New Research Reveals Phased Formation of Northwest China's Ancient Oil and Gas Resources
Northwest China contains significant oil and gas resources within rocks formed approximately 300 million years ago, during the Carboniferous and Permian periods. For decades, the precise ages of these rocks and their interrelationships across different basins have remained uncertain. This challenge stemmed primarily from a complex transition from marine to land environments and a scarcity of datable fossils.
A research team led by Nanjing University has addressed this challenge by analyzing volcanic ash layers preserved within the sedimentary rocks, utilizing zircon crystals as geological clocks.
"The precise ages of these rocks and their interrelationships across different basins have remained uncertain for decades, primarily due to a complex transition from marine to land environments and a scarcity of datable fossils."
Unveiling Ancient Ages Through Volcanic Ash
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 adjacent Turpan–Hami, Santanghu, and Yili basins. The study's findings, published in Science China Earth Sciences, indicate a significant revelation.
"The region's major oil-source rocks did not form simultaneously, but rather developed during three distinct periods."
A New Timeline of Oil Source Rock Formation
This detailed analysis established a clear, phased timeline for the development of oil-source rocks:
- Late Carboniferous to Early Permian: In the Mahu Sag of the Junggar Basin, source rocks formed earliest.
- Early Permian: Farther south, in the southern Junggar Basin and the Turpan–Hami and Santanghu basins, source rocks primarily accumulated during this period.
- Middle to Late Permian: The youngest source rocks were located in the Yili Basin and eastern Junggar Basin, forming later.
Geological Evidence for Ocean Closure
This new timeline demonstrates that the transition from marine to land-based environments progressed across the region over millions of years, becoming progressively younger from northwest to east. Researchers state this pattern provides crucial geological evidence supporting a gradual, scissor-like closure of the Paleo-Asian Ocean.
"This pattern provides geological evidence supporting a gradual, scissor-like closure of the Paleo-Asian Ocean."
Enhancing Energy Exploration
In addition to its scientific implications for understanding Earth's history, the study offers practical benefits 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. Precise dating of these rocks enables geologists to create more accurate basin models and enhance predictions for oil and gas resource locations.
The researchers emphasize that combining high-precision dating with extensive sampling is crucial for interpreting complex geological regions. This comprehensive approach contributes significantly to the understanding of Central Asian tectonic evolution and provides vital support for future energy exploration efforts.