Perry Oaks Sediment Investigation

PERRYOAKS SEDIMENT INVESTIGATION

by Martin R. Bates

Introduction This report summarises the findings from the investigation of selected sections from the Bed B and Bed C areas of the WPR98 excavation taken during the fieldwork phase in 1999. The work undertaken by the author included field visits throughout the period of excavation from April to November 1999. Field visits involved recording of key representative profiles through major identified ditches1 and the sampling (on a context basis) of the major units present in individual ditches. This work aimed to ascertain whether: •

Individual contexts identified by field staff exhibited different sedimentological signatures thereby cross-checking the validity of the contextual sub-division.

•

Consistent patterns of infilling of the ditches could be identified across space (and through time) within Beds B and C.

•

The patterns of infilling could be interpreted in terms of changing processes of infilling.

•

Further investigation of sampled contexts would provide additional data to clarify issues arising as a result of the present investigation.

Ultimately the work was designed as an attempt to determine whether changing patterns of landscape use may have been reflected in the fills of individual ditches (conventionally such patterns should be recorded in the site stratigraphy across the site however, because of the large scale stripping of the stratigraphy prior to sewage farm construction this evidence was not available for study).

Methodology Sections through ditches were identified for investigation following consultation with field staff responsible for individual excavation areas. Features and sections were selected for detailed investigation if: •

1

The profiles were thought to represent typical fills (based on repeated observations through a number of intersections) through an identified feature.

Only ditches were selected for study; it was considered that ditches would act as a local to regional trap for sediments deriving both from within and beyond the ditch. Pits were omitted from the study due to their restricted nature and the complex patterns of infilling expected within a closed system such as a pit.

•

The profiles derived from features representing a sample of features from across the site and of different (preliminary) ages from the Neolithic to Iron Ages.

Once features had been selected for investigation the drawn section was used to identify the contexts present in the profile and descriptions of individual contexts were undertaken by the author. Following description bulk samples were taken of the major contexts for detailed analysis. The recovered bulk sample sizes were intended to reflect the nature of the contained material (i.e. in order to produce an accurate estimation of the particle size distribution of an individual context larger samples were required from coarser gravel samples than from finer grained deposits in order to be assured that all grades of particle would be represented in the recovered sample). A full list of all sections, contexts and sampling information is presented in Table 1. Samples taken were processed in the following fashion: •

Bulk samples were weighed and wet sieved through a nest of sieves with sieve mesh sizes of 64mm, 32mm, 16mm, 8mm, 4mm and 2mm. The residues retained on each mesh was weighed. Subtraction of the total weights retained on all meshes from the original bulk weight allowed the less than 2mm fraction to be determined. Percentage values for each fraction were then calculated.

•

In order to calculate the sand (2mm – 0.062mm) and clay-silt (<0.062mm) fractions a sub-sample from each bulk sample was sieved in order to determine the >2mm fraction, 2mm – 0.062mm fraction and the <0.062mm fraction. The >2mm fraction was then calibrated against the >2mm fraction from the coarse sieving exercise and the percentages of sand and clay-silt calculated.

•

Additionally the size of the largest clast in the coarse sieved samples and the mean particle size of the 10 largest clasts were determined using measuring callipers for each sample.

The results of this investigation (Table 2) are shown in Figures 2 to 26. The results are presented on a feature by feature basis and illustrate: •

The particle size distribution of individual samples investigated presented as a series of percentage bar graphs (tabulated data on percentages in each grade class are shown).

•

The gravel to fine ratio (>2mm:<2mm fractions) for all samples investigated.

•

The clasts size statistics for all measured samples (mean (10) largest clasts and the maximum clast size).

•

A stacked bar graph comparing the particle size distributions for each sample investigated set out in stratigraphic order from base to top of profile (where possible).

In addition to the work on the particle size distributions a limited investigation of the organic content and the magnetic susceptibility properties of a number of features

from Bed B have been undertaken. Determination of organic content was undertaken by combustion of air dried samples at 550°C for 2 hours. Mass specific magnetic susceptibility determinations were made on air-dried sub-samples using a Bartington MS2 system.

MODELS AND ASSUMPTIONS In order to understand the information generated by this study and to interpret the results it is necessary to consider the ways in which the ditch features would infill. A substantial body of data is available on the processes responsible for feature infilling (e.g. Bell et al. 1996). An exhaustive survey of the relevant literature has not been conducted on these aspects as part of this study however from this body of literature it is possible to arrive at some basic conclusions regarding feature infill. For example, for a feature infilling from the decay of the ditch profile and where no re-cutting of the ditch profile is in evidence and where no additional material is derived from bank collapse/deliberate backfilling it is likely that: •

Bedrock substrate will be a primary determinant regarding the nature of the fills, i.e. a fill may be derived directly from a given bedrock, e.g. a fine grained bedrock substrate can only provide fine grained fills.

•

Profiles through wider, shallower ditches will stabilise rapidly thereby reducing the slope angles across which potential infilling particles may move and decreasing energy levels required to transport larger particles. This will result in a typically finer grained fill (in respect to narrower ditches).

•

Narrow, deep ditches will be subject to profile decay over longer timespans than wider ditches and are likely to contain coarser elements (bedrock substrate permitting) than wider ditches.

Figure 1 illustrates these relationships. Ultimately if these assumptions are valid individual features infilling through natural processes should exhibit a general fining upwards in particle size. This would reflect the initial infilling of the feature resulting from collapse of feature edges (if bedrock sediments were coarse the early fills would reflect this) and later filling from fines derived from washout of material from feature edge locations but where the larger particles remain in situ within the parent body due to the absence of sufficient transport mediums to move them. If the assumptions outlined above are valid then deviation from the observed pattern may indicate derivation of fill deposits through other mechanisms and processes. These may be: •

Decay of adjacent bank material.

