Preliminary results of bone diagenesis in Scandinavian bogs

There are several hundred documented finds of “bog bodies” from all over Europe, exhibiting a range of preservation states and spanning nearly all archaeological eras — from Neolithic to Medieval. Although these have caught the imagination of both public and academics alike, there is still little consensus on the diagenetic processes that lead to their formation. This work presents early results of an ongoing eight-year project to model some of the processes that lead to the formation of a bog body. The project covers two wetland sites, Rørmyra in Mid-Norway and Lejre in Denmark. Preliminary results show rapid demineralisation of bovine bone and spectacular preservation of pig skin within a raised sphagnum bog in Norway, compared with no detectable demineralisation and poor preservation of skin in a fenland bog in Denmark. Rates of demineralisation at Rørmyra show a linear relationship with time and lead us to predict that a human skeleton may become completely decalcified in approximately 300 years. Electron microscopy of histological sections shows that decalcification proceeds via the natural canalicular network in bone, ultimately leaving a naked collagen matrix that shrinks and cracks on drying.