SMA 9 Burial, Decay And Preservation Of Archaeological Remains

Burial Conditions
1. Normal
  1. Dryslwyn Castle, Wales
    Annotations:
    - Medieval Welsh castle, constructed between AD 1220’s and 1287, occupied until 1420’s, then demolished. Located on a limestone hill. No organic material remains and the metal is highly corroded
  2. Sutton Hoo, Suffolk
    Annotations:
    - A 7th century Saxon burial ground which including a royal ship burial. Sandy soil ridge above a river. Well drained all the iron was highly corroded and all organic material decayed. Even some of the bones had decayed leaving little more than a stain in the ground.
2. Frozen
  1. John Torrington
    Annotations:
    - One of 3 sailors on the 1845 Franklin expedition, buried in the perma-frost ground of one of the islands in the Canadian Arctic. All members of the expedition eventually perished. The body of John Torrington has remained preserved, frozen in its grave.
  2. Otze (the iceman)
    Annotations:
    - A man from circa 3200-3500 BC, who was interred in the glacier, recovered in 1991, together with much of the clothing and equipment he was carrying. Organic materials such as his shoes and his bow and arrows survived.
  3. Qilakitsoq
    Annotations:
    - West Greenland Two groups of Inuit buried under a rock overhang, near the settlement of Qilakitsoq. The bodies of children and women date from circa AD1475 and were probably killed by disease. Many of the bodies were wrapped in clothing of leather and feathers. The bodies and clothing had preserved by being frozen and then dried by the cold arctic wind. This had effectively freeze dried the remains.
3. Waterlogged
  1. Coppergate (York) and Rose & Globe Theatres (London)
    Annotations:
    - Coppergate: 9-11th century buildings & occupation deposits, flood ground beside river Ouse. Rose & Globe: wooden Shakespearean theatres flooded ground beside the Thames
  2. Bog Bodies: Tollund Man (Denmark) Lindow Man (England)
    Annotations:
    - Bog bodies, usually with evidence of having been ritually killed and weighted or held down, have been retrieved from bogs in England, Ireland, Denmark, Netherlands and northern Germany. These well preserved examples usually come from raised bog environments rich in sphagnum peat.
  3. Sweet track
    Annotations:
    - Somerset Trackway built circa 3200BC across the lowland peat bogs of the Somerset Levels. The wood of the trackway has been preserved in the oxygen free environment of the peat bog.
  4. Wasa
    Annotations:
    - 17th century warship raised from Stockholm harbour
4. Sealed
  1. Osburg Viking Ship Burial
    Annotations:
    - A rich Viking ship burial was sealed under a clay mound at Osburg in Norway. Extensive wood and textile remains preserved.
  2. Cuthbert and his Coffin
    Annotations:
    - Cuthbert died in 687, his body retrieved in 698 was found to be miraculously incorrupt. He was interred in a new coffin which was probably kept in an above ground shrine for most of the medieval period.
5. Dessicated
  1. Tutankhamun’s Tomb
    Annotations:
    - Rock-cut tomb for the pharaoh Tutankhamun(1361-1352 BC). Opened in AD1922, it was dry, virtually no water had entered to tomb. All the organic material (wood textile, basketry) was preserved. The body had been mummified and protected in a series of coffins inside a sarcophagus.
6. Burial environments determine what survives. ‘Normal’ soil contains both oxygen (aerobic) and water and so metals corrode and organic materials are consumed by fungi and bacteria.
  1. Soils without oxygen = anoxic (anaerobic), usually waterlogged, preserve organic material and metal, as do frozen and desiccated sites (without liquid water).
Archaeological Materials
1. Inorganics
  1. stone, ceramics, glass (enamel)
2. Organics
  1. wood, bone (antler, ivory, tooth), leather, textiles
3. Metals
  1. iron (steel), gold, silver, copper alloys (brass, bronze), lead, tin
Metal Corrosion
1. Iron
  1. FeOOH = goethite (red)
  2. Fe3O4 = magnetite (black)
2. Copper
  1. CuCO3.Cu(OH)2 = malachite (green)
  2. Cu2O = cuprite (red)
3. Silver
  1. Ag2S = acanthite - silver sulphide (black)
  2. AgCl = horn silver (grey)
4. Lead
  1. PbCO3.Pb(OH)2 = hydrocerrusite (white)
  2. PbCO3 = cerrusite (white)
5. All metals, except gold (Au) corrode in the presence of oxygen and water
  1. M (metal) → M+ (metal ion) + e- (electron)
  2. Metal ions dissolve into water, electrons pass through the metal. On the metal surface, electrons react with oxygen and water to form hydroxide ions.
    1. 4e- (electrons) + O2 (oxygen) + H2O (water) → 4OH- (hydroxide ions)
    2. Hydroxide ions dissolve into water and combine with metal ions to form minerals. Metal hydroxides are not stable so more stable minerals such as oxides and carbonates form. It's these minerals which build up as corrosion on the exterior of metals.
      1. Chloride ions (Cl-) = catalyst for most metal corrosion reactions, particularly iron. Consequently metal corrosion occurs faster in marine conditions.
Mineral Replaced Organics and Mineral Preserved Organics
1. Cast:
  1. where the minerals forms a shell round the outside of the organic, producing a mirror image of its exterior form.
2. In wet or damp conditions iron minerals can form on or in organic materials lying beside or attached to the corroding iron object. The organic materials soon decays leaving the iron minerals preserving the form of the organic material.
3. Pseudomorph:
  1. minerals form within the organic material forming an exact copy of the organic material.
4. Cast and Pseudomorph:
  1. both mechanism occur at the same.
5. Silver Embrittlement:
  1. Silver when debased with copper gradually hardens over time as the atoms separate within the crystal structure of the metal. This makes it fragile and any silver over 500 years old could shatter. Pure silver is unaffected and remains tough. Silver is often decorated with niello, a deliberately created and applied silver sulphide.

Next up

SMA 9 Burial, Decay And Preservation Of Archaeological Remains

Description

Resource summary

Similar

	Created by Sophie Lumsdon over 10 years ago