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Geochronology is the scientific branch of geology that aims to determine the age of rocks, fossils, and sediments either through absolute (e.g., radiometric dating) or relative means (e.g., stratigraphic position, paleomagnetism, stable isotope ratios). Geochronometry is the field of geochronology that numerically quantifies geologic time. [16]
Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes , whereas relative geochronology is provided by tools such as paleomagnetism and stable isotope ratios .
Absolute dating is the process of determining an age on a specified chronology in archaeology and geology.Some scientists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies an unwarranted certainty of accuracy.
The age that can be calculated by radiometric dating is thus the time at which the rock or mineral cooled to closure temperature. [ 16 ] [ 17 ] This temperature varies for every mineral and isotopic system, so a system can be closed for one mineral but open for another.
Relative dating is the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining their absolute age (i.e., estimated age). In geology, rock or superficial deposits, fossils and lithologies can be used to correlate one stratigraphic column with another.
Absolute dating allows geologists to determine a more precise chronology of geological events, based on numerical ages or ranges. Absolute dating includes the use of radiometric dating methods, such as radiocarbon dating , potassium–argon dating , and uranium–lead dating .
Comparison of different minerals in a rock sample thus allows scientists to infer the original 87 Sr/ 86 Sr ratio and determine the age of the rock. In addition, Rb is a highly incompatible element that, during partial melting of the mantle, prefers to join the magmatic melt rather than remain in mantle minerals.
Cross-cutting relationships can be used to determine the relative ages of rock strata and other structures. Explanations: A – folded rock strata cut by a thrust fault; B – large intrusion (cutting through A); C – erosional angular unconformity (cutting off A & B) on which rock strata were deposited; D – volcanic dike (cutting through A, B & C); E – even younger rock strata (overlying ...