“…The “evolved” variety of glauconite acquires high K 2 O content because of the prolonged interaction of the glauconitic substrate with seawater (10 5 –10 6 years) at the depositional surface (Amorosi et al, ; Banerjee, Bansal, Pande et al, ; Banerjee, Bansal, & Thorat, ; Banerjee, Jeevankumar, & Eriksson, ; Giresse & Wiewióra, ; Harris & Whiting, ; Hesselbo & Huggett, ; Huggett & Gale, ; Kelly & Webb, ; Odin & Matter, ). “Evolved” glauconites occur in close proximity to the maximum flooding surface as detrital sediment input is minimal corresponding to this important sequence stratigraphic element (Amorosi, ; Amorosi, ; Banerjee, Chattoraj, Saraswati, Dasgupta, Sarkar, & Bumby, ; Banerjee, Chattoraj, Saraswati, Dasgupta, & Sarkar, ; Bansal, Banerjee, Pande, Arora, & Meena, ; Rudmin, Banerjee, & Mazurov, ). The K/Ar and 40 Ar/ 39 Ar ages of authigenic glauconite constraints the age of sedimentary sequences in the absence of age diagnostic fossils (Bonhomme, ; Clauer, Liewig, Mossem, & Chaudhuri, ; Odin, ; Odin, ; Odin, ; Rathore, Prabhu, Vijan, Vic, & Misra, and many others).…”