Volume VI | Chapter 3 | Regional GeologyNext Back to catalogue index
by John R. Senior

As noted in Chapter 2, the area covered by this volume presents a continuum with that described in Lang (1991), and includes a large section of the traditional North Riding of Yorkshire, bounded by the river Tees in the north, the Yorkshire coast to the east, the high Central Pennine hills to the west and a rather ill defined southern margin based on the City of York (see Fig. 2).

This swathe of northern English topography includes the Carboniferous hills and dales of the east Central Pennines in the west and the central glaciated lowlands of the Vale of York and the lower Tees Basin. To the east of the area, parts of the Yorkshire Jurassic Basin dominate the topography in the form of the Cleveland Hills in the north and the North York Moors further south, which are separated from the less prominent topographical feature of the Howardian Hills by the Vale of Pickering fault graben structure.

The Lower to Upper Carboniferous strata of the Central Pennines dip gently eastwards, disappearing under the more recent (geologically speaking) sediments in the Vale of York. Carboniferous strata form the basement rocks, at depth, under the whole area of study. The differences between the hardness of the strata and the cyclicity of the depositional regime are the keys to the explanation of local topography in the Central Pennines (the Yoredale Cyclothems were first described by John Phillips in Wensleydale in 1836). The repetitive cycles of deposition in the Lower to Upper Carboniferous of northern Yorkshire result in the characteristic stepped profiles of the hills and valley sides of the central Yorkshire Dales, where more durable limestones and sandstones form steep, often cliff edged, broad natural benches on the hillsides, and the intercalating softer shales produce poorly drained, steep, slightly concave slopes. Also characteristic of this part of the Pennines are the flat topped hills (e.g. Penhill, Addleborough, Wetherfell), visible up to 40 miles (65km) away, and which are capped by coarse, durable Namurian Millstone Grit.

At the western margin of the Vale of York, desert influenced sediments of Permo Triassic Age unconformably overlap the Carboniferous strata. Of the Permo Triassic sediments, only the basal Zechstein limestones (the Magnesian Limestones) are durable enough to create a modest topographical feature, a low series of hills (often masked by more recent glacial deposits) from the Harrogate area to County Durham. However these dolomitic limestones are greatly attenuated over the west–east trending structural feature, the Cleveland High, to the north west of Leeming. The Upper Permian and Triassic saliferous marls and soft sandstones are more easily eroded. During the last, Devensian, glaciation of this region (25,000–18,000 BP), the southerly advance of the pack ice (from local, Scottish, Lake District and Scandinavian origins) exploited these soft Permo Triassic sediments, gouging them away and on the retreat of the glaciers (c. 14,000–10,000 BP), replacing the surface topography with an undulating, poorly drained landscape complex comprised of tillite glacial deposits, sands and gravels, low morainic hills and a very disturbed surface drainage pattern. Little Upper Permian and Triassic strata are exposed in the Vale of York and Cleveland Basin area.

To the east of the study area the harder strata of the Cleveland Hills, North York Moors and the Howardian Hills resisted the progress of the Devensian ice advance and so have remained dominant topographical features in the northern Yorkshire landscape, resulting in physical barriers that must have influenced human access, at least until comparatively recent times. These Jurassic sediments of the eastern hill masses include the soft Liassic clays and shales which form part of the lowland plains that skirt the steep inland escarpment features (e.g. Cleveland Hills Old Norse clifa-land, 'district of cliffs': Smith 1928, 129), the flat-topped moors (which dip gently southwards) and the coastal cliffs. These sharply defined topographical features are capped by harder Middle Jurassic deltaic sandstones in the north of this area and by Upper Jurassic oolitic limestones on the Hambleton and Tabular Hills to the south (Senior 1991; id. 1999).

