1968).

Staithes Sandstone Formation (shallow marine, with tidal influences and storm surges) This forms the main part of Cowbar Nab and the lower part of the cliffs westwards. It is about 25m in thickness and consists principally of siltstones and fine-grained sandstones. Beds 1 to 10 of Howarth’s (1955) sequence of 23 beds are accessible on the west side of the harbour and the remainder on the scar to the east. Measured sections are recorded by Tate and Blake (1876, referred to as ‘Colburn Nab’) and Barrow (1888). Modern detailed descriptions are available by, for example, Howarth (ibid), Howard (1985), Knox et al. (1990, Figure 21), Rawson and Wright (1995, Fig. 22) and Hesselbo and Jenkyns (1995, Figures 25 & 26).

Rawson and Wright (ibid) reported that, as seen at Cowbar Nab;

"the dominant lithology in the lower beds is an intensively bioturbated, argillaceous silty sandstone, with occasional thin (1-35 cm), almost unbioturbated fine sandstones. The latter exhibit delicately-preserved bedding structures, including parallel lamination, low-angle cross-lamination and wave ripple lamination. They have erosive bases, sometimes down-cutting to form small channels".

Knox et al. (ibid) comment that the beds form;

"a fining-up sequence of intensely bioturbated sandy siltstones and siltstones containing laterally discontinuous scour-like tempestites".

Fossils are mostly restricted to shelly lenses.

According to Hesselbo and Jenkyns (ibid) individual beds (and particularly the basal ‘Oyster Bed’) can be correlated closely with those exposed at Robin Hood’s Bay.

Redcar Mudstone Formation (marine): At Cowbar Nab the sequence is transitional and the top of the Formation is taken arbitrarily at the base of the ‘Oyster Bed’ (c.30 cm thick). The 20m logged sequence at Cowbar Nab (Knox et al. ibid, Hesselbo and Jenkyns ibid, their figure 25) consists of silty mudstone passing up to muddy siltstone with graded layers and very fine-grained sandstone with the ‘Oyster Bed’ at the top. Bed 21 (in Hesselbo and Jenkyns log at 20m below the ‘Oyster Bed’) is an ooidal ironstone also seen at a similar level in Robin Hood’s Bay and drawn to their attention by J. Senior. Tate and Blake (ibid) also refer to, what may be the same, ooidal ironstone, 8 or 9 inches (~0.2m) thick at Red Nab and Barrow to a ‘white ironstone’ 40 feet 6 inches (12.3m) below the ‘Oyster Bed’.

Chronostratigraphy (from Hesselbo and Jenkyns ibid):

• Staithes Sandstone Formation (Prodactylioceras davoei zone, Oistoceras figulinum subzone (22m), Androgynoceras capricornus subzone (~2m at base).
• Redcar Mudstone Formation (Prodactylioceras davoei zone, Androgynoceras maculatum subzone).

Fossils lists specific to these localities are in Tate and Blake (ibid) and Barrow (ibid) but note that most have since been renamed.

Geomorphology: For about 2 km west of Cowbar Nab, where the cliffs are capped by till, marine erosion consists of a combination of gradual wearing away of material giving rise in particular to a notch just above high water mark, with more substantial joint/fault/bedding-controlled fracturing resulting in rockfalls, and landslippage of the much less coherent till (Agar, 1960, Hemingway, 1982). Slight variations in competence and fracture patterns have resulted in the formation of several small coves and nabs.

Further west, below the higher Boulby Cliffs, there have been several landslips and rockfalls reported during and since the period of alum working that have carried away parts of the works and particularly the tracks down to the shore. Elsewhere, such as, for example, at the western end of the alum quarry (Sallow Tree Plain) the cliff erosion has been limited at least for the past 150 years.

The ground between the Boulby and Loftus Quarries illustrates how the original cliffs may have looked.

The erosion has been studied in recent years by D. Pybus (see Appleton, 2010) and a team from Durham University.

Historical geology: These sea cliffs and Boulby Quarry above are where several 19^th Century and, since then, other geologists haves made measured sections, making use of the tracks down to the shore. That by Louis Hunton (1836) is the most notable as he was one of the first to recognize the importance of collecting fossils in situ and relating the fossils found to the beds in which they occur.

View of the cliffs looking west from Sandy Wyke. Redhouse Nab can be seen slightly left of center.

Industrial History and Archaeology

Alum: The alum works dates from the 1650s. It closed in 1871. The alum house was at NZ 761 190 on the cliff top. There was a liquor conduit from the quarries and tracks and a shaft and tunnel from the house down to the dock at Hole Wyke (see section on Boulby Quarry). The history and industrial archaeology of the alum works has received much attention in recent years.

The tunnel entrance was lost to view for many years owing to landslippage and was rediscovered by Owen (1990) when it reappeared as a result of the eventual erosion of the loose, landslipped material. Owen and others (especially Morris and Whitlock, 2005) have made detailed surveys as more of the archaeology has been revealed. The entrance and associated ‘rooms’ have now been largely lost to the sea and the real start of the tunnel in bedrock is now revealed.
The microbiology of adjacent weathered shale has been studied by Cockell et al., 2011.

Western tunnel in the cliff at Hole Wyke, beneath the former Alum House as seen on 11th March 2007.

Ironstone: The Main Seam of the Cleveland Ironstone Formation has been worked extensively from:

1. Boulby Mine (1903-1934), miners’ drift entrance at NZ 754 191, and
2. Grinkle Mine (1865-1934) drift at NZ 762 177.
   (Boulby ironstone mine main haulage drift is now under the surface buildings of Cleveland Potash mine and the fan shaft is near the railway at NZ 757 179).

The Main Seam typically consisted of a Top Block ~1m, Shale 0.3m and Bottom Block 0.7m. Waste was tipped in to the sea from a drift exit on the sea cliff at NZ 762 190.

It is likely that there was some earlier ironstone working involving the collection of material from the beaches; 2 drifts in the cliff face are shown by the Geological Survey (Yorkshire sheet IX, 1878) at approximately NZ 753 194 and 755 196).

Current mining: Cleveland Potash mine (at NZ 762 184) is of major importance to the local and national economies. Production started in 1973 and production is of the order 1 million tonnes per year of potash as well as common salt. The workings extend over a wide area that includes Boulby Quarry at a depth of around 1100m below sea level.

The discharge tunnel shaft is on the cliff top at NZ 765 190.

Bibliography

Maps

Geological Survey Yorkshire Sheet IX SW, Rockcliff. scale 6 inches to 1 mile, 1878 (Ordnance Survey 1856).
Notes on the Lower Lias, Main Seam and Dogger. 13 Steeping pits at Sallow Tree with cisterns, various buildings and reservoirs. Rockcliff (Pithill) building shown with various paths and reservoirs.

Geological Survey Yorkshire Sheet IXX NW, Boulby, Runswick & Kettleness scale 6 inches to 1 mile, 1899 (Ordnance Survey 1856).
Detailed layout plan of alum house.

Geology & Geomorphology

Agar, R. 1960. Post-glacial Erosion of the North Yorkshire Coast from the Tees Estuary to Ravenscar. Proc. Yorks. Geol. Soc., 32, 409-428.
A valuable study of coastal erosion but subject to much, perhaps mistaken, criticism by Hemingway and others.

