High-resolution astrochronological record for the Paleocene-Oligocene (66–23 Ma) from the rapidly subsiding Bohai Bay Basin, northeastern China

Abstract

The Paleogene succession of the Bohai Bay Basin (BBB), a highly productive petroleum basin in northeastern China with predominantly lacustrine fill, is poorly dated at present. Here, we generated an internal astronomical time scale (ATS) for the Paleogene strata of the Bohai Bay Basin (Dongying Depression, Jiyang Subbasin) using multitaper method (MTM) spectral analysis of high-resolution gamma ray logs. This ATS, which extends from 66 to 23Ma, is anchored to the standard geologic time scale by calibration to the Paleogene/Neogene boundary (23.03Ma) at the top of Dongying Formation. Based on this ATS, we recalibrated the ages of biozones, rifting episodes, and paleoclimate stages within the BBB. The recalibrated ages of rifting episodes and related fluctuations in sedimentation rates exhibit a close relationship to secular variation in production rates of Pacific oceanic plateaus and spreading rates of the Southeast Indian Ridge, confirming that the subsidence history of the BBB was significantly influenced by subduction of the Pacific Plate along the eastern margin of Asia and by collision of the Indian and Eurasian plates. Age recalibration also facilitated re-evaluation of the relationship of sedimentation in the Bohai Bay Basin to the Paleogene climate history of East Asia, e.g., confirming a cooling and drying trend throughout the Eocene.