Absolute dating can be performed with the use of historical documents and through the analysis of biological and patterns that are geological from annual climatic variants, such as for instance tree bands (dendrochronology) and varve analysis. Since 1950 the real sciences contributed lots of absolute dating techniques that have experienced a revolutionary influence on archaeology and geology. These strategies are based on the dimension of radioactive procedures (radiocarbon; potassium-argon, uranium-lead, uranium-thorium, thorium-lead, etc.; fission track; thermoluminescence; optically stimulated luminescence; and resonance that is electron-spin, chemical procedures (amino-acid racemization and obsidian moisture), as well as the magnetic properties of igneous product, cooked clay, and sedimentary build up (paleomagnetism). Other practices are now and again helpful, as an example, historic or iconographic recommendations to datable astronomical activities such as for example solar eclipses (archaeoastronomy).
Whenever archaeologists get access to the historic documents of civilizations which had calendars and counted and recorded the passage through of years, the particular chronilogical age of the archaeological product can be ascertainedвЂ”provided there is certainly some foundation for correlating our contemporary calendar using the ancient calendar.