Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or a presumed evolution in form or structure, or absolute dating, in which items are assigned a date independent of context.
speed dating modesto - Lead dating
See also fission-track dating; helium dating; lead-210 dating; rubidium-strontium dating; uranium-234–uranium-238 dating; uranium-thorium-lead dating.
in geology, determining a chronology or calendar of events in the history of the Earth, using to a large degree the evidence of organic evolution in the sedimentary rocks accumulated through geologic time in marine and continental environments.
To date past events, processes, formations, and fossil organisms, geologists employ a variety of techniques.
These include some that establish a relative chronology in which occurrences can be placed in the correct sequence relative to one another or to some known succession of events.
Radiometric dating and certain other approaches are used to provide absolute chronologies in terms of years before the present.
The two approaches are often complementary, as when a sequence of occurrences in one context can be correlated with an absolute chronlogy elsewhere.Local relationships on a single outcrop or archaeological site can often be interpreted to deduce the sequence in which the materials were assembled.This then can be used to deduce the sequence of events and processes that took place or the history of that brief period of time as recorded in the rocks or soil.For example, the presence of recycled bricks at an archaeological site indicates the sequence in which the structures were built.Similarly, in geology, if distinctive granitic pebbles can be found in the sediment beside a similar granitic body, it can be inferred that the granite, after cooling, had been uplifted and eroded and therefore was not injected into the adjacent rock sequence.Although with clever detective work many complex time sequences or relative ages can be deduced, the ability to show that objects at two separated sites were formed at the same time requires additional information.