Appleton, A. 2010. The Ice Age and its Aftermath in Eastern Yorkshire: One possible interpretation of the evidence. Unpublished review, 33p. (in Whitby Lit. and Phil. Library).
An important contribution collating many views on the ice age and including data on marine erosion.

Barrow, G. 1888. The Geology of North Cleveland. Mem. Geol. Survey, H.M.S.O., London, 101p.
Pages. 9 and 12 show the Redcar Mudstone and Staithes Sandstone Formation sequences.

Bewick, J. 1861. Geological Treatise on the District of Cleveland in North Yorkshire, etc. Reid, Newcastle-upon-Tyne, 194p.
Page 191 shows the measured ironstone section.

Chowns, T. M. 1968. Environmental and diagenetic studies of the Cleveland Ironstone Formation in north-east Yorkshire. Thesis, University of Newcastle upon Tyne.
Page 337 has the measured section at Rockcliff.

Cockell, C. S. et al. 2011. Molecular characterization and geological microenvironment of a microbial community inhabiting receding shale cliffs. Microb. Ecol. , 61, 166-181. Samples taken from shale in the alum tunnel.

Fox-Strangways, C. 1892. The Jurassic Rocks of Britain, Volume 1. Yorkshire. Geol. Survey, H.M.S.O., London, 551p.
Similar to Barrow, 1888.

Hemingway, J. E. 1982. Chapter 1 in Prehistoric and Roman archaeology of north-east Yorkshire ed. D.A. Spratt. BAR British Series 104, 7-31.
A useful account of the eminent professor’s views on glaciation, cliff erosion, etc.

Hesselbo, S. P. And Jenkyns, H. C. 1995. A comparison of the Hettangian and Bajocian successions of Dorset and Yorkshire. From Taylor, P. D. (ed.), Field geology of the British Jurassic, Geological Society, London, 105-150.
Very detailed account. Includes lithic logs of ~20m of the Redcar Mudstone Formation, Ironstone Shale and all the Staithes Sandstone Formation at Staithes (page 138). They report long distance correlation of individual beds, for example, with those at Robin Hood’s Bay and, incredibly, Dorset.

Howard, A. S. 1985. Lithostratigraphy of the Staithes Sandstone and Cleveland Ironstone Formations (Lower Jurassic) of north-east Yorkshire. Proc. Yorks. Geol. Soc. 45, 261-275.
Detailed description, classificationand mode of formation.

Knox, R. W. O’B, Howard, A.S., Powell, J. H. And van Buchem, F. S. P. 1991. Lower and Middle Jurassic Sediments of the Cleveland Basin N. E. England: shallow marine and paralic facies seen in their sequence stratigraphic context. Field guide no. 5, 13th International Sedimentological Congress, Nottingham. 66p.
Day 2 (at Staithes) covers Cowbar Nab including ~6m of the Redcar Mudstone Formation.

Rawson, P. F. and Wright, J. K. 1995. Jurassic of the Cleveland basin, North Yorkshire. From Taylor, P. D. (ed.), Field geology of the British Jurassic, Geological Society, London, 173-208.
Excursion 5 covers Cowbar Nab.

Rawson, P. F. and Wright, J. K. 2000. The Yorkshire Coast. Geologists’ Association Guide No. 34, 3rd revised edition., 130p.
Itinerary 1, Staithes to Port Mulgrave is on pages 16 to 24 and locality 1A is Cowbar Nab.

Tate, R. and Blake, J. F. 1876. The Yorkshire Lias. John Van Voorst, London, 475p.
Pages 89-101, especially page 97, detail the A. capricornus (now P. davoei) zone. Pages 132and 133 show the ironstone section as seen on the path to the shore.

Historical geology

Goldring, D. 2007. Louis Hunton and Loftus Alum Works. Cleveland Industrial Heritage No. 21, 9-15.
Includes a copy of Hunton’s famous section emphasising points of industrial interest.

Hunton, L. 1836. Remarks on a section of the Upper Lias and Marlstone of Yorkshire, etc. Trans. Geol. Soc. London, 5, 215-220.
This is Hunton’s classic paper and includes his section at Boulby, undoubtedly the best by the early 19th Century geologists.

Phillips, J. 1829. Illustrations of the Geology of Yorkshire, etc. Part 1: The Yorkshire coast. Private publication, York, 192p. (2nd Edition 1835 and 3rd Edition 1875, edit R. Etheridge).
Classic account. Section no. 9 shows some detail at Boulby.

Torrens, H. S. and Getty, T. A. 1984. Louis Hunton (1814-1838). English Pioneer in Ammonite Biostratigraphy. Earth Sciences History, 3, 58-68.
A biography stressing the scientific importance of Louis Hunton.

Young, G. and Bird, J. 1822. A Geological Survey of the Yorkshire Coast. Clark, Whitby, 332p. (2nd edition 1828).
The classic measured section at Boulby is on page 134 in the 2nd Edition with the Whitby Mudstone Formation divided into 3 units.

Industrial History & Archaeology

Alum

Barton, P. 2004. Boulby Alum Works: Ways down to the beach. CIAS Newsletter No. 86, 13.
Refers to R. Jackson’s journal items from 1757 to 1783.

Chapman, S. K. 1975. Excavations at the Boulby Alum Works. Cleveland Industrial Archaeology Soc., 2, 23-47.
One of the first industrial archaeological accounts of an alum works.

Chapman, K. 2002. Boulby Alum Works. Chapter 6 in Steeped in History (ed. Miller, I.), North Yorks Moors National Park Authority, 61-74.
A revised account of the 1975 work with major additions and maps by English Heritage.

Featherston, G. R. 2004. Boulby: More on ways down to the beach. CIAS Newsletter No. 86, 13-15.
Adds to Goldring, 2004. See also 18, 19 for photos by J. K. Almond dated 5/8/2004

Goldring, D. 2004. Boulby Alum Works. Ways down to the beach. CIAS Newsletter No. 85, 12,13.
Discussion of the two alum roads to the beach and the shaft and tunnel.

Goldring, D. 2006. Boulby Alum Tunnel. Cleveland Industrial Heritage no. 19, 20.
Brief description of tunnel seen in 2004.

Jecock, M. 2009. A Fading Memory: the North Yorkshire coastal alum industry in the light of recent analytical field survey by English Heritage. Industrial Archaeology Review, 31, 54-73.
General review of the alum industry, including several pictures of Boulby.

Morris, C. H. and Whitlock, S. 2005. Boulby Alum Works’ Tunnel Revisited. Cleveland Industrial Archaeologist No. 30, 29-45.
A detailed industrial archaeological appraisal based on visits between August 2004 and January 2005.

Owen, J. S. 1990. The Tunnel and Shaft for Boulby Alum Works, some features briefly exposed. CIAS Newsletter No. 51, 3-6.
Report on first exposure of the tunnel since being covered by a landslip for many years.

Owen, J. S. 1991. As above, CIAS Newsletter No. 53, page 6.

Owen, J. S. 1995. Continuing clearance at Boulby alum works beach tunnel. CIAS Newsletter No. 62, 3-6.
Further comments.

Owen, J. S. (CIAS Editorial Board). 1998. Cleveland Ironstone. A Memorial to John Owen. CIAS & NYMNP Authority, 103p.
Pages 81-84 are on the Boulby tunnel, etc. based on the CIAS Newsletter references.

