Nunnington

[SE 646 785], [SE 648 787] and [SE 649 787]

J.K. Wright

Introduction

An abandoned railway cutting, Nunnington Railway Cutting, an adjacent overgrown quarry, Nunnington Railway Cutting Quarry, and Leysthorpe Quarry, a large quarry formerly worked by E.W. Creaser (Quarries) Limited of Pocklington, York, constitute a composite site west of Nunnington village and north-west of Stonegrave village (Figure 4.34). Leysthorpe Quarry lies beside the B1257 between Stonegrave and Leysthorpe. The Ordnance Survey spelling of the latter changed from 'Laysthorpe' to 'Leysthorpe' in the 1970s.

These exposures occur on the southern side of the Vale of Pickering adjacent to the E–W-trending Asenby–Coxwold Graben. The low ground occupied by this structure (Hovingham Carrs, (Figure 4.34)) separates the Corallian rocks of Caulldeys Bank, upon which the Nunnington site occurs, from the Howardian Hills to the south.

The railway cutting and adjacent quarry have been known to geologists for some time. The cutting was first described by Blake and Hudleston (1877), and by Fox-Strangways (1892). It was mentioned briefly by Arkell (1933, 1935–1948), and was visited by the Geologists' Association in 1933 and 1950 (Wilson, 1934, 1954). Wright (in litt, 1960) mapped the area and prepared detailed descriptions of the exposures. Wright (1972) described the Coral Rag in the cutting and adjacent quarry, and figured several ammonites collected from the Upper Calcareous Grit of Leysthorpe Quarry. The latter acquired importance as the stratotype locality of the Nunningtonense Subzone of the Upper Oxfordian Pumilus Zone (Sub-Boreal zonal scheme). Leysthorpe Quarry was referred to by Kent (1980b) as 'a quarry at Nunnington'. Wright (1996a, b) figured numerous ammonites from the two quarries, and gave a detailed measured section of the Upper Calcareous Grit at Leysthorpe Quarry.

Description

Measured sections at the three exposures: Nunnington Railway Cutting, Nunnington Railway Cutting Quarry and Leysthorpe Quarry are given below. These are updated versions of measured sections originally prepared by the present author in 1960.

Nunnington Railway Cutting section

Blake and Hudleston (1877) record Gervillella aviculoides (J. Sowerby), Cerithium muricatum (J. Sowerby) and 'Trigonia' sp. from Bed 4.

Nunnington Railway Cutting Quarry section

Blake and Hudleston (1877) record Hemicidaris sp., Natica clio, Nerinea sp., Chemnitzia sp. and Nanogyra nana (J. Sowerby) from Bed 2.

Leysthorpe Quarry section

A log of the Coralline Oolite Formation in Leysthorpe Quarry is given in (Figure 4.35).

The shelly oomicrites and oosparites of Beds 1–4 in the quarry mark a distinctive series of limestone beds that can be traced along Caulkleys Bank and pass into a coral bed and a shell bed at Ness (Wright, 1972). The upper Malton Oolite in the quarry is a very poorly sorted, pasty oolite (bed 5), with very few fossils preserved. The sequence of limestone beds at Leysthorpe Quarry is illustrated in (Figure 4.36).

The Coral Rag has an extremely prolific fauna. In all three exposures it divides into a coralliferous shell bed below, overlain by a fossilized coral reef with corals in growth position. The shell bed has yielded bivalves, gastropods and echinoids, spines of Paracidaris florigemma being abundant. The upper massive, micritic limestone is well exposed both at the Railway Cutting Quarry and in the railway cutting. It is noteworthy for the variety of corals present. Isastraea explanata occurs sparingly, and only one specimen of Montlivaltia dispar has been recorded. The tiny branching coral Rhabdophyllia phillipsi is more common, but the most abundant phaceloid coral is Thecosmilia annularis, with several arborescent colonies weathering out in Nunnington Railway Cutting and the Railway Cutting Quarry. Thamnasteria concinna is ubiquitous, layer upon layer of this massive coral encrusting bivalves and gastropods into one solid mass. Of the bivalves, Chlamys is notably rare, its place being taken by abundant Ctenostreon proboscideum. The massive corals are riddled with Gastrochaenolites borings containing Lithophaga inclusa, and many specimens can be found with the bivalve nestling in its hole. Gastropods and echinoid spines abound in the micritic matrix in between the corals, spines of Paracidaris florigemma being much more numerous than those of Cidaris smithi. The thickness of the Coral Rag varies considerably, increasing from 2.5 to 3.5 m when traced southwards in a 50 m length of the railway cutting.

The chief interest of the Upper Calcareous Grit is its remarkable ammonite fauna ((Figure 4.5)A–C, G), the most diverse, abundant and best-preserved in this formation in Yorkshire.

Though often compressed, particularly in the Newbridge Member, the ammonites, both macroconchs and microconchs, are usually fully preserved complete with body chamber. Wright (1996a, b) has figured 35 specimens collected in the two quarries.

Interpretation

During deposition of the Malton Oolite, Leysthorpe Quarry seems to have been situated in a slightly sheltered or depressed area, possibly lagoonal, accumulating sediments deposited in lower energy conditions. The sandy oolites of Bed 1, with their appreciable pyrite content, thus seem to have been laid down in a poorly circulated, stagnant area separating clastic sedimentation to the west from pure carbonate sedimentation to the east. They mark the lateral transition from the Middle Calcareous Grit into Malton Oolite (Figure 4.4). These sandy carbonates are overlain by micrites laid down under quiet, fully marine conditions, and yielding a thin-shelled bivalve and gastropod fauna (Bed 2 and Bed 4), separated by a higher-energy incursion containing much broken shell debris (Bed 3). The higher ooidal beds (Bed 5) are remarkably ill-sorted at Leysthorpe Quarry, without cross-bedding, and thus show no sign of winnowing by currents. They were presumably dumped into deeper water immediately after being formed in tidal channels. These channels, with their cross-bedded oolite, can be seen only 1.5 km away to the east in Nunnington Quarry [SE 661 787] (Figure 4.34).

