Northwest China contains some of the country’s most important oil and gas resources, many of which are hosted in rocks formed between the Carboniferous and Permian periods, around 300 million years ago. Despite their economic importance, the exact ages of these rocks—and how they relate to one another across different basins—have remained uncertain for decades. This is mainly because the rocks record a complicated transition from ancient seas to land environments and contain few fossils that can be used for precise dating.
In a new study published in Science China Earth Sciences, an international team of researchers led by Nanjing University tackled this problem by turning to volcanic ash layers preserved within the sedimentary rocks. These ash layers contain zircon crystals that act like tiny geological clocks. By analyzing these crystals using multiple high-precision dating techniques, the team obtained 53 zircon U–Pb ages from outcrops and drill cores across the Junggar Basin and the neighboring Turpan–Hami, Santanghu, and Yili basins.
The results reveal that the region’s major oil-source rocks did not all form at the same time. Instead, they developed during three separate and well-defined periods. In the Mahu Sag of the Junggar Basin, source rocks formed from the late Carboniferous to the very beginning of the Permian. Farther south, in the southern Junggar Basin and the Turpan–Hami and Santanghu basins, source rocks mainly accumulated during the early Permian. The youngest source rocks, found in the Yili Basin and eastern Junggar Basin, formed later still, during the middle to late Permian.
This new timeline shows that the shift from marine to land-based environments swept across the region over millions of years, becoming progressively younger from northwest to east. According to the researchers, this pattern provides fresh geological evidence that the Paleo-Asian Ocean closed gradually, like a pair of scissors, rather than disappearing everywhere at once.
Beyond its significance for understanding Earth’s history, the study has practical implications for energy exploration. Key source-rock units in the Junggar region—such as the Fengcheng, Lucaogou, and Pingdiquan formations—are central to major shale oil systems in northwest China. Knowing precisely when these rocks formed allows geologists to build more accurate basin models and better predict where oil and gas resources may be found.
The researchers stress that combining high-precision dating with large-scale sampling is essential for decoding complex geological regions. Their work not only sheds new light on the tectonic evolution of Central Asia during the Late Paleozoic, but also provides a stronger scientific foundation for future energy exploration in northwest China.
See the article:
Hou Z, Wang X, Zhi D, Tang Y, Wu Q, Zhang H, Cao J, Xiao D, Fu G, Zheng M, Qi X, Cai Y, Feng Z, Zhang B, Zhou C, Li Y, Ye X, Huang X, Zhang S, Shen B, Ramezani J, Zhang S, Shen S. 2026. High-resolution chronostratigraphic framework and spatiotemporal evolution of Carboniferous-Permian source rocks in the Junggar Basin and its periphery. Science China Earth Sciences, 69(1): 288–312, https://doi.org/10.1007/s11430-025-1748-3
Science China Earth Sciences