Problems with understanding fossils dating

[heartless]

We're using, Concepts in Modern Biology. On page 410, it says that layers of rock determine the age of a fossil, and few lines later that using a fossil we may determine the age of the layer. Does it work in this way that, they determine the age of the fossil using radioactive dating and then identify the age of rock, or they don't use the ractive dating for that? And guess?
Thanks,

 

[matthyaouw]

It does work both ways, but only if you have a good understanding of the sequence of rocks and the fossils they contain. If you find a new exposure with fossils you know appear only in mid jurassic rocks, you can place a fairly safe bet that these rocks are mid jurassic too. There are some very good indicator fossils that changed form quickly and lived short durations that can pin a rock age down to within a few million years. likewise you can use stratigraphy to determine the relative ages of a fossils- one higher up in a sequence will just about always be younger. For an absolute date (the fossil is x million years old) you will need some radioactive dating at some point, but sometimes relative dating (x is older than y, which is older than z) is enough. Pretty much all of the sedimantary rock in the UK had been given a relative age and assigned to a period on the geological column before radioactive dating was invented, so it goes to show that stratigraphy and fossil evidence work pretty well for dating rocks relative to each other.

 

[ravenprp]

The process of dating fossils and determining the age of rock layers is a complex and constantly evolving field in biology. While it is true that layers of rock can be used to determine the age of a fossil, it is not the only method used. Fossils can also be dated using various forms of relative and absolute dating techniques, including radioactive dating.

In radioactive dating, scientists measure the amount of radioactive isotopes present in a fossil to determine its age. This method is based on the principle that radioactive isotopes decay at a constant rate over time. By comparing the amount of radioactive isotope to the amount of its decay product, scientists can calculate the age of a fossil.

However, there are limitations to this method. For example, the accuracy of radioactive dating can be affected by factors such as contamination, sample size, and the type of radioactive isotope used. Therefore, scientists often use a combination of dating techniques to get a more accurate estimate of a fossil's age.

To answer the question of whether the age of the fossil is used to determine the age of the rock layer or vice versa, it is important to note that the age of the fossil and the age of the rock layer are not always the same. Fossils can be found in layers of rock that are much older or younger than the fossil itself. Therefore, the age of the fossil is used to determine the age of the rock layer in which it is found, but the age of the rock layer does not necessarily determine the age of the fossil.

In conclusion, while there may be some limitations and complexities in dating fossils and rock layers, scientists use a variety of techniques, including radioactive dating, to determine the age of fossils. It is an ongoing and constantly evolving process, and new advancements in technology and understanding are constantly being made to improve the accuracy and reliability of dating methods.