Please explain how the flood would have affected U-Pb dating.
Thus creationists need not be hindered in building their Creation-Flood young-earth model for the geological record by the many claims in the open geological literature that U-Th-Pb radiometric ‘dating’ has ‘proved’ the presumed great antiquity of the earth, and the strata and fossils of the so-called geological column. Accordingly, all the apparent isochron and other ‘ages’ that have been referred to here have been quoted as millions of years (Ma) purely in order to reveal the shortcomings of the U-Th-Pb ‘dating’ method. Indeed, even the use of conventional geological era terms such as ‘Archaean’ and ‘Lower Proterozoic’ has been for convenient reference to the rock units under discussion, there being no absolute ‘age’ significance attached to these terms here - only a relative position within the overall rock record. There is clearly a real sequence of rock units that comprise the total geological record, from the so-called Archaean to the Recent, the formation of which needs to be understood and coherently modelled within the biblical framework of a recent Creation and global Flood. Much progress towards this goal has been, and is being, made within the relatively small creationist geological community. Thus the mounting evidence that the claimed ‘absolute dating’ methods, such as U- Th-Pb radiometrics, are unreliable at best, and in reality produce many results that are impressive but geologically meaningless, can only assist in this quest.
http://www.answersingenesis.org/tj/v9/i1/dating.asp