ðə bˈeɪs ʌvðə kˈɜːtlənd fɔːɹmˈeɪʃən ænd ɪts lˈoʊɪst sˈʌbjˈuːnɪt, ðə hˈʌntɚ wˈɑːʃ mˈɛmbɚ, hˈæzbiːn dˈeɪɾᵻd tə sˈɛvənti fˈaɪv.zˈiəɹoʊ tˈuː plˈʌs ɔːɹ mˈaɪnəs zˈiəɹoʊ.θˈɜːtiːn mˈɑː.
The base of the Kirtland Formation and its lowest sub-unit, the Hunter Wash member, has been dated to 75.02 ± 0.13 Ma.