Quinn, K. 2009. Boulby Alum. The works diary of George Dodds, 1772-1788. Cleveland Industrial Archaeology Society Research Report No. 9, 76p.
A detailed, primary historical account of operations at Boulby.

Ironstone

Chapman, S. 1997. Boulby Ironstone Mine. Peter Tuffs, Guisborough, 40p.
Account of ironstone mining at Boulby and description of surface remains.

Marley, J. 1857. Cleveland Ironstone, etc. North of England IME Trans., 165-219.
Early, 19th Century ironstone working.

Tuffs, P. 1996. Catalogue of Cleveland Ironstone Mines. Peter Tuffs, Guisborough, 56p.
General details of the mines; booklet (Cleveland Ironstone Series) specifically on Grinkle Mine to be published during 2011.

Abandonment Plans (at Teesside Archives)

Boulby (1 plan), abandoned 2/7/1934. Reference No. 11232

Grinkle (4 plans), abandoned 21/6/1934. Reference No. 11261

Surveyors

Denis Goldring 2011

Please Note: Tees Valley RIGS Group cannot be held responsible for the content of external sites.

©2011 Tees Valley RIGS Group.

Mini Geo-Trail

In the following route description, notes concerned with navigation are show in plum, descriptions of features able to be seen are in black and warnings are given in red.

Please Note: a more detailed description is available in CIAS newsletter No. 100, Feb., 2011 from which this geo-trail is abridged.

Looking west through Loftus Quarries. The quarry floor is Alum Shale, and with Cattersty Cliff in the background.

Geo-Trail Map

Please note that a downloadable annotated version of this map will be made available soon.

Click here to see the Loftus Quarries Geo-Trail Map.
NB: Numbers on map correspond with numbered items in text.

Directions

Please note that numbers shown in black refer to the numbers given on the map.

View east from the car park at Skinningrove showing Hummeresa Cliff which carries the Cleveland Way to Loftus Alum Quarries.

• Car Park: At NZ 713 201 by the mouth of Skinningrove Beck north of the village.
• Make your way across the beck and follow the Cleveland Way up the steep, stepped path and then eastwards where there is a view of the Old Gut dock (marked 1 on the plan). Pass the path down to the shore at NZ 725 198 and North Warren Cottage (Tile Sheds). (2 cisterns (2) are missed unless one deviates along the coastal path). At NZ 735 197 fork left off the Cleveland Way to go down the track in to the quarries.
• 3. Where the coastal path rejoins the track Loftus Quarries come in to view. There is a sandstone quarry (4) and below it a large alum shale quarry (5), its south-eastern face being the location of the murchisonae beds.
• Continue down the track.
• 6. (NZ 737 200) – Foot of ramp track. There are views of tiered quarries to the NW. There were two sets of steeping pits and the cliff edge (7) where there is now a crown hole, the result of jet working. To the east one can leave the path temporarily to examine the alum shale face close by.
• Cross the embankment and follow the path for about 200m to, just before a large fallen block of sandstone, descend down a faint path to the site of the smithy (8).
• 8. (NZ 739 201) – This is the site of the smithy and 2 steeping pits as shown on the 1st edition O.S. map. Little is seen but there are indications of other steeping pits on the cliff edge to the west.
• Go down the short ramp into the ‘kidney’ quarry immediately to the east.
• 9. (NZ 740 201) – ’Kidney quarry’. This quarry is sheltered from the north by an in-situ shale wall that has an opening for waste disposal over the cliff. The O.S. map shows that there was a set of 6 steeping pits here.
• Trek eastwards over the desolate landscape, crossing several cols and quarries (scoops) and passing archaeological locations (10), (11) and (12).


The desolate-looking quarry floor which occurs within Loftus Quarries.

• There is the opportunity to look for; (a) Zone ammonites such as species of Harpoceras and Dactylioceras and (b) the small bivalve Dacryomya ovum regarded by Hunton as characteristic of shale suited to alum making (but these are unlikely to be found; researchers believe that this was the time of slow recovery from an major sea floor extinction event (during formation of the Jet Rock).
• 13. (NZ 744 200) – There is a stone slab platform here, probably the base of a steeping pit, slightly bowed as a result of expansion of the shale beneath it. It is a good spot to view the archaeological remains (14, steeping pits, cistern and lengths of a stone trough) in the quarry further to the east and examine large limestone concretions with Dactylioceras that are close by. The extreme eastern end of Loftus Quarries is not far beyond. Here, the Horse Back (15) is the landslipped ground between Loftus and Boulby Quarries.
• Make your way on a thin path to (16) (NZ 744 199) where a path goes up a steep but safe slope to the Cleveland Way.


View of the back-wall from the east end of the quarries close to the Cleveland Way.

• 17. (NZ 743 199) – This is the site of a reservoir for the alum works, long and narrow in outline.
• Return westwards to Skinningrove along the Cleveland Way. There are at first fine views of the quarries to the north and the rolling dip slope to the south.

Disclaimer: Tees Valley RIGS Group cannot be responsible for the safety of anyone visiting the Loftus site whilst following this geo-trail. The accompanying map was accurate when this trail was devised in 2011, but these cliffs are prone to landslip through natural processes and paths may be lost.

Warning!
Due to the presence of unfenced cliffs we strongly suggest you take extreme care. The area is unsuitable for unsupervised children and all dogs should be kept on a lead. Please use suitable safety equipment when necessary. These cliffs are extremely dangerous and must not, under any circumstances, be climbed.

Taken from the eastern end of the quarries, this image shows the scale of the undertaking here.

Bibliography

See Loftus Quarry Site Description »»

©2011 Tees Valley RIGS Group.

Frosterley Marble is a dark grey to black limestone which has been used as an ornamental stone locally and internationally in churches and buildings such as Durham Cathedral.

Frosterley Marble is not a true marble as it is not a metamorphic rock (true marble is limestone which has recrystallised during thermal or regional metamorphism). Stonemasons use the term marble for some limestones which can take a high polish.

Much of the Frosterley Marble has been worked from quarries around Frosterly, in Weardale, County Durham. Frosterley Marble was formed during the Lower Carboniferous Period (325 million years ago) when the northern Pennines area was closer to the equator. The area alternated between a deltaic and tropical marine depositional environment. The Great Limestone Member was deposited in a marine environment and is in places, 22m thick. The Frosterley Marble forms a fossil rich band in this rock.

Frosterly Marble containing numerous fossil corals.
Image: Carole Rushall.

This photograph shows a boulder of the marble which contains abundant fossil specimens of the coral Dibunophyllum bipartitum. Unlike many corals which live as colonies, Dibunophyllum bipartitum was a solitary coral (it is now extinct). The solitary coral organism had a curved cone shaped calcareous skeleton in which lived a soft-bodied polyp whose tentacles captured organic matter from the sea water. When the organism died, the skeleton settled into the limy ooze on the sea floor which eventually formed limestone.

You can download an illustrated leaflet about Frosterley Marble produced by the North Pennines AONB Partnership by clicking here…

References

Stone, P., Millward, D., Young, B., Merritt, J.W., Clarke, S.M., McCormac, M. & Lawrence, D.J.D. (2010). British Regional Geology: Northern England (Fifth edition). Keyworth, Nottingham: British Geological Survey.

