Easter 2017 Fieldwalking and Magnetometry Surveying

This Easter a team assembled to carry out a comprehensive field survey of the intersecting areas of Chalk Pit Field, Hall Field and Shernborne Breck (Polar Breck is currently home to a number of ewes and lambs). In 2005 and 2006, SHARP carried out evaluation excavations on a Late Iron Age through to Romano-British farmstead in Polar Breck  and Chalk Pit Field respectively. The excavations in Polar Breck uncovered a cobbled surfaced, presumed to be of a yard and an E-W running ditch feature dated by pottery and coin finds to a 3rd/4th century date. These Romano-British remains post-dated a series of Late Iron Age features, including ditches containing much pottery of that date.

The 2006 excavations in the SE corner of Chalk Pit Field exposed further E-W and N-S running ditches of the Romano-British period, along with a clay-built oven, ducting hot gasses into a post-built structure, presumed to be either a malting or drying shed. It was in the base of this oven that the burnt human body of mid-4th century date was discovered. The Romano-British features again were found to cut through earlier Late Iron Age features.

The aim of the April 2017 field work programme was to conduct a pre-excavation assessment of the area around the intersection of the four fields, prior to a further evaluation excavation of the site during the summer 2017 excavation season. Field walking, metal detector survey and a large area magnetometry survey were combined as part of the pre-excavation investigations.

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Map of field survey areas

Fieldwalking in Shernborne Breck was generally unproductive. This might be an indication of low levels of past settlement activity in the field, but the possibility that ground preparation for the potato crop had buried artefacts in the ‘earthing-up’ process, combined with dry weather preventing their exposure by rain-wash cannot be discounted. Metal detecting in Shernborne Breck proved to be challenging and restrictive due to the mounds for the potato crop. This only left the bottom of the toughs to detect, and as these were only about half a metre wide it provided very little scope to swing the detectors. We did eventually manage to cover most of the same area as that covered by magnetometry. The finds were disappointingly largely iron nails, but also found were part of an iron key, a bag seal and one musket/pistol ball.

Accordingly the focus was switched to Chalk Pit (South) and Hall Fields. Polar Breck was not available for study, being in pasture and stocked with ewes in lamb. Surface finds of both grey and black Romano-British pottery, as well as abraded Iron Age pottery, were made in both fields (in the vicinity of the four field intersection), with the greater proportion being from Hall Field. Of particular interest were two Neolithic artefacts – a flint scraper and a leaf-shaped arrowhead. Ceramic finds of note included the handle from a Roman Amphora (indicating the import of either olive oil or wine from the continent), a piece of Roman tile (bearing a wave pattern) and a well-preserved Samian ware pedestal base (possibly part of a flat dish). Manufactured in southern Gaul from the late 1st and through the 2nd centuries, the Samian find pushes the date of the farm site back into the second century and perhaps into the first.

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Part of Roman Amphora handle

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Samian ware pedestal base

The pattern of distribution of ceramic finds suggests the likelihood that the domestic buildings of the farm are to be located in Hall Field and the working part in the other fields. As Hall Field and Chalk Pit Field both had a young emerging crop (i.e. not potatoes!), it was pretty much ideal metal detecting ground to work on. The detectorists again covered the same area as that surveyed with the magnetometer. Both of these fields yielded few decent signals but by the end of week the finds amounted to five Roman coins, one and a quarter silver hammered coins, three musket/pistol balls, part of a fibula brooch, a Romano-British pestle and a few other nondescript items.

Cosmetic grinders are small two piece sets made from copper alloy. They comprise – a larger component – the mortar; and the smaller component – the pestle. Both components have a crescent or elliptical shape and nearly all have a loop for suspension. The mortar has a channelled groove, the pestle is a solid rod. The pestles vary in shape from strongly curved ellipses to virtually straight examples. End looped examples (as found) tend to be longer than the middle looped examples, most fall within 40-75mm – the one found is 56mm in length. The suspension loops can be completely plain, through to having ornate decoration, our example is relatively plain.

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Romano-British pestle

Their purpose is thought to be to prepare a substance or substances by crushing or grinding a small quantity in the groove of the mortar – our pestle shows a flattened surface on the underside. What was being ground, and for what purpose, is not clear as no examples have yet been found with any residue. But, an example found in London was fused together with a nail cleaner and tweezers, this may suggest that they were all held together on a cord and used for some form of body care or make up preparation/application.

It is possible that small quantities of minerals were ground and applied to the face, for example rouge from ground haematite, grey/black from galena or graphite, and green from ground malachite. Likely to be from the late Iron Age to Roman period. To find out more information search ‘Cosmetic sets of late iron age and Roman Britain – Ralph Jackson (https://www.britishmuseum.org/pdf/0%20Prelims-%201-3-rfs%20pp.pdf).

The field walking results combined with the metal detecting finds in this and in previous seasons, have demonstrated the importance of further evaluation by excavation. The new SHARP magnetometer, piloted by Wing Commander (Retd.) David Wood, well assisted from the right hand seat by ‘First Officer’ Yvonne Bolton-Smith has produced dramatically good results, allowing the siting of trenches to be focussed to maximise the results from excavation.

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Setting up the magnetometry equipment

The results point to excavation opportunities stretching over several years and to the possibility of discovering whether there is a continuation of Late Iron Age activity into and throughout the Roman period, or whether there is a hiatus following the revolt of 61AD until re-occupation in the late 1st/early 2nd century.

The purpose of the geophysical survey was to detect any buried archaeological anomalies that might provide a measurable magnetic response. A fluxgate gradiometer (magnetometry) survey was undertaken on 3 of the 4 field quadrants centred on the intersection of boundaries of Chalk Pit Field (South), Hall Field and Shernborne Breck. Polar Breck will be completed later in the Spring (due to ewes in lamb at the time of the survey). The field work was undertaken between Saturday 8th April to Thursday 13th April 2017, weather conditions being warm and mostly dry, with a brisk wind. 40m x 40m grids were set out, where possible. However, 20m x 20m grids were used in part of Shernborne Breck due to the restrictions imposed by a newly planted potato crop. Each grid was surveyed with 1m traverses; samples were taken every 0.25m. Data was collected along N-S traverses in a zigzag pattern, beginning in the south-west corner of each grid where possible.

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The depth of the seeded potato crop in Sherborne Breck

A significant number of anomalies were identified in each of the quadrants, as shown in the final picture composite. Many of the features matched those of LiDAR, aerial photos, previous surveys and the exploratory SHARP excavation in 2006. The initial assessments of the survey in Hall Field show east-west and north-south aligned linear features which possibly constitutes an enclosure. This area is immediately to the east of the 2006 excavation in Chalk Pit Field. Another feature of interest is the north-south aligned feature (showing as a white line on the survey) which measures approximately 40 metres in length and could be part of a building structure.

Hall Field

 

 

 

 

 

 

 

 

 

 

 

 

 

Hall Field magnetometry survey (N⬆︎)

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Shernborne Breck magnetometry survey (N⬆︎)

The distinct depression or pit (visible on LiDAR as well as on the ground) in Shernborne Breck was detected by the magnetometer as a significant positive flux response in the shape of an oval. However, the similar positive flux response a few metres to the west was not associated with a depression or pit. Many additional pits and unknown anomalies were detected throughout all the areas, some associated with burning or high temperatures and some which appear ferrous in their magnetic signature.

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 LiDAR map of the Sedgeford locality

Assessment of the magnetometer survey is still ongoing and we will provide further updates. Combined with last year’s fieldwalking in Hall Field and the combined surveys last week, SHARP has some very enticing archaeology to pursue in the future within this area.

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