Geologists often will determine the relative age of a rock by carefully studying where the rock is found in the field in relation to other rocks, they have already determined the age of. However, a certain amount of circular reasoning might become involved in their determinations. At times, the age of a layer of rock will be determined by the type of fossils they contain; but then the geologist will date the fossils by the rock layer they are found in.  

In the American Journal of Science, in January of 1976, J.E. O'Rourke said: "The intelligent layman has long suspected circular reasoning in the use of rocks to date fossils and fossils to date rocks." He went on to say: "The rocks do date the fossils, but the fossils date the rocks more accurately."

In Glencoe Biology in 1994 on p. 306 it said: "Often the layers of rock can be dated by the types of fossils they contain." Then on p. 307 it says: "Scientists have determined the relative times of appearance and disappearance of many kinds of organisms from the locations of their fossils in sedimentary rock layers." So, on page 306 the rock is dated by the fossil, and on page 307 the fossil is dated by the rock it is found in.

"It is obvious that radiometric techniques may not be the absolute dating methods that they are claimed to be. Age estimates on a given geological stratum by different radiometric methods are often quite different (sometimes by hundreds of millions of years)." William D. Stansfield, Ph.D. (Instructor of Biology, California Polytechnic State U) The Science of Evolution, Macmillan 1997

If a rock specimen is found that contains fossil evidence and is believed to be less than 100,000 years old, it will most likely be dated using Carbon-14 dating. However, if the rock specimen is believed to be over 500,000 years old, a different dating method will be used such as Potassium-Argon which will usually yield a date of over 500,000 years old. If Uranium-Lead is used it will yield a date of over 100 million years old. Three different dating methods may give dates from 50,000 years old to 150 million years old and you are attempting to date the same specimen. How could we know which date was correct?

If we did not have a geologic column chart telling us approximately how old the specimen probably is, we would not know which dating method to use to get the date we want. We could use five different dating methods on the same specimen and get five different dates, and we wouldn't know which one was correct.

"In general, dates in the 'correct ball park' are assumed to be correct and are published, but those in disagreement with other data are seldom published nor are discrepancies fully explained." Richard L. Mauger, Ph.D. (Associate Professor of Geology, East Carolina University) ...Contributions to Geology, University of Wyoming, vol. 15 (1), 1977 p. 37

Questionable Assumptions

1. The decay rates have always been the same.

2. No daughter element was already present in the specimen.

3. The specimen has not been affected by heat or pressure.

4. No parent or daughter elements have entered or left the specimen at any time.

5. In the case of carbon-14 it is assumed it has always formed in our atmosphere at the same rate.

The fact is that parent or daughter elements can move through the rocks. Heating and deformation of the rocks can cause these to migrate. Water percolation can also transport them and redeposit them and leaching occurs. Exposure to radiation can change isotopic ratios or the decay rates. Many of the parent and daughter elements are water soluble. Argon can travel from rock to rock when one rock is heated, and argon is soluble in magma.

Radiocarbon Testing Sometimes Inaccurate

“The British Science and Engineering Research Council (which funded the installation of the C14 apparatus at Oxford) ran a series of tests in 1989 with 38 laboratories involved worldwide.” … Dr. Baxter reports: “It came out very badly in the survey, even when dating samples as little as 200 years old. Only 7 out of 38 laboratories produced satisfactory results, and the margin of error with artefacts of known age was two to three times greater than the technique’s practitioners claim.

Nature (the magazine which published details of the original C14 experiment) has now published a demonstration that the radiocarbon technique is not only unsound but also outdated. The Geological Observatory of Columbia University in New York has proved that the C14 results given in past years are in error by as much as 3,500 years in dating fossils, artefacts and events of the past 40,000 years, and the further back we go in time, the greater the error.”

Dating a Woolly Mammoth

A number of years ago near Midland, MI it was believed that a farmer had unearthed the body of a Woolly Mammoth. A scientist was called in to date the age of the specimen. Through scientific testing it was determined the Mammoth was approximately 23,000 years old. That seemed to fit the age that was expected. But then an elderly gentleman came forward with an interesting revelation. He said back in the 1930's the circus came to town. One day one of their elephants died, and they had paid him to bury the one they were looking at. He said: "I might look 23,000 years old but I'm not." It was very embarrassing for the scientist. Was this error related to his scientific method of dating, or his starting assumptions?