Characteristics and paleogeographic pattern of source-to-sink system of the Jurassic Yan’an Formation in Ordos Basin

The middle-Jurassic Yan’an Formation in Ordos Basin is a set of coal-bearing clastic strata influenced by multiple source systems of the peripheral orogenic belt after the lag effect of the Indosinian movement. The coal and oil-gas resources show great exploration potential. This paper investigates the provenance analysis based on the characteristics of light minerals, heavy minerals, paleo-flow, major, trace and rare earth elements. And the characteristics of source-to-sink system of Yan’an Formation in Ordos Basin are studied based on previous research results. The result shows that the Yan ’an Formation in Ordos Basin is influenced by four source-to-sink systems from Yinshan ancient land in the north, Alxa ancient land in the northwest, Qilian ancient land in the southwest and north Qinling orogenic belt in the south. This paper deepens the understanding of paleogeographic pattern on the basis of source-to-sink system partition: on the basis of the ravines crossbar landform in the pre-Jurassic period, the Yan’an Formation was influenced by the difference of weathering, denudation-transport and deposition processes in four different ancient terrigenous source areas. Yan’an Formation formed continental coal-bearing clastic rock deposits with Yan’an in the middle-Jiyuan in the southeast as the depositional center. Alluvial fan-braided river-meander river-delta-lake deposition changes from basin margin to catchment area in an orderly manner. The northwestern and northern source-to-sink system has the largest sedimentary scale. And it is the focus of basin exploration. It is concluded that the results have theoretical and practical significance for further understanding of various reservoir characteristics and reservoir prediction under the influence of different provenance systems.