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SOIL AND ARCHAEOLOGICAL The case study GROUNDWORKS FOR of Assebroek LANDSCAPE DEVELOPMENT PROJECTS OF THE FLEMISH LAND AGENCY C. Ampe1 K. Gheysen1

¹ Vlaamse Landmaatschappij, regio West,

Corresponding author Carole Ampe, [email protected]

abstract This paper describes the preliminary soil and archaeological research carried out by the Flemish Land Agency, to achieve a well substantiated project design. At the circular structure of Ver-Assebroek (), the site of a former medieval castle, a landscape development project aims to increase the visibility of the structure while respecting the soil values and archaeological structures on the site. keywords circular structure, peat, limnic material, land development project doi 10.5281/zenodo.3421067

SOILS AS RECORDS OF PAST AND PRESENT. FROM SOIL SURVEYS TO ARCHAEOLOGICAL SITES: RESEARCH STRATEGIES FOR INTERPRETING SOIL CHARACTERISTICS Proceedings of the Geoarchaeological Meeting, Bruges, 6 & 7 November 2019. Edited by J. Deák, C. Ampe and J. Mikkelsen. © Raakvlak 308 SOILS AS RECORDS OF PAST AND PRESENT. FROM SOIL SURVEYS TO ARCHAEOLOGICAL SITES: RESEARCH STRATEGIES FOR INTERPRETING SOIL CHARACTERISTICS

1. Introduction to complete the missing links between the green spaces of the cycling network encircling the city. A land develop- In Ver-Assebroek (Bruges, Belgium) a large man-made ment plan was agreed between different governmental circular structure is positioned on the edge of humid partners, town councils, farmers, NGO Natuurpunt, and meadowlands (Assebroekse Meersen) and a dry sandy the Water Board (polder). At Assebroekse Meersen the ridge on which the church of Ver-Assebroek is located. measures consist of restoring the nature values of the hu- Ameryckx (1955) was the first to describe this structure mid meadowlands by improving the water management in detail. During the ’80s, the site was further examined system and securing the future of the archaeological site by De Meulemeester (1981), Soers (1987) and the Univer- through visualisation and maintenance. sity of (UGent) and afterwards a multi-disciplinary research (combining historical, geophysical, soil and ar- chaeological analysis) was contracted (Ryssaert et al., 2. Study area 2010) by the Flemish Government in preparation of the protection of the site as an ‘archaeological zone’ (2012). The circular structure of Assebroek is located on the edge The meadowlands and the archaeological site are of a large basin-shaped depression (called Assebroekse part of a land development project called ‘Groene Fiets- Meersen) that lies between 3,75 and 5 m TAW (m a.s.l.) gordel’ (VLM, 2009). The project aims to increase the south of a cover sand ridge with altitudes of up to more quality of the ‘green belt’ around the city of Bruges and than 10 m TAW.

Figure 1. Location of the Assebroekse Meersen in West-Flanders, Belgium and the digital height model (Digitaal Hoogtemodel Vlaanderen II, 2013) showing the four circles of the archaeological site. SOIL AND ARCHAEOLOGICAL GROUNDWORKS FOR LANDSCAPE DEVELOPMENT PROJECTS OF THE FLEMISH LAND AGENCY 309

