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Macharioch Geophysical Survey
Date 18 April 2009 - 2 May 2009
Event ID 605417
Category Project
Type Project
Permalink http://canmore.org.uk/event/605417
NR 173646 609268 An integrated programme of gradiometer, resistivity and magnetic susceptibility surveys, which aimed to identify the character of potential archaeology, was carried out around the upstanding stones of a possible chambered cairn from 18 April–2 May 2009. Two base lines were laid out using tapes. The first was aligned ENE and the second was orientated at 90° to the first. The NE origin peg for both base lines was at NR173610 609275. The surveys, which did not incorporate the scheduled area, detected a series of anomalies.
The gradiometer survey was carried out over four 30m grids, using a Bartington Grad601 dual sensor vertical
component fluxgate gradiometer, and a sampling interval of 0.25m on a 1m traverse. Even without processing it is clear that the chambered cairn has not been removed by ploughing and extends well beyond the scheduled area (see plot). The extreme values from the stones suggest that igneous rock may have been used in its construction.
The resistivity survey was carried out over four 20m grids, using a Geoscan RM15 twin probe with 0.5 spacing, and a sampling interval of 0.5m on a 1m traverse. Once again the tomb is apparent but the contrast between positive and negative readings is not particularly pronounced. This could be because the ploughsoil covering the monument is too deep, with the archaeology below 0.5m, or simply bland results due to the saturated state of the ground (heavy rain occurred before and during the survey).
Previous fieldwork had identified lithic scatters on the N side of this field (DES 2006), and an attempt was made to determine whether an increased level of activity could be detected in relation to these scatters. Four 100m grids were sampled at 10m intervals with a Bartington MS2 magnetic susceptibility meter with a MS2D field survey 185mm loop sensor. A fifth grid was limited to 80m by the field boundary.
The results show a large anomaly running N–S within the E side of the survey area. Test pitting carried out in the next field (DES 2006) had demonstrated the presence of ancient dune systems below thin topsoil. This dune system probably continues into our survey area and would explain these results. A second trend in the data seems to be higher readings as the field slopes to the S. This may indicate increased human settlement activity closer to Macharioch Bay. Further data processing from all surveys is required.
Archive: RCAHMS (intended)
Funder: University of Central Lancashire
Vicki Cummings and Gary Robinson – University of Central Lancashire/Bangor University
