tag:blogger.com,1999:blog-3728725441575309638.post394865500710068445..comments2023-10-30T08:13:43.200-07:00Comments on Questioning Answers In Genesis: Inventing the isochron: Steve Austin, Andrew Snelling, and the Cardenas Basalts of the Grand CanyonChemostrat1646http://www.blogger.com/profile/01067579479402100587noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-3728725441575309638.post-86671133704553023632011-03-30T13:54:07.922-07:002011-03-30T13:54:07.922-07:00I ran an Ar-Ar mass spec for some time, and dated ...I ran an Ar-Ar mass spec for some time, and dated many different samples, from relatively young (<20Ma) to much older (>1Ga). We did step heating, as well as core-rim ages, by means of a laser-ablation system. <br /><br />Ar-loss is very common, but could be most often accounted for within the first couple of steps. Excess Argon defintely disturbed not a few analyses, but it was quite obvious when thta happened. What you look for are repeatable plateau ages - a plateau is a continuous set of analyses in one grain, during the step-heating process, comprising at least 40% of all 39Ar released by the grain, and with results within at least 1-sigma error margin. A couple of plateau ages from different grains that are within error of each other could potentially be considered a credible result. <br /><br />Compared to the rigour of this method I find the simplicity of Snelling et al quite shocking. I met Snelling myself briefly in SA just as I started working in the Geochron lab - his comments then indicated very little understanding, and it appears that general ignorance has not progressed much.The Singular Observerhttps://www.blogger.com/profile/12427638663514348421noreply@blogger.com