Scrutton, C. (ed) (2004). Northumbrian Rocks and Landscape : A Field Guide. (Second edition). Yorkshire Geological Society.

Our thanks go to Carole Rushall for providing this month’s article.

PLEASE NOTE: Tees Valley RIGS Group cannot be held responsible for the content of external websites.

©2011 Tees Valley RIGS Group.

Site Description

Grid Reference: NZ 736 200 to 744 200
BGS Sheet: 34
OS Sheet: 94
Forwarded as RIGS: 30/09/2003

Site Status: SSSI (Not RIGS, other reference No. 53). Open access (National Trust).

Description of Geodiversity: Extensive former alum quarries of great historical and industrial archaeological interest. The Cleveland Way passes around the southern edge, along the top of the quarry back wall that is nearly 200m O.D. The coastal scenery is impressive.

Looking west through Loftus Quarries from near the Cleveland Way.

Geology

With shallow dips, the Jurassic strata that can be examined directly in situ are limited to beds near to the top of the Redcar Mudstone Formation. Higher beds in the cliff faces can be viewed and examined as fallen blocks.

• Saltwick Formation: This forms the southern back wall of the quarry, some 750m in length and over 30m in height. It is formed predominantly of river channel sandstones. It is difficult to reach and is best examined closely from fallen blocks.
• Dogger Formation: This is about 4m thick and is unique re. coastal exposures. It consists mainly of murchisonae shale and is one reason for the location being SSSI. The apparent transitional beds upwards to Saltwick Formation flood plain deposits are an important source of fossil plants.
• Whitby Mudstone Formation: There are extensive exposures of the lower beds that form the quarry floor (including some Mulgrave Shale).
• Reason for SSSI Status: (1) Occurrence of murchisonae shale, (2) Finding of various reptilian species. (Note: the SSSI status is named as Boulby but the site plan includes both Boulby and Loftus. The murchisonae shale only occurs at Loftus and the pterosaur is also from there. However, the other reptiles may have come from Boulby.)

View from within Loftus Quarries looking west toward Cattersty.

Geomorphology: Several past and potential landslips and rockfalls can be seen and, in contrast, examples of slow, gradual subaerial cliff erosion.

Historical geology: Lewis Hunton’s family were alum makers and estate agents here. Hunton’s study of the stratigraphy at Boulby Quarry, immediately to the east, was a major contribution to the development of geological science.

Industrial Archaeology:

• The quarry is a major alum site with several stages of development. However, industrial archaeological remains are somewhat sparse especially in comparison with Boulby.
• The quarries are underlain by the extensive underground workings of the Main Seam (Cleveland Ironstone Formation) of Loftus Mine that are exposed along the sea cliffs. Jet workings are also present along the sea cliffs not far below the lowest alum levels.

Access

The main access point is at NZ 735 198 where a track into the quarries branches off the Cleveland Way. This point can be reached on foot in various ways but particularly by following the Cleveland Way eastwards from Skinningrove where there is parking (see the mini-geotrail).

Access map for Loftus Quarries showing suggested parking in Skinningrove, extent of Boulby SSSI and North York Moors National Park.
(Click on map to enlage)

General Assessment:

The quarries are an excellent venue for demonstrating Lower and Middle Jurassic geology and industrial archaeology (alum workings).

Associated Sites

Boulby Alum Quarries (SSSI, other reference no. 54);
Hummersea sea cliffs and foreshore (Heritage Coast, other reference no. 51);
Boulby and Cowbar Nab Cliffs ((RC5, other reference no. 80);

Safety Information

PLEASE NOTE: Due to the presence of high unfenced cliff faces we suggest that this site is not suitable for visits by unsupervised children. Please remain well away from the cliff edge and ensure any dogs are kept on a lead. Because of their unstable nature these cliffs must not, under any circumstances, be climbed.

Disclaimer: Tees Valley RIGS Group cannot be responsible for the safety of anyone visiting this coastal site. The accompanying map was accurate when this trail was devised in 2011, but these cliffs are prone to landslip through natural processes and paths may be lost.

A NOTE ON FOSSILS

Please feel free to collect loose fossil specimens weathered from their places of original deposition. However, to enable future scientific study, and for the enjoyment of others who may follow in your footsteps, in situ fossils (i.e. those still embedded in their position of original deposition) should not be collected, but their positions noted and details passed on to TVRIGS, a local museum or other similar body.

Please follow the Countryside Code. Do not light fires. Take any litter home.

Supplementary Information

Geology

Structure: The succession is shown in the accompany section. The beds dip about 3° to the south.

Section through Loftus Quarries showing the general dip of the beds to the south.

Saltwick Formation (deltaic/alluvial): This forms the impressive back wall of the quarry and consists principally of massive lenses of river channel sandstone. It is generally difficult to reach owing to the fallen rock. Blocks, some extremely large, can be readily examined showing sedimentary structures such as cross-bedding and the imprints of plant remains.

Dogger Formation (marine incursion): The peculiar nature of this Formation at this locality was, perhaps, first noticed by Hunton (1836) who reported 10ft (3m) of shale at the top of the succession distinct from the Alum Shale. Later, Tate and Blake (1876, page 26) and Barrow (1888, page 43) described the section in some detail. Tate and Blake provide a lengthy fossil list of 20 species from bed 11, a 3 inch (7.5cm) thick bed described as ‘impure limestone dogger’ and reported Ludwigia murchisonae (an Aalenian zone ammonite) from bed 10 (‘shale’, 1 ft 6 ins (46 cm)) that is directly above.

The geology was subsequently investigated by Black (1929 and 1934) and has been summarised by Rastall and Hemingway (1940). Black’s section is also shown in the British Regional Geology, East Yorkshire and Lincolnshire (1948, page 38). Black records about 11ft (3.3m) of murchisonae beds with a basal ‘pebble bed’ (mainly of mudstone) overlain by ferruginous shale with bands of siderite mudstone nodules, some of which are fossiliferous with the basal bed carrying the zone fossil. The beds are overlain, apparently without any break, by flood plain deposits ascribed to the Saltwick Formation and including coaly shale and fossil plant beds. They are also cut out laterally by channel sandstone that passes laterally into a thin bed of sandstone above the plant-rich layers.

The locality is described by Tate and Blake as “…due north of Upton…”, i.e. at the extreme western end of the quarries at NZ 737 198, but is now rather difficult to reach and is in a poor state.

No comparable localities are known along the coast but similar beds are found inland especially at Cold Moor where they overlie the limestone-rich facies type that is also of murchisonae age. This implies that at Loftus Quarries there is a considerable gap in the stratigraphic succession with several missing time zones at the level of the pebble bed.

Alum Shale and Mulgrave Shale Members (marine, recovering from the anoxic event of the Jet rock): Some 30m of beds are exposed at various sub-quarry levels along the northern, seawards side. They probably belong to the Hard Shale sub-unit of the Member and beds below, the Bituminous Shale sub-unit of the Mulgrave Shale. They consist of weathered, friable, grey, iron-stained, poorly bedded, flaky shale with vertically disposed, small-scale jointing. Fossils, chiefly poorly preserved belemnites, are uncommon but, when seen, may be present in clusters. Small acicular crystals of iron-stained gypsum are common.

