Abstract: Sediments in the Hefei basin to the north of the Dabie orogen are important records of unroofing history for the orogen．K-Ar dating of authigenic illite proves that strata in drill-hole Ancan-1 from top to bottom are lower Cretaceous，upper-mid-lower-Jurassic．lower Permian and upper Carboniferous strata which are probably underlain by Ordovician strata．Detrital composition analysis of the Mesozoic sandstones indicates that their provenance is the Dabie orogen．Lower Permian sandstones in drill-hole Ancan-1 do not contain detrital phengite from orogen．Rich phengite(Si>3．3)detritus occurs continuously in sandstones from lower Jurassic to lower Cretaceous strata in the dril1-hole．This shows that the Dabie orogen is main provenance for the Hefei basin．and indicates that HP to UHP metamorphic rocks of the orogen were unroofed since the earliest Early Jurassic and exposed continuously since then．