Two different age models were constructed from weighted mean U dates, comparing smoothing cubic spline and Bayesian interpolation approaches.The statistical treatment of the combined datasets allows quantification of the lower and upper limits and associated uncertainties of the two conodont biozones as well as of the FO of .
Furthermore, by the time the temperature of the granite and the hydrothermal fluids had cooled to 150ºC, the heat energy driving the hydrothermal fluid convection would have begun to wane and the vigor of the hydrothermal flow would also have begun to diminish …
The obvious conclusion has to be that if the processes of magma intrusion, crystallization, and cooling required 100,000–1 million years, then so much Po would have already decayed and thus been lost from the hydrothermal fluids by the time the granite and fluids had cooled to 150ºC that there simply would not have been enough Po isotopes left to generate the Po radiohalos …” Thus, taking all these factors into account, Snelling has concluded that the granite intrusion, crystallization, and cooling processes must have occurred together over a timescale of only about 6-10 days. Radiohalos in granites: evidence for accelerated nuclear decay.
This strategy is applied to the case of the Early–Middle Triassic boundary (EMTB) in the southern Nanpanjiang Basin in South China, aiming to obtain the most accurate age information for this boundary with an associated uncertainty.
The EMTB has been located in a sedimentary section near Monggan, Guangxi, South China, which permitted tight correlation between conodont biozones, the carbon isotopic record, and high-precision zircon U–Pb data from volcanic ashes.
Often the host rocks into which such granites have been intruded (and which are therefore older than the granites themselves) originated as fossil-bearing sediments thought by most creationists to have formed during the global Flood.
Snelling’s model, by contrast, is a hydrothermal fluid transport model, in which the Po isotopes were produced by U-238 decay in zircon crystals found in the same biotite mica flakes as the Po radiohalos (Snelling 2005).The age for the EMTB is calculated from combined interpolated data at 247.05 ± 0.16 Ma.The age model derived from Bayesian interpolation is considered to be more adapted to the present case, where discontinuous changes in sedimentation rates are expected to be important.The hydrothermal fluids released by the crystallizing and cooling granite magma flowed along the biotite cleavage planes and transported the Po isotopes from the U-238 radiocentres.The Po isotopes were then precipitated in lattice defects along the same biotite cleavage planes where sulphur, chlorine and other atoms chemically attractive to Po were located, within a millimetre or so of the U-238 radiocentres.One such individual is Robert Gentry, who holds a Master's degree in Physics (and an honorary doctorate from the fundamentalist Columbia Union College).