Snuffler 1504

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A GPR survey of Roman Chichester

Text of Snuffler 1504

  • Site Code. CHICHESTERGPR15Site identification

    and addressChichester

    County, district

    and / or boroughChichester District Council

    O.S. grid ref. ManyGeology. Alluvium over London ClayProject number. SNUFFLER1504Fieldwork type. Geophysics GPRSite type.Date of fieldwork. July 2015Sponsor/client. CDCProject manager. David StaveleyProject

    supervisor.Period summary Roman and Medieval

    Project summary.

    (100 word max)GPR survey over various parts of Roman Chichester

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  • A Ground Penetrating Radar Survey Targeting RomanChichester

    by David Staveley

    Contents

    1. HER Statement2. Contents3. Introduction3. Acknowledgements3. Methodology4. Priory Park4. Positioning6. Results6. Area 18. Area 214. Area 319. Area 421. Area 1,3,4 Interpretation24. Area 2 Interpretation26. Conclusion27. Amphitheatre27. Positioning28. Results33. Interpretation35. Conclusion36. Single Transect Surveys36. Stane Street39. Town Walls42. Conclusion43. References

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  • Introduction

    This project was initially started to answer a particular research question, which was whether or notStane Street continued on through Chichester and out of the south gate instead of stopping at theeast gate. This theory was put forward by John Magilton (1995B, p.31), who suggested that the roadpre-dated Chichester. The original plan was to walk along all of the pavements within the Romantown walls, taking single GPR B-scans and joining the dots to reveal the internal Roman roadlayout of the town. It subsequently became clear that the archaeology was too damaged and tooshallow for this to work well, so radar surveys of grassed areas at Priory Park and the Amphitheatrewere added to make the project more fruitful. Other areas received light attention with a view tocarrying out further radar work.

    Acknowledgements

    The author would like to thank James Kenny of Chichester District Council for making this possibleand for his expert local knowledge of the archaeology. This wisdom is hereafter referred to as JKPC(James Kenney Pers. Comm.)

    Methodology

    The surveys shown here were carried out using an UTSI Groundvue 3a ground penetrating radarwith a 400MHz antenna. A-Scan separation is ~3cm and line separation varied between surveyareas. The data was processed using ReflexW, with static correction, background removal, gain andband pass filters applied. Depths given assume a velocity of 0.1m/s and are only a rough estimation.No hyperbola fitting has been done. Survey grids were set out and position recorded with a JavadTriumph-LS GNSS net rover. Any position given is OSGB36/OSTN02/Newlyn Datum. Ininterpretation images, possible Roman features are shown in green, possible medieval in yellow andpossible modern in red.

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  • Priory ParkTwo areas of the park were surveyed, the large cricket pitch to the east (Area 2) and the smallertriangular area of grass to the south of the Guildhall (Area 1). Since the area was so large, a lowresolution exploratory survey was undertaken with lines spaced one metre apart and walking east-west, with a view to surveying areas again at a higher resolution if something interesting was found.Two further areas of interest (Areas 3 and 4) south of the town hall were then surveyed with 25cmline spacing when Roman buildings were found for a total of four survey areas. Select time slicesare shown to display the features discussed in the interpretation.

    Positioning

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  • Area Pos Easting Northing1 Size 50m 55m

    A 486195.80 105104.38B 486245.74 105106.49C 486248.07 105051.56

    2 Size 120m 130mD 486253.83 105151.86E 486353.29 105166.08F 486258.90 105032.00G 486378.77 105037.07

    3 Size 25m 30mH 486213.08 105098.11I 486238.05 105099.16J 486214.35 105068.14K 486239.32 105069.20

    4 Size 25m 20mL 486222.68 105060.49M 486247.65 105061.54N 486248.49 105041.57

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  • Area 1 Results

    Area 1 16.6ns (~83cm)

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  • Area 2 20.7ns (~103.5cm)

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  • Area 2 Results

    Area 2 10.5ns (~52.5cm)

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  • Area 2 11.9ns (59.5cm)

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  • Area 2 13.1ns (~65.5cm)

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  • Area 2 15ns (~75cm)

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  • Area 2 16.4ns (~82cm)

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  • Area 2 24.2ns (~121cm)

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  • Area 3 Results

    Area 3 13.7ns (~68.5cm)

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  • Area 3 19ns (~95cm)

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  • Area 3 22ns (~110cm)

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  • Area 3 27ns (~135cm)

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  • Area 3 30.5ns (~152.5cm)

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  • Area 4 Results

    Area 4 11.4ns (~57cm)

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  • Area 4 17ns (~85cm)

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  • Areas 1,3,4 Interpretation

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  • A) This feature, clearly visible on aerial photographs, is a modern reservoir (JKPC). It is visible inthe slices from the surface and the walls slope inwards slightly until it disappears at about a depth of60cm.