Occasional beds of lighter grey, calcareous, sometimes septarian, nodules are common and in places the bare shale surface is littered by loose pieces of these nodules. However, so far, Howarth’s (1962) detailed lithostratigraphic succession has not been elucidated. It is likely that the beds exposed belong to the lower part of the Member (the Hard Shale sub-unit) and to the upper part of the Mulgrave Shale Member.

The upper sequence of the Alum Shale Member is mostly obscured by waste dumps and rock falls but can be seen from a distance in some places. Black (ibid) and Rastall and Hemingway (ibid) report shale with cementstone nodules (and typical Alum Shale ammonites) overlain by about 2 feet (0.6m) mainly consisting of ‘chocolate mudstone’, of ‘doubtful age’, below the Dogger Formation pebble bed.

View Looking west from the eastern end of the quarries showing faces of Alum Shale.

Fossil reptiles: The SSSI description refers to type specimens of two plesiosaurs (Eretmosaurus maccroptera and Thaumatosaurus zetlandicus), one ichthyosaur (Ichthyosaurus crassimonus) and one pterosaur (Parapsicephalus (Schaphognathus) purdoni). The pterosaur was found at Lofthouse (Loftus) by the Rev. D. W. Purdon in 1881 and was described by Newton (Phil. Trans. Royal Soc. London, 1888). It is now at the British Geol. Survey, Keyworth (information from the Pterosaur data base where there are photos).

Geomorphology: The back wall of the quarry has been subject to rock falls and there is now much debris at its foot. At the top, on the Cleveland Way there are open fissures with the quarry wall being in a poor state.

At quarry level on the seawards edge there have been several landslips but also stretches of cliff where there has been little erosion since the publication of the first Ordnance Survey maps. The ground between the Boulby and Loftus Quarries illustrates how the original cliffs looked.

Historical geology: As noted above, Hunton (1836) published an important paper concerning the collection of fossils in-situ and their stratigraphic significance. Hunton’s home was at Hummersea House and he must also have been familiar with Loftus Quarries although his section refers to Rockcliff, Boulby where there was, at the time, an easy track down to the beach.

Industrial History and Archaeology

Alum: The alum works was started in the mid-17^th century and closed in about 1860. There was a major redevelopment about 1800 when a new alum house was constructed by Hummersea beach. The history and industrial archaeology of the alum works has received much attention in recent years and, in particular, there is the major survey by English Heritage (Hunt et al. 2004). The main sites are included in the mini-geotrail.

Ironstone: The Main Seam of the Cleveland Ironstone Formation has been worked extensively under the quarries as part of Loftus Ironstone Mine, the surface works of which are now the Cleveland Ironstone Mining Museum at Skinningrove (at NZ 712 193). The seams typically consisted of a Bottom Block (1.2m) and Top Block (1.5m) separated by a dogger or shale parting up to 0.2 m (but thicknesses varied across the reserve). Tuffs (1996) gives a brief and Chapman (1998) a detailed description.

Literature References

Maps

Geological Survey Yorkshire Sheet IX SW, scale 6 inches to 1 mile, 1878 (Ordnance Survey 1856).
his shows a large number of industrial features that have since disappeared such as several sets of steeping pits and an outline plan of the alum house.

Excursion Guides

Goldring, D. 2001. Along the Scar. Peter Tuffs, Guisborough, 145p. See pages 59-65.

Goldring, D. 2010. Guided Walk to Loftus Alum Quarries 24th July, 2010. CIAS Newsletter No. 100. See pages 5-11.
The mini-geotrail is based on this.

Geology

Barrow, G. 1888. The Geology of North Cleveland. Mem. Geol. Survey, H.M.S.O., London, 101p.
Pages. 9 and 12 show the Redcar Mudstone and Staithes Sandstone Formation sequences. The Main Seam ironstone section at the Old Gut is on page 19.

Black, M. 1929. Drifted plant beds of the Upper Estuarine Series of Yorkshire. Quart. Journ. Geol. Soc. 85.

Black, M. 1934. Sedimentation of the Aalenian rocks of Yorkshire. Proc. Yorks. Geol. Soc., 22, 265-279.
Details of the Dogger Formation succession

Goldring, D. 2011. Geological background to the North Yorkshire alum industry.
Paper in preparation.

Fox-Strangways, C. 1892. The Jurassic Rocks of Britain, Volume I Yorkshire. Geol. Survey, H.M.S.O., London, 551p.
Similar to Barrow, 1888.

Howarth, M. K. 1962. The Jet Rock Series and the Alum Shale Series of the Yorkshire coast. Proc. Yorks. Geol. Soc., 33, 381-418.
The main bed by bed description of the strata, followed by subsequent researchers.

Rastall, R. H. & Hemingway, J. E. 1940. The Yorkshire Dogger, 1. The Coastal Region. Geol. Mag., 77, 177-197 & 257-275.
This is the main detailed description of the Dogger Formation for the Cleveland coast. Pages 192 and 193 refer to the Loftus section.

Tate, R. and Blake, J. F. 1876. The Yorkshire Lias. John Van Voorst, London, 475p.
he measured section and fossil list of the Dogger Formation is on page 26 (cliff due north of Upton hamlet). Pages 132 and 133 show the ironstone section as seen on the path to the shore at Boulby.

Wilson, V. 1948. British Regional Geology, East Yorkshire and Lincolnshire. HMSO, 94p.
Black’s section is reproduced on page 38.

Historical Geology

Hunton, L. 1836. Remarks on a section of the Upper Lias and Marlstone of Yorkshire, etc. rans. Geol. Soc. London, 5, 215-220.
This is Hunton’s classic paper and includes his section at Boulby, undoubtedly the best by the early 19th Century geologists.

Torrens, H. S. and Getty, T. A. 1984. Louis Hunton (1814-1838). English pioneer in ammonite biostratigraphy. Earth Sciences History, 3, 58-68.
biography stressing the scientific importance of Louis Hunton.

Industrial History & Archaeology

Alum

Goldring, D. 2007. Louis Hunton and Loftus Alum Works. Cleveland Industrial Heritage, No. 21, 9-15.
Includes a copy of Hunton’s famous section emphasising points of industrial interest.

Hunt, A. et al. 2004. Loftus alum works, Redcar and Cleveland, Cleveland. An archaeological and historical survey. English Heritage, Survey Report A1/02/2004, 67p.
This is a major survey of Loftus Quarries with detailed plans covering the whole site. It is a pity that there is not more geology, that there are few survey levels and that information on the early 6 inches to 1 mile O. S. maps is missing.

Jecock, M. 2009. A Fading Memory: The North Yorkshire coastal alum industry in the light of recent analytical field survey by English Heritage. Industrial Archaeology Review, 31, 54-73.
General review of the alum industry.

Miller, I. 2002. The Manufacture of Alum: The Collated Evidence. Chapter 9 in ed. I. Miller, Steeped in History. The alum industry of North-East Yorkshire. NorthYorks Moors National Park Authority. 107-120.
A review that includes several references and photos of Hummersea going back to 1993.

Owen, J. S. 1986. Rutways before railways on the Yorkshire coast, with details of twelve sites between Saltburn and Scarborough. CIA No. 18, 23-32.
John Owen’s main record of rutways, etc.

