High Resolution ID‐TIMS Redefines the Distribution and Age of the Main Mesozoic Lacustrine Hydrocarbon Source Rocks in the Ordos Basin, China.

Using high‐precision zircon U‐Pb ID‐TIMS geochronology, tuffs from the Chang 9 shale and the Chang 7 shale were dated. The tuff in the Chang 9 shale is 241.47 ± 0.17 Ma, which falls between the top tuff age of 241.06 ± 0.12 Ma and the bottom tuff age of 241.558 ± 0.093 Ma in the Chang 7 shale. These reveal that the Chang 9 and Chang 7 shales are contemporaneous, belonging to the Ladinian stage of the Middle Triassic. This insight expands the region of the main source rock of Chang 7 to the northeast and will inform the search for the deep Chang 9 shale petroleum system, increasing the scope for exploring the Chang 7 shale system in northern Shaanxi. The research results clarify the relationship between the two sets of shale in the Yanchang Formation and redefine the distribution range of the Chang 7 shale in the Ordos Basin. At the same time, it shows that there is a cross‐layer problem in the stratigraphic division of the Yanchang Formation in different regions, the high‐precision U‐Pb dating technology providing a reference for the fine stratigraphic correlation of other continental basins in the world. [ABSTRACT FROM AUTHOR]