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Abstract The Lower Palaeozoic in Ordos were identified with the comprehensive method of integrating the outcrop sections, well sections and seismic profiles,first integrating the synthetic seismograms and the vertical seismic profiles(VSP)of 11 wells. Totally 371 pieces and 15 683 kilometers of seismic profiles were processed and stratigraphically interpretated,which greatly upgraded the interpretation of the seismic profiles.Based on above achievements, the Lower Palaeozoic in Ordos were divided into five stratigraphical units, i.e. Lower and Middle Cambrian, Middle and Upper Cambrian and Lower Ordovician, Lower Majiagou Group, Upper Majiagou Group, and pingliang Formation and Beiguoshan Formation, and their isopach maps were compiled. These maps show that the palaeotectonic pattern of the former four ages was “one uplift and three depressions”,i.e. one middle uplift was surrounded by the western depression,southern depression and eastern depression, which together took the shape of “U”, and the palaeotectonic pattern of the last age was “one uplift and two depressions”, i.e. the huge Ordos uplift borders on the western depression and southern depression, which together took the shape of “L”. At the end of the Ordovician the Ordos and the whole North China Platform formed an unified uplift and the framework of uplifts alternating with depressions vanished.
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