However, more recent work, based on rare-earth element (REE) distributions in garnet in conjunction with Lu–Hf and Sm–Nd geochronology, indicates that protracted prograde garnet growth may be recorded by the Lu–Hf system in Norwegian and Alpine eclogites that equilibrated at temperatures up to as high as 750–850°C, even with relatively small ( estimates tend to be higher for rim than for core pairs, except for sample 07XD01.
This is in line with pseudosection modeling for eclogites that has shown that garnet grows in eclogites during prograde and peak (U)HP metamorphism ().
Using relative dating the fossil is compared to something for which an age is already known.
For example if you have a fossil trilobite and it was found in the Wheeler Formation.
The unlikely “garnet growth during near-isobaric cooling” recorded by garnet sample 07XD01 may result from the decreased robustness of the thermobarometer due to the absence of Ky.
The majority of the time fossils are dated using relative dating techniques.These isotopes break down at a constant rate over time through radioactive decay.By measuring the ratio of the amount of the original (parent) isotope to the amount of the (daughter) isotopes that it breaks down into an age can be determined.Studying the layers of rock or strata can also be useful. If a layer of rock containing the fossil is higher up in the sequence that another layer, you know that layer must be younger in age. This can often be complicated by the fact that geological forces can cause faulting and tilting of rocks.Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods.Then after another 5,000 years half of the remaining parent isotope will have decayed.