Het was toeval. De archeologische begeleiding van de uitbreiding van het Tilburgse sportcomplex Spoordijk had slechts enkele sporen en vondsten uit de ijzertijd opgeleverd en was afgesloten. Frans van Nuenen, vrijwilliger in de archeologie, inspecteerde na afloop van de werkzaamheden echter nog eenmaal het terrein en vond in het talud van een nieuwe waterpartij een grote, zwarte vlek. De gemeente pakte de waarneming meteen op en liet een kleinschalige opgraving uitvoeren om de kuil te documenteren en de vondsten te bergen (afbeelding 1). Het bleek om een flinke kuil te gaan, vol met houtskool en prehistorisch aardewerk. Een 14C-datering van verkoolde zaden maakt duidelijk dat de kuil stamt uit de tweede helft van de vijfde eeuw voor Chr. Vorm en versiering van het aardewerk uit de kuil onderstrepen deze datering in de midden-ijzertijd. Tussen het vondstmateriaal werd een aantal opvallende en onbekende voorwerpen aangetroffen: complete en gebroken, eivormige, holle objecten met een klein gat in de punt en een verglaasde buitenkant. Wat zijn dit? ... Read more

Signed 25 years ago, the Valletta treaty places a strong emphasis on the protection of archaeological sites. Because of acute threats of archaeological site destruction by construction activities, a major result was a massive increase in rescue and preventative excavations on threatened sites. The Treaty also proposed that heritage assets should be preserved in situ, where feasible, and recommended member states share knowledge and training on this subject. Over the past 25 years a range of pilot projects and detailed one-off studies on specific sites have been conducted across Europe. In this session, we will discuss new insights we have gained into human and natural threats to archaeological sites, and practical ways to deal with them, including a) assessing and limiting the impact of construction on archaeological sites, e.g. the effects of piling and loading; b) determining the effects that agricultural practices, nature conservation projects and other rural land-use change have on archaeological sites and what mitigating measures are possible; c) developing and future-proofing protective measures and dynamic schemes for site protection; d) monitoring and assessment of the state of preservation of archaeological sites and materials, especially with regard balancing high-tech intense monitoring on few with low-tech extensive monitoring on larger numbers of sites; e) effects of climate change on the preservation of archaeological sites. ... Read more

The ratification of the Malta convention has meant that construction works are commonly preceded by research to establish whether damage to archaeological remains will occur. If this is likely, development plans are adapted to enable preservation in-situ or the developer funds a rescue-excavation. A factor playing in favour of in-situ preservation is the overconsolidation of archaeological layers. A soil is said to be overconsolidated when it has been exposed during its history to vertical stresses higher than current ones. As a result, it is only when stresses applied by new constructions exceed the pre-consolidation pressure that soil de-structuration and mechanical damage to archaeology may occur. Many processes can generate overconsolidation at archaeological sites. Site burial followed by erosion, construction of structures, then demolished, soil trampling by heavy animals, drainage of topsoil to keep site occupants’ feet dry, increase of ground water level after site abandonment, but also chemical reactions and ageing can cause over-consolidation. High over-consolidation has been measured in the foundation layers of a high embankment (up to 15 m high) built in the 19th century at Vechten, the Netherlands. The embankment was erected on top of a former Roman vicus established on the natural levee. The Roman level and the 19th century topsoil are rich in fragments of ceramics, bones and metal objects. Over-consolidation pressures are in line with the measured strength and stiffness of the foundation material and the massive soil structures analysed using X-ray micro-computed tomography and micro-morphology. The absence of deflection of the interface between the embankment and its foundation layers indicates that the archaeological layers were already in an over-consolidation state before the construction of the embankment and remained over-consolidated after its construction. In such circumstances, it is only by affecting the groundwater flow and chemistry that the embankment could have degraded underlain archaeology. ... Read more

X-ray Micro-Computed Tomography (micro-CT) is an excellent technique to inspect small delicate beads. It reveals their composition and inner structure without damaging them. In particular the geometry of the narrow bead shafts becomes clear on micro-CT scans. Archaeologists can then draw conclusions about the way the beads were made, worn and, in some occasions, re-worked. The origin of the materials selected to make the beads, their production centre and trading routes can even be traced by combining micro-CT scans to other information, such as results of XRF analyses. Signs of post-burial deterioration become obvious. Forgery is easily detected. micro-CT scans also constitute a form of virtual preservation of the ornaments. Once stored in open source repository, they can be further exploited by various stakeholders (musea, archaeologists, the creative industry). The potential of micro-CT is illustrated for two collections of ancient Dutch ornaments: the Neolithic amber beads recovered from several graves and Early Iron Age frothy glass beads from Zutphen.
The role of amber beads in the materiality of burial practices in three different periods of the Dutch Neolithic has been investigated by combining microscopy and micro-CT. The scans allowed to evaluate the quality of manufacture and repair of the beads and detect signs of wear, re-shaping and post burial degradation. About 60 glass beads were recovered from an Early Iron Age urn-field near Zutphen (NL). Glass is rare in this period in the Netherlands and has been investigated, first, to determine from what primary glass production centre this glass originated, and by what route it could have reached the Netherlands, and second, to determine the nature and origin of the frothy structure of the beads. With its many glass bubbles, copper fillings and mineral inclusions, the glass of the Zutphen beads does not resemble glass from Mediterranean
production sites. ... Read more

Curly malachite (CM) is found as a green cupric carbonate hydroxide corrosion product on archaeological bronze, mostly on artefacts retrieved from graves. In this paper, a morphological characterization approach is proposed, enabling the investigation of the formation process of CM. It is suggested that curly malachite precipitates from an aqueous solution, for which the surrounding soil conditions provide local triggers. Anthropic activities associated with ritual burials do not significantly affect the growth of CM. It is also confirmed that curly malachite is usually not a pseudomorph of formerly organic material. Although the understanding of the formation process is far from complete, this study has shown that CM is expected to be found more often than is currently recognized, due to its relatively simple formation mechanisms and boundary conditions. ... Read more