Early radioisotopic age constraints about the Campanian formations from the WIB consisted of K–Ar analyses of biotite and feldspar from interbedded bentonites115,116, with assumed uncertainties around the order of ± five%, and these analyses usually are not talked about additional right here. Biotite ages, specifically, are viewed as of questionable https://www.generationgenius.com/videolessons/fossil-record-video-for-kids/