The last, Devensian, glaciation affected large areas of the northern landscape. The thick ice fields which, at their optimum, occupied the whole of the Vale of York (as far south as Sheffield) and the North Sea Basin (as far distant as Lincolnshire) trapped large temporary bodies of melt water at the edge of the Cleveland Hills, the North York Moors, the Hambleton and Howardian Hills (also the eastern part of the Central Pennines). The escaping, highly erosive waters from these extra glacial lakes (Kendall 1902; Gregory 1962) created a series of high level channels and over deepened river valley systems on all the peripheral flanks of these Yorkshire hill masses. This resulted in the current highly complex landscape profile, marginal to all the hill masses, when ice retreat eventually took place (c. 14,000–10,000 BP). During the Devensian glaciation, the ice dammed Vale of Pickering became a large and important lake area (Lake Pickering, of Kendall 1902), in which varved brick clays were deposited on Upper Jurassic sediments, chiefly Kimmeridge Clay. When the ice retreated, Lake Pickering largely emptied, leaving an afforested landscape environment of small lakes and marshland, which presented a considerable barrier to north–south communications until serious civil engineering (second-century road building by the Romans and thirteenth- to fourteenth-century drainage canal digging by the Cistercian communities) effectively started to change the situation.

STONE TYPES USED FOR THE SCULPTURES

A table indicating the geological origins of the stone types used for the sculptures in the area described in this volume can be found in the Figures. In comparison with the previous volume (Lang 1991) the variety of stone types used for the northern Yorkshire pre Conquest sculpture is far more limited; this is a reflection of the more localised availability of suitable quality stone and the large central tract of the Vale of York, which is largely glacial tillite covered and almost completely devoid of building and artefact stone.

CARBONIFEROUS SOURCES

Lower Carboniferous Sandstones (Brigantian Group)

Distinctive fine- to medium-grained beds of sandstone that overlay the Undersett Limestone (part of the Undersett Limestone Cyclothem) have been used extensively in the Stanwick area, abutting the northern boundary of north Yorkshire at the river Tees (e.g. Gilling West, Melsonby, Forcett and Stanwick). This stone type has been extensively quarried on the ridge escarpment occupied by the A66 (west of Scotch Corner, the route of Roman road 82: Margary 1967, 433–6), also on the gentle dip slope to the north and used traditionally for vernacular houses, farms and boundary walling in the area. Stone currently (spring 2001) being quarried for building stone at Gatherley Moor (NZ 193,068) is of the same type and quality used in most of the Stanwick group of sculptures.

Local sandstones from similar Lower Carboniferous horizons have been used in sculpture manufacture at the Barningham, Wycliffe, Cotherstone, Startforth, Rey Cross and Croft-on-Tees sites.

Upper Carboniferous

Millstone Grit Formation

These medium to very coarse grained, feldspathic sandstones (often with substantial quantities of larger quartzite pebbles, even pebble beds) were favoured by Roman builders and sculptors because of their resistance to weathering. Also being very porous, Millstone Grit rock dries out very rapidly, resulting in its use as damp-proofing ashlar courses in Roman York and other settlements of the north Roman frontier province.

The use of Millstone Grit declined after the Roman withdrawal in c. AD 410, but still this coarse sandstone continued to be used in a more domestic context (e.g. the manufacture of quern cereal grinding equipment and later millstones).

The sources of Millstone Grit stone used in manufacture of the sculptures is more problematical. Those sculptures found close to major Roman sites (such as York and Aldborough) were probably recut using stone robbed from the original Roman settlements. This stone was probably obtained from various West Riding sources indicated in Senior (1991): the East Carlton Grit at Hetchell Crag, near Thorner and East Carlton, but also the quarries in the Upper Plompton Grit along the river Nidd in the vicinity of Knaresborough (SE 346,567 358,556 and SE 355,537).

However, new Millstone Grit was probably being also quarried from the above quarries (this will be a subject discussed in the future West Riding Corpus volume) and also in the more northern Yorkshire Dales. The consistent use of Millstone Grit in the Wensleydale group of sculpture sites (Bedale, Middleham, Coverham, Wensley, West Witton, Castle Bolton, Patrick Brompton and Finghall), probably indicates the active quarrying of the Red Scar Grit which caps the hill masses to the west. This same stone was also extensively exploited later in the twelfth and thirteenth centuries to construct the abbeys at Jervaulx (Senior 1989) and Coverham, thus indicating a continuity of use.

Similarly Millstone Grit was used for sculptures at Masham, Wath and West Tanfield. Again the source of the rock was probably the local Pennine Hills to the west of these settlements where the Brimham and Plompton Grits are exposed.

In addition good quality fine- to medium-grained Namurian sandstones (probably locally quarried) have been utilised in sculpture manufacture in middle Wensleydale (Spennithorne, Coverham, Hauxwell and Thornton Steward).

