innermessan, near stranraer: interim report on resistance and magnetic survey

7/30/2019 Innermessan, near Stranraer: Interim Report on Resistance and Magnetic Survey

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DISCOVERING DUMFRIES ANDGALLOWAYS PAST

GEOPHYSICAL SURVEY AT INNERMESSAN, NEAR STRANRAER

INTERIM REPORT


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Author:Giles CareyDate of Issue: 12/12/12

Contents

Summary ................................................................................................................................................... 2Acknowledgements ................................................................................................................................... 3Introduction ............................................................................................................................................... 4Project Background ................................................................................................................................... 4

Site Location ...................................................................................................................................................... 4Aims and objectives ........................................................................................................................................... 4Archaeological and historical background .......................................................................................................... 4

Geophysical survey ................................................................................................................................... 6Standards........................................................................................................................................................... 6

Field methods .................................................................................................................................................... 7Data processing ................................................................................................................................................. 7

Results ...................................................................................................................................................... 7Area A ................................................................................................................................................................ 7Area B ................................................................................................................................................................ 8

Conclusions ............................................................................................................................................... 9Open Day .................................................................................................................................................. 9

Appendix 1: Technical data ..................................................................................................................... 10

Appendix 2: Volunteers ........................................................................................................................... 11Bibliography ............................................................................................................................................ 12

0BList of figures

Cover image: volunteers undertaking magnetic survey at base of Innermessan motte ............................ 1Figure 1: General location of geophysical survey .................................................................................... 13Figure 2: Area A - raw resistance survey data ....................................................................................... 14Figure 3: Area A: processed resistance survey data .............................................................................. 15Figure 4: Area A raw magnetic survey data ........................................................................................ 16Figure 5: Area A processed magnetic survey data .............................................................................. 17


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IntroductionThis report presents the results of a week of both magnetic (gradiometer) and resistance survey carriedout at Innermessan, 2km to the north of Stranraer. The survey was focused on two key areas, one at thefoot of the extant motte adjacent to Innermessan steading (NMRS NX06SE 3; Area A) and another in afield 350m to the north, where converging cropmarks of field boundaries have been observed on aerial

photographs (NMRS NX06SE 98; Area B).

A total of 1.4ha of magnetic survey and 0.8ha of resistance survey were carried out over the course of 4days.

This fieldwork was carried out by volunteers drawn from the local community, under the supervision ofstaff from the University of Glasgow. The survey was part of Discovering Dumfries and Galloways Past,a project engaging local communities across the region in non-intrusive archaeological fieldwork.

Project Background

Site LocationBoth areas were under pasture at the time of survey, although Area B has been under cultivationrecently.

Ground conditions were generally good during the survey, although the weather was mixed, with short,heavy rain showers at times hindering progress.

Area A comprised a flat area at the base of the motte (see cover photograph). A series of pylons ranalong the eastern boundary of the survey area, but these did not appear to adversely affect the results ofeither survey. Area B comprised a flat field to the north of Area A; some disturbance was noted aroundthe field entrance from recent cattle activity. The southern boundary fence was electrified, although theeffects on the magnetic survey carried out in this area appear to be minimal.

Aims and objectivesThe purpose of any geophysical survey is to as far as reasonably possible, determine the nature of thedetectable archaeological resource within a specified area using appropriate methods and practices


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NMRS No Object Period

NX06SE 16 Brass Ewer Medieval

NX06SE 17 Bronze Flat Axehead Early Bronze Age

NX06SE 18 Bronze Socketed Axehead Late Bronze Age

NX06SE 19 Side-blown horn Late Bronze Age

NX06SE 20 Bronze Flanged Axehead (Blacarry

type)

Bronze Age

NX06SE 214 Silver Octagonal Brooch 13t/14

tcentury

Chance finds made in the Innermessan Area. Source: National Monument Record of Scotland

Historical research, primarily associated with the lost town of Innermessan, has revealed a long historyof settlement in the medieval period across this area (Hunter, 2003). In 1429, The Agnews of Lochnawtook possession of Innermessan. As a burgh of barony, the town apparently flourished at this time. Thetown, on the shores of Loch Ryan, is depicted prominently on maps from the early 17 th-century onwards.

