Historical_Dating

Historical dating This relies on written records such as documents, government and religious records, and inscriptions on stone, clay or papyrus. There are two techniques for dating in archaeological sites; relative and absolute dating. Relative dating methods • This type of dating is based on the principles of stratigraphy and typology to establish approximate dates for archaeological finds. Stratigraphic dating: • This method of dating involves the analysis of the different strata levels which contain different archaeological finds to establish a chronological sequence. • Since each layer usually represents a different time period of human occupation at he site, they are able to work out which objects are earlier or later than each other • Therefore the strata closer to the surface will be younger than those below • However these Stratigraphic sequences can sometimes be unreliable Typology dating: • This same principle of organising finds in chronological sequence is also the basis of typology dating (relative dating). • Groups of artefacts such as pottery, tools or weapons can be arranged in a sequence from the earliest types to the latest • Two important principles of typology dating: • All artefacts belonging to a particular period of time have similar features, based on creation materials, shape and decoration • As time progresses, the artefacts will change form, style, appearance etc. materials and process of creation may also vary; general rule = earlier models tend to be more similar in design as appose to the elaborate detail of later models Serration dating: • Was created by William Flinders Petrie (1853-1942) in Naquada, Egypt in 1894-95 • It was foundered through the innovation of arranging all artefacts discovered in the excavated graves in typological sequence, and then similar groups were arranged in a succession (serial order) The three – Age system: • One of the earliest and most useful systems of organising finds in sequential order – created in 1836 by CJ. Thomsen • It was established as a three-part organisation of ancient artefacts based on the technology of stone, bronze and iron • Stone cam before bronze, and bronze before iron – another form of relative dating Absolute Dating • The most fundamental concern in archaeology; is accurate and absolute dating results • 1940’s saw the creation of radiocarbon dating • It was now possible to determine exact or absolute dates by strictly scientific methods Radiocarbon dating: • Radiocarbon dating *Carbon 14) dates organic material from 400yrs old to 50,000 yrs old • Works on basic principle that all living things interact with atmospheric carbon – therefore over time this carbon begins to decay when organism is deceased • Through this scientist can pinpoint when it was created based on the remaining carbon 14 • Examples of materials able to be dated using this method include; peat, pollen, bone, shell, hair, leather, corals, blood residue, paper &parchment, fish and insect remains, soil, wood, charcoal etc AMS radiocarbon dating: • AMS = Accelerator mass spectrometry • This is a more sophisticated version of radiocarbon dating – developed in 1970’s and is slowly phasing out other methods of radiocarbon dating despite large costs • It can date material to about 70,000 years old • More accurate and requires smaller amounts of samples • Contamination can be more easily reduced making the results more accurate • Produces results much quicker than other forms of carbon dating • Possibility of dating objects over 100,000 years old Dendrochronology: • This is tree-ring dating, developed in the 1920,s first method of scientific dating used by archaeologists • Works on the principle that the age of a tree (or any timber objects made from trees) can be determined by counting the growth rings in a cross-section of the timber • By comparing the overlapping of such ring patterns (older trees of the same species growing in the same region show a similar pattern of ring-growth), scientists can work out a long, continuous or master sequence for a region of thousands of yrs old • Archaeologists can match the pattern of growth rings in timber artefacts from an excavation site with the master sequence for that region • Enables them to calculate a date for the stratum in which the timber artefacts are found Potassium-argon dating: • This is used by geologists to date volcanic rock up to millions of years old. • It has proved to be one of the most useful methods for dating human evolution • Effectively works when evidence of human life is located around areas of high volcanic activity – which produces fossils Uranium-series dating: • The uranium series method is most commonly used to date rocks containing calcium carbonate that are most commonly found as stalagmite and other formations in caves • Effective as caves hold sources of human activity; such as remains, bones etc • Useful for periods of time between 50,000 and 500,000 yrs of age – beyond present reach of carbon dating – therefore links well with it Fission-track dating: • This is an application of radioactive dating used by archaeologists to determine the thermal age of artefacts containing uranium-bearing minerals • Dates between 21,000 and 1,000,000 yrs old • Effective dating items include, manufactured and natural glass, stones, fired ceramics (pottery and tile) • Used to verify dates obtained from potassium-argon dating Thermoluminescence dating: • This is another form of radiocarbon dating • It can date pottery and inorganic material that is over 50,00 yrs old 9unlinke other forms of carbon dating) • It’s often been used to date artefacts from sites where radiocarbon dates cannot be obtained or where the Carbon 14 dates may be unreliable • Artefacts that may be fake can be tested by TL dating for authenticity • Principle = the microscopic structure of some minerals and ceramics trap nuclear radioactivity Dating Method Application Electron-spin resonance (ESR) Bone, teeth, shell Archaeomagnitc dating Fireplaces, areas of burnt earth Obsidian hydrating Volcanic glass, tools etc, Palaeothic sites Amino-acid racemisation Human or animal bone – up to 100,000 yrs old Cation-ratio dating Rock carvings and engraving Fluorine-uranium-nitrogen dating Bone, teeth, antlers, ivory