Coal Measure sandstones, Westphalian

A few sculptures have been encountered (e.g. Kirklevington 2, Northallerton 1 and 5) which have been manufactured from good quality, fine grained Coal Measure sandstone. As there is no Westphalian (Upper Carboniferous) strata exposed in the survey area, the source of the sculpture stone must be out of the county. This then raises questions of the original stone source, its transportation and distribution (see below).

UPPER PERMIAN

Magnesian Limestone, Cadeby Formation

Sculptures carved in dolomitic limestone from the Cadeby Formation, Upper Permian were only recorded from a few sites (Wycliffe, Well, Croft and Newburgh Priory), unlike the situation described in Lang (1991) where the use of Magnesian Limestone was recognised in major sculptural pieces and these were extensively distributed throughout eastern Yorkshire.

In the case of Well, the poorly preserved piece was cut in locally quarried stone. Well was originally a Roman settlement located on the spring line at junction between dip slope of the Magnesian Limestone (Cadeby formation) uplands in the west, and lowland glacial deposits of the Vale of York.

TRIASSIC

Sherwood Sandstone Formation

Straddling the Permian–Triassic boundary are the reddish sediments of the Sherwood Sandstone Formation. These desert sediments include siltstones as well as poorly sorted fluviatile sandstones and some dunal components. These soft, poor quality sandstones have been used sparingly as a local source of building stone and apparently very rarely for sculptural stone. The use in sculpture manufacture at Croft may be a reflection of local availability of the stone, and the rarity in its use as such may be the consequence of its poor quality and having little resistance to normal weathering processes (i.e. many other sculptures may have been destroyed by weathering in the intervening centuries).

JURASSIC SOURCES

The local availability of excellent quality Middle and Upper Jurassic stone in the eastern part of the study area results in these having been often the preferred sources of stone in the manufacture of sculptures. The sediments of the Lower Jurassic in this Corpus area are too soft to have been considered for building or sculpture purposes.

Saltwick Formation, Aalenian, Middle Jurassic

Middle Jurassic deltaic strata are well exposed on the peripheral slopes of the North York Moors. They also cap large sections of the Cleveland and Eston Hills and are found in small, but important areas of the Howardian Hills and the Harlsey–Borrowby ridge. They are also well exposed in, and have been exploited extensively for building stone on, the sides of the deeply incised north–south river valley systems of the Seph (Senior 1990; 1999), Dove and Seven which drain the southward dipping hills of the North York Moors. These deltaic sequences accumulated as river-deposited parallic deposits within the Yorkshire Jurassic basin and consist mainly of siltstones, shales, and thin, flaggy sandstones, cut by contemporary river channel systems (Hemingway and Knox 1973). Redundant river channels became filled with clean, well sorted, cross-bedded sandstone bodies, the sources of excellent architectural and artefact stone. These have been exploited from the Iron Age period to the present day. Being elongate and meandering river-like in plan and lenticular in cross section, these sandstones bodies rarely lend themselves to modern extensive quarrying exploitation, but were ideal sources of good quality stone for the relatively small-scale Anglo-Scandinavian and medieval usage (Senior 1990; 1991).

Individual channels provide stone of differing qualities and colour variation (from white, through shades of yellow, pale brown and brown, to reddish brown) in accordance with the increasing limonite (ferric hydroxide) content.

The quarries at Aislaby, near Whitby (NZ 850,087), seem to have provided large quantities of stone for the pre-Conquest and post-Conquest monastic communities at Whitby. These extensive quarries, which are still visible, have white to pale yellowish sandstone at the base and rich reddish-brown ferruginous sandstones at the top of the quarry areas. Both types of stone from the Aislaby quarry source are commonly represented in the large numbers of surviving pre-Conquest sculpture fragments from the Whitby Abbey site and Lythe church, but in addition sculptural pieces have been exported far and wide throughout Yorkshire (Senior 1991, 14). Is this widespread distribution of religious sculpture a reflection of the importance of the Whitby community?

There are also a large number of locations around the area of the Cleveland Hills, parts of the North York Moors (particularly the scarp slopes and interior valleys), the Eston Hills, parts of the Howardian Hills and the top of the Harlsey–Borrowby ridge where good quality channel sandstones have been quarried, principally as ashlar masonry for churches and vernacular buildings, but also for sculpture manufacture. Unfortunately it is currently difficult, using geology alone, to accurately match stone used in sculptures with the probable source. However, consideration of the stone type with the rather tenuous knowledge of the contemporary communications patterns allows some source links to be made. Future advances in trace element analysis may shed more accurate geological light on this interesting problem.

