Probe Installation (phase 1) at Diddington 6th-8th June 2011
Between the 6th and 8th of June work was undertaken in a pasture field at Diddington, Cambridgeshire. The main focus of this work was the installation of Time Domain Reflectometry probes, temperature sensors and the removal of bulk soil and other samples in a trench containing an archaeological feature. Additional work included coring, SPAD and spectroradiometry transects.
The field team consisted of:
- Keith Wilkinson (directing)
- Anthony Beck
- Dan Boddice
- Rob Fry
- Laura Pring
- David Stott
Machining was undertaken by Mark from Lattenbury Services. Many thanks to Tim and Vicky Dickens from Thornhill Estates for all their help. Quinton Carroll, the Cambridgeshire County Archaeologist, visited the excavation prior to backfilling on the 8th.
The trench was located over a feature detected by magnetometry survey and characterised by coring. The cores contained pottery fragments and charcoal. Topsoil was removed by a JCB with a 1.2m wide toothless ditching bucket. The trench was excavated to a length of 7m. A sealing layer with a depth of 30cm was under the topsoil and also removed by machine. This layer looks like a high energy waterborne deposit laid as part of an aggrading phase of the floodplain. Further research will be undertaken on the nature and extent of this deposition event. The ditch was in the expected location at 60cm depth. It was a 60cm deep feature with a flattened V shaped profile that contained three fills. The upper fill (context 3) contained bone, slag, daub and pottery. The fill was sandy silt with frequent gravel inclusions and occasional flecks of charcoal. Context 4 contained pottery, stone and slag. The fill was dark sandy silt with frequent charcoal and occasional gravel inclusions. The basal fill, context 5, contained flint and a single sherd of pottery. The fill was largely sandy gravel with rare charcoal flecking. After the sediments were excavated and recorded the surrounding ‘natural’ matrix was removed by machine using a toothed bucket to a depth of c. 1.2m. Bulk samples of the ‘natural’ soil were taken by machine and emptied into cubic metre soil sacks. The section was cleaned and recorded and each context was recorded.
The machine excavated a 30cm deep platform for the solar panels and box which contains the batteries and sensor array. The frame for the solar panels and sensor box was placed on the platform and levelled. The solar panel and box were installed and the frame partially backfilled to stabilise the base. 50 cm long metal bars, for Ground Penetrating Radar (GPR) calibration, were installed in the trench sections.
During day 2 the archaeological and non archaeological features were sampled. 7 monolith tins were taken as were bulk and other geotechnical soil samples. The TDR and temperature probes were inserted into the archaeological sediments and the surrounding soil layers. The location of all samples and probes were recorded. The weather station was connected.
David Stott and Anthony Beck established two transects in adjacent fields that ran over archaeological features and took SPAD (chlorophyll) readings at 1 metre intervals. The local drought conditions have revealed a range of crop marks in the adjacent wheat fields that were visible from ground level. CASI, LiDAR and hi-resolution vertical aerial photographic surveys have been commissioned from the Environment Agency to occur ASAP. In addition a bespoke request has been sent to the NERC Airborne Remote Sensing Facility for Eagle and Hawk hyperspectral surveys to capitalise on the ‘once in a hundred years’ weather conditions.
During day 3 the overnight readings were checked to ensure that the sensors were recording. After a brief visit from Quinton Carroll, who also confirmed that the pottery was likely to be mid-late Iron Age (c. 400BC – c. 100AD). The trench was then backfilled. Archaeological sediments and soils surrounding each sensor were hand compacted and the remaining soil reinterred with the aid of a minidigger and hand shovelling. The machine then compacted the trench. The bulk soil samples were moved to a secure location on site. Spectroradiometry reading s were taken at 1 metre intervals on the transects located in the adjacent fields. The site was recorded using dGPS and the location for cores were established along the line of the excavated ditch. Further cores were taken with a percussion corer. Finally, two straw bales were placed to the west of the sensor array and solar panel to obscure the installation from passing traffic on the A1.
All in all an excellent few days work!