Geologists use radiometric dating

Geologists use radiometric dating

Besides the papers mentioned here, there are hundreds, if not thousands, of similar papers providing bracketing ranges for fossil occurrences. So far, I know of no valid theory that explains how this could occur, let alone evidence in support of such a theory, although there have been highly fallacious attempts e. These types of distinctive events provide confirmation that the Earth's stratigraphy is genuinely successional on a global scale. Radiometric dating has simply made the estimates more precise, and extended it into rocks barren of fossils and other stratigraphic tools.

An ash bed

See archived copy instead. Prior to the availability of radiometric dating, and even prior to evolutionary theory, the Earth was estimated to be at least hundreds of millions of years old see above. An ash bed near the top of the Judith River Fm. This reconstruction is tested and refined as new field information is collected, and can be and often is done completely independently of anything to do with other methods e. In support of this pattern, there is an unmistakable trend of smaller and smaller revisions of the time scale as the dataset gets larger and more precise Harland et al.

However, this statistical likelihood is not assumed, it is tested, usually by using other methods e. To get to that point, there is also a historical discussion and description of non-radiometric dating methods. The real question is what happens when conditions are ideal, versus when they are marginal, because ideal samples should give the most reliable dates. In no way are they meant to imply there are no exceptions.

Dinosaurs and many other types of fossils are also found in this interval, and in broad context it occurs shortly before the extinction of the dinosaurs, and the extinction of all ammonites. Estimates of the age of the Earth again returned to the prior methods. Because of the short length of the carbon half-life, carbon dating is only accurate for items that are thousands to tens of thousands of years old. The data are determined by the rocks, not by preconceived notions about what will be found. The time scale is refined to reflect the relatively few and progressively smaller inconsistencies that are found.

Comparison of newer data with the Harland et al. This observation led to attempts to explain the fossil succession by various mechanisms.

It contains a mixture of minerals from a volcanic eruption and detrital mineral grains eroded from other, older rocks. Other examples yield similar results - i. The unfortunate part of the natural process of refinement of time scales is the appearance of circularity if people do not look at the source of the data carefully enough.

See archived copyPrior to the availability

It demonstrates how consistent radiometric data can be when the rocks are more suitable for dating. It depends upon the exact situation, and how much data are present to test hypotheses e. Some of these events do exist. Even in complex situations of multiple deposition, deformation, erosion, deposition, and repeated events, it is possible to reconstruct the sequence of events. If the age of this unit were not so crucial to important associated hominid fossils, it probably would not have been dated at all because of the potential problems.

Canadian Journal of Earth Sciences, v. The results are therefore highly consistent given the analytical uncertainties in any measurement. There are innumerable independent tests that can identify and resolve inconsistencies in the data. Radiometric dating provides numerical values for the age of an appropriate rock, usually expressed in millions of years.

Spore-bearing land plants like ferns were always found before the occurrence of flowering plants. It happens in all sciences. This was true at a regional, and even a global scale.