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Artefacts & Environmental Evidence: The Environmental Evidence

Stephen Rowland and Nicky Toop with Allan Hall and Harry Kenward

Assessment of Sediment Samples from Blue Bridge Lane

1.0 Introduction

Excavation at Blue Bridge Lane encountered 1285 deposits dated from the Roman period to the 20th century of which 225 deposits were sampled for assessment, yielding well in excess of 4125 litres of sediment. The majority of sampled material derived from pit features, many of Anglian date, but ditches, post holes, scoops, kilns, layers and a well were also represented. Excavation at Fishergate House encountered 452 deposits dated from the Roman period to the 20th century of which 42 deposits were sampled for assessment, being more than 605 litres of sediment. The majority of material derived from pit features, of which F64F, dated to the Anglian period, was the largest and most important but ditches, post holes, cremations, a hearth and a sunken feature building were also represented.

The amount of sediment taken, which ranged from 1 to 100 litres, and its subsequent treatment, depended upon the deposit and feature type, the amount of sediment available, and the potential of this material to be informative when combined with stratigraphic and dating evidence. Dependent upon their potential and volume, samples were subjected to one or a number of three processing techniques of increasingly fine recovery. With the material from Blue Bridge Lane, sediment from 81 contexts was subjected to fine-mesh sieving, samples from 206 contexts was processed through flotation in a Siraf (water recycling) tank, and thirteen 10 litre buckets from thirteen contexts were retained for further analysis due to potential preserved uncharred organic content. Nine of these retained samples were subjected to more detailed laboratory assessment along with 20 Siraf washovers selected on the basis of archaeological importance and abundance of charred organic matter. In addition, a large volume of sediment was processed in the field through wet coarse-sieving within a 10mm mesh. At Fishergate House, samples from forty-two contexts was processed through flotation in a Siraf (water recycling) tank, and fifteen 10 litre buckets from fifteen contexts were retained for further analysis due to potential preserved uncharred organic content. Six of these retained samples were subjected to more detailed laboratory assessment along with six Siraf washovers selected on the basis of archaeological importance and abundance of charred organic matter.

1.1 Aims & Objectives

The aim of the excavation was to record and characterise archaeological deposits for the purpose of data retrieval in advance of their destruction. The aim of the sediment analysis was twofold: to maximise the amount of data recovered from the excavated sediments and to establish the character of the archaeological sediments in terms of the presence and preservation of uncharred and charred organic material such as plants and insects that could be further studied toward the elucidation of past diet, living conditions and building materials as well as the reconstruction of site formation processes and waste disposal management.

1.2 Methodology

Siraf flotation was used for samples with potential for waterlogged preservation of organic materials, for fine charred organic matter (such as carbonised seeds and grains) or for particularly small finds and craft-working residues. Samples were washed down within a 1mm mesh held inside a water recycling flotation (Siraf) tank with the light fraction washed over into a 250 micron mesh. This light fraction was kept wet, as was the heavy residue if it contained uncharred organic material. Where there was evidence of uncharred material within flotation samples, and where the original sample size allowed, c.10 litres was retained for more detailed and thorough processing and analysis. Fine-mesh sieving was used for samples of large volume or lower priority where there was a likelihood of very small finds (such as beads and fish bones) and involved disaggregating material within a 2mm mesh with the aid of a hose. The residue of this process was then dried out. Dried residues from flotation and fine-mesh sieving were screened using 2mm and 5mm test sieves, producing three fractions (<2mm, 2-5mm and >5mm),all of which were retained but only the larger two were sorted for cultural and environmental materials. Other wet residues were not screened, merely being rapidly sorted and re-bagged. Notes were made on the abundance (rare, occasional, common or very common) and retention (discarded, sampled or kept) of these objects. Samples subjected to coarse-sieving tended to be those with little potential for organic remains, either due to preservation (following Siraf flotation of a proportion of the sample), or because of deposit status, or, for finds recovery when a large sample had already been processed for environmental remains. Such material was washed down within 10mm mesh using a hose gun. Any finds were separated and kept while the rest of the residue was immediately disposed of. The nine samples subjected to more detailed assessment used the usual methods of Kenward et al. (1980) involving disaggregation and sieving but were 'washed over' and dried rather than paraffinated because of a perceived lack of insects. Plant remains and other components of the dried washovers from this process and their residues along with those from the 20 selected Siraf washovers were recorded briefly by 'scanning', identifiable taxa and other components being listed directly to a PC using Paradox and Access software.

