12 May 2014

Digging up the Geophysics at Oaklands Park

Readers of my blog will remember the magnetometry and radar at Oaklands Park, Sedlescombe. As well as the final report being published, some excavation has been going on, run by the Independent Historical Research Group. Just for a change, I was the site director! Despite thinking that geophysics is way better than excavation, this site provided a genuinely interesting archaeological question that only excavation could answer, which is whether or not the site was run by the Classis Britannica. It is an industrial scale iron working site, connected by iron-slag metalled roads to other Classis Britannica iron working sites and situated on what would have been a navigable river. The answer was surely yes and this could be proved by finding the special CL:BR stamped tiles that can be found on the sites that they ran. Here is the trench layout.

Trench Map. Click for a larger image

Trench A) This was the main trench. I was hoping the building shaped structure on the geophysics would turn out to be some sort of administrative building with a roof of CL:BR tiles. The walls appeared on both the magnetometry and radar, so I was expecting the foundations would be constructed of iron slag, which they were. Apart from that, things were quite different than expected. The feature in the centre of the building, which I had presumed was a central support was actually a trample layer. A smith had worn a shallow groove in the ground whilst standing at his anvil, leaving a thin layer of iron-slag, charcoal and hammer scale. The inner north wall (there are two) was quite substantial, being composed of layers of iron slag, on top of which a wooden building would have stood. The outer north wall was more slight and was most likely a lean-to against the main building. This only went half way across the trench from the east, so the entrance to the building may have been here. Unfortunately, the floor layer of the building had been ploughed away, but the lack of floor material and the trample layer in the centre of the building suggest that the floor was bare earth. No tiles were found in the area, so the building most likely had a wooden shingle roof. The identification of the building as a smithy raises further questions, such as what they were making. It may have been as simple as hammering the raw blooms into a shape suitable for export. On the geophysics, the middle of the southern wall of the building shows a strong feature jutting slightly into the building. This is most likely the forge.

A slot through the inner north wall in Trench A

Trench B) The original purpose of trench B was to target what seemed to be a pile of moderately magnetic material to the west of the smithy, in case a tile roof had been stripped and dumped to one side before the building was robbed, which the radar suggested had happened on the west side. The results of the excavation were slightly different. At the lowest level, at the level of the natural, some stake holes were found. The remains of a burnt plank was found resting on top of the natural. On top of this, a layer of redeposited clay and earth mixed together was dumped, presumably to level the area out in order to construct a wooden building on top. Unlike the main building, there was no foundation, just a beam slot and some postholes cut into the redeposited clay. On top of this, a destruction or occupation layer filled with charcol  contained a lot of pottery and iron slag. The form of the building is unclear given the small area sampled, but it is more flimsy than the smithy.

A complete pot found at the bottom of the occupation layer in Trench B

Trench C) This trench targeted a massive pit feature, about 35m x 10m, to the north of the smithy. The radar suggested that it was lined with a lense of dense material and it was hoped that some tiles had found their way in. The very deep (1.5m) test pit found pretty much what was expected. The bottom of the pit contained thin layers of burnt clay, slag and charcoal, unfortunately tile free. Above this was a very thick layer of silt, presumably because the pit filled with water, followed by a layer of hillwash with a much greater clay component. The natural here was a very clean clay. As this massive pit was only partially filled with rubbish and lacked any iron stone in the natural (the quarries for the iron stone were at the top of the hill), the quarry was most likely for the extraction of clay to build the bloomeries. To further vex us, we found a modern cable and a land drain cut without a land drain in it.

Trench C: Hello down there!

Trench D) After quickly exhausting the first 3 planned trenches much quicker than anticipated, thoughts turned to what to do next. I toyed with the idea of opening up a huge trench over a large (3m x 7m) bloomery, but decided against it, as that would not have furthered the research question. It was decided to further sample other parts of the site in the hope of finding the CL:BR stamped tiles, so trench D never happened.

Trench E) This trench was in a similar massive pit to trench C, but within the rectangular enclosure to the north-east, near the well. This quarry was 20m x 10m and the test pit found a similar thin layer of material at the bottom, but this time composed entirely of burnt clay from a destoyed bloomery. Below this layer was a thick layer of redeposited clay with little in it apart from pottery at the very top. We never reached the natural. Unlike the quarry at trench C, this quarry did not silt up due to being filled with water but was filled with hill wash.

 Some of the burnt clay layer in Trench E

Trench F) This trench targeted the main slag heap against the northern edge of the field. It was recorded that coins and other occupation material had been found in the slag heap as it was being removed for road building, so it was hoped that some tiles would be found. After about a metre of topsoil that had been ploughed down the hill, the slag bank was reached. It was black with charcoal and contained few finds, with only two pieces of pottery being found in 30cm of excavation. It was decided to close this test pit before the slag heap bottomed out.

 Trench F. Nothing to see here, move along.

Trench G) Targetting a different feature type and a different part of the site, what looked like a rubbish pit on the geophysics, about 2 metres wide, was half sectioned at the western end of the site. It did indeed turn out to be a rubbish pit as expected, with a huge amount of pottery in a black charcoal layer at the bottom. There was a dump of burnt clay on top of this on one side of the pit follwed by a silting up of the feature and some sandstone blocks being dumped near the top. There was quite a bit of post-medieval tile in the plough soil above the feature, but no Roman tile in it unfortunately.

A partially excavated Trench G

We didn't manage to prove the site was Classis run by finding their stamped tiles, but we found out a lot about the site while we were looking. Finding a Roman site with so few tiles of ay sort is quite an oddity in itself. A big thankyou must go to Pestalozzi for letting us dig up their land. Thanks to all the diggers, especially Robin, Brian and Cameron for all their sterling work.

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