The Coral Rag has a profusion of Paracidaris florigemma and a large variety of corals preserved in shelly micrite. This is clearly the true Coral Rag, and not simply a coralliferous facies of the Malton Oolite as was the case at Betton Farm Quarry (this volume). Many of the corals, particularly the 1 m high arboresques of Thecosmilia, indicate slightly more sheltered conditions away from the reef-front, which was probably situated to the south (see site report for Wath Quarry, this volume). The development of the Coral Rag at this site is much thinner than is usual and it is absent altogether east of Leysthorpe, at Nunnington village and Ness (Wright, 1972). In contrast, in the West Newton Grange Borehole 1.5 km to the north-west [SE 628 802] (Wright, 1996a), it is 8.7 m thick, and this thickness seems typical throughout the western end of the Vale of Pickering, with the exception of the present area. In the borehole core, the junction of Upper Calcareous Grit on Coral Rag was clearly bored and erosive, and it would appear that the thinning in the area of the Nunnington site, and absence at Nunnington village and Ness, is due to erosion beneath the Upper Calcareous Grit. A substantial gap between the two is indicated in (Figure 4.4), which also shows the limited area where the Newbridge Member is preserved due to erosion beneath the Spaunton Sandstone.

The Upper Calcareous Grit is present in a markedly atypical facies towards the base, and the laminated spiculites (Bed 7 in the Railway Cutting Quarry and Bed 9 and Bed 10 in Leysthorpe Quarry) are only tentatively correlated with the Newbridge Member. In the West Newton Grange Borehole, the normal, argillaceous facies of the Newbridge Member is present (Wright, 1996a). These laminated, clayey silts appear to pass into the laminated spiculites. Shallow, quiet, slow conditions of sedimentation are implied, without the influx of mud that characterizes the Newbridge Member at other localities. In the east, around Nunnington village and Ness, where flaggy sandstone (?Spaunton Sandstone) overlies Malton Oolite (Wright, 1996b), the Newbridge Member appear to have been overstepped (Figure 4.4). This is probably the case also in the railway cutting section. The upper members of the Upper Calcareous Grit, the Spaunton and Snape sandstones, were instantly recognizable in the borehole core, and comparison of these thicknesses with those measured in the Nunnington Railway Cutting suggests that the Snape Sandstone comes above the highest beds seen in the cutting.

The Upper Calcareous Grit at Leysthorpe Quarry, and to a lesser extent at Nunnington Railway Cutting Quarry, has yielded an Amoeboceras fauna that fills a significant gap in British Oxfordian stratigraphy (Wright, 1972). With its coarsely ribbed A. transitorium and A. glosense ((Figure 4.5)B, C), and its finer-ribbed A. ilovaiskii, A. newtonense and A. nunningtonense ((Figure 4.5)A) this fauna is older than the Glosense Subzone Amoeboceras fauna of the Clavellata Formation of Dorset (Figure 2.11)B, E. It is therefore also older than the equivalent Bed 4 Amoeboceras fauna of Newbridge Quarry (Figure 4.5)D, E. It rests on the Coral Rag, whose ammonite fauna both in Yorkshire and around Oxford is that of the Sub-Boreal Parandieri Subzone of Callomon (1960) (Figure 1.4). The Amoeboceras and associated peri-sphinctid fauna of Bed 9 and Bed 10 thus became the type fauna of the Sub-Boreal Nunningtonense Subzone of the full Pumilus Zone (Wright, 1972), and it also typifies the Boreal Ilovaiskii Subzone of the Glosense Zone (Sykes and Callomon, 1979).

Perisphinctes is remarkably common in Bed 9 and Bed 10 at Leysthorpe Quarry ((Figure 4.5)G, H). This section is therefore the only exposure in England where the Amoeboceras of the Ilovaiskii Subzone (Sykes and Callomon, 1979) and the Amoeboceras, Perisphinctes and Deci pia of the equivalent Nunningtonense Subzone (Wright, 1972) can be collected from a permanent exposure. All other Yorkshire exposures of Upper Calcareous Grit, with the possible exception of Ravenswyke Quarry, Kirkby Moorside (Wright, 1996a), yield faunas predominantly of Glosense Subzone age. The highest beds at Leysthorpe Quarry (beds 11–13) may belong to this subzone.

Conclusions

Nunnington Railway Cutting and the neighbouring Nunnington Railway Cutting Quarry and Leysthorpe Quarry provide a fine composite section through the Malton Oolite and Coral Rag Members of the Coralline Oolite Formation. The shelly facies of the Malton Oolite forms a significant marker band that can be traced throughout the Caulkleys Bank area. The Coral Rag shows lateral thickness and facies changes together with a rich and diverse reef-forming and reef-dwelling invertebrate assemblage.

The Upper Calcareous Grit has yielded important holotype ammonites defining a new Sub-Boreal subzone (Nunningtonense Subzone). This allows correlation with areas containing similar ammonites in the Sub-Mediterranean Province in southern Europe and Poland. The presence in addition of ammonites typifying the Boreal Ilovaiskii Subzone allows correlation with areas in the Boreal Realm such as Skye and Greenland. Nunnington is thus a key stratigraphical locality for both the wide variety of lithologies and fossil groups present here, and its bearing on intercontinental correlations.

References