Carbon dating fact fiction
These include some that establish a relative chronology in which occurrences can be placed in the correct sequence relative to one another or to some known succession of events.
For example, the presence of recycled bricks at an archaeological site indicates the sequence in which the structures were built.In the ideal case, the geologist will discover a single rock unit with a unique collection of easily observed attributes called a marker horizon that can be found at widely spaced localities.Any feature, including colour variations, textures, fossil content, mineralogy, or any unusual combinations of these can be used.Similarly, in geologic studies, vast quantities of information from widely spaced outcrops have to be integrated.Some method of correlating rock units must be found.With time, water-soluble “cement” will cause the sandy units to become sandstone.
Rocks of this kind in the ancient record may very well have resulted from rapid uplift and continent collision.
Similarly, in geology, if distinctive granitic pebbles can be found in the sediment beside a similar granitic body, it can be inferred that the granite, after cooling, had been uplifted and eroded and therefore was not injected into the adjacent rock sequence.
Although with clever detective work many complex time sequences or relative ages can be deduced, the ability to show that objects at two separated sites were formed at the same time requires additional information.
Just as the use of the fossil record has allowed a precise definition of geologic processes in approximately the past 600 million years, absolute ages allow correlations back to Earth’s oldest known rocks formed more than 4 billion years ago.
In fact, even in younger rocks, absolute dating is the only way that the fossil record can be calibrated.
When rocks are subjected to high temperatures and pressures in mountain roots formed where continents collide, certain datable minerals grow and even regrow to record the timing of such geologic events.