Soil

Core blimey! Jason Stewart and the Sediment Core Samples

The best thing about working as a geoarchaeologist at MOLA is the variety; one day I could be watching a machine ripping through the odorous remains of a 19th century gas works, the next day could find me wrestling with the implications of a newly returned set of radiocarbon dates.

Today however finds me in the lab examining sediment cores retrieved from an evaluation. The site is in Dartford within the Thames estuary and has early prehistoric peat forming on top of the cold climate landsurface with various phases of being mudflat, marshland or flooded.

The cores are carefully laid out with the top of the borehole at one end of the lab and the base at the other. As there is 16m of sequence and the cores are 1.5m long and filled with heavy sediment this can take longer than you would think.  The cores are then methodically cleaned and the colour texture, inclusions and nature of the boundaries are recorded.  This detailed cleaning and logging allows me to think about the depositional environment of the site and the nature and rate of the changes that occur.

The next task is to select the locations from which to take samples, we take samples for radiocarbon dating, this enables us to places the changes in environment in some kind of chronological framework allowing us to compare the developments onsite with other work we have done in the surrounding area.  We also sample for things which will tell us about the environment in the past (usually pollen, diatoms, ostracods and plant remains).  These are carefully sliced from the core and sealed in labelled bags to be sent off to the various specialists.  The cores are then re-wrapped and returned to their climate controlled environment, the lab surfaces cleaned and the results typed up.

Jason Stewart

Discovering Dumfries and Galloway’s Past

Well, hello from a soggy south-west Scotland. I’m Giles, Development Officer for Discovering Dumfries and Galloway’s Past and I wanted to tell you on Day of Archaeology 2012 about the project and what we are going to be doing over the next week or so…

DDGP is an exciting new community archaeology project based in south-west, providing training in using geophysical survey to help volunteers record, understand and interpret the region’s fascinating archaeology. There’s going to be plenty of opportunity for local people right across the region to get involved in the surveys – it’s a great way to find out more about buried archaeology without having to excavate.

What is geophysics, and what can we find out using it?

Not all archaeology is about excavation – you may have come across ‘geofizz’ on TV’s Time Team where it’s often used to plan where to put the trenches in. Geophysics is a way of mapping buried archaeological deposits – be they ditches, pits or building material – without ever breaking the ground surface.

There are two main techniques for geophysical survey:

Glasgow University archaeologists undertaking resistivity survey

Resistivity: By passing a small electrical current into the ground, and measuring the amount of resistance that results, it is possible to locate buried remains of archaeological interest.

Resistance is related to the amount of moisture in the soil. Around buried walls, for example, the surrounding soil will often be dryer. The current cannot pass so easily through this dry soil, so stonework can often show up as areas of higher resistance. This technique is therefore ideal for locating building walls and foundations.

Glasgow University archaeologists undertaking magnetic survey

Magnetometry:  This technique detects extremely small variations in the earth’s magnetic field, caused when the ground has been disturbed by previous activity. Burning, for instance, will often leave a significant magnetic trace.

Magnetometry is excellent for locating ditches, pits, middens, hearths and kilns – and is great at covering large areas quite quickly.

The great thing about geophysical survey is that the results can be rapidly downloaded on site to a laptop, and even with minimum processing it is possible to define ‘anomalies’ which can represent buried archaeology. For volunteers on the project surveys this is great – they can see the fruits of their labours in the field. We are aiming to get these very quickly into reports which will be uploaded onto our website, to share them with as wide an audience as possible.

Our next survey
It’s all a bit hectic in the office today as we put the finishing touches to our programme for next week’s survey. We’ll be undertaken both magnetic and resistivity survey at the nationally important site of the Roman fort at Birrens. This continues work that the University of Glasgow have been concentrating on – looking in and around Roman military sites in Eastern Dumfriesshire.

Magnetic survey results around Bankhead Roman fort, Dalswinton

This has looked at fabulous sites around Lockerbie, such as the Roman fort at Dalswinton. As you can see this has added loads of detail (as you can see on the right) to both the inside of the fort of Bankhead and the surrounding area – which aerial photographs have shown to be really interesting.

