INTRODUCTION
Excavations of urban and rural sites across Britain dating to the Roman occupation (a.d. 43–410) have revealed many mosaics of high quality and some whose workmanship is exceptional, as a recently-completed corpus of all known mosaics from Britain illustrates.Footnote 1 The wealth of abstract pattern and figurative detail contained in these mosaics has excited considerable discussion about their artistic composition and iconographic interpretationFootnote 2 and also speculation as to the existence of fourth-century groups of mosaicists based on the identification of regional shared stylistic characteristics.Footnote 3 However, there are still many practical questions concerning the manufacture of the mosaics that remain unanswered. In particular, we have little knowledge about the way in which tesserae were sourced and transported. This study investigates the provenance of chalk tesserae from Leicester (Ratae Corieltavorum).
There were sound reasons for choosing to study material from Leicester. Firstly, the town occupied a central position in the Roman province of Britannia ( fig. 1a). This was pivotal not only in terms of location, but also in economic and developmental terms, since the town lay (as it were) in the mid-lands between the ‘militarised north’ and the ‘civilised south’. This made the possibility of contributing to the post-excavation analysis of the Vine Street excavations — which revealed the first complete plan of a town-house to be uncovered in Ratae — an interesting prospect. Secondly, there are no chalk outcrops within easy reach of the town, which means that any chalk artefacts recovered by excavation must have been transported. Ratae had good road and river communications with the rest of the province and it was thought that this would enable some light to be shed on the movement of mosaic materials. Thirdly, there was an availability of chalk tesserae from several different archaeological levels in the Vine Street Town-House. All these factors combined to make material from Leicester a suitable candidate for study.
Chalk has a distinctive microfossil signature which can be utilised to determine its biostratigraphical age and thus, in many cases, its source. Narrowing down the provenance of the chalk to particular areas enables conclusions to be drawn about the origin, transportation and distribution of the tesserae. Tesserae that can be traced to a particular level in an excavation are particularly useful in this respect, in that they are likely to be dated, at least approximately, by the wider archaeological context in which they were found. This information can then be used to determine whether the provenance of the raw material varied through time.
A pilot study demonstrating the validity of this ‘microfossil signature’ technique examined chalk tesserae from Insula IX, Silchester (Calleva Atrebatum).Footnote 4 The excavation furnished several mosaics dating from the first to the fourth centuries a.d. The chalk tesserae yielded an assemblage of microfossils dating to the Late Cretaceous. This eliminated local sources of chalk, which were older in date, and pointed instead to an origin in the chalk downlands of southern England, which suggested that the mosaicists working in Calleva had imported their tesserae from Dorset, a source of other lithologies used in the mosaics. More recently, microfossils have been used to show that local chalk was used in mosaics at Brading Roman Villa on the Isle of Wight.Footnote 5 Here microfossils are used to reconstruct the biostratigraphical age of chalk tesserae employed in Roman Leicester and to refer to the distribution of the Chalk Group in England to suggest likely areas of provenance for the tesserae.
METHODOLOGY
The need for more and better information on the geographical origin of mosaic materials has been acknowledged for some timeFootnote 6 and this has led to a growing recognition of the contribution that geology can bring to archaeology in the field of provenance studies. In recent years, the provenance of tesserae and sculptural material has been investigated using microfacies analysis,Footnote 7 petrological analysis,Footnote 8 a combined approach using petrological and geochemical analysis,Footnote 9 and microfossil analysis.Footnote 10
These approaches have contributed much to our understanding of the use of raw materials in the manufacture of tesserae. For example, boulders and pebbles of Mesozoic carbonates and sandstones found locally in Pleistocene and Holocene glacial sediments have been shown to be the source of raw material used to manufacture bichrome (black and white) mosaic tesserae from two villas close to Augsburg (Augusta Vindelicum) in Bavaria.Footnote 11 Similarly, an early third-century polychrome mosaic from Kraiburg in Bavaria was found to contain coloured tesserae cut from Jurassic and Cretaceous sedimentary deposits found in local Pleistocene fluvioglacial deposits.Footnote 12 In Britain, dolomitic cementstone and burned clay sourced from the Upper Jurassic Kimmeridge Clay Formation in Dorset contributed the raw material for a large number of tesserae from mosaics found at Silchester;Footnote 13 indeed, the use of these lithologies (and others from the same geographical area) in the manufacture of pottery, tesserae, shale goods and sculptural items found at sites across South-East England provides strong evidence for a geomaterials industry based in the Poole-Purbeck area of Dorset from the first century a.d. onwards.Footnote 14 Finally, geochemical and petrological analysis of materials used in the manufacture of late first-century to early second-century funerary sculpture and monumental architecture found in Roman Britain has also recorded the use of Caen limestone and similar freestones from the Jurassic, Upper Cretaceous and Tertiary periods imported from widely separate outcrops in northern and central France and also from the Rhineland.Footnote 15 This study focuses on the contribution to provenance studies that can be made using biostratigraphy based on microfossil analysis.
MICROFOSSILS AND PROVENANCE
The principle of biostratigraphy is not new. Similarities and differences in fossil fauna and flora have been used to characterise rock successions since the pioneering work of the engineer geologist William ‘Strata’ Smith in the early nineteenth century.Footnote 16 This powerful methodology has enabled the correlation and relative dating of rock successions throughout the Phanerozoic and provided a framework for the understanding of evolutionary lineages and global environmental change. Using the fossil content of rocks to characterise and so correlate particular strata is a technique widely used in geology.
Microfossils have proved themselves particularly useful in this respect. Their very small size (generally <1 mm) enables them to be recovered from small samples, a useful characteristic when dealing with tesserae, which are typically sized between 5 and 20 mm3. In general, the groups of organisms that are preserved as microfossils evolve rapidly, are geographically widespread, can be extremely abundant and are found in a wide variety of sedimentary rock types.Footnote 17 As a result, there is growing recognition of the research potential of microfossils to the study of inorganic archaeological materials.Footnote 18 The microfossils found in chalk rock units (principally ostracods, foraminifera and nannofossils) have been studied particularly closely because of their usefulness in correlating strata between regions, which is of interest to petroleum geologists concerned with the reservoir potential of chalk formations. Correlating strata across regions has also led to the concept of foraminiferal biozones: biostratigraphic intervals based on the presence of particular species or assemblages of foraminifera. These faunal differences can be used to provenance chalks and are the basis of the approach to provenance taken in this paper.
