ðə bˈoːɹdɚ bᵻtwˌiːn ðə hˈʌntɚ wˈɑːʃ mˈɛmbɚ ænd ˌoʊvɚlˈaɪɪŋ fˈɑːɹmɪŋtən mˈɛmbɚ dˈeɪts tʊ ɐpɹˈɑːksɪmətli sˈɛvənti fˈoːɹ mˈɪliən jˈɪɹz ɐɡˈoʊ.
The border between the Hunter Wash member and overlying Farmington member dates to approximately 74 million years ago.