MesozoicCretaceousCenomanian PaleozoicDevonianGivetian CenozoicPaleoceneThanetian Using Index Fossils
Dating in Geology 1) Relative dating –a) Superposition –b) Correlation 2) Numerical (absolute) dating –radiometrics
Radiometric Dating: the basic idea A product is detectable The rate of production of that product is known Product amount is 0 (or known) at age 0 of sample Product / Rate = Time –example:10g / 0.5g/yr = 20 years
IsotopesIsotopes: elements with the same atomic number but different atomic mass (number of neutrons). Some isotopes unstable ( 40 K, 14 C; radioisotopes); others are stable ( 39 K, 41 K, 12 C, 13 C) Unstable isotopes (parent) decay to another stable or unstable isotope (daughter) Rate expressed as half-life -- time in which ½ of radioisotopes decay.