An Encyclopaedia of Indian Archaeology v1.c12.s1.1

v1.c12.s1.1

Geochronology, the science of dating events in earth history, essentially involves the study of repetitive superimposed features of the geological record, such as tree rings, varves and sedimentary cycles and of measurement of the ages based on the progressive decay of radiometric minerals, e.g. carbon 14 [5.3], potassium-argon, uranium-thorium, etc. These absolute methods are closely linked with relative dating methods where events are described as older or younger than other events and include the study of river/coastal terraces, palaeontology, palaeobotany and stratigraphy. Thermoluminescence [5.6] and fission-trace dating involve the measurement of microscopic features produced in certain minerals due to radioactive reactions. Palaeomagnetic studies record changes in the direction of the earth's magnetic field, while archaeomagnetism [5.2] measures the remnant of magnetism in archaeological material (pottery) caused by heat. Collectively these techniques have helped to push back the antiquity of man to three million years B.P. in Africa.