•

Deliberate backfilling of features by human activity.

•

The presence of an unknown sources material for sediment adjacent to the feature.

•

Stripping of the adjacent soil cover to expose bedrock surfaces to erosion.

Coarse bedrock sediment Sediment coarseness

Fine bedrock sediment

Ditch width

RESULTS

Figure 1. Theoretical relationships between ditch width and fill sediment coarseness for two types of bedrock sediment. For coarse bedrock sediment fills should be coarser within narrow features than wider features. For fine bedrock sediment fills fill particle size distributions will be similar in narrow and wide features.

Bed B. Cursus ditches (Figures 2 – 8). Four intersections through the cursus ditches were examined: 149009 – cursus ditch west (southern end) (Figure 2) 149006 – cursus ditch west (northern end) (Figure 3) 134022 – cursus ditch east (southern end) (Figure 4) 155165 – cursus ditch east (central area) (Figure 5) 153023 – cursus ditch east (northern end) (Figure 6) The following points are revealed from a study of the graphical results: •

Particle size distributions from the western cursus ditch (Figures 2 and 3) show that there is a small, but significant increase in the sand content of the sediments up-profile. Within the northern intersection (149006) (Figure 3) the bedrock particle size distribution is similar to that within the fill deposits.

•

Mass-specific magnetic susceptibility determinations (Figure 7) throughout the profile from 149006 (western cursus ditch) show little up-profile change, this is mirrored in the organic content of the fills (Figure 7).

•

There is a significant up-profile decrease in particle size in the eastern ditch (Figures 4 and 6). This is seen clearly in the gravel/fine ratio and in the summarised results where an increase in sand content (at the expense of gravel) occurs up-profile.

•

Mass specific magnetic susceptibility results from 153023 (Figure 8) increase upprofile to a depth of 9.5cm where values stabilise. The organic content of the feature shows a similar pattern to a depth of 11.5cm before values begin to decline upwards.

•

Information from 155165 (Figure 5) indicates that the presence of a coarse middle fill from this sequence suggest a different pattern of infilling dominated in this area of the cursus ditch.

This information suggests that: •

The infill of the western ditch could have been derived from degradation of the surrounding bedrock edges with only minimal alteration of the sediment during infilling. However the increase in sand content seen in 149006 (Figure 3) may indicate an influx of sand from other sources (possibly a fluvial input?).

•

The magnetic susceptibility determinations from the western ditch fills indicate little evidence for trends within results that perhaps indicates gradual, slow and continual accumulation of sediment.

•

Infilling of the eastern ditch suggests that progressive infilling of the feature resulted from a winnowing out of the finer elements of the bedrock, and their subsequent deposition as ditch fills, and a decrease in gravel content up-profile (Figures 4 and 6). Infilling of the central section of the eastern ditch (155165) suggests differing patterns of infilling dominated here.

•

The peaks of values for both magnetic susceptibility and organic content within the eastern ditch (Figures 7 and 8) suggest variation in the nature of patterns of sedimentation and the possibility that a phase of stability exists within the middle part of the profile (thus implying a period of ditch fill stability and cessation of infilling – this may be reflected in the age distribution of finds from the uppermost fills being considerably later than the assumed age for the early fills).

Bed B. Diagonal ditch (Figures 9 – 12). Two intersects were examined from the diagonal ditch present to the east of the cursus monument: 132003 (Figure 9)

153003 (Figure 10) The following points are revealed from a study of the graphical results: •

In both profiles a decrease in the particle size distributions of contexts up-profile was noted.

•

Data from 132003 (Figure 9) indicates that the sand and clay-silt fractions both increase significantly up-profile.

•

Gravel/fine ratios decrease up-profile.

•

Mass specific magnetic susceptibility values show a peak in values towards the top of the sequence in 132003 (Figure 11).

•

Organic levels are typically low but exhibit some variations in the fill of 132003 (Figure 12).

This information suggests that: •

This pattern is similar to that seen in certain parts of the cursus ditch fills (Figures 4 and 6) suggesting winnowing out of finer elements in the surrounding bedrock and their deposition within the ditch fills occurred progressively up-profile during ditch infilling

•

The infilling elements within the ditch fills may all be derived from the surrounding bedrock profiles.

•

Mass specific susceptibility values may indicate the presence of a buried soil or weathering horizon towards the top of the fill in 132003 (Figure 11).

Bed B. Ditches in the vicinity of the ring ditch (Figures 13 – 15). Three intersects were examined from ditches in the vicinity of the ring ditch feature: 150003 (Figure 13) 138007 (Figure 14) 138003 (Figure 15) The following points are revealed from a study of the graphical results: •

Fills in all intersections rest of bedrock with a major coarse gravel component.

•

Particle size distributions from the fills indicate decreasing particle size up-profile but where the uppermost fills exhibiting a slightly coarser component than the penultimate fills (i.e. the fills possess a coarse ‘tail’).

•

This coarse tail within the fills is clearly illustrated by the upturned tail exhibited in the gravel/fine ratio from all intersects (Figures 13 – 15).

This information suggests that: •

Progressive winnowing of finer elements within the bedrock took place during the deposition of the majority of the ditch fills.

•

A sudden influx of coarser sediment occurred within the uppermost fills of all intersections.

This pattern of infilling does not reflect patterns observed in any ditches to the west towards the cursus monument and does not match the model set out above. This data suggests that differing infill processes may have been responsible for the infilling of the upper parts of these features.

