"Carbon dating is not used to date fossils." ANYMORE.
This is very key.
Carbon dating was the first and only method of dating for 10 years.
The "new" parent-daughter dating methods run into the same problems as carbon dating though they fix the radioactive halflife issue.
You cannot date any fossil properly without knowing how much of the parent substance there was to begin with. Any fossil rich in the parent substance (be it argon, or potassium, etc.) would give inaccurate data. You can't know how much time has passed if you don't know how much sand was in the hourglass to begin with. This is pretty basic.
Levels of all radioactive parent substances differ worldwide, and even in specific areas at different times change. We do our best to measure changes, then extrapolate this data backwards, but any catastrophic change in conditions will influence levels greatly, and again, give us a false date.
Taking a closer look at the fossils themselves, instead of relying on radioactive dating itself can give some insight into the actual dates. Scientists have found fossilized lobster shells from lobsters that are STILL ALIVE. Carbon dating claimed them to be over a thousand years old. But the lobster was still ALIVE.
This shows two things. Firstly, that carbon dating is not an exact science, and since the other methods of radiocarbon dating use the same process, it is possible to question their dates as well. The second, that fossilization can occur rapidly. This is also evident with fossils of mammoth graveyards, Mammoths in the middle of giving birth and in the middle of battle. Lizards with their tongue sticking out, etc. These are all examples of fast fossilization.
Lets finish with this question. How long does it take to make a fossil? Does a long time seem reasonable? Would the structure of the animal remain intact for millions of years? Just askin.
"Secondly, it is the ratio of parent to daughter isotope that is used. For example, if you start with 1 g of uranium after 1 halflife you will have 0.5 g of uranium and 0.5 g of lead. If you start with 5 g of uranium then after one half life you will have 2.5 g of uranium and 2.5 g of lead. It is the RATIO that is important."
Right, but you know what the initial levels of the parent substance are present. You are assuming that niether the parent or daughter substance can seep into surrounding ground, even though fossils occur in sedimentary rock. This is amusing at best. As well, any catastrophic event (ice age, flooding, etc.) would almost certainly effect levels of many substances in the area, or worldwide, depending on the severity of the occurance.
"Last I checked an hourglass is a closed system so the amount of sand in the hourglass is how much you started with."
Correct. And if an hourglass is half passed, then we can measure the rate at which the sand falls, and find out how long the hourglass has been tipped. But if you left the room, and I took sand out of the top, then you came back, you would guess incorrectly, based on the amount of sand present.
"This is what causes the older date. Scientists know all about this effect."
And yet do not account for it.
Since Carbon-14, as well as many other radioactive parent substances do not decay at a constant rate (decay rates vary depending on temperature, pressure, electron screening, as well as the fluctuation of the Van Allen belt), and the varying levels of carbon worldwide (8.5% margins), it seems almost impossible for an accurate timescale to be drawn based on any form of radioactive decay. As well, any daughter substance buried with the animal, but not occuring through radioactive decay would give false readings, making the fossil appear older.
"By far the most widely used method, U-Pb, takes advantage of the fact that significant amounts of lead physically and electrically can't get into minerals such as zircons at solidification"
When Zircons (or other gems, such as monazite) form, they exclude lead, but can have considerable levels of Uranium. As the Uranium decays, lead is produced. Sounds logical. Except you still do not know the levels of Uranium to begin with.
quote:As with other isochron methods, the U-Pb isochron method has been questioned in the open literature, because often an excellent line of best fit between ratios obtained from a set of good cogenetic samples gives a resultant �isochron� and yields a derived age that has no distinct geological meaning. At Koongarra, Australia, U-Th-Pb isotopic studies of uranium ore, host rocks and soils have produced an array of false isochrons that yield ages that are geologically meaningless.
Andrew A. Snelling, Ph.D.
quote:It is not uncommon to find that �ages� derived from standard 207Pb/206Pb plots are erroneous, even though the data fit well-defined linear arrays ('isochrons').14
", that has nothing to do with Carbon 14. Try one of RAZD's correlation threads."
I posted this to respond to what I thought I read about U-Pb dating...I can't find it now, but whoever thats for, it's there.
quote:Beck and colleagues tested slices of a half-metre long stalagmite that grew between 45 000 and 11 000 years ago in a cave in the Bahamas. Stalagmites are calcium carbonate deposits left behind when carbon dioxide evaporates out of cave seepage water. They found that carbon-14 concentrations were twice their modern level during that period. Current records of the levels of carbon-14 in the atmosphere only cover the last 16 thousand years, and this discovery extends those records a further 30 thousand years.
Galactic cosmic rays create most of the carbon-14 in our atmosphere, while solar cosmic rays generate a smaller fraction. The Earth is partially shielded from galactic cosmic rays by its own magnetic field and the solar magnetic field, which fluctuates as the solar cycle proceeds. But these effects are predictable and are thought to have changed little in the last million years - which means they cannot explain the glut of carbon-14. Evidence from North Atlantic sediments suggests that the Earth's magnetic field may have dipped around 40 thousand years ago, but this would still only account for - at best - half of the observed peak in carbon-14 concentrations.
Beck's team concludes that either a jump in the cosmic ray flux or a fundamental change in the carbon cycle must have produced the sudden increase of carbon-14. The team speculates that a supernova shock wave could have produced a flurry of cosmic rays. "Weaker circulation of the oceans - which are the biggest reservoirs of carbon on Earth - would explain the excess of carbon-14", David Richards, joint team leader, told PhysicsWeb. If carbon-14 is carried more slowly from the surface to the depths of the ocean, he explains, the carbon-14 content of the atmosphere will rise.
quote:Measurable 14C in pre-Flood organic materials fossilized in Flood strata therefore appears to represent a powerful and testable confirmation of the young earth Creation-Flood model. It was on this basis that Snelling [37-41] analyzed the 14C content of fossilized wood conventionally regarded as 14C ‘dead’ because it was derived from Tertiary, Mesozoic, and upper Paleozoic strata having conventional radioisotope ages of 40 to 250 million years. All samples were analyzed using AMS technology by a reputable commercial laboratory with some duplicate samples also tested by a specialist laboratory in a major research institute. Measurable 14C was obtained in all cases.