Braathen Dendrokronologiska Undersökningar
Lunnevägen 2, SE-46144 Trollhättan, Sweden
Bulverket Tingstäde Träsk, Gotland
In the middle of a lake, Tingstäde Träsk, in northern Gotland a construction consisting of about 38000 pieces of timber (Bulverket) is situated. The structure is a square with a length of 270 m of the outer side. It is open in its interior. It is surrounded in some distance by two rows of vertical poles, knocked into the bottom of the lake. The structure consists of rows of parallel placed log framed bases along the sides of the square. In between are remains of buildings in framework construction.
Anders Rönnby, archaeologist, has made a thorough investigation of the structure and intends to present a thesis for his doctor's degree in 1993. His work might be of interest also outside Sweden because similar structures have been found in lakes east of the Baltic Sea.
More than 100 samples from the pine timber were investigated, but only a few had waney edge. Those with waney edge had been taken about 2 m below the present bottom of the lake. The youngest received date from a log in the square is 1121 and from one of the poles outside the square 1124.
All the dating together show that the structure was built in one, rather short period.
All the pieces of wood which were in level with or above the bottom were much eroded but to a varying degree due to their position. More than 50 annual rings had partly disappeared because of movement of the water.