Bed B North-south ditches at eastern end of Bed B. (Figures 16 – 20). Three intersects were examined from the ditches present towards the eastern end of Bed B: 147007 (Figure 16) 146014 (Figure 17) 148006 (Figure 18) The following points are revealed from a study of the graphical results: •

A general trend to fining upwards is noted in the fills of the three profiles sampled (Figures 16 – 18). A coarser tail is noted in Figure 18 to the fills of 148006.

•

Fill units retain a typical coarse gravel component throughout the fill sequences in all three profiles examined (this contrasts with sediments for example in any of the features to the west of this part of Bed B).

•

Magnetic susceptibility determinations through 148014 (Figure 19) exhibit little evidence of trends in values from top to base of profile.

•

Organic content values fluctuate, exhibiting a general upwards increase in values but with a major peak in values at c.17cm depth (Figure 20).

This information suggests that: •

The infilling of the ditches are likely to have been derived from the local bedrock but winnowing of fines from the adjacent bedrock and the subsequent concentration within the fills does not appear to be as important a processes as that seen in other fills to the west (e.g. within the diagonal ditch fill sequences).

•

A sudden influx of coarser sediment occurred within the uppermost fill of 148006 (Figure 18). This is consistent with the pattern seen in ditches surrounding the ring ditch complex.

•

Infill rates of features may have been constant (see Figure 19) with minimal variation in fill processes up-profile.

Bed C (Figures 21 – 24). Four intersects were examined from the Bed C area: 125137 (Figure 21) 138038 (Figure 22) 166025 (Figure 23) 125144 (Figure 24) The following points are revealed from a study of the graphical results: •

Bedrock particle size distribution is typically coarse gravel (Figures 21, 22 and 23).

•

Fining upwards trends are seen in all profiles sampled (Figures 21 – 24) but a coarse tails to the sediments is only seen in feature 125144 (Figure 24).

This information suggests that: •

Progressive winnowing of the sediments in the bedrock surrounding cuts occurs and this material is concentrated in fill units exhibiting concentration of finer elements up profile. This is similar to trends seen in features towards the western end of Bed B.

•

All particle size distributions of fill deposits may be generated from the bedrock sediments however, in order to generate the quantities of fine grained fills present it is necessary to consider what has happened to the coarser elements clearly present in the natural bedrock sediments.

CONCLUSIONS The evidence presented in this study indicates that a number of conclusions can be drawn: •

Bedrock particle size distributions vary across the site and range from coarse gravels to sands.

•

Fining upwards processes can be seen to dominate ditch fill profiles throughout most sequences (this is predicted by the model outlined above). This indicates that many of the features examined appear to have infilled naturally.

•

Although fining upwards processes dominate, some features contain fills that are considerably coarser than others (e.g. ditches at the eastern end of Bed B (Figures 16 – 18).

•

In some cases coarse tails to the infill sequences are reported, e.g. from features surrounding the ring ditch complex (Figures 13 – 15), ditches in the eastern part of Bed B (Figure 18) and a single profile from Bed C (Figure 24).

•

Loss-on-ignition and magnetic susceptibility data indicate that infilling processes within different features may have varied.

In order to illustrate the nature of the results two graphs are presented (Figures 25 and 26) which attempt to summarise the findings. Figure 1 illustrated the potential relationships between feature width and sediment coarseness and Figure 25 shows the information generated in this study illustrating the relationship between width/depth ratios and gravel/fine ratios (uppermost fills) from selected samples. This evidence shows that: •

The wide, shallow cursus ditches are filled with fine-grained sediments and therefore conform to the proposed model presented above.

•

Ditches towards the eastern end of Bed B exhibit coarse fills resting within narrow features, in some cases the gravel fills may appear very coarse.

•

Ditches surrounding the ring ditch complex exhibit values between the cursus values and those from the eastern part of Bed B showing intermediate values in ditch width and sediment grain size.

•

Feature fills from Bed C indicate the presence of narrow ditches containing typically fine-grained fills. This does not fit with the proposed model.

The feature fills from Bed B conform to the pattern of the model set out in Figure 24 for natural infilling of the features derived from the sediments surrounding the ditch profile cut. However, the coarse elements noted in some of the upper fills from the features surrounding the ring ditch complex and the eastern ditches in Bed B suggest an input of coarser sediments late in the infill history of the features. Two sources of material may exist for this fill element: •

Decay of adjacent bank or

•

Erosion of the surrounding landsurface following clearance.

At present it is not possible to be certain which of these hypotheses is correct. If bank decay is responsible then it must be assumed that decay of banks was not an important factor during the infilling of features towards the western end of Bed B.

The finer grained fills of the features within Bed C may relate to either differing processes of infilling or the fact that a brickearth spread existed across much of this part of the site. This brickearth spread would have contributed most of the fill to these features. It is clear from the results from Bed C that while general trends upprofile in these features indicate fining upwards sequences decay of the surrounding ditch edges does not appear to have played an important role in ditch fill generation (this contrasts with the patterns in the fills from the eastern edge of Bed B).

The results of the investigation do appear to indicate that: •

The recognition of the major context units during field excavation is verified by the results of this investigation.

•

Consistent patterns of infilling of the ditches could be identified across space.

•

Infill patterns appear to be dominated by factors associated with the nature of the underlying bedrock and the natural progression of abandoned features. Some evidence from the ring ditch complex and the eastern end of Bed B suggests other processes such as bank decay or, probably, landscape degradation may have been contributing to ditch fill sediments.

The results of this investigation suggest that further work could be contemplated: •

Additional magnetic susceptibility determinations from key contexts sampled to cross-check results presented here.

