NEW CHRONOSTRATIGRAPHIC CONSTRAINT ON LATE JURRASIC (?) – EARLY CRETACEOUS SEDIMENTATION IN THE DISTAL CORDILLERAN FORELAND BASIN IN NORTHERN NEW MEXICO
Detrital zircon ages from these intermediary strata overlap in age with the Yavapai and Mazatzal provinces (1800-1600 Ma), A-type Granitoids (1500-1350 Ma), and Grenville province (1300-1000 Ma). Latest Precambrian and Mesozoic peak ages overlap with Neoproterozoic-Jurassic zircons that span from 620-300 and 220-170 Ma and are interpreted to represent recycled Mesozoic eolianites of the Colorado Plateau. Jurassic ages are common and overlap with magmatic sources of the Cordilleran Arc, whereas Early Cretaceous zircons are extremely rare (limited to a single zircon). Maximum depositional ages for the youngest stratigraphic horizons support a latest Jurassic–Early Cretaceous age for the Jackpile Sandstone (143–147 Ma), and Lytle Sandstone (150–152 Ma).
Although these new ages support a Late Jurassic–Early Cretaceous age for these strata, there are scenarios where they could be interpreted to be younger in age. It is certainly possible that latest Jurassic zircons represent reworked, air-fall tuffs from the Cordilleran arc, thus absences of young Cretaceous grains could be interpreted as a temporary hiatus in air-fall material to the strata during the Early Cretaceous.