2.0 Results

With so many samples from different feature types and periods, it is difficult to succinctly summarise the data from flotation and fine-mesh sieving. One overall trend was the generally poor state of organic preservation from most features. This has already been commented upon by O'Connor (1993) in regard to Anglian deposits from 46-54 Fishergate, where bone was similarly well-preserved and organic material equally poorly represented. Here O'Connor suggested that organic matter was deliberately collected for manuring local fields, and indeed, from Blue Bridge Lane and Fishergate House, there were very few deposits that from their colouration and texture could have been argued to have contained a high proportion of organic matter; rather, many deposits seem to be more clayey or gravelly. However, the marked subsidence of many Period 3 features suggests that organic matter was decomposing and compacting for centuries after deposition; this may be mainly the case for the primary cess deposits. The organic material that was present was frequently mineralised and found in association with the olive green soils likely to derive from faecal deposits. However, if organic material was removed for local manuring, which is perhaps not improbable given the peripheral location of the site, then it was done so throughout each period of occupation. Other reasons for a lack of organic material could relate more to preservation, where, despite being so close to the river, features may not have reached the water table, or, were periodically waterlogged, with such intermittent wetting and drying actually encouraging the decomposition of organic matter. Alternatively, the fact that many of the deposits are likely to have developed as middens before being redeposited into pits could mean that a large proportion of exposed organic rubbish could have decomposed prior to final burial.

Further limitations to the potential of material from Blue Bridge Lane and Fishergate House are the high degree of intrusion and deposit recycling as indicated by the pottery. Indeed, many of the Anglian features are dated not so much by contemporary pottery, but more so by the absence of later pottery and the presence of residual Roman sherds.

Period 2 Roman Features

At Blue Bridge Lane samples from a total of four contexts from four features (three ditches and a cremation) along with four floating contexts were subjected to assessment. There appeared to be no uncharred organic preservation. Slag and hammerscale was present in many contexts, albeit rarely, but was recorded as occasional from cremation F394B C1790B. This could be due to the misidentification of vitrified fuel ash and other cindery pyre products, but might also relate to the destruction or decomposition of iron objects. Charcoal was also more likely to occur in contexts containing slag. Bone was present but not particularly common. Rare CBM fragments and ceramic material was noted in ploughsoil C2133B.

Fishergate House sediment samples were assessed from seven contexts from five features, including a ditch, a gully fill and three cremations, and from a layer interpreted as a Roman soil (C1501B). Rare amounts of magnetic material were present in most cases and may be natural rather than micro-slag or hammerscale; charcoal was present in only two contexts. Bone was present in all deposits, but usually rare in cremation features. CBM and ceramic were identified in all deposits, though generally noted as rare. Cremations 2 and 3 contained amounts of burnt clay fragments; it is possible that they represent burnt earth from the pyre site.

Period 3 Anglian Features

108 deposits derived from Fishergate House and Blue Bridge Lane were dated to the Anglian period; these came from a total of twenty-three features, of which all but two have been identified as pits. The remaining features, F46B and F225B represent a possible well and a bonfire kiln respectively. Of the 108 samples, only five (pit F13B C1881B, C1904B and C1913B, pit F381B C1853B and C1858B) contained limited ancient uncharred organic matter. More rarely, uncharred organic material was collected from flotation and fine-mesh sieving samples (including pit F273B C2095B and C2103B, pit F351B C2113B, F381B C2063B (single cases), pit F381B C1847B and C2063B, pit F427B C1936B and C2090B), and in some instances these were of modern contaminant seeds.