ROMAN LEICESTER AND THE VINE STREET TOWN-HOUSE
Leicester (Ratae Corieltavorum) is sited at a crossing point of the River Soar and this geographical advantage is likely to have contributed to its early development as an important Late Iron Age settlement: by the end of the first century b.c., the community was prosperous enough to be importing pottery from Gaul and the Mediterranean.Footnote 19 The settlement appears to have been a local centre for the Corieltavi, whose coins are found here, most recently amongst a series of hoards found in a shrine context some 15 km to the south-east at Hallaton.Footnote 20 It is possible that the strategic importance of the settlement and its river crossing point made Ratae an early military objective for the invading Roman army, as a small Roman fort appears to have been established on the west bank of the river to control the crossing,Footnote 21 and although it is not known whether the tribal groupings constituting the Corieltavi were amicable, ambivalent or antagonistic towards the Romans, there is a suggestion that the invading forces may not have been welcomed by all.Footnote 22 A gridded town plan ( fig. 1a) was laid out early in the second century a.d., probably coincident with the town becoming a civitas-capital, but the main phase of civic building did not occur until later: a stone forum and basilica were built under Hadrian (a.d. 117–38), the Jewry Wall public baths under Antoninus Pius (a.d. 138–61), and the market hall or macellum not until the late second century.Footnote 23 Mosaics dating from the second to the fourth century a.d., some of very high quality, have been recorded from Ratae, the greatest density being found in the west of the townFootnote 24 from houses overlooking the river. This may indicate that the western half of the civitas-capital was more prosperous than the east.Footnote 25
a. Plan of Roman Leicester (Ratae Corieltavorum) showing the location of the Vine Street Town-House in Insula V; b. Plan of the Vine Street Town-House, Leicester, in the third to mid-fourth centuries a.d., showing the location of Room 6. (With permission of University of Leicester Archaeological Services)
In 2004–6, the University of Leicester Archaeological Services (ULAS) carried out the largest excavation ever undertaken in Leicester as part of the new Highcross retail development.Footnote 26 The excavation took place in the vicinity of Vine Street and provided a rare opportunity to investigate in detail the building history of private domestic and commercial properties in one of the more peripheral insulae of the Roman town (Insula V). In all, ten Roman buildings situated in the north-east corner of the settlement and dating from the late first to the late fourth centuries a.d. were excavated. The excavations revealed a history of modest development during the first and second centuries a.d., followed by a period of active construction in the third and a degree of decline in the fourth. The second-century buildings found on the site were not without merit. Tesserae and decorated wall-plaster containing cinnabar that were found among debris associated with one of these buildings (Building D, later incorporated into the Town-House) imply that it had a superior status, and there is good evidence for suggesting that the central room of this building was the source of the second-century geometric mosaic found in 1839 and now housed in the Jewry Wall Museum in Leicester.Footnote 27
A major phase of renewed construction in Insula V at the beginning of the third century led to the above building and two others on the same site being remodelled into a single structure by the addition of a north range. The new north range was connected to the three existing buildings by a peristyle corridor that surrounded an internal courtyard and gave access to suites of rooms within the new complex. It was partially provided with a hypocaust system and contained a central apsidal room, suggestive of a formal reception room, which was set opposite a possible entrance-hall in the southern range across the courtyard. This third-century remodelling created a substantial courtyard-style town-house some 39 by 40 m square (the Vine Street Town-House). The Town-House occupied the whole south-west corner of the insula, providing it with two road frontages ( fig. 1b).
Apart from some modest improvements made in the early to mid-third century, the Town-House appears to have undergone no further major structural alterations. Successive resurfacing of floors throughout the building indicates that it was occupied continuously for around 150 years until its abandonment as a dwelling in the mid-fourth century. There is no evidence of sumptuous decoration, but some fragments of coarse mosaic flooring were found in situ in the peristyle corridor of the eastern range. These are contextually dated to the early fourth century a.d. Enough tessellation remains to show that the simple design consisted of red tile tesserae set into a background of blue-grey sandstone ones, either in multiple stripes or in a grid pattern. The red-on-blue grid pattern is similar to other geometric mosaics found in Leicester and dating to the same period, such as those found at the Norfolk Street (Cherry Orchard) villa, sited about 1 km outside the Roman town on the west bank of the river,Footnote 28 and there are similarities to other fourth-century mosaics found at Tixover and Thistleton Dyer in Rutland,Footnote 29 although in these villas the red grid is laid on a buff background. Sufficient quantities of residual blue-grey and red tesserae were also recovered from elsewhere at this level in Vine Street to suggest that the north range suite of rooms and its associated corridor may have been similarly tessellated, and a Small Find of intact mosaic consisting of several rows of smaller tesserae (SF 1084, discussed below) indicates that the building may have housed a finer quality mosaic in at least one room. Unfortunately, the north range appears to have been deliberately demolished in the mid-fourth century, thus removing any evidence for mosaics from the rooms most likely to have housed them, and the Town-House also appears to have been abandoned as a private dwelling around this time. There is evidence that some rooms continued to be used as workshops for a short time longer, but the building seems to have become derelict by the end of the fourth century.
THE VINE STREET TOWN-HOUSE TESSERAE
The tesserae examined in this study came from four levels of redeposited and unsorted material (Vine Street A, B, C and D) found in Room 6 in the far south-western corner of the Town-House (fig. 1b).Footnote 30 The Vine Street B tesserae had been re-used, along with ceramic tile and sandstone fragments, to provide the substrate for a new floor in Room 6 during a major phase of resurfacing in the early to mid-fourth century. The Vine Street A and C tesserae were taken from two piles of reclaimed building material which had been left in the northern end of Room 6, apparently as salvage, during the final usage of the building in the mid- to late fourth century. The Vine Street D tesserae were sampled from the fine mosaic (Small Find SF 1084) mentioned above. This had been picked off the floor of Room 6 and consisted of three rows of small white chalk tesserae and one row of small dark blue-grey limestone tesserae.
The Vine Street tesserae examined in this study were all taken from redeposited material, so although the time of their re-deposition relative to the age of the building may be inferred from the archaeological context, it is not possible to know with any certainty either when or where the mosaics from which they were salvaged were laid. However, it is possible to make some assumptions. The simple tessellated design of the surviving peristyle mosaic appeared to use only blue-grey and red tesserae, which suggests that the white chalk tesserae used for this study came from elsewhere in the Town-House. Also, the tesserae examined included finer material: some of the Vine Street A material was less than 4 mm2 in size, and the Vine Street C tesserae were all small (<10 mm2) and contained a number of thin triangular shapes, indicating that they had been used for more detailed tessellation. This suggests that the Vine Street A and C tesserae found in Room 6 may originally have been laid in one of the principal rooms in the north range and were salvaged for re-use when this was demolished in the mid-fourth century. If this is so, the mortared tesserae of the Vine Street D Small Find may be a fragment of a finer-quality mosaic originally laid in one of the formal rooms.
Unfortunately, it is not possible to ascertain from the archaeological evidence when any such finer-quality mosaics might have been laid. The north range was demolished in the mid-fourth century and post-Roman truncation has removed levels to below that of the Roman floors. However, the date can be modestly constrained by recognising that any mosaics laid at the time of the construction of the north range would date to the early third century, whilst any contemporaneous with the tessellation of the peristyle corridor would date to the early fourth. Arguments for the later date might include the reasonable assumption that the tessellation in the north range and its associated corridors was laid at the same time, and that the tesserae found in Room 6 had been carefully salvaged and collected; any mosaics in the north range laid in the early fourth century would not have been in place for longer than about 20 or 30 years before the range was demolished and the material might, therefore, have been thought particularly worth saving.
