Dendroarchaeology - dendrochronological investigations of archaeological wood from Ljubljansko barje (Ljubljana Moor)

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1 Dendroarchaeology - dendrochronological investigations of archaeological wood from Ljubljansko barje (Ljubljana Moor) Prehistoric wheel Ljubljana Moor is our the most important location where larger amounts of wood from the past are preserved underwater or buried in ground. Veluscek (1999) reports on remains of over 40 prehistoric pile dwellings from the cooper age (Eneolit). They existed between 3500 and 2500 BC. Our work is focused towards dendrochronological investigations of archaeological wood. Systematic collecting of wood for research started in Dr. Anton Veluscek from the Institute of Archaeology SRC SAAS coordinates the work. In the last years we investigated wood from 10 pile dwellings. The picture presents their position on the map of Ljubljana Moor. Remains of pile dwellings that existed in the same time as those in

2 the Ljubljana Moor, have been found in all Alpine countries. The wood is generally preserved underwater (for example in the river Iscica) or buried in the soil. The wood is often found during different activities, like cleaning of the drainage ditches. After exposure to air it decays rapidly. Rescue excavations in the ditches are important to obtain wood for research. In the Ljubljana Moor we mainly found remains of vertical piles. Samples of wood prepared for laboratory analyses. On smooth surfaces we can observe wood structure and identify wood species. We can also observe the tree-rings. The structure of the rings represents an archive of past events, that affected growth of a tree. Picture shows samples of ash-wood

3 (Fraxinus sp.). This is the most frequent wood species from our prehistoric pile dwellings. Larger stems (>14 cm) were split along the tree axis. Picture shows samples of oak (Quercus sp.) also an important wood species in the Ljubljana Moor. Structural details can be observed on thin slides with help of a microscope. In the remains of the dwellings we can often find large number of piles from trees cut in the same calendar year.

4 We select samples for radiocarbon dating. Radiocarbon dating of our samples was done by Dr. Bern Kromer and his team from the Heidelberg Academy of Sciences - Radiometische Altersbestimmung von Wasser und Sedimenten, Heidelberg, Germany. Graph showing time spans of treering series. The picture shows that several trees have been cut in the same year. Most of the trees were cut in relative years 187 and 232. A plan of the dwelling with coordinates of all wooden remains. The distribution of piles from the same period helps to reconstruct ground plans of the buildings. The picture shows the older (top) and the younger (below) part of the dwelling. The piles found on the same place often originate from different periods.

5 Dendrochronologically investigated pile dwellings existed between 4000 BC and 2500 BC. The dating is based on dendrochronology and radiocarbon analyses. The prehistoric wheel and other wooden artefacts, properties of archaeological wood The team of archaeologists coordinated by Dr. Anton Veluscek during excavations in 2002 found a prehistoric wheel with axle and some other wooden artefacts. The age of the wheel is 5100 years or more. The dating is based on radiocarbon dating of the laboratory VERA in Vienna, Austria.

6 A reconstruction of a prehistoric cart has been made years ago the civilizations from the near east already used the wheels, but none of them has been preserved until today. The wheel has been made out of two radial boards of ash-wood. The axle was made of oak wood. The wood was processed with stone tools.the artefact shows that the prehistoric men from the Ljubljana Moor understood wood properties very well. They processed and used wood in an optimal way. In the Ljubljana Moor there were found several canoes. The dugout found in 2002 has been made of one oak stem. The elaboration of wood was of high quality. The canoe has been dendrochronologically cross-dated with a chronology of Stare Gmajne, the dwelling where it was found. The dating of the canoe is BC.

7 The picture shows the oldest bow made of wood of yew (Taxus sp.) aged 5800 years.in the period when it was made bows were regularly used weapons. The bow is exceptionally well preserved. Such founds are extremely rare. The archaeological wood seems to be well preserved when excavated but its properties differ considerably from those of normal wood. The predominant chemical constituent in archaeological wood is lignin (approx. 70%). The amount of cellulose and hemicelluloses is considerably reduced. Physical properties of wood are changed as well exceptionally its shrinkage. The picture shows the watersaturated disc of wood (upper picture) as found in the field. After 5 days (middle) it shrank considerably. After 21 days (lower picture) it was completely collapsed. The wood lost its research potential. We must prevent desiccation of water-saturated wood. The wood can

8 be stored in polythene bags.