Charred organics such as seeds, grains and pulses (as opposed to charcoal per se) were a little more common, but were neither widespread nor present in large quantities. All cases were recorded from pits; the lack of such organics from F225B further supports the use of the feature as a bonfire kiln rather than for grain drying purposes. The presence of possible burnt bread from F225B C1494B might also offer an alternative interpretation of a bread oven, but such material has been recovered from a range of features and contexts. The presence of charred bread could mean that loaves were baked in the near vicinity, with burnt off-cuts disposed of close to their site of manufacture (possibly even thrown back into the fire), or, they could be burnt fragments that have passed through the digestive tract. Burnt grain was found in large quantities or recorded as frequent from the residues of F13B C1144B, F46B C1167B, F225B C1494B, F241B C1518B, F381B C1858B, F408B C1906B, and from F520B C1811B and C2120B, while a presence in fourteen of the other contexts containing charred organics was restricted to small amounts (recorded as rare). Detailed assessment of selected washovers has identified evidence for a range of cereals including oats, rye, club wheat, wheat and most commonly, barley, while field bean and apple were present in certain contexts and carbonised hazelnut shells were widespread if not common. Overall, the edible plant assemblage seems typical for the period and location. Barley was also the chief cereal recorded from Anglian levels at 46-54 Fishergate (Allison et al. 1996a; b), though this may reflect an origin in, for example, straw from thatch, rather than grain from stores for human use or from domestic fires and so may not properly represent the relative importance of this cereal to the local inhabitants. Further possible evidence for thatch or plant litter is that from pit F408B C1906B which is important in the light of the limited structural remains from Anglian Blue Bridge Lane.

Fourteen of the contexts derived from pits F427B and F458B, which upon analysis of the pottery and stratigraphy, were dated to the Anglian period. The overall amount of carbonised matter within the wash-overs of these deposits tended to be small, and a total of seven contexts contained charred grain or seeds identified during detailed assessment as wheat, oat and barley. There appeared to be no uncharred organic preservation beyond some mineralised seeds in F427B C2092B and F458B C2095B and these, along with a few cases of faecal concretions would indicate that these features had received quite significant amounts of faecal material and are likely to have functioned as cess pits. Without wishing to produce a circular argument, cess pits seem more typical of the nature of activity associated with Anglian settlement rather than that of the less intense occupation of the Roman period.

Detailed assessment has indicated, through various forms of evidence, the use of other pit features as cess pits including F13B, F46B, F241B, F273B and F381B. Along with concretions and chewed (and in all probability ingested) fish bones, a few mineralised remains (including those of fly puparia likely to be attracted to squalid conditions), mostly (and quite typically) not identifiable, point to the presence in some deposits of probable faecal material (confirmed in at least two cases through the presence of Trichuris eggs in 'squashes' made on samples of 'concretions'). It seems likely that most of these deposits may have contained organic material at some stage, but decay has been so intense that the only vestiges of non-charred organic matter are in the concretions seen in many samples - though these were often bone-rich and may include material from, for example, dog coprolites as well as or instead of faecal matter from humans. Despite the presence of faecal material in a lot of deposits, the origin of many pit contents seems quite heterogeneous with charcoal and plant ash, likely to originate from domestic fires, also being common. It is possible that this material was periodically added to cess pits as a means of deodorisation.

Other food remains such as bone were well-represented and included high numbers of fish bones. Small vertebrates, particularly amphibians, were present in moderate proportions and indicate the likelihood that certain features were left open as the fills developed, inadvertently acting as pitfall traps. While the frequency of bone from individual contexts was highly variable (ranging from rare to very common, but never absent), greater concentrations of bone appear to have been present in pits F241B and F273B where frequency was often recorded as 'common', while from pits F13B and F143B proportions, particularly smaller bones, were generally recorded as 'rare' or 'occasional'. Other food debris such as molluscs was very rare overall, being limited to a few fragments of mussel and oyster shell, while crustaceans appear not to have been exploited; a single piece of egg shell was recovered from F353B C1772B.

Non-organic building materials were rarely common from Anglian deposits, with CBM, where present, generally being recorded as occasional or rare and consisting of small abraded fragments of Period 2 material. Daub was even less abundant, being recorded in small quantities from five contexts. Exceptions include pit F381B backfill C2054B where CBM was recorded as 'common', and bonfire kiln F225B C1494B wherein CBM and daub were recorded as 'common' and fragments of loomweight as 'very common'. It is possible that in this case the CBM and daub may be differentially fired loom weight.