•

Geochemistry/mineralogy of cursus ditch fills and Bed C features to ascertain whether fills are derived from alluvial sources/brickearth sources.

REFERENCES Bell, M., Fowler, P.J. and Hillson, S.W. 1996 The experimental earthwork project, 1960 – 1992. CAB Research Report 100. Council for British Archaeology: York.

Table 1. Features, context and laboratory analysis statistics. Feature No.

Context No.

Type

Particle size

Large clasts

147007

147004 147005 147006 Natural gravel

N/S ditch in east of B

Yes

Yes

146014

146011 Natural gravel

N/S ditch in east of B

Yes

Yes

148006

148003 148004 148005 Natural gravel

N/S ditch in east of B

Yes

Yes

138007

138008 138017 Natural gravel

Ring area

ditch

Yes

Yes

150003

150004 150005 (upper) 150005 Natural gravel

Ring area

ditch

Yes

Yes

149009

149010 149011

Cursus ditch

Yes

Yes

149006

149007 149008 Natural gravel

Cursus ditch

Yes

Yes

134022

134025 134024 Natural gravel

Cursus ditch

Yes

Yes

153023

153025 153024 Natural gravel

Cursus ditch

Yes

Yes

153003

153005 153004

Diagonal ditch

Yes

Yes

132003

132004 132007 Natural gravel

Diagonal ditch

Yes

Yes

125144

125148 125146 125145

Bed C

Yes

Yes

155165

155166 155167 Natural gravel

Cursus ditch

Yes

Yes

LOI

M.Sus.

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Table 1 (cont.). Features, context and laboratory analysis statistics. 138038

138039 138040 138041 138043 Natural gravel

Bed C

Yes

Yes

166025

166023 166024 166031 166028 166030 Natural gravel

Bed C

Yes

Yes

125137

125141 125140 125139 125138 Natural gravel

Bed C

Yes

Yes

138003

138004 138005 138006 Natural gravel

Ring area

Yes

Yes

ditch

Figure 2 Feature No. Contexts/age ascription

149009 149010 149011

Particle size distribution, 149010 60 50 %

40 30 20 10 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

0.4054 5.2703 5.6216 6.0811 2.027 50.964 29.63 Particle size class

Particle size distribution, 149011 50 40 %

30 20 10 0 %>64 %>32 %>16 %>8 0

Series1

3.3333 8.5185

10

%>4

%>2

%>0. %<0. 062 062

5.1852 2.2222 30.041 40.7

Particle size class

0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0

Clast size statistics 90 80 70 60 m 50 m 40 30 20 10 0

0.413612565

0.240778001

149010

Mean (10) largest Maximum clast size

149010

149011

149011 Context

Context

Summarise particle size data, 149009 >64 >32

149010

>16 Context

G:F

Gravel:fine ratio, 149009

>8 >4 >2 149011

>0.062 <0.062 0%

20%

40%

60% %

80%

100%

Nat. l

Figure 3 Feature No. Contexts/age ascription

149006 149007 149008 Natural gravel

Particle size distribution, 149007 80

%

60 40 20 0 %>64 %>32 %>16 %>8 Series1

0

0

%>4

%>2

%>0. %<0. 062 062

0

73.237 17.902

2.5316 3.7975 2.5316 Particle size class

Particle size distribution,149008

Particle size distribution, natural gravel

80 50 40

40 %

30 20

20

10 0 %>64 %>32 %>16 %>8 Series1

0

0

%>4

%>2

%>0. %<0. 062 062

0 %>64 %>32 %>16 %>8

%>4

%>2

3.0651 0.3831 3.4483 1.5326 59.937 31.634 Series1

Particle size class

0

%>0. %<0. 062 062

0.2041 2.0408 2.0408 3.4014 0.6803 47.344 44.289 Particle size class

Gravel: fine ratio, 149006 0.098

Clast size statistics

0.097222222

70

0.096

60

G: 0.094 F 0.092

50

0.092050209

0.09

0.091314031

mm

%

60

Mean (10) largest

40 Maximum clast size

30 20

0.088

10

149007

149008 Context

Nat.

0 149007

149008 Context

Nat. grav.

Figure 4 Feature No. Contexts/age ascription

134022 134025 134024 Natural gravel

Particle size distribution, 134025 80

%

60 40 20 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

1.4058 5.1546 7.9663 10.622 1.8119 60.66 12.38 Particle size class

Particle size distribution, natural gravel Particle size distribution, 134024 40 50 30 %

40

20

%

30 20

10

10

0

0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>64 %>32 %>16 %>8

%>0. %<0. 062 062

Series1

0

19.205

11.579 19.079 14.079 9.2105 2.3684 38.442 5.2421

23

%>4

%>2

%>0. %<0. 062 062

16.386 9.1136 2.1591 30.136 3.2289 Particle size class

Particle size class

Clast size statistics

Gravel:fine ratio, 134022 100

2.5

m m

1.5 1.289156627

Mean (10) largest

60

Maximum clast size

40

1

20 0.5

0.369118905

0

0

134025 134025

134024

Nat. grav.

134024 Context

Context

Summarised particle size data, 134022 >64 134025

>32 >16

Context

G:F

80

2.093903566

2

>8

134024

>4 >2 >0.062

Nat. grav.

<0.062 0%

20%

40%

60% %

80%

100%

Nat. grav.