RECOVERING MICROFOSSILS FROM THE TESSERAE
Sample tesserae from three of the four levels of the Vine Street excavation (Vine Street A, B and C) were crushed and processed individually, using a variety of techniques. As the Vine Street A tesserae were relatively soft, two of them were simply crushed and examined unprocessed, but this technique was not successful in extracting microfossils and so the remaining tesserae from Vine Street A were processed by soaking them in white spirit for 30 minutes and then boiling them in sodium hexametaphosphate. In contrast, the Vine Street B and C tesserae, which were generally harder, were processed by a freeze-thaw method using sodium sulphate decahydrate (Glauber's Salt), since results from a trial of processing methods suggested that the freeze-thaw method was a more successful technique than the white spirit method for extracting microfossils from harder chalks.Footnote 31 In addition, polished thin sections were made from tesserae from all three levels. However, as consistently good microfossil identification results were obtained only from thin section analysis, this was the only method adopted for the Vine Street D mosaic fragment, six of whose tesserae (five of white chalk and one of blue limestone) were removed for this purpose. In total, 36 tesserae from Vine Street were examined, of which eleven yielded no microfossils and a twelfth (VS B05) was crushed sacrificially in order to demonstrate the strong smell of bitumen released on disintegration (Table 1).
NUMBER OF TESSERAE EXAMINED FROM EACH LOCATION IN THE VINE STREET TOWN-HOUSE, LEICESTER
The samples of loose tesserae varied considerably in size, as might be expected of reclaimed but unsorted material. The Vine Street A tesserae varied the most in size, the smallest triangular tesserae having sides less than 4 mm in length whilst the largest tessera was rectangular 25 by 30 mm. The Vine Street B tesserae were square, typically sized between 15 and 20 mm2, similar to those used for coarse tessellation. In contrast, the Vine Street C tesserae were all small (<10 mm2) and the sample contained a number of thin triangular shapes. The mortared Vine Street D tesserae were also small, typically between c. 10 and 13 mm2. The samples also varied in hardness, the Vine Street A tesserae being generally softer (easier to crush) than either the Vine Street B or C tesserae. The Vine Street B tesserae were grey, smelled strongly of bitumen when crushed and were splintery in texture when processed. They were classified as a calcareous mudstone and found to yield few microfossils.
BIOSTRATIGRAPHICAL ANALYSIS
The distribution of species of foraminifera within the Upper Cretaceous Chalk Group is well knownFootnote 32 and this knowledge has enabled a sequence of foraminiferal biozones to be developed by Wilkinson through the application of existing biostratigraphical schemes to high-resolution mapping carried out by the British Geological Survey (BGS).Footnote 33 Foraminifera recovered from the Vine Street tesserae were compared with this dataset. Details of the tesserae examined and the foraminifera identified appear in Tables 2–5. fig. 2 shows thin-section images of some of the key species identified. fig. 3 shows the lithostratigraphy and biostratigraphy for chalks of northern and southern England and the frequency and relative abundance of the algal sphere Pithonella sphaerica in chalks of southern England for the early Upper Cretaceous (Cenomanian and Turonian stages). The shaded area in fig. 3 represents the stratigraphic age range for the microfossils recovered from the Vine Street chalk tesserae, based on the known evolutionary ranges of the index species recovered from the samples. An analysis of the results for each of the levels appears below.
Thin section images of microfossils found in chalk tesserae from the Vine Street Town-House, Leicester. 2.1: Dicarinella hagni (MPK 14370: ex MPA 62491); 2.2: Pithonella sphaerica in flood proportions (MPK 14371: ex MPA 62494); 2.3: Marginotruncana marginata (MPK 14373: ex MPA 62492); 2.4: Dicarinella canaliculata (MPK 14372: ex MPA 62491). Note that the majority of specimens in image 2.2 are Pithonella sphaerica, but that P. ovalis also occurs in small numbers.
Upper Cretaceous (Cenomanian and Turonian) lithostratigraphy and biostratigraphy for chalks of northern (N) and southern (S) England. The frequency and abundance of pithonellid blooms for chalks of southern England are shown. The faunal biozones follow those of Wilkinson Reference Wilkinson2000. The shaded area represents the stratigraphic age range for the chalk tesserae from Vine Street.
MICROFOSSILS FOUND IN TESSERAE FROM THE VINE STREET TOWN-HOUSE EXCAVATION, LEICESTER (ALL TESSERAE WERE FOUND IN ROOM 6 OF BUILDING G OF THE VINE STREET TOWN-HOUSE, LEICESTER (SK 583 049)) VINE STREET A *thin sections VINE STREET B *thin sections VINE STREET C *thin section VINE STREET D * thin sections
VINE STREET A
All the planktonic foraminifera viewed or recovered from the Vine Street A tesserae were simple, non-keeled forms, mostly of Hedbergella (Table 2). The absence of keeled species suggests the fauna date to be the Cenomanian. This is supported by the common occurrence in thin section of the algal sphere Pithonella sphaerica, whose relative abundance in sediments increases noticeably during the Cenomanian to reach a maximum in the Late Cenomanian and Early Turonian (see fig. 3). However, although several samples of the Vine Street A material were highly fossiliferous, index species used in biostratigraphical zonation were not found in the tesserae examined.
VINE STREET B
The Vine Street B tesserae broke into hard and splintery grey fragments and released a strong smell of bitumen when crushed. The sample taken for thin-section analysis also released a similar smell of bitumen when cut. However, samples of the fragments reacted positively when tested with cold dilute hydrochloric acid. It would appear, therefore, that the Vine Street B tesserae had been cut from a calcareous mudstone rather than from a chalk. A very few indeterminate microfossils were recovered from the calcareous mudstone, but these could not be positively identified as foraminifera (Table 3). This sample was therefore not considered further.
VINE STREET C
One of the Vine Street C tesserae (C02) was a soft and creamy-white chalk from which foraminifera were recovered, although unfortunately these were poor in quality and none could be identified with certainty. A thin section cut from a second and harder chalk tessera (C07) also proved to be highly fossiliferous. The remaining five tesserae appeared chalky, but splintered into blue-grey fragments on processing, the chalky appearance being down to a surface covering of lime mortar masking a dark blue-grey limestone. No foraminifera were recovered from these five tesserae or their mortar. However, the similarity between the two rock types found in this sample (chalk and a blue-grey silty limestone) and those found in the mosaic fragment described below (Vine Street D) suggests that the Vine Street C tesserae might have been salvaged from the same mosaic as the Small Find 1084.