Evidence for industrial activity in the form of slag and, more frequently, hammerscale was widespread, but appeared limited in scale, being present in most contexts, but only recorded as 'rare'. F381B seemed unusual in containing a higher number of contexts with occasional and even common amounts of slag and hammerscale. There appeared to be no correlation between concentrations of charcoal and higher proportions of slag and hammerscale. Lead was limited, but there was a noticeable concentration in F520B.

At Fishergate House nine contexts from F64F were sampled all of which were artefactually poor with very little in the way of pottery or ironwork although slag/hammerscale, likely to be > background noise =, was present in small quantities at most. Bone was again present in most, but was very common only in C1120F. Faecal concretions, mineralised seeds and crushed fish bones in basal deposits C1345F, C1349F, C1352F suggested that F64F had originally been dug as a cess pit, while a concentration of amphibian bones in C1352F implied that the cess deposits had accumulated quite gradually acting as a pitfall trap into which these creatures had inadvertently fallen.

Period 4 Anglo-Scandinavian

Three features of Anglo-Scandinavian date were sampled at Blue Bridge Lane for flotation, and a context from one further feature was sampled for fine-mesh sieving. The overall results were similar to the Anglian period, with limited evidence for non-organic building materials; CBM was notes as rare in F256B, and common from F314B, while daub was noted in F460B. Apart from a considerable quantity of charred grain, and rarer burnt seed from pit F460B, food remains mainly comprised animal bone (F256B C1574B). The amount of slag and hammerscale was consistently low and charcoal was moderate.

At Fishergate House twenty contexts from twelve features, including six pits, a hearth, four postholes and a sunken feature building were assessed through flotation producing results broadly similar to those from Anglian contexts. The definition of F177F as a sunken feature building could not be confirmed or refuted through the environmental evidence as, while F177F C1350F contained mineralised material, none of the contexts from associated rubbish pits seemed to contain much evidence for faeces, either in the form of fishbone (with the exception of a little from F125F) or concretions.

Uncharred plant remains were noted from twelve deposits; in a number of these, however, this material appeared to be modern in nature (F129F C1318F, F171F C1325F, F184F C1346F). Charred remains were identified in the majority of Period 4 deposits; burnt grains and seeds were identified in F125F C1240F and F184F C1346F, in addition to a single charred cotyledon of a probably field bean from F161F, and a large quantity of cereal grain from F216F, primarily comprising barley, but also oat, wheat and possible weed seeds; charred nutshell was noted as rare in posthole F180F. Several features contained evidence for fuel materials, including hearth F183F and pit F125F, the latter suggesting the burning of peat. Animal bone was noted from almost all Period 4 samples. The presence of a concentration of amphibian bone in F125F would again imply that this feature had been left open to accumulate sediment more slowly. Pit F216 C1456 contained a concentration of burnt clay fragments, similar to the shattered loomweights recovered from Blue Bridge Lane. This deposit was also significant in containing a large amount of grain (mostly barley) and weed seeds. It would appear that the nature of activity in the Anglo-Scandinavian period as indicated by the environmental material was slightly different to that of the Anglian, with little evidence for processing of cereals/ thatching materials and even less for faeces. It is possible that night soiling as well as removal of vegetable matter may have taken place, but it is also possible that the organisation of the site may have meant that cesspits were not contacted during the excavated area. This corresponds with the finds noted in the features at Blue Bridge Lane above, where there was a similar lack of evidence of organic material from this period.

Period 5

At Blue Bridge lane, a total of six contexts from six features were sampled, comprising five pits (F216B, F272B, F214B, F215B, F242B) and a posthole (F163B). No Period 5 features were sampled at Fishergate House. Food remains were represented by animal bone in all five features, and included identifiable fragments of fish, cattle and caprovid bones; mussel was noted as rare from F215F. The presence of amphibian bones in F216B and F272B may indicate that these features were open for some time.

Building materials were generally limited; CBM was noted as rare from F216B and F242B, and occasional in F163B. Single pieces of glass were recovered from F216B and F272B. Hammerscale and slag were noted in most of the features, although these were only small quantities.

