The top of the Farmington member and bottom of the overlying De-na-zin member has been radiometrically dated to 73.83 ± 0.18
ðə tˈɑːp ʌvðə fˈɑːɹmɪŋtən mˈɛmbɚ ænd bˈɑːɾəm ʌvðɪ ˌoʊvɚlˈaɪɪŋ dənˈɑːzˈɪn mˈɛmbɚ hˈæzbiːn ɹˌeɪdɪoʊmˈɛtɹɪkli dˈeɪɾᵻd tə sˈɛvənti θɹˈiː.ˈeɪɾi θɹˈiː plˈʌs ɔːɹ mˈaɪnəs zˈiəɹoʊ.ˈeɪtiːn