The microfossils identified from the Vine Street C thin section (Table 4) consisted of keeled and non-keeled planktonic foraminifera and the algal sphere Pithonella sphaerica. There were noticeably few benthonic foraminifera. The non-keeled planktonic foraminifera were represented by long-ranging species such as Hedbergella delrioensis, H. brittonensis and Heterohelix reussi. However, the keeled planktonic foraminifera identified from the thin section included the index species Dicarinella hagni, whose appearance is limited to BGS Foraminiferal Zones 6–9 (sensu Wilkinson Reference Wilkinson2000) which cover the period from the late Cenomanian to the early Turonian. The thin section also revealed most noticeably Pithonella sphaerica in large numbers. Such Pithonellid ‘blooms’ (sensu Wilkinson Reference Wilkinson2011b) are characteristic of several stages in the Late Cretaceous, of which the earliest is in the early Turonian.Footnote 34 The pithonellid and planktonic foraminiferal evidence would, therefore, suggest an early Turonian date for these tesserae. This is supported by evidence from the few benthonic foraminifera recovered, which include, as well as the long-ranging Lenticulina rotula, the occasional specimen of the benthonic foraminiferid Gavelinella cf berthelini, which is found particularly in the Cenomanian to Turonian.
VINE STREET D
Polished thin sections were made from six tesserae (five of white chalk and one of dark blue-grey limestone) extracted from a mosaic fragment (SF 1084) found in Room 6. Only bivalve fragments were seen in the limestone sample (D06) and so this will not be considered further. The five chalk sections all contained microfossils: these consisted of keeled and unkeeled planktonic foraminifera and variable numbers of the algal sphere Pithonella sphaerica. The unkeeled foraminifera included long-ranging species such as Hedbergella brittonensis, H. delrioensis and Heterohelix species, including H. moremani. The keeled foraminifera included the index species Marginotruncana marginata, which first appears at the base of BGS Foraminiferal Biozone 8, in the latest Cenomanian. However, it was noticeable that only one species of benthonic foraminiferid could be identified (Gavelinella sp.). In contrast, the algal sphere Pithonella sphaerica was found in all of the chalk thin sections, occurring rarely in one (D02), but either commonly or in ‘flood’ proportions in two others (D04 and D03 respectively). Occasional P. ovalis were also found in one thin section (D05). The appearance of Marginotruncana marginata constrains the date of this sample to the very Late Cenomanian or Early Turonian.
DISCUSSION
The underlying solid geology of the Roman city of Ratae Corieltavorum comprises the Triassic Mercia Mudstone Group sedimentary deposits, which to the east of the modern city are succeeded by younger Jurassic limestones and mudstones that form a series of rolling hills stretching towards the city of Peterborough in north Cambridgeshire. Unlike at Brading on the Isle of WightFootnote 35 or at Roman Silchester,Footnote 36 there is no immediate source of rock from the Cretaceous Chalk Group in or around Leicester, although fragments of chalk occur in local Quaternary glacial till deposits, such as the Oadby Member, a component of the Wolston Formation. However, the taxa identified in the Oadby Member chalk fragments are Coniacian to Santonian in ageFootnote 37 and date to the Late Cretaceous, and the fragments themselves are too small and too few to have been used systematically as a source of chalk for tesserae (see fig. 4). Some Leicestershire gravels, though, do contain larger (cobble-sized) clasts of chalk that might represent a possible local source for the manufacture of tesserae. However, the systematic use of glacial erratics as a chalk source would be expected to produce a wider microfossil signal in the tesserae than the consistent Late Cenomanian–Early Turonian one obtained from the Leicester material, and it seems more likely that the chalk used to manufacture the Vine Street mosaics has a remote source.
Till of the Oadby Member (Quaternary) at outcrop, showing entrained chalk fragments. (Photo: courtesy of Mr Keith Ambrose, British Geological Survey)
The long-distance transport of chalk need not surprise us. Wilkinson et al. Footnote 38 noted the likelihood of chalk having been transported from the south coast of Britain 100 km northwards to Roman Silchester (Calleva Atrebatum), despite local chalks outcropping in the near vicinity of the town: a decision that may have been made on grounds of quality, since long-distance transport must have incurred some expense and at least a modicum of inconvenience. However, the long-distance overland transport of bulky items within the province seems always to have been a possibility. One of the earliest known examples of fine freestone carving in Britannia, the Claudian tombstone of the auxiliary cavalryman Longinus, son of Sdapezematygus,Footnote 39 was carved from a Middle Jurassic oolitic limestone (Painswick stone) that had been transported some 230 km from the Gloucestershire Cotswolds to the legionary garrison at Colchester in Essex.Footnote 40 Rubble from the Temple of Claudius precinct at Colchester has also revealed a sample of Middle Jurassic Lincolnshire Limestone,Footnote 41 while one of the paving stones found at the precinct is a possible example of Lower Jurassic Ham Hill limestone from Somerset.Footnote 42 Hayward suggests that the long distances travelled by these raw materials could reflect either the involvement of the military in their provision or a lack of information during the earliest years of the occupation on the availability of more local sources of suitable stone.Footnote 43 But Painswick stone does take a fine polish, and Hayward adds that its appearance during the first century a.d. in several non-military contexts in Silchester, Caerleon and London might also reflect a choice based on this quality.
The presence of tesserae at Vine Street cut from chalks dating to both the Late Cenomanian and Early Turonian stages suggests that they may have originated from a single source, since these stages are contiguous in the stratigraphical column. A possible site might be a quarry that exposed the boundary between the two stages. However, the nearest Late Cenomanian–Early Turonian stage chalk outcrops to Leicester are found at some considerable distance: in the Lincolnshire Wolds, about 110 km to the north-east; in north Norfolk, some 120 km almost due east; in the Hertfordshire Chilterns, about 95 km to the south-east; and on the West Berkshire Downs, around 140 km to the south. Chalks from these two stages are also widely found along the south coast of England, from Beer (south-east Devon) to Dover (Kent) ( fig. 5). These last locations are obviously at greater distances from Leicester (>300 km), but as we have seen already, transport over such distances is not impossible.
From a geographical perspective, therefore, the potential source areas for the Vine Street chalk tesserae are widely spread. However, it is possible to use archaeological data to narrow down the geographical possibilities. It is clear from the mass of archaeological reports, watching-briefs, field-walking surveys and Heritage Environment Records (HERs) comprising the grey literature of Romano-British archaeology that the casual digging of pits for the local extraction of chalk around settlements was a common practice. However, there are places in which the archaeological evidence appears to show that the extraction of chalk was deliberate and systematic and on a large enough scale to suggest that actual quarrying was taking place. Superimposing the Roman road network of the second and later centuries a.d. onto a map of the UK showing Chalk Group outcrops of the relevant stages, highlights potential areas of investigation for such quarrying activities and also likely overland transportation routes for their chalk products ( fig. 5). The following sections of this paper, therefore, attempt to combine the above archaeological and geological approaches in order to evaluate the relative likelihood of the geographical areas mentioned above being a provenance for the chalk used to construct the Vine Street Town-House mosaic floors.