Period 6

A total of twenty-seven contexts from eighteen features of Period 6 date were sampled from Blue Bridge Lane. These represented nine pits, six postholes, a ditch, and two scoops. Again, evidence for non-organic building materials was limited, although mortar was very common in lime pit F4B C1041B. Food remains were limited to a small amount of bone (only being common in scoop F251B C1561B and pit F252B C157B1), while scoop backfill F426B C1791B contained an unusually high amount of slag and hammerscale, although there was no corresponding concentration of charcoal.

Preservation of organic matter remained poor, and while charred grain (including barley) and seeds were observed within the light fractions of eight deposits (all but one from pits), these were never particularly abundant. There was an overall increase in the amount of CBM, although mortar was still present more rarely. Animal bone was present, mostly occasionally, in almost all contexts, although common only in a handful of pit fills and backfills. Again, a generally low level of slag and hammerscale was present in most contexts and charcoal was never common.

At Fishergate House, a single context was sampled, from ditch F284F. The presence of pottery in particular was noticeable, including a fragment of Samian; charcoal bone and hammerscale were all present, and a single iron object and a fossil were also recovered.

Period 7 14th Century

A total of 50 contexts allocated to Period 7 were sampled from Blue Bridge Lane; these are discussed within the subdivisions of Period 7A, 7B and 7C. As no such division has been undertaken at Fishergate House, the two Period 7 samples are discussed beforehand.

These two contexts, from the boundary ditches (F263F, F282F) both produced moderate quantities of charred and uncharred material. These deposits exhibited a heterogeneous nature; CBM, hammerscale, mortar, charcoal, bones and pottery were noted as occasional or rare in both samples.

Period 7A

A total of twelve contexts from eight features were examined from Period 7A, all of which have been identified as pits. No uncharred material was recovered, while charred material was identified in contexts from all features. More specifically, burnt grain was identified in two samples (F223B C1489B and F254B C1548B), burnt seed was noted from three contexts (F218N C1409B, F435B C1945B and F397B C1884B) and a single fragment of hazelnut shell was identified in F245B. Animal bone, including bird, fish and mammal, occurred in all but one of the contexts, and was noted as frequent in pit F223B C1489B. F397B C1884B was identified as containing faecal matter, on the grounds of a greenish tinge, and low non-organic inclusions.

Some industrial evidence was noted; charcoal and hammerscale were identified in F183B, F208B, F218B, F223B, F239B, F254B, F397B and F435B, although noted as rare in some cases. Slag was identified in nine contexts, ferrous objects were recovered from F208B (nails), F223B, F239B (nails), and lead was identified in two cases (F223B and F218B). Glass was recovered from two contexts.

Period 7B

From Blue Bridge Lane, samples were derived from thirty-three contexts from twelve features of Period 7B date. The sampled features included seven pits, a kiln, a clay storage pit, one scoop, and two postholes. These contexts provided valuable evidence regarding the plant matter that would have been consumed on the site.

No uncharred material was recovered, although charred grain and seeds were present in a further twenty-two contexts and single mineralised seed was observed in pit F333B C1736B. Of particular interest were the mineralised plum stone from pit F211B C1523B and the charred evidence for lentil from kiln F58B fill C1369B. Detailed assessment identified elder seeds (F211B C1523B), grape seeds, and uncharred seeds of blackberry and henbane (F211B C1524B). While these latter seeds may have been intrusive, they need not have been; the same deposit contained evidence of faecal material in the form of crushed fish bone and mineralised woodlouse. It is possible that the pit, once falling out of use, could have been backfilled rapidly with rubbish.

As in previous phases, slag and hammerscale were present in virtually all deposits, but generally only rarely. Against this background it was recorded as common in pit F150B C1312B and C1333B and in pit F211B C1524B and occasional in nine other contexts, mostly from pits but also from post holes, and ditch F208B. The amount of CBM in flotation samples seemed no greater than in previous phases, although F198B contained deposits with greater concentrations. Small quantities of mortar were present in few contexts, two of which were from kiln F58B. Glass was present in twelve contexts, iron in twenty, copper in eight and lead in one. Bone was present in most contexts with concentrations most notable in pit F150B.

