Abstract:

Taking the Yanchang Formation in the southwestern Ordos Basin as an example, based on the studies of petrology, sedimentary characteristics, measurements of paleocurrent directions shown by outcrops, as well as framework grains and minerals in sandstones and their distribution characteristics, the paper studied the provenance and depositional characteristics of the research area. The study shown that early sediment source was mainly from the southwest of the basin with some contribution from the south. This was followed by subsequent deposition of sediments sourced from the southwestern and southern areas with some contribution from the northeast of the basin. Debris of the Chang 8 sandstone is dominated by metamorphic rocks, small amount of sedimentary and volcanic rocks. Debris of the Chang 6 sandstone is dominated by sedimentary rocks, and a small amount of metamorphic rock and volcanic rocks. The presence of more felsic materials of the late Archean in the Chang 6 sandstone suggested that the western margin of the basin uplift had undergone intensive erosion, resulting in a large number of younger strata eroded and added to the source rocks. The distribution of the Yanchang Lake basin was along northwestsoutheast. It mainly developed braided fluvial and braided delta depositional systems in the southwestern slope, meandering river delta depositional system in northeastern terrainrelief and turbidite fan deposits in the deep lake systems.

Key words: heavy mineral, provenance direction, Yanchang Formation, southwestern Ordos Basin