At Birrens Roman fort, near Middlebie, we’ll be focusing on similar things. A group of 6 volunteers will be joining us for 3 days next week to carry out some resistivity survey on the interior – hopefully we’ll get detail of the street pattern, as well as an idea of how the buildings – both the barrack blocks and administrative headquarters of the fort – were laid out.

You can find out more about Birrens fort – known to the Romans as blatobulgium (literally the ‘flour sack’) here.

We’re having an Open Day on Saturday July 7th – it’ll be a great chance to show the public the results as well as an opportunity to show just how geophysics ‘works’ – including the amount of walking in straight lines that’s involved! The response has been fantastic locally – so here’s hoping for some sunshine!

I hope this has wet your apetite both for ‘geophysics’ and the project – please see our website to keep up to date with the latest – discoveringdgpast.wordpress.com.

The project is jointly funded by the Scottish Government and The European Community, Dumfries and Galloway Leader 2007-2013; The Crichton Foundation and The University of Glasgow.

Archaeology: Watching Other People Dig

It’s an early morning for me, earlier than usual. I have two archaeology jobs these days – one as the webmaster for archaeologyfieldwork.com, and also my full time job working for a government agency in the northeast US. I wake at 4am and have just enough time to post some new archaeology jobs to the website, then it’s a quick rush to get ready for work!

I am adhering to the schedule of a subconsultant doing work on our property. An environmental company is planning a soil remediation project, essentially stripping away dirt that has tested as contaminated, and removing it from the site. Generally one thinks of archaeologists as the ones doing the digging, but today I will be watching someone else digging.

This is only my second week on the job, and the first time I’ve been in the field in a long time. I’m still learning the ropes at my employer and figuring out the right people to talk to, where to look up information, and even mundane things like where various equipment is located.

I’ve gathered the requisite equipment and spent time mentally preparing for the job at hand. Before you go into the field, there are certain steps that need to be taken. Part of the process is doing research on the area where you will be working. I needed to figure out what previously recorded archaeological and historical sites were in the vicinity of the project area, and what was found. Geographic information system (GIS) maps and site files are consulted in the search. Soil survey maps are also studied and can provide something of a preview of what you can expect to encounter. It’s important to also know the topography of a project area – is the landform flat, a severe slope, a hilltop? Related information is also important such as proximity to a water source (including seasonal water sources, or even one that existed only in the past). Some predictive models have been developed using those factors and other criteria to provide an educated guess on where sites may be found. Knowing something about the history of an area is also helpful. Is the project area near known Native American trails, or historic routes? Were structures present? What do we know about land use here in the last few hundred years? Archaeologists try to arm themselves with as much information as possible before an excavation ever occurs, however, you really don’t know what’s out there until you conduct fieldwork.

I did my homework, packed my truck, and headed out to the site to meet the contractors. I’m usually a bit obsessive about being early, but following a slow moving dump truck on dusty roads for miles and miles, I show up just on time. The contaminated soil is in association with a historic structure whose foundation remains. The contractors spend a bit of time debating the various methods of removing the soil, and I busy myself taking measurements  and photos of the ruins and proposed excavation. Nothing too exciting here from an archaeological perspective, even for someone enamored of historics like myself. Poking around the fill in the foundation turns up a few modern artifacts – sewer drainage pipe, PVC plumbing and plastics.

The excavator begins to strip the top few feet of soil, which is recent fill. I find a dark colored lens with charred wood in the excavated wall, likely a modern burn episode. The excavator operator is a local and informs me this is where trash was sometimes burned behind the structure. I ask more questions about the surroundings and compare the info given with my previous research. It’s often beneficial to hear what folks have to say, and sometimes you can obtain useful information. Any archaeologist who has been working in the field long enough can tell you stories about how a local informant clued them in to what was really going on (and usually where the real sites were).

The excavation comes to a halt, as there is a delay in bringing containers on site from another contractor. After spending time waiting for the containers to show up, the decision is made to cease operations for the day. I pack up and drive back to the office to write up my notes. The containers may not be arriving until next week, so I shift my attention to the next project and put this on the back burner for now. Shovel testing is planned for Friday at another site, and I need to complete my research before heading out. And so the cycle begins anew. Onto the next project!

