Geologic age dating methods
Geologic age dating methods - online dating branding
Among these metamorphosed volcanic strata are amphibolites, belonging to the Brahma Schist.These were originally basalt lava flows several meters to tens of meters thick.
The "age" or "date" is calculated from the amount of the daughter isotope produced by radioactive decay of the parent isotope.Using the basic ideas of bracketing and radiometric dating, researchers have determined the age of rock layers all over the world.This information has also helped determine the age of the Earth itself.Some of the isotopes used for this purpose are uranium-238, uranium-235 and potassium-40, each of which has a half-life of more than a million years.Unfortunately, these elements don't exist in dinosaur fossils themselves.All 27 samples were sent to two well-credentialed internationally-recognized, commercial laboratories for radioisotope analyses—potassium-argon (K-Ar) at a Canadian laboratory, and rubidium-strontium (Rb-Sr), samarium-neodymium (Sm-Nd), and lead-lead (Pb-Pb), at an Australian laboratory.
Both laboratories use standard, best-practice procedures on state-of-the-art equipment.
In Grand Canyon, the "date" of metamorphism of the basalt lavas to form these Brahma amphibolites has been determined as 1690-1710 Ma (million years ago), based on U-Pb dating of minerals in the overlying Vishnu Schist and underlying Rama Schist that formed during the metamorphism.
It is also claimed that the original basalt lavas were erupted between 17 Ma, based on U-Pb dating of "original" zircon grains in metamorphosed felsic (granitic) volcanic layers within the Brahma and Rama Schists.
Twenty-seven Brahma amphibolite samples were collected from various Inner Gorge outcrops as part of the RATE (Radioisotopes and the Age of The Earth) project.
These included seven samples from a 150 meter long and 2 meter wide amphibolite body outcropping just upstream from the mouth of Clear Creek at river mile 84 (measured from Lees Ferry).
But this sediment doesn't typically include the necessary isotopes in measurable amounts.