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Practical Archaeological Excavation Techniques, day one

October 17th, 2008
post #129   history / prehistory »

An account of the first day on the Archaeological Excavation Techniques course run by Liverpool University Continuing Education in conjunction with National Museums Liverpool.

Monday 6th October 2008. Weather - Morning sunny with a light mist visible over distance. Overcast in the afternoon.


This was the first day the site had been opened since the Summer. Arriving at the farm at 0920, arrangements were made to get both people and kit down to the South-Eastern corner of the field where the current excavations are taking place. Wet weather in the previous week had prevented the potato harvest from taking place, a week’s dry weather being required before this can begin.

People and kit were loaded and moved by road to a roadside opposite the field corner, with access via a gap in the hedge beside the river.

Following a brief reiteration of health and safety procedures, we were given some additional safety and courtesy guidance for the site - such as taking care with tools when working closely together, walking clear of the edges of the balks between trenches, and the need to take notice of where we choose to dump spoil from barrows and buckets to ensure access and continued ease of site use.

We were then introduced to the site with a tour of the areas under investigation, those areas previously excavated and the features and finds they yielded. We were given the latest understanding of the site’s usage from Prehistory to Mediæval times and into the Twentieth Century and its relations to the landscape, nearby towns and halls.

Other areas of the field - where previous excavation had uncovered evidence of Iron Age settlement and a Roman trackway - were shown to us. The site’s popularity for periodic settlement may be explained by its proximity to the river and the presence of a spring.

The Western end of the site was notable for its mesolithic flint knapping waste through to examples of neolithic pottery - rare for this region. Moving down the slope East towards the river evidence of Mediæval settlement (possible structures, drainage ditches, pot sherds) had been uncovered, and it is at this end of the site that we were to begin our work.

Our first task was to reclaim the area we were to work on by clearing weeds and grasses that had grown since the last work was done. The balks around the South-Eastern corner of the site were cleared of surrounding weeds to faciliate access on all but the roadside. The sides of the trench were re-cut to give a clean edge. Plastic and geotextile coverings were removed from the immediate areas we would work on. As this work was done, any finds were placed in a tray marked with the trench number - in Roman numerals (Trench XVIA) . Such finds could come to lie in or around the open trenches and are recorded as ‘unstratified’.

The freshly cut trench edges were then used to demonstrate the site’s stratigraphy from modern farm layers down to the ‘blown sands’ of the Mediæval layers that had been discussed in the classroom. We were shown the subtle differences in colour, texture (and sound) when touched or trowelled. We were shown how to use sun and shade to help us to distinguish between the layers visually and to determine the layers as they appear in different trenches.

The site grid

The site plans shown to us are drawn onto tracing paper over gridded paper. Similar to the Ordnance Survey system, The site is given an origin in the South-West from which all measurements begin, and the Eastings and Northings from that point are marked permanently on waxed paper attached to nails periodically positioned across the site. Normally nails mark 5 metre divisions in each direction, with other being added as excavation progresses and plans are drawn. Sometimes the excavation topography will not allow regular intervals for grid nails, so they are placed and marked appropriately at the next nearest metre interval.

Plans

The plans we were shown of a previously opened trench show a portion of the whole site, marked with its origin co-ordinates. Thick grid lines denote single metre intervals, while their feint subdivisions count for 200mm intervals therein. Site features such as rocks had been marked on the plan, along with finds numbers and context numbers, which we were introduced to next.

Before commencing any trowel work within a trench, we were shown how the site was being recorded in terms of its depth and contents as opposed to its plan position. The whole site has a shorthand name and numeric code, trenches on the plan have their own numbering scheme, and context numbers are allocated to the features of a trench - this may be to describe a stratum uncovered or to describe the context of a post-hole, backfill or negative feature. Given their many uses, context numbers are allocated according to their features from a pre-printed sequentially numbered context sheet, allowing fast allocation on site. As the same stratum could be found across a whole site and in many trenches, the trench number is also recorded with the context number and details of the feature on the context sheet. A single feature may then have many context numbers. During the post-excavation stage, all of the trench-context information is combined to give a greater understanding of the site.

Finds bag from the sig siteFinds recording

Using these recording schemes we were shown the finds recording sheet and the methods used to record our finds. Finds may be recorded individually or in groups - a single, large pot sherd may be recorded individually while a number of far smaller pieces found in proximity to each other may be treated as a single find. Each find or group of finds is recorded in three places: On the finds sheet, on the site with a finds marker and nail, and on its find bag.

On turning up a find, its plan position in the trench according to the grid square (and easting/northing within it) are noted. The metre grid square is recorded as a whole number and more exact detail following a decimal point (*for example 2899.32E/ 1004.22N would represent 320mm East and 220mm North of the origin point of the grid square 2899E/1004N).

On the finds sheet a short description of the find (’Med Pot’ for example), the trench and context numbers in which it was found, the initials of the excavator and the date are recorded along with the exact Easting/Northing of the find alongside a pre-printed sequential finds number.

The trench number, find number, context number (and sometimes the E/N) are then recorded on waxed-paper using permanent marker and attached using a short finds nail to the point in the trench where it was found. This practice enables a planner to record on a site plan details of finds in the trench according to the context and other features of the site.

Finally, the same details are written onto a finds bag. The find is then placed in the finds bag and may be stored in a finds tray or at the point in the trench it was found to be collected at the end of the day. Leaving markers and finds in place makes them available for photographing in situ before work ceases.

On both the finds markers and bags, the find number is recorded within a triangle, and conventions exist for the position of the trench, context and co-ordinate numbers.

Commencing work

Each excavator was allocated a portion of Trench XVIA to work. Moving from the edge of the trench we had recut back towards the West, instructed to remove a small amount of material depth of the context we were working (number 2892). As the site had not been worked in some time this was to some degree to remedy the effects of animal disturbance and weathering, taking the context back to the state it had when last worked.

The context was described as a ginger sand layer, containing small pebbles and largely smoothed rocks. We could see the point at which this layer had culminated in the clean trench edge we had cut.

The area I worked contained darker patches of earth, which I was told could indicate organic material. While apparently regular and forming a rough rectangular shape the context still showed evidence of plough damage. This meant that further excavation - following recording - would be needed to show the extent of the feature before any sense could be made of it.

Bright orange patches in the context indicated the iron pans that had been discussed in class. These features could indicate water flow, and could add to the understanding of the other indicators of drainage ditches that appear to run across the site and this trench marked by discolourations, rock and pebble dispersions.

The day did yield some pottery finds, though not from my area. As the day drew to a close I followed the darker areas of the context, and the supervisor noticed a triangular terminal to one of them that could prove more interesting (possibly indicating a posthole) as excavation continued.



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