Middle Calcareous Grit Member, Coralline Oolite Formation, Middle Oxfordian, Upper Jurassic

As indicated in Senior (1991) sculptures were manufactured in distinctive Middle Calcareous Grit (a good quality, durable calcareous sandstone) in the near vicinity to the Stonegrave Minster site and distributed in the Vale of Pickering area. In the present survey similar stone was used for sculptures at Crayke and Birdforth Hall.

DISTRIBUTION OF SCULPTURE IN NORTHERN YORKSHIRE

The distribution of pre-Conquest sculpture in northern Yorkshire is the consequence of a number of disparate factors. Some of these factors are obvious (such as availability of suitable stone), others can be inferred with various degrees of certainty (for example the use of pre-Roman tracks or Roman communications), and finally a number, such as patronage, which are currently difficult to address.

THE CONSEQUENCES OF GEOLOGICAL CONSTAINTS

As indicated above, it is generally the case that the stone used for sculpture was sourced in the higher areas of northern Yorkshire. Harder, more durable stone is more readily available in the Cleveland Hills, North York Moors and Howardian Hills in the east and the Pennine Hills in the west.

The lowland areas of northern Yorkshire are essentially devoid of stone suitable for sculpture manufacture, and the distribution of artefacts to these areas required transportation from the source quarries and sculpture workshops. It is currently recognised that the dressing and transport of stone (still a relatively inexpensive commodity) from the sources to the end-use point was the most costly item in stone processing and use. Certainly this seemed to be the case in medieval building (Salzman 1952, 119–38), and there can be little doubt that these cost factors also applied in eighth- to tenth-century England. Therefore it can be generally assumed that:-

(a) When stone is destined for very local use, then the sculpture workshop would be set up in or very close to the production quarries ('quarries' in a loose way could include pre-existing structures, i.e. Roman buildings being dismantled). In this scenario the Master Sculptor would travel to the site to set up a sculpture school.

Recognition of the work of a Master Sculptor or sculpture school (style and method of stone carving, subjects being executed etc.) is therefore important in understanding part of the environment of pre-Conquest sculpture use and manufacture (Lang 1991, 38–42).

(b) Where sculptures have been manufactured in stone recognised as being from a relatively distant source, then the sculpture would be completed at the stone source and transported as a finished article. The craftsmanship represents the added value to what is a relatively low cost block of raw material.

The transport of finished articles over a long distance represent a major investment in time and energy. These more distantly distributed sculptured pieces may have more significance than would at first be realised and may represent the effect of patronage.

TOPOGRAPHIC CONSTRAINTS

The topographically high areas of the Pennine Hills to the west of the region and the Cleveland Hills / North York Moors in the east provided considerable physical barriers to the easy distribution of the finished sculptured pieces. Therefore it is not surprising that every opportunity was taken to select local stone sources (Fig. 7). Because of the higher and more difficult terrain, sculpture sites were concentrated in the lower valley corridors (i.e. the Pennine Dales) or the older settlements peripheral to the upland regions (i.e. the foot of the escarpment of the North York Moors and Cleveland Hills).

The lowland regions of northern Yorkshire must have presented other problems and of a different magnitude. These areas are largely devoid of quality stone suitable for sculptural work. Therefore it is more than likely that all the stone found in these areas had to be transported from source quarry to its usage site, and often the transportation distances were considerable.

As previously indicated, the lowland areas of northern Yorkshire were greatly modified during the late Quaternary period by the Devensian glaciation (c. 25,000–18,000 BP). The Vale of York and the contiguous Cleveland Basin were left as poorly drained undulating marshy terrains by the retreat of the Devensian ice sheet, and the Vale of Pickering remained as a marshy former lake site. Both lowland areas were re-occupied at the end of the period of glaciation (c. 14,000–10,000 BP) by re-routed, meandering and modified river patterns.

The dense forests which quickly re-colonised the marshy vales after the end of the Devensian glaciation were largely left intact until medieval times. However, the upland areas, which had been deforested from Mesolithic time (but particularly through the Bronze and Iron Age periods) were connected by important tracks (McDonnell 1963), which also crossed the lowlands (e.g. the regalis via).