It appears to have gone into decline as Stranraer developed.


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Rev James Ferguson, who records a stratum containing of ashes, charred wood and fragments ofbone (New Statistical Account, 1845: 86). No evidence for associated structures with the motte hasbeen recorded to date.

Area B

Aerial reconnaissance over this field has recorded the the cropmarks of a ditch, apparently forming twosides of a possible rectangular enclosure 350m N of Innermessan Farm. These two sides appear to joinat a corner-angle (reminiscent of Roman camps) and the longer side is visible for about 130m (NMRSNX06SE 98).

Additionally, this area appears to have been intensely used in WW2. The substantial water tank at thefield entrance dates from when the camp was in use.

Slipway

Nissen huts of camp

Water tank

Motte


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Field methodsAn overall survey grid was established using tapes, with reference to known points on Ordnance Surveymapping. Data collection was carried out using a standard methodology, with data collected in 20m gridunits, with all grids walked in the same direction (N-S).

A Geoscan RM15 resistance meter was used to conduct the resistance survey; the sample interval usedwas 1.0m with a traverse interval of 1.0m. All grids were walked in a zig-zag traverse scheme.

A Geoscan FM36 fluxgate gradiometer was used to collect magnetic survey data; the sample intervalused was 1.0m with a traverse interval of 1.0m with all data being hand-logged. Initially, two grids in

Area A were walked in a zig-zag traverse scheme, subsequently all traverses were walked in parallel toimprove data resolution.

Data processingGeoplot software (version 3) was used to download and process the resistance data. Greyscale plots ofboth raw and processed data were produced in Geoplot, and are presented in this report as figures 2-9.

The raw data has been subject to minimum editing to remove operator error, with data subsequentlyprocessed to remove geological and background biases and interpolated to aid interpretation (seeappendix 1).

ResultsA set of interpretative diagrams are presented in text below, with certain anomalies annotated for easeof reference in the discussion below.

Area ASee figures 10 and 11

Magnetic survey across the flat area around the base of the motte has recorded a number of anomalies,although the background of the survey is generally magnetically quiet.

The dipolar magnetic trace of the pipeline (A1) is immediately obvious to the north of the survey area,


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associated with a telegraph pole. This area is crossed by a number of linear trends, visible in bothsurveys, which are best interpreted as drainage/field boundaries.

Given the concentration of features in these 5 grids, this area formed a focus for resistance survey.These complemented the results of the magnetic survey.

Interpretation of both surveys in area A (left) and comparison of magnetic and resistance surveys (right); see fig. 10 and 11

Anomaly A3 is particularly clear in both datasets which lends credence to it being a feature ofarchaeological interest. Additionally, a small penannular feature is visible in the conjectural centre of theanomaly; however, this is poorly defined so its interpretation must remain putative.

The size and morphology of this feature, where clearly defined, suggests that it might represent a smallstock enclosure. If it is accepted that its circuits are cut by the motte ditch anomaly, it must pre-date the12th century. Although nothing further can be said at present about this feature, it is worth noting that its

size would be commensurate with that of settlement enclosures identified in Wigtownshire (see Poller,2005: Appendix 2), including ones very close to the site on the slopes of Craigcaffie. These have beenloosely dated as later prehistoric2.


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to before the mid-19th century, as field boundaries are not shown in this area on the 1 st edition OrdnanceSurvey 6-inch map (Wigtownshire 1849, sheet 85NX06SE), although rig and furrow cultivation has beennoted in this area from air photographs taken in 1995 (NMRS NX06SE 98).

The only other feature present (B3) represents an area of extensive disturbance visible at the field

entrance.

