Radiometric dating detrital minerals sedimentary rocks gives
Rocks that cool within the Earth’s crust, intrusive igneous rocks, cool slowly and thus have coarse crystalline grains, whereas, rocks that cool on the surface of the Earth, extrusive igneous rocks, cool relatively quickly.As the cooling happens much faster in extrusive rocks than intrusive rocks, the minerals do not have time to congregate with one another and thus form fine-grained rock.The Auckland Islands consist mainly of basalt, but there are also some occurrences of granite, gabbro, sandstone, conglomerate and limestone.Basalt, granite and gabbro are all igneous rocks – they form when magma rises from the mantle and cools.This dating method works by looking at the atomic structure of the sample.All rocks are composed of atoms, each atom having a nucleus containing protons and neutrons. Those that are not are called radioactive isotopes.Limestone is what is known as a chemically precipitated sedimentary rock.These rocks form when mineral compounds accumulate at the bottom of oceans or inland lakes.
So in order to determine the age of a rock sample, geologists compare the amount of the original isotope in the sample with the amount of the decayed end product – the daughter atoms.The Auckland Islands lie approximately 375km south of Stewart Island on the Campbell Plateau.These islands were formed by multiple geological events.Conglomerate is a type of sandstone that contains a wide variety of particle sizes.
Both sandstone and conglomerate are what is known as clastic sedimentary rocks, where mineral fragments from any of the three major rock groups accumulate and lithify (compact and cement).
Absolute ages and relative stratigraphy can then be cross correlated to justify the evidence related to dating the geological events.