Writing a press pack for the British Science Festival

I’ve spent most of today writing the press pack for the British Science Festival. Engagement with journalists is important. Journalists provide the opportunity for you to get your information out to a wider audience. The challenge is to take complex data and interpretations and find a way to present it to journalists in a way which is both accessible and allows them to weave a narrative which is interesting to their readers.

Here it is….  Apologies to those who do other archaeological prospection work: you may think it’s a bit biased towards aerial approaches. It is, but that’s the very issue for a press release.

This draft will be sent through to the University of Leeds press office prior to submission to the British Science Festival.

The Electromagnetic Spectrum. Re-used under a creative commons share-a-like licence from DART_Project.

The Electromagnetic Spectrum. Re-used under a creative commons share-a-like licence from DART_Project.

I’m sure I left it somewhere: discovering our heritage through scientific prospection

Anthony Beck – School of Computing, University of Leeds

A presentation for the British Science Festival in Session 56: Exploring new archaeological worlds, 12 September 2011.

Can you provide a brief introduction to the topic of your presentation?

Guidance: This should be more than an abstract or one-paragraph summary of your research. We would anticipate the summary of your presentation to be in the region of 1000 – 1500 words. Two to three sides is ideal. It is an opportunity to introduce the main findings of the work/research described in your presentation, as well as to include relevant background information and to fit your work within the wider context. It should contain specific information (e.g. data, number of people included in any studies, etc) that would enable a journalist to accurately write a story about your work, without them having to hunt around for details elsewhere. Due to time constraints journalists are rarely able to attend the talk itself, which is why press papers are so important – therefore the details you provide shouldn’t assume that the journalist will be attending your talk.

Summary/Abstract (174 words): Multi-spectral and hyper-spectral sensors offer immense potential as archaeological prospection tools. The sensors are sensitive to emitted or reflected radiation over different areas (wavelengths) of the electromagnetic spectrum. Their two major advantages are that they have the potential to detect archaeological sites and monuments (henceforth archaeological residues) that are undetectable in the visible wavelengths and that they may extend the window of opportunity for their detection. For example, localised crop stress and vigour variations, which underpin crop-mark formation, are sometimes better expressed in the near-infrared than in the visible. In addition, multi/hyper-spectral data collected from different platforms (aerial and satellite) under different conditions can be used to generate ancillary themes that aid interpretation (e.g. soil, geology and land-use layers). However, multi/hyper-spectral sensors are relatively expensive and require systematic surveys under ‘appropriate conditions’ in order to be successful. It is this latter point which is critical: there is a poor understanding of the spatial, environmental and seasonal contrast dynamics that determine an ‘appropriate condition’ and therefore whether features of archaeological interest can be detected.

Text (1423 words): Although there are many examples of upstanding architecture, the vast majority of archaeological residues are expressed on the ground surface or buried and essentially invisible to the human eye. However, traces can be identified via changes in chemical, physical and biological attributes (either directly or by proxy) through, for example, changes in phosphorous content, clusters of artefacts and cropmarks. In the UK, the practice of using remote sensing techniques for detecting archaeological sites and visualizing archaeological landscapes has traditionally been based on low altitude aerial photography using film emulsions sensitive at optical and sometimes near-infrared wavelengths. The underlying premise of remote sensing is that interpreters can extract information about objects and features by studying the measurements from a sensor system. Both oblique and vertical aerial photographs have been used extensively for archaeological reconnaissance and mapping all over the world. Early aerial photographers helped to refine the instruments and establish methods that are still in use today. O.G.S. Crawford in particular established methods of site classification and wrote about the effects of weather, season, soil moisture and crop type on photographic return. Today, these aerial approaches are accepted as a cost-effective, non-invasive technique for the reconnaissance and survey of monuments.

