Alverstone: The Site
The Alverstone excavation covered an area of some 1887 sq m, reaching depths of up to 4m. Most of the structural remains lay between 2 and 3m from the surface. The stratigraphy of the area is generally clayed alluvial silt, overlaying peat. In practical terms this meant excavation in very heavy, sticky and waterlogged mud which constantly flooded.
The area around the causway, in the direction that would have been down stream, is anomalous in that a large sand bar is present. The causeway structures appear to be associated with this old water way.
The modern stream bounds the site to the east.
Limited post ex has been undertaken to date, so interprtation is very much interim. The entire work was surveyed with a Total Station throughout, from which the following survey images were created. The first image shows the layout of the main wooden features. The second shows the position of all the vertical posts.
The third an interpretation of seven phases of causeway drawn from timber allignments. ∞ ∞
The main causeway appeared to have four phases of construction. ∞ The earliest shown in the picture is the cobbble surface over which lies a wooden track way. The track itself has three different alignments one of which may predate the cobbles (not shown here). To the right of the image, the cobble surface does not appear to have had a wooden track surface. The wooden track is shaped into a curve and changes alignment at this point. In the foreground a long term silting event can be seen between the cobbles and the upper trackway.
∞ This image shows the causway looking along its length. The wooden track does not appear to have overlain the cobbles in the foreground; the turn point mentioned above, is just infront of the blue barrel. The stack of buckets, in the foreground mark an area of small stakes running accross the track which appear to have been used to hold the cobbles at a slight gradient. It is possible to see that the cobbles are cambered towards left edge. The right edge; which lies upstream, has a steep edge and has a large accumulation of drift wood.
This image shows a cambered edge to the cobble trackway. The wood features here, which rest on the sandbar, have been interpreted as non structural driftwood. The sand bar does not apper to be present to the right of the causeway.
Once the wooden trackway was removed a ridge of cobbling was exposed. Excavation showed that the cobbles were arranged in irregular wooden frames along the centre, with outriggers consisting of a double post row, on both sides, interspersed with vertical stakes.
The next image gives some idea as to the arrangement of the stake and post rows. The are shown, is was under the cobble causway to the east, where the wooden trackway was not present. The double row of heavy posts gave way at this point to a more intence use of smaller stakes. A piece of squared timber can be seen in the foreground.
The last image shows one of the many posts being removed. The condition of the posts are as good as the day they were cot. The oak was yellow on removal from the clay and the faceted axe marks are clearly visible. Note how sharp the point of the stake still is.
| CBA, St Mary's House, 66 Bootham, York YO30 7BZ.
tel: +(44) (0)1904 671417 | fax: +(44) (0)1904 671384 | email: