The event deposits from the Yanchangian lacustrine basin in the Ordos Basin

The turbidites, seismites and tuffs may be discriminated in terms of their vertical sedimentary sequences. The event deposits from the Yanchangian lacustrine basin in the Ordos Basin were initiated during the Chang-6 to Chang-8 stages. In a planar view, they are arranged in the deep-lake area in the southwestern part of the basin. The mechanisms for the formation of the event deposits have disclosed that the tectonic movements tend to give rise to the volcanic activities, followed by severe earthquakes. The earthquakes, in turn, may cause the braided delta front deposits to migrate toward the deep-lake area. All the event deposits outlined above are closely associated with hydrocarbon accumulation. The turbidites and seismites have certain reservoir potential, and thus may act as the main reservoir rocks in the deep-water areas. The tuffs may stimulate the formation and evolution of the excellent source rocks.