The Assebroekse Meersen have a very specific The aim of the landscape restoration project is to landscape position within the Sandy region. They are optimise the water management (both water quality and part of the ‘Zuidbrugse dallandschap’ (Deduytsche, quantity) on the archaeological site and in the meadow- 1974), a wide basin-formed depression south of Bruges in lands. The project will also improve the visibility and ‘read- which different valleys convene. During the Late Glacial ability’ of the circular structures and the landscape of the period the cover sands were reworked to a broad cover archaeological site. sand ridge from Gistel to Stekene (De Moor and Heyse, 1978) obstructing the river systems. At the Assebroekse Meersen a palaeolake was formed and filled with lake 4. Material and methods marl sediment. The lake evolved to a swamp and in due course peat developed (soil series V) (Soil map of Bel- The study of the soil and ecology by the VLM and the in- gium, Brugge 23W, MGI, 1958). The soils and former hy- ventory of the archaeological structure formed the basis drological conditions form a very suitable environment of the project design. At the same time, Ryssaert et al. for the development of Calthion palustris grasslands. (2010) collected historical data and soil data by augering, The circular structure of Assebroek consists of 4 geophysical survey and 3 trenches in preparation of the concentric ditches separated by banks. The inner ditch is designation of the site as a protected heritage site. up to 40 m wide, the second 20 m, the third and fourth In order to refine the data, additional research by only 7 m. The outer circle has a diameter of 260 m. The VLM was necessary. Soilscape research through auger- concentric ditches surround a central platform mound ing consisted of 10 transects in a radial pattern according with a diameter of approximately 50 m (Figure 1). The to the terrain conditions starting from the centre of the platform was elevated by sand and held a castle in the archaeological structure. Augerings were placed every 10 form of a fortified house or tower. The site was built in m as long as profiles were intact. Distances in between the 13th century, but already abandoned at the end of the were shortened to 0,5 m whenever the profile morphol- 15th or early 16th century (Ryssaert et al., 2010). The ar- ogy changed. Each augering was located by dGPS and chaeological findings in the ditches are covered by peat, combined with the digital height model (Digitaal Hoogte- which suggests water saturation conditions after the model Vlaanderen II, DSM, raster, 5 m; 2013) and an eco- abandonment of the site. In the 19th century the area was logical recording. Soil profiles were described according remediated for agricultural use. New parcelling was ap- to FAO guidelines (2006). plied, ditches were dug and the mound, banks and his- torical ditches were levelled. In 1863 a tramway was con- structed through the site. 5. Results

The digital height model (DTM) (Digitaal Hoogtemodel 3. Aim of the study Vlaanderen II, DSM, raster, 5m; 2013) was used for an easi- er location of the structures on the field. By manipulating The interdisciplinary approach has two objectives: restitu- the height interval, it became possible to recognize the tion of the original ecosystem and a visual representation ditches of the archaeological structure and the ditches of the archaeological site. and drainage ditches of the 19th century parcelling pattern. The main bottlenecks for the preservation of intend- Across the structure the track of the tramway runs with ed habitats in the meadowlands are 1) excessive drainage different elevated access ramps to the parcels. in summer causing deep groundwater tables and degra- The soil – landscape research by augering resulted in a dis- dation of the peat; 2) flooding during winter with nutrient tinction into 3 soil units: rich water from polluted ditches; 3) spilling over of excess 1. Natural profile: the substrate is formed by Eemian water on the meadows of the sewage system after heavy sediments. On top of these are limnic sediments with rainfall; 4) changes in the last decades towards a more in- gyttja in the lower part and marl in the upper part tensive agricultural use of the meadowlands. (Figure 2). The surface horizon consists of peat (dated Additionally, the visual observation of the archaeo- on the site between approx. 1750 – 1400 BC, Ryssaert logical site of Assebroek is at present very difficult. The mi- et al., 2010). This peat was probably exploited in medi- crorelief of ditches and banks is hardly observable. Heavy eval times, and most likely this horizon was originally trampling by cattle, drainage by recently made ditches thicker. Towards the sandy ridge in northern direc- cutting through the site, and the tramway track splitting tion, the surface horizon gradually changes from peat the site in two are the main causes for the decreased visi- to clayey to sandy material, and the thickness of the bility of the site. marl gradually peters out towards the sand ridge. 310 SOILS AS RECORDS OF PAST AND PRESENT. FROM SOIL SURVEYS TO ARCHAEOLOGICAL SITES: RESEARCH STRATEGIES FOR INTERPRETING SOIL CHARACTERISTICS

2. Ditches: the study of Ryssaert et al. (2010) showed refilled with heterogenous materials up to 10 – 20 that the 2 most inner ditches were dug through the cm thick of humiferous sandy loam to sandy mate- limnic sediments into the sandy layer. Moreover, the rial. Most archaeological information lies in the trenches showed a 2-stepped profile with a first level slope of the ditches and in the deeper central part on the limnic layer and a second level cutting through of the ditches. In the project design, these zones this layer into the substratum of the sandy material. had to be excluded from any disturbance in order The slope is very gradual from the onset of the ditch to protect the archaeological heritage features. towards the first level. Because of natural accumula- The outermost (fourth) circular ditch and part of tion of organic matter in water saturated conditions the third ditch, in the northern part of the struc- after the site had been left, the peaty layer was much ture, are situated in the transition zone between the thicker in the ditch than in the natural profile, with sandy ridge and the peaty depression. The argument an abrupt lower boundary. In this recent peat, plant of the absence of the marl layer as an indicator for remnants are often visible unlike in the older peat the existence of a ditch could not be used here. In which is amorphous. The older peat showed a nat- this case, it was only the presence of a humiferous ural transition to the limnic layer, which helped to horizon indicating the refill of the ditch. distinguish the boundary between the original soil and the ditch. Finally, the shallow depressions of the 3. Mound and banks between the ditches: the natu- ditches were recently (in the 19th and 20th centuries) ral profile has been buried with (on average) a 40 cm thick mixture of peat, marl and sandy material. The closer towards the centre of the site, the more archaeological artefacts (bricks, pottery, …) appeared (Ryssaert et al., 2010). The profile sequence is all the way through made up of mixed materials of limnic material with peat and sand originating from digging the ditches and used for the construction of the mound (in a latter phase this material is ploughed) – peat – limnic materials – sandy/loamy material.