Also, following the Roman occupation of Yorkshire (early AD 70s), a network of roads was constructed across the marshy lowlands, together with inland ports on the navigable rivers (i.e. York, Tadcaster, Malton) and settlements on important river crossings (i.e. Aldborough / Boroughbridge).

There is also ample evidence that by the eighth century the higher 'islands' of these marshy, lowland terrains (i.e. the Ness at Stonegrave) had already become important settlements and consequently often also sculpture sites.

TRANSPORTATION OF STONE SCULPTURES

The average weight of the stone types used in the northern Yorkshire area are as follows:-

Middle Jurassic Sandstone   188kg/m3 (127lb/ft3)
Magnesian Limestone   186kg/m3 (125lb/ft3)
Upper Carboniferous Sandstone   223kg/m3 (150lb/ft3)
Upper Carboniferous Millstone Grit   238kg/m

Because of transportion difficulties there is a general 'rule of thumb' that the larger the sculptured monolith the less overland distance it must have travelled. However, it is evident that even when the monument is large (i.e. the Masham column or the Easby cross), it may have been constructed from a series of prefabricated pieces.

The methodology of sculpture distribution is also another important piece of conjectural evidence that should be considered. Transportation would have been very hazardous if not dangerous, as land communications were difficult. For example, it was easier getting to and from Whitby by sea until the railway connection was built in the mid nineteenth century. Therefore stone sculptures would probably be exported from the quarry/sculptural workshop in a finished state (as high value objects), since transporting rough blocks of stone is wasteful in terms of time and effort.

Various methods of transport were available for the distribution of the sculptures. For local transport of the larger, heavier, monolith pieces (entire crosses, hogback grave-covers etc.), sleds would have been available using horse or human power. These horse-drawn iron-shod sleds were commonly used in northern England even to the end of the nineteenth century for transporting stone/wood/feed over the frozen fellside in winter, or corn/hay/wool bales over the sun-baked ground in summer.

Another common mode of land transport in early medieval Britain was the pack horse. Hardy fell ponies can carry loads in excess of 99kg (220lb) for considerable distances, over moderate terrain with reasonable tracks (i.e. Roman roads, pannier tracks), slowly and when shod (Carla Weston, pers. comm.). This means, for example, that the sections of the Easby cross may have been transported in this way from the Aislaby Quarries near Whitby, along with other sculptural pieces.

River transport, where possible, would have been the most efficient mode of transport. Studies on the excavated tenth-century Graveney boat (Fenwick 1978, 173) indicate that the vessel had a carrying capacity of over 7 tonnes and a draught of only 0.65 metres. Other contemporary boats also referred to by Fenwick (1978, 254) suggest that with a lesser carrying capacity the boat draught could be reduced to 0.5 metres.

With boats of this carrying capacity and draught, even the upper reaches of the river Ouse system in Yorkshire would have been accessible to stone, particularly that 'quarried' from Roman York.

However, the writer's recent experience of river travel in Sarawak suggest that large stretches of the Yorkshire river system (the Tees, Swale, Ure, Nidd and Derwent) may have been accessible in flat-bottomed canoes or rafts. The 10-metre long Sarawak canoes have a cargo-carrying capacity of c. 200kg (440lb) minimal draught, and are easy to handle (by experts) in difficult, boulder-choked rivers.

PATRONAGE

Although, as previously stated, patronage is difficult to infer from eighth- to tenth-century monument distribution, there can be little doubt that certain sites did exert considerable influence on the sculptural heritage in Yorkshire. The master craftsmen and sculptural workshops of York (and other important sites) certainly exported finished, well-designed and executed pieces to many parts of Yorkshire (Lang 1991, 38–42). Likewise there is rock-type evidence that sculptures were exported from the Aislaby Quarries near Whitby (long associated with Hild's community at Whitby Abbey) to many areas of Yorkshire.

The expense of designing, carving and then transporting the sculpture pieces must have been the province of wealthy patrons, but the evidence for the connection between the current location of the sculptural fragments and the quarries/workshops of origin are very tenuous. One may take as an example the Easby cross. Cut in various sections of stone from one of the Aislaby Quarries, this well designed and executed important monument was then transported overland in sections from the remote east of the area to the valley of the river Swale. Who paid for this expensive monument, the design, the master craftsman, the transportation and why was the final site at Easby chosen?

Next Back to catalogue index

mouseover