The North Qilian Orogenic belt and North Qinling Orogenic belt experienced a similar ocean land transformation process in the early Paleozoic Era, and developed a trench arc basin system in the convergent margin in the Ordovician Era. Consequently, it formed the northwest trending Early Paleozoic island arc and back arc basin at the northern margin of Nanshan along the North Qilian Orogenic belt corridor, and EW trending Early Paleozoic island arc and back arc basin along the North Qinling Orogenic belt, respectively. During this time, it formed a basin range coupling system between subduction accretion orogeny in the Qinling Qilian ocean and the southwestern margin and interior lake of the Ordos basin. Then, it triggered a series of tectonic events, volcanic eruptions events and various types of depositional events. There is a link among them on a series of genetic mechanisms, which have a common macroeconomic background. There is a tectonic shift from passive continental margin into active continental margin, in the western and southern margin of Ordos Basin in the almost identical period. And then it induced multi period volcanic eruption events in the Ordovician, and formed multiple sets of bentonite of Ordovician rocks in the southwestern margin of the Ordos Basin. Meanwhile, the southern margin of Ordos Basin turned into deepwater slope from shallow water carbonate platform, and developed, regularly and concentratedly, event deposits, such as gravity flow deposits (submarine fan, turbidite, etc.), slumping deposits and seismites. On the formation mechanism, the northward subduction by the South China plate triggered volcanic activity and earthquakes, and volcanic eruptions made a series of bentonites concentrated in Ordovician sedimentary rocks, seismic activity leaded to large sets of gravity flow deposits in the same period, and triggered relatively deep water sediments moving into deeper water area, making gravity flow deposits to be turbidite with good reservoirs, which constitute the main reservoir of oil and gas in deep water. Statistics show that the development time of these event deposits is consistent with the relatively most active period of tectonic activity in Qinling region. Therefore, these stable distribution thin beded bentonites and the Middle Ordovician gravity flow deposits with concentrated and regular distribution formed in the background of subduction by the South China plate, and there is a coupling relationship between them.