Mesozoic–Cenozoic denudation and thermal history in the Central Uplift of the South Yellow Sea basin and the implications for hydrocarbon systems: Constraints from the CSDP-2 borehole

Abstract

Abstract This study focuses on the Mesozoic–Cenozoic tectono-thermal events in the Central Uplift of the South Yellow Sea Basin (SYSB) based on the CSDP-2 borehole. CSDP-2 is the first borehole to penetrate the integrated Paleozoic–Mesozoic sedimentary strata and recovered approximately 2736 m of core. The drilling results confirm a significant stratigraphic hiatus, i.e., Indosinian unconformity, between the Neogene–Quaternary and the underlying Lower Triassic. The eroded thickness estimated from sonic log and vitrinite reflectance data range from ∼1200 to 1400 m. Multiple paleo-thermometer data from the CSDP-2 cores, including vitrinite reflectance, apatite/zircon fission-track (AFT/ZFT) and fluid inclusions, were used to reconstruct the Mesozoic–Cenozoic thermal history in the study area. There was a continuous heating process during the early Mesozoic. The peak paleo-temperature may have reached up to 160 °C (base Permian) during the Late Jurassic, with the highest paleo-geothermal gradient of approximately 58.8 °C·km−1. The tectono-thermal evolution was dominated by the Mesozoic intracontinental collision between the Yangtze Craton and the Sino-Korean platform. The heating process was mainly caused by rapid burial on the passive continental margin and igneous activities. The paleo-temperature significantly decreased following the Late Jurassic. Two rapid cooling processes ca. 100–65 Ma and ca. 35 Ma are suggested by the AFT modeling results. Cooling history indicates that the tectonic uplift and denudation likely occurred from the Early Cretaceous to the Miocene. The reconstruction results of thermal evolution confirm that the Mesozoic–Paleozoic source rocks are mature or even highly mature, and hydrocarbon generation, migration and charge undoubtedly occurred in the Central Uplift, showing substantial hydrocarbon potential. Moreover, the reconstruction of the tectono-thermal history provides important constraints for regional tectonic studies.