What is the reason for dating fossils? Not romantically of course.?

Question

What is the logic behind the dating of fossils? Assuming that the minerals of the earth have a maximum age of 4.65 billions years, is that the age all fossils are dated as, since they have replaced all organic material with rock? And then the different strata layers seperate into different periods? Or do the fossils actually have a different range of years as in one being 700 million years or another one being 1.3 billion years. Example. Someone finds a fossil. They date it. The result comes came 4.6 billion years. But it is in the jurassic layer of earth, so they know it came later on in history and the big number only shows the age of minerals it is made of. I am only assuming, I don't know. If someone could confirm my assumtion or correctly inform me, that would be great. thanks

Answer 1

The absolute ages (ie. x million years old) placed on fossils come about as a consequence of the science of Geology. Radiometric dating, such as uranium-lead, and potassium-argon, is used to get the absolute ages of suitable minerals when they are found. Only a few minerals are suitable, eg. zircon crystals and volcanic ash beds. Geologists due this because it is important for unraveling geology (the source of all our metals and petroleum).

So, for example, we know that the Jurassic Period lasted from 199.6 ± 0.6 to 145.4 ± 4.0 million years ago. And at a finer scale, we know that the Toarcian stage, within the Jurassic Period, lasted from183.0 ± 1.5 to175.6 ± 2.0 Ma. And so on for sub-stages of the Toarcian.

So when you recover a fossil from strata which is correlated to the early Toarcian, you know roughly how many millions of years old it is.

Answer 2

Usually fossils themselves are noted dated because they do not contain the right minerals to be dated.

Normally a volcanic deposit over or below the fossil can be dated usind say uranium - lead ratios. This will then givs an idea of the age of the fossil.

If the volcanic bed is dated at say 90 million years old and the fossil occurs just below it, then the fossil is a bit older than 90 million years.

There are also ways of cross-checking the ages of fossils.

Answer 3

One aspect I didnt see covered was that when rock is heated and melted (forming magma or lava) the resolidification results in a new composition of minerals and elements allowing the carbon dating of that rock to reset. Therefore, it is a new rock and because of this not all rocks are the same "age" (age referring to the time at which they were solidified and their mineral composition "set in stone" no pun intended). Using this knowledge as well as compiling information from sedimentary layers we are able to ascertain the approximate age of a given layer of earth and therefore we can date fossils and create fossil records with definitive knowledge accurate to within a few million years. Dating of the fossils themselves is not as relevant as the layers by which they are contained as they exist because the calcium in the bones was replaced by rock over time. Carbon dating is the practice of measuring the radioactive decay of isotopes of Carbon (typically C-14) to which they've made accurate measures and can thereby create a geological timetable based on that information.

To address Caseypayne's statement:
They do know when the radioactive decay started by using simple subtraction. Measuring how many isotopes have decayed vs. how many havent gives the necessary info to work backwards using the half-life of a specific element (which is easily measurable and calcuable) to the point at which that rock solidified (It has nothing to do with carbon in the air, i believe you are referring to CO2 which has no bearing on this topic). Such as in the case of the cretacious-terciary extinction WHICH WAS 65 MILLION YEARS AGO. One just has to assume that up is up and down is down and that the universe exists with a set of rules. By that logic, and without proof of breaking the rules, physics must be uniform and a time period exists by following that uniformity. If you don't believe that the universe exists with a set of rules then I suggest you be careful or you may one day end up floating into the sky because gravity no longer ties you to the earth.

As for evolution, see my answer to "Is it Crazy to believe Dinosaurs roamed with humans? Christians are crazy?" as i touch on the subject in that one.

Answer 4

Details of carbondating and also isotopes being used are from the source shown:
People who ask about carbon-14 (14C) dating usually want to know about the radiometric1 dating methods that are claimed to give millions and billions of years—carbon dating can only give thousands of years.
Carbon has unique properties that are essential for life on earth. Familiar to us as the black substance in charred wood, as diamonds, and the graphite in ‘lead’ pencils, carbon comes in several forms, or isotopes. One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or 14C, or radiocarbon.
Scientists can use different chemicals for absolute dating:
The best-known absolute dating technique is carbon-14 dating, which archaeologists prefer to use. However, the half-life of carbon-14 is only 5730 years, so the method cannot be used for materials older than about 70,000 years.
Radiometric dating involves the use of isotope series, such as rubidium/strontium, thorium/lead, potassium/argon, argon/argon, or uranium/lead, all of which have very long half-lives, ranging from 0.7 to 48.6 billion years. Subtle differences in the relative proportions of the two isotopes can give good dates for rocks of any age.
Scientists can check their accuracy by using different isotopes. The first radiometric dates, generated about 1920, showed that the Earth was hundreds of millions, or billions, of years old. Since then, geologists have made many tens of thousands of radiometric age determinations, and they have refined the earlier estimates. A key point is that it is no longer necessary simply to accept one chemical determination of a rock's age. Age estimates can be cross-tested by using different isotope pairs. Results from different techniques, often measured in rival labs, continually confirm each other.
There is only a 1% chance of error with current dating technology. Every few years, new geologic time scales are published, providing the latest dates for major time lines. Older dates may change by a few million years up and down, but younger dates are stable. For example, it has been known since the 1960s that the famous Cretaceous-Tertiary boundary, the line marking the end of the dinosaurs, was 65 million years old. Repeated recalibrations and retests, using ever more sophisticated techniques and equipment, cannot shift that date. It is accurate to within a few thousand years. With modern, extremely precise, methods, error bars are often only1% or so.
VR