Figure 5 Feature No. Contexts/age ascription

155165 155166 155167 Natural gravel

80 70 60 50 40 30 20 10 0

%

<0 .0 62

>2 >0 .0 62 %

%

%

>4

>8 %

%

%

%

>1 6

>3 2

Series1

>6 4

%

Particle size distribution, 155167

Particle size class

Particle size distribution, 155166 60 50 %

40 30 20 10 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

3.4821 16.964 16.964 7.8571 6.25 48.482 42.778 Particle size class

Particle size distribution, natural gravel 100 80 %

60 40 20 0 %>64 %>32 %>16 %>8 Series1

0

0

6

5.8333

%>4 6

%>2

%>0. %<0. 062 062

1.5833 80.583 65.152

Particle size class

Gravel:fine ratio, 155165

Clast size statistics

1.2

0.8 G: F 0.6 0.445347787

0.4 0.2

0.240951396

0 155067

155166 Context

Nat.grav.

mm

1.062615101

1

90 80 70 60 50 40 30 20 10 0

Mean (10) largest Maximum clast size

155067

155166 Context

Nat.grav.

Figure 6 Feature No. Contexts/age ascription

153023 153026 153024 Natural gravel

Particle size distribution, 153026 50 40 %

30 20 10 0 %>64 %>32 %>16 %>8 0

Series1

%>4

%>2

%>0. %<0. 062 062

0.7463 6.7164 8.209 5.2239 0.597 35.574 42.934 Particle size class

Particle size distribution, 153024

particle size distribution, natural gravel

50

30

30

25

%

40

20 %

20

15

10

10

0 %>64 %>32 %>16 %>8 0

7.3333 17.333

12

8

%>2

5 0 %>64 %>32 %>16 %>8

0.6667 38.842 15.825

Particle size class

0

Series1

%>4

%>2

%>0. %<0. 062 062

14.141 26.965 18.972 14.756 3.3377 16.79 5.037 Particle size class

Gravel:fine ratio, 153023

Clast size statistics 140

4 3.581488934

3.5

120

3

100 mm

2.5 2 1.5 1 0.5 0

Mean (10) largest

80 Maximum clast size

60 40

0.829268293

20

0.273764259 153026

0 153024

153026

Nat. grav.

153024

Nat. grav.

Context

Context

Summarised particle size data, 153023 >64 153026

>32 >16

Context

G:F

Series1

%>4

%>0. %<0. 062 062

>8

153024

>4 >2 >0.062

Nat. grav.

<0.062 0%

20%

40%

60% %

80%

100%

Figure 7: Mass specific magnetic susceptibility results χlf(10-6m3kg-1) from cursus ditch fills

149006

153023

2. 5

1.5

8. 5

7.5

1 4. 5

13.5 22. 5

19.5

28. 5 0

5

10

15

0

Western ditch

5

10 m a g . S u s.

M a g . Su s .

Eastern ditch

15

20

Figure 8. Organic content within cursus ditches

Loi Results Cursus ditch west Depth

2.50 10.50 20.50 28.50 0

5

10

15

20

25

%

Loi results Cursus ditch east Depth

3.50 11.50 19.50 0

2

4

6 %

8

10

12

Figure 9 Feature No. Contexts/age ascription

132003 132004 133007 Natural gravel Particle size distribution, 132004 120 100 %

80 60 40 20 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

0.1572 0.7862 1.5723 0.9434 0.1572 96.384 64.735 Particle size class

Particle size distribution, 132007

Particle size distribution, natural gravel 60

40

50 %

40

30 %

30 20

20

10

10

0 %>64 %>32 %>16 %>8

%>4

%>0. %<0. 062 062

%>2

0 %>64 %>32 %>16 %>8

Series1 4.9116 4.9116 15.619 9.8232 8.8409 0.9823 54.912 18.304 Particle size class

0

Series1

%>4

%>2

%>0. %<0. 062 062

2.2014 10.295 13.241 22.046 16.899 35.319 13.913 Particle size class

Gravel:fine ratio, 132003

1.831347388

120 100

mm

80 0.821109123

Mean (10) largest

60

Maximum clast size

40 20

0.037520392 132004

132007

0

Nat. grav.

132004

Context

132007 Context

Summarised particle size data, 132003 >64 132004

>32 >16

Context

G:F

Clast size statistics 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0

>8

132007

>4 >2 >0.062

Nat. grav.

<0.062 0%

20%

40%

60% %

80%

100%

Nat. grav.

Figure 10 Feature No. Contexts/age ascription

153003 153005 153004

Particle size distribution, 153005 100 80 %

60 40 20 0 %>64 %>32 %>16 %>8 0

Series1

1.5833 5.5833

7

%>4

%>2

%>0. %<0. 062 062

6.875 1.4583 77.5 43.509

Particle size class

Particle size distribution, 153004 50 40 %

30 20 10 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

6.1321 20.126 15.881 13.994 3.7736 40.094 15.33 Particle size class

Gravel:fine ratio, 153003 1.6

Clast size statistics 1.494117647

1.4 1.2

mm

G:F

1 0.8 0.6 0.4 0.2

0.290322581

0 153005

153004 Context

90 80 70 60 50 40 30 20 10 0

Mean (10) largest Maximum clast size

153005

153004 Context

Figure 11. Mass specific magnetic susceptibility results χlf(10-6m3kg-1) from feature 132003

132003

5.5 13.5 19.5 0

5

10 M a g . S u s.

Diagonal ditch

15

20

Figure 12. Organic content within diagonal Bronze Age ditch

Depth

Loi Results Bronze Age diagonal ditch 7.50 19.50 6.5

7

7.5 %

8

8.5

Figure 13 Feature No. Contexts/age ascription

150003 150005 (upper) 150005 150004 Natural gravel

Particle sie distribution, 150005 (upper)