    B) This building appears to be a Roman town house. The highest upstanding sections of wall, on theeast and north side start to make an appearance at 30cm, and intact floors to the south-west at 35cm.One room appears to have a complete floor and three other rooms surrounding it have partial floorspaces remaining. A full set of foundations don't appear in the slices until about 85cm, so thereseems to be significant robbing of the walls, especially in the north where some walls have gonecompletely. The whole building probably extended further to the west, but will have been truncatedby feature A.

    C) This feature appears to be in very good condition, probably due to its depth. The highestremaining wall parts are at 45cm, lower than building B by 10cm, but the rest of the building issunken, with the completely intact floor not making an appearance until a depth of 90cm. This floorslopes downwards from the south to the north by 20cm. This slope is consistent rather than warped,so may be down to design rather than post Roman sinking of the feature. The wall appearing to cutthe building in half is only about 10cm high at the bottom, with the surrounding untouched wallsextending much higher, so again this may be down to design rather than robbing. The smallextension to the west may be access down into this room from the Roman surface level, but stepsare not visible on the results. The building seems to be connected to building E to the south, both bya wall and the same orientation. The most likely interpretation is an unheated bathing pool.

    D) This flat section of hard material may be a collapsed section of Roman wall, perhaps preservedas other upstanding sections were more obvious targets for stone robbing, with this section covered,but due to a lack of foundation at this point, a more likely explanation is that this is a medievalfeature associated with feature G, constructed of robbed Roman material. The blue line on theinterpretation is the line of the transect shown below. Feature D is shown to the centre left, with thecut of feature G showing weakly diving down next to it, before rising again to another small solidfeature to the east that is on the same level as feature D. The three seem associated in this transect,hence the suggestion that they are of the same date.

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  • E) Another possible Roman building, connected to building C by a wall. It is not in as good acondition as building B. The highest surviving sections of wall appear at 30cm, the centre wallrunning N-S. Most of the walls in the northern part have appeared by 50cm and the southern part by60cm. There are no surviving floor layers.

    F) This small circular feature is bowl shaped. It appears at 35cm, being ~140x190cm wide curvingdown to a base ~80cmx110cm wide at a depth of 50cm. It's purpose is unclear. A transect across thisfeature, shown by the blue line on the interpretation, is shown below, with feature F in the centre.To the east of that, some of the rubble filling the cut of feature G is visible.

    G) This feature is most likely the same as feature J in area 2, but here is more visible, as the fillcontains some solid material. Due to the proximity to building E, this solid material used forbackfilling this feature may be wall and floor material robbed from feature E. The feature seems toend abruptly at feature D, which may be associated with it, but this is not a certainty, given feature Jin area 2 is so hard to see. What is not visible in area 1 to the north of feature G is the same phasechange in the un-enveloped data that defines feature J in area 2. The profile looks curved to thenorthern end, as shown on the transect associated with feature D, while to the south the cut seemsalmost vertical, as shown on the transect associated with feature F.

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  • Area 2 Interpretation

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  • A & B) Features A and B were originally part of the Roman street grid of Chichester. It is roughly6.5m wide to the north and 8m wide to the south, but were once the same feature, being cut by themedieval motte ditch, feature E. To the south, it seems it is also cut by feature H. The whole is onthe same line as a previously known road that heads roughly along the line of Little London (Down1988 p.15). Also to the south, there is a 3m wide branch road heading east, perpendicular to themain street for a distance of roughly 17m. These features appear in some form almost from thesurface, and are visible as parch marks in dry weather, though the most solid parts start at a depth of25cm. Further, less solid material, on the line of the road is visible almost to the surface. At depth,the road can still be seen at around 70cm. Feature B is partly cut by feature F, plus there are twofurther cuts on the east side of A and B which are either down to robbing or Saxon occupation.

    C) Nestled within