Map of England and Wales, showing (i) the distribution of Upper Cretaceous Chalk Group rocks and their intersection with Roman roads and (ii) main sites mentioned in the text (modern names). (Cretaceous Chalk data taken from Waltham et al. Reference Waltham, Simms, Farrant and Goldie 1997 , ch. 7, fig. 1; position of Cenomanian and Turonian Age chalk taken from British Geological Survey Edina Digimaps (Geological Map Data © NERC 2011); Roman roads based on Ordnance Survey Map of Roman Britain (5th edn, 2001))
NORFOLK
Although Chalk Group rocks form the bedrock of much of north and central Norfolk, their exposure is limited owing to a much later deposition of Pleistocene sedimentary deposits. Chalks of Late Cenomanian and Early Turonian stages are exposed only as a long narrow ribbon running inland from the coast at Hunstanton along the chalk ridge (the East Anglian Heights) that separates the flat Fenland to the west from the flat Broads to the east. The chalk of these stages most easily accessed by the Roman road network is found around Swaffham and Thetford.
The western edge of the Heights culminates in the West Norfolk Ridge, an outcrop of sandstone and mudstone along which lies a small concentration of villas about 12–15 km to the north-west of Swaffham. Excavation of these villas revealed only plain mosaics appearing to date to the second century a.d., suggesting these were early foundations; if they were still occupied in the fourth century, they do not seem to have installed any mosaics dating to this period.Footnote 44 Indeed, with the exception of the large cluster found in Colchester and its environs, Cosh and Neal record very few mosaics from East Anglia as a whole. This surprising absence of display of wealth in an area of generally rich farmland has been interpreted by Jones and MattinglyFootnote 45 as evidence for the retarded development of the Icenian élite as a long-term legacy of the Boudican revolt and also possibly for the establishment of large imperial estates on confiscated land. The number of hoards of silver and gold coin and plate dating from the first to the fifth centuries found throughout Norfolk show that at least some local wealth did exist;Footnote 46 perhaps its owners preferred to keep it portable rather than to translate it into something more permanent. Certainly it does not appear to have been translated into mosaics: Cosh and Neal note that no fine mosaics of any period have come to light in the county and that plain red tessellated pavements are the norm, even in villas where excavation has revealed the presence of bath-houses and painted plaster.Footnote 47 It seems, therefore, that tessellation was regarded locally as more a functional than a decorative practice; and although this may, and probably did, involve the utilisation of local chalks, it does not suggest that these chalks were exploited on a large enough scale or for a long enough period to have acted as a source of tesserae for Leicester, some 120 km distant.
THE CHILTERN ESCARPMENT
Chalk dating to the Late Cenomanian and Early Turonian stages comprises, in this area of England, the upper part of the ZigZag Chalk Formation and the whole of the Holywell Nodular Chalk Formation.Footnote 48 Exposures of these two stages are found along the length of the northern edge of the Chiltern escarpment, from Cambridgeshire in the north-east to Wiltshire in the south-west, and although outcrops are nowhere large in scale and are occasionally very patchy, nevertheless the geographical area under consideration is extensive.
Here again it is instructive to consider the Roman road network (see fig. 5). The routes south from Leicester ran in three directions: south-east to Colchester via Godmanchester; south-south-east along Watling Street towards St Albans and London; and south towards Silchester and the coast. These routes cross chalk of Late Cenomanian and Early Turonian age at Royston and Baldock, near to Stevenage in Hertfordshire; around Dunstable in Bedfordshire; and in the vicinity of Lambourn on the Berkshire Downs. It seems sensible therefore to look in these areas for evidence of the quarrying of chalk that could have been used to manufacture the Vine Street tesserae.
It is known that chalk from the Chiltern escarpment was utilised in Roman times. The second-century villa at Totternhoe in Bedfordshire utilised dressed blocks of Totternhoe Stone, the local ‘clunch’ (hard building stone), in the construction of foundations and hypocaustsFootnote 49 and a block of the same stone was found paving Watling Street under the Edgware Road in London.Footnote 50 Chalk blocks were also used in the construction of two early villas at Alfred's CastleFootnote 51 and nearby Maddle Farm,Footnote 52 both sited on the Berkshire Downs close to Lambourn. There is also evidence of quarrying activities in the Chilterns. Chalk quarries or pits dating to the Roman period have been identified at Barrington, about 16 km south-west of Cambridge;Footnote 53 at a site close to Todd's Green, about 3 km west of the A1(M) at Stevenage (Herts.);Footnote 54 at Datchworth (Herts.), a few kilometres south of Stevenage;Footnote 55 about 10 km south-west of Avebury (Wilts.);Footnote 56 and possibly also at Verulamium, both to the northFootnote 57 and southFootnote 58 of the Roman town.
All of the above quarrying sites are within reach of Leicester on the Roman road system, but none of them appears to have been the source of the chalk used for the Leicester tesserae. Totternhoe Stone, used at the eponymous villa and also excavated at Barrington, dates to the mid-Cenomanian and so is slightly too old, and the quarries west and south of Stevenage and those at Verulamium expose chalks higher in the stratigraphical column, which are therefore too young. The series of shallow pits south-west of Avebury might expose chalk of the correct age, depending on their exact location, but the layout of the pits, dug parallel to the Roman road from Bath to Marlborough for 500 m on the north side of Morgan's Hill and about 1 km on the south side of Cherhill Down, suggests localised quarrying for hardcore for the metalling of the road rather than large-scale extraction. Other evidence for chalk quarrying in the Morgan's Hill and Cherhill Down area, which interestingly centres on linear extraction of the hard bed of Chalk Rock found locally, has been dated to the post-medieval period.Footnote 59
There is, however, evidence that chalk of the correct age was quarried in the Roman period at Baldock (Herts.). Baldock was an important settlement in the Late Iron Age that developed into a small town in the Roman period.Footnote 60 Excavation of a site in the north-west of the town on a chalk ridge that probably formed the boundary of the Roman settlement was carried out by North Hertfordshire District Council's Field Archaeology Section.Footnote 61 The site (The Stationmaster's House) lies at the junction of the Icknield Way and the Roman road leading north from Baldock to Godmanchester and thence either to Lincoln or Leicester (fig. 5). Trial-trenching exposed a large excavation in excess of 20 by 15 m in area and about 2.5 m in depth; this had been cut into the side of the chalk ridge and the chalk extracted using a series of smaller stepped cuts that had left angular faces. Contextual evidence suggests that the quarry came into use during the third century a.d. and continued in use into the fourth. It is not possible to know what the extracted chalk was used for: chalk was used for agriculture as well as building and it is possible that even a large quarry may have served only Baldock and its environs. However, since the quarry lies directly on chalk of the Late Cenomanian and Early Turonian stages, and appears to have been operating at the time the Vine Street Town-House was being refurbished, and also has good road access to Leicester, there is at least the possibility that it may have provided chalk for the Vine Street tesserae.
