Radiometric age dating flaws

23 Jan

Y., reported today in the British journal Nature that some estimates of age based on carbon analyses were wrong by as much as 3,500 years.They arrived at this conclusion by comparing age estimates obtained using two different methods - analysis of radioactive carbon in a sample and determination of the ratio of uranium to thorium in the sample.But it is already clear that the carbon method of dating will have to be recalibrated and corrected in some cases.Scientists at the Lamont-Doherty Geological Laboratory of Columbia University at Palisades, N.Nd ratios on several minerals with a mass spectrometer and then from the slope determine the age of the rock. If a magma cools quickly on the surface of the Earth, some of the Ar may be trapped.The initial ratio has particular importance for studying the chemical evolution of the Earth's mantle and crust, as we discussed in the section on igneous rocks. If this happens, then the date obtained will be older than the date at which the magma erupted.We can also construct a Concordia diagram, which shows the values of Pb isotopes that would give concordant dates.The Concordia curve can be calculated by defining the following: ).

But when a plant or animal dies, it can no longer accumulate fresh carbon 14, and the supply in the organism at the time of death is gradually depleted.

Zircon has a high hardness (7.5) which makes it resistant to mechanical weathering, and it is also very resistant to chemical weathering. Chemically, zircon usually contains high amounts of U and low amounts of Pb, so that large amounts of radiogenic Pb are produced.

Other minerals that also show these properties, but are less commonly used in radiometric dating are Apatite and sphene.

The only problem is that we only know the number of daughter atoms now present, and some of those may have been present prior to the start of our clock. The reason for this is that Rb has become distributed unequally through the Earth over time.

We can see how do deal with this if we take a particular case. For example the amount of Rb in mantle rocks is generally low, i.e. The mantle thus has a low If these two independent dates are the same, we say they are concordant.