However, recording using traditional observer directed reconnaissance and aerial photography is not without its problems. The reliance on a small component of the electromagnetic spectrum raises a number of issues. The small spectral window can introduce a significant bias as only certain residues under specific conditions express contrasts in these wavelengths. The over-reliance on the visual component of the electromagnetic spectrum has had a significant impact on data capture. The collection technique and technology mitigate against using any other sensor (peripatetic surveys are directed by visual observation from a plane and collected using an optical system, a camera out of a window: this technique will never allow the detection of the multitude of archaeological residues whose contrast expression can not be seen by the human eye – i.e. is outside the optical).  This presentation will introduce multi and hyper-spectral remote sensing (including the important resolving characteristics of the sensors) and the nature of the archaeological problems to which they can be applied. This is followed with a brief description of the DART project: a UK research project designed to improve the understanding of the application and the factors underpinning archaeological detection.

The main advantage to multi and hyperspectral imaging is that more of the electromagnetic spectrum is sampled at potentially finer spectral granularity; hence, there is more information about the objects under study. The main disadvantages are cost and complexity.  Unfortunately the archaeological application of this technology is under-researched: there is little understanding of the physical, chemical, biological and environmental processes that determine whether archaeological residues will be identified in one or any sensor. Hence, knowledge of which techniques will detect which components of the archaeological domain and under what conditions is poorly understood. Most multi and hyperspectral analysts use spectral signatures to accurately identify different vegetation and geology types. Unfortunately archaeological sites do not exhibit spectral signatures that can be used for generic detection purposes. Archaeological sites and features are created by localised formation and deformation processes. For example, as a mud-brick built farmstead erodes, the silt, sand, clay, large clasts and organics in the mud-brick along with other anthropogenic debris are incorporated into the soil. This produces localised variations in soil particle size and structure. This impacts on drainage and changes localised crop stress and vigour responses, which in turn changes reflectance characteristics.

Multispectral sensors address some of these problems because they are able to ‘look’ simultaneously at a wide range of different wavelengths. Wavelengths in the near and short-wave infrared add important collateral information to the visual wavelengths and improve the ability to discriminate vegetation stress and soil, moisture and temperature variations than either the human eye or photographic film. Narrow band spectral imaging can often help to enhance or distinguish different features on the ground or provide information on their state of health or ambient conditions according to their particular absorption and reflectance properties or their spectral signature.

This increased sensitivity is crucial for contrast detection. For example, cropmarks are an instance of localised variations in vegetation stress or vigour correlated with subsurface archaeological features. Wavelengths outside the visible are also sensitive to changes in vegetation health. Theoretically, exploiting relevant areas of the electromagnetic spectrum at the appropriate degree of granularity will mean that crop stress or vigour relating to subsurface archaeological residues can be expressed  more clearly and also that it can be detected both earlier and later in the growing cycle. Therefore, the window of opportunity for detecting archaeological features can be dramatically extended by using wavelengths outside the visible. This increased sensitivity means that archaeological contrasts can also be detected in soils and crops that have been traditionally categorised as marginal or unresponsive to aerial archaeological prospection. This is a significant improvement over traditional techniques.

We can hypothesise that archaeological residues produce localised contrasts in the landscape matrix which can be detected using an appropriate sensor under appropriate conditions. However, little is known about how different archaeological residues contrast with their local environment, how these contrasts are expressed in the electromagnetic spectrum, or how environmental, and other localised factors such as soil or vegetation, impact on contrast magnitude (over space and time).   This requires an understanding of both the nature of the residues and the landscape matrix within which they exist.

The Detection of Archaeological residues using Remote Sensing Techniques (DART) project (www.comp.leeds.ac.uk/dart) will focus on analysing factors that influence archaeological residue contrast dynamics. DART aims to determine how different remote sensing technologies detect contrast caused by different underlying factors under dynamic environmental conditions. This understanding will allow the optimal deployment of the different sensors.  By combining the results from a battery of sensors, each optimally deployed when the archaeological residues have the greatest likelihood of being detected, the maximal knowledge of archaeological residues can be achieved.

DART will address the following research issues:

  • What are the factors that produce archaeological contrasts?
  • How do these contrast processes vary over space and time?
  • What causes these variations?
  • How can we best detect these contrasts (sensors and conditions)?