The Stationmaster's House quarry is not the only evidence for chalk extraction in Baldock. A large pit dug into the Holywell Nodular Chalk Formation discovered during excavation in advance of development in the town was also interpreted as a chalk quarry dating to the Roman period.Footnote 62 However, fill from this pit comprised a series of deposits of silty clay and redeposited chalk containing pottery dating from the second to the late third century a.d. This would limit the quarrying activity to the first or early second centuries a.d., which is too early a date to suggest that material from here might have been used in the production of the Vine Street tesserae. It will be interesting to see whether further excavation in the Baldock area uncovers additional evidence for chalk extraction and whether examination of chalk tesserae from elsewhere suggests that the material might have been supplied from the town.
The use of Totternhoe Stone raises the interesting question of chalk selection. It is noticeable that the Chalk Group rocks exposed at three of the above locations contained a condensed bed of hard, white chalk (Totternhoe Stone at both Totternhoe and Barrington, and Chalk Rock at Todd's Green west of the A1(M) at Stevenage). The question, therefore, arises as to whether these particular horizons were being sought out deliberately. This would make sense for the production of tesserae, as harder chalks should be considerably harder wearing underfoot than softer ones. In fact, the Late Cenomanian–Early Turonian Holywell Nodular Chalk Formation does include, both at Baldock and in the eastern reaches of the Chilterns, a condensed bed of hard, off-white, blocky fractured chalk (the Melbourn Rock Member) that would have been the ‘right’ age for a source for the Vine Street tesserae and might have been considered a suitable medium for their manufacture. But, disappointingly, no evidence has emerged from excavation to support the hypothesis that this hard bed of chalk was being specifically targeted for quarrying.
It is not possible to form a judgement as to whether Chiltern chalk travelled to Leicestershire. We know that Totternhoe Stone travelled from Bedfordshire to London. Tesserae cut from chalk are found at Little Wymondley villa (Herts.), but since this villa is within a few kilometres of both Baldock and Stevenage, this does not constitute much of a movement of materials.Footnote 63 However, there is some evidence that material was travelling in the opposite direction. Swithland slate from Charnwood in north-west Leicestershire has been identified in roof-tiles from one of the buildings at Bancroft (Bucks.)Footnote 64 and also in dark blue-grey tesserae occurring in mosaics found at the villa;Footnote 65 and other possible identifications of Swithland slate have been made in fourth-century villa mosaics from nearby Foscott (Bucks.) and Thenford near Banbury (Northants.).Footnote 66 McWhirrFootnote 67 injects a cautious note concerning the identification of ‘Swithland’ slate, but nevertheless his records indicate that the material has been found at sites as far as 60–80 km from Ratae.
Assuming that the above identifications are correct, this evidence, although slight, does suggest a movement of Swithland slate southwards from Leicestershire during the mid-fourth century a.d. This is perhaps not unconnected with the proposed Midlands Group of mosaicists active at the same time;Footnote 68 as Neal and Cosh point out, mosaics at Bancroft Roman villa, located in the suburbs of Milton Keynes in Buckinghamshire and dating to around a.d. 350, show strong stylistic similarities to coeval mosaics from villas at Drayton in LeicestershireFootnote 69 and the slightly later mosaics at Great Casterton in Rutland.Footnote 70 Although any such movement of material (and possibly in the case of Bancroft, also mosaicists) is later than the suggested early fourth-century date for the Vine Street Town-House mosaics, there is a possibility that it was a continuation of an earlier trend; in which case, it may not be implausible that chalk material from the Baldock area in Hertfordshire was moving northwards in a reciprocal movement. Indeed, the nearest source for the chalk tesserae found at the late third- to early fourth-century villa at Whitehall Farm on Watling Street, some 13 km north of Towcester, would be the Chiltern escarpment around Dunstable.Footnote 71
THE NORTH-EAST
Late Cenomanian and Early Turonian stage chalk is also found in Lincolnshire and north-east Yorkshire, where it comprises the upper part of the Ferriby Chalk Formation and the lower part of the Welton Chalk Formation; the former consists mainly of grey, marly chalk whilst the latter is dominated by thick beds of chalk containing flint nodules.Footnote 72 Much of the solid geology in this area is obscured by Pleistocene sedimentary deposits, but the Chalk Group rocks to which these two formations belong are exposed along the steep slopes of the northern and western edges of the Yorkshire and Lincolnshire Wolds. The particular chalks of the Late Cenomanian and Early Turonian stage outcrop in a narrow band which curves inland from the Yorkshire coast at Bempton, close to Flamborough Head, before turning through 90 degrees to run south-east to the Humber estuary. From here the outcrop continues to run along the western scarp edge of the Lincolnshire Wolds to reach lower ground around Candlesby close to Skegness (fig. 5). As with the Chiltern escarpment, therefore, the Late Cenomanian–Early Turonian stage chalk outcrop in the Yorkshire and Lincolnshire Wolds is geologically constrained, but geographically extensive, and it is necessary to see if potential source areas can be identified through archaeological considerations.
About half of the thirty-odd Roman villa sites in Yorkshire are found on the western edge of the Yorkshire Wolds, where the chalk meets an impervious stratum to form a natural spring line and the soils are less heavy than those in the Vale of York and so easier for arable cultivation.Footnote 73 This is in contrast to Lincolnshire, where most of the villas are sited along or in proximity to Ermine Street and relatively few are sited on the Wolds themselves.Footnote 74 The majority of the mosaics found in these north-eastern villas date to the third or fourth centuries a.d. and are remarkable in that very few are figured: Neal and Cosh speculate that this might be a cultural rather than an economic phenomenon.Footnote 75 The rising prosperity of the North-East in general, and Yorkshire in particular, during the third and fourth centuries a.d. and possible reasons for the comparative lack of villas in the area are discussed succinctly in Wilson et al. Footnote 76
The main north–south movement of men and materials in the North-East bypassed the chalk outcrops of Yorkshire and Lincolnshire. Traffic moved north along Ermine Street from Lincoln to the Humber crossing at Winteringham–Brough and north from there towards York, Catterick and the northern frontier. An alternative route north from Lincoln bypassed the Humber crossing by running inland to the Trent crossing at Littlethorpe and then on to York; this may even have become the preferred route north by the third century a.d. This meant that both the main routes north from Lincoln passed to the west of the chalk escarpment. However, Ermine Street was connected with potential chalk sources in the Wolds by a series of secondary routes. Two of these connected the main highway with ports on the east Lincolnshire and Yorkshire coasts: the more southerly of these ran from Lincoln to the coast at Skegness and a (presumed) ferry crossing across The Wash to a point west of Brancaster in north Norfolk, whilst the more northerly ran east from York across the Yorkshire Wolds to the coast at Bridlington. A third route ran north from the Humber estuary to the fort and settlement at Malton in the Vale of Pickering. Other roads, linking Ermine Street to its eastern hinterland (to Caistor, for instance), and linking Horncastle to Caistor and the Humber estuary at South Ferriby, have been suggested; practical considerations suggest that such routes must have existed, but definite evidence for them is lacking.Footnote 77
Water transportation routes to Leicester from the east and north-east were generally good. The town was connected to the Humber estuary via the rivers Soar and Trent, and to York by upstream travel on the Ouse. Lincoln, The Wash and the Fenlands were accessible through the Foss Dyke which connected the Trent at Torksey with the Witham to the west of Lincoln. However, only the Soar–Trent–Humber route passed close to any of the potential chalk source areas in the Wolds.
