Early radioisotopic age constraints about the Campanian formations with the WIB consisted of K–Ar analyses of biotite and feldspar from interbedded bentonites115,116, with assumed uncertainties about the order of ± five%, and these analyses are not discussed even more right here. Biotite ages, specifically, are viewed as of questionable precision https://bookmarkinglog.com/story13178583/fossil-record-secrets