england fossils palaeontology

Salthill Quarry, Clitheroe: A resource degraded

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Stephen K Donovan (The Netherlands)

The Mississippian (Lower Carboniferous) is often referred to as the ‘Age of Crinoids’. Historically, the best collecting area for fossil crinoids in the Carboniferous Limestone of the British Isles has been Clitheroe, in Lancashire. The late Stanley Westhead, who lived in Clitheroe, rightly claimed that:

… nowhere else in England have Carboniferous crinoids been found in such large numbers and also in such variety of genera and species” (Westhead, 1979, p. 465).

Indeed, it is probably the best area to collect fossil crinoids of any age in England. Although there may be more species known from the Silurian (Wenlock) of the Dudley area in the West Midlands, since the quarries there ceased operation in the 1920s, crinoid crowns have been difficult to find. In contrast, I have just spent an enjoyable week in August 2010 collecting thecae and other crinoid fragments at Clitheroe.

There are three notable crinoid localities in the Clitheroe area, namely Bellmanpark, Coplow and Salthill quarries (Wright, 1950-1960; Donovan, 1992a). Bellmanpark (currently active) and Coplow (disused) quarries are not accessible to the public. Salthill Quarry (Grayson, 1981; Bowden et al., 1997) is a nature reserve managed by the Wildlife Trust for Lancashire, Manchester and North Merseyside. It exists around an industrial estate and is freely accessible.

Fig. 1. The crinoid bank (locality 6 of Bowden et al., 1997) as it is today, largely obscured by grass. Collectors (left and middle) approximately define the exposure of bedded limestone, which extends a little way past the bush in the centre. The best collecting is along this line and lower, where crinoid debris accumulates as a fossil-enriched gravel.

Of particular interest is locality 6 of Bowden et al. (1997), which has been an excellent site for collecting crinoid thecae. (The word “thecae” refers to the skeleton and free arms of the crinoid.) A number of guides exist to the crinoids and other echinoderms of this quarry, to which the reader is referred (Donovan, 1992a; Donovan et al., 2003; Donovan & Lewis, in press). Articulated brachiopods, solitary rugose corals and rare blastoids are other elements of the macrofauna here. Bulk sampling of the fossil gravel, which accumulates at the bottom of the slope (Figs. 1 and 2), may reveal other taxa that are not obvious in the field, such as the spines and test plates of echinoids.

Fig. 2. Collecting at Salthill Quarry. As it is a nature reserve, hammering limestones is discouraged. However, there is abundant crinoid debris to collect from the surface gravel of fossils washed out of shales, with rarer articulated brachiopods, and tabulate and solitary rugose corals.

Locality 6 was scraped over and exposed in the early 1960s when this area of Salthill was being evaluated for quarrying, which, ultimately, never happened. However, what this process did do was expose a highly fossiliferous succession for collectors. Stanley Westhead was there to sample this succession when it was first exposed and his fine collection is now safely housed in The Natural History Museum, in London. I first collected at this locality in the early 1980s.

Twenty years after it was exposed, it was still a delightful collecting site, yielding camerate crinoid thecae of the size and appearance of golf balls. (The name “camerate” comes from the chamber that a tube – the tegmen – forms above the cup in these species.) Crinoid roots, distinctive columns of genera not known from this site as thecae (such as Barycrinus sp; Donovan & Veltkamp, 1990), borings in crinoid columns and cups (Donovan, 1992b), and distinctive new species were there to be collected (Donovan & Westhead, 1987).

Fig. 3. The attractive crinoid seat at the top of the bank. Good to look at, but a little lumpy to sit on. The carvings of crinoids are anatomically inaccurate, but still pleasing to the eye and only a crinoid expert would notice the errors.

My first trip to locality 6 at Salthill Quarry in over 20 years engendered mixed feelings. It was good to be back. The scraped slope was still there (Fig. 1), although grass is more prevalent than before. A fine bench now sits at the top of the slope with unusual crinoid artwork (Fig. 3), attractive, but unfortunately not anatomically strictly accurate. In addition, the crinoids are still there (Figs. 2 and 4), although thecae are not as abundant, and those that were found by me and others were generally small, with larger specimens being incomplete. Yet, it still represents an important crinoid site. I have added some fine specimens to my research collection of crinoid columns with prominent boreholes. Having first seen such specimens almost 30 years ago, it is high time for me to study them seriously.

Fig. 4. An exposed bed of limestone, rich in crinoid pluricolumnals, which appear dark. The surface has been washed with water to enhance contrast.

The nature reserve at Salthill Quarry does not just cater for the geologically inclined. I enjoyed the wildflowers, the butterflies and, when not disturbed by the noise from the industrial estate, the general peace that made collecting so enjoyable. However, the requirements of a geological reserve are different from those for living organisms. Plants and animals grow and reproduce, but geology deteriorates if it is not refreshed. I wonder if now, almost 50 years after it first happened, it isn’t time to scrape the surface at locality 6 once again. This would cause little disturbance to the rest of the reserve, yet would revitalise a scientifically important site, perhaps for another 50 years.

My thanks go to NCB Naturalis, Leiden, for the financial support, which made my recent visit to Salthill Quarry possible.

Update

An update to this article can be found at: Salthill Quarry, Clitheroe: A resource revitalised.

References

Bowden, A., Webster, M. & Mitcham, T. 1997. Salthill Quarry geology trail. Geologists’ Association Guide, 58, 30 pp.

Donovan, S. K. 1992a. A field guide to the fossil echinoderms of Coplow, Bellman and Salthill Quarries, Clitheroe, Lancashire. North West Geologist, 2: 33‑54.

Donovan, S.K. 1992b. Site selectivity of a Lower Carboniferous boring organism infesting a crinoid. Geological Journal, 26: 1‑5.

Donovan, S.K. & Lewis, D.N. (in press). Fossil echinoderms from the Mississippian (Lower Carboniferous) of the Clitheroe district. In Kabrna, P.N. (ed.), Carboniferous Geology: Bowland Fells to Pendle Hill. Craven & Pendle Geological Society, UK.

Donovan, S. K., Lewis, D. N. & Crabb, P. 2003. Lower Carboniferous echinoderms of northwest England. Palaeontological Association Fold-Out Fossils, 1: 12 pp.

Donovan, S. K. & Veltkamp, C. J. 1990. Barycrinus (Crinoidea) from the Lower Carboniferous of England. Journal of Paleontology, 64: 988‑992.

Donovan, S. K. & Westhead, S. 1987. Platycrinites contractus (Gilbertson) and a new Platycrinites from the Lower Carboniferous of northern England. Proceedings of the Geologists’ Association, 98, 211‑215.

Grayson, R. 1981. Salthill Quarry Geological Trail. Nature Conservancy Council, London, 26 pp.

Westhead, S. 1979. Carboniferous crinoids from the Clitheroe area. Proceedings of the North-East Lancashire Group of the Geologists’ Association, 2, 465-496.

Wright, J. 1950-1960. A monograph of the British Carboniferous Crinoidea. Monograph of the Palaeontographical Society, 1, pt. 1, pp. i-xxx+1‑24 [1950]; pt. 2, pp. 25‑46 [1951]; pt. 3, pp. 47‑102 [1951]; pt. 4, pp. 103-148 [1952]; pt. 5, pp. 149-190 [1954]: 2, pt. 1, pp. 191-254 [1955]; pt. 2, pp. 255-272 [1955]; pt. 3, pp. 273-306 [1956]; pt. 4, pp. 307-328 [1958]; pt. 5, pp. 329-347 [1960].

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