York: World Class Heritage City
Waterlogged Deposits
The deep, wet archaeological deposits together with anoxic preservation conditions have ensured that minimal degradation of organic materials has occurred. Artefacts, structural features, biological remains and environmental evidence often appear to be as well preserved as when they were first deposited. Metal objects exhibit minimal corrosion and retain their original sheen; textiles and leatherwork remain pliable; insects are perfectly preserved (including a Viking hive complete with bees). These wet, anoxic conditions create the optimum circumstances for the preservation of organic materials that do not survive on dry archaeological sites.
The best-known excavation of these deposits was carried out at Coppergate, where between 1976 and 1981, a 7m deep set of stratified deposits was systematically investigated from the 19th century to the 1st century. Much of the deposit belonged to the 10th–11th century. Four long narrow plots at this period (and indeed later) ran back from Coppergate towards the nearby River Foss. At the street front, each plot contained a timber house or shop set gable-end to the street. Behind were workshops and behind them yards, rubbish pits, latrines and wells. There may have been a warehouse near the river.
The ground was waterlogged, rubbish was dumped in and around the buildings, and conditions grew up which were conducive to the preservation not only of the buildings themselves, but also of both organic and inorganic artefacts, natural materials and the ambient flora and fauna. Individual objects numbered some 15,000, outstanding amongst which – indeed one of the most important finds ever in York – is the York helmet, made in York c. AD 780.
The remarkable conditions of preservation at Coppergate have subsequently been observed on other sites dating from the Roman period to the 19th century.