The so-called ‘absolute’ (physical, numerical) methods, and especially those based on exposure age dating with in situ cosmogenic radionuclides, are appealing because they produce direct numerical ages, and appear to be widely applicable, but there are severe temporal limitations, and sampling problems complicate, and may invalidate, interpretation.
Absolute age determinations must be consistent with the stratigraphic and geomorphologic settings.
These span fields like calibrating radiometric dating methods, reconstructing past changes of the Earth's magnetic field or detecting fluctuations in solar forcing.
Once a varve chronology is established it can be applied to precisely date events like volcanic ash layers, earthquakes or human impact, as well as short- and long-term climate (temperature, precipitation, wind, hydroclimatic conditions or flooding) and environmental changes (eutrophication, pollution).
The discovery of small numbers of fossils has caused huge changes in theories of human evolution, perhaps indicating that too much has been constructed on too little.
Conversely, discoveries such as those made in Dmanisi, Georgia provide examples of falsification of earlier held positions, indicating why paleoanthropology can be considered a science.
Due to their exceptional high temporal resolution and in combination with their robust and accurate “internal” time scale in calendar years, annually laminated sediments can be regarded as one of the most precious environmental archives on the continents.
These records are necessary to extend temporally limited instrumental records back in time.
There are no temporal limits to relative dating, for the methods are equally applicable to the dating, say, of Proterozoic surfaces as of those of Pleistocene age.
The disadvantage of such methods is that the necessary evidence is frequently either not preserved or not exposed.
Various predominating climatic and depositional conditions may result in clastic, biogenic or endogenic (incl. To reliably establish a varve chronology, the annual character of laminations needs to be determined and verified in a multidisciplinary fashion.
Sources and influences of possible errors in varve chronologies are best determined and constrained by repeated varve counts, and by including radioisotopes and correlation with historically documented events.
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