Interpretation of both surveys in area B: magnetic survey (left) and resistance survey (right); see fig. 12 and 13

ConclusionsThe programme of resistance and magnetic survey at Innermessan has recorded a number of featuresof interest.

Unfortunately, no evidence of a bailey, or of features which could potentially be associated with theburgh of barony were recorded in Area A, adjacent to the motte. The background to this survey area wasparticularly quiet suggesting, intriguingly, limited activity on this tongue of land.

Of particular note in this area, however, is the apparent double-ditched feature which appears to be cutb th 12th t tt dit h If thi h th i t d thi f t d t t ti ll t th


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Appendix 1: Technical data

Resistance Data

1. Raw Data

Clip(limits maximum and minimum values for display and subsequent processing): -2/+2 Despike(removes large anomalies above a certain threshold): x-radius 1; y-radius 1; threshold 2Zero Mean Grid(normalizes dataset to remove discrepancies between balancing of remote probes)

2. Processed data

Edge matching(further refines normalization of dataset)

Interpolation(smoothes greyscale appearance by adding extra data points into the dataset, calculatedwith reference to surrounding collected data) on both the Y and X-axis

Gradiometer Data1. Raw Data

Clip(limits maximum and minimum values for display and subsequent processing): -2/+2 Despike(removes large anomalies above a certain threshold): x-radius 1; y-radius 1; threshold 2. A

number of large ferrous responses were visible in the data, caused by iron-rich stone close to thesurface.Zero mean traverse(to remove striping from grids, cuased by inaccurate N-S balancing ofgradiometer). Note: this was only visible in data collected in zig-zag traverse scheme.

2. Processed data

Low pass filter(smoothes data and enhances larger weak anomalies)Interpolation(smoothes greyscale appearance by adding extra data points into the dataset, calculatedwith reference to surrounding collected data) on both the Y and X-axis


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Appendix 2: Volunteers

Thanks to all the following for their help over the course of survey:

Margaret CooperRuth FlemmingRichard LawesStephen ByrneNigel JoslinLes Dunford

Anne DunfordPhil Heslop

Walter WalkerPamela Walker


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Bibliography

English Heritage, 2008 Geophysical Survey in Archaeological Field Evaluation[online]HUhttp://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf 04/07/2011U

Geoscan Research 2005 Geoplot Instruction Manual[consulted online]HUhttp://www.geoscan-research.co.uk/Gp300Proc3.pdfUH 04/07/2012

Gill, B. 1999 Title: The Cairnryan Military Railway 1941-1959Stranraer: Stranraer & District LocalHistory Trust

Hunter, J. 2003 The Lost Town of InnermessanStranraer: Stranraer & District Local History Trust

IfA, 2010 Draft Standard and Guidance for Archaeological Geophysical Survey[online]HUhttp://www.archaeologists.net/sites/default/files/node-files/geophysicsSG.pdf 04/07/20112U

New Statistical Account, 1845 Inch Parish[consulted online]http://stat-acc-scot.edina.ac.uk/link/1834-45/Wigton/Inch/4/86/12/12/2012

Poller, T. 2005 Interpreting Iron Age Settlement Landscapes of WigtownshireUnpublished PhD thesis,

University of Glasgow.

Schmidt, A. 2001 Geophysical Data in Archaeology: A Guide to Good PracticeYork: Archaeology DataService

Other sources

National Monument Record of Scotland (NMRS) consulted athttp://canmore.rcahms.gov.uk

