Geophysical Survey

Date 18 August 2021

Event ID 1145279

Category Recording

Type Geophysical Survey

Permalink http://canmore.org.uk/event/1145279

NS 31930 39157 A geophysical survey was undertaken at Seagate Castle, Irvine on 18 August 2021. This survey forms part of wider evaluation of the site prior to consolidation works. The survey entailed resistance survey (0.8ha at 0.5m x 0.5m) and a Ground Penetrating Radar utilising a 500MHz antenna (0.8ha at 0.5m interval traverses) and a 250MHz antenna (0.8ha at 1m traverse interval).

The resistance survey has detected a wide variety of values across the site. In the SW of the survey area, adjacent to the extant castle, very low resistance has been recorded which is likely to be associated with increased moisture content of this ground. No anomalies suggesting the foundations of the known North range, or the cesspit have been detected. Well-defined anomalies have been detected in the N. While they appear structural in nature, given that resistance is usually only detecting to a depth of about 0.75m–1m, a modern origin associated with landscaping seems probable. A broad area of high resistance may suggest possible demolition rubble associated with a possible wing or wall related to the southern limits of the extant Castle although interpretation is tentative. More discrete, but ephemeral high resistance responses have also been noted in this area which may indicate remnants of surviving structural remains, although such an interpretation is cautious.

The 500MHz GPR survey has detected high amplitude

responses at a depth of 0.75m, which show good correlation with the resistance data supporting the presence of possible structures or demolition rubble associated with the southern limits of the castle. However, there is some suggestion in the GPR data that this may simply be associated with modern landscaping. Responses associated with the known western building and cesspit have been detected. Below 1m, there is some evidence in the GPR data for potential structural remains that may suggest features associated with earlier phases of the castle. However, responses from modern paths and past excavation introduces an element of caution.

The 250MHz GPR survey has identified potential earlier ground surfaces associated with the castle, prior to the area being landscaped in more recent times.

Archive: Rose Geophysical Consultants Funder: Rathmell Archaeology

Susan Ovenden – Rose Geophysical Consultants

(Source: DES Vol 22)