Boulby – Cowbar Foreshore

This page still under construction.

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.

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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).

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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.

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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.

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Associated Sites

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

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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.

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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.

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.

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.

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.

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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

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Surveyors

Denis Goldring 2011

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©2011 Tees Valley RIGS Group.

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