Particle size distribution, 150004

50

40

40 30 %

%

30 20

20

10

10

0 %>64 %>32 %>16 %>8 0

Series1

4

%>4

%>2

0

%>0. %<0. 062 062

%>64 %>32 %>16 %>8

14.053 10.053 3.7368 2.6316 24.412 41.115

0

Series1

Particle size class

%>4

%>2

%>0. %<0. 062 062

6.2857 15.333 8.9524 4.381 3.7143 34.233 27.101 Particle size class

Particle size distribution, natural gravel

Particle size distribution, 150005

30 50

25

40

20

%

%

30

15

20

10

10

5 0

0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>0. %<0. 062 062

%>2

%>64 %>32 %>16 %>8 Series1

6.5294 5.2941 5.0588 3.5882 2.2353 30.482 46.812

0

13.3

Gravel:fine ratio, 150003

9.75

7.4

%>0. %<0. 062 062 26.4

8.8

Clast size statistics

2.5

120

2.090909091

2

100 Mean (10) largest

80 mm

1.5 1

60

Maximum clast size

40

0.630434783

0.526104418

20

0.293759513

0

0 150005 u

150005

150004

150005 u

Nat. grav.

150005

150004

Context

Context

Summarised particle size data, 150003 150005 u >64 Context

G:F

18.3

%>2

Particle size class

Particle size class

0.5

24.85

%>4

>32

150005

>16 >8

150004

>4 >2

Nat. grav.

>0.062 0%

20%

40%

60% %

80%

100%

<0.062

Nat. grav.

Figure 14 Feature No. Contexts/age ascription

138007 138008 138017 Natural gravel

Particle size distribution, 138008 80

%

60 40 20

Particle size distribution, natural gravel

0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

40 30

5.3814 11.079 10.13 6.3311 1.7411 65.337 12.565

%

Particle size class

20 10 0

Particle size distribution, 138017

%>64 %>32 %>16 %>8 Series1

80

0

%>4

%>2

10.717 18.573 16.436 14.299 5.3426 34.632 16.821 Particle size class

%

60 40 20 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

3.4771 8.3449 5.5633 5.5633 6.9541 70.097 36.3 Particle size class

2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0

Clast size statistics 140

1.887477314

120 100 mm

G:F

Gravel:fine ratio, 138007

0.530523256

0.426587302

Mean (10) largest

80 Maximum clast size

60 40 20

138008

138017 Context

Nat. grav.

0 138008

138017

Context

%>0. %<0. 062 062

Nat. grav.

Figure 15 Feature No. Contexts/age ascription

138003 138004 138005 138006 Natural gravel

%

Particle size distribution, 138004

Particle size distribution, 138006

80

50

60

40 30 %

40

20 20

10 0 %>64 %>32 %>16 %>8 0

Series1

%>4

%>2

0

%>0. %<0. 062 062

%>64 %>32 %>16 %>8

1.5341 4.4034 4.6023 7.3864 7.2727 74.801 26.715

%>4

%>2

%>0.0 %<0.0 62 62

Series1 5.0526 10.526 16.842 14.105 8.9474 6.1053 38.421 16.177

Particle size class

Particle size class

Particle size distribution, 138005

Particle size distribution, natural gravel 100

30

%

80

25

60

20 %

40 20

15 10

0 %>64 %>32 %>16 %>8 0

Series1

%>4

%>2

5

%>0. %<0. 062 062

0 %>64 %>32 %>16 %>8

3.4468 3.8298 4.2128 2.2979 1.9574 84.255 35.887 Particle size class

Series1

0

%>4

%>2

%>0. %<0. 062 062

20.938 24.063 14.688 6.25 6.875 27.188 26.121 Particle size class

Gravel:fine ratio, 138003

Clast size statistics

3

140

2.67816092

2.5

120 100 mm

1.602739726

1.5

0.5

Mean (10) largest

80 60

Maximum clast size

40

1

20

0.336878086

0

0

0.186868687

138004

138004

138005

138006

138005

138006

Nat. grav. Context

Context

Summarised particle size data, 138003 138004 >64 Context

G:F

2

>32

138005

>16 >8

138006

>4 >2

Nat. grav.

>0.062 0%

20%

40%

60% %

80%

100%

<0.062

Nat. grav.

Figure 16 Feature No. Contexts/age ascription

147007 147004 147005 147006 Natural gravel Particle size distribution, 147006

Particle size distribution, 147004 40

60 50

30 %

%

40 30

20

20

10

10

0

0 %>64 %>32 %>16 %>8 0

Series1

%>4

%>2

%>0. %<0. 062 062

%>64 %>32 %>16 %>8

6.4363 16.091 12.873 12.873 3.2182 48.509 20.616

Series1

0

%>4

%>2

%>0. %<0. 062 062

9.17 23.314 19.77 11.999 2.1759 33.572 6.7143

Particle size class

Particle size class

Particle size distribution, 147005

Particle size distribution,natural gravel 40

40 %

30

30 %

20 10

10

0 %>64 %>32 %>16 %>8 Series1

20

0

%>4

%>0. %<0. 062 062

%>2

0 %>64 %>32 %>16 %>8

9.1345 24.359 19.368 11.785 2.7629 32.591 4.8886 Particle size class

Series1

0

%>4

%>2

%>0. %<0. 062 062

15.953 36.187 22.568 20.623 4.2802 0.3891 0.0556 Particle size class

Gravel:fine ratio, 147007 300

Clast size statistics 256

250

150

mm

Series1

100 50 0

1.0614634152.0683391 1.978703704 147004

147005

147006

Nat. grav.