Owen, J. S. (compiled by CIAS editorial board). 1998. Rutways and some other coastal features. (In Cleveland Ironstone (memorial volume)) 75-79. CIAS & NYMNP Authority, 103p
A compilation of John Owen’s finds.

Ironstone

Abandonment Plan (at Teesside Archives) Loftus (1 plan), abandoned 27/06/1959. Reference No. 15168.

Chapman, S. 1998. The Loftus mines, Skinningrove. Peter Tuffs Publications, 100pp.
Account of ironstone mining at Boulby and description of surface remains.

Tuffs, P. 1996. Catalogue of Cleveland Ironstone Mines. Peter Tuffs, Guisborough, 56p.
General details of Loftus mine.

Mini Geo-trail

Click here to view the Loftus Quarries Mini Geo-Trail »»

Surveyors

Denis Goldring 2011

©2011 Tees Valley RIGS Group.

PLEASE NOTE: Tees Valley RIGS Group cannot be held responsible for the content of external sites.

Mini Geo-Trail

In the following route description, notes concerned with navigation are show in plum, descriptions of features able to be seen are in black and warnings are given in red.

Geo-Trail Map

Hummersea mini geo-trail location map showing numbered features of interest and parking (P). Adapted from Along the Scar (2001) (See references).
(Click on map to enlarge)

Directions

• Car Park: On the west side of the Skinningrove Beck mouth at NZ 712 201. Cross the village front and go over the bridge to reach the slipway on the eastern side of the valley.
  
  

  Looking east from the car park across the beck mouth at Skinningrove showing Hummersea Cliff.

  1. There are views of the village, the slag cliffs topped by the iron and steelworks, the incline and the jetty used for the export of pig iron. Further afield, Huntcliff can be seen with the present day mineral railway and the Guibal fanhouse (a much better view is gained by going a little way up the Cleveland Way steps).

 



Looking west from Hummersea Scar showing the slag cliffs (center left), jetty and Cattersty Cliff (midground) and Huntcliff (background).

• Go on to the beach and eastwards on the scar.
  2. The cliff line follows the strike (i.e. the beds are apparently horizontal as seen) and the same strata can be followed for some distance. The ironstone seams gradually appear as the cliffs become higher with the Main Seam at c.60m. At scar level the Redcar Mudstone Formation, silty shale, has thin beds and nodules of ironstone. Rounding Hummersea Point there are two deep clefts in the cliffs, the result of jointing and faulting. There are good examples of rutways on the scar.

 




Members of the RIGS Group and others explore the perched boulders between Skinningrove and Hummersea Steps.

• Continue on to Hummersea Beach, the steps and the ‘kiln’.
  3 The various remains of alum operations noted above can be viewed and the variety of pebbles appreciated.

 




Members of the RIGS Group and others discuss Hummersea Cliff from the beach below Hummersea Steps.

• Continue on the usually wet scar to the Old Gut.
  4. The remains of the dock can be investigated and the ironstone seams of the landslip.The seams have an apparent dip of c.80º to the south! The old line of a track up the cliff can be made out.
  Warning: It’s possible for the intrepid to go on eastwards a short way and, perhaps, find the ‘third dock’ but beware of the incoming tide; there is no easy way up the cliff short of Staithes.

 

• Return to Hummersea Beach and climb the steps and path to the Cleveland Way.
  5. View the geomorphology of this area (much of which has now been donated to Tees Valley Wildlife Trust). The scarp line of Saltwick Sandstone is set back from the coast and is paralleled underground by the subcrop of the Cleveland Ironstone Formation (see the geological map). The, therefore, deep embayment is infilled by till that is much landslipped on the seawards side. The Snilah Ponds, still shown on modern maps, are said to have been infilled by material from Boulby Potash Mine development.

 




View of Hummersea Cliff and Scar (foreground) with Skinningrove Beck mouth and Cattersty Cliff (beyond). The swing in the strike of the beds on the scar is clearly seen. Warsett Hill and Hunt Cliff are in the background with the Guibal fanhouse visible on the cliff top

• Return to Skinningrove along the cliff top following the Cleveland Way. Hummersea House, the home of the Louis Hunton, the famous geologist, is in view to the south-west prior to rounding Warsett Hill.

Disclaimer: Tees Valley RIGS Group cannot be responsible for the safety of anyone visiting the Hummersea site whilst following this geo-trail. The accompanying map was accurate when this trail was devised in 2011, but these cliffs are prone to landslip through natural processes and paths may be lost.

THINK SAFETY

We suggest that you check tide times and weather conditions before setting off, and do so only on a falling tide. Take great care and remain at least 10m away from the cliff base as the cliffs are prone to rock falls. Use appropriate safety equipment where necessary.

Bibliography

See Hummersea site description page »

©2011 Tees Valley RIGS Group.

PLEASE NOTE: Tees Valley RIGS Group cannot be held responsible for the content of external sites.

Site Description

Grid Reference: NZ 755 195
BGS Sheet: 34
OS Sheet: 94
Forwarded as RIGS: 30/09/2003

Site Status: SSSI (RIGS Site Ref: RC5, Site No. 54 [ * Under Review * ]). Open access.

Please Note: The quarry is situated on private land, however spectacular views can be found by walking along the Cleveland Way and other adjacent public footpaths.

Description of Geodiversity: Extensive former alum quarry of great geological, scientific, historical and industrial archaeological interest. The Cleveland Way passes around the southern edge and along the top of the quarry back-wall that rises to over 200m O.D. The coastal scenery is impressive.

View of Boulby Quarries (foreground) showing Cowbar Nab near Staithes (background). Taken from the Cleveland Way above Sallow Tree Plain.

Geology

The quarries form the upper part of a virtually complete Jurassic succession ranging from the Lower Jurassic Redcar Mudstone Formation on the foreshore to the Middle Jurassic Saltwick Formation at the top. The quarried beds of interest to the alum industry constitute principally the Alum Shale Member of the Whitby Mudstone Formation. The beds exposed in the quarries are:

• Saltwick Formation: This forms the southern back-wall of the quarry, some 600m in length and up to 30m in height. It is formed predominantly of river channel sandstones. These exposures are difficult to reach and best examined more closely within the numerous fallen blocks.
• Dogger Formation: This Formation is about 1m thick and consists mainly of siliceous ironstone. It is sometimes absent as a result of washouts, and is now poorly exposed.
• Alum Shale Member: There are good exposures of the lower beds of shale (Whitby Mudstone Formation) which form the quarry floor especially at the western end.
• Reasons for SSI Status: Although the SSSI is named Boulby it actually includes both Boulby and Loftus Quarries. Two significant features, the murchisonae shale facies of the Dogger Formation and the finding of pterosaur remains in the Alum Shale, are at Loftus Quarries but it is likely that other reptilian remains were also found at Boulby.

Geomorphology: Several past and potential landslips and rockfalls can be seen and, in contrast, examples of slow, gradual sub-aerial cliff erosion.

Historical geology: This is the site of 19^th century measured sections by Rev. George Young, John Phillips, Lewis Hunton and others.