It is difficult to quantify the Roman use of chalk in the North-East. The use of stone for building in York during the occupation has been well studied,Footnote 78 but there is little mention of chalk. Gaunt and BucklandFootnote 79 state that chalk was used for sill walls on several Roman villa sites in East Yorkshire, but do not provide details of specific locations. Whitwell provides some information on quarrying activity around Lincoln and states that chalk was used for foundations for the putative Roman villa at Worlaby.Footnote 80 Other sources provide information on the use of chalk for tesserae. Gaunt and Buckland state that chalk was used extensively for the manufacture of white tesserae and that examples of such tesserae have been found in York, but without providing further details:Footnote 81 Price and Wilson, however, state that chalk tesserae were found in pavements from Aldwark and Clementhorpe.Footnote 82 Neal and Cosh record about ten mosaics from York; they also record over thirty mosaics from the colonia at Lincoln and a further ten from the nearby villa at Greetwell, but unfortunately without being able to confirm the use of chalk tesserae in any of them.Footnote 83 However, they do record the presence of chalk tesserae in pavements from Haceby in Lincolnshire and from Aldborough, Harpham, Langton and Wharram Grange in Yorkshire, all of early, or probable, fourth-century a.d. date.Footnote 84 Chalk tesserae were also used in pavements at the Roman villa at Winterton (sited about 10 km north of Scunthorpe) and chalk tesserae chippings were found above a floor in one of its rooms (Room 21), the suggestion being that the latter were the residue from patching work undertaken on some of the mosaics at the other end of the building.Footnote 85 Pragmatism suggests that some of the ‘white tesserae’ described by Neal and Cosh as making up the background, borders or fine detail of the (largely) geometric patterned pavements found elsewhere in Yorkshire and Lincolnshire were also manufactured from local chalks, but in the absence of positive identification, this has to remain a conjecture.
With regard to provenance, the chalk tesserae found at Winterton in north Lincolnshire are described as localFootnote 86 and indeed the villa is less than 10 km from the foot of the chalk escarpment of the Lincolnshire Wolds. However, Neal and Cosh report that the white tesserae housed in Hull and East Riding Museum and attributed to the fourth-century villa at Harpham were found to have originated from sea-worn rock chalk pebbles and may have come from the chalk shore source closest to the villa, which is the bay at Bridlington about 10 km to the east.Footnote 87 This is interesting, since the excavation report for the much earlier baths at Well (Yorks.) — sited north of Ripon and about 5 km west of Ermine Street on its inland route between Isurium Brigantum and Cataractonium — gives a probable geological provenance of ‘the beach area north of Bridlington’ for tesserae found at the site that are made from a hard white chalk.Footnote 88 As Bridlington is over 100 km from Well, assuming travel westwards from the coast across the Wolds to York and then northwards via Ermine Street, this would imply that chalk from the coast was travelling a considerable distance inland by about the mid-second century a.d.
It is possible that Bridlington might have been a source of chalk for tesserae. The regional dip of the Chalk Group rocks to the north and south of Flamborough Head exposes a succession of stages around the coastal cliffs, which includes an exposure of Late Cenomanian and Early Turonian stage chalk to the north of Bridlington around Bempton Cliffs. Several sections of these coastal chalk exposures are today noticeably difficult or even impossible to accessFootnote 89 and presumably presented similar difficulties in Roman times. However, if the above provenances are correct, the more accessible of these exposures might have provided chalk for tesserae found at Harpham and at Well, and also for other villas in the region. In this context, it is perhaps worth noting the piles of tesserae found during excavation at Rudston Roman villa, some 7 km west of Bridlington. The tesserae found in Building 3 at Rudston were sorted by size and colour, whilst those found in Building 7 were unsorted but numbered around 1,500.Footnote 90 This was thought by Smith to constitute evidence for the manufacture of tesserae at the villa, either for domestic use or as a cottage industry.Footnote 91 It is interesting to note that, of the material found in Building 3, the largest pile was of small white tesserae. If these were cut from chalk, it is possible that they too may have been sourced from the Bridlington area.
Given the above information, it would not be surprising to find that chalk for the local production of tesserae was quarried either from exposures on the shore or inland in the Wolds, even though evidence for quarrying on the scale of the excavations described above at Baldock has not been found. However, it is hard to prove that any such material might have moved to Leicester. Neal and Cosh identify stylistic affinities between two mosaics in Leicester and a second-century mosaic from Well, suggesting that they might be the products of the same craftsmen, as well as a fourth-century mosaic from Haceby.Footnote 92 The use of Leicestershire Swithland slate roof-tiles at the settlement of Haceby is also attested,Footnote 93 but this does not constitute enough information to demonstrate a strong link between the two areas. However, accessible chalk of the same age as that used to manufacture the Vine Street tesserae is found in the North-East, including around Bridlington; many of the mosaics laid in the North-East date to the fourth century and so were utilising chalk tesserae at the same time as the Vine Street mosaics are thought to have been laid; and the piles of tesserae at Rudston might possibly be evidence of a tesserae workshop, if only a local one. This means that a source of chalk in the North-East for the Vine Street tesserae is still a tantalising possibility.
THE SOUTH
Much of the Chalk Group responsible for the familiar chalk landscapes of southern England is younger than the chalk used to manufacture the Vine Street tesserae. Outcrops of Late Cenomanian and Early Turonian stage chalk are limited to the scarp faces of the North and South Downs, a narrow outcrop in the Isle of Wight and an Early Turonian outcrop at beach level at Beer in south Devon. The exposures on the Downs tend to be elongate and are occasionally intermittent, but in general terms form a horseshoe whose arms run north-east and south-east from the vicinity of Petersfield (Hants.). Broadly speaking, the northern arm of the horseshoe follows the line of the North Downs Way to culminate in cliffs at Folkestone and Dover and the southern arm of the horseshoe follows the line of the South Downs Way to culminate in cliffs at Beachy Head. The relevant chalk outcrops are crossed by a series of Roman roads originating from London and connecting the port with the south and east coasts (fig. 5). All of these routes provided good communications with Leicester.