The key will be to understand how archaeological residues differ from, and dynamically interact with, the localised soils/sediments and vegetation/crop and how these differences can be detected. Archaeological residue interaction models will be developed and tested under a range of different environmental, seasonal and crop conditions. In-situ measurements will be taken using probes and sensors, and samples will be taken for laboratory analysis. Standard geotechnical tests will be conducted such as density, grain size distribution, organic content, magnetic susceptibility, dielectric permittivity, geochemistry, pH and conductivity. Permanent in-situ probes will measure temperature gradient, density and soil moisture variations through a soil profile. In addition, each site will be visited regularly for measuring earth resistance, soil colour, conductivity, dielectric permittivity, hand-held spectro-radiometry, GPR transects and ambient climatic data. Traditional aerial flyovers and bespoke hyperspectral surveys will be commissioned.

Remote sensing can provide an impressive picture of the archaeological landscape without the need for invasive or expensive survey methods. The true potential of multispectral remote sensing, including thermal imaging, is still not clear and needs to be evaluated to test responsiveness under a broad range of climatic and ground conditions. Further research is likely to produce sensors capable of resolving relatively small features such as post-holes and shallow pits. When used appropriately, remote sensing provides a basis for testing hypotheses of landscape evolution that may be further explored by ground survey, geophysical survey or excavation. Large-scale airborne and satellite surveys can provide the framework on which planning policy and excavation strategies can be established. In addition, computer enhancement and the increased spectral resolution of the digital data places less dependency on the time of year for revealing archaeological features.

Remote sensing is increasingly important to many areas of archaeological enquiry from prospection through to management. It is therefore essential that it is not applied inappropriately. The inappropriate application of a single sensor could produce minimal results or the dogmatic application of that sensor will have diminishing archaeological returns. The combination of different sensors with different characteristics can produce profound interpretative synergies. Multiple sensors should be evaluated on the basis of ‘fitness for purpose’. Fitness for purpose in this context refers to the cost/benefit returns of each sensor and should be based upon an understanding of the nature of the archaeological residues, the sensor characteristics and the environmental characteristics of the landscape

What is new and interesting about your work?

Guidance: This should clearly summarise the main conclusions of your work, the key findings. This helps journalists (and the British Science Association Press Office) quickly identify key outcomes and is an important section to fill out. I’d suggest 100-200 words for this section.

Text (338 words): Geophysical and Aerial survey have substantially increased our understanding of the nature and distribution of archaeology remains. However, there is variable understanding of the physical, chemical, biological and environmental factors which produce the archaeological contrasts that are detected by the sensor technologies. These factors vary geographically, seasonally and throughout the day, meaning that the ability to detect features changes over time and space. This is not yet well understood. The DART project is a three year AHRC/EPSRC funded project with 25 partners from a range of disciplines.

Detection techniques rely on the ability of a sensor to measure the contrast between an archaeological residue and its immediate surroundings or matrix. Detection is influenced by many factors – changes in precipitation, temperature, crop stress/type, soil type and structure, and land management techniques. DART will increase the foundational knowledge about the remote sensing of sub-surface archaeological remains. To determine contrast factors, samples and measurements are taken on and around different sub-surface archaeological features at different times of the day and year to ensure that a representative range of conditions is covered. Field measurements include geophysical and hyperspectral surveys, thermal profiling, soil moisture and spectral reflectance. Laboratory analysis of samples includes geochemistry and particle size. This will result in a comprehensive knowledgebase.

During analysis the key will be to understand the dynamic interaction between soils, vegetation and archaeological residues and how these affect detection with sensing devices. This requires understanding how the archaeology differs from, and dynamically interacts with, the localised soils and vegetation and how these differences can be detected.

DART is an Open Science project. Open science is the idea that scientific knowledge of all kinds should be openly shared as early as is practical in the discovery process. By scientific knowledge “of all kinds” we include journal articles, data, code, online software tools, questions, ideas, and speculations; anything which can be considered knowledge. The “as is practical” clause is included because very often there are other factors (legal, ethical, social, etc) that must be considered prior to opening access.

What is the key finding of the work/research described in your presentation?