Industrial Archaeology:

• The quarry was a major alum site with at least two stages of development – mid-17^th to late-18^th century and late-18^th to late-19^th centuries. Across the site can be found the remains of calcining places, steeping pits, buildings, reservoirs, liquor conduits, etc. The stone revetments at the western end are most impressive.
• There are small ironstone trials of the Top Seam (Dogger Formation).
• The quarry is underlain by the extensive underground workings of the Main Seam (Cleveland Ironstone Formation) that are exposed along the sea cliff face.

Access

Access map for Boulby Quarries showing extent of SSSI and suggested parking.
(Click on map to enlage)

The easiest access is from the east along the Cleveland Way. A minor road off the A174 affords suitable parking.

General Assessment:

The quarry is an excellent venue for demonstrating Lower and Middle Jurassic geology, recent geomorphology, historical geology and industrial archaeology (alum and ironstone workings). The high cliffs require care.

Associated Sites

Boulby Sea Cliffs and Foreshore (North Yorkshire Heritage Coast, RC5, other reference 80.);
Loftus Alum Quarries (SSSI, other reference no. 53).

Safety Information

PLEASE NOTE: Due to the presence of high unfenced cliff faces we suggest that this site is not suitable for visits by unsupervised children. Please remain well away from the cliff edge and ensure any dogs are kept on a lead. Because of their unstable nature these cliffs must not, under any circumstances, be climbed.

Please follow the Country Code. Do not light fires. Take any litter home.

In situ fossils must not be collected, but their positions noted and details passed on to TVRIGS, a local museum or other similar body. Scattered fossils already weathered from the rock may be collected freely.

Supplementary Information

Geology

Structure: The succession is shown in the accompany section. The beds dip about 3° to the south.

Section through the cliff and quarry demonstrating the gentle dip of the beds.

Saltwick Formation (deltaic/alluvial): This forms the impressive back-wall of the quarry and consists principally of massive lenses of river channel sandstone. It is generally difficult to reach owing to fallen rock. Blocks, some extremely large, can be readily examined showing sedimentary structures such as cross-bedding and the imprints of plant remains.

Dogger Formation (marine incursion): This is about 1m in thickness and consists mainly of siliceous ooidal ironstone. However, at the eastern end it is described as ooidal siderite mudstone overlain by dark mudstone with similar mudstone nodules, as a clear result of lateral transition (Rastall and Hemingway, 1940). It is now poorly exposed. Blocks of ironstone can be examined that form a roughly laid wall by an old trial adit.

Alum Shale Member (marine): Some 10m of beds are exposed at various sub-quarry levels especially at the western (Sallow Tree Plain) end of the workings around the stone revetments. They consist of weathered, friable, grey, iron-stained, poorly bedded, flaky shale with vertically disposed jointing on the small scale. Fossils, chiefly poorly preserved belemnites, are uncommon but when seen may be present in clusters. Small acicular crystals of iron-stained gypsum are common. Occasional beds of lighter grey, calcareous, sometimes septarian, nodules can be found but, so far, Howarth’s (1962) detailed lithostratigraphic succession has not been elucidated. It is likely that the beds exposed belong to the lower part of the Alum Shale Member (the Hard Shale sub-unit) or even the upper part of the Mulgrave Shale Member.

Revetment walls at the west end of the site with Cowbar Nab in the background.

Geomorphology: The back-wall of the quarry has been subject to rock falls and there is now much debris at its foot. At the top, on the Cleveland Way there are open fissures with the cliffs being in a poor state. At quarry level on the seawards side there have been several landslips reported during and since the period of working that have carried away parts of the alum works and particularly the former tracks down to the shore. Elsewhere, such as for example at the Sallow Tree Plain (western end) steeping pits the cliff erosion has been limited. The ground between the Boulby and adjacent Loftus Alum Quarries illustrates how the original cliff profile looked.

Historical geology: Boulby Quarry and the sea cliffs beneath (making use of the tracks down to the shore) are where several 19^th century and, more recently, geologists such as Chowns made measured sections. That by Lewis Hunton (1836) is the most notable as he independently recognized the importance of collecting fossils in-situ, and relating the fossils found to the beds in which they occur bolstering the emerging concept of biostratigraphy.

View of Boulby Quarry and cliff as seen from Bias Scar toward Staithes.

Industrial History and Archaeology

Alum: The alum works was started in the 1650s at the eastern (Rockhole Hill) end of the quarry, redeveloped at the western (Sallow Tree Plain) end in 1784, and eventually closed in 1871. The alum house was about 0.5km to the south-east and, as well as tracks, there was a shaft and tunnel here connecting the house to the dock at Hole Wyke (see Boulby Sea Cliffs and Foreshore). The history and industrial archaeology of the alum works has received much attention in recent years (see references).

Ironstone: The Main Seam of the Cleveland Ironstone Formation has been worked extensively under the quarries from:

• (a) Boulby Mine, miners’ drift entrance at NZ 754 191, and
• (b) Grinkle Mine drift at NZ 762 177.

Boulby Ironstone Mine main haulage drift is now under the surface buildings of Cleveland Potash Mine, and the fan shaft is near the railway at NZ 757 179. The Main Seam typically consisted of a Top Block ~1m, Shale 0.3m and Bottom Block 0.7m. Waste was tipped in to the sea from a drift exit on the sea cliff at NZ 762 190. There are two trials of the Top Seam ironstone of the Dogger Formation, one within the quarries and one a short distance to the east (at NZ 758 190).

Current mining: Cleveland Potash Mine (at NZ 762 184) is of major importance to the local and national economies. Production started in 1973 and is of the order 1 million tonnes per year of potash (sylvinite) as well as rock salt (halite). The workings extend over a wide area that includes Boulby Quarry at a depth of around 1100m below sea level.

Literature References

Maps & Plans

Geological Survey Yorkshire Sheet IX SW, Rockcliff, scale 6 inches to 1 mile, 1878 (Ordnance Survey 1856).
Notes on the Lower Lias, Main Seam and Dogger. Shows 12 Steeping pits at Sallow Tree with cisterns, various buildings and reservoirs. Rockcliff (Pithill) building shown with various paths and reservoirs.

Geological Survey Yorkshire Sheet IXX NW, Boulby, Runswick & Kettleness, scale 6 inches to 1 mile, 1899 (Ordnance Survey 1856).
Shows outline plan of the alum house.

Ironstone Abandonment Plans (at Teesside Archives)

Boulby (1 plan), abandoned 2/7/1934. Ref. 11232
Grinkle (4 plans), abandoned 21/6/1934. Ref. 11261

Barrow, G. 1888. The Geology of North Cleveland. Mem. Geol. Survey, H.M.S.O., London, 101p.
Official memoir. Page. 9 shows the Main Seam ironstone section made on ‘the old road now slipped away’. Pages 42 and 43 show Dogger sections.

Chapman, S. K. 1975. Excavations at the Boulby Alum Works. Cleveland Industrial Archaeology Soc., 2, 23-47.
One of the first industrial archaeological accounts of an alum works.

Chapman, S. 2005. Boulby Alum Works Visit. C.I.A.S Newsletter No. 88, 11-17.
Industrial archaeological excursion guide.

Chapman, K. 2002. Boulby Alum Works. Chapter 6 in ‘Steeped in History’ (ed. Miller, I.), North Yorks Moors National Park Authority, 61-74.
A revised account of the 1975 work with additions and maps by English Heritage.