Based on the soil typology and the DTM is was pos- sible to delineate, with high accuracy, the ditches and to determine their width. The central island has a diameter of 48 m. The width of the first ditch, between the cutting through the marl, is 20 m. In the ditch lies a recent sec- ondary fill on top of the recent peat, which has developed since the abandonment of the site. The bank between the first and second ditch measures 38 to 40 m. The bank was raised with a mixture of peat, sand and marl on top of the original peat. The second ditch is, between the cutting of the marl, about 12 m wide, the next bank between 20 to 23 m. The third ditch is about 7 m wide. The fourth and out- ermost ditch could not be identified in the trenches nor through augerings at the SE side. However, at the NW and NE side a ditch was encountered with a width of 5 to 6 m and identified through the presence of humiferous sandy material up to 160 cm deep. At the S and SW-side, the fourth ditch continues in a brook called Sint-Trudolede- ken. Whether this brook was incorporated into the site or vice versa is still a question to be answered (Figure 3).

Figure 2. Assebroekse Meersen. The natural profile shows a horizon of about 45 cm thick consisting of amorphous peaty mate- rial, underlain by marl sediments with former root galleries (bar = 80 cm). SOIL AND ARCHAEOLOGICAL GROUNDWORKS FOR LANDSCAPE DEVELOPMENT PROJECTS OF THE FLEMISH LAND AGENCY 311

6. Progress of the project and 20th century) applied heterogenous materials in the ditches of the northern part, and of the access ramps. A The aim of the landscape restoration project is to optimise recently dug ditch that drains the site will be refilled with the water management on the archaeological site and in locally recuperated sandy material. Finally, a walking path the meadowlands and to improve the hydrological and will lead to the core of the archaeological structure where soil conditions for the development of high quality mea- a viewpoint will be established. dowlands. The first phase of the project was completed in As the circular structure of Assebroek is legally pro- 2016. In the meadowlands, the water management works tected as an archaeological site, it is a challenge to develop involved the instalment of weirs and earth dams to regu- a restoration plan without damaging the site and the soils late the water level and to retain more water during sum- and to safeguard the ecological values. The soil – land- mer. Clearing water courses, ditches and drainage ditches scape reconstruction through augering made it possible was needed to improve water flow and to increase the to establish the exact thickness of the recent deposits, buffer capacity of the area. A bypass of the Meersbeek which can be removed without disturbing the archaeo- towards the meadowlands ensured the supply of good logical structures. quality water. The cycle path was rerouted and the tram- way track was removed. The second phase includes the upgrading of the archaeological site to improve the visibility of the archaeo- logical structure. It includes the removal of the felted turf in the ditches of the southern part, of the recently (19th

Figure 3. Localisation of the circular ditches separated by banks, position of the augerings and trench (Ryssaert et al. (2010); research VLM). 312 SOILS AS RECORDS OF PAST AND PRESENT. FROM SOIL SURVEYS TO ARCHAEOLOGICAL SITES: RESEARCH STRATEGIES FOR INTERPRETING SOIL CHARACTERISTICS