Answer 5

You have to remember that dating fossils, especially by evolutionist, is never truthful. Dinosaurs roamed the earth during human life.

Scientist miss guidlingly date fossils to try and help darwin theory. Because according to the false beliefs of darwin, all life came from a single celled organism and spawned like a tree created all forms of life. Which is false and darwin theory is evaporating. Wonder why there are missing links in fossils? because the connection of evolution is a false belief and we are not evolutionizing. Life began some 8 to 14 thousand years ago, not millions or billions. Carbone dating is inaccurate because they have to know the carbon in the air of the orgins of time which they don't. Radiation dating isn't accurate because they have to know when the decay started or how and they don't.

Remember to view things from all angles.

Answer 6

There are lots of descriptions for C14 dating on the web. I found the info below at: http://www.c14dating.com/int.html.

Keep in mind that there are lots of other dating methods beside radio carbon - or C14. Radiometric dating involves the use of isotope series, such as rubidium/strontium, thorium/lead, potassium/argon, argon/argon, or uranium/lead, all of which have very long half-lives, ranging from 0.7 to 48.6 billion years. Subtle differences in the relative proportions of the two isotopes can give good dates for rocks of any age.

The 14C Method

There are three principal isotopes of carbon which occur naturally - C12, C13 (both stable) and C14 (unstable or radioactive). These isotopes are present in the following amounts C12 - 98.89%, C13 - 1.11% and C14 - 0.00000000010%. Thus, one carbon 14 atom exists in nature for every 1,000,000,000,000 C12 atoms in living material. The radiocarbon method is based on the rate of decay of the radioactive or unstable carbon isotope 14 (14C), which is formed in the upper atmosphere through the effect of cosmic ray neutrons upon nitrogen 14. The reaction is:

14N + n => 14C + p

(Where n is a neutron and p is a proton).
The 14C formed is rapidly oxidised to 14CO2 and enters the earth's plant and animal lifeways through photosynthesis and the food chain. The rapidity of the dispersal of C14 into the atmosphere has been demonstrated by measurements of radioactive carbon produced from thermonuclear bomb testing. 14C also enters the Earth's oceans in an atmospheric exchange and as dissolved carbonate (the entire 14C inventory is termed the carbon exchange reservoir (Aitken, 1990)). Plants and animals which utilise carbon in biological foodchains take up 14C during their lifetimes. They exist in equilibrium with the C14 concentration of the atmosphere, that is, the numbers of C14 atoms and non-radioactive carbon atoms stays approximately the same over time. As soon as a plant or animal dies, they cease the metabolic function of carbon uptake; there is no replenishment of radioactive carbon, only decay. There is a useful diagrammatic representation of this process given here

Libby, Anderson and Arnold (1949) were the first to measure the rate of this decay. They found that after 5568 years, half the C14 in the original sample will have decayed and after another 5568 years, half of that remaining material will have decayed, and so on (see figure 1 below). The half-life (t 1/2) is the name given to this value which Libby measured at 5568±30 years. This became known as the Libby half-life. After 10 half-lives, there is a very small amount of radioactive carbon present in a sample. At about 50 - 60 000 years, then, the limit of the technique is reached (beyond this time, other radiometric techniques must be used for dating). By measuring the C14 concentration or residual radioactivity of a sample whose age is not known, it is possible to obtain the countrate or number of decay events per gram of Carbon. By comparing this with modern levels of activity (1890 wood corrected for decay to 1950 AD) and using the measured half-life it becomes possible to calculate a date for the death of the sample.

Answer 7

I would guess you are correct, but from what I have read the layers of earth has changed so much, there is no original layer of earth. Interesting question though because I don't even know if they have found any bone structure that is even one Billion years old.

Answer 8

Don't know much about the methods employed to date fossils but i know that it is done mainly to establish a chronology in evolution, and the evolutionary history has proved to be useful knowledge for humans beings till now.

Answer 9

I simply do not see the logic of scientists dating fossils, even if it's just as friends. I like old rocks myself, but I am not about to buy dinner for one or take one to the movies.

Answer 10

Oh ok, I thought you meant dating older people. -- the answer to that is cos older people have thicker wallets.

dating other fossils? Who cares