Fox-Strangways, C. 1892 The Jurassic Rocks of Britain, Volume 1. Yorkshire. Geol. Survey, H.M.S.O., London, 551p.
Similar to Barrow, 1888.

Goldring, D. 2001. Along the Scar. Peter Tuffs, Guisborough, 145p.
See pages 59 to 65.

Goldring, D. 2007. Louis Hunton and Loftus Alum Works. Cleveland Industrial Heritage No. 21, 9-15.
Includes a copy of Hunton’s famous section emphasising points of industrial interest.

Hunton, L. 1836. Remarks on a Section of the Upper Lias and Marlstone of Yorkshire, etc. Trans. Geol. Soc. London, 5, 215-220.
This is Hunton’s classic paper and includes his section at Boulby, undoubtedly the best by the early 19th Century geologists.

Jecock, M. 2009. A Fading Memory: The North Yorkshire coastal alum industry in the light of a recent analytical field survey by English Heritage. Industrial Archaeology Review, 31, 54-73.
General review of the alum industry, including several pictures of Boulby.

Marley, J. 1857. Cleveland Ironstone, etc. North of England IME Trans., 165-219.
Early, 19th Century ironstone working.

Miller, I. 2002. Steeped in History North York Moors NPA.

Osbourne, R. 1998. The Floating Egg Pimlico.

Phillips, J. 1829. Illustrations of the geology of Yorkshire, etc. Part 1 The Yorkshire coast. Private publication, York, 192p. (2nd Edition 1835 and 3rd Edition 1875, edit R. Etheridge).
Classic account. Section no. 9 shows some detail at Boulby.

Quinn, K. 2009. Boulby Alum: The works diary of George Dodds, (1772-1788). Cleveland Industrial Archaeology Society Research Report No. 9, 76p.
A detailed, primary historical account of operations at Boulby.

Rastall, R. H. & Hemingway, J. E. 1940. The Yorkshire Dogger, 1. The Coastal Region. Geol. Mag., 77, 177-197 & 257-275.
This is the only detailed description of the Dogger Formation for the Cleveland area. Pages 191 and 192 refer to Boulby sections and pages 263 and 264 to the petrography.

Tate, R. and Blake, J. F. 1876. The Yorkshire Lias. John Van Voorst, London, 475p.
Pages 132 and 133 show the ironstone section as seen on the path to the shore. Pages 170 and 175 detail the section in part of the Whitby Mudstone Formation.

Torrens, H. S. and Getty, T. A. 1984. Louis Hunton (1814-1838). English Pioneer in Ammonite Biostratigraphy. Earth Sciences History, 3, 58-68.
A biography stressing the scientific importance of Louis Hunton.

Tuffs, P. 1996. Catalogue of Cleveland Ironstone Mines. Peter Tuffs, Guisborough, 56p.
General details of the mines.

Young, G. and Bird, J. 1822. A Geological Survey of the Yorkshire Coast. Clark, Whitby, 332p. (2nd edition 1828).
The classic measured section at Boulby is on page 134 in the 2nd Edition with the Whitby Mudstone Formation divided into 3 subdivisions.

Surveyors

Denis Goldring 2011

©2011 Tees Valley RIGS Group.

Derived from the Latin Argilla – meaning ‘clay’, this group of rocks primarily comprise particles of the finest grade, including clay- and silt-sized clasts up to ¹/₁₆ mm in diameter. They may be divided into subclasses of shales, mudstones and siltstones.

Both shale and mudstone are composed of the finest particles of sediment less than ¹/₂₅₆ mm in diameter, and can be distinguished by the way in which they cleave. Shale is generally finely-laminated and fissile, able to be split easily along its bedding planes, mudstone on the other hand has no preferred axis of cleavage and tends to exhibit a ‘blocky’ fracture¹. Siltstone follows similar principles of cleavage but comprises grains between ¹/₂₅₆ mm and ¹/₁₆ mm in diameter.

Shales of the Whitby Mudstone Formation (grey) form the foreshore and lower cliff beneath Middle Jurassic sandstone (yellow) at Rosedale Wyke. The remains of Kettleness alum quarries form the headland in the background.

Clay minerals (alumino-silicates) make up the bulk of such rocks and may include kaolinite, illite, chlorite and montmorillonite-smectite. Argillites are rarely pure but include a mixture of minerals. For example the Alum Shale Member of the locally exposed Whitby Mudstone Formation contains all four of the above mentioned clay minerals plus pyrite (FeS₂), quartz (SiO₂), siderite (FeCO₃), calcite (CaCO₃), collophane (apatite), goethite (FeO(OH)), gypsum CaSO₄ • 2(H₂O), jarosite (KFe³⁺₃(OH)₆(SO₄)₂), mica, feldspar, zircon and anatase. The latter three minerals in only minor amounts.

Shales and mudstones may also frequently contain inclusions in the form of calcium carbonate, siderite or other minerals. These features form after deposition of the originating sediment during the process of lithifaction. They grow in-situ when minerals distributed through the body of the deposit are drawn toward a single point through ionic transportation. Often a shell fragment or fossil will provide a nucleating point around which the inclusion develops as the accreting mineral is drawn from the surrounding sediment. In the image below showing the Jet Rock Member at Rosedale Wyke, bedding can be seen to pass around the outside of weathered calcium carbonate nodules.

Laminations in the Jet Rock Member of the Whitby Mudstone Formation passing around weathered limestone nodules.

Argillites are all sedimentary in origin, their components being either water or wind-borne. They are the products of fairly low energy environments such as deep sea floor, tidal flats, lakes and (in the case of loessite – lithified wind-borne rock dust from a number of sources) continental environs. They may occur in a variety of colours ranging from the dark red-brown, blue-grey, or tea green Triassic deposits to the light brown or black Bituminous Shale and Jet Rock Members of the Lower Jurassic containing hydrocarbons.

Red-Brown Permo-Triassic mudstone as seen at Seaton Carew.

The fine-grained nature of argillites make them ideal for the preservation of detailed fossil specimens. One example of such excellent preservation is the enigmatic suite of remains discovered in the Burgess Shale of Canada by Charles Doolittle Walcott (1850-1927) in the early 20th century². These Middle Cambrian fossils were reappraised in the 1970s and found to represent the remains of creatures with a number of body plans previously unknown to science such as Marrella a kind of extinct crustacean.

Marrella - An extinct crustacean from the Burgess Shale of Canada with no modern day relatives.

Historically, argillites have been exploited locally for a number of reasons. Millions of tons of Lower Jurassic (Toarcian) Alum Shale were quarried and processed to serve the local alum trade at over twenty sites in and around the Tees Valley. At Ravengill, near Commondale, Middle Jurassic (Aalenian) mudstone was quarried and milled for the brick and tile trade.

When sedimentary argillites become altered (or metamorphosed) by heat and/or pressure to form rocks such as slate, hornfels, etc. the resulting fine-grained metamorphic rocks tend to be referred to as Pelites.

Notes

^[1] The ironstone miners of Cleveland had their own terminology for many kinds of rock and tended to refer to mudstone units inter-bedded with ironstone seams as shale.

^[2] If the anecdote concerning this discovery is to be believed, although C.D Walcott recovered the fossils from this lagerstatten, it was actually his horse which drew his attention to their presence.

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