Period 7C

Three contexts from two pits (F261B and F401B) were sampled at Blue Bridge Lane. C1604B, derived from pit F261B, and was particularly mixed, containing animal bone, charcoal, hammerscale, while iron, copper wire, mussel shell and carbonised grain were noted as rare. Contexts from F401B were less varied containing only hammerscale and animal bone.

Period 8

At Blue Bridge Lane, samples deriving from Period 8 are discussed within their sub-phases of Periods 8A and B. A single 10 litre sample was taken from a Period 8 pit at Fishergate House, which produced evidence for animal bone, also fragments of human teeth and bone, which will have derived from disturbed graves. CBM and hammerscale were noted as rare.

Period 8A

Eight samples derived from Period 8A, from a pit (F108B), a ditch (F219B) and from the fills of possible levelling cut F352B. Uncharred organics (other than modern rootlets) were not present. All samples produced animal bone; notably, fish bone was identified within all contexts, although recorded as rare in many cases.

Each sample contained rare components of slag, hammerscale or iron, and copper alloy was noted from one sample (F219B C1429B), while CBM and pottery seems to have occurred more frequently (F109B, F219B, F352B), possibly deriving from buildings and occupation in the vicinity.

Period 8B

A total of twenty-six contexts was sampled from Period 8B, deriving from fifteen features, of which eleven were pits, one was a posthole and three were hearths.

Uncharred material was noted in two contexts from pits (F125B C1577B and F126B C1590B), in the form of uncharred seeds. Carbonised material was noted in the majority of contexts, and charred seeds and grains in particular were noted thirteen contexts from eight features, predominately from pits, but also from hearth F178B C1292B. This latter example was identified as comprising grape seeds, which were also noted in F242B C1528B. Burnt nutshell was identified in two contexts from pits, F253B C1569B and F310B C1684B.

Animal bone was present in all but two of the samples, though noted only as rare in eleven of these samples. In the remainder, however, animal bone, and particularly fish bone, appears to have been more common. Contexts from pits F77B, F125B, F126B, F242B were noted to have high quantities of fish bone; F126B C1580B consisted almost entirely of fish bone, and in this context and F126B C1590B herring in particular was identified. Oyster shells were also noted in F242B C1528B, and F334B C1740B.

Non-organic building materials were identified in almost all contexts. Just three samples did not contain CBM, and in the remainder CBM was noted as occasional or common. Burnt daub was noted in F329B C1729B, and mortar or plaster were observed in a further six contexts. Fragments of limestone, which may have derived from building material, was identified in one context. A further eight contexts produced small glass fragments.

Pottery was noted from eighteen contexts, while hammerscale, charcoal, slag and vitrified fuel ash, in varying combinations, were noted in the majority of contexts, generally noted as rare, but seen to occur more occasionally in the hearth deposits. Iron objects were recovered from sixteen contexts, copper alloy artefacts from eight contexts (including fragments of wire, a pin and an earscoop), and lead from one context.

Discussion

Overall, the sampling strategy implemented at Blue Bridge Lane has been successful at maximising the efficiency of the recovery of dating and environmental evidence, as well as the collection of a host of smaller artefacts and products pertaining to various activities on the site. This has left a large number of residues which, having been sorted, contain little more than gravel and fine fragments of CBM, charcoal, fragmentary unidentifiable bone and concretions likely to be of faecal origin. As such, it does not seem to be of any great value to retain this vast quantity of inert material. While further analysis of the faecal concretions may prove valuable in the identification of worm eggs, detailed assessment indicated that in the majority of cases the results are likely to be disappointing. There are also a large number of washovers from Siraf flotation which are currently kept wet. It would be worth drying out these (for greater ease of storage) and, although they are likely to contain burnt grain, seeds and fishbone, actual further work on them is only likely to be valuable within the framework of a specific research objective, for example, tracing the progressive development of pit fills as a means of reconstructing site formation processes; otherwise, detailed assessment indicates that we can expect to accumulate more similar data.

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apc > monographs > blue bridge lane & fishergate house > artefacts & environmental > environmental evidence