References

Ameryckx, J., 1955. Merkwaardige oudheidkundige vondst te Assebroek. Biekorf, 56, 7-8, 205-209. Ameryckx, J., 1958. Bodemkaart van België. Verklarende tekst bij het kaartblad Brugge 23W. Gent, centrum voor bodemkartering, IWONL. Ampe, C., 2012. Assebroekse Meersen: bespreking van de boor- resultaten; bijlage beschrijving van de boringen. Onuitgegeven rapport, VLM Regio West, vestiging Brugge. Deduytsche, A., 1974. Studie van enkele geomorfologische aspekten van het Zuid-Brugse Dallandschap. Onuitgegeven licentiaatsverhandeling, Rijksuniversiteit Gent, 58 p. De Meulemeester, J., 1981. Circulaire vormen in het Vlaamse kustgebied. Archaeologia Belgica, 234. De Moor, G. and Heyse, I., 1978. De morfologische evolutie van de Vlaamse Vallei. De Aardrijkskunde, 4, 343-375. FAO, 2006. Guidelines for soil description, fourth edition, FAO, Rome. Gheysen, K., 2019. Archeologienota Assebroekse Meersen fase 3. Verslag van resultaten. VLM Regio West, vestiging Brugge. Ryssaert, C., De Gryse, J., Tys, D., Baeteman, C., Orbons, J., Pype, P., Termote, D., Germonprez, D., and Perdaen, Y., 2010. Archeologische evaluatie en waardering van de circulaire struc- tuur van Ver-Assebroek (gemeente Brugge, provincie West- Vlaanderen). Onuitgegeven rapport. Studie in opdracht van Vlaamse Overheid, Ruimte en Erfgoed. Soers, K., 1987. Assebroek. Archeologische Inventaris Vlaanderen, band IX. Rijksuniversiteit Gent, Gent. UGent. Databank Luchtfotografie van de Vakgroep Archeologie van de Universiteit Gent. VLM, 2009. Brugse Veldzone. Veldgebied Brugge. Inrichtingsproject Randstedelijk Gebied Brugge. IP Groene Fietsgordel Brugge. VLM, West-Vlaanderen. SOILS AS RECORDS OF PAST AND PRESENT From soil surveys to archaeological sites: research strategies for interpreting soil characteristics

Edited by Judit Deák Carole Ampe Jari Hinsch Mikkelsen

Proceedings of the Geoarchaeological Meeting Bruges, 6 & 7 November 2019 This book is published on the occasion of the Geoarchaeological Meeting: Soils as records of Past and Present. From soil surveys to archaeological sites: research strategies for interpreting soil characteristics on 6 & 7 November 2019 in Bruges, Belgium.

Editors Judit Deák, Carole Ampe and Jari Hinsch Mikkelsen

Technical editor Mariebelle Deceuninck

English language reviewer Caroline Landsheere

Graphic design Frederick Moyaert

Printing & binding Die Keure, Bruges

Publisher Raakvlak Archaeology, Monuments and Landscapes of Bruges and Hinterland, Belgium www.raakvlak.be

Copyright and photographic credits The printed version of this book is protected by the copyright © Raakvlak. ISBN 978 90 76297 811 This book is a collection of freely available (open access) documents. The book and the papers composing it have individual digital object identifiers (doi, indicated on each paper) and are hosted by the non-commercial depository archive (Zenodo). MUSEA The rightsholders (authors and/or institutions) retain the BRUGGE copyright of their contribution. The online contributions are distributed under the Creative Commons Attribution Share Alike, 4.0 License (CC-BY-SA). The authors of the papers warrant that they have secured the right to reproduce any material that has already been published or copyrighted elsewhere and that they identified such objects with appropriate citations and copyright statements, if applicable, in captions or even within the objects themselves. Neither the editors, nor the publisher can in any way be held liable for any copyright complains. Photographic credits Citation recommendation Cover, p. 6 Judit Deák, Carole Ampe, and Jari Hinsch Mikkelsen (Eds.). Landscape with cows near (detail), Soils as records of past and Present. From soil surveys to Jean Baptiste Daveloose archaeological sites: research strategies for interpreting soil © Musea Brugge characteristics. Proceedings of the Geoarchaeological Meeting © Lukas Art in Flanders vzw Bruges (Belgium), 6 & 7 November, 2019. Raakvlak, Bruges. © Dominique Provost Art Photography ISBN 978 90 76297 811 Soil collages p. 16, 87, 173, 261, 297 Doi: http://10.5281/zenodo.3420213 © Roger Langohr, Jari Hinsch Mikkelsen and Carole Ampe 4

TABLE OF CONTENT

7 Foreword D. De fauw, N. Blontrock and P. Ennaert

9 Introduction From soils surveys to archaeological sites and beyond: research strategies and original approaches for interpreting soils, anthropic activity, and environmental changes J. Deák, C. Ampe and J. Hinsch Mikkelsen

