#mincup25 — Public Fediverse posts
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#Sanidine from the Fish Canyon Tuff is essential to understanding the pace of events in the #Cenozoic
High potassium, quickly erupted and cooled, and old enough to have accumulated sufficient 40Ar from radioactive decay. These crystals calibrate neutron flux for 40Ar/39Ar dating. The 28.2 Ma age of the FCT sanidine has been fine-tuned using #Milankovitch cycles of other ash beds in stable sedimentary basins.
photo from MinDat.org by Dan Polhemus