Two periods of high-pressure metamorphic belts, which have been dated 335.5 Ma and 440-460 Ma seperately by isotopic methods, have been discovered in the mid Cambrian and low-middle Ordovician strata.

• 同位素年龄分别为335.；5 Ma和440-460 Ma的两期高压变质带赋存于中寒武统和下中奥陶统中。