100 90 80 70 60 50 40 30 20 10 0

Mean (10) largest Maximum clast size

147004

Context

147005

147006

Context

Summarised particle size data, 147007 147004 >64 Context

G:F

200

>32

147005

>16 >8

147006

>4 >2

Nat. grav.

>0.062 0%

20%

40%

60% %

80%

100%

<0.062

Nat. grav.

Figure 17 Feature No. Contexts/age ascription

146014 146011 Natural gravel

Particle size distribution, 146011 80

%

60 40 20 0

%>64 %>32 %>16 %>8 0

Series1

%>4

%>2 %>0. %<0.

4.758 13.61 7.481 4.069 1.197 68.88 24.73 Particle size class

Particle size distribution, natural gravel 40

%

30 20 10 0 Series1

%>64 %>32 %>16 %>8 0

%>4

%>2 %>0. %<0.

8.113 31.24 16.86 5.611 0.633 37.54 14.77 Particle size class

Clast size statistics

1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0

120 1.663736264

100 80 mm

G:F

Gravel:fine ratio, 146014

Mean (10) largest

60

Maximum clast size

40 0.45178106

20 0

146011

Nat. grav. Context

146011

Nat. grav. Context

Figure 18 Feature No. Contexts/age ascription

148006 148003 148004 148005 Natural gravel

Particle size distribution, 148005 40

Particle size distribution, 148003

30

60

%

50

20

%

40

10

30 20

0

10

%>64 %>32 %>16 %>8

0 %>64 %>32 %>16 %>8 0

Series1

%>4

%>0. %<0. 062 062

%>2

0

Series1

%>4

%>2

%>0. %<0. 062 062

12.029 21.969 16.578 10.408 2.2437 36.772 14.234 Particle size class

13.976 12.786 8.9206 6.066 1.1894 57.062 29.958 Particle size class

Particle size distribution, natural gravel

Particle size distribution, 148004

30

100

25

80

20

%

%

60

15

40

10

20

5 0

0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>0. %<0. 062 062

%>2

%>64 %>32 %>16 %>8

2.1667 8.5556 5.9167 5.2778 1.4722 76.611 46.398

Series1

0

%>4

%>2

%>0. %<0. 062 062

21.085 23.411 14.109 11.783 3.2558 26.357 2.9285

Particle size class

Particle size class

Clast size statistics

Gravel:fine ratio, 148006 140

3

120

2.794117647

100 mm

2.5 1.719491525 1.5

80

Mean (10) largest

60

Mximum clast size

40 20

1 0.752475248 0.5

0 148003 148004 148005

0.305293691

0 148003

148004

148005

Nat. grav.

Context

Context

Sumarised particle size data, 148006 >64

4

>32 Context

G:F

2

>16

3

>8 >4

2

>2 >0.062

1

<0.062 0%

20%

40%

60% %

80%

100%

Nat. grav.

Figure 19. Mass specific magnetic susceptibility results χlf(10-6m3kg-1) from a late Bronze Age ditch

148014

1 .5

5 .5

Depth (cm)

9 .5

1 3 .5

2 3 .5

2 7 .5

3 1 .5 0

2

4

6

M a g .S u s

8

10

Figure 20. Organic content within later Bronze Age ditch

Loi Results LBA ditch Depth

1.50 9.50 23.50 31.50 0

1

2

3 %

4

5

6

Figure 21 Feature No. Contexts/age ascription

125137 125141 125140 125139 125138 Natural gravel

Particle size distribution, 125141

Particle size class, 125138 60

80

50

60

40 %

%

100

40

30 20

20

10

0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

0.7143 4.1429 4.5714 3.2143 5.3571

0

%>0. %<0. 062 062 82

%>64 %>32 %>16 %>8

64.649

0

Series1

Particle size class

%>4

%>0. %<0. 062 062

%>2

10.872 17.949 7.6923 3.5385 3.9487

56

44.8

Particle size class

Particle size distribution, 125140

Particle size distribution, natural gravel

80

30 25

60 %

20 %

40

15 10

20

5 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

0

%>0. %<0. 062 062

%>64 %>32 %>16 %>8

5.1208 8.9372 6.4734 6.4251 2.8019 70.242 4.548

Series1

Particle size class

0

%>4

%>2

%>0. %<0. 062 062

11.053 27.368 20.526 6.8947 6.0526 28.105 27.554 Particle size class

Particle size distribution, 125139

Clast size statistics 80

120 %

60

100

40

Mean (10) largest

mm

80

20

60

Maximum clast size

40 20

%>0. %<0. 062 062

Particle size class

N at .g ra v.

0

4.4286 8.5714 5.3571 3.1429 4.8571 73.643 50.849

12 51 38

0

%>2

12 51 41

Series1

%>4

12 51 39

%>64 %>32 %>16 %>8

12 51 40

0

Context

Gravel:fine ratio, 125137 Summarised particle size data, 125137

3 2.558052434

2.5

125141 >64

125140

1.5 1

0.785714286

0.5 0

0.219512195

Context

G:F

2

>32 >16

125139

>8 125138

0.423658872 0.357904947

>4 >2

Nat.grav.

