500 ka precipitation record from southeastern Australia: evidence for interglacial relative aridity.
A large drop in atmospheric 14C/12C and reduced melting in the Younger Dryas, documented with 230Th ages of corals.
Most of the fossil corals in the elevated reef terraces along the Gulf of Aqaba (GOA) were extensively altered to calcite.
This observation indicates extensive interaction with freshwater, possibly when the terraces passed through a coastal aquifer that existed along the shores of the GOA, implying a wetter climate during the time of recrystallization from aragonite to calcite.
Thus, dating of the recrystallization events should yield the timing of past wetter conditions in the current hyper-arid area of the GOA.
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Uranium-thorium dating has an upper age limit of somewhat over 500,000 years, defined by the half-life of thorium-230, the precision with which we can measure the thorium-230/uranium-234 ratio in a sample, and the accuracy to which we know the half-lives of thorium-230 and uranium-234.
Note that to calculate an age using this technique the ratio of uranium-234 to its parent isotope uranium-238 must also be measured.
Thorium-230 is itself radioactive with a half-life of 75,000 years, so instead of accumulating indefinitely (as for instance is the case for the uranium-lead system), thorium-230 instead approaches secular equilibrium with its radioactive parent uranium-234.