National Collection of Aerial Photography consulted athttp://aerial.rcahms.gov.uk
http://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf%2004/07/2011http://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf%2004/07/2011http://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf%2004/07/2011http://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf%2004/07/2011http://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf%2004/07/2011http://www.geoscan-research.co.uk/Gp300Proc3.pdfhttp://www.geoscan-research.co.uk/Gp300Proc3.pdfhttp://www.geoscan-research.co.uk/Gp300Proc3.pdfhttp://www.geoscan-research.co.uk/Gp300Proc3.pdfhttp://www.geoscan-research.co.uk/Gp300Proc3.pdfhttp://www.archaeologists.net/sites/default/files/node-files/geophysicsSG.pdf%2004/07/20112http://www.archaeologists.net/sites/default/files/node-files/geophysicsSG.pdf%2004/07/20112http://www.archaeologists.net/sites/default/files/node-files/geophysicsSG.pdf%2004/07/20112http://www.archaeologists.net/sites/default/files/node-files/geophysicsSG.pdf%2004/07/20112http://stat-acc-scot.edina.ac.uk/link/1834-45/Wigton/Inch/4/86/http://stat-acc-scot.edina.ac.uk/link/1834-45/Wigton/Inch/4/86/http://stat-acc-scot.edina.ac.uk/link/1834-45/Wigton/Inch/4/86/http://stat-acc-scot.edina.ac.uk/link/1834-45/Wigton/Inch/4/86/http://canmore.rcahms.gov.uk/http://canmore.rcahms.gov.uk/http://canmore.rcahms.gov.uk/http://aerial.rcahms.gov.uk/http://aerial.rcahms.gov.uk/http://aerial.rcahms.gov.uk/http://maps.nls.uk/http://aerial.rcahms.gov.uk/http://canmore.rcahms.gov.uk/http://stat-acc-scot.edina.ac.uk/link/1834-45/Wigton/Inch/4/86/http://stat-acc-scot.edina.ac.uk/link/1834-45/Wigton/Inch/4/86/http://www.archaeologists.net/sites/default/files/node-files/geophysicsSG.pdf%2004/07/20112http://www.geoscan-research.co.uk/Gp300Proc3.pdfhttp://www.geoscan-research.co.uk/Gp300Proc3.pdfhttp://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf%2004/07/2011http://www.english-heritage.org.uk/publications/geophysical-survey-in-archaeological-field-evaluation/geophysics-guidelines.pdf%2004/07/2011


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DDGP: Survey at Innermessan, near Stranraer. - 13 -FIGURE 1:GENERAL LOCATION OF GEOPHYSICAL SURVEY

Area A

Area B


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DDGP: Survey at Innermessan, near Stranraer. - 14 -FIGURE 2:AREAA- RAW RESISTANCE SURVEY DATA


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DDGP: Survey at Innermessan, near Stranraer. - 15 -FIGURE 3:AREAA: PROCESSED RESISTANCE SURVEY DATA


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DDGP: Survey at Innermessan, near Stranraer. - 16 -FIGURE 4:AREAA RAW MAGNETIC SURVEY DATA


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DDGP: Survey at Innermessan, near Stranraer. - 17 -FIGURE 5:AREAA PROCESSED MAGNETIC SURVEY DATA


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DDGP: Survey at Innermessan, near Stranraer. - 18 -FIGURE 6:AREA B RAW RESISTANCE SURVEY DATA


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DDGP: Survey at Innermessan, near Stranraer. - 19 -F

IGURE7:

A

REAB

PROCESSED RESISTANCE SURVEY DATA


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IGURE8:

A

REAB

RAW MAGNETIC SURVEY DATA


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IGURE

9:

AREA

B

PROCESSED MAGNETIC SURVEY DATA


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DDGP: Survey at Innermessan, near Stranraer. - 22 -

FIGURE 10:AREAAINTERPRETATION DIAGRAM


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FIGURE 11:AREAADETAILED COMPARISON OF RESISTANCE (LEFT) AND MAGNETIC (RIGHT) SURVEY DATA, IN VICINITY OF MOTTE


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FIGURE12:AREA B RESISTANCE SURVEY INTERPRETATION DIAGRAM


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FIGURE13:AREA B MAGNETIC SURVEY INTERPRETATION DIAGRAM

innermessan, near stranraer: interim report on resistance and magnetic survey

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