125141

125140

125139 Context

125138

>0.062

Nat.grav. 0%

20%

40%

60% %

80%

100%

<0.062

Figure 22 Feature No. Contexts/age ascription

138038 138039 138040 138041 138043 Natural gravel

Particle size distribution, 138029

Particle size distribution, 138043 50

80

40

60

30

%

%

100

40

20

20

10

0 %>64 %>32 %>16 %>8 Series1

0

0

%>4

%>2

0

%>0. %<0. 062 062

%>64 %>32 %>16 %>8

0.6173 1.9753 1.7901 5.4321 90.247 52.343

0

Series1

Particle size class

%>4

%>0. %<0. 062 062

%>2

4.9231 23.077 15.385 6.4615 5.0769 45.077 42.525 Particle size class

Particle size distribution, 138040

Particle size distribution, natural gravel 80

30

%

60

25 20 %

40

15

20

10

0 %>64 %>32 %>16 %>8 0

Series1

%>4

5

%>0. %<0. 062 062

%>2

0 %>64 %>32 %>16 %>8

1.2222 16.5 5.7222 3.6444 6.1444 66.767 45.702 Particle size class

0

Series1

%>4

%>2

%>0. %<0. 062 062

13.333 24.444 23.333 14.444 12.222 12.222 10.889 Particle size class

Particle size distribution, 138041

Summarised particle size data, 138038

60

Nat.grav.

40

138043

>64 >32

Context

%

80

20 0 %>64 %>32 %>16 %>8 0

Series1

%>4

>8 >4 >2

138040

%>0. %<0. 062 062

%>2

>16

138041

>0.062 138039

8.8462 11.385 4.6923 1.6154 4.1538 69.308 43.773 Particle size class

<0.062 0%

20%

40%

60%

80%

100%

%

Gravel:fine ratio, 138038 Clast size statistics

8 7.181818182

138041 Context

138043

Nat.grav.

3

0.49775337 0.442841287

138040

at .g ra v.

0.10875513 138039

N

0

1

1

Maximum clast size

13 80 4

1.218430034

0

2

Mean (10) largest

13 80 4

3

9

4

mm

G:F

5

90 80 70 60 50 40 30 20 10 0 13 80 4

6

13 80 3

7

Context

Figure 23 Feature No. Contexts/age ascription

166025 166023 166031 166029 Natural gravel

166024 166028 166030

Particle size distribution, 166023

Particle size distribution, 166028

100

100

80

80

60 %

%

60

40

40

20

20

0 %>64 %>32 %>16 %>8 0

Series1

0

3.68

3.12

%>4

%>2

%>0. %<0. 062 062

3.68

0.88

88.64 58.677

0 %>64 %>32 %>16 %>8 0

Series1

Particle size class

%>4

%>2

%>0. %<0. 062 062

0.0513 2.7179 2.4615 2.6154 0.8205 91.333 54.8 Particle size class

Particle size distribution, 166024 Particle size distribution, 166030 100 80

80

60

%

60 %

40

40

20 20 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

0 %>64 %>32 %>16 %>8

%>4

%>2

1.3514 4.2703 4.4865 5.9459 2.1081 81.838 68.638 0

Series1

Particle size class

%>0. %<0. 062 062

8.4262 14.91 5.1985 3.3705 0.6855 67.409 34.828 Particle size class

Particle size distribution, 166031 Particle size distribution, natural gravel 100 40

80

30

%

60 %

40

20

20 10 0 %>64 %>32 %>16 %>8 Series1

0

%>4

%>2

%>0. %<0. 062 062

0 %>64 %>32 %>16 %>8

%>4

%>2

2.0005 6.5401 4.2062 2.9751 2.5135 81.765 49.059 0

Series1

Particle size class

%>0. %<0. 062 062

15.167 22.278 17.63 11.426 1.7037 31.796 2.0514 Particle size class

Gravel:fine ratio, 166025

Clast size statistics 2.5

0 gr av .

60 3

16

N

at .

8

9 60 2

16

60 2

1

4

60 3

16

Context

Nat. grav.

16

0.221928666 0.223023839 0.128158845 0.094890511 166023 166024 166031 166028 166029 166030

3

0

Maximum clast size

60 2

0.578947368 0.483474576

0.5

Mean (10) largest

60 2

1

16

mm

G:F

1.5

100 90 80 70 60 50 40 30 20 10 0

16

2.145020384

2

Context

Figure 24 Feature No. Contexts/age ascription

125144 125148 125146 125145

Particle size distribution, 125148 80

%

60 40 20 0 %>64 %>32 %>16 %>8 Series1

0

11

3.8

4.5

%>4

%>2

1.8

4.9

%>0. %<0. 062 062 74

39.846

Particle size class

Particle size distribution, 125146 100 80 %

60 40 20 0 %>64 %>32 %>16 %>8 Series1

0

0.75

3.9

3.8

%>4

%>2

%>0. %<0. 062 062

2.1

3.7

85.75 46.55

Particle size class

Partice size distribution, 125145 60 50 %

40 30 20 10 0 %>64 %>32 %>16 %>8 Series1

0

6.5385

21

%>4

9.2308

5

%>2

%>0. %<0. 062 062

4.3846 53.846 9.6154

Particle size class

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

Clast size statistics 0.857142857

mm

G:F

Gravel:fine ratio, 125144

0.351351351 0.166180758

125148

125146 Context

125145

90 80 70 60 50 40 30 20 10 0

Mean (10) largest Maximum clast size

125148

125146 Context

125145

Figure 25

Width:depth ratio/Gravel:fine ratio (upper fills) 1.2

Coarser

Gravel:fine ratio

1 Cursus ditches 0.8

Diagonal ditches Ditches near ring ditch

0.6

N/S ditches east of B

0.4

Bed C ditches 0.2 0 0

5

10

Width:depth ratio

Wider

15

Figure 26

Gravel:fine lower fills/Gravel:fine upper fills

Coarser

Gravel:fine lower fill

3 2.5 Cursus ditch

2

Diagonal ditch

1.5

Ditches near ring ditch

1

N/S ditch east of B

0.5 0 0

0.2

0.4

0.6

G:F upper fill

Coarser

0.8