Buried Jurassic rift system in the middle segment of the northern Qaidam Basin: Implications for Mesozoic landforms of the northern Tibetan Plateau

Abstract

ABSTRACT The Jurassic is one of the most important periods generating hydrocarbon source rocks and coals in Northwest China, and the Qaidam Basin is an important petroliferous and coal-forming basin. However, a series of explorations in the Qaidam Basin targeting Jurassic source rocks have failed over the past several years. These failures were mainly caused by missing the targeted Jurassic strata, suggesting that the current understanding of the Jurassic distribution in the Qaidam Basin is still limited. Therefore, this study conducts detailed analyses of the drilling wells and seismic data in the middle segment of the northern Qaidam Basin. The seismic profiles and borehole data indicate a rifting tectonic setting with discontinuous deposition and rapid facies transition during the Jurassic. A well-preserved buried rift valley proved in the Hongnan region reveals that the Jurassic deposits are mainly restricted in the narrow rift system. Therefore, further exploration targeting the Jurassic source rocks should focus on delineating the distribution of the Jurassic rift system in the Qaidam Basin, combined with the recovery of the complex Cenozoic tectonic overprinting.