Both South-East and South-Central England were occupied and settled earlier than the rest of Britannia and experienced earlier prosperity. However, the continual uneasiness and sporadic instability of the political situation at home and on the continental mainland during the third century may have effected a downturn in the economic prosperity of the region during the fourth, particularly in the South-East. This would explain the large number of mosaics in this region that can be dated to the second century and the comparatively few that can be dated to the fourth.Footnote 94 This economic situation is very different to the one found in the South-West and also in the North-East: in these areas, villas were being established or developed during much of the fourth century and a considerable number of mosaics and several mosaic workshops date to this period.Footnote 95
Chalk tesserae are confirmed at several sites in the South, although the widespread use by mosaicists of the paler geological facies in both geometric and figured pavements suggests that it must have been used at very many more. Neal and Cosh record the use of chalk tesserae from mosaics found in Hampshire, at West Meon;Footnote 96 in West Sussex, at Chilgrove, Fishbourne, Pulborough and Southwick, and in East Sussex at Preston;Footnote 97 in Kent, at Boxted and Folkestone;Footnote 98 and in Surrey, at Walton-on-the-Hill and Worpleston.Footnote 99 Chalk tesserae have also been identified from town-houses in Ilchester (Somerset), at sites in Church StreetFootnote 100 and in Castle Yard, High Street and Limington Road;Footnote 101 at Halstock villa (Dorset), near to IlchesterFootnote 102 and at the Applegates site in Dorchester;Footnote 103 and at Badbury and Tockenham (Wilts.).Footnote 104 Of the mosaics that are dated, only those from sites further west (Ilchester, West Meon, Chilgrove, Badbury and Halstock) are fourth-century; the other sites either flourished earlier or are of unknown date. It is likely that this reflects the greater stability and affluence of the west of the province at this time, as evinced by the groups of mosaicists thought to have been operating out of Dorchester and the Cirencester area in the fourth century.Footnote 105
In five instances the provenance of the chalk used to manufacture tesserae in the South is either known, or strongly suspected. The chalk tesserae workshop at Norden, Corfe Castle, in the Isle of PurbeckFootnote 106 seems to have utilised chalk from a local source,Footnote 107 as apparently did mosaicists at Brading Roman villa on the Isle of Wight;Footnote 108 chalk from Dorset was used to manufacture tesserae for mosaics from Silchester;Footnote 109 chalk from Stonehill Down, Purbeck, was used for tesserae from the Applegates site in Dorchester;Footnote 110 and chalk from the Marlborough Downs has been identified from Tockenham.Footnote 111 Tesserae at Norden were being produced as early as a.d. 70, but the evidence suggests that activity at the site declined after the mid-second century before experiencing a modest revival in the late third. Whether this revival included the manufacture of chalk tesserae is not clear, but there is not much evidence for it; very few tesserae have been found dating to this period (only 16, as opposed to the >1,500 examples and their associated waste chippings from the earlier context) and the later chalk material consisted predominantly of sawn slabs of chalk for use as floor tiles or wall veneers.Footnote 112 It would appear therefore that chalk tesserae manufacture at Norden was confined almost entirely to the earlier period, and as Sunter points out, it might not be a coincidence that this was when the floors for the Flavian villa at Fishbourne were constructed.
The possibility of supplying chalk to Leicester from the south of the province is an interesting one, given its technical feasibility and the fact that other lithologies are known to have travelled considerable distances. However, the archaeological evidence for any actual quarrying of chalk in the South in Roman times is limited, which makes it difficult to suggest a possible source area. Chalk quarries dating to the Roman period have been identified during excavation at the County HospitalFootnote 113 and Colliton ParkFootnote 114 sites in Dorchester (Dorset) and possibly also to the west of the town at Middle FarmFootnote 115 and Winterbourne Monkton;Footnote 116 at Tilshead (Wilts.);Footnote 117 in Kent, at Birchington in ThanetFootnote 118 and Chartham near Canterbury,Footnote 119 and also at Keston Roman Villa and the A2/A282/M25 Improvement Scheme site in Dartford District;Footnote 120 and in Essex, at Coulsden in CroydenFootnote 121 and close to the London Road at Purfleet.Footnote 122 However, the main periods of operation for all but one of these quarrying activities appears to have been before the mid-third century a.d., so if these were supplying chalk to a wider hinterland than their immediate neighbourhood, it does not seem that any of them was still in production at the time of the laying of the Vine Street mosaics. The exception is the chalk quarry on the Dartford District site, which from excavation evidence appears to have been considerable in size and also operational beyond the mid-third century. However, neither the Dartford District nor any other of the above quarries appears to have been sited on the rather limited outcrops of Late Cenomanian or Early Turonian chalk and so none could have acted as a source for the Vine Street tesserae.
This lack of evidence for chalk quarrying in the south of England after the mid-third century, coupled with the paucity of later mosaics from the South-East, does not suggest a thriving mosaic industry in this part of the province. It is worth noting that a number of mid-fourth-century mosaics from Silchester and London show stylistic affinities with the Saltire Group of mosaicists working out of Cirencester (Corinium): in the case of London, Neal and Cosh speculate that this might be because the London-based Acanthus workshop may have ceased to operate by the late third or early fourth century a.d. and so expertise had to be imported from the West.Footnote 123 Probably, this makes it unlikely that the chalk for the Vine Street tesserae was sourced from anywhere in the South-East, although it does not eliminate possible sources further south and west. This begs the question of where the chalk for the many fourth-century mosaics being laid by the Corinium and Durnovarian Groups in the West and South-West was being sourced, and also whether the mosaic ‘workshops’ operating out of the region at this time were using the same or different sources of chalk. A microfossil analysis of chalk tesserae from a selection of these mosaics, similar to that carried out on the Vine Street tesserae for this paper, might provide some answers and the authors commend this approach to future researchers.
SUMMARY
It is clear from the above discussion that it is not possible to draw a definite conclusion as to the provenance of the chalk tesserae used in the construction of mosaics in the Vine Street Town-House. However, it has been possible to suggest two possible source locations, both of which satisfy the geological and the archaeological criteria. These are Baldock in Hertfordshire and Bridlington in Yorkshire. Baldock is the nearer of the two and the easier of access, given the road network, and therefore on these grounds, the more convincing suggestion. However, we should not discount the possibility of a northern source. The slower rise to prosperity in the North-East meant that mosaics were being laid there well into the fourth century a.d., which must have created a demand for materials, if only a local one. Further investigation into the provenance of chalk tesserae from mosaics in Yorkshire might yet produce surprises.
ACKNOWLEDGEMENTS
The authors would like to thank the two anonymous referees for their comments and also the University of Leicester Archaeological Services (ULAS) for providing chalk tesserae from the Vine Street Town-House for analysis. IPW publishes with the permission of the Executive Director of the British Geological Survey (N.E.R.C.).
