|Excavations at Oxford Castle Motte 2009|
As part of the Festival of British Archaeology Oxford Archaeology was asked by Oxford Preservation Trust to carry out a small excavation on the top of Oxford Castle motte. Oxford Castle was constructed in 1071 by Robert D'Oilly and comprised an earthen mound (motte), which survives today, and a large enclosure surrounded by earth ramparts and a moat (bailey) extending to the south-east. The motte and the bailey ramparts were constructed from layers of gravel, capped with clay that were derived from moats that surrounded them, and which were filled with water from the river Thames.|
It is likely that in the 11th century a wooden tower (keep) was located on top of the motte, which was replaced by a stone keep in the 12th century. The new stone keep was ten sided and may have encircled a smaller tower. A well chamber exists within the motte and was assumed to be contemporary with the stone keep.
By the 17th century the castle was largely ruinous. The keep had a large crack down one side, and was subsequently dismantled during the English Civil War (1642 - 1651). The motte was refortified and an earthen rampart constructed within the keep. In the 18th century the keep was levelled and the top of the motte was landscaped.
Our work follows on from an earlier excavations on the motte; in the 18th century, excavations by Daniel Harris exposed sections of the keep and well chamber, and last summer OA recorded the northern part of the keep as part of repair work on the motte. In April Stratascan carried out a geophysical survey of the motte to further identify the extent of the foundations of the keep, and to attempt to identify any other features. Their work helped determine the location of the current trenches.
We have excavated three trenches on top of the motte, measuring up to 4 m long and 2 m wide. The two trenches on the west and east sides of the motte have further defined the extent of the keep, where we have exposed two sections of 2 m wide limestone foundations. The castle would have been encircled by a stone wall on its ramparts, which would have abutted the keep on the motte. We had hoped to determine where these walls abutted the keep, but unfortunately no evidence of these walls has been found during this stage of works.
We have revealed a compacted gravel floor in the centre of the motte, which may have formed a surface in the original wooden tower. The surface is cut by a trench for the well chamber, and we hope to find evidence that will more closely date the well's construction. Deposits overlying the floor contained a redeposited glazed floor tile, which may have formed part of a surface within the stone tower.
Evidence for the refortification of the motte during the English civil war has also been revealed. Up to 1 m of redeposited clay and gravel filled the central area of the keep, which would have formed a possible gun platform in the mid 17th-century.
The trenches will be open to the public as part of an open day at Oxford Castle Unlocked on Sunday 2nd August.