Absolute dating

Absolute age dating using apatite is only possible in very restricted circumstances and has been applied to volcanic and shallow intrusive rocks, meteorite impact events and contact metamorphism. The fundamental requirement is that samples cooled rapidly and subsequently remained thermally undisturbed and close to or at the surface. Due to its relatively low uranium content and restricted occurrence, apatite dating of Quaternary 

The complete or partial resetting of apatite fission track clocks in target rocks by shock-wave heating has been used to constrain the timing of meteorite impacts events (e.g., Wagner 1977, Storzer and Wagner 1977, Hartung et al. 1986, Omar et al. 1987 and Kohn et al. 1995). 

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Chronology may be expressed in two forms absolute and relative chronology. Absolute chronology depends on knowing the precise date of events or age of materials or objects. To sequence events or objects in absolute chronology implies organizing them in a certain order, for example, from oldest to most recent. Relative chronology is not expressed in specific dates but rather in a sequential relationship of events. Relative dates are therefore expressed in relation to those of other objects or events they do not specify the precise age of objects or the time of occurrence of events. Absolute dates provide the precise age of objects and the time of occurrence of events, and are derived independently of those of other objects or events. 

Considering all the above factors for amino acid racemisation rates, this technique cannot be used as an absolute dating technique. To overcome the problem of uncertainty, the amino acid racemisation method must be calibrated against other more reliable techniques. 

It has been suggested by Lai [34] that 10Be and 26A1 taken together form an ideal pair for absolute dating. Their residence time and geochemical behavior in the earth s biosphere are sufficiently similar that one may expect a constant ratio of these radioisotopes in all sediments at the time of deposition. Each of the radioisotopes decays exponentially, so that the age of the sediments can be calculated from ... 

Because the half-lives of these two isotopes vary by more than a factor of two, the method is sensitive. Since the ratio 26A1/ 10Be decreases by a factor of two every 1.3 million years, it is thought that the method should provide absolute dates up to several million years. 

Absolute Dating of Travertines from Archaeological Sites... 

Figure 1. Absolute dating methods relevant to the period of man s evolution. TL (Thermoluminescence), MTh/mV and 231 Pa/235 dating are applicable to...

Schwarcz, H. P., Liritzis, Y., Dixon, A., Absolute dating of travertines from Petralona cave, Khalkidiki Peninsula, Greece, Anthropos (Athens), 7, 152-173 (1980). 

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