Detrital zircons from fluvial Jurassic strata of the Michigan Basin; implications for the transcontinental Jurassic paleoriver hypothesis

The U-Pb age spectrum of detrital zircons in sandstone of the fluvial Middle Jurassic Ionia Formation in the Michigan basin, United States, resembles the age spectra in Jurassic eolianites of the Colorado Plateau, except that a Neoproterozoic (725-510 Ma) subpopulation present in the eolianites is absent from the Michigan basin strata. The detrital zircon data are compatible with the hypothesis that the Ionia Formation was deposited by northern tributaries of a transcontinental Jurassic paleoriver system that transported detritus from headwaters in Atlantic rift highlands of the Appalachian region to floodplains and deltas in the present northern Rocky Mountains region. Previous detrital zircon studies have indicated that sedimented lowlands in that paleogeographic position were deflated by paleowinds to feed eolian sand southward (in present coordinates) into the Colorado Plateau ergs (sand seas).