15 Scientific reviewers

1. Present and past soilscapes and land use

19 Settlement of the first farmers in the Belgian loess belt, the edaphic factor R. Langohr

31 Land use and settlement dynamics in the bays of Bevaix and Cortaillod (Neuchâtel Lake, Switzerland) during Late Bronze Age J. Deák, F. Langenegger and S. Wüthrich

55 The Abc soil types: Podzoluvisols, Albeluvisols or Retisols? A review S. Dondeyne and J.A. Deckers

65 The byre’s tale. Farming nutrient-poor cover sands at the edge of the Roman Empire (NW-Belgium) J. Hinsch Mikkelsen, R. Langohr, V. Vanwesenbeeck, I. Bourgeois and W. De Clercq

2. Natural and anthropogenic soil forming factors and processes

89 Drift sand-podzol hydrosequences in the Mol-Dessel area, NE Belgium K. Beerten

99 Bioturbation and the formation of latent stratigraphies on prehistoric sites Two case studies from the Belgian-Dutch coversand area Ph. Crombé, L. Messiaen, D. Teetaert, J. Sergant, E. Meylemans, Y. Perdaen and J. Verhegge

113 Les faux poteaux plantés J. Vanmoerkerke, W. Tegel and C. Laurelut

121 Feux agricoles, des techniques méconnues des archéologues L’apport de l’étude archéopédologique des résidus de combustion de Transinne (Belgique) C. Menbrivès, C. Petit, M. Elliott, W. Eddargach and K. Fechner

141 Micromorphologie des constructions en terre et convergence de faciès Le cas du site des Genêts à Ablis (Yvelines, France) M. Rué and A. Hauzeur

159 Facing complexity: an interdisciplinary study of an early medieval Dark Earth witnessing pasture and crop cultivation from the centre of Aalst (Belgium) Y. Devos, K. De Groote, J. Moens and L. Vrydaghs 5

3. Archaeology and soil science, unravelling the complexity

175 Méthodologie d’une recherche paléoenvironnementale en archéologie préventive L’exemple du site de Kerkhove Stuw (Belgique) F. Cruz, J. Sergant, A. Storme, L. Allemeersch, K. Aluwé, J. Jacops, H. Vandendriessche, G. Noens, J. Hinsch Mikkelsen, J. Rozek, P. Laloo and Ph. Crombé

189 Study of past and present records in soils from Lorraine (France) A geoarchaeological approach in the context of rescue archaeology A. Gebhardt

209 Reconstruction des modes de vie au Néolithique et au Bronze Ancien Synopsis des apports récents des études pédologiques entre Rhin et Seine K. Fechner, D. Bosquet, F. Broes, avec la collaboration de L. Burnez-Lanotte, V. Clavel, L. Deschodt, H. Doutrelepont (†), G. Hulin, J. Hus and R. Langohr

231 The evolution and medieval re-use of a prehistoric barrow at Wielsbeke (, Belgium) F. Beke, J. Hinsch Mikkelsen and A.C. van den Dorpel

243 Curbing the tide. The discovery of a Roman terp along the Heistlaan in Ramskapelle (Knokke-Heist) D. Verwerft, J. Hinsch Mikkelsen and W. De Clercq

4. Past climates and environments

263 Soils or sediments? The role of R. Langohr’s process-oriented approach in understanding carbonate-related palaeosols of the stratigraphic record A. Mindszenty

271 Palaeosoils as indicators of local palaeoenvironmental changes Mosaics from the Hungarian loess studies E. Horváth, Á. Novothny, G. Barta, D. Csonka, T. Végh and B. Bradák

279 A distinct pedogenetic path under a Mediterranean climate The case of soils on Areny sandstone formation (Tremp basin, NE Iberian Peninsula) R.M. Poch, J.C. Balasch, M. Antúnez, J. Vadell, A. Forss and J. Boixadera

5. Present and future use of soil data

299 The Database of the Subsoil in Flanders (DOV) related to soil and archaeological research K. Oorts, V. Vanwesenbeeck, M. Van Damme and S. Buyle

307 Soil and archaeological groundworks for landscape development projects of the Flemish Land Agency The case study of Assebroek C. Ampe and K. Gheysen

313 Archaeology and Soil Science in Flanders Personal reflections of an archaeologist in 2019 M. Pieters