Guidance: What is it that would make someone sit up and listen? One way to approach this question is to imagine that you are talking to a journalist about your work – what are the key pieces of information that you would want to convey? Please do fill this out. Even if there is no ‘new’ research in your presentation, what message do you wish to convey, or what new angle will you present? Remember that whilst the research may not be new to you, there is every possibility that the journalists won’t have heard it before. I’d suggest 100-200 words for this section.

Text (317 words): The DART project is producing foundational research which will ensure that heritage/archaeological curators and policy makers are prepared for the challenges of the 21st Century and beyond. Current landscape detection techniques can be either too small scale or biased. For example, traditional aerial survey is biased in that it is mainly responsive on well draining soils. This means that difficult environments, like clays and pasture, have not been targeted. It is also possible that after a century of flying, in different environmental conditions, a point of saturation has been reached: no previously unobserved features are being detected – this does not mean that there are no new archaeological residues to discover, rather that no more can be detected with that particular sensor configuration. The DART knowledgebase will allow more effective decision making and management.

This work is particularly timely given the advances made in precision agriculture remote sensing and the application of Unmanned Aerial Vehicles (UAVs). Precision agriculture approaches are being used to increase yield by regulating crop growth to ameliorate extreme and non-ideal conditions (the very conditions under which ’never before seen’ archaeological features are observed). Advances in precision agriculture have the potential to significantly reduce the overall impact of traditional aerial archaeological approaches. An understanding of the underlying processes and dynamics in key crops and soils will help policy makers understand the potential impact of these developments and so determine curation and land-management policies more effectively. This will underpin the development of a framework for improving the detection of archaeological features through the more complete understanding of soil change, species phenology and the impact of different stress conditions on detection.

As an alternative: we have managed to exploit the new technology during the driest spring in Cambridgeshire since 1910. Whilst we are still analysing the results, the hyperspectral images have the opportunity to revolutionise our understanding of the buried landscape particularly in the clay areas.

What is the relevance of your work to a general audience?

Guidance: Think about in what way(s) the work is relevant to the general population, why it’s important. I’d suggest including around 100-200 words for this section.

Text (153 words):   The DART project is all about improving the underlying knowledge about process so that more archaeology can be detected. This will lead to better information and knowledge (for the public, for industry and for managers), which will lead to better decision making and policy formation.

In addition the DART Project is an Open Science initiative. Where practicable all science objects (data, algorithms, illustrations etc.) will be made openly available. An open license means that the outputs can be reused in a broadly unfettered way (be that for research, teaching and learning, personal edification etc.). Initiatives like Open Science in conjunction with the internet and social media are changing the research landscape. Research is become ever more open and collaborative. Consumers of research are participating in a conversation, not listening to a lecture. This more sophisticated form of engagement can increase impact and engagement dramatically. This will significantly change the way universities ‘do business’.

DART sidetracked


Day Of Tweed

Day Of Tweed

Inevitably you get sidetracked…..

DART is burying temperature and soil moisture sensors at our test sites that take readings every hour or so. The data from these sensors will feed into soil and other models so we can get a better understanding of thermal emmisivity characteristics, soil-water percolation etc. and how this impacts on contrast identification and therefore the detection of archaeology. Most of these probes are bespoke units developed by the University of Birmingham. In order to test the veracity of these systems against an ‘off-the-shelf’ system we are collaborating with Van Walt Ltd to install their ‘off the shelf’ temperature and moisture arrays.

On Monday we will be installing the Van Walt sensors at our site in Cambridgeshire. Consequently I need to ensure that the last-minute logistics are sorted out and the programme of works is understood by all. Dr. Keith Wilkinson, our geoarchaeologist, set out the trench and borehole locations earlier today.

In addition we will be installing the Birmingham sensors in the same area in the week commencing 22nd August 2011. I have just booked the machine which will excavate and backfill the trench.

I also note that other people have put picture of themselves up. So….. here’s one of me. Today is a Tweed Friday and some stereotypes are worth maintaining! Unfortunately I have evolved in a way which precludes the growing of fancy facial furniture. I am therefore beard-free.

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.”