Studied the fluid inclusions and stable isotopes in the fillings of Lower Paleozoic dissolve burrows on the southeast margin of Ordos

four discontinuous temperature sequences were recovered:44—46℃

59—61℃ and 104—118℃ were Caledonian orogenic stage

156—169℃ was Hercynian orogenic stage.Therefore

it might be considered that organic matter of Lower Ordovician was mature in Caledonian stage and turned into gas in Her-cynian.According to the paleotemperature of the bottom of Majiagou Formation in LowerOrdovician and the deep water characters of Middle-Upper Ordovician on the basin periphery

it is suggested that the internal basin had received Middle-Upper Ordovician sediments which were eroded after Caledonian orogeny.