Abstract: Tectonic-sedimentary evolution history of the Early Paleozoic was further studied in the Tazhong-Bachu-Maigaiti area by using the drilling data and seismic data obtained recently. The results show that a unified large "paleo-uplift" was formed in the Tazhong-Bachu-Yubei area in the Middle Caledonian movement, which controlled the distribution of the sedimentary facies during the early and middle stage of the Late Ordovician. Thenceforth, regional differentiation and development occurred in this large "paleo-uplift" from the Late Caledonian to the Early Hercynian, which was characterized by the development and finalization of the Hetian paleo-uplift, by the formation of the NE-trend buried hill structure zones in the East Yubei area and the Tanggubasi Depression, and by the development of the NE-trend strike-slip faults in the Tazhong North Slope. The macroscopic geologic conditions for the development of the Ordovician carbonate reservoir in these areas were different due to the control of the tectonic-sedimentary evolution characteristics of the Early Paleozoic. The Tazhong-Bachu area was located in the main part of the large middle-Caledonian paleo-uplift, in which the karst reservoirs of Lower Ordovician were developed in this stage. During the Late Caledonian to the Early Hercynian, the karst reservoirs of Lower Ordovician might be developed continually in the Middle and West of Yubei area, the western Bachu area, and the NE-trend buried hill structure zones of the Tanggubasi Depression. Fractured-vuggy Ordovician reservoirs, related with the multi-period activities of the NE-trend faults, possibly developed in the Tazhong North Slope.

Key words: tectonic evolution, paleo-uplift, carbonate reservoir, Ordovician, Tazhong area, Bachu-Maigaiti area