Pedology

A day of archaeology in the peatlands of Ireland II

The view across Killaderry Bog. Co. Galway.

You can find part I of this post here.

Getting to the site

It’s a two hour drive from my base in Kildare to Killaderry, part of the trip is on the new Motorways built during the Celtic Tiger period but once you cross the Shannon these roads run out and you are back on the old single carriageways and narrow bridges that characterise the country.

The excavations

I Arrived at Killaderry, Co. Galway just after 11am and Jane Whitaker of ADS showed me around. These are raised bogs, which means they developed from ancient lakes. The natural vegetation has been removed by milling so they give the impression of solidified dark brown lakes. The only visible features are the long and deep drains extending into the distance that break up the bog into long narrow fields. The figures of archaeologists in reflective yellow safety gear can be seen beside shallow excavation cuttings filling out recording sheets. The trackways are spread around the bog and it takes a long time to walk out to them and then from site to site. This year 13 sites were excavated in Killaderry Bog and 3 in Castlegar. Dan Young from Reading University is busily taking samples from around the trackways for environmental analysis. When it rains this can be a bleak place as there’s no cover. In a hot summer there’s no shade from the sun. The peat dries out and can become airborne and tractors and harvesters create mini-dust-storms as they pass.

A section of a trackway prepared for environmental sampling at Killaderry Bog. Co. Galway.

The trackways have a wide date range from the Bronze Age right through to the fifteenth century AD. The longer trackways tend to cross the bogs at their narrowest points linking areas of dryland. In a number of cases trackways follow the routes that were established at earlier periods. There are other alignments of trackway that are being investigated this season that will soon be dated and will provide more detail. At this stage the evidence indicates that this routeway through Killaderry bog was in use for at least two thousand years and is probably the preserved wetland part of an ancient road network that existed in this area. Investigation of the nearby River Suck also has the potential to identify ancient fording points and possibly the remains of bridges. There have been interesting finds, a Late Bronze Age wooden shovel, a rough-out for a handled bowl and a spoon that resembles a chisel. Now that the season’s fieldwork has come to an end the next part of work, the post-ex phase, begins.

Final recording of cuttings and samples at Killaderry Bog. Co. Galway.


A day of archaeology in the peatlands of Ireland


View Killaderry& Castlegar in a larger map

About me
As an archaeologist my work ranges widely from advising developers how to avoid impacts on archaeology and built heritage, to the preparation of the cultural heritage sections of environmental impact assessments, to the commissioning of field-based investigations such as geophysical survey and the traditional archaeological excavation. Part of my professional work involves overseeing the archaeological programme of Bord na Móna, where I act as Project Archaeologist. Bord na Móna is the commercial Semi-state body with responsibility for the development of the Irish national peat resource. Bord na Móna owns and manages more than 80,000 ha of land spread across Ireland. Most of this is peatland which has preserved a wealth of organic archaeological and palaeoenvironmental material. Once thought to be areas of wilderness we now know that the bogs were used by people for thousands of years.

(more…)

Predictive Modelling for Archaeological Heritage Management

Marlies Janssens (Vestigia BV, The Netherlands) is analysing Dutch soils today.

Vestigia BV, a Dutch company, operates in the field of commercial archaeology primarily as a consultant to policy makers, project developers, spatial planners on the role of cultural heritage, archaeology and history, in corporate, social and sustainable development. Colleague Marlies Janssens is conducting fieldwork today, with the aim to test the predictive model that was constructed based on desktop survey.

“Six in the morning: no office outfit for today. I’d better wear an old pair of jeans and firmly tied shoes. Because in my job at an archaeological consultancy company I’m not only working at the office. Several days a month I’m out in the field all through The Netherlands.  Today is one of those days. Together with one of my colleagues, in a car filled with geological and archaeological equipment like hand corers, sieves and sample bags, we’re heading for the cover sand region in the province of Brabant, The Netherlands. The local authorities here have asked us to develop an indicative map of archaeological values that can serve as a starting point for their local policy on archaeological heritage management. To develop this map we’ve already been analyzing existing maps (like soil maps, historical maps, geological maps), known archaeological sites and archaeological databases. However, analyzing a landscape from maps and databases will always leave us with questions which cannot be answered by desktop survey only.  “What do the soil layers look like?”, “Can we see former landscape surfaces which might have been inhabited during the past? And if so, are these surfaces and soils still intact? Or have they been disturbed by recent human activities?” To answer these questions we’ll have to conduct fieldwork.

And that’s what is scheduled for today. We’ll visit several sites as part of a larger project where several colleagues, each with his or her own expertise, will aim to answer these questions. Today we will mainly focus on the landscape an soil characteristics, since me and my colleague are both physical geographers and approach archeology from the landscape point of view.

The first stop is at a site which is indicated on the soil map as an ‘enkeerd’ or plaggen soil. This man-made type of soil is often associated with late-medieval farming, when people added a mixture of heath sods and cattle manure to fertilize their arable land. By doing this year after year, they created a thick humic agricultural topsoil. These soils have a high archaeological potential; archaeological remains can be found within this plaggen cover (for the late medieval period), or underneath the cover (for older the period prior to that). After we’ve asked the owner for permission to enter his field, we start coring and find a thick humic sand layer. First, we think that this might indeed be the enkeerd soil as described on the soil-map, but while getting deeper, we start doubting whether this is really the medieval soil we were expecting to find. The humic layer looks very homogeneous, and the transition from the black topsoil to the yellowish cover sand  underneath it looks very sharp. Imagine this farmer ploughing his land, blending the black topsoils with the yellowish cover sand year after year. That probably won’t result in a sharp  boundary between the two layers. Furthermore, an older soil, which is often found underneath these man-made soils, is completely missing.  Looking at the landscape and noticing that this field is extremely flat and somewhat lower than the surrounding areas, we have to conclude that this soil has probably been disturbed recently and is leveled with black sand. Former surfaces or soils are missing, so the archaeological potential might be lower than we would have thought before.

The next coring, we had better luck. About a few hundred meters away from the previous site, we’ve found a podzol soil, which is still intact. These soils have been formed in cover sands since the start of the Holocene, about 10.000 years ago. This means that the surface we are standing on now,  is the same surface as the one people could have lived on  since the Stone Age.  Later in the afternoon we were also lucky enough the find a nice undisturbed enkeerdsoil, with remains of an older podzol soils underneath, meaning high archaeological potential for the complete range of historical and even prehistorical periods.

At the end of the day, after visiting some more sites in this cover sand region and several brook valleys, we’re heading back home again, feeling a bit tired from working in this very sunny afternoon, but also satisfied.  Actually seeing the landscape and the (sub)soils  in the field definitely gave us a better idea of the this area, which will help drawing up the archaeological document. Moreover, this was again one of those days that make me realize how lucky I am to have a job in archaeology that